98 files changed, 38637 insertions, 0 deletions
diff --git a/docshell/base/BaseHistory.cpp b/docshell/base/BaseHistory.cpp
new file mode 100644
index 0000000000..3932711b5b
--- /dev/null
+++ b/docshell/base/BaseHistory.cpp
@@ -0,0 +1,247 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BaseHistory.h"
+#include "nsThreadUtils.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Link.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/StaticPrefs_layout.h"
+
+namespace mozilla {
+
+using mozilla::dom::ContentParent;
+using mozilla::dom::Link;
+
+BaseHistory::BaseHistory() : mTrackedURIs(kTrackedUrisInitialSize) {}
+
+BaseHistory::~BaseHistory() = default;
+
+static constexpr nsLiteralCString kDisallowedSchemes[] = {
+    "about"_ns,         "blob"_ns,           "cached-favicon"_ns,
+    "chrome"_ns,        "data"_ns,           "imap"_ns,
+    "javascript"_ns,    "mailbox"_ns,        "news"_ns,
+    "page-icon"_ns,     "resource"_ns,       "view-source"_ns,
+    "moz-extension"_ns, "moz-page-thumb"_ns,
+};
+
+bool BaseHistory::CanStore(nsIURI* aURI) {
+  nsAutoCString scheme;
+  if (NS_WARN_IF(NS_FAILED(aURI->GetScheme(scheme)))) {
+    return false;
+  }
+
+  if (!scheme.EqualsLiteral("http") && !scheme.EqualsLiteral("https")) {
+    for (const nsLiteralCString& disallowed : kDisallowedSchemes) {
+      if (scheme.Equals(disallowed)) {
+        return false;
+      }
+    }
+  }
+
+  nsAutoCString spec;
+  aURI->GetSpec(spec);
+  return spec.Length() <= StaticPrefs::browser_history_maxUrlLength();
+}
+
+void BaseHistory::ScheduleVisitedQuery(nsIURI* aURI,
+                                       dom::ContentParent* aForProcess) {
+  mPendingQueries.WithEntryHandle(aURI, [&](auto&& entry) {
+    auto& set = entry.OrInsertWith([] { return ContentParentSet(); });
+    if (aForProcess) {
+      set.Insert(aForProcess);
+    }
+  });
+  if (mStartPendingVisitedQueriesScheduled) {
+    return;
+  }
+  mStartPendingVisitedQueriesScheduled =
+      NS_SUCCEEDED(NS_DispatchToMainThreadQueue(
+          NS_NewRunnableFunction(
+              "BaseHistory::StartPendingVisitedQueries",
+              [self = RefPtr<BaseHistory>(this)] {
+                self->mStartPendingVisitedQueriesScheduled = false;
+                auto queries = std::move(self->mPendingQueries);
+                self->StartPendingVisitedQueries(std::move(queries));
+                MOZ_DIAGNOSTIC_ASSERT(self->mPendingQueries.IsEmpty());
+              }),
+          EventQueuePriority::Idle));
+}
+
+void BaseHistory::CancelVisitedQueryIfPossible(nsIURI* aURI) {
+  mPendingQueries.Remove(aURI);
+  // TODO(bug 1591393): It could be worth to make this virtual and allow places
+  // to stop the existing database query? Needs some measurement.
+}
+
+void BaseHistory::RegisterVisitedCallback(nsIURI* aURI, Link* aLink) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aURI, "Must pass a non-null URI!");
+  MOZ_ASSERT(aLink, "Must pass a non-null Link!");
+
+  if (!CanStore(aURI)) {
+    aLink->VisitedQueryFinished(/* visited = */ false);
+    return;
+  }
+
+  // Obtain our array of observers for this URI.
+  auto* const links =
+      mTrackedURIs.WithEntryHandle(aURI, [&](auto&& entry) -> ObservingLinks* {
+        MOZ_DIAGNOSTIC_ASSERT(!entry || !entry->mLinks.IsEmpty(),
+                              "An empty key was kept around in our hashtable!");
+        if (!entry) {
+          ScheduleVisitedQuery(aURI, nullptr);
+        }
+
+        return &entry.OrInsertWith([] { return ObservingLinks{}; });
+      });
+
+  if (!links) {
+    return;
+  }
+
+  // Sanity check that Links are not registered more than once for a given URI.
+  // This will not catch a case where it is registered for two different URIs.
+  MOZ_DIAGNOSTIC_ASSERT(!links->mLinks.Contains(aLink),
+                        "Already tracking this Link object!");
+
+  links->mLinks.AppendElement(aLink);
+
+  // If this link has already been queried and we should notify, do so now.
+  switch (links->mStatus) {
+    case VisitedStatus::Unknown:
+      break;
+    case VisitedStatus::Unvisited:
+      [[fallthrough]];
+    case VisitedStatus::Visited:
+      aLink->VisitedQueryFinished(links->mStatus == VisitedStatus::Visited);
+      break;
+  }
+}
+
+void BaseHistory::UnregisterVisitedCallback(nsIURI* aURI, Link* aLink) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aURI, "Must pass a non-null URI!");
+  MOZ_ASSERT(aLink, "Must pass a non-null Link object!");
+
+  // Get the array, and remove the item from it.
+  auto entry = mTrackedURIs.Lookup(aURI);
+  if (!entry) {
+    MOZ_ASSERT(!CanStore(aURI),
+               "Trying to unregister URI that wasn't registered, "
+               "and that could be visited!");
+    return;
+  }
+
+  ObserverArray& observers = entry->mLinks;
+  if (!observers.RemoveElement(aLink)) {
+    MOZ_ASSERT_UNREACHABLE("Trying to unregister node that wasn't registered!");
+    return;
+  }
+
+  // If the array is now empty, we should remove it from the hashtable.
+  if (observers.IsEmpty()) {
+    entry.Remove();
+    CancelVisitedQueryIfPossible(aURI);
+  }
+}
+
+void BaseHistory::NotifyVisited(
+    nsIURI* aURI, VisitedStatus aStatus,
+    const ContentParentSet* aListOfProcessesToNotify) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aStatus != VisitedStatus::Unknown);
+
+  NotifyVisitedInThisProcess(aURI, aStatus);
+  if (XRE_IsParentProcess()) {
+    NotifyVisitedFromParent(aURI, aStatus, aListOfProcessesToNotify);
+  }
+}
+
+void BaseHistory::NotifyVisitedInThisProcess(nsIURI* aURI,
+                                             VisitedStatus aStatus) {
+  if (NS_WARN_IF(!aURI)) {
+    return;
+  }
+
+  auto entry = mTrackedURIs.Lookup(aURI);
+  if (!entry) {
+    // If we have no observers for this URI, we have nothing to notify about.
+    return;
+  }
+
+  ObservingLinks& links = entry.Data();
+  links.mStatus = aStatus;
+
+  // If we have a key, it should have at least one observer.
+  MOZ_ASSERT(!links.mLinks.IsEmpty());
+
+  // Dispatch an event to each document which has a Link observing this URL.
+  // These will fire asynchronously in the correct DocGroup.
+
+  const bool visited = aStatus == VisitedStatus::Visited;
+  for (Link* link : links.mLinks.BackwardRange()) {
+    link->VisitedQueryFinished(visited);
+  }
+}
+
+void BaseHistory::SendPendingVisitedResultsToChildProcesses() {
+  MOZ_ASSERT(!mPendingResults.IsEmpty());
+
+  mStartPendingResultsScheduled = false;
+
+  auto results = std::move(mPendingResults);
+  MOZ_ASSERT(mPendingResults.IsEmpty());
+
+  nsTArray<ContentParent*> cplist;
+  nsTArray<dom::VisitedQueryResult> resultsForProcess;
+  ContentParent::GetAll(cplist);
+  for (ContentParent* cp : cplist) {
+    resultsForProcess.ClearAndRetainStorage();
+    for (auto& result : results) {
+      if (result.mProcessesToNotify.IsEmpty() ||
+          result.mProcessesToNotify.Contains(cp)) {
+        resultsForProcess.AppendElement(result.mResult);
+      }
+    }
+    if (!resultsForProcess.IsEmpty()) {
+      Unused << NS_WARN_IF(!cp->SendNotifyVisited(resultsForProcess));
+    }
+  }
+}
+
+void BaseHistory::NotifyVisitedFromParent(
+    nsIURI* aURI, VisitedStatus aStatus,
+    const ContentParentSet* aListOfProcessesToNotify) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (aListOfProcessesToNotify && aListOfProcessesToNotify->IsEmpty()) {
+    return;
+  }
+
+  auto& result = *mPendingResults.AppendElement();
+  result.mResult.visited() = aStatus == VisitedStatus::Visited;
+  result.mResult.uri() = aURI;
+  if (aListOfProcessesToNotify) {
+    for (auto* entry : *aListOfProcessesToNotify) {
+      result.mProcessesToNotify.Insert(entry);
+    }
+  }
+
+  if (mStartPendingResultsScheduled) {
+    return;
+  }
+
+  mStartPendingResultsScheduled = NS_SUCCEEDED(NS_DispatchToMainThreadQueue(
+      NewRunnableMethod(
+          "BaseHistory::SendPendingVisitedResultsToChildProcesses", this,
+          &BaseHistory::SendPendingVisitedResultsToChildProcesses),
+      EventQueuePriority::Idle));
+}
+
+}  // namespace mozilla
diff --git a/docshell/base/BaseHistory.h b/docshell/base/BaseHistory.h
new file mode 100644
index 0000000000..f0fa36db99
--- /dev/null
+++ b/docshell/base/BaseHistory.h
@@ -0,0 +1,85 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_BaseHistory_h
+#define mozilla_BaseHistory_h
+
+#include "IHistory.h"
+#include "mozilla/dom/ContentParent.h"
+#include "nsTHashSet.h"
+
+/* A base class for history implementations that implement link coloring. */
+
+namespace mozilla {
+
+class BaseHistory : public IHistory {
+ public:
+  void RegisterVisitedCallback(nsIURI*, dom::Link*) final;
+  void ScheduleVisitedQuery(nsIURI*, dom::ContentParent*) final;
+  void UnregisterVisitedCallback(nsIURI*, dom::Link*) final;
+  void NotifyVisited(nsIURI*, VisitedStatus,
+                     const ContentParentSet* = nullptr) final;
+
+  // Some URIs like data-uris are never going to be stored in history, so we can
+  // avoid doing IPC roundtrips for them or what not.
+  static bool CanStore(nsIURI*);
+
+ protected:
+  void NotifyVisitedInThisProcess(nsIURI*, VisitedStatus);
+  void NotifyVisitedFromParent(nsIURI*, VisitedStatus, const ContentParentSet*);
+  static constexpr const size_t kTrackedUrisInitialSize = 64;
+
+  BaseHistory();
+  ~BaseHistory();
+
+  using ObserverArray = nsTObserverArray<dom::Link*>;
+  struct ObservingLinks {
+    ObserverArray mLinks;
+    VisitedStatus mStatus = VisitedStatus::Unknown;
+
+    size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+      return mLinks.ShallowSizeOfExcludingThis(aMallocSizeOf);
+    }
+  };
+
+  using PendingVisitedQueries = nsTHashMap<nsURIHashKey, ContentParentSet>;
+  struct PendingVisitedResult {
+    dom::VisitedQueryResult mResult;
+    ContentParentSet mProcessesToNotify;
+  };
+  using PendingVisitedResults = nsTArray<PendingVisitedResult>;
+
+  // Starts all the queries in the pending queries list, potentially at the same
+  // time.
+  virtual void StartPendingVisitedQueries(PendingVisitedQueries&&) = 0;
+
+ private:
+  // Cancels a visited query, if it is at all possible, because we know we won't
+  // use the results anymore.
+  void CancelVisitedQueryIfPossible(nsIURI*);
+
+  void SendPendingVisitedResultsToChildProcesses();
+
+ protected:
+  // A map from URI to links that depend on that URI, and whether that URI is
+  // known-to-be-visited-or-unvisited already.
+  nsTHashMap<nsURIHashKey, ObservingLinks> mTrackedURIs;
+
+ private:
+  // The set of pending URIs that we haven't queried yet but need to.
+  PendingVisitedQueries mPendingQueries;
+  // The set of pending query results that we still haven't dispatched to child
+  // processes.
+  PendingVisitedResults mPendingResults;
+  // Whether we've successfully scheduled a runnable to call
+  // StartPendingVisitedQueries already.
+  bool mStartPendingVisitedQueriesScheduled = false;
+  // Whether we've successfully scheduled a runnable to call
+  // SendPendingVisitedResultsToChildProcesses already.
+  bool mStartPendingResultsScheduled = false;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/docshell/base/BrowsingContext.cpp b/docshell/base/BrowsingContext.cpp
new file mode 100644
index 0000000000..141036a86c
--- /dev/null
+++ b/docshell/base/BrowsingContext.cpp
@@ -0,0 +1,3905 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/BrowsingContext.h"
+
+#include "ipc/IPCMessageUtils.h"
+
+#ifdef ACCESSIBILITY
+#  include "mozilla/a11y/DocAccessibleParent.h"
+#  include "mozilla/a11y/Platform.h"
+#  include "nsAccessibilityService.h"
+#  if defined(XP_WIN)
+#    include "mozilla/a11y/AccessibleWrap.h"
+#    include "mozilla/a11y/Compatibility.h"
+#    include "mozilla/a11y/nsWinUtils.h"
+#  endif
+#endif
+#include "mozilla/AppShutdown.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/BrowserHost.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/BrowserParent.h"
+#include "mozilla/dom/BrowsingContextGroup.h"
+#include "mozilla/dom/BrowsingContextBinding.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLEmbedElement.h"
+#include "mozilla/dom/HTMLIFrameElement.h"
+#include "mozilla/dom/Location.h"
+#include "mozilla/dom/LocationBinding.h"
+#include "mozilla/dom/MediaDevices.h"
+#include "mozilla/dom/PopupBlocker.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/SessionStoreChild.h"
+#include "mozilla/dom/SessionStorageManager.h"
+#include "mozilla/dom/StructuredCloneTags.h"
+#include "mozilla/dom/UserActivationIPCUtils.h"
+#include "mozilla/dom/WindowBinding.h"
+#include "mozilla/dom/WindowContext.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "mozilla/dom/SyncedContextInlines.h"
+#include "mozilla/dom/XULFrameElement.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/net/DocumentLoadListener.h"
+#include "mozilla/net/RequestContextService.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/AsyncEventDispatcher.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Components.h"
+#include "mozilla/HashTable.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MediaFeatureChange.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPrefs_fission.h"
+#include "mozilla/StaticPrefs_media.h"
+#include "mozilla/StaticPrefs_page_load.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/URLQueryStringStripper.h"
+#include "mozilla/EventStateManager.h"
+#include "nsIURIFixup.h"
+#include "nsIXULRuntime.h"
+
+#include "nsDocShell.h"
+#include "nsDocShellLoadState.h"
+#include "nsFocusManager.h"
+#include "nsGlobalWindowInner.h"
+#include "nsGlobalWindowOuter.h"
+#include "PresShell.h"
+#include "nsIObserverService.h"
+#include "nsISHistory.h"
+#include "nsContentUtils.h"
+#include "nsQueryObject.h"
+#include "nsSandboxFlags.h"
+#include "nsScriptError.h"
+#include "nsThreadUtils.h"
+#include "xpcprivate.h"
+
+#include "AutoplayPolicy.h"
+#include "GVAutoplayRequestStatusIPC.h"
+
+extern mozilla::LazyLogModule gAutoplayPermissionLog;
+extern mozilla::LazyLogModule gTimeoutDeferralLog;
+
+#define AUTOPLAY_LOG(msg, ...) \
+  MOZ_LOG(gAutoplayPermissionLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
+namespace IPC {
+// Allow serialization and deserialization of OrientationType over IPC
+template <>
+struct ParamTraits<mozilla::dom::OrientationType>
+    : public ContiguousEnumSerializer<
+          mozilla::dom::OrientationType,
+          mozilla::dom::OrientationType::Portrait_primary,
+          mozilla::dom::OrientationType::EndGuard_> {};
+
+template <>
+struct ParamTraits<mozilla::dom::DisplayMode>
+    : public ContiguousEnumSerializer<mozilla::dom::DisplayMode,
+                                      mozilla::dom::DisplayMode::Browser,
+                                      mozilla::dom::DisplayMode::EndGuard_> {};
+
+template <>
+struct ParamTraits<mozilla::dom::PrefersColorSchemeOverride>
+    : public ContiguousEnumSerializer<
+          mozilla::dom::PrefersColorSchemeOverride,
+          mozilla::dom::PrefersColorSchemeOverride::None,
+          mozilla::dom::PrefersColorSchemeOverride::EndGuard_> {};
+
+template <>
+struct ParamTraits<mozilla::dom::ExplicitActiveStatus>
+    : public ContiguousEnumSerializer<
+          mozilla::dom::ExplicitActiveStatus,
+          mozilla::dom::ExplicitActiveStatus::None,
+          mozilla::dom::ExplicitActiveStatus::EndGuard_> {};
+
+// Allow serialization and deserialization of TouchEventsOverride over IPC
+template <>
+struct ParamTraits<mozilla::dom::TouchEventsOverride>
+    : public ContiguousEnumSerializer<
+          mozilla::dom::TouchEventsOverride,
+          mozilla::dom::TouchEventsOverride::Disabled,
+          mozilla::dom::TouchEventsOverride::EndGuard_> {};
+
+template <>
+struct ParamTraits<mozilla::dom::EmbedderColorSchemes> {
+  using paramType = mozilla::dom::EmbedderColorSchemes;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mUsed);
+    WriteParam(aWriter, aParam.mPreferred);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->mUsed) &&
+           ReadParam(aReader, &aResult->mPreferred);
+  }
+};
+
+}  // namespace IPC
+
+namespace mozilla {
+namespace dom {
+
+// Explicit specialization of the `Transaction` type. Required by the `extern
+// template class` declaration in the header.
+template class syncedcontext::Transaction<BrowsingContext>;
+
+extern mozilla::LazyLogModule gUserInteractionPRLog;
+
+#define USER_ACTIVATION_LOG(msg, ...) \
+  MOZ_LOG(gUserInteractionPRLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
+static LazyLogModule gBrowsingContextLog("BrowsingContext");
+static LazyLogModule gBrowsingContextSyncLog("BrowsingContextSync");
+
+typedef nsTHashMap<nsUint64HashKey, BrowsingContext*> BrowsingContextMap;
+
+// All BrowsingContexts indexed by Id
+static StaticAutoPtr<BrowsingContextMap> sBrowsingContexts;
+// Top-level Content BrowsingContexts only, indexed by BrowserId instead of Id
+static StaticAutoPtr<BrowsingContextMap> sCurrentTopByBrowserId;
+
+static void UnregisterBrowserId(BrowsingContext* aBrowsingContext) {
+  if (!aBrowsingContext->IsTopContent() || !sCurrentTopByBrowserId) {
+    return;
+  }
+
+  // Avoids an extra lookup
+  auto browserIdEntry =
+      sCurrentTopByBrowserId->Lookup(aBrowsingContext->BrowserId());
+  if (browserIdEntry && browserIdEntry.Data() == aBrowsingContext) {
+    browserIdEntry.Remove();
+  }
+}
+
+static void Register(BrowsingContext* aBrowsingContext) {
+  sBrowsingContexts->InsertOrUpdate(aBrowsingContext->Id(), aBrowsingContext);
+  if (aBrowsingContext->IsTopContent()) {
+    sCurrentTopByBrowserId->InsertOrUpdate(aBrowsingContext->BrowserId(),
+                                           aBrowsingContext);
+  }
+
+  aBrowsingContext->Group()->Register(aBrowsingContext);
+}
+
+// static
+void BrowsingContext::UpdateCurrentTopByBrowserId(
+    BrowsingContext* aNewBrowsingContext) {
+  if (aNewBrowsingContext->IsTopContent()) {
+    sCurrentTopByBrowserId->InsertOrUpdate(aNewBrowsingContext->BrowserId(),
+                                           aNewBrowsingContext);
+  }
+}
+
+BrowsingContext* BrowsingContext::GetParent() const {
+  return mParentWindow ? mParentWindow->GetBrowsingContext() : nullptr;
+}
+
+bool BrowsingContext::IsInSubtreeOf(BrowsingContext* aContext) {
+  BrowsingContext* bc = this;
+  do {
+    if (bc == aContext) {
+      return true;
+    }
+  } while ((bc = bc->GetParent()));
+  return false;
+}
+
+BrowsingContext* BrowsingContext::Top() {
+  BrowsingContext* bc = this;
+  while (bc->mParentWindow) {
+    bc = bc->GetParent();
+  }
+  return bc;
+}
+
+const BrowsingContext* BrowsingContext::Top() const {
+  const BrowsingContext* bc = this;
+  while (bc->mParentWindow) {
+    bc = bc->GetParent();
+  }
+  return bc;
+}
+
+int32_t BrowsingContext::IndexOf(BrowsingContext* aChild) {
+  int32_t index = -1;
+  for (BrowsingContext* child : Children()) {
+    ++index;
+    if (child == aChild) {
+      break;
+    }
+  }
+  return index;
+}
+
+WindowContext* BrowsingContext::GetTopWindowContext() const {
+  if (mParentWindow) {
+    return mParentWindow->TopWindowContext();
+  }
+  return mCurrentWindowContext;
+}
+
+/* static */
+void BrowsingContext::Init() {
+  if (!sBrowsingContexts) {
+    sBrowsingContexts = new BrowsingContextMap();
+    sCurrentTopByBrowserId = new BrowsingContextMap();
+    ClearOnShutdown(&sBrowsingContexts);
+    ClearOnShutdown(&sCurrentTopByBrowserId);
+  }
+}
+
+/* static */
+LogModule* BrowsingContext::GetLog() { return gBrowsingContextLog; }
+
+/* static */
+LogModule* BrowsingContext::GetSyncLog() { return gBrowsingContextSyncLog; }
+
+/* static */
+already_AddRefed<BrowsingContext> BrowsingContext::Get(uint64_t aId) {
+  return do_AddRef(sBrowsingContexts->Get(aId));
+}
+
+/* static */
+already_AddRefed<BrowsingContext> BrowsingContext::GetCurrentTopByBrowserId(
+    uint64_t aBrowserId) {
+  return do_AddRef(sCurrentTopByBrowserId->Get(aBrowserId));
+}
+
+/* static */
+already_AddRefed<BrowsingContext> BrowsingContext::GetFromWindow(
+    WindowProxyHolder& aProxy) {
+  return do_AddRef(aProxy.get());
+}
+
+CanonicalBrowsingContext* BrowsingContext::Canonical() {
+  return CanonicalBrowsingContext::Cast(this);
+}
+
+bool BrowsingContext::IsOwnedByProcess() const {
+  return mIsInProcess && mDocShell &&
+         !nsDocShell::Cast(mDocShell)->WillChangeProcess();
+}
+
+bool BrowsingContext::SameOriginWithTop() {
+  MOZ_ASSERT(IsInProcess());
+  // If the top BrowsingContext is not same-process to us, it is cross-origin
+  if (!Top()->IsInProcess()) {
+    return false;
+  }
+
+  nsIDocShell* docShell = GetDocShell();
+  if (!docShell) {
+    return false;
+  }
+  Document* doc = docShell->GetDocument();
+  if (!doc) {
+    return false;
+  }
+  nsIPrincipal* principal = doc->NodePrincipal();
+
+  nsIDocShell* topDocShell = Top()->GetDocShell();
+  if (!topDocShell) {
+    return false;
+  }
+  Document* topDoc = topDocShell->GetDocument();
+  if (!topDoc) {
+    return false;
+  }
+  nsIPrincipal* topPrincipal = topDoc->NodePrincipal();
+
+  return principal->Equals(topPrincipal);
+}
+
+/* static */
+already_AddRefed<BrowsingContext> BrowsingContext::CreateDetached(
+    nsGlobalWindowInner* aParent, BrowsingContext* aOpener,
+    BrowsingContextGroup* aSpecificGroup, const nsAString& aName, Type aType,
+    bool aIsPopupRequested, bool aCreatedDynamically) {
+  if (aParent) {
+    MOZ_DIAGNOSTIC_ASSERT(aParent->GetWindowContext());
+    MOZ_DIAGNOSTIC_ASSERT(aParent->GetBrowsingContext()->mType == aType);
+    MOZ_DIAGNOSTIC_ASSERT(aParent->GetBrowsingContext()->GetBrowserId() != 0);
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(aType != Type::Chrome || XRE_IsParentProcess());
+
+  uint64_t id = nsContentUtils::GenerateBrowsingContextId();
+
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("Creating 0x%08" PRIx64 " in %s", id,
+           XRE_IsParentProcess() ? "Parent" : "Child"));
+
+  RefPtr<BrowsingContext> parentBC =
+      aParent ? aParent->GetBrowsingContext() : nullptr;
+  RefPtr<WindowContext> parentWC =
+      aParent ? aParent->GetWindowContext() : nullptr;
+  BrowsingContext* inherit = parentBC ? parentBC.get() : aOpener;
+
+  // Determine which BrowsingContextGroup this context should be created in.
+  RefPtr<BrowsingContextGroup> group = aSpecificGroup;
+  if (aType == Type::Chrome) {
+    MOZ_DIAGNOSTIC_ASSERT(!group);
+    group = BrowsingContextGroup::GetChromeGroup();
+  } else if (!group) {
+    group = BrowsingContextGroup::Select(parentWC, aOpener);
+  }
+
+  // Configure initial values for synced fields.
+  FieldValues fields;
+  fields.Get<IDX_Name>() = aName;
+
+  if (aOpener) {
+    MOZ_DIAGNOSTIC_ASSERT(!aParent,
+                          "new BC with both initial opener and parent");
+    MOZ_DIAGNOSTIC_ASSERT(aOpener->Group() == group);
+    MOZ_DIAGNOSTIC_ASSERT(aOpener->mType == aType);
+    fields.Get<IDX_OpenerId>() = aOpener->Id();
+    fields.Get<IDX_HadOriginalOpener>() = true;
+
+    if (aType == Type::Chrome && !aParent) {
+      // See SetOpener for why we do this inheritance.
+      fields.Get<IDX_PrefersColorSchemeOverride>() =
+          aOpener->Top()->GetPrefersColorSchemeOverride();
+    }
+  }
+
+  if (aParent) {
+    MOZ_DIAGNOSTIC_ASSERT(parentBC->Group() == group);
+    MOZ_DIAGNOSTIC_ASSERT(parentBC->mType == aType);
+    fields.Get<IDX_EmbedderInnerWindowId>() = aParent->WindowID();
+    // Non-toplevel content documents are always embededed within content.
+    fields.Get<IDX_EmbeddedInContentDocument>() =
+        parentBC->mType == Type::Content;
+
+    // XXX(farre): Can/Should we check aParent->IsLoading() here? (Bug
+    // 1608448) Check if the parent was itself loading already
+    auto readystate = aParent->GetDocument()->GetReadyStateEnum();
+    fields.Get<IDX_AncestorLoading>() =
+        parentBC->GetAncestorLoading() ||
+        readystate == Document::ReadyState::READYSTATE_LOADING ||
+        readystate == Document::ReadyState::READYSTATE_INTERACTIVE;
+  }
+
+  fields.Get<IDX_BrowserId>() =
+      parentBC ? parentBC->GetBrowserId() : nsContentUtils::GenerateBrowserId();
+
+  fields.Get<IDX_OpenerPolicy>() = nsILoadInfo::OPENER_POLICY_UNSAFE_NONE;
+  if (aOpener && aOpener->SameOriginWithTop()) {
+    // We inherit the opener policy if there is a creator and if the creator's
+    // origin is same origin with the creator's top-level origin.
+    // If it is cross origin we should not inherit the CrossOriginOpenerPolicy
+    fields.Get<IDX_OpenerPolicy>() = aOpener->Top()->GetOpenerPolicy();
+
+    // If we inherit a policy which is potentially cross-origin isolated, we
+    // must be in a potentially cross-origin isolated BCG.
+    bool isPotentiallyCrossOriginIsolated =
+        fields.Get<IDX_OpenerPolicy>() ==
+        nsILoadInfo::OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP;
+    MOZ_RELEASE_ASSERT(isPotentiallyCrossOriginIsolated ==
+                       group->IsPotentiallyCrossOriginIsolated());
+  } else if (aOpener) {
+    // They are not same origin
+    auto topPolicy = aOpener->Top()->GetOpenerPolicy();
+    MOZ_RELEASE_ASSERT(topPolicy == nsILoadInfo::OPENER_POLICY_UNSAFE_NONE ||
+                       topPolicy ==
+                           nsILoadInfo::OPENER_POLICY_SAME_ORIGIN_ALLOW_POPUPS);
+  } else if (!aParent && group->IsPotentiallyCrossOriginIsolated()) {
+    // If we're creating a brand-new toplevel BC in a potentially cross-origin
+    // isolated group, it should start out with a strict opener policy.
+    fields.Get<IDX_OpenerPolicy>() =
+        nsILoadInfo::OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP;
+  }
+
+  fields.Get<IDX_HistoryID>() = nsID::GenerateUUID();
+  fields.Get<IDX_ExplicitActive>() = [&] {
+    if (parentBC || aType == Type::Content) {
+      // Non-root browsing-contexts inherit their status from its parent.
+      // Top-content either gets managed by the top chrome, or gets manually
+      // managed by the front-end (see ManuallyManagesActiveness). In any case
+      // we want to start off as inactive.
+      return ExplicitActiveStatus::None;
+    }
+    // Chrome starts as active.
+    return ExplicitActiveStatus::Active;
+  }();
+
+  fields.Get<IDX_FullZoom>() = parentBC ? parentBC->FullZoom() : 1.0f;
+  fields.Get<IDX_TextZoom>() = parentBC ? parentBC->TextZoom() : 1.0f;
+
+  bool allowContentRetargeting =
+      inherit ? inherit->GetAllowContentRetargetingOnChildren() : true;
+  fields.Get<IDX_AllowContentRetargeting>() = allowContentRetargeting;
+  fields.Get<IDX_AllowContentRetargetingOnChildren>() = allowContentRetargeting;
+
+  // Assume top allows fullscreen for its children unless otherwise stated.
+  // Subframes start with it false unless otherwise noted in SetEmbedderElement.
+  fields.Get<IDX_FullscreenAllowedByOwner>() = !aParent;
+
+  fields.Get<IDX_DefaultLoadFlags>() =
+      inherit ? inherit->GetDefaultLoadFlags() : nsIRequest::LOAD_NORMAL;
+
+  fields.Get<IDX_OrientationLock>() = mozilla::hal::ScreenOrientation::None;
+
+  fields.Get<IDX_UseGlobalHistory>() =
+      inherit ? inherit->GetUseGlobalHistory() : false;
+
+  fields.Get<IDX_UseErrorPages>() = true;
+
+  fields.Get<IDX_TouchEventsOverrideInternal>() = TouchEventsOverride::None;
+
+  fields.Get<IDX_AllowJavascript>() =
+      inherit ? inherit->GetAllowJavascript() : true;
+
+  fields.Get<IDX_IsPopupRequested>() = aIsPopupRequested;
+
+  if (!parentBC) {
+    fields.Get<IDX_ShouldDelayMediaFromStart>() =
+        StaticPrefs::media_block_autoplay_until_in_foreground();
+  }
+
+  RefPtr<BrowsingContext> context;
+  if (XRE_IsParentProcess()) {
+    context = new CanonicalBrowsingContext(parentWC, group, id,
+                                           /* aOwnerProcessId */ 0,
+                                           /* aEmbedderProcessId */ 0, aType,
+                                           std::move(fields));
+  } else {
+    context =
+        new BrowsingContext(parentWC, group, id, aType, std::move(fields));
+  }
+
+  context->mEmbeddedByThisProcess = XRE_IsParentProcess() || aParent;
+  context->mCreatedDynamically = aCreatedDynamically;
+  if (inherit) {
+    context->mPrivateBrowsingId = inherit->mPrivateBrowsingId;
+    context->mUseRemoteTabs = inherit->mUseRemoteTabs;
+    context->mUseRemoteSubframes = inherit->mUseRemoteSubframes;
+    context->mOriginAttributes = inherit->mOriginAttributes;
+  }
+
+  nsCOMPtr<nsIRequestContextService> rcsvc =
+      net::RequestContextService::GetOrCreate();
+  if (rcsvc) {
+    nsCOMPtr<nsIRequestContext> requestContext;
+    nsresult rv = rcsvc->NewRequestContext(getter_AddRefs(requestContext));
+    if (NS_SUCCEEDED(rv) && requestContext) {
+      context->mRequestContextId = requestContext->GetID();
+    }
+  }
+
+  return context.forget();
+}
+
+already_AddRefed<BrowsingContext> BrowsingContext::CreateIndependent(
+    Type aType) {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess(),
+                        "BCs created in the content process must be related to "
+                        "some BrowserChild");
+  RefPtr<BrowsingContext> bc(
+      CreateDetached(nullptr, nullptr, nullptr, u""_ns, aType, false));
+  bc->mWindowless = bc->IsContent();
+  bc->mEmbeddedByThisProcess = true;
+  bc->EnsureAttached();
+  return bc.forget();
+}
+
+void BrowsingContext::EnsureAttached() {
+  if (!mEverAttached) {
+    Register(this);
+
+    // Attach the browsing context to the tree.
+    Attach(/* aFromIPC */ false, /* aOriginProcess */ nullptr);
+  }
+}
+
+/* static */
+mozilla::ipc::IPCResult BrowsingContext::CreateFromIPC(
+    BrowsingContext::IPCInitializer&& aInit, BrowsingContextGroup* aGroup,
+    ContentParent* aOriginProcess) {
+  MOZ_DIAGNOSTIC_ASSERT(aOriginProcess || XRE_IsContentProcess());
+  MOZ_DIAGNOSTIC_ASSERT(aGroup);
+
+  uint64_t originId = 0;
+  if (aOriginProcess) {
+    originId = aOriginProcess->ChildID();
+    aGroup->EnsureHostProcess(aOriginProcess);
+  }
+
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("Creating 0x%08" PRIx64 " from IPC (origin=0x%08" PRIx64 ")",
+           aInit.mId, originId));
+
+  RefPtr<WindowContext> parent = aInit.GetParent();
+
+  RefPtr<BrowsingContext> context;
+  if (XRE_IsParentProcess()) {
+    // If the new BrowsingContext has a parent, it is a sub-frame embedded in
+    // whatever process sent the message. If it doesn't, and is not windowless,
+    // it is a new window or tab, and will be embedded in the parent process.
+    uint64_t embedderProcessId = (aInit.mWindowless || parent) ? originId : 0;
+    context = new CanonicalBrowsingContext(parent, aGroup, aInit.mId, originId,
+                                           embedderProcessId, Type::Content,
+                                           std::move(aInit.mFields));
+  } else {
+    context = new BrowsingContext(parent, aGroup, aInit.mId, Type::Content,
+                                  std::move(aInit.mFields));
+  }
+
+  context->mWindowless = aInit.mWindowless;
+  context->mCreatedDynamically = aInit.mCreatedDynamically;
+  context->mChildOffset = aInit.mChildOffset;
+  if (context->GetHasSessionHistory()) {
+    context->CreateChildSHistory();
+    if (mozilla::SessionHistoryInParent()) {
+      context->GetChildSessionHistory()->SetIndexAndLength(
+          aInit.mSessionHistoryIndex, aInit.mSessionHistoryCount, nsID());
+    }
+  }
+
+  // NOTE: Call through the `Set` methods for these values to ensure that any
+  // relevant process-local state is also updated.
+  context->SetOriginAttributes(aInit.mOriginAttributes);
+  context->SetRemoteTabs(aInit.mUseRemoteTabs);
+  context->SetRemoteSubframes(aInit.mUseRemoteSubframes);
+  context->mRequestContextId = aInit.mRequestContextId;
+  // NOTE: Private browsing ID is set by `SetOriginAttributes`.
+
+  Register(context);
+
+  return context->Attach(/* aFromIPC */ true, aOriginProcess);
+}
+
+BrowsingContext::BrowsingContext(WindowContext* aParentWindow,
+                                 BrowsingContextGroup* aGroup,
+                                 uint64_t aBrowsingContextId, Type aType,
+                                 FieldValues&& aInit)
+    : mFields(std::move(aInit)),
+      mType(aType),
+      mBrowsingContextId(aBrowsingContextId),
+      mGroup(aGroup),
+      mParentWindow(aParentWindow),
+      mPrivateBrowsingId(0),
+      mEverAttached(false),
+      mIsInProcess(false),
+      mIsDiscarded(false),
+      mWindowless(false),
+      mDanglingRemoteOuterProxies(false),
+      mEmbeddedByThisProcess(false),
+      mUseRemoteTabs(false),
+      mUseRemoteSubframes(false),
+      mCreatedDynamically(false),
+      mIsInBFCache(false),
+      mCanExecuteScripts(true),
+      mChildOffset(0) {
+  MOZ_RELEASE_ASSERT(!mParentWindow || mParentWindow->Group() == mGroup);
+  MOZ_RELEASE_ASSERT(mBrowsingContextId != 0);
+  MOZ_RELEASE_ASSERT(mGroup);
+}
+
+void BrowsingContext::SetDocShell(nsIDocShell* aDocShell) {
+  // XXX(nika): We should communicate that we are now an active BrowsingContext
+  // process to the parent & do other validation here.
+  MOZ_DIAGNOSTIC_ASSERT(mEverAttached);
+  MOZ_RELEASE_ASSERT(aDocShell->GetBrowsingContext() == this);
+  mDocShell = aDocShell;
+  mDanglingRemoteOuterProxies = !mIsInProcess;
+  mIsInProcess = true;
+  if (mChildSessionHistory) {
+    mChildSessionHistory->SetIsInProcess(true);
+  }
+
+  RecomputeCanExecuteScripts();
+  ClearCachedValuesOfLocations();
+}
+
+// This class implements a callback that will return the remote window proxy for
+// mBrowsingContext in that compartment, if it has one. It also removes the
+// proxy from the map, because the object will be transplanted into another kind
+// of object.
+class MOZ_STACK_CLASS CompartmentRemoteProxyTransplantCallback
+    : public js::CompartmentTransplantCallback {
+ public:
+  explicit CompartmentRemoteProxyTransplantCallback(
+      BrowsingContext* aBrowsingContext)
+      : mBrowsingContext(aBrowsingContext) {}
+
+  virtual JSObject* getObjectToTransplant(
+      JS::Compartment* compartment) override {
+    auto* priv = xpc::CompartmentPrivate::Get(compartment);
+    if (!priv) {
+      return nullptr;
+    }
+
+    auto& map = priv->GetRemoteProxyMap();
+    auto result = map.lookup(mBrowsingContext);
+    if (!result) {
+      return nullptr;
+    }
+    JSObject* resultObject = result->value();
+    map.remove(result);
+
+    return resultObject;
+  }
+
+ private:
+  BrowsingContext* mBrowsingContext;
+};
+
+void BrowsingContext::CleanUpDanglingRemoteOuterWindowProxies(
+    JSContext* aCx, JS::MutableHandle<JSObject*> aOuter) {
+  if (!mDanglingRemoteOuterProxies) {
+    return;
+  }
+  mDanglingRemoteOuterProxies = false;
+
+  CompartmentRemoteProxyTransplantCallback cb(this);
+  js::RemapRemoteWindowProxies(aCx, &cb, aOuter);
+}
+
+bool BrowsingContext::IsActive() const {
+  const BrowsingContext* current = this;
+  do {
+    auto explicit_ = current->GetExplicitActive();
+    if (explicit_ != ExplicitActiveStatus::None) {
+      return explicit_ == ExplicitActiveStatus::Active;
+    }
+    if (mParentWindow && !mParentWindow->IsCurrent()) {
+      return false;
+    }
+  } while ((current = current->GetParent()));
+
+  return false;
+}
+
+bool BrowsingContext::GetIsActiveBrowserWindow() {
+  if (!XRE_IsParentProcess()) {
+    return Top()->GetIsActiveBrowserWindowInternal();
+  }
+
+  // chrome:// urls loaded in the parent won't receive
+  // their own activation so we defer to the top chrome
+  // Browsing Context when in the parent process.
+  return Canonical()
+      ->TopCrossChromeBoundary()
+      ->GetIsActiveBrowserWindowInternal();
+}
+
+void BrowsingContext::SetIsActiveBrowserWindow(bool aActive) {
+  Unused << SetIsActiveBrowserWindowInternal(aActive);
+}
+
+bool BrowsingContext::FullscreenAllowed() const {
+  for (auto* current = this; current; current = current->GetParent()) {
+    if (!current->GetFullscreenAllowedByOwner()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static bool OwnerAllowsFullscreen(const Element& aEmbedder) {
+  if (aEmbedder.IsXULElement()) {
+    return !aEmbedder.HasAttr(nsGkAtoms::disablefullscreen);
+  }
+  if (aEmbedder.IsHTMLElement(nsGkAtoms::iframe)) {
+    // This is controlled by feature policy.
+    return true;
+  }
+  if (const auto* embed = HTMLEmbedElement::FromNode(aEmbedder)) {
+    return embed->AllowFullscreen();
+  }
+  return false;
+}
+
+void BrowsingContext::SetEmbedderElement(Element* aEmbedder) {
+  mEmbeddedByThisProcess = true;
+
+  // Update embedder-element-specific fields in a shared transaction.
+  // Don't do this when clearing our embedder, as we're being destroyed either
+  // way.
+  if (aEmbedder) {
+    Transaction txn;
+    txn.SetEmbedderElementType(Some(aEmbedder->LocalName()));
+    txn.SetEmbeddedInContentDocument(
+        aEmbedder->OwnerDoc()->IsContentDocument());
+    if (nsCOMPtr<nsPIDOMWindowInner> inner =
+            do_QueryInterface(aEmbedder->GetOwnerGlobal())) {
+      txn.SetEmbedderInnerWindowId(inner->WindowID());
+    }
+    txn.SetFullscreenAllowedByOwner(OwnerAllowsFullscreen(*aEmbedder));
+    if (XRE_IsParentProcess() && aEmbedder->IsXULElement() && IsTopContent()) {
+      nsAutoString messageManagerGroup;
+      aEmbedder->GetAttr(nsGkAtoms::messagemanagergroup, messageManagerGroup);
+      txn.SetMessageManagerGroup(messageManagerGroup);
+      txn.SetUseGlobalHistory(
+          !aEmbedder->HasAttr(nsGkAtoms::disableglobalhistory));
+      if (!aEmbedder->HasAttr(nsGkAtoms::manualactiveness)) {
+        // We're active iff the parent cross-chrome-boundary is active. Note we
+        // can't just use this->Canonical()->GetParentCrossChromeBoundary here,
+        // since mEmbedderElement is still null at this point.
+        RefPtr bc = aEmbedder->OwnerDoc()->GetBrowsingContext();
+        const bool isActive = bc && bc->IsActive();
+        txn.SetExplicitActive(isActive ? ExplicitActiveStatus::Active
+                                       : ExplicitActiveStatus::Inactive);
+        if (auto* bp = Canonical()->GetBrowserParent()) {
+          bp->SetRenderLayers(isActive);
+        }
+      }
+    }
+
+    MOZ_ALWAYS_SUCCEEDS(txn.Commit(this));
+  }
+
+  if (XRE_IsParentProcess() && IsTopContent()) {
+    Canonical()->MaybeSetPermanentKey(aEmbedder);
+  }
+
+  mEmbedderElement = aEmbedder;
+
+  if (mEmbedderElement) {
+    if (nsCOMPtr<nsIObserverService> obs = services::GetObserverService()) {
+      obs->NotifyWhenScriptSafe(ToSupports(this),
+                                "browsing-context-did-set-embedder", nullptr);
+    }
+
+    if (IsEmbedderTypeObjectOrEmbed()) {
+      Unused << SetSyntheticDocumentContainer(true);
+    }
+  }
+}
+
+bool BrowsingContext::IsEmbedderTypeObjectOrEmbed() {
+  if (const Maybe<nsString>& type = GetEmbedderElementType()) {
+    return nsGkAtoms::object->Equals(*type) || nsGkAtoms::embed->Equals(*type);
+  }
+  return false;
+}
+
+void BrowsingContext::Embed() {
+  if (auto* frame = HTMLIFrameElement::FromNode(mEmbedderElement)) {
+    frame->BindToBrowsingContext(this);
+  }
+}
+
+mozilla::ipc::IPCResult BrowsingContext::Attach(bool aFromIPC,
+                                                ContentParent* aOriginProcess) {
+  MOZ_DIAGNOSTIC_ASSERT(!mEverAttached);
+  MOZ_DIAGNOSTIC_ASSERT_IF(aFromIPC, aOriginProcess || XRE_IsContentProcess());
+  mEverAttached = true;
+
+  if (MOZ_LOG_TEST(GetLog(), LogLevel::Debug)) {
+    nsAutoCString suffix;
+    mOriginAttributes.CreateSuffix(suffix);
+    MOZ_LOG(GetLog(), LogLevel::Debug,
+            ("%s: Connecting 0x%08" PRIx64 " to 0x%08" PRIx64
+             " (private=%d, remote=%d, fission=%d, oa=%s)",
+             XRE_IsParentProcess() ? "Parent" : "Child", Id(),
+             GetParent() ? GetParent()->Id() : 0, (int)mPrivateBrowsingId,
+             (int)mUseRemoteTabs, (int)mUseRemoteSubframes, suffix.get()));
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(mGroup);
+  MOZ_DIAGNOSTIC_ASSERT(!mIsDiscarded);
+
+  if (mGroup->IsPotentiallyCrossOriginIsolated() !=
+      (Top()->GetOpenerPolicy() ==
+       nsILoadInfo::OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP)) {
+    MOZ_DIAGNOSTIC_ASSERT(aFromIPC);
+    if (aFromIPC) {
+      auto* actor = aOriginProcess
+                        ? static_cast<mozilla::ipc::IProtocol*>(aOriginProcess)
+                        : static_cast<mozilla::ipc::IProtocol*>(
+                              ContentChild::GetSingleton());
+      return IPC_FAIL(
+          actor,
+          "Invalid CrossOriginIsolated state in BrowsingContext::Attach call");
+    } else {
+      MOZ_CRASH(
+          "Invalid CrossOriginIsolated state in BrowsingContext::Attach call");
+    }
+  }
+
+  AssertCoherentLoadContext();
+
+  // Add ourselves either to our parent or BrowsingContextGroup's child list.
+  // Important: We shouldn't return IPC_FAIL after this point, since the
+  // BrowsingContext will have already been added to the tree.
+  if (mParentWindow) {
+    if (!aFromIPC) {
+      MOZ_DIAGNOSTIC_ASSERT(!mParentWindow->IsDiscarded(),
+                            "local attach in discarded window");
+      MOZ_DIAGNOSTIC_ASSERT(!GetParent()->IsDiscarded(),
+                            "local attach call in discarded bc");
+      MOZ_DIAGNOSTIC_ASSERT(mParentWindow->GetWindowGlobalChild(),
+                            "local attach call with oop parent window");
+      MOZ_DIAGNOSTIC_ASSERT(mParentWindow->GetWindowGlobalChild()->CanSend(),
+                            "local attach call with dead parent window");
+    }
+    mChildOffset =
+        mCreatedDynamically ? -1 : mParentWindow->Children().Length();
+    mParentWindow->AppendChildBrowsingContext(this);
+    RecomputeCanExecuteScripts();
+  } else {
+    mGroup->Toplevels().AppendElement(this);
+  }
+
+  if (GetIsPopupSpam()) {
+    PopupBlocker::RegisterOpenPopupSpam();
+  }
+
+  if (IsTop() && GetHasSessionHistory() && !mChildSessionHistory) {
+    CreateChildSHistory();
+  }
+
+  // Why the context is being attached. This will always be "attach" in the
+  // content process, but may be "replace" if it's known the context being
+  // replaced in the parent process.
+  const char16_t* why = u"attach";
+
+  if (XRE_IsContentProcess() && !aFromIPC) {
+    // Send attach to our parent if we need to.
+    ContentChild::GetSingleton()->SendCreateBrowsingContext(
+        mGroup->Id(), GetIPCInitializer());
+  } else if (XRE_IsParentProcess()) {
+    // If this window was created as a subframe by a content process, it must be
+    // being hosted within the same BrowserParent as its mParentWindow.
+    // Toplevel BrowsingContexts created by content have their BrowserParent
+    // configured during `RecvConstructPopupBrowser`.
+    if (mParentWindow && aOriginProcess) {
+      MOZ_DIAGNOSTIC_ASSERT(
+          mParentWindow->Canonical()->GetContentParent() == aOriginProcess,
+          "Creator process isn't the same as our embedder?");
+      Canonical()->SetCurrentBrowserParent(
+          mParentWindow->Canonical()->GetBrowserParent());
+    }
+
+    mGroup->EachOtherParent(aOriginProcess, [&](ContentParent* aParent) {
+      MOZ_DIAGNOSTIC_ASSERT(IsContent(),
+                            "chrome BCG cannot be synced to content process");
+      if (!Canonical()->IsEmbeddedInProcess(aParent->ChildID())) {
+        Unused << aParent->SendCreateBrowsingContext(mGroup->Id(),
+                                                     GetIPCInitializer());
+      }
+    });
+
+    if (IsTop() && IsContent() && Canonical()->GetWebProgress()) {
+      why = u"replace";
+    }
+
+    // We want to create a BrowsingContextWebProgress for all content
+    // BrowsingContexts.
+    if (IsContent() && !Canonical()->mWebProgress) {
+      Canonical()->mWebProgress = new BrowsingContextWebProgress(Canonical());
+    }
+  }
+
+  if (nsCOMPtr<nsIObserverService> obs = services::GetObserverService()) {
+    obs->NotifyWhenScriptSafe(ToSupports(this), "browsing-context-attached",
+                              why);
+  }
+
+  if (XRE_IsParentProcess()) {
+    Canonical()->CanonicalAttach();
+  }
+  return IPC_OK();
+}
+
+void BrowsingContext::Detach(bool aFromIPC) {
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("%s: Detaching 0x%08" PRIx64 " from 0x%08" PRIx64,
+           XRE_IsParentProcess() ? "Parent" : "Child", Id(),
+           GetParent() ? GetParent()->Id() : 0));
+
+  MOZ_DIAGNOSTIC_ASSERT(mEverAttached);
+  MOZ_DIAGNOSTIC_ASSERT(!mIsDiscarded);
+
+  if (XRE_IsParentProcess()) {
+    Canonical()->AddPendingDiscard();
+  }
+  auto callListeners =
+      MakeScopeExit([&, listeners = std::move(mDiscardListeners), id = Id()] {
+        for (const auto& listener : listeners) {
+          listener(id);
+        }
+        if (XRE_IsParentProcess()) {
+          Canonical()->RemovePendingDiscard();
+        }
+      });
+
+  nsCOMPtr<nsIRequestContextService> rcsvc =
+      net::RequestContextService::GetOrCreate();
+  if (rcsvc) {
+    rcsvc->RemoveRequestContext(GetRequestContextId());
+  }
+
+  // This will only ever be null if the cycle-collector has unlinked us. Don't
+  // try to detach ourselves in that case.
+  if (NS_WARN_IF(!mGroup)) {
+    MOZ_ASSERT_UNREACHABLE();
+    return;
+  }
+
+  if (mParentWindow) {
+    mParentWindow->RemoveChildBrowsingContext(this);
+  } else {
+    mGroup->Toplevels().RemoveElement(this);
+  }
+
+  if (XRE_IsParentProcess()) {
+    RefPtr<CanonicalBrowsingContext> self{Canonical()};
+    Group()->EachParent([&](ContentParent* aParent) {
+      // Only the embedder process is allowed to initiate a BrowsingContext
+      // detach, so if we've gotten here, the host process already knows we've
+      // been detached, and there's no need to tell it again.
+      //
+      // If the owner process is not the same as the embedder process, its
+      // BrowsingContext will be detached when its nsWebBrowser instance is
+      // destroyed.
+      bool doDiscard = !Canonical()->IsEmbeddedInProcess(aParent->ChildID()) &&
+                       !Canonical()->IsOwnedByProcess(aParent->ChildID());
+
+      // Hold a strong reference to ourself, and keep our BrowsingContextGroup
+      // alive, until the responses comes back to ensure we don't die while
+      // messages relating to this context are in-flight.
+      //
+      // When the callback is called, the keepalive on our group will be
+      // destroyed, and the reference to the BrowsingContext will be dropped,
+      // which may cause it to be fully destroyed.
+      mGroup->AddKeepAlive();
+      self->AddPendingDiscard();
+      auto callback = [self](auto) {
+        self->mGroup->RemoveKeepAlive();
+        self->RemovePendingDiscard();
+      };
+
+      aParent->SendDiscardBrowsingContext(this, doDiscard, callback, callback);
+    });
+  } else {
+    // Hold a strong reference to ourself until the responses come back to
+    // ensure the BrowsingContext isn't cleaned up before the parent process
+    // acknowledges the discard request.
+    auto callback = [self = RefPtr{this}](auto) {};
+    ContentChild::GetSingleton()->SendDiscardBrowsingContext(
+        this, !aFromIPC, callback, callback);
+  }
+
+  mGroup->Unregister(this);
+  UnregisterBrowserId(this);
+  mIsDiscarded = true;
+
+  if (XRE_IsParentProcess()) {
+    nsFocusManager* fm = nsFocusManager::GetFocusManager();
+    if (fm) {
+      fm->BrowsingContextDetached(this);
+    }
+  }
+
+  if (nsCOMPtr<nsIObserverService> obs = services::GetObserverService()) {
+    // Why the context is being discarded. This will always be "discard" in the
+    // content process, but may be "replace" if it's known the context being
+    // replaced in the parent process.
+    const char16_t* why = u"discard";
+    if (XRE_IsParentProcess() && IsTop() && !Canonical()->GetWebProgress()) {
+      why = u"replace";
+    }
+    obs->NotifyObservers(ToSupports(this), "browsing-context-discarded", why);
+  }
+
+  // NOTE: Doesn't use SetClosed, as it will be set in all processes
+  // automatically by calls to Detach()
+  mFields.SetWithoutSyncing<IDX_Closed>(true);
+
+  if (GetIsPopupSpam()) {
+    PopupBlocker::UnregisterOpenPopupSpam();
+    // NOTE: Doesn't use SetIsPopupSpam, as it will be set all processes
+    // automatically.
+    mFields.SetWithoutSyncing<IDX_IsPopupSpam>(false);
+  }
+
+  AssertOriginAttributesMatchPrivateBrowsing();
+
+  if (XRE_IsParentProcess()) {
+    Canonical()->CanonicalDiscard();
+  }
+}
+
+void BrowsingContext::AddDiscardListener(
+    std::function<void(uint64_t)>&& aListener) {
+  if (mIsDiscarded) {
+    aListener(Id());
+    return;
+  }
+  mDiscardListeners.AppendElement(std::move(aListener));
+}
+
+void BrowsingContext::PrepareForProcessChange() {
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("%s: Preparing 0x%08" PRIx64 " for a process change",
+           XRE_IsParentProcess() ? "Parent" : "Child", Id()));
+
+  MOZ_ASSERT(mIsInProcess, "Must currently be an in-process frame");
+  MOZ_ASSERT(!mIsDiscarded, "We're already closed?");
+
+  mIsInProcess = false;
+  mUserGestureStart = TimeStamp();
+
+  ClearCachedValuesOfLocations();
+
+  // NOTE: For now, clear our nsDocShell reference, as we're primarily in a
+  // different process now. This may need to change in the future with
+  // Cross-Process BFCache.
+  mDocShell = nullptr;
+  if (mChildSessionHistory) {
+    // This can be removed once session history is stored exclusively in the
+    // parent process.
+    mChildSessionHistory->SetIsInProcess(false);
+  }
+
+  if (!mWindowProxy) {
+    return;
+  }
+
+  // We have to go through mWindowProxy rather than calling GetDOMWindow() on
+  // mDocShell because the mDocshell reference gets cleared immediately after
+  // the window is closed.
+  nsGlobalWindowOuter::PrepareForProcessChange(mWindowProxy);
+  MOZ_ASSERT(!mWindowProxy);
+}
+
+bool BrowsingContext::IsTargetable() const {
+  return !GetClosed() && AncestorsAreCurrent();
+}
+
+void BrowsingContext::SetOpener(BrowsingContext* aOpener) {
+  MOZ_DIAGNOSTIC_ASSERT(!aOpener || aOpener->Group() == Group());
+  MOZ_DIAGNOSTIC_ASSERT(!aOpener || aOpener->mType == mType);
+
+  MOZ_ALWAYS_SUCCEEDS(SetOpenerId(aOpener ? aOpener->Id() : 0));
+
+  if (IsChrome() && IsTop() && aOpener) {
+    // Inherit color scheme overrides from parent window. This is to inherit the
+    // color scheme of dark themed PBM windows in dialogs opened by such
+    // windows.
+    auto openerOverride = aOpener->Top()->PrefersColorSchemeOverride();
+    if (openerOverride != PrefersColorSchemeOverride()) {
+      MOZ_ALWAYS_SUCCEEDS(SetPrefersColorSchemeOverride(openerOverride));
+    }
+  }
+}
+
+bool BrowsingContext::HasOpener() const {
+  return sBrowsingContexts->Contains(GetOpenerId());
+}
+
+bool BrowsingContext::AncestorsAreCurrent() const {
+  const BrowsingContext* bc = this;
+  while (true) {
+    if (bc->IsDiscarded()) {
+      return false;
+    }
+
+    if (WindowContext* wc = bc->GetParentWindowContext()) {
+      if (!wc->IsCurrent() || wc->IsDiscarded()) {
+        return false;
+      }
+
+      bc = wc->GetBrowsingContext();
+    } else {
+      return true;
+    }
+  }
+}
+
+bool BrowsingContext::IsInBFCache() const {
+  if (mozilla::SessionHistoryInParent()) {
+    return mIsInBFCache;
+  }
+  return mParentWindow &&
+         mParentWindow->TopWindowContext()->GetWindowStateSaved();
+}
+
+Span<RefPtr<BrowsingContext>> BrowsingContext::Children() const {
+  if (WindowContext* current = mCurrentWindowContext) {
+    return current->Children();
+  }
+  return Span<RefPtr<BrowsingContext>>();
+}
+
+void BrowsingContext::GetChildren(
+    nsTArray<RefPtr<BrowsingContext>>& aChildren) {
+  aChildren.AppendElements(Children());
+}
+
+Span<RefPtr<BrowsingContext>> BrowsingContext::NonSyntheticChildren() const {
+  if (WindowContext* current = mCurrentWindowContext) {
+    return current->NonSyntheticChildren();
+  }
+  return Span<RefPtr<BrowsingContext>>();
+}
+
+void BrowsingContext::GetWindowContexts(
+    nsTArray<RefPtr<WindowContext>>& aWindows) {
+  aWindows.AppendElements(mWindowContexts);
+}
+
+void BrowsingContext::RegisterWindowContext(WindowContext* aWindow) {
+  MOZ_ASSERT(!mWindowContexts.Contains(aWindow),
+             "WindowContext already registered!");
+  MOZ_ASSERT(aWindow->GetBrowsingContext() == this);
+
+  mWindowContexts.AppendElement(aWindow);
+
+  // If the newly registered WindowContext is for our current inner window ID,
+  // re-run the `DidSet` handler to re-establish the relationship.
+  if (aWindow->InnerWindowId() == GetCurrentInnerWindowId()) {
+    DidSet(FieldIndex<IDX_CurrentInnerWindowId>());
+    MOZ_DIAGNOSTIC_ASSERT(mCurrentWindowContext == aWindow);
+  }
+}
+
+void BrowsingContext::UnregisterWindowContext(WindowContext* aWindow) {
+  MOZ_ASSERT(mWindowContexts.Contains(aWindow),
+             "WindowContext not registered!");
+  mWindowContexts.RemoveElement(aWindow);
+
+  // If our currently active window was unregistered, clear our reference to it.
+  if (aWindow == mCurrentWindowContext) {
+    // Re-read our `CurrentInnerWindowId` value and use it to set
+    // `mCurrentWindowContext`. As `aWindow` is now unregistered and discarded,
+    // we won't find it, and the value will be cleared back to `nullptr`.
+    DidSet(FieldIndex<IDX_CurrentInnerWindowId>());
+    MOZ_DIAGNOSTIC_ASSERT(mCurrentWindowContext == nullptr);
+  }
+}
+
+void BrowsingContext::PreOrderWalkVoid(
+    const std::function<void(BrowsingContext*)>& aCallback) {
+  aCallback(this);
+
+  AutoTArray<RefPtr<BrowsingContext>, 8> children;
+  children.AppendElements(Children());
+
+  for (auto& child : children) {
+    child->PreOrderWalkVoid(aCallback);
+  }
+}
+
+BrowsingContext::WalkFlag BrowsingContext::PreOrderWalkFlag(
+    const std::function<WalkFlag(BrowsingContext*)>& aCallback) {
+  switch (aCallback(this)) {
+    case WalkFlag::Skip:
+      return WalkFlag::Next;
+    case WalkFlag::Stop:
+      return WalkFlag::Stop;
+    case WalkFlag::Next:
+    default:
+      break;
+  }
+
+  AutoTArray<RefPtr<BrowsingContext>, 8> children;
+  children.AppendElements(Children());
+
+  for (auto& child : children) {
+    switch (child->PreOrderWalkFlag(aCallback)) {
+      case WalkFlag::Stop:
+        return WalkFlag::Stop;
+      default:
+        break;
+    }
+  }
+
+  return WalkFlag::Next;
+}
+
+void BrowsingContext::PostOrderWalk(
+    const std::function<void(BrowsingContext*)>& aCallback) {
+  AutoTArray<RefPtr<BrowsingContext>, 8> children;
+  children.AppendElements(Children());
+
+  for (auto& child : children) {
+    child->PostOrderWalk(aCallback);
+  }
+
+  aCallback(this);
+}
+
+void BrowsingContext::GetAllBrowsingContextsInSubtree(
+    nsTArray<RefPtr<BrowsingContext>>& aBrowsingContexts) {
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    aBrowsingContexts.AppendElement(aContext);
+  });
+}
+
+BrowsingContext* BrowsingContext::FindChildWithName(
+    const nsAString& aName, WindowGlobalChild& aRequestingWindow) {
+  if (aName.IsEmpty()) {
+    // You can't find a browsing context with the empty name.
+    return nullptr;
+  }
+
+  for (BrowsingContext* child : NonSyntheticChildren()) {
+    if (child->NameEquals(aName) && aRequestingWindow.CanNavigate(child) &&
+        child->IsTargetable()) {
+      return child;
+    }
+  }
+
+  return nullptr;
+}
+
+BrowsingContext* BrowsingContext::FindWithSpecialName(
+    const nsAString& aName, WindowGlobalChild& aRequestingWindow) {
+  // TODO(farre): Neither BrowsingContext nor nsDocShell checks if the
+  // browsing context pointed to by a special name is active. Should
+  // it be? See Bug 1527913.
+  if (aName.LowerCaseEqualsLiteral("_self")) {
+    return this;
+  }
+
+  if (aName.LowerCaseEqualsLiteral("_parent")) {
+    if (BrowsingContext* parent = GetParent()) {
+      return aRequestingWindow.CanNavigate(parent) ? parent : nullptr;
+    }
+    return this;
+  }
+
+  if (aName.LowerCaseEqualsLiteral("_top")) {
+    BrowsingContext* top = Top();
+
+    return aRequestingWindow.CanNavigate(top) ? top : nullptr;
+  }
+
+  return nullptr;
+}
+
+BrowsingContext* BrowsingContext::FindWithNameInSubtree(
+    const nsAString& aName, WindowGlobalChild* aRequestingWindow) {
+  MOZ_DIAGNOSTIC_ASSERT(!aName.IsEmpty());
+
+  if (NameEquals(aName) &&
+      (!aRequestingWindow || aRequestingWindow->CanNavigate(this)) &&
+      IsTargetable()) {
+    return this;
+  }
+
+  for (BrowsingContext* child : NonSyntheticChildren()) {
+    if (BrowsingContext* found =
+            child->FindWithNameInSubtree(aName, aRequestingWindow)) {
+      return found;
+    }
+  }
+
+  return nullptr;
+}
+
+bool BrowsingContext::IsSandboxedFrom(BrowsingContext* aTarget) {
+  // If no target then not sandboxed.
+  if (!aTarget) {
+    return false;
+  }
+
+  // We cannot be sandboxed from ourselves.
+  if (aTarget == this) {
+    return false;
+  }
+
+  // Default the sandbox flags to our flags, so that if we can't retrieve the
+  // active document, we will still enforce our own.
+  uint32_t sandboxFlags = GetSandboxFlags();
+  if (mDocShell) {
+    if (RefPtr<Document> doc = mDocShell->GetExtantDocument()) {
+      sandboxFlags = doc->GetSandboxFlags();
+    }
+  }
+
+  // If no flags, we are not sandboxed at all.
+  if (!sandboxFlags) {
+    return false;
+  }
+
+  // If aTarget has an ancestor, it is not top level.
+  if (RefPtr<BrowsingContext> ancestorOfTarget = aTarget->GetParent()) {
+    do {
+      // We are not sandboxed if we are an ancestor of target.
+      if (ancestorOfTarget == this) {
+        return false;
+      }
+      ancestorOfTarget = ancestorOfTarget->GetParent();
+    } while (ancestorOfTarget);
+
+    // Otherwise, we are sandboxed from aTarget.
+    return true;
+  }
+
+  // aTarget is top level, are we the "one permitted sandboxed
+  // navigator", i.e. did we open aTarget?
+  if (aTarget->GetOnePermittedSandboxedNavigatorId() == Id()) {
+    return false;
+  }
+
+  // If SANDBOXED_TOPLEVEL_NAVIGATION flag is not on, we are not sandboxed
+  // from our top.
+  if (!(sandboxFlags & SANDBOXED_TOPLEVEL_NAVIGATION) && aTarget == Top()) {
+    return false;
+  }
+
+  // If SANDBOXED_TOPLEVEL_NAVIGATION_USER_ACTIVATION flag is not on, we are not
+  // sandboxed from our top if we have user interaction. We assume there is a
+  // valid transient user gesture interaction if this check happens in the
+  // target process given that we have checked in the triggering process
+  // already.
+  if (!(sandboxFlags & SANDBOXED_TOPLEVEL_NAVIGATION_USER_ACTIVATION) &&
+      mCurrentWindowContext &&
+      (!mCurrentWindowContext->IsInProcess() ||
+       mCurrentWindowContext->HasValidTransientUserGestureActivation()) &&
+      aTarget == Top()) {
+    return false;
+  }
+
+  // Otherwise, we are sandboxed from aTarget.
+  return true;
+}
+
+RefPtr<SessionStorageManager> BrowsingContext::GetSessionStorageManager() {
+  RefPtr<SessionStorageManager>& manager = Top()->mSessionStorageManager;
+  if (!manager) {
+    manager = new SessionStorageManager(this);
+  }
+  return manager;
+}
+
+bool BrowsingContext::CrossOriginIsolated() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  return StaticPrefs::
+             dom_postMessage_sharedArrayBuffer_withCOOP_COEP_AtStartup() &&
+         Top()->GetOpenerPolicy() ==
+             nsILoadInfo::
+                 OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP &&
+         XRE_IsContentProcess() &&
+         StringBeginsWith(ContentChild::GetSingleton()->GetRemoteType(),
+                          WITH_COOP_COEP_REMOTE_TYPE_PREFIX);
+}
+
+void BrowsingContext::SetTriggeringAndInheritPrincipals(
+    nsIPrincipal* aTriggeringPrincipal, nsIPrincipal* aPrincipalToInherit,
+    uint64_t aLoadIdentifier) {
+  mTriggeringPrincipal = Some(
+      PrincipalWithLoadIdentifierTuple(aTriggeringPrincipal, aLoadIdentifier));
+  if (aPrincipalToInherit) {
+    mPrincipalToInherit = Some(
+        PrincipalWithLoadIdentifierTuple(aPrincipalToInherit, aLoadIdentifier));
+  }
+}
+
+std::tuple<nsCOMPtr<nsIPrincipal>, nsCOMPtr<nsIPrincipal>>
+BrowsingContext::GetTriggeringAndInheritPrincipalsForCurrentLoad() {
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal =
+      GetSavedPrincipal(mTriggeringPrincipal);
+  nsCOMPtr<nsIPrincipal> principalToInherit =
+      GetSavedPrincipal(mPrincipalToInherit);
+  return std::make_tuple(triggeringPrincipal, principalToInherit);
+}
+
+nsIPrincipal* BrowsingContext::GetSavedPrincipal(
+    Maybe<PrincipalWithLoadIdentifierTuple> aPrincipalTuple) {
+  if (aPrincipalTuple) {
+    nsCOMPtr<nsIPrincipal> principal;
+    uint64_t loadIdentifier;
+    std::tie(principal, loadIdentifier) = *aPrincipalTuple;
+    // We want to return a principal only if the load identifier for it
+    // matches the current one for this BC.
+    if (auto current = GetCurrentLoadIdentifier();
+        current && *current == loadIdentifier) {
+      return principal;
+    }
+  }
+  return nullptr;
+}
+
+BrowsingContext::~BrowsingContext() {
+  MOZ_DIAGNOSTIC_ASSERT(!mParentWindow ||
+                        !mParentWindow->mChildren.Contains(this));
+  MOZ_DIAGNOSTIC_ASSERT(!mGroup || !mGroup->Toplevels().Contains(this));
+
+  mDeprioritizedLoadRunner.clear();
+
+  if (sBrowsingContexts) {
+    sBrowsingContexts->Remove(Id());
+  }
+  UnregisterBrowserId(this);
+
+  ClearCachedValuesOfLocations();
+  mLocations.clear();
+}
+
+/* static */
+void BrowsingContext::DiscardFromContentParent(ContentParent* aCP) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (sBrowsingContexts) {
+    AutoTArray<RefPtr<BrowsingContext>, 8> toDiscard;
+    for (const auto& data : sBrowsingContexts->Values()) {
+      auto* bc = data->Canonical();
+      if (!bc->IsDiscarded() && bc->IsEmbeddedInProcess(aCP->ChildID())) {
+        toDiscard.AppendElement(bc);
+      }
+    }
+
+    for (BrowsingContext* bc : toDiscard) {
+      bc->Detach(/* aFromIPC */ true);
+    }
+  }
+}
+
+nsISupports* BrowsingContext::GetParentObject() const {
+  return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
+}
+
+JSObject* BrowsingContext::WrapObject(JSContext* aCx,
+                                      JS::Handle<JSObject*> aGivenProto) {
+  return BrowsingContext_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+bool BrowsingContext::WriteStructuredClone(JSContext* aCx,
+                                           JSStructuredCloneWriter* aWriter,
+                                           StructuredCloneHolder* aHolder) {
+  MOZ_DIAGNOSTIC_ASSERT(mEverAttached);
+  return (JS_WriteUint32Pair(aWriter, SCTAG_DOM_BROWSING_CONTEXT, 0) &&
+          JS_WriteUint32Pair(aWriter, uint32_t(Id()), uint32_t(Id() >> 32)));
+}
+
+/* static */
+JSObject* BrowsingContext::ReadStructuredClone(JSContext* aCx,
+                                               JSStructuredCloneReader* aReader,
+                                               StructuredCloneHolder* aHolder) {
+  uint32_t idLow = 0;
+  uint32_t idHigh = 0;
+  if (!JS_ReadUint32Pair(aReader, &idLow, &idHigh)) {
+    return nullptr;
+  }
+  uint64_t id = uint64_t(idHigh) << 32 | idLow;
+
+  // Note: Do this check after reading our ID data. Returning null will abort
+  // the decode operation anyway, but we should at least be as safe as possible.
+  if (NS_WARN_IF(!NS_IsMainThread())) {
+    MOZ_DIAGNOSTIC_ASSERT(false,
+                          "We shouldn't be trying to decode a BrowsingContext "
+                          "on a background thread.");
+    return nullptr;
+  }
+
+  JS::Rooted<JS::Value> val(aCx, JS::NullValue());
+  // We'll get rooting hazard errors from the RefPtr destructor if it isn't
+  // destroyed before we try to return a raw JSObject*, so create it in its own
+  // scope.
+  if (RefPtr<BrowsingContext> context = Get(id)) {
+    if (!GetOrCreateDOMReflector(aCx, context, &val) || !val.isObject()) {
+      return nullptr;
+    }
+  }
+  return val.toObjectOrNull();
+}
+
+bool BrowsingContext::CanSetOriginAttributes() {
+  // A discarded BrowsingContext has already been destroyed, and cannot modify
+  // its OriginAttributes.
+  if (NS_WARN_IF(IsDiscarded())) {
+    return false;
+  }
+
+  // Before attaching is the safest time to set OriginAttributes, and the only
+  // allowed time for content BrowsingContexts.
+  if (!EverAttached()) {
+    return true;
+  }
+
+  // Attached content BrowsingContexts may have been synced to other processes.
+  if (NS_WARN_IF(IsContent())) {
+    MOZ_CRASH();
+    return false;
+  }
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+
+  // Cannot set OriginAttributes after we've created our child BrowsingContext.
+  if (NS_WARN_IF(!Children().IsEmpty())) {
+    return false;
+  }
+
+  // Only allow setting OriginAttributes if we have no associated document, or
+  // the document is still `about:blank`.
+  // TODO: Bug 1273058 - should have no document when setting origin attributes.
+  if (WindowGlobalParent* window = Canonical()->GetCurrentWindowGlobal()) {
+    if (nsIURI* uri = window->GetDocumentURI()) {
+      MOZ_ASSERT(NS_IsAboutBlank(uri));
+      return NS_IsAboutBlank(uri);
+    }
+  }
+  return true;
+}
+
+Nullable<WindowProxyHolder> BrowsingContext::GetAssociatedWindow() {
+  // nsILoadContext usually only returns same-process windows,
+  // so we intentionally return nullptr if this BC is out of
+  // process.
+  if (IsInProcess()) {
+    return WindowProxyHolder(this);
+  }
+  return nullptr;
+}
+
+Nullable<WindowProxyHolder> BrowsingContext::GetTopWindow() {
+  return Top()->GetAssociatedWindow();
+}
+
+Element* BrowsingContext::GetTopFrameElement() {
+  return Top()->GetEmbedderElement();
+}
+
+void BrowsingContext::SetUsePrivateBrowsing(bool aUsePrivateBrowsing,
+                                            ErrorResult& aError) {
+  nsresult rv = SetUsePrivateBrowsing(aUsePrivateBrowsing);
+  if (NS_FAILED(rv)) {
+    aError.Throw(rv);
+  }
+}
+
+void BrowsingContext::SetUseTrackingProtectionWebIDL(
+    bool aUseTrackingProtection, ErrorResult& aRv) {
+  SetForceEnableTrackingProtection(aUseTrackingProtection, aRv);
+}
+
+void BrowsingContext::GetOriginAttributes(JSContext* aCx,
+                                          JS::MutableHandle<JS::Value> aVal,
+                                          ErrorResult& aError) {
+  AssertOriginAttributesMatchPrivateBrowsing();
+
+  if (!ToJSValue(aCx, mOriginAttributes, aVal)) {
+    aError.NoteJSContextException(aCx);
+  }
+}
+
+NS_IMETHODIMP BrowsingContext::GetAssociatedWindow(
+    mozIDOMWindowProxy** aAssociatedWindow) {
+  nsCOMPtr<mozIDOMWindowProxy> win = GetDOMWindow();
+  win.forget(aAssociatedWindow);
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::GetTopWindow(mozIDOMWindowProxy** aTopWindow) {
+  return Top()->GetAssociatedWindow(aTopWindow);
+}
+
+NS_IMETHODIMP BrowsingContext::GetTopFrameElement(Element** aTopFrameElement) {
+  RefPtr<Element> topFrameElement = GetTopFrameElement();
+  topFrameElement.forget(aTopFrameElement);
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::GetIsContent(bool* aIsContent) {
+  *aIsContent = IsContent();
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::GetUsePrivateBrowsing(
+    bool* aUsePrivateBrowsing) {
+  *aUsePrivateBrowsing = mPrivateBrowsingId > 0;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::SetUsePrivateBrowsing(bool aUsePrivateBrowsing) {
+  if (!CanSetOriginAttributes()) {
+    bool changed = aUsePrivateBrowsing != (mPrivateBrowsingId > 0);
+    if (changed) {
+      NS_WARNING("SetUsePrivateBrowsing when !CanSetOriginAttributes()");
+    }
+    return changed ? NS_ERROR_FAILURE : NS_OK;
+  }
+
+  return SetPrivateBrowsing(aUsePrivateBrowsing);
+}
+
+NS_IMETHODIMP BrowsingContext::SetPrivateBrowsing(bool aPrivateBrowsing) {
+  if (!CanSetOriginAttributes()) {
+    NS_WARNING("Attempt to set PrivateBrowsing when !CanSetOriginAttributes");
+    return NS_ERROR_FAILURE;
+  }
+
+  bool changed = aPrivateBrowsing != (mPrivateBrowsingId > 0);
+  if (changed) {
+    mPrivateBrowsingId = aPrivateBrowsing ? 1 : 0;
+    if (IsContent()) {
+      mOriginAttributes.SyncAttributesWithPrivateBrowsing(aPrivateBrowsing);
+    }
+
+    if (XRE_IsParentProcess()) {
+      Canonical()->AdjustPrivateBrowsingCount(aPrivateBrowsing);
+    }
+  }
+  AssertOriginAttributesMatchPrivateBrowsing();
+
+  if (changed && mDocShell) {
+    nsDocShell::Cast(mDocShell)->NotifyPrivateBrowsingChanged();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::GetUseRemoteTabs(bool* aUseRemoteTabs) {
+  *aUseRemoteTabs = mUseRemoteTabs;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::SetRemoteTabs(bool aUseRemoteTabs) {
+  if (!CanSetOriginAttributes()) {
+    NS_WARNING("Attempt to set RemoteTabs when !CanSetOriginAttributes");
+    return NS_ERROR_FAILURE;
+  }
+
+  static bool annotated = false;
+  if (aUseRemoteTabs && !annotated) {
+    annotated = true;
+    CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::DOMIPCEnabled,
+                                       true);
+  }
+
+  // Don't allow non-remote tabs with remote subframes.
+  if (NS_WARN_IF(!aUseRemoteTabs && mUseRemoteSubframes)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mUseRemoteTabs = aUseRemoteTabs;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::GetUseRemoteSubframes(
+    bool* aUseRemoteSubframes) {
+  *aUseRemoteSubframes = mUseRemoteSubframes;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::SetRemoteSubframes(bool aUseRemoteSubframes) {
+  if (!CanSetOriginAttributes()) {
+    NS_WARNING("Attempt to set RemoteSubframes when !CanSetOriginAttributes");
+    return NS_ERROR_FAILURE;
+  }
+
+  static bool annotated = false;
+  if (aUseRemoteSubframes && !annotated) {
+    annotated = true;
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::DOMFissionEnabled, true);
+  }
+
+  // Don't allow non-remote tabs with remote subframes.
+  if (NS_WARN_IF(aUseRemoteSubframes && !mUseRemoteTabs)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mUseRemoteSubframes = aUseRemoteSubframes;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::GetUseTrackingProtection(
+    bool* aUseTrackingProtection) {
+  *aUseTrackingProtection = false;
+
+  if (GetForceEnableTrackingProtection() ||
+      StaticPrefs::privacy_trackingprotection_enabled() ||
+      (UsePrivateBrowsing() &&
+       StaticPrefs::privacy_trackingprotection_pbmode_enabled())) {
+    *aUseTrackingProtection = true;
+    return NS_OK;
+  }
+
+  if (GetParent()) {
+    return GetParent()->GetUseTrackingProtection(aUseTrackingProtection);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContext::SetUseTrackingProtection(
+    bool aUseTrackingProtection) {
+  return SetForceEnableTrackingProtection(aUseTrackingProtection);
+}
+
+NS_IMETHODIMP BrowsingContext::GetScriptableOriginAttributes(
+    JSContext* aCx, JS::MutableHandle<JS::Value> aVal) {
+  AssertOriginAttributesMatchPrivateBrowsing();
+
+  bool ok = ToJSValue(aCx, mOriginAttributes, aVal);
+  NS_ENSURE_TRUE(ok, NS_ERROR_FAILURE);
+  return NS_OK;
+}
+
+NS_IMETHODIMP_(void)
+BrowsingContext::GetOriginAttributes(OriginAttributes& aAttrs) {
+  aAttrs = mOriginAttributes;
+  AssertOriginAttributesMatchPrivateBrowsing();
+}
+
+nsresult BrowsingContext::SetOriginAttributes(const OriginAttributes& aAttrs) {
+  if (!CanSetOriginAttributes()) {
+    NS_WARNING("Attempt to set OriginAttributes when !CanSetOriginAttributes");
+    return NS_ERROR_FAILURE;
+  }
+
+  AssertOriginAttributesMatchPrivateBrowsing();
+  mOriginAttributes = aAttrs;
+
+  bool isPrivate = mOriginAttributes.mPrivateBrowsingId !=
+                   nsIScriptSecurityManager::DEFAULT_PRIVATE_BROWSING_ID;
+  // Chrome Browsing Context can not contain OriginAttributes.mPrivateBrowsingId
+  if (IsChrome() && isPrivate) {
+    mOriginAttributes.mPrivateBrowsingId =
+        nsIScriptSecurityManager::DEFAULT_PRIVATE_BROWSING_ID;
+  }
+  SetPrivateBrowsing(isPrivate);
+  AssertOriginAttributesMatchPrivateBrowsing();
+
+  return NS_OK;
+}
+
+void BrowsingContext::AssertCoherentLoadContext() {
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  // LoadContext should generally match our opener or parent.
+  if (IsContent()) {
+    if (RefPtr<BrowsingContext> opener = GetOpener()) {
+      MOZ_DIAGNOSTIC_ASSERT(opener->mType == mType);
+      MOZ_DIAGNOSTIC_ASSERT(opener->mGroup == mGroup);
+      MOZ_DIAGNOSTIC_ASSERT(opener->mUseRemoteTabs == mUseRemoteTabs);
+      MOZ_DIAGNOSTIC_ASSERT(opener->mUseRemoteSubframes == mUseRemoteSubframes);
+      MOZ_DIAGNOSTIC_ASSERT(opener->mPrivateBrowsingId == mPrivateBrowsingId);
+      MOZ_DIAGNOSTIC_ASSERT(
+          opener->mOriginAttributes.EqualsIgnoringFPD(mOriginAttributes));
+    }
+  }
+  if (RefPtr<BrowsingContext> parent = GetParent()) {
+    MOZ_DIAGNOSTIC_ASSERT(parent->mType == mType);
+    MOZ_DIAGNOSTIC_ASSERT(parent->mGroup == mGroup);
+    MOZ_DIAGNOSTIC_ASSERT(parent->mUseRemoteTabs == mUseRemoteTabs);
+    MOZ_DIAGNOSTIC_ASSERT(parent->mUseRemoteSubframes == mUseRemoteSubframes);
+    MOZ_DIAGNOSTIC_ASSERT(parent->mPrivateBrowsingId == mPrivateBrowsingId);
+    MOZ_DIAGNOSTIC_ASSERT(
+        parent->mOriginAttributes.EqualsIgnoringFPD(mOriginAttributes));
+  }
+
+  // UseRemoteSubframes and UseRemoteTabs must match.
+  MOZ_DIAGNOSTIC_ASSERT(
+      !mUseRemoteSubframes || mUseRemoteTabs,
+      "Cannot set useRemoteSubframes without also setting useRemoteTabs");
+
+  // Double-check OriginAttributes/Private Browsing
+  AssertOriginAttributesMatchPrivateBrowsing();
+#endif
+}
+
+void BrowsingContext::AssertOriginAttributesMatchPrivateBrowsing() {
+  // Chrome browsing contexts must not have a private browsing OriginAttribute
+  // Content browsing contexts must maintain the equality:
+  // mOriginAttributes.mPrivateBrowsingId == mPrivateBrowsingId
+  if (IsChrome()) {
+    MOZ_DIAGNOSTIC_ASSERT(mOriginAttributes.mPrivateBrowsingId == 0);
+  } else {
+    MOZ_DIAGNOSTIC_ASSERT(mOriginAttributes.mPrivateBrowsingId ==
+                          mPrivateBrowsingId);
+  }
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(BrowsingContext)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsILoadContext)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(BrowsingContext)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(BrowsingContext)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(BrowsingContext)
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(BrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(BrowsingContext)
+  if (sBrowsingContexts) {
+    sBrowsingContexts->Remove(tmp->Id());
+  }
+  UnregisterBrowserId(tmp);
+
+  if (tmp->GetIsPopupSpam()) {
+    PopupBlocker::UnregisterOpenPopupSpam();
+    // NOTE: Doesn't use SetIsPopupSpam, as it will be set all processes
+    // automatically.
+    tmp->mFields.SetWithoutSyncing<IDX_IsPopupSpam>(false);
+  }
+
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(
+      mDocShell, mParentWindow, mGroup, mEmbedderElement, mWindowContexts,
+      mCurrentWindowContext, mSessionStorageManager, mChildSessionHistory)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(BrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(
+      mDocShell, mParentWindow, mGroup, mEmbedderElement, mWindowContexts,
+      mCurrentWindowContext, mSessionStorageManager, mChildSessionHistory)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+static bool IsCertainlyAliveForCC(BrowsingContext* aContext) {
+  return aContext->HasKnownLiveWrapper() ||
+         (AppShutdown::GetCurrentShutdownPhase() ==
+              ShutdownPhase::NotInShutdown &&
+          aContext->EverAttached() && !aContext->IsDiscarded());
+}
+
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_BEGIN(BrowsingContext)
+  if (IsCertainlyAliveForCC(tmp)) {
+    if (tmp->PreservingWrapper()) {
+      tmp->MarkWrapperLive();
+    }
+    return true;
+  }
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_END
+
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_BEGIN(BrowsingContext)
+  return IsCertainlyAliveForCC(tmp) && tmp->HasNothingToTrace(tmp);
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_END
+
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_BEGIN(BrowsingContext)
+  return IsCertainlyAliveForCC(tmp);
+NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_END
+
+class RemoteLocationProxy
+    : public RemoteObjectProxy<BrowsingContext::LocationProxy,
+                               Location_Binding::sCrossOriginProperties> {
+ public:
+  typedef RemoteObjectProxy Base;
+
+  constexpr RemoteLocationProxy()
+      : RemoteObjectProxy(prototypes::id::Location) {}
+
+  void NoteChildren(JSObject* aProxy,
+                    nsCycleCollectionTraversalCallback& aCb) const override {
+    auto location =
+        static_cast<BrowsingContext::LocationProxy*>(GetNative(aProxy));
+    CycleCollectionNoteChild(aCb, location->GetBrowsingContext(),
+                             "JS::GetPrivate(obj)->GetBrowsingContext()");
+  }
+};
+
+static const RemoteLocationProxy sSingleton;
+
+// Give RemoteLocationProxy 2 reserved slots, like the other wrappers,
+// so JSObject::swap can swap it with CrossCompartmentWrappers without requiring
+// malloc.
+template <>
+const JSClass RemoteLocationProxy::Base::sClass =
+    PROXY_CLASS_DEF("Proxy", JSCLASS_HAS_RESERVED_SLOTS(2));
+
+void BrowsingContext::Location(JSContext* aCx,
+                               JS::MutableHandle<JSObject*> aLocation,
+                               ErrorResult& aError) {
+  aError.MightThrowJSException();
+  sSingleton.GetProxyObject(aCx, &mLocation, /* aTransplantTo = */ nullptr,
+                            aLocation);
+  if (!aLocation) {
+    aError.StealExceptionFromJSContext(aCx);
+  }
+}
+
+bool BrowsingContext::RemoveRootFromBFCacheSync() {
+  if (WindowContext* wc = GetParentWindowContext()) {
+    if (RefPtr<Document> doc = wc->TopWindowContext()->GetDocument()) {
+      return doc->RemoveFromBFCacheSync();
+    }
+  }
+  return false;
+}
+
+nsresult BrowsingContext::CheckSandboxFlags(nsDocShellLoadState* aLoadState) {
+  const auto& sourceBC = aLoadState->SourceBrowsingContext();
+  if (sourceBC.IsNull()) {
+    return NS_OK;
+  }
+
+  // We might be called after the source BC has been discarded, but before we've
+  // destroyed our in-process instance of the BrowsingContext object in some
+  // situations (e.g. after creating a new pop-up with window.open while the
+  // window is being closed). In these situations we want to still perform the
+  // sandboxing check against our in-process copy. If we've forgotten about the
+  // context already, assume it is sanboxed. (bug 1643450)
+  BrowsingContext* bc = sourceBC.GetMaybeDiscarded();
+  if (!bc || bc->IsSandboxedFrom(this)) {
+    return NS_ERROR_DOM_SECURITY_ERR;
+  }
+  return NS_OK;
+}
+
+nsresult BrowsingContext::LoadURI(nsDocShellLoadState* aLoadState,
+                                  bool aSetNavigating) {
+  // Per spec, most load attempts are silently ignored when a BrowsingContext is
+  // null (which in our code corresponds to discarded), so we simply fail
+  // silently in those cases. Regardless, we cannot trigger loads in/from
+  // discarded BrowsingContexts via IPC, so we need to abort in any case.
+  if (IsDiscarded()) {
+    return NS_OK;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(aLoadState->TargetBrowsingContext().IsNull(),
+                        "Targeting occurs in InternalLoad");
+  aLoadState->AssertProcessCouldTriggerLoadIfSystem();
+
+  if (mDocShell) {
+    nsCOMPtr<nsIDocShell> docShell = mDocShell;
+    return docShell->LoadURI(aLoadState, aSetNavigating);
+  }
+
+  // Note: We do this check both here and in `nsDocShell::InternalLoad`, since
+  // document-specific sandbox flags are only available in the process
+  // triggering the load, and we don't want the target process to have to trust
+  // the triggering process to do the appropriate checks for the
+  // BrowsingContext's sandbox flags.
+  MOZ_TRY(CheckSandboxFlags(aLoadState));
+  SetTriggeringAndInheritPrincipals(aLoadState->TriggeringPrincipal(),
+                                    aLoadState->PrincipalToInherit(),
+                                    aLoadState->GetLoadIdentifier());
+
+  const auto& sourceBC = aLoadState->SourceBrowsingContext();
+
+  if (net::SchemeIsJavascript(aLoadState->URI())) {
+    if (!XRE_IsParentProcess()) {
+      // Web content should only be able to load javascript: URIs into documents
+      // whose principals the caller principal subsumes, which by definition
+      // excludes any document in a cross-process BrowsingContext.
+      return NS_ERROR_DOM_BAD_CROSS_ORIGIN_URI;
+    }
+    MOZ_DIAGNOSTIC_ASSERT(!sourceBC,
+                          "Should never see a cross-process javascript: load "
+                          "triggered from content");
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(!sourceBC || sourceBC->Group() == Group());
+  if (sourceBC && sourceBC->IsInProcess()) {
+    nsCOMPtr<nsPIDOMWindowOuter> win(sourceBC->GetDOMWindow());
+    if (WindowGlobalChild* wgc =
+            win->GetCurrentInnerWindow()->GetWindowGlobalChild()) {
+      if (!wgc->CanNavigate(this)) {
+        return NS_ERROR_DOM_PROP_ACCESS_DENIED;
+      }
+      wgc->SendLoadURI(this, mozilla::WrapNotNull(aLoadState), aSetNavigating);
+    }
+  } else if (XRE_IsParentProcess()) {
+    if (Canonical()->LoadInParent(aLoadState, aSetNavigating)) {
+      return NS_OK;
+    }
+
+    if (ContentParent* cp = Canonical()->GetContentParent()) {
+      // Attempt to initiate this load immediately in the parent, if it succeeds
+      // it'll return a unique identifier so that we can find it later.
+      uint64_t loadIdentifier = 0;
+      if (Canonical()->AttemptSpeculativeLoadInParent(aLoadState)) {
+        MOZ_DIAGNOSTIC_ASSERT(GetCurrentLoadIdentifier().isSome());
+        loadIdentifier = GetCurrentLoadIdentifier().value();
+        aLoadState->SetChannelInitialized(true);
+      }
+
+      cp->TransmitBlobDataIfBlobURL(aLoadState->URI());
+
+      // Setup a confirmation callback once the content process receives this
+      // load. Normally we'd expect a PDocumentChannel actor to have been
+      // created to claim the load identifier by that time. If not, then it
+      // won't be coming, so make sure we clean up and deregister.
+      cp->SendLoadURI(this, mozilla::WrapNotNull(aLoadState), aSetNavigating)
+          ->Then(GetMainThreadSerialEventTarget(), __func__,
+                 [loadIdentifier](
+                     const PContentParent::LoadURIPromise::ResolveOrRejectValue&
+                         aValue) {
+                   if (loadIdentifier) {
+                     net::DocumentLoadListener::CleanupParentLoadAttempt(
+                         loadIdentifier);
+                   }
+                 });
+    }
+  } else {
+    MOZ_DIAGNOSTIC_ASSERT(sourceBC);
+    if (!sourceBC) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    // If we're in a content process and the source BC is no longer in-process,
+    // just fail silently.
+  }
+  return NS_OK;
+}
+
+nsresult BrowsingContext::InternalLoad(nsDocShellLoadState* aLoadState) {
+  if (IsDiscarded()) {
+    return NS_OK;
+  }
+  SetTriggeringAndInheritPrincipals(aLoadState->TriggeringPrincipal(),
+                                    aLoadState->PrincipalToInherit(),
+                                    aLoadState->GetLoadIdentifier());
+
+  MOZ_DIAGNOSTIC_ASSERT(aLoadState->Target().IsEmpty(),
+                        "should already have retargeted");
+  MOZ_DIAGNOSTIC_ASSERT(!aLoadState->TargetBrowsingContext().IsNull(),
+                        "should have target bc set");
+  MOZ_DIAGNOSTIC_ASSERT(aLoadState->TargetBrowsingContext() == this,
+                        "must be targeting this BrowsingContext");
+  aLoadState->AssertProcessCouldTriggerLoadIfSystem();
+
+  if (mDocShell) {
+    RefPtr<nsDocShell> docShell = nsDocShell::Cast(mDocShell);
+    return docShell->InternalLoad(aLoadState);
+  }
+
+  // Note: We do this check both here and in `nsDocShell::InternalLoad`, since
+  // document-specific sandbox flags are only available in the process
+  // triggering the load, and we don't want the target process to have to trust
+  // the triggering process to do the appropriate checks for the
+  // BrowsingContext's sandbox flags.
+  MOZ_TRY(CheckSandboxFlags(aLoadState));
+
+  const auto& sourceBC = aLoadState->SourceBrowsingContext();
+
+  if (net::SchemeIsJavascript(aLoadState->URI())) {
+    if (!XRE_IsParentProcess()) {
+      // Web content should only be able to load javascript: URIs into documents
+      // whose principals the caller principal subsumes, which by definition
+      // excludes any document in a cross-process BrowsingContext.
+      return NS_ERROR_DOM_BAD_CROSS_ORIGIN_URI;
+    }
+    MOZ_DIAGNOSTIC_ASSERT(!sourceBC,
+                          "Should never see a cross-process javascript: load "
+                          "triggered from content");
+  }
+
+  if (XRE_IsParentProcess()) {
+    ContentParent* cp = Canonical()->GetContentParent();
+    if (!cp || !cp->CanSend()) {
+      return NS_ERROR_FAILURE;
+    }
+
+    MOZ_ALWAYS_SUCCEEDS(
+        SetCurrentLoadIdentifier(Some(aLoadState->GetLoadIdentifier())));
+    Unused << cp->SendInternalLoad(mozilla::WrapNotNull(aLoadState));
+  } else {
+    MOZ_DIAGNOSTIC_ASSERT(sourceBC);
+    MOZ_DIAGNOSTIC_ASSERT(sourceBC->Group() == Group());
+
+    nsCOMPtr<nsPIDOMWindowOuter> win(sourceBC->GetDOMWindow());
+    WindowGlobalChild* wgc =
+        win->GetCurrentInnerWindow()->GetWindowGlobalChild();
+    if (!wgc || !wgc->CanSend()) {
+      return NS_ERROR_FAILURE;
+    }
+    if (!wgc->CanNavigate(this)) {
+      return NS_ERROR_DOM_PROP_ACCESS_DENIED;
+    }
+
+    MOZ_ALWAYS_SUCCEEDS(
+        SetCurrentLoadIdentifier(Some(aLoadState->GetLoadIdentifier())));
+    wgc->SendInternalLoad(mozilla::WrapNotNull(aLoadState));
+  }
+
+  return NS_OK;
+}
+
+void BrowsingContext::DisplayLoadError(const nsAString& aURI) {
+  MOZ_LOG(GetLog(), LogLevel::Debug, ("DisplayLoadError"));
+  MOZ_DIAGNOSTIC_ASSERT(!IsDiscarded());
+  MOZ_DIAGNOSTIC_ASSERT(mDocShell || XRE_IsParentProcess());
+
+  if (mDocShell) {
+    bool didDisplayLoadError = false;
+    nsCOMPtr<nsIDocShell> docShell = mDocShell;
+    docShell->DisplayLoadError(NS_ERROR_MALFORMED_URI, nullptr,
+                               PromiseFlatString(aURI).get(), nullptr,
+                               &didDisplayLoadError);
+  } else {
+    if (ContentParent* cp = Canonical()->GetContentParent()) {
+      Unused << cp->SendDisplayLoadError(this, PromiseFlatString(aURI));
+    }
+  }
+}
+
+WindowProxyHolder BrowsingContext::Window() {
+  return WindowProxyHolder(Self());
+}
+
+WindowProxyHolder BrowsingContext::GetFrames(ErrorResult& aError) {
+  return Window();
+}
+
+void BrowsingContext::Close(CallerType aCallerType, ErrorResult& aError) {
+  if (mIsDiscarded) {
+    return;
+  }
+
+  if (IsSubframe()) {
+    // .close() on frames is a no-op.
+    return;
+  }
+
+  if (GetDOMWindow()) {
+    nsGlobalWindowOuter::Cast(GetDOMWindow())
+        ->CloseOuter(aCallerType == CallerType::System);
+    return;
+  }
+
+  // This is a bit of a hack for webcompat. Content needs to see an updated
+  // |window.closed| value as early as possible, so we set this before we
+  // actually send the DOMWindowClose event, which happens in the process where
+  // the document for this browsing context is loaded.
+  MOZ_ALWAYS_SUCCEEDS(SetClosed(true));
+
+  if (ContentChild* cc = ContentChild::GetSingleton()) {
+    cc->SendWindowClose(this, aCallerType == CallerType::System);
+  } else if (ContentParent* cp = Canonical()->GetContentParent()) {
+    Unused << cp->SendWindowClose(this, aCallerType == CallerType::System);
+  }
+}
+
+template <typename FuncT>
+inline bool ApplyToDocumentsForPopup(Document* doc, FuncT func) {
+  // HACK: Some pages using bogus library + UA sniffing call window.open()
+  // from a blank iframe, only on Firefox, see bug 1685056.
+  //
+  // This is a hack-around to preserve behavior in that particular and
+  // specific case, by consuming activation on the parent document, so we
+  // don't care about the InProcessParent bits not being fission-safe or what
+  // not.
+  if (func(doc)) {
+    return true;
+  }
+  if (!doc->IsInitialDocument()) {
+    return false;
+  }
+  Document* parentDoc = doc->GetInProcessParentDocument();
+  if (!parentDoc || !parentDoc->NodePrincipal()->Equals(doc->NodePrincipal())) {
+    return false;
+  }
+  return func(parentDoc);
+}
+
+PopupBlocker::PopupControlState BrowsingContext::RevisePopupAbuseLevel(
+    PopupBlocker::PopupControlState aControl) {
+  if (!IsContent()) {
+    return PopupBlocker::openAllowed;
+  }
+
+  RefPtr<Document> doc = GetExtantDocument();
+  PopupBlocker::PopupControlState abuse = aControl;
+  switch (abuse) {
+    case PopupBlocker::openControlled:
+    case PopupBlocker::openBlocked:
+    case PopupBlocker::openOverridden:
+      if (IsPopupAllowed()) {
+        abuse = PopupBlocker::PopupControlState(abuse - 1);
+      }
+      break;
+    case PopupBlocker::openAbused:
+      if (IsPopupAllowed() ||
+          (doc && doc->HasValidTransientUserGestureActivation())) {
+        // Skip PopupBlocker::openBlocked
+        abuse = PopupBlocker::openControlled;
+      }
+      break;
+    case PopupBlocker::openAllowed:
+      break;
+    default:
+      NS_WARNING("Strange PopupControlState!");
+  }
+
+  // limit the number of simultaneously open popups
+  if (abuse == PopupBlocker::openAbused || abuse == PopupBlocker::openBlocked ||
+      abuse == PopupBlocker::openControlled) {
+    int32_t popupMax = StaticPrefs::dom_popup_maximum();
+    if (popupMax >= 0 &&
+        PopupBlocker::GetOpenPopupSpamCount() >= (uint32_t)popupMax) {
+      abuse = PopupBlocker::openOverridden;
+    }
+  }
+
+  // If we're currently in-process, attempt to consume transient user gesture
+  // activations.
+  if (doc) {
+    auto ConsumeTransientUserActivationForMultiplePopupBlocking =
+        [&]() -> bool {
+      return ApplyToDocumentsForPopup(doc, [](Document* doc) {
+        return doc->ConsumeTransientUserGestureActivation();
+      });
+    };
+
+    // If this popup is allowed, let's block any other for this event, forcing
+    // PopupBlocker::openBlocked state.
+    if ((abuse == PopupBlocker::openAllowed ||
+         abuse == PopupBlocker::openControlled) &&
+        StaticPrefs::dom_block_multiple_popups() && !IsPopupAllowed() &&
+        !ConsumeTransientUserActivationForMultiplePopupBlocking()) {
+      nsContentUtils::ReportToConsole(nsIScriptError::warningFlag, "DOM"_ns,
+                                      doc, nsContentUtils::eDOM_PROPERTIES,
+                                      "MultiplePopupsBlockedNoUserActivation");
+      abuse = PopupBlocker::openBlocked;
+    }
+  }
+
+  return abuse;
+}
+
+void BrowsingContext::GetUserActivationModifiersForPopup(
+    UserActivation::Modifiers* aModifiers) {
+  RefPtr<Document> doc = GetExtantDocument();
+  if (doc) {
+    // Unlike RevisePopupAbuseLevel, modifiers can always be used regardless
+    // of PopupControlState.
+    (void)ApplyToDocumentsForPopup(doc, [&](Document* doc) {
+      return doc->GetTransientUserGestureActivationModifiers(aModifiers);
+    });
+  }
+}
+
+void BrowsingContext::IncrementHistoryEntryCountForBrowsingContext() {
+  Unused << SetHistoryEntryCount(GetHistoryEntryCount() + 1);
+}
+
+std::tuple<bool, bool> BrowsingContext::CanFocusCheck(CallerType aCallerType) {
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  if (!fm) {
+    return {false, false};
+  }
+
+  nsCOMPtr<nsPIDOMWindowInner> caller = do_QueryInterface(GetEntryGlobal());
+  BrowsingContext* callerBC = caller ? caller->GetBrowsingContext() : nullptr;
+  RefPtr<BrowsingContext> openerBC = GetOpener();
+  MOZ_DIAGNOSTIC_ASSERT(!openerBC || openerBC->Group() == Group());
+
+  // Enforce dom.disable_window_flip (for non-chrome), but still allow the
+  // window which opened us to raise us at times when popups are allowed
+  // (bugs 355482 and 369306).
+  bool canFocus = aCallerType == CallerType::System ||
+                  !Preferences::GetBool("dom.disable_window_flip", true);
+  if (!canFocus && openerBC == callerBC) {
+    canFocus =
+        (callerBC ? callerBC : this)
+            ->RevisePopupAbuseLevel(PopupBlocker::GetPopupControlState()) <
+        PopupBlocker::openBlocked;
+  }
+
+  bool isActive = false;
+  if (XRE_IsParentProcess()) {
+    CanonicalBrowsingContext* chromeTop = Canonical()->TopCrossChromeBoundary();
+    nsCOMPtr<nsPIDOMWindowOuter> activeWindow = fm->GetActiveWindow();
+    isActive = activeWindow == chromeTop->GetDOMWindow();
+  } else {
+    isActive = fm->GetActiveBrowsingContext() == Top();
+  }
+
+  return {canFocus, isActive};
+}
+
+void BrowsingContext::Focus(CallerType aCallerType, ErrorResult& aError) {
+  // These checks need to happen before the RequestFrameFocus call, which
+  // is why they are done in an untrusted process. If we wanted to enforce
+  // these in the parent, we'd need to do the checks there _also_.
+  // These should be kept in sync with nsGlobalWindowOuter::FocusOuter.
+
+  auto [canFocus, isActive] = CanFocusCheck(aCallerType);
+
+  if (!(canFocus || isActive)) {
+    return;
+  }
+
+  // Permission check passed
+
+  if (mEmbedderElement) {
+    // Make the activeElement in this process update synchronously.
+    nsContentUtils::RequestFrameFocus(*mEmbedderElement, true, aCallerType);
+  }
+  uint64_t actionId = nsFocusManager::GenerateFocusActionId();
+  if (ContentChild* cc = ContentChild::GetSingleton()) {
+    cc->SendWindowFocus(this, aCallerType, actionId);
+  } else if (ContentParent* cp = Canonical()->GetContentParent()) {
+    Unused << cp->SendWindowFocus(this, aCallerType, actionId);
+  }
+}
+
+bool BrowsingContext::CanBlurCheck(CallerType aCallerType) {
+  // If dom.disable_window_flip == true, then content should not be allowed
+  // to do blur (this would allow popunders, bug 369306)
+  return aCallerType == CallerType::System ||
+         !Preferences::GetBool("dom.disable_window_flip", true);
+}
+
+void BrowsingContext::Blur(CallerType aCallerType, ErrorResult& aError) {
+  if (!CanBlurCheck(aCallerType)) {
+    return;
+  }
+
+  if (ContentChild* cc = ContentChild::GetSingleton()) {
+    cc->SendWindowBlur(this, aCallerType);
+  } else if (ContentParent* cp = Canonical()->GetContentParent()) {
+    Unused << cp->SendWindowBlur(this, aCallerType);
+  }
+}
+
+Nullable<WindowProxyHolder> BrowsingContext::GetWindow() {
+  if (XRE_IsParentProcess() && !IsInProcess()) {
+    return nullptr;
+  }
+  return WindowProxyHolder(this);
+}
+
+Nullable<WindowProxyHolder> BrowsingContext::GetTop(ErrorResult& aError) {
+  if (mIsDiscarded) {
+    return nullptr;
+  }
+
+  // We never return null or throw an error, but the implementation in
+  // nsGlobalWindow does and we need to use the same signature.
+  return WindowProxyHolder(Top());
+}
+
+void BrowsingContext::GetOpener(JSContext* aCx,
+                                JS::MutableHandle<JS::Value> aOpener,
+                                ErrorResult& aError) const {
+  RefPtr<BrowsingContext> opener = GetOpener();
+  if (!opener) {
+    aOpener.setNull();
+    return;
+  }
+
+  if (!ToJSValue(aCx, WindowProxyHolder(opener), aOpener)) {
+    aError.NoteJSContextException(aCx);
+  }
+}
+
+// We never throw an error, but the implementation in nsGlobalWindow does and
+// we need to use the same signature.
+Nullable<WindowProxyHolder> BrowsingContext::GetParent(ErrorResult& aError) {
+  if (mIsDiscarded) {
+    return nullptr;
+  }
+
+  if (GetParent()) {
+    return WindowProxyHolder(GetParent());
+  }
+  return WindowProxyHolder(this);
+}
+
+void BrowsingContext::PostMessageMoz(JSContext* aCx,
+                                     JS::Handle<JS::Value> aMessage,
+                                     const nsAString& aTargetOrigin,
+                                     const Sequence<JSObject*>& aTransfer,
+                                     nsIPrincipal& aSubjectPrincipal,
+                                     ErrorResult& aError) {
+  if (mIsDiscarded) {
+    return;
+  }
+
+  RefPtr<BrowsingContext> sourceBc;
+  PostMessageData data;
+  data.targetOrigin() = aTargetOrigin;
+  data.subjectPrincipal() = &aSubjectPrincipal;
+  RefPtr<nsGlobalWindowInner> callerInnerWindow;
+  nsAutoCString scriptLocation;
+  // We don't need to get the caller's agentClusterId since that is used for
+  // checking whether it's okay to sharing memory (and it's not allowed to share
+  // memory cross processes)
+  if (!nsGlobalWindowOuter::GatherPostMessageData(
+          aCx, aTargetOrigin, getter_AddRefs(sourceBc), data.origin(),
+          getter_AddRefs(data.targetOriginURI()),
+          getter_AddRefs(data.callerPrincipal()),
+          getter_AddRefs(callerInnerWindow), getter_AddRefs(data.callerURI()),
+          /* aCallerAgentClusterId */ nullptr, &scriptLocation, aError)) {
+    return;
+  }
+  if (sourceBc && sourceBc->IsDiscarded()) {
+    return;
+  }
+  data.source() = sourceBc;
+  data.isFromPrivateWindow() =
+      callerInnerWindow &&
+      nsScriptErrorBase::ComputeIsFromPrivateWindow(callerInnerWindow);
+  data.innerWindowId() = callerInnerWindow ? callerInnerWindow->WindowID() : 0;
+  data.scriptLocation() = scriptLocation;
+  JS::Rooted<JS::Value> transferArray(aCx);
+  aError = nsContentUtils::CreateJSValueFromSequenceOfObject(aCx, aTransfer,
+                                                             &transferArray);
+  if (NS_WARN_IF(aError.Failed())) {
+    return;
+  }
+
+  JS::CloneDataPolicy clonePolicy;
+  if (callerInnerWindow && callerInnerWindow->IsSharedMemoryAllowed()) {
+    clonePolicy.allowSharedMemoryObjects();
+  }
+
+  // We will see if the message is required to be in the same process or it can
+  // be in the different process after Write().
+  ipc::StructuredCloneData message = ipc::StructuredCloneData(
+      StructuredCloneHolder::StructuredCloneScope::UnknownDestination,
+      StructuredCloneHolder::TransferringSupported);
+  message.Write(aCx, aMessage, transferArray, clonePolicy, aError);
+  if (NS_WARN_IF(aError.Failed())) {
+    return;
+  }
+
+  ClonedOrErrorMessageData messageData;
+  if (ContentChild* cc = ContentChild::GetSingleton()) {
+    // The clone scope gets set when we write the message data based on the
+    // requirements of that data that we're writing.
+    // If the message data contains a shared memory object, then CloneScope
+    // would return SameProcess. Otherwise, it returns DifferentProcess.
+    if (message.CloneScope() ==
+        StructuredCloneHolder::StructuredCloneScope::DifferentProcess) {
+      ClonedMessageData clonedMessageData;
+      if (!message.BuildClonedMessageData(clonedMessageData)) {
+        aError.Throw(NS_ERROR_FAILURE);
+        return;
+      }
+
+      messageData = std::move(clonedMessageData);
+    } else {
+      MOZ_ASSERT(message.CloneScope() ==
+                 StructuredCloneHolder::StructuredCloneScope::SameProcess);
+
+      messageData = ErrorMessageData();
+
+      nsContentUtils::ReportToConsole(
+          nsIScriptError::warningFlag, "DOM Window"_ns,
+          callerInnerWindow ? callerInnerWindow->GetDocument() : nullptr,
+          nsContentUtils::eDOM_PROPERTIES,
+          "PostMessageSharedMemoryObjectToCrossOriginWarning");
+    }
+
+    cc->SendWindowPostMessage(this, messageData, data);
+  } else if (ContentParent* cp = Canonical()->GetContentParent()) {
+    if (message.CloneScope() ==
+        StructuredCloneHolder::StructuredCloneScope::DifferentProcess) {
+      ClonedMessageData clonedMessageData;
+      if (!message.BuildClonedMessageData(clonedMessageData)) {
+        aError.Throw(NS_ERROR_FAILURE);
+        return;
+      }
+
+      messageData = std::move(clonedMessageData);
+    } else {
+      MOZ_ASSERT(message.CloneScope() ==
+                 StructuredCloneHolder::StructuredCloneScope::SameProcess);
+
+      messageData = ErrorMessageData();
+
+      nsContentUtils::ReportToConsole(
+          nsIScriptError::warningFlag, "DOM Window"_ns,
+          callerInnerWindow ? callerInnerWindow->GetDocument() : nullptr,
+          nsContentUtils::eDOM_PROPERTIES,
+          "PostMessageSharedMemoryObjectToCrossOriginWarning");
+    }
+
+    Unused << cp->SendWindowPostMessage(this, messageData, data);
+  }
+}
+
+void BrowsingContext::PostMessageMoz(JSContext* aCx,
+                                     JS::Handle<JS::Value> aMessage,
+                                     const WindowPostMessageOptions& aOptions,
+                                     nsIPrincipal& aSubjectPrincipal,
+                                     ErrorResult& aError) {
+  PostMessageMoz(aCx, aMessage, aOptions.mTargetOrigin, aOptions.mTransfer,
+                 aSubjectPrincipal, aError);
+}
+
+void BrowsingContext::SendCommitTransaction(ContentParent* aParent,
+                                            const BaseTransaction& aTxn,
+                                            uint64_t aEpoch) {
+  Unused << aParent->SendCommitBrowsingContextTransaction(this, aTxn, aEpoch);
+}
+
+void BrowsingContext::SendCommitTransaction(ContentChild* aChild,
+                                            const BaseTransaction& aTxn,
+                                            uint64_t aEpoch) {
+  aChild->SendCommitBrowsingContextTransaction(this, aTxn, aEpoch);
+}
+
+BrowsingContext::IPCInitializer BrowsingContext::GetIPCInitializer() {
+  MOZ_DIAGNOSTIC_ASSERT(mEverAttached);
+  MOZ_DIAGNOSTIC_ASSERT(mType == Type::Content);
+
+  IPCInitializer init;
+  init.mId = Id();
+  init.mParentId = mParentWindow ? mParentWindow->Id() : 0;
+  init.mWindowless = mWindowless;
+  init.mUseRemoteTabs = mUseRemoteTabs;
+  init.mUseRemoteSubframes = mUseRemoteSubframes;
+  init.mCreatedDynamically = mCreatedDynamically;
+  init.mChildOffset = mChildOffset;
+  init.mOriginAttributes = mOriginAttributes;
+  if (mChildSessionHistory && mozilla::SessionHistoryInParent()) {
+    init.mSessionHistoryIndex = mChildSessionHistory->Index();
+    init.mSessionHistoryCount = mChildSessionHistory->Count();
+  }
+  init.mRequestContextId = mRequestContextId;
+  init.mFields = mFields.RawValues();
+  return init;
+}
+
+already_AddRefed<WindowContext> BrowsingContext::IPCInitializer::GetParent() {
+  RefPtr<WindowContext> parent;
+  if (mParentId != 0) {
+    parent = WindowContext::GetById(mParentId);
+    MOZ_RELEASE_ASSERT(parent);
+  }
+  return parent.forget();
+}
+
+already_AddRefed<BrowsingContext> BrowsingContext::IPCInitializer::GetOpener() {
+  RefPtr<BrowsingContext> opener;
+  if (GetOpenerId() != 0) {
+    opener = BrowsingContext::Get(GetOpenerId());
+    MOZ_RELEASE_ASSERT(opener);
+  }
+  return opener.forget();
+}
+
+void BrowsingContext::StartDelayedAutoplayMediaComponents() {
+  if (!mDocShell) {
+    return;
+  }
+  AUTOPLAY_LOG("%s : StartDelayedAutoplayMediaComponents for bc 0x%08" PRIx64,
+               XRE_IsParentProcess() ? "Parent" : "Child", Id());
+  mDocShell->StartDelayedAutoplayMediaComponents();
+}
+
+nsresult BrowsingContext::ResetGVAutoplayRequestStatus() {
+  MOZ_ASSERT(IsTop(),
+             "Should only set GVAudibleAutoplayRequestStatus in the top-level "
+             "browsing context");
+
+  Transaction txn;
+  txn.SetGVAudibleAutoplayRequestStatus(GVAutoplayRequestStatus::eUNKNOWN);
+  txn.SetGVInaudibleAutoplayRequestStatus(GVAutoplayRequestStatus::eUNKNOWN);
+  return txn.Commit(this);
+}
+
+template <typename Callback>
+void BrowsingContext::WalkPresContexts(Callback&& aCallback) {
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    if (nsIDocShell* shell = aContext->GetDocShell()) {
+      if (RefPtr pc = shell->GetPresContext()) {
+        aCallback(pc.get());
+      }
+    }
+  });
+}
+
+void BrowsingContext::PresContextAffectingFieldChanged() {
+  WalkPresContexts([&](nsPresContext* aPc) {
+    aPc->RecomputeBrowsingContextDependentData();
+  });
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_SessionStoreEpoch>,
+                             uint32_t aOldValue) {
+  if (!mCurrentWindowContext) {
+    return;
+  }
+  SessionStoreChild* sessionStoreChild =
+      SessionStoreChild::From(mCurrentWindowContext->GetWindowGlobalChild());
+  if (!sessionStoreChild) {
+    return;
+  }
+
+  sessionStoreChild->SetEpoch(GetSessionStoreEpoch());
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_GVAudibleAutoplayRequestStatus>) {
+  MOZ_ASSERT(IsTop(),
+             "Should only set GVAudibleAutoplayRequestStatus in the top-level "
+             "browsing context");
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_GVInaudibleAutoplayRequestStatus>) {
+  MOZ_ASSERT(IsTop(),
+             "Should only set GVAudibleAutoplayRequestStatus in the top-level "
+             "browsing context");
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_ExplicitActive>,
+                             const ExplicitActiveStatus&,
+                             ContentParent* aSource) {
+  return XRE_IsParentProcess() && IsTop() && !aSource;
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_ExplicitActive>,
+                             ExplicitActiveStatus aOldValue) {
+  MOZ_ASSERT(IsTop());
+
+  const bool isActive = IsActive();
+  const bool wasActive = [&] {
+    if (aOldValue != ExplicitActiveStatus::None) {
+      return aOldValue == ExplicitActiveStatus::Active;
+    }
+    return GetParent() && GetParent()->IsActive();
+  }();
+
+  if (isActive == wasActive) {
+    return;
+  }
+
+  Group()->UpdateToplevelsSuspendedIfNeeded();
+  if (XRE_IsParentProcess()) {
+    if (BrowserParent* bp = Canonical()->GetBrowserParent()) {
+      bp->RecomputeProcessPriority();
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+      if (a11y::Compatibility::IsDolphin()) {
+        // update active accessible documents on windows
+        if (a11y::DocAccessibleParent* tabDoc =
+                bp->GetTopLevelDocAccessible()) {
+          HWND window = tabDoc->GetEmulatedWindowHandle();
+          MOZ_ASSERT(window);
+          if (window) {
+            if (isActive) {
+              a11y::nsWinUtils::ShowNativeWindow(window);
+            } else {
+              a11y::nsWinUtils::HideNativeWindow(window);
+            }
+          }
+        }
+      }
+#endif
+    }
+
+    // NOTE(emilio): Ideally we'd want to reuse the ExplicitActiveStatus::None
+    // set-up, but that's non-trivial to do because in content processes we
+    // can't access the top-cross-chrome-boundary bc.
+    auto manageTopDescendant = [&](auto* aChild) {
+      if (!aChild->ManuallyManagesActiveness()) {
+        aChild->SetIsActiveInternal(isActive, IgnoreErrors());
+        if (BrowserParent* bp = aChild->GetBrowserParent()) {
+          bp->SetRenderLayers(isActive);
+        }
+      }
+      return CallState::Continue;
+    };
+    Canonical()->CallOnAllTopDescendants(manageTopDescendant,
+                                         /* aIncludeNestedBrowsers = */ false);
+  }
+
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    if (nsCOMPtr<nsIDocShell> ds = aContext->GetDocShell()) {
+      nsDocShell::Cast(ds)->ActivenessMaybeChanged();
+    }
+  });
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_InRDMPane>, bool aOldValue) {
+  MOZ_ASSERT(IsTop(),
+             "Should only set InRDMPane in the top-level browsing context");
+  if (GetInRDMPane() == aOldValue) {
+    return;
+  }
+  PresContextAffectingFieldChanged();
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_PageAwakeRequestCount>,
+                             uint32_t aNewValue, ContentParent* aSource) {
+  return IsTop() && XRE_IsParentProcess() && !aSource;
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_PageAwakeRequestCount>,
+                             uint32_t aOldValue) {
+  if (!IsTop() || aOldValue == GetPageAwakeRequestCount()) {
+    return;
+  }
+  Group()->UpdateToplevelsSuspendedIfNeeded();
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_AllowJavascript>, bool aValue,
+                             ContentParent* aSource) -> CanSetResult {
+  if (mozilla::SessionHistoryInParent()) {
+    return XRE_IsParentProcess() && !aSource ? CanSetResult::Allow
+                                             : CanSetResult::Deny;
+  }
+
+  // Without Session History in Parent, session restore code still needs to set
+  // this from content processes.
+  return LegacyRevertIfNotOwningOrParentProcess(aSource);
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_AllowJavascript>, bool aOldValue) {
+  RecomputeCanExecuteScripts();
+}
+
+void BrowsingContext::RecomputeCanExecuteScripts() {
+  const bool old = mCanExecuteScripts;
+  if (!AllowJavascript()) {
+    // Scripting has been explicitly disabled on our BrowsingContext.
+    mCanExecuteScripts = false;
+  } else if (GetParentWindowContext()) {
+    // Otherwise, inherit parent.
+    mCanExecuteScripts = GetParentWindowContext()->CanExecuteScripts();
+  } else {
+    // Otherwise, we're the root of the tree, and we haven't explicitly disabled
+    // script. Allow.
+    mCanExecuteScripts = true;
+  }
+
+  if (old != mCanExecuteScripts) {
+    for (WindowContext* wc : GetWindowContexts()) {
+      wc->RecomputeCanExecuteScripts();
+    }
+  }
+}
+
+bool BrowsingContext::InactiveForSuspend() const {
+  if (!StaticPrefs::dom_suspend_inactive_enabled()) {
+    return false;
+  }
+  // We should suspend a page only when it's inactive and doesn't have any awake
+  // request that is used to prevent page from being suspended because web page
+  // might still need to run their script. Eg. waiting for media keys to resume
+  // media, playing web audio, waiting in a video call conference room.
+  return !IsActive() && GetPageAwakeRequestCount() == 0;
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_TouchEventsOverrideInternal>,
+                             dom::TouchEventsOverride, ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource;
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_TouchEventsOverrideInternal>,
+                             dom::TouchEventsOverride&& aOldValue) {
+  if (GetTouchEventsOverrideInternal() == aOldValue) {
+    return;
+  }
+  WalkPresContexts([&](nsPresContext* aPc) {
+    aPc->MediaFeatureValuesChanged(
+        {MediaFeatureChangeReason::SystemMetricsChange},
+        // We're already iterating through sub documents, so we don't need to
+        // propagate the change again.
+        MediaFeatureChangePropagation::JustThisDocument);
+  });
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_EmbedderColorSchemes>,
+                             EmbedderColorSchemes&& aOldValue) {
+  if (GetEmbedderColorSchemes() == aOldValue) {
+    return;
+  }
+  PresContextAffectingFieldChanged();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+                             dom::PrefersColorSchemeOverride aOldValue) {
+  MOZ_ASSERT(IsTop());
+  if (PrefersColorSchemeOverride() == aOldValue) {
+    return;
+  }
+  PresContextAffectingFieldChanged();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_MediumOverride>,
+                             nsString&& aOldValue) {
+  MOZ_ASSERT(IsTop());
+  if (GetMediumOverride() == aOldValue) {
+    return;
+  }
+  PresContextAffectingFieldChanged();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_DisplayMode>,
+                             enum DisplayMode aOldValue) {
+  MOZ_ASSERT(IsTop());
+
+  if (GetDisplayMode() == aOldValue) {
+    return;
+  }
+
+  WalkPresContexts([&](nsPresContext* aPc) {
+    aPc->MediaFeatureValuesChanged(
+        {MediaFeatureChangeReason::DisplayModeChange},
+        // We're already iterating through sub documents, so we don't need
+        // to propagate the change again.
+        //
+        // Images and other resources don't change their display-mode
+        // evaluation, display-mode is a property of the browsing context.
+        MediaFeatureChangePropagation::JustThisDocument);
+  });
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_Muted>) {
+  MOZ_ASSERT(IsTop(), "Set muted flag on non top-level context!");
+  USER_ACTIVATION_LOG("Set audio muted %d for %s browsing context 0x%08" PRIx64,
+                      GetMuted(), XRE_IsParentProcess() ? "Parent" : "Child",
+                      Id());
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    nsPIDOMWindowOuter* win = aContext->GetDOMWindow();
+    if (win) {
+      win->RefreshMediaElementsVolume();
+    }
+  });
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_IsAppTab>, const bool& aValue,
+                             ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource && IsTop();
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_HasSiblings>, const bool& aValue,
+                             ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource && IsTop();
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_ShouldDelayMediaFromStart>,
+                             const bool& aValue, ContentParent* aSource) {
+  return IsTop();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_ShouldDelayMediaFromStart>,
+                             bool aOldValue) {
+  MOZ_ASSERT(IsTop(), "Set attribute on non top-level context!");
+  if (aOldValue == GetShouldDelayMediaFromStart()) {
+    return;
+  }
+  if (!GetShouldDelayMediaFromStart()) {
+    PreOrderWalk([&](BrowsingContext* aContext) {
+      if (nsPIDOMWindowOuter* win = aContext->GetDOMWindow()) {
+        win->ActivateMediaComponents();
+      }
+    });
+  }
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_OverrideDPPX>, const float& aValue,
+                             ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource && IsTop();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_OverrideDPPX>, float aOldValue) {
+  MOZ_ASSERT(IsTop());
+  if (GetOverrideDPPX() == aOldValue) {
+    return;
+  }
+  PresContextAffectingFieldChanged();
+}
+
+void BrowsingContext::SetCustomUserAgent(const nsAString& aUserAgent,
+                                         ErrorResult& aRv) {
+  Top()->SetUserAgentOverride(aUserAgent, aRv);
+}
+
+nsresult BrowsingContext::SetCustomUserAgent(const nsAString& aUserAgent) {
+  return Top()->SetUserAgentOverride(aUserAgent);
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_UserAgentOverride>) {
+  MOZ_ASSERT(IsTop());
+
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    nsIDocShell* shell = aContext->GetDocShell();
+    if (shell) {
+      shell->ClearCachedUserAgent();
+    }
+  });
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_IsInBFCache>, bool,
+                             ContentParent* aSource) {
+  return IsTop() && !aSource && mozilla::BFCacheInParent();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_IsInBFCache>) {
+  MOZ_RELEASE_ASSERT(mozilla::BFCacheInParent());
+  MOZ_DIAGNOSTIC_ASSERT(IsTop());
+
+  const bool isInBFCache = GetIsInBFCache();
+  if (!isInBFCache) {
+    UpdateCurrentTopByBrowserId(this);
+    PreOrderWalk([&](BrowsingContext* aContext) {
+      aContext->mIsInBFCache = false;
+      nsCOMPtr<nsIDocShell> shell = aContext->GetDocShell();
+      if (shell) {
+        nsDocShell::Cast(shell)->ThawFreezeNonRecursive(true);
+      }
+    });
+  }
+
+  if (isInBFCache && XRE_IsContentProcess() && mDocShell) {
+    nsDocShell::Cast(mDocShell)->MaybeDisconnectChildListenersOnPageHide();
+  }
+
+  if (isInBFCache) {
+    PreOrderWalk([&](BrowsingContext* aContext) {
+      nsCOMPtr<nsIDocShell> shell = aContext->GetDocShell();
+      if (shell) {
+        nsDocShell::Cast(shell)->FirePageHideShowNonRecursive(false);
+      }
+    });
+  } else {
+    PostOrderWalk([&](BrowsingContext* aContext) {
+      nsCOMPtr<nsIDocShell> shell = aContext->GetDocShell();
+      if (shell) {
+        nsDocShell::Cast(shell)->FirePageHideShowNonRecursive(true);
+      }
+    });
+  }
+
+  if (isInBFCache) {
+    PreOrderWalk([&](BrowsingContext* aContext) {
+      nsCOMPtr<nsIDocShell> shell = aContext->GetDocShell();
+      if (shell) {
+        nsDocShell::Cast(shell)->ThawFreezeNonRecursive(false);
+        if (nsPresContext* pc = shell->GetPresContext()) {
+          pc->EventStateManager()->ResetHoverState();
+        }
+      }
+      aContext->mIsInBFCache = true;
+      Document* doc = aContext->GetDocument();
+      if (doc) {
+        // Notifying needs to happen after mIsInBFCache is set to true.
+        doc->NotifyActivityChanged();
+      }
+    });
+
+    if (XRE_IsParentProcess()) {
+      if (mCurrentWindowContext &&
+          mCurrentWindowContext->Canonical()->Fullscreen()) {
+        mCurrentWindowContext->Canonical()->ExitTopChromeDocumentFullscreen();
+      }
+    }
+  }
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_SyntheticDocumentContainer>) {
+  if (WindowContext* parentWindowContext = GetParentWindowContext()) {
+    parentWindowContext->UpdateChildSynthetic(this,
+                                              GetSyntheticDocumentContainer());
+  }
+}
+
+void BrowsingContext::SetCustomPlatform(const nsAString& aPlatform,
+                                        ErrorResult& aRv) {
+  Top()->SetPlatformOverride(aPlatform, aRv);
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_PlatformOverride>) {
+  MOZ_ASSERT(IsTop());
+
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    nsIDocShell* shell = aContext->GetDocShell();
+    if (shell) {
+      shell->ClearCachedPlatform();
+    }
+  });
+}
+
+auto BrowsingContext::LegacyRevertIfNotOwningOrParentProcess(
+    ContentParent* aSource) -> CanSetResult {
+  if (aSource) {
+    MOZ_ASSERT(XRE_IsParentProcess());
+
+    if (!Canonical()->IsOwnedByProcess(aSource->ChildID())) {
+      return CanSetResult::Revert;
+    }
+  } else if (!IsInProcess() && !XRE_IsParentProcess()) {
+    // Don't allow this to be set from content processes that
+    // don't own the BrowsingContext.
+    return CanSetResult::Deny;
+  }
+
+  return CanSetResult::Allow;
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_IsActiveBrowserWindowInternal>,
+                             const bool& aValue, ContentParent* aSource) {
+  // Should only be set in the parent process.
+  return XRE_IsParentProcess() && !aSource && IsTop();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_IsActiveBrowserWindowInternal>,
+                             bool aOldValue) {
+  bool isActivateEvent = GetIsActiveBrowserWindowInternal();
+  // The browser window containing this context has changed
+  // activation state so update window inactive document states
+  // for all in-process documents.
+  PreOrderWalk([isActivateEvent](BrowsingContext* aContext) {
+    if (RefPtr<Document> doc = aContext->GetExtantDocument()) {
+      doc->UpdateDocumentStates(DocumentState::WINDOW_INACTIVE, true);
+
+      RefPtr<nsPIDOMWindowInner> win = doc->GetInnerWindow();
+      if (win) {
+        RefPtr<MediaDevices> devices;
+        if (isActivateEvent && (devices = win->GetExtantMediaDevices())) {
+          devices->BrowserWindowBecameActive();
+        }
+
+        if (XRE_IsContentProcess() &&
+            (!aContext->GetParent() || !aContext->GetParent()->IsInProcess())) {
+          // Send the inner window an activate/deactivate event if
+          // the context is the top of a sub-tree of in-process
+          // contexts.
+          nsContentUtils::DispatchEventOnlyToChrome(
+              doc, nsGlobalWindowInner::Cast(win),
+              isActivateEvent ? u"activate"_ns : u"deactivate"_ns,
+              CanBubble::eYes, Cancelable::eYes, nullptr);
+        }
+      }
+    }
+  });
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_OpenerPolicy>,
+                             nsILoadInfo::CrossOriginOpenerPolicy aPolicy,
+                             ContentParent* aSource) {
+  // A potentially cross-origin isolated BC can't change opener policy, nor can
+  // a BC become potentially cross-origin isolated. An unchanged policy is
+  // always OK.
+  return GetOpenerPolicy() == aPolicy ||
+         (GetOpenerPolicy() !=
+              nsILoadInfo::
+                  OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP &&
+          aPolicy !=
+              nsILoadInfo::
+                  OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP);
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_AllowContentRetargeting>,
+                             const bool& aAllowContentRetargeting,
+                             ContentParent* aSource) -> CanSetResult {
+  return LegacyRevertIfNotOwningOrParentProcess(aSource);
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_AllowContentRetargetingOnChildren>,
+                             const bool& aAllowContentRetargetingOnChildren,
+                             ContentParent* aSource) -> CanSetResult {
+  return LegacyRevertIfNotOwningOrParentProcess(aSource);
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_FullscreenAllowedByOwner>,
+                             const bool& aAllowed, ContentParent* aSource) {
+  return CheckOnlyEmbedderCanSet(aSource);
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_UseErrorPages>,
+                             const bool& aUseErrorPages,
+                             ContentParent* aSource) {
+  return CheckOnlyEmbedderCanSet(aSource);
+}
+
+TouchEventsOverride BrowsingContext::TouchEventsOverride() const {
+  for (const auto* bc = this; bc; bc = bc->GetParent()) {
+    auto tev = bc->GetTouchEventsOverrideInternal();
+    if (tev != dom::TouchEventsOverride::None) {
+      return tev;
+    }
+  }
+  return dom::TouchEventsOverride::None;
+}
+
+bool BrowsingContext::TargetTopLevelLinkClicksToBlank() const {
+  return Top()->GetTargetTopLevelLinkClicksToBlankInternal();
+}
+
+// We map `watchedByDevTools` WebIDL attribute to `watchedByDevToolsInternal`
+// BC field. And we map it to the top level BrowsingContext.
+bool BrowsingContext::WatchedByDevTools() {
+  return Top()->GetWatchedByDevToolsInternal();
+}
+
+// Enforce that the watchedByDevTools BC field can only be set on the top level
+// Browsing Context.
+bool BrowsingContext::CanSet(FieldIndex<IDX_WatchedByDevToolsInternal>,
+                             const bool& aWatchedByDevTools,
+                             ContentParent* aSource) {
+  return IsTop();
+}
+void BrowsingContext::SetWatchedByDevTools(bool aWatchedByDevTools,
+                                           ErrorResult& aRv) {
+  if (!IsTop()) {
+    aRv.ThrowInvalidModificationError(
+        "watchedByDevTools can only be set on top BrowsingContext");
+    return;
+  }
+  SetWatchedByDevToolsInternal(aWatchedByDevTools, aRv);
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_DefaultLoadFlags>,
+                             const uint32_t& aDefaultLoadFlags,
+                             ContentParent* aSource) -> CanSetResult {
+  // Bug 1623565 - Are these flags only used by the debugger, which makes it
+  // possible that this field can only be settable by the parent process?
+  return LegacyRevertIfNotOwningOrParentProcess(aSource);
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_DefaultLoadFlags>) {
+  auto loadFlags = GetDefaultLoadFlags();
+  if (GetDocShell()) {
+    nsDocShell::Cast(GetDocShell())->SetLoadGroupDefaultLoadFlags(loadFlags);
+  }
+
+  if (XRE_IsParentProcess()) {
+    PreOrderWalk([&](BrowsingContext* aContext) {
+      if (aContext != this) {
+        // Setting load flags on a discarded context has no effect.
+        Unused << aContext->SetDefaultLoadFlags(loadFlags);
+      }
+    });
+  }
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_UseGlobalHistory>,
+                             const bool& aUseGlobalHistory,
+                             ContentParent* aSource) {
+  // Should only be set in the parent process.
+  //  return XRE_IsParentProcess() && !aSource;
+  return true;
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_UserAgentOverride>,
+                             const nsString& aUserAgent, ContentParent* aSource)
+    -> CanSetResult {
+  if (!IsTop()) {
+    return CanSetResult::Deny;
+  }
+
+  return LegacyRevertIfNotOwningOrParentProcess(aSource);
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_PlatformOverride>,
+                             const nsString& aPlatform, ContentParent* aSource)
+    -> CanSetResult {
+  if (!IsTop()) {
+    return CanSetResult::Deny;
+  }
+
+  return LegacyRevertIfNotOwningOrParentProcess(aSource);
+}
+
+bool BrowsingContext::CheckOnlyEmbedderCanSet(ContentParent* aSource) {
+  if (XRE_IsParentProcess()) {
+    uint64_t childId = aSource ? aSource->ChildID() : 0;
+    return Canonical()->IsEmbeddedInProcess(childId);
+  }
+  return mEmbeddedByThisProcess;
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_EmbedderInnerWindowId>,
+                             const uint64_t& aValue, ContentParent* aSource) {
+  // If we have a parent window, our embedder inner window ID must match it.
+  if (mParentWindow) {
+    return mParentWindow->Id() == aValue;
+  }
+
+  // For toplevel BrowsingContext instances, this value may only be set by the
+  // parent process, or initialized to `0`.
+  return CheckOnlyEmbedderCanSet(aSource);
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_EmbedderElementType>,
+                             const Maybe<nsString>&, ContentParent* aSource) {
+  return CheckOnlyEmbedderCanSet(aSource);
+}
+
+auto BrowsingContext::CanSet(FieldIndex<IDX_CurrentInnerWindowId>,
+                             const uint64_t& aValue, ContentParent* aSource)
+    -> CanSetResult {
+  // Generally allow clearing this. We may want to be more precise about this
+  // check in the future.
+  if (aValue == 0) {
+    return CanSetResult::Allow;
+  }
+
+  // We must have access to the specified context.
+  RefPtr<WindowContext> window = WindowContext::GetById(aValue);
+  if (!window || window->GetBrowsingContext() != this) {
+    return CanSetResult::Deny;
+  }
+
+  if (aSource) {
+    // If the sending process is no longer the current owner, revert
+    MOZ_ASSERT(XRE_IsParentProcess());
+    if (!Canonical()->IsOwnedByProcess(aSource->ChildID())) {
+      return CanSetResult::Revert;
+    }
+  } else if (XRE_IsContentProcess() && !IsOwnedByProcess()) {
+    return CanSetResult::Deny;
+  }
+
+  return CanSetResult::Allow;
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_ParentInitiatedNavigationEpoch>,
+                             const uint64_t& aValue, ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource;
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_CurrentInnerWindowId>) {
+  RefPtr<WindowContext> prevWindowContext = mCurrentWindowContext.forget();
+  mCurrentWindowContext = WindowContext::GetById(GetCurrentInnerWindowId());
+  MOZ_ASSERT(
+      !mCurrentWindowContext || mWindowContexts.Contains(mCurrentWindowContext),
+      "WindowContext not registered?");
+
+  // Clear our cached `children` value, to ensure that JS sees the up-to-date
+  // value.
+  BrowsingContext_Binding::ClearCachedChildrenValue(this);
+
+  if (XRE_IsParentProcess()) {
+    if (prevWindowContext != mCurrentWindowContext) {
+      if (prevWindowContext) {
+        prevWindowContext->Canonical()->DidBecomeCurrentWindowGlobal(false);
+      }
+      if (mCurrentWindowContext) {
+        // We set a timer when we set the current inner window. This
+        // will then flush the session storage to session store to
+        // make sure that we don't miss to store session storage to
+        // session store that is a result of navigation. This is due
+        // to Bug 1700623. We wish to fix this in Bug 1711886, where
+        // making sure to store everything would make this timer
+        // unnecessary.
+        Canonical()->MaybeScheduleSessionStoreUpdate();
+        mCurrentWindowContext->Canonical()->DidBecomeCurrentWindowGlobal(true);
+      }
+    }
+    BrowserParent::UpdateFocusFromBrowsingContext();
+  }
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_IsPopupSpam>, const bool& aValue,
+                             ContentParent* aSource) {
+  // Ensure that we only mark a browsing context as popup spam once and never
+  // unmark it.
+  return aValue && !GetIsPopupSpam();
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_IsPopupSpam>) {
+  if (GetIsPopupSpam()) {
+    PopupBlocker::RegisterOpenPopupSpam();
+  }
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_MessageManagerGroup>,
+                             const nsString& aMessageManagerGroup,
+                             ContentParent* aSource) {
+  // Should only be set in the parent process on toplevel.
+  return XRE_IsParentProcess() && !aSource && IsTopContent();
+}
+
+bool BrowsingContext::CanSet(
+    FieldIndex<IDX_OrientationLock>,
+    const mozilla::hal::ScreenOrientation& aOrientationLock,
+    ContentParent* aSource) {
+  return IsTop();
+}
+
+bool BrowsingContext::IsLoading() {
+  if (GetLoading()) {
+    return true;
+  }
+
+  // If we're in the same process as the page, we're possibly just
+  // updating the flag.
+  nsIDocShell* shell = GetDocShell();
+  if (shell) {
+    Document* doc = shell->GetDocument();
+    return doc && doc->GetReadyStateEnum() < Document::READYSTATE_COMPLETE;
+  }
+
+  return false;
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_Loading>) {
+  if (mFields.Get<IDX_Loading>()) {
+    return;
+  }
+
+  while (!mDeprioritizedLoadRunner.isEmpty()) {
+    nsCOMPtr<nsIRunnable> runner = mDeprioritizedLoadRunner.popFirst();
+    NS_DispatchToCurrentThread(runner.forget());
+  }
+
+  if (IsTop()) {
+    Group()->FlushPostMessageEvents();
+  }
+}
+
+// Inform the Document for this context of the (potential) change in
+// loading state
+void BrowsingContext::DidSet(FieldIndex<IDX_AncestorLoading>) {
+  nsPIDOMWindowOuter* outer = GetDOMWindow();
+  if (!outer) {
+    MOZ_LOG(gTimeoutDeferralLog, mozilla::LogLevel::Debug,
+            ("DidSetAncestorLoading BC: %p -- No outer window", (void*)this));
+    return;
+  }
+  Document* document = nsGlobalWindowOuter::Cast(outer)->GetExtantDoc();
+  if (document) {
+    MOZ_LOG(gTimeoutDeferralLog, mozilla::LogLevel::Debug,
+            ("DidSetAncestorLoading BC: %p -- NotifyLoading(%d, %d, %d)",
+             (void*)this, GetAncestorLoading(), document->GetReadyStateEnum(),
+             document->GetReadyStateEnum()));
+    document->NotifyLoading(GetAncestorLoading(), document->GetReadyStateEnum(),
+                            document->GetReadyStateEnum());
+  }
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_AuthorStyleDisabledDefault>) {
+  MOZ_ASSERT(IsTop(),
+             "Should only set AuthorStyleDisabledDefault in the top "
+             "browsing context");
+
+  // We don't need to handle changes to this field, since PageStyleChild.sys.mjs
+  // will respond to the PageStyle:Disable message in all content processes.
+  //
+  // But we store the state here on the top BrowsingContext so that the
+  // docshell has somewhere to look for the current author style disabling
+  // state when new iframes are inserted.
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_TextZoom>, float aOldValue) {
+  if (GetTextZoom() == aOldValue) {
+    return;
+  }
+
+  if (IsInProcess()) {
+    if (nsIDocShell* shell = GetDocShell()) {
+      if (nsPresContext* pc = shell->GetPresContext()) {
+        pc->RecomputeBrowsingContextDependentData();
+      }
+    }
+
+    for (BrowsingContext* child : Children()) {
+      // Setting text zoom on a discarded context has no effect.
+      Unused << child->SetTextZoom(GetTextZoom());
+    }
+  }
+
+  if (IsTop() && XRE_IsParentProcess()) {
+    if (Element* element = GetEmbedderElement()) {
+      AsyncEventDispatcher::RunDOMEventWhenSafe(*element, u"TextZoomChange"_ns,
+                                                CanBubble::eYes,
+                                                ChromeOnlyDispatch::eYes);
+    }
+  }
+}
+
+// TODO(emilio): It'd be potentially nicer and cheaper to allow to set this only
+// on the Top() browsing context, but there are a lot of tests that rely on
+// zooming a subframe so...
+void BrowsingContext::DidSet(FieldIndex<IDX_FullZoom>, float aOldValue) {
+  if (GetFullZoom() == aOldValue) {
+    return;
+  }
+
+  if (IsInProcess()) {
+    if (nsIDocShell* shell = GetDocShell()) {
+      if (nsPresContext* pc = shell->GetPresContext()) {
+        pc->RecomputeBrowsingContextDependentData();
+      }
+    }
+
+    for (BrowsingContext* child : Children()) {
+      // Setting full zoom on a discarded context has no effect.
+      Unused << child->SetFullZoom(GetFullZoom());
+    }
+  }
+
+  if (IsTop() && XRE_IsParentProcess()) {
+    if (Element* element = GetEmbedderElement()) {
+      AsyncEventDispatcher::RunDOMEventWhenSafe(*element, u"FullZoomChange"_ns,
+                                                CanBubble::eYes,
+                                                ChromeOnlyDispatch::eYes);
+    }
+  }
+}
+
+void BrowsingContext::AddDeprioritizedLoadRunner(nsIRunnable* aRunner) {
+  MOZ_ASSERT(IsLoading());
+  MOZ_ASSERT(Top() == this);
+
+  RefPtr<DeprioritizedLoadRunner> runner = new DeprioritizedLoadRunner(aRunner);
+  mDeprioritizedLoadRunner.insertBack(runner);
+  NS_DispatchToCurrentThreadQueue(
+      runner.forget(), StaticPrefs::page_load_deprioritization_period(),
+      EventQueuePriority::Idle);
+}
+
+bool BrowsingContext::IsDynamic() const {
+  const BrowsingContext* current = this;
+  do {
+    if (current->CreatedDynamically()) {
+      return true;
+    }
+  } while ((current = current->GetParent()));
+
+  return false;
+}
+
+bool BrowsingContext::GetOffsetPath(nsTArray<uint32_t>& aPath) const {
+  for (const BrowsingContext* current = this; current && current->GetParent();
+       current = current->GetParent()) {
+    if (current->CreatedDynamically()) {
+      return false;
+    }
+    aPath.AppendElement(current->ChildOffset());
+  }
+  return true;
+}
+
+void BrowsingContext::GetHistoryID(JSContext* aCx,
+                                   JS::MutableHandle<JS::Value> aVal,
+                                   ErrorResult& aError) {
+  if (!xpc::ID2JSValue(aCx, GetHistoryID(), aVal)) {
+    aError.Throw(NS_ERROR_OUT_OF_MEMORY);
+  }
+}
+
+void BrowsingContext::InitSessionHistory() {
+  MOZ_ASSERT(!IsDiscarded());
+  MOZ_ASSERT(IsTop());
+  MOZ_ASSERT(EverAttached());
+
+  if (!GetHasSessionHistory()) {
+    MOZ_ALWAYS_SUCCEEDS(SetHasSessionHistory(true));
+  }
+}
+
+ChildSHistory* BrowsingContext::GetChildSessionHistory() {
+  if (!mozilla::SessionHistoryInParent()) {
+    // For now we're checking that the session history object for the child
+    // process is available before returning the ChildSHistory object, because
+    // it is the actual implementation that ChildSHistory forwards to. This can
+    // be removed once session history is stored exclusively in the parent
+    // process.
+    return mChildSessionHistory && mChildSessionHistory->IsInProcess()
+               ? mChildSessionHistory.get()
+               : nullptr;
+  }
+
+  return mChildSessionHistory;
+}
+
+void BrowsingContext::CreateChildSHistory() {
+  MOZ_ASSERT(IsTop());
+  MOZ_ASSERT(GetHasSessionHistory());
+  MOZ_ASSERT(!mChildSessionHistory);
+
+  // Because session history is global in a browsing context tree, every process
+  // that has access to a browsing context tree needs access to its session
+  // history. That is why we create the ChildSHistory object in every process
+  // where we have access to this browsing context (which is the top one).
+  mChildSessionHistory = new ChildSHistory(this);
+
+  // If the top browsing context (this one) is loaded in this process then we
+  // also create the session history implementation for the child process.
+  // This can be removed once session history is stored exclusively in the
+  // parent process.
+  mChildSessionHistory->SetIsInProcess(IsInProcess());
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_HasSessionHistory>,
+                             bool aOldValue) {
+  MOZ_ASSERT(GetHasSessionHistory() || !aOldValue,
+             "We don't support turning off session history.");
+
+  if (GetHasSessionHistory() && !aOldValue) {
+    CreateChildSHistory();
+  }
+}
+
+bool BrowsingContext::CanSet(
+    FieldIndex<IDX_TargetTopLevelLinkClicksToBlankInternal>,
+    const bool& aTargetTopLevelLinkClicksToBlankInternal,
+    ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource && IsTop();
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_BrowserId>, const uint32_t& aValue,
+                             ContentParent* aSource) {
+  // We should only be able to set this for toplevel contexts which don't have
+  // an ID yet.
+  return GetBrowserId() == 0 && IsTop() && Children().IsEmpty();
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_PendingInitialization>,
+                             bool aNewValue, ContentParent* aSource) {
+  // Can only be cleared from `true` to `false`, and should only ever be set on
+  // the toplevel BrowsingContext.
+  return IsTop() && GetPendingInitialization() && !aNewValue;
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_HasRestoreData>, bool aNewValue,
+                             ContentParent* aSource) {
+  return IsTop();
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_IsUnderHiddenEmbedderElement>,
+                             const bool& aIsUnderHiddenEmbedderElement,
+                             ContentParent* aSource) {
+  return true;
+}
+
+bool BrowsingContext::CanSet(FieldIndex<IDX_ForceOffline>, bool aNewValue,
+                             ContentParent* aSource) {
+  return XRE_IsParentProcess() && !aSource;
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_IsUnderHiddenEmbedderElement>,
+                             bool aOldValue) {
+  nsIDocShell* shell = GetDocShell();
+  if (!shell) {
+    return;
+  }
+  const bool newValue = IsUnderHiddenEmbedderElement();
+  if (NS_WARN_IF(aOldValue == newValue)) {
+    return;
+  }
+
+  if (auto* bc = BrowserChild::GetFrom(shell)) {
+    bc->UpdateVisibility();
+  }
+
+  if (PresShell* presShell = shell->GetPresShell()) {
+    presShell->SetIsUnderHiddenEmbedderElement(newValue);
+  }
+
+  // Propagate to children.
+  for (BrowsingContext* child : Children()) {
+    Element* embedderElement = child->GetEmbedderElement();
+    if (!embedderElement) {
+      // TODO: We shouldn't need to null check here since `child` and the
+      // element returned by `child->GetEmbedderElement()` are in our
+      // process (the actual browsing context represented by `child` may not
+      // be, but that doesn't matter).  However, there are currently a very
+      // small number of crashes due to `embedderElement` being null, somehow
+      // - see bug 1551241.  For now we wallpaper the crash.
+      continue;
+    }
+
+    bool embedderFrameIsHidden = true;
+    if (auto* embedderFrame = embedderElement->GetPrimaryFrame()) {
+      embedderFrameIsHidden = !embedderFrame->StyleVisibility()->IsVisible();
+    }
+
+    bool hidden = IsUnderHiddenEmbedderElement() || embedderFrameIsHidden;
+    if (child->IsUnderHiddenEmbedderElement() != hidden) {
+      Unused << child->SetIsUnderHiddenEmbedderElement(hidden);
+    }
+  }
+}
+
+bool BrowsingContext::IsPopupAllowed() {
+  for (auto* context = GetCurrentWindowContext(); context;
+       context = context->GetParentWindowContext()) {
+    if (context->CanShowPopup()) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/* static */
+bool BrowsingContext::ShouldAddEntryForRefresh(
+    nsIURI* aPreviousURI, const SessionHistoryInfo& aInfo) {
+  return ShouldAddEntryForRefresh(aPreviousURI, aInfo.GetURI(),
+                                  aInfo.HasPostData());
+}
+
+/* static */
+bool BrowsingContext::ShouldAddEntryForRefresh(nsIURI* aPreviousURI,
+                                               nsIURI* aNewURI,
+                                               bool aHasPostData) {
+  if (aHasPostData) {
+    return true;
+  }
+
+  bool equalsURI = false;
+  if (aPreviousURI) {
+    aPreviousURI->Equals(aNewURI, &equalsURI);
+  }
+  return !equalsURI;
+}
+
+void BrowsingContext::SessionHistoryCommit(
+    const LoadingSessionHistoryInfo& aInfo, uint32_t aLoadType,
+    nsIURI* aPreviousURI, SessionHistoryInfo* aPreviousActiveEntry,
+    bool aPersist, bool aCloneEntryChildren, bool aChannelExpired,
+    uint32_t aCacheKey) {
+  nsID changeID = {};
+  if (XRE_IsContentProcess()) {
+    RefPtr<ChildSHistory> rootSH = Top()->GetChildSessionHistory();
+    if (rootSH) {
+      if (!aInfo.mLoadIsFromSessionHistory) {
+        // We try to mimic as closely as possible what will happen in
+        // CanonicalBrowsingContext::SessionHistoryCommit. We'll be
+        // incrementing the session history length if we're not replacing,
+        // this is a top-level load or it's not the initial load in an iframe,
+        // ShouldUpdateSessionHistory(loadType) returns true and it's not a
+        // refresh for which ShouldAddEntryForRefresh returns false.
+        // It is possible that this leads to wrong length temporarily, but
+        // so would not having the check for replace.
+        // Note that nsSHistory::AddEntry does a replace load if the current
+        // entry is not marked as a persisted entry. The child process does
+        // not have access to the current entry, so we use the previous active
+        // entry as the best approximation. When that's not the current entry
+        // then the length might be wrong briefly, until the parent process
+        // commits the actual length.
+        if (!LOAD_TYPE_HAS_FLAGS(
+                aLoadType, nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY) &&
+            (IsTop()
+                 ? (!aPreviousActiveEntry || aPreviousActiveEntry->GetPersist())
+                 : !!aPreviousActiveEntry) &&
+            ShouldUpdateSessionHistory(aLoadType) &&
+            (!LOAD_TYPE_HAS_FLAGS(aLoadType,
+                                  nsIWebNavigation::LOAD_FLAGS_IS_REFRESH) ||
+             ShouldAddEntryForRefresh(aPreviousURI, aInfo.mInfo))) {
+          changeID = rootSH->AddPendingHistoryChange();
+        }
+      } else {
+        // History load doesn't change the length, only index.
+        changeID = rootSH->AddPendingHistoryChange(aInfo.mOffset, 0);
+      }
+    }
+    ContentChild* cc = ContentChild::GetSingleton();
+    mozilla::Unused << cc->SendHistoryCommit(
+        this, aInfo.mLoadId, changeID, aLoadType, aPersist, aCloneEntryChildren,
+        aChannelExpired, aCacheKey);
+  } else {
+    Canonical()->SessionHistoryCommit(aInfo.mLoadId, changeID, aLoadType,
+                                      aPersist, aCloneEntryChildren,
+                                      aChannelExpired, aCacheKey);
+  }
+}
+
+void BrowsingContext::SetActiveSessionHistoryEntry(
+    const Maybe<nsPoint>& aPreviousScrollPos, SessionHistoryInfo* aInfo,
+    uint32_t aLoadType, uint32_t aUpdatedCacheKey, bool aUpdateLength) {
+  if (XRE_IsContentProcess()) {
+    // XXX Why we update cache key only in content process case?
+    if (aUpdatedCacheKey != 0) {
+      aInfo->SetCacheKey(aUpdatedCacheKey);
+    }
+
+    nsID changeID = {};
+    if (aUpdateLength) {
+      RefPtr<ChildSHistory> shistory = Top()->GetChildSessionHistory();
+      if (shistory) {
+        changeID = shistory->AddPendingHistoryChange();
+      }
+    }
+    ContentChild::GetSingleton()->SendSetActiveSessionHistoryEntry(
+        this, aPreviousScrollPos, *aInfo, aLoadType, aUpdatedCacheKey,
+        changeID);
+  } else {
+    Canonical()->SetActiveSessionHistoryEntry(
+        aPreviousScrollPos, aInfo, aLoadType, aUpdatedCacheKey, nsID());
+  }
+}
+
+void BrowsingContext::ReplaceActiveSessionHistoryEntry(
+    SessionHistoryInfo* aInfo) {
+  if (XRE_IsContentProcess()) {
+    ContentChild::GetSingleton()->SendReplaceActiveSessionHistoryEntry(this,
+                                                                       *aInfo);
+  } else {
+    Canonical()->ReplaceActiveSessionHistoryEntry(aInfo);
+  }
+}
+
+void BrowsingContext::RemoveDynEntriesFromActiveSessionHistoryEntry() {
+  if (XRE_IsContentProcess()) {
+    ContentChild::GetSingleton()
+        ->SendRemoveDynEntriesFromActiveSessionHistoryEntry(this);
+  } else {
+    Canonical()->RemoveDynEntriesFromActiveSessionHistoryEntry();
+  }
+}
+
+void BrowsingContext::RemoveFromSessionHistory(const nsID& aChangeID) {
+  if (XRE_IsContentProcess()) {
+    ContentChild::GetSingleton()->SendRemoveFromSessionHistory(this, aChangeID);
+  } else {
+    Canonical()->RemoveFromSessionHistory(aChangeID);
+  }
+}
+
+void BrowsingContext::HistoryGo(
+    int32_t aOffset, uint64_t aHistoryEpoch, bool aRequireUserInteraction,
+    bool aUserActivation, std::function<void(Maybe<int32_t>&&)>&& aResolver) {
+  if (XRE_IsContentProcess()) {
+    ContentChild::GetSingleton()->SendHistoryGo(
+        this, aOffset, aHistoryEpoch, aRequireUserInteraction, aUserActivation,
+        std::move(aResolver),
+        [](mozilla::ipc::
+               ResponseRejectReason) { /* FIXME Is ignoring this fine? */ });
+  } else {
+    RefPtr<CanonicalBrowsingContext> self = Canonical();
+    aResolver(self->HistoryGo(
+        aOffset, aHistoryEpoch, aRequireUserInteraction, aUserActivation,
+        Canonical()->GetContentParent()
+            ? Some(Canonical()->GetContentParent()->ChildID())
+            : Nothing()));
+  }
+}
+
+void BrowsingContext::SetChildSHistory(ChildSHistory* aChildSHistory) {
+  mChildSessionHistory = aChildSHistory;
+  mChildSessionHistory->SetBrowsingContext(this);
+  mFields.SetWithoutSyncing<IDX_HasSessionHistory>(true);
+}
+
+bool BrowsingContext::ShouldUpdateSessionHistory(uint32_t aLoadType) {
+  // We don't update session history on reload unless we're loading
+  // an iframe in shift-reload case.
+  return nsDocShell::ShouldUpdateGlobalHistory(aLoadType) &&
+         (!(aLoadType & nsIDocShell::LOAD_CMD_RELOAD) ||
+          (IsForceReloadType(aLoadType) && IsSubframe()));
+}
+
+nsresult BrowsingContext::CheckLocationChangeRateLimit(CallerType aCallerType) {
+  // We only rate limit non system callers
+  if (aCallerType == CallerType::System) {
+    return NS_OK;
+  }
+
+  // Fetch rate limiting preferences
+  uint32_t limitCount =
+      StaticPrefs::dom_navigation_locationChangeRateLimit_count();
+  uint32_t timeSpanSeconds =
+      StaticPrefs::dom_navigation_locationChangeRateLimit_timespan();
+
+  // Disable throttling if either of the preferences is set to 0.
+  if (limitCount == 0 || timeSpanSeconds == 0) {
+    return NS_OK;
+  }
+
+  TimeDuration throttleSpan = TimeDuration::FromSeconds(timeSpanSeconds);
+
+  if (mLocationChangeRateLimitSpanStart.IsNull() ||
+      ((TimeStamp::Now() - mLocationChangeRateLimitSpanStart) > throttleSpan)) {
+    // Initial call or timespan exceeded, reset counter and timespan.
+    mLocationChangeRateLimitSpanStart = TimeStamp::Now();
+    mLocationChangeRateLimitCount = 1;
+    return NS_OK;
+  }
+
+  if (mLocationChangeRateLimitCount >= limitCount) {
+    // Rate limit reached
+
+    Document* doc = GetDocument();
+    if (doc) {
+      nsContentUtils::ReportToConsole(nsIScriptError::errorFlag, "DOM"_ns, doc,
+                                      nsContentUtils::eDOM_PROPERTIES,
+                                      "LocChangeFloodingPrevented");
+    }
+
+    return NS_ERROR_DOM_SECURITY_ERR;
+  }
+
+  mLocationChangeRateLimitCount++;
+  return NS_OK;
+}
+
+void BrowsingContext::ResetLocationChangeRateLimit() {
+  // Resetting the timestamp object will cause the check function to
+  // init again and reset the rate limit.
+  mLocationChangeRateLimitSpanStart = TimeStamp();
+}
+
+void BrowsingContext::LocationCreated(dom::Location* aLocation) {
+  MOZ_ASSERT(!aLocation->isInList());
+  mLocations.insertBack(aLocation);
+}
+
+void BrowsingContext::ClearCachedValuesOfLocations() {
+  for (dom::Location* loc = mLocations.getFirst(); loc; loc = loc->getNext()) {
+    loc->ClearCachedValues();
+  }
+}
+
+}  // namespace dom
+
+namespace ipc {
+
+void IPDLParamTraits<dom::MaybeDiscarded<dom::BrowsingContext>>::Write(
+    IPC::MessageWriter* aWriter, IProtocol* aActor,
+    const dom::MaybeDiscarded<dom::BrowsingContext>& aParam) {
+  MOZ_DIAGNOSTIC_ASSERT(!aParam.GetMaybeDiscarded() ||
+                        aParam.GetMaybeDiscarded()->EverAttached());
+  uint64_t id = aParam.ContextId();
+  WriteIPDLParam(aWriter, aActor, id);
+}
+
+bool IPDLParamTraits<dom::MaybeDiscarded<dom::BrowsingContext>>::Read(
+    IPC::MessageReader* aReader, IProtocol* aActor,
+    dom::MaybeDiscarded<dom::BrowsingContext>* aResult) {
+  uint64_t id = 0;
+  if (!ReadIPDLParam(aReader, aActor, &id)) {
+    return false;
+  }
+
+  if (id == 0) {
+    *aResult = nullptr;
+  } else if (RefPtr<dom::BrowsingContext> bc = dom::BrowsingContext::Get(id)) {
+    *aResult = std::move(bc);
+  } else {
+    aResult->SetDiscarded(id);
+  }
+  return true;
+}
+
+void IPDLParamTraits<dom::BrowsingContext::IPCInitializer>::Write(
+    IPC::MessageWriter* aWriter, IProtocol* aActor,
+    const dom::BrowsingContext::IPCInitializer& aInit) {
+  // Write actor ID parameters.
+  WriteIPDLParam(aWriter, aActor, aInit.mId);
+  WriteIPDLParam(aWriter, aActor, aInit.mParentId);
+  WriteIPDLParam(aWriter, aActor, aInit.mWindowless);
+  WriteIPDLParam(aWriter, aActor, aInit.mUseRemoteTabs);
+  WriteIPDLParam(aWriter, aActor, aInit.mUseRemoteSubframes);
+  WriteIPDLParam(aWriter, aActor, aInit.mCreatedDynamically);
+  WriteIPDLParam(aWriter, aActor, aInit.mChildOffset);
+  WriteIPDLParam(aWriter, aActor, aInit.mOriginAttributes);
+  WriteIPDLParam(aWriter, aActor, aInit.mRequestContextId);
+  WriteIPDLParam(aWriter, aActor, aInit.mSessionHistoryIndex);
+  WriteIPDLParam(aWriter, aActor, aInit.mSessionHistoryCount);
+  WriteIPDLParam(aWriter, aActor, aInit.mFields);
+}
+
+bool IPDLParamTraits<dom::BrowsingContext::IPCInitializer>::Read(
+    IPC::MessageReader* aReader, IProtocol* aActor,
+    dom::BrowsingContext::IPCInitializer* aInit) {
+  // Read actor ID parameters.
+  if (!ReadIPDLParam(aReader, aActor, &aInit->mId) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mParentId) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mWindowless) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mUseRemoteTabs) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mUseRemoteSubframes) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mCreatedDynamically) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mChildOffset) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mOriginAttributes) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mRequestContextId) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mSessionHistoryIndex) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mSessionHistoryCount) ||
+      !ReadIPDLParam(aReader, aActor, &aInit->mFields)) {
+    return false;
+  }
+  return true;
+}
+
+template struct IPDLParamTraits<dom::BrowsingContext::BaseTransaction>;
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/docshell/base/BrowsingContext.h b/docshell/base/BrowsingContext.h
new file mode 100644
index 0000000000..5ec95a61e4
--- /dev/null
+++ b/docshell/base/BrowsingContext.h
@@ -0,0 +1,1469 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BrowsingContext_h
+#define mozilla_dom_BrowsingContext_h
+
+#include <tuple>
+#include "GVAutoplayRequestUtils.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/HalScreenConfiguration.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Span.h"
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/LocationBase.h"
+#include "mozilla/dom/MaybeDiscarded.h"
+#include "mozilla/dom/PopupBlocker.h"
+#include "mozilla/dom/UserActivation.h"
+#include "mozilla/dom/BrowsingContextBinding.h"
+#include "mozilla/dom/ScreenOrientationBinding.h"
+#include "mozilla/dom/SyncedContext.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsIDocShell.h"
+#include "nsTArray.h"
+#include "nsWrapperCache.h"
+#include "nsILoadInfo.h"
+#include "nsILoadContext.h"
+#include "nsThreadUtils.h"
+
+class nsDocShellLoadState;
+class nsGlobalWindowInner;
+class nsGlobalWindowOuter;
+class nsIPrincipal;
+class nsOuterWindowProxy;
+struct nsPoint;
+class PickleIterator;
+
+namespace IPC {
+class Message;
+class MessageReader;
+class MessageWriter;
+}  // namespace IPC
+
+namespace mozilla {
+
+class ErrorResult;
+class LogModule;
+
+namespace ipc {
+class IProtocol;
+class IPCResult;
+
+template <typename T>
+struct IPDLParamTraits;
+}  // namespace ipc
+
+namespace dom {
+class BrowsingContent;
+class BrowsingContextGroup;
+class CanonicalBrowsingContext;
+class ChildSHistory;
+class ContentParent;
+class Element;
+struct LoadingSessionHistoryInfo;
+class Location;
+template <typename>
+struct Nullable;
+template <typename T>
+class Sequence;
+class SessionHistoryInfo;
+class SessionStorageManager;
+class StructuredCloneHolder;
+class WindowContext;
+class WindowGlobalChild;
+struct WindowPostMessageOptions;
+class WindowProxyHolder;
+
+enum class ExplicitActiveStatus : uint8_t {
+  None,
+  Active,
+  Inactive,
+  EndGuard_,
+};
+
+struct EmbedderColorSchemes {
+  PrefersColorSchemeOverride mUsed{};
+  PrefersColorSchemeOverride mPreferred{};
+
+  bool operator==(const EmbedderColorSchemes& aOther) const {
+    return mUsed == aOther.mUsed && mPreferred == aOther.mPreferred;
+  }
+
+  bool operator!=(const EmbedderColorSchemes& aOther) const {
+    return !(*this == aOther);
+  }
+};
+
+// Fields are, by default, settable by any process and readable by any process.
+// Racy sets will be resolved as-if they occurred in the order the parent
+// process finds out about them.
+//
+// The `DidSet` and `CanSet` methods may be overloaded to provide different
+// behavior for a specific field.
+//  * `DidSet` is called to run code in every process whenever the value is
+//    updated (This currently occurs even if the value didn't change, though
+//    this may change in the future).
+//  * `CanSet` is called before attempting to set the value, in both the process
+//    which calls `Set`, and the parent process, and will kill the misbehaving
+//    process if it fails.
+#define MOZ_EACH_BC_FIELD(FIELD)                                              \
+  FIELD(Name, nsString)                                                       \
+  FIELD(Closed, bool)                                                         \
+  FIELD(ExplicitActive, ExplicitActiveStatus)                                 \
+  /* Top()-only. If true, new-playing media will be suspended when in an      \
+   * inactive browsing context. */                                            \
+  FIELD(SuspendMediaWhenInactive, bool)                                       \
+  /* If true, we're within the nested event loop in window.open, and this     \
+   * context may not be used as the target of a load */                       \
+  FIELD(PendingInitialization, bool)                                          \
+  /* Indicates if the browser window is active for the purpose of the         \
+   * :-moz-window-inactive pseudoclass. Only read from or set on the          \
+   * top BrowsingContext. */                                                  \
+  FIELD(IsActiveBrowserWindowInternal, bool)                                  \
+  FIELD(OpenerPolicy, nsILoadInfo::CrossOriginOpenerPolicy)                   \
+  /* Current opener for the BrowsingContext. Weak reference */                \
+  FIELD(OpenerId, uint64_t)                                                   \
+  FIELD(OnePermittedSandboxedNavigatorId, uint64_t)                           \
+  /* WindowID of the inner window which embeds this BC */                     \
+  FIELD(EmbedderInnerWindowId, uint64_t)                                      \
+  FIELD(CurrentInnerWindowId, uint64_t)                                       \
+  FIELD(HadOriginalOpener, bool)                                              \
+  FIELD(IsPopupSpam, bool)                                                    \
+  /* Hold the audio muted state and should be used on top level browsing      \
+   * contexts only */                                                         \
+  FIELD(Muted, bool)                                                          \
+  /* Hold the pinned/app-tab state and should be used on top level browsing   \
+   * contexts only */                                                         \
+  FIELD(IsAppTab, bool)                                                       \
+  /* Whether there's more than 1 tab / toplevel browsing context in this      \
+   * parent window. Used to determine if a given BC is allowed to resize      \
+   * and/or move the window or not. */                                        \
+  FIELD(HasSiblings, bool)                                                    \
+  /* Indicate that whether we should delay media playback, which would only   \
+     be done on an unvisited tab. And this should only be used on the top     \
+     level browsing contexts */                                               \
+  FIELD(ShouldDelayMediaFromStart, bool)                                      \
+  /* See nsSandboxFlags.h for the possible flags. */                          \
+  FIELD(SandboxFlags, uint32_t)                                               \
+  /* The value of SandboxFlags when the BrowsingContext is first created.     \
+   * Used for sandboxing the initial about:blank document. */                 \
+  FIELD(InitialSandboxFlags, uint32_t)                                        \
+  /* A non-zero unique identifier for the browser element that is hosting     \
+   * this                                                                     \
+   * BrowsingContext tree. Every BrowsingContext in the element's tree will   \
+   * return the same ID in all processes and it will remain stable            \
+   * regardless of process changes. When a browser element's frameloader is   \
+   * switched to another browser element this ID will remain the same but     \
+   * hosted under the under the new browser element. */                       \
+  FIELD(BrowserId, uint64_t)                                                  \
+  FIELD(HistoryID, nsID)                                                      \
+  FIELD(InRDMPane, bool)                                                      \
+  FIELD(Loading, bool)                                                        \
+  /* A field only set on top browsing contexts, which indicates that either:  \
+   *                                                                          \
+   *  * This is a browsing context created explicitly for printing or print   \
+   *    preview (thus hosting static documents).                              \
+   *                                                                          \
+   *  * This is a browsing context where something in this tree is calling    \
+   *    window.print() (and thus showing a modal dialog).                     \
+   *                                                                          \
+   * We use it exclusively to block navigation for both of these cases. */    \
+  FIELD(IsPrinting, bool)                                                     \
+  FIELD(AncestorLoading, bool)                                                \
+  FIELD(AllowContentRetargeting, bool)                                        \
+  FIELD(AllowContentRetargetingOnChildren, bool)                              \
+  FIELD(ForceEnableTrackingProtection, bool)                                  \
+  FIELD(UseGlobalHistory, bool)                                               \
+  FIELD(TargetTopLevelLinkClicksToBlankInternal, bool)                        \
+  FIELD(FullscreenAllowedByOwner, bool)                                       \
+  FIELD(ForceDesktopViewport, bool)                                           \
+  /*                                                                          \
+   * "is popup" in the spec.                                                  \
+   * Set only on top browsing contexts.                                       \
+   * This doesn't indicate whether this is actually a popup or not,           \
+   * but whether this browsing context is created by requesting popup or not. \
+   * See also: nsWindowWatcher::ShouldOpenPopup.                              \
+   */                                                                         \
+  FIELD(IsPopupRequested, bool)                                               \
+  /* These field are used to store the states of autoplay media request on    \
+   * GeckoView only, and it would only be modified on the top level browsing  \
+   * context. */                                                              \
+  FIELD(GVAudibleAutoplayRequestStatus, GVAutoplayRequestStatus)              \
+  FIELD(GVInaudibleAutoplayRequestStatus, GVAutoplayRequestStatus)            \
+  /* ScreenOrientation-related APIs */                                        \
+  FIELD(CurrentOrientationAngle, float)                                       \
+  FIELD(CurrentOrientationType, mozilla::dom::OrientationType)                \
+  FIELD(OrientationLock, mozilla::hal::ScreenOrientation)                     \
+  FIELD(UserAgentOverride, nsString)                                          \
+  FIELD(TouchEventsOverrideInternal, mozilla::dom::TouchEventsOverride)       \
+  FIELD(EmbedderElementType, Maybe<nsString>)                                 \
+  FIELD(MessageManagerGroup, nsString)                                        \
+  FIELD(MaxTouchPointsOverride, uint8_t)                                      \
+  FIELD(FullZoom, float)                                                      \
+  FIELD(WatchedByDevToolsInternal, bool)                                      \
+  FIELD(TextZoom, float)                                                      \
+  FIELD(OverrideDPPX, float)                                                  \
+  /* The current in-progress load. */                                         \
+  FIELD(CurrentLoadIdentifier, Maybe<uint64_t>)                               \
+  /* See nsIRequest for possible flags. */                                    \
+  FIELD(DefaultLoadFlags, uint32_t)                                           \
+  /* Signals that session history is enabled for this browsing context tree.  \
+   * This is only ever set to true on the top BC, so consumers need to get    \
+   * the value from the top BC! */                                            \
+  FIELD(HasSessionHistory, bool)                                              \
+  /* Tracks if this context is the only top-level document in the session     \
+   * history of the context. */                                               \
+  FIELD(IsSingleToplevelInHistory, bool)                                      \
+  FIELD(UseErrorPages, bool)                                                  \
+  FIELD(PlatformOverride, nsString)                                           \
+  /* Specifies if this BC has loaded documents besides the initial            \
+   * about:blank document. about:privatebrowsing, about:home, about:newtab    \
+   * and non-initial about:blank are not considered to be initial             \
+   * documents. */                                                            \
+  FIELD(HasLoadedNonInitialDocument, bool)                                    \
+  /* Default value for nsIDocumentViewer::authorStyleDisabled in any new      \
+   * browsing contexts created as a descendant of this one.  Valid only for   \
+   * top BCs. */                                                              \
+  FIELD(AuthorStyleDisabledDefault, bool)                                     \
+  FIELD(ServiceWorkersTestingEnabled, bool)                                   \
+  FIELD(MediumOverride, nsString)                                             \
+  /* DevTools override for prefers-color-scheme */                            \
+  FIELD(PrefersColorSchemeOverride, dom::PrefersColorSchemeOverride)          \
+  /* prefers-color-scheme override based on the color-scheme style of our     \
+   * <browser> embedder element. */                                           \
+  FIELD(EmbedderColorSchemes, EmbedderColorSchemes)                           \
+  FIELD(DisplayMode, dom::DisplayMode)                                        \
+  /* The number of entries added to the session history because of this       \
+   * browsing context. */                                                     \
+  FIELD(HistoryEntryCount, uint32_t)                                          \
+  /* Don't use the getter of the field, but IsInBFCache() method */           \
+  FIELD(IsInBFCache, bool)                                                    \
+  FIELD(HasRestoreData, bool)                                                 \
+  FIELD(SessionStoreEpoch, uint32_t)                                          \
+  /* Whether we can execute scripts in this BrowsingContext. Has no effect    \
+   * unless scripts are also allowed in the parent WindowContext. */          \
+  FIELD(AllowJavascript, bool)                                                \
+  /* The count of request that are used to prevent the browsing context tree  \
+   * from being suspended, which would ONLY be modified on the top level      \
+   * context in the chrome process because that's a non-atomic counter */     \
+  FIELD(PageAwakeRequestCount, uint32_t)                                      \
+  /* This field only gets incrememented when we start navigations in the      \
+   * parent process. This is used for keeping track of the racing navigations \
+   * between the parent and content processes. */                             \
+  FIELD(ParentInitiatedNavigationEpoch, uint64_t)                             \
+  /* This browsing context is for a synthetic image document wrapping an      \
+   * image embedded in <object> or <embed>. */                                \
+  FIELD(SyntheticDocumentContainer, bool)                                     \
+  /* If true, this document is embedded within a content document,  either    \
+   * loaded in the parent (e.g. about:addons or the devtools toolbox), or in  \
+   * a content process. */                                                    \
+  FIELD(EmbeddedInContentDocument, bool)                                      \
+  /* If true, this browsing context is within a hidden embedded document. */  \
+  FIELD(IsUnderHiddenEmbedderElement, bool)                                   \
+  /* If true, this browsing context is offline */                             \
+  FIELD(ForceOffline, bool)
+
+// BrowsingContext, in this context, is the cross process replicated
+// environment in which information about documents is stored. In
+// particular the tree structure of nested browsing contexts is
+// represented by the tree of BrowsingContexts.
+//
+// The tree of BrowsingContexts is created in step with its
+// corresponding nsDocShell, and when nsDocShells are connected
+// through a parent/child relationship, so are BrowsingContexts. The
+// major difference is that BrowsingContexts are replicated (synced)
+// to the parent process, making it possible to traverse the
+// BrowsingContext tree for a tab, in both the parent and the child
+// process.
+//
+// Trees of BrowsingContexts should only ever contain nodes of the
+// same BrowsingContext::Type. This is enforced by asserts in the
+// BrowsingContext::Create* methods.
+class BrowsingContext : public nsILoadContext, public nsWrapperCache {
+  MOZ_DECL_SYNCED_CONTEXT(BrowsingContext, MOZ_EACH_BC_FIELD)
+
+ public:
+  enum class Type { Chrome, Content };
+
+  static void Init();
+  static LogModule* GetLog();
+  static LogModule* GetSyncLog();
+
+  // Look up a BrowsingContext in the current process by ID.
+  static already_AddRefed<BrowsingContext> Get(uint64_t aId);
+  static already_AddRefed<BrowsingContext> Get(GlobalObject&, uint64_t aId) {
+    return Get(aId);
+  }
+  // Look up the top-level BrowsingContext by BrowserID.
+  static already_AddRefed<BrowsingContext> GetCurrentTopByBrowserId(
+      uint64_t aBrowserId);
+  static already_AddRefed<BrowsingContext> GetCurrentTopByBrowserId(
+      GlobalObject&, uint64_t aId) {
+    return GetCurrentTopByBrowserId(aId);
+  }
+
+  static void UpdateCurrentTopByBrowserId(BrowsingContext* aNewBrowsingContext);
+
+  static already_AddRefed<BrowsingContext> GetFromWindow(
+      WindowProxyHolder& aProxy);
+  static already_AddRefed<BrowsingContext> GetFromWindow(
+      GlobalObject&, WindowProxyHolder& aProxy) {
+    return GetFromWindow(aProxy);
+  }
+
+  static void DiscardFromContentParent(ContentParent* aCP);
+
+  // Create a brand-new toplevel BrowsingContext with no relationships to other
+  // BrowsingContexts, and which is not embedded within any <browser> or frame
+  // element.
+  //
+  // This BrowsingContext is immediately attached, and cannot have LoadContext
+  // flags customized unless it is of `Type::Chrome`.
+  //
+  // The process which created this BrowsingContext is responsible for detaching
+  // it.
+  static already_AddRefed<BrowsingContext> CreateIndependent(Type aType);
+
+  // Create a brand-new BrowsingContext object, but does not immediately attach
+  // it. State such as OriginAttributes and PrivateBrowsingId may be customized
+  // to configure the BrowsingContext before it is attached.
+  //
+  // `EnsureAttached()` must be called before the BrowsingContext is used for a
+  // DocShell, BrowserParent, or BrowserBridgeChild.
+  static already_AddRefed<BrowsingContext> CreateDetached(
+      nsGlobalWindowInner* aParent, BrowsingContext* aOpener,
+      BrowsingContextGroup* aSpecificGroup, const nsAString& aName, Type aType,
+      bool aIsPopupRequested, bool aCreatedDynamically = false);
+
+  void EnsureAttached();
+
+  bool EverAttached() const { return mEverAttached; }
+
+  // Cast this object to a canonical browsing context, and return it.
+  CanonicalBrowsingContext* Canonical();
+
+  // Is the most recent Document in this BrowsingContext loaded within this
+  // process? This may be true with a null mDocShell after the Window has been
+  // closed.
+  bool IsInProcess() const { return mIsInProcess; }
+
+  bool IsOwnedByProcess() const;
+
+  bool CanHaveRemoteOuterProxies() const {
+    return !mIsInProcess || mDanglingRemoteOuterProxies;
+  }
+
+  // Has this BrowsingContext been discarded. A discarded browsing context has
+  // been destroyed, and may not be available on the other side of an IPC
+  // message.
+  bool IsDiscarded() const { return mIsDiscarded; }
+
+  // Returns true if none of the BrowsingContext's ancestor BrowsingContexts or
+  // WindowContexts are discarded or cached.
+  bool AncestorsAreCurrent() const;
+
+  bool Windowless() const { return mWindowless; }
+
+  // Get the DocShell for this BrowsingContext if it is in-process, or
+  // null if it's not.
+  nsIDocShell* GetDocShell() const { return mDocShell; }
+  void SetDocShell(nsIDocShell* aDocShell);
+  void ClearDocShell() { mDocShell = nullptr; }
+
+  // Get the Document for this BrowsingContext if it is in-process, or
+  // null if it's not.
+  Document* GetDocument() const {
+    return mDocShell ? mDocShell->GetDocument() : nullptr;
+  }
+  Document* GetExtantDocument() const {
+    return mDocShell ? mDocShell->GetExtantDocument() : nullptr;
+  }
+
+  // This cleans up remote outer window proxies that might have been left behind
+  // when the browsing context went from being remote to local. It does this by
+  // turning them into cross-compartment wrappers to aOuter. If there is already
+  // a remote proxy in the compartment of aOuter, then aOuter will get swapped
+  // to it and the value of aOuter will be set to the object that used to be the
+  // remote proxy and is now an OuterWindowProxy.
+  void CleanUpDanglingRemoteOuterWindowProxies(
+      JSContext* aCx, JS::MutableHandle<JSObject*> aOuter);
+
+  // Get the embedder element for this BrowsingContext if the embedder is
+  // in-process, or null if it's not.
+  Element* GetEmbedderElement() const { return mEmbedderElement; }
+  void SetEmbedderElement(Element* aEmbedder);
+
+  // Return true if the type of the embedder element is either object
+  // or embed, false otherwise.
+  bool IsEmbedderTypeObjectOrEmbed();
+
+  // Called after the BrowingContext has been embedded in a FrameLoader. This
+  // happens after `SetEmbedderElement` is called on the BrowsingContext and
+  // after the BrowsingContext has been set on the FrameLoader.
+  void Embed();
+
+  // Get the outer window object for this BrowsingContext if it is in-process
+  // and still has a docshell, or null otherwise.
+  nsPIDOMWindowOuter* GetDOMWindow() const {
+    return mDocShell ? mDocShell->GetWindow() : nullptr;
+  }
+
+  uint64_t GetRequestContextId() const { return mRequestContextId; }
+
+  // Detach the current BrowsingContext from its parent, in both the
+  // child and the parent process.
+  void Detach(bool aFromIPC = false);
+
+  // Prepare this BrowsingContext to leave the current process.
+  void PrepareForProcessChange();
+
+  // Triggers a load in the process which currently owns this BrowsingContext.
+  nsresult LoadURI(nsDocShellLoadState* aLoadState,
+                   bool aSetNavigating = false);
+
+  nsresult InternalLoad(nsDocShellLoadState* aLoadState);
+
+  // Removes the root document for this BrowsingContext tree from the BFCache,
+  // if it is cached, and returns true if it was.
+  bool RemoveRootFromBFCacheSync();
+
+  // If the load state includes a source BrowsingContext has been passed, check
+  // to see if we are sandboxed from it as the result of an iframe or CSP
+  // sandbox.
+  nsresult CheckSandboxFlags(nsDocShellLoadState* aLoadState);
+
+  void DisplayLoadError(const nsAString& aURI);
+
+  // Check that this browsing context is targetable for navigations (i.e. that
+  // it is neither closed, cached, nor discarded).
+  bool IsTargetable() const;
+
+  // True if this browsing context is inactive and is able to be suspended.
+  bool InactiveForSuspend() const;
+
+  const nsString& Name() const { return GetName(); }
+  void GetName(nsAString& aName) { aName = GetName(); }
+  bool NameEquals(const nsAString& aName) { return GetName().Equals(aName); }
+
+  Type GetType() const { return mType; }
+  bool IsContent() const { return mType == Type::Content; }
+  bool IsChrome() const { return !IsContent(); }
+
+  bool IsTop() const { return !GetParent(); }
+  bool IsSubframe() const { return !IsTop(); }
+
+  bool IsTopContent() const { return IsContent() && IsTop(); }
+
+  bool IsInSubtreeOf(BrowsingContext* aContext);
+
+  bool IsContentSubframe() const { return IsContent() && IsSubframe(); }
+
+  // non-zero
+  uint64_t Id() const { return mBrowsingContextId; }
+
+  BrowsingContext* GetParent() const;
+  BrowsingContext* Top();
+  const BrowsingContext* Top() const;
+
+  int32_t IndexOf(BrowsingContext* aChild);
+
+  // NOTE: Unlike `GetEmbedderWindowGlobal`, `GetParentWindowContext` does not
+  // cross toplevel content browser boundaries.
+  WindowContext* GetParentWindowContext() const { return mParentWindow; }
+  WindowContext* GetTopWindowContext() const;
+
+  already_AddRefed<BrowsingContext> GetOpener() const {
+    RefPtr<BrowsingContext> opener(Get(GetOpenerId()));
+    if (!mIsDiscarded && opener && !opener->mIsDiscarded) {
+      MOZ_DIAGNOSTIC_ASSERT(opener->mType == mType);
+      return opener.forget();
+    }
+    return nullptr;
+  }
+  void SetOpener(BrowsingContext* aOpener);
+  bool HasOpener() const;
+
+  bool HadOriginalOpener() const { return GetHadOriginalOpener(); }
+
+  // Returns true if the browsing context and top context are same origin
+  bool SameOriginWithTop();
+
+  /**
+   * When a new browsing context is opened by a sandboxed document, it needs to
+   * keep track of the browsing context that opened it, so that it can be
+   * navigated by it.  This is the "one permitted sandboxed navigator".
+   */
+  already_AddRefed<BrowsingContext> GetOnePermittedSandboxedNavigator() const {
+    return Get(GetOnePermittedSandboxedNavigatorId());
+  }
+  [[nodiscard]] nsresult SetOnePermittedSandboxedNavigator(
+      BrowsingContext* aNavigator) {
+    if (GetOnePermittedSandboxedNavigatorId()) {
+      MOZ_ASSERT(false,
+                 "One Permitted Sandboxed Navigator should only be set once.");
+      return NS_ERROR_FAILURE;
+    } else {
+      return SetOnePermittedSandboxedNavigatorId(aNavigator ? aNavigator->Id()
+                                                            : 0);
+    }
+  }
+
+  uint32_t SandboxFlags() const { return GetSandboxFlags(); }
+
+  Span<RefPtr<BrowsingContext>> Children() const;
+  void GetChildren(nsTArray<RefPtr<BrowsingContext>>& aChildren);
+
+  Span<RefPtr<BrowsingContext>> NonSyntheticChildren() const;
+
+  const nsTArray<RefPtr<WindowContext>>& GetWindowContexts() {
+    return mWindowContexts;
+  }
+  void GetWindowContexts(nsTArray<RefPtr<WindowContext>>& aWindows);
+
+  void RegisterWindowContext(WindowContext* aWindow);
+  void UnregisterWindowContext(WindowContext* aWindow);
+  WindowContext* GetCurrentWindowContext() const {
+    return mCurrentWindowContext;
+  }
+
+  // Helpers to traverse this BrowsingContext subtree. Note that these will only
+  // traverse active contexts, and will ignore ones in the BFCache.
+  enum class WalkFlag {
+    Next,
+    Skip,
+    Stop,
+  };
+
+  /**
+   * Walk the browsing context tree in pre-order and call `aCallback`
+   * for every node in the tree. PreOrderWalk accepts two types of
+   * callbacks, either of the type `void(BrowsingContext*)` or
+   * `WalkFlag(BrowsingContext*)`. The former traverses the entire
+   * tree, but the latter let's you control if a sub-tree should be
+   * skipped by returning `WalkFlag::Skip`, completely abort traversal
+   * by returning `WalkFlag::Stop` or continue as normal with
+   * `WalkFlag::Next`.
+   */
+  template <typename F>
+  void PreOrderWalk(F&& aCallback) {
+    if constexpr (std::is_void_v<
+                      typename std::invoke_result_t<F, BrowsingContext*>>) {
+      PreOrderWalkVoid(std::forward<F>(aCallback));
+    } else {
+      PreOrderWalkFlag(std::forward<F>(aCallback));
+    }
+  }
+
+  void PreOrderWalkVoid(const std::function<void(BrowsingContext*)>& aCallback);
+  WalkFlag PreOrderWalkFlag(
+      const std::function<WalkFlag(BrowsingContext*)>& aCallback);
+
+  void PostOrderWalk(const std::function<void(BrowsingContext*)>& aCallback);
+
+  void GetAllBrowsingContextsInSubtree(
+      nsTArray<RefPtr<BrowsingContext>>& aBrowsingContexts);
+
+  BrowsingContextGroup* Group() { return mGroup; }
+
+  // WebIDL bindings for nsILoadContext
+  Nullable<WindowProxyHolder> GetAssociatedWindow();
+  Nullable<WindowProxyHolder> GetTopWindow();
+  Element* GetTopFrameElement();
+  bool GetIsContent() { return IsContent(); }
+  void SetUsePrivateBrowsing(bool aUsePrivateBrowsing, ErrorResult& aError);
+  // Needs a different name to disambiguate from the xpidl method with
+  // the same signature but different return value.
+  void SetUseTrackingProtectionWebIDL(bool aUseTrackingProtection,
+                                      ErrorResult& aRv);
+  bool UseTrackingProtectionWebIDL() { return UseTrackingProtection(); }
+  void GetOriginAttributes(JSContext* aCx, JS::MutableHandle<JS::Value> aVal,
+                           ErrorResult& aError);
+
+  bool InRDMPane() const { return GetInRDMPane(); }
+
+  bool WatchedByDevTools();
+  void SetWatchedByDevTools(bool aWatchedByDevTools, ErrorResult& aRv);
+
+  dom::TouchEventsOverride TouchEventsOverride() const;
+  bool TargetTopLevelLinkClicksToBlank() const;
+
+  bool FullscreenAllowed() const;
+
+  float FullZoom() const { return GetFullZoom(); }
+  float TextZoom() const { return GetTextZoom(); }
+
+  float OverrideDPPX() const { return Top()->GetOverrideDPPX(); }
+
+  bool SuspendMediaWhenInactive() const {
+    return GetSuspendMediaWhenInactive();
+  }
+
+  bool IsActive() const;
+  bool ForceOffline() const { return GetForceOffline(); }
+
+  bool ForceDesktopViewport() const { return GetForceDesktopViewport(); }
+
+  bool AuthorStyleDisabledDefault() const {
+    return GetAuthorStyleDisabledDefault();
+  }
+
+  bool UseGlobalHistory() const { return GetUseGlobalHistory(); }
+
+  bool GetIsActiveBrowserWindow();
+
+  void SetIsActiveBrowserWindow(bool aActive);
+
+  uint64_t BrowserId() const { return GetBrowserId(); }
+
+  bool IsLoading();
+
+  void GetEmbedderElementType(nsString& aElementType) {
+    if (GetEmbedderElementType().isSome()) {
+      aElementType = GetEmbedderElementType().value();
+    }
+  }
+
+  bool IsLoadingIdentifier(uint64_t aLoadIdentifer) {
+    if (GetCurrentLoadIdentifier() &&
+        *GetCurrentLoadIdentifier() == aLoadIdentifer) {
+      return true;
+    }
+    return false;
+  }
+
+  // ScreenOrientation related APIs
+  [[nodiscard]] nsresult SetCurrentOrientation(OrientationType aType,
+                                               float aAngle) {
+    Transaction txn;
+    txn.SetCurrentOrientationType(aType);
+    txn.SetCurrentOrientationAngle(aAngle);
+    return txn.Commit(this);
+  }
+
+  void SetRDMPaneOrientation(OrientationType aType, float aAngle,
+                             ErrorResult& aRv) {
+    if (InRDMPane()) {
+      if (NS_FAILED(SetCurrentOrientation(aType, aAngle))) {
+        aRv.ThrowInvalidStateError("Browsing context is discarded");
+      }
+    }
+  }
+
+  void SetRDMPaneMaxTouchPoints(uint8_t aMaxTouchPoints, ErrorResult& aRv) {
+    if (InRDMPane()) {
+      SetMaxTouchPointsOverride(aMaxTouchPoints, aRv);
+    }
+  }
+
+  // Find a browsing context in this context's list of
+  // children. Doesn't consider the special names, '_self', '_parent',
+  // '_top', or '_blank'. Performs access control checks with regard to
+  // 'this'.
+  BrowsingContext* FindChildWithName(const nsAString& aName,
+                                     WindowGlobalChild& aRequestingWindow);
+
+  // Find a browsing context in the subtree rooted at 'this' Doesn't
+  // consider the special names, '_self', '_parent', '_top', or
+  // '_blank'.
+  //
+  // If passed, performs access control checks with regard to
+  // 'aRequestingContext', otherwise performs no access checks.
+  BrowsingContext* FindWithNameInSubtree(const nsAString& aName,
+                                         WindowGlobalChild* aRequestingWindow);
+
+  // Find the special browsing context if aName is '_self', '_parent',
+  // '_top', but not '_blank'. The latter is handled in FindWithName
+  BrowsingContext* FindWithSpecialName(const nsAString& aName,
+                                       WindowGlobalChild& aRequestingWindow);
+
+  nsISupports* GetParentObject() const;
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  // Return the window proxy object that corresponds to this browsing context.
+  inline JSObject* GetWindowProxy() const { return mWindowProxy; }
+  inline JSObject* GetUnbarrieredWindowProxy() const {
+    return mWindowProxy.unbarrieredGet();
+  }
+
+  // Set the window proxy object that corresponds to this browsing context.
+  void SetWindowProxy(JS::Handle<JSObject*> aWindowProxy) {
+    mWindowProxy = aWindowProxy;
+  }
+
+  Nullable<WindowProxyHolder> GetWindow();
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SKIPPABLE_SCRIPT_HOLDER_CLASS(BrowsingContext)
+  NS_DECL_NSILOADCONTEXT
+
+  // Window APIs that are cross-origin-accessible (from the HTML spec).
+  WindowProxyHolder Window();
+  BrowsingContext* GetBrowsingContext() { return this; };
+  BrowsingContext* Self() { return this; }
+  void Location(JSContext* aCx, JS::MutableHandle<JSObject*> aLocation,
+                ErrorResult& aError);
+  void Close(CallerType aCallerType, ErrorResult& aError);
+  bool GetClosed(ErrorResult&) { return GetClosed(); }
+  void Focus(CallerType aCallerType, ErrorResult& aError);
+  void Blur(CallerType aCallerType, ErrorResult& aError);
+  WindowProxyHolder GetFrames(ErrorResult& aError);
+  int32_t Length() const { return Children().Length(); }
+  Nullable<WindowProxyHolder> GetTop(ErrorResult& aError);
+  void GetOpener(JSContext* aCx, JS::MutableHandle<JS::Value> aOpener,
+                 ErrorResult& aError) const;
+  Nullable<WindowProxyHolder> GetParent(ErrorResult& aError);
+  void PostMessageMoz(JSContext* aCx, JS::Handle<JS::Value> aMessage,
+                      const nsAString& aTargetOrigin,
+                      const Sequence<JSObject*>& aTransfer,
+                      nsIPrincipal& aSubjectPrincipal, ErrorResult& aError);
+  void PostMessageMoz(JSContext* aCx, JS::Handle<JS::Value> aMessage,
+                      const WindowPostMessageOptions& aOptions,
+                      nsIPrincipal& aSubjectPrincipal, ErrorResult& aError);
+
+  void GetCustomUserAgent(nsAString& aUserAgent) {
+    aUserAgent = Top()->GetUserAgentOverride();
+  }
+  nsresult SetCustomUserAgent(const nsAString& aUserAgent);
+  void SetCustomUserAgent(const nsAString& aUserAgent, ErrorResult& aRv);
+
+  void GetCustomPlatform(nsAString& aPlatform) {
+    aPlatform = Top()->GetPlatformOverride();
+  }
+  void SetCustomPlatform(const nsAString& aPlatform, ErrorResult& aRv);
+
+  JSObject* WrapObject(JSContext* aCx);
+
+  static JSObject* ReadStructuredClone(JSContext* aCx,
+                                       JSStructuredCloneReader* aReader,
+                                       StructuredCloneHolder* aHolder);
+  bool WriteStructuredClone(JSContext* aCx, JSStructuredCloneWriter* aWriter,
+                            StructuredCloneHolder* aHolder);
+
+  void StartDelayedAutoplayMediaComponents();
+
+  [[nodiscard]] nsresult ResetGVAutoplayRequestStatus();
+
+  /**
+   * Information required to initialize a BrowsingContext in another process.
+   * This object may be serialized over IPC.
+   */
+  struct IPCInitializer {
+    uint64_t mId = 0;
+
+    // IDs are used for Parent and Opener to allow for this object to be
+    // deserialized before other BrowsingContext in the BrowsingContextGroup
+    // have been initialized.
+    uint64_t mParentId = 0;
+    already_AddRefed<WindowContext> GetParent();
+    already_AddRefed<BrowsingContext> GetOpener();
+
+    uint64_t GetOpenerId() const { return mFields.Get<IDX_OpenerId>(); }
+
+    bool mWindowless = false;
+    bool mUseRemoteTabs = false;
+    bool mUseRemoteSubframes = false;
+    bool mCreatedDynamically = false;
+    int32_t mChildOffset = 0;
+    int32_t mSessionHistoryIndex = -1;
+    int32_t mSessionHistoryCount = 0;
+    OriginAttributes mOriginAttributes;
+    uint64_t mRequestContextId = 0;
+
+    FieldValues mFields;
+  };
+
+  // Create an IPCInitializer object for this BrowsingContext.
+  IPCInitializer GetIPCInitializer();
+
+  // Create a BrowsingContext object from over IPC.
+  static mozilla::ipc::IPCResult CreateFromIPC(IPCInitializer&& aInitializer,
+                                               BrowsingContextGroup* aGroup,
+                                               ContentParent* aOriginProcess);
+
+  bool IsSandboxedFrom(BrowsingContext* aTarget);
+
+  // The runnable will be called once there is idle time, or the top level
+  // page has been loaded or if a timeout has fired.
+  // Must be called only on the top level BrowsingContext.
+  void AddDeprioritizedLoadRunner(nsIRunnable* aRunner);
+
+  RefPtr<SessionStorageManager> GetSessionStorageManager();
+
+  // Set PendingInitialization on this BrowsingContext before the context has
+  // been attached.
+  void InitPendingInitialization(bool aPendingInitialization) {
+    MOZ_ASSERT(!EverAttached());
+    mFields.SetWithoutSyncing<IDX_PendingInitialization>(
+        aPendingInitialization);
+  }
+
+  bool CreatedDynamically() const { return mCreatedDynamically; }
+
+  // Returns true if this browsing context, or any ancestor to this browsing
+  // context was created dynamically. See also `CreatedDynamically`.
+  bool IsDynamic() const;
+
+  int32_t ChildOffset() const { return mChildOffset; }
+
+  bool GetOffsetPath(nsTArray<uint32_t>& aPath) const;
+
+  const OriginAttributes& OriginAttributesRef() { return mOriginAttributes; }
+  nsresult SetOriginAttributes(const OriginAttributes& aAttrs);
+
+  void GetHistoryID(JSContext* aCx, JS::MutableHandle<JS::Value> aVal,
+                    ErrorResult& aError);
+
+  // This should only be called on the top browsing context.
+  void InitSessionHistory();
+
+  // This will only ever return a non-null value if called on the top browsing
+  // context.
+  ChildSHistory* GetChildSessionHistory();
+
+  bool CrossOriginIsolated();
+
+  // Check if it is allowed to open a popup from the current browsing
+  // context or any of its ancestors.
+  bool IsPopupAllowed();
+
+  // aCurrentURI is only required to be non-null if the load type contains the
+  // nsIWebNavigation::LOAD_FLAGS_IS_REFRESH flag and aInfo is for a refresh to
+  // the current URI.
+  void SessionHistoryCommit(const LoadingSessionHistoryInfo& aInfo,
+                            uint32_t aLoadType, nsIURI* aCurrentURI,
+                            SessionHistoryInfo* aPreviousActiveEntry,
+                            bool aPersist, bool aCloneEntryChildren,
+                            bool aChannelExpired, uint32_t aCacheKey);
+
+  // Set a new active entry on this browsing context. This is used for
+  // implementing history.pushState/replaceState and same document navigations.
+  // The new active entry will be linked to the current active entry through
+  // its shared state.
+  // aPreviousScrollPos is the scroll position that needs to be saved on the
+  // previous active entry.
+  // aUpdatedCacheKey is the cache key to set on the new active entry. If
+  // aUpdatedCacheKey is 0 then it will be ignored.
+  void SetActiveSessionHistoryEntry(const Maybe<nsPoint>& aPreviousScrollPos,
+                                    SessionHistoryInfo* aInfo,
+                                    uint32_t aLoadType,
+                                    uint32_t aUpdatedCacheKey,
+                                    bool aUpdateLength = true);
+
+  // Replace the active entry for this browsing context. This is used for
+  // implementing history.replaceState and same document navigations.
+  void ReplaceActiveSessionHistoryEntry(SessionHistoryInfo* aInfo);
+
+  // Removes dynamic child entries of the active entry.
+  void RemoveDynEntriesFromActiveSessionHistoryEntry();
+
+  // Removes entries corresponding to this BrowsingContext from session history.
+  void RemoveFromSessionHistory(const nsID& aChangeID);
+
+  void SetTriggeringAndInheritPrincipals(nsIPrincipal* aTriggeringPrincipal,
+                                         nsIPrincipal* aPrincipalToInherit,
+                                         uint64_t aLoadIdentifier);
+
+  // Return mTriggeringPrincipal and mPrincipalToInherit if the load id
+  // saved with the principal matches the current load identifier of this BC.
+  std::tuple<nsCOMPtr<nsIPrincipal>, nsCOMPtr<nsIPrincipal>>
+  GetTriggeringAndInheritPrincipalsForCurrentLoad();
+
+  void HistoryGo(int32_t aOffset, uint64_t aHistoryEpoch,
+                 bool aRequireUserInteraction, bool aUserActivation,
+                 std::function<void(Maybe<int32_t>&&)>&& aResolver);
+
+  bool ShouldUpdateSessionHistory(uint32_t aLoadType);
+
+  // Checks if we reached the rate limit for calls to Location and History API.
+  // The rate limit is controlled by the
+  // "dom.navigation.locationChangeRateLimit" prefs.
+  // Rate limit applies per BrowsingContext.
+  // Returns NS_OK if we are below the rate limit and increments the counter.
+  // Returns NS_ERROR_DOM_SECURITY_ERR if limit is reached.
+  nsresult CheckLocationChangeRateLimit(CallerType aCallerType);
+
+  void ResetLocationChangeRateLimit();
+
+  mozilla::dom::DisplayMode DisplayMode() { return Top()->GetDisplayMode(); }
+
+  // Returns canFocus, isActive
+  std::tuple<bool, bool> CanFocusCheck(CallerType aCallerType);
+
+  bool CanBlurCheck(CallerType aCallerType);
+
+  // Examine the current document state to see if we're in a way that is
+  // typically abused by web designers. The window.open code uses this
+  // routine to determine whether to allow the new window.
+  // Returns a value from the PopupControlState enum.
+  PopupBlocker::PopupControlState RevisePopupAbuseLevel(
+      PopupBlocker::PopupControlState aControl);
+
+  // Get the modifiers associated with the user activation for relevant
+  // documents. The window.open code uses this routine to determine where the
+  // new window should be located.
+  void GetUserActivationModifiersForPopup(
+      UserActivation::Modifiers* aModifiers);
+
+  void IncrementHistoryEntryCountForBrowsingContext();
+
+  bool ServiceWorkersTestingEnabled() const {
+    return GetServiceWorkersTestingEnabled();
+  }
+
+  void GetMediumOverride(nsAString& aOverride) const {
+    aOverride = GetMediumOverride();
+  }
+
+  dom::PrefersColorSchemeOverride PrefersColorSchemeOverride() const {
+    return GetPrefersColorSchemeOverride();
+  }
+
+  bool IsInBFCache() const;
+
+  bool AllowJavascript() const { return GetAllowJavascript(); }
+  bool CanExecuteScripts() const { return mCanExecuteScripts; }
+
+  uint32_t DefaultLoadFlags() const { return GetDefaultLoadFlags(); }
+
+  // When request for page awake, it would increase a count that is used to
+  // prevent whole browsing context tree from being suspended. The request can
+  // be called multiple times. When calling the revoke, it would decrease the
+  // count and once the count reaches to zero, the browsing context tree could
+  // be suspended when the tree is inactive.
+  void RequestForPageAwake();
+  void RevokeForPageAwake();
+
+  void AddDiscardListener(std::function<void(uint64_t)>&& aListener);
+
+  bool IsAppTab() { return GetIsAppTab(); }
+  bool HasSiblings() { return GetHasSiblings(); }
+
+  bool IsUnderHiddenEmbedderElement() const {
+    return GetIsUnderHiddenEmbedderElement();
+  }
+
+  void LocationCreated(dom::Location* aLocation);
+  void ClearCachedValuesOfLocations();
+
+ protected:
+  virtual ~BrowsingContext();
+  BrowsingContext(WindowContext* aParentWindow, BrowsingContextGroup* aGroup,
+                  uint64_t aBrowsingContextId, Type aType, FieldValues&& aInit);
+
+  void SetChildSHistory(ChildSHistory* aChildSHistory);
+  already_AddRefed<ChildSHistory> ForgetChildSHistory() {
+    // FIXME Do we need to unset mHasSessionHistory?
+    return mChildSessionHistory.forget();
+  }
+
+  static bool ShouldAddEntryForRefresh(nsIURI* aCurrentURI,
+                                       const SessionHistoryInfo& aInfo);
+  static bool ShouldAddEntryForRefresh(nsIURI* aCurrentURI, nsIURI* aNewURI,
+                                       bool aHasPostData);
+
+ private:
+  mozilla::ipc::IPCResult Attach(bool aFromIPC, ContentParent* aOriginProcess);
+
+  // Recomputes whether we can execute scripts in this BrowsingContext based on
+  // the value of AllowJavascript() and whether scripts are allowed in the
+  // parent WindowContext. Called whenever the AllowJavascript() flag or the
+  // parent WC changes.
+  void RecomputeCanExecuteScripts();
+
+  // Is it early enough in the BrowsingContext's lifecycle that it is still
+  // OK to set OriginAttributes?
+  bool CanSetOriginAttributes();
+
+  void AssertOriginAttributesMatchPrivateBrowsing();
+
+  // Assert that the BrowsingContext's LoadContext flags appear coherent
+  // relative to related BrowsingContexts.
+  void AssertCoherentLoadContext();
+
+  friend class ::nsOuterWindowProxy;
+  friend class ::nsGlobalWindowOuter;
+  friend class WindowContext;
+
+  // Update the window proxy object that corresponds to this browsing context.
+  // This should be called from the window proxy object's objectMoved hook, if
+  // the object mWindowProxy points to was moved by the JS GC.
+  void UpdateWindowProxy(JSObject* obj, JSObject* old) {
+    if (mWindowProxy) {
+      MOZ_ASSERT(mWindowProxy == old);
+      mWindowProxy = obj;
+    }
+  }
+  // Clear the window proxy object that corresponds to this browsing context.
+  // This should be called if the window proxy object is finalized, or it can't
+  // reach its browsing context anymore.
+  void ClearWindowProxy() { mWindowProxy = nullptr; }
+
+  friend class Location;
+  friend class RemoteLocationProxy;
+  /**
+   * LocationProxy is the class for the native object stored as a private in a
+   * RemoteLocationProxy proxy representing a Location object in a different
+   * process. It forwards all operations to its BrowsingContext and aggregates
+   * its refcount to that BrowsingContext.
+   */
+  class LocationProxy final : public LocationBase {
+   public:
+    MozExternalRefCountType AddRef() { return GetBrowsingContext()->AddRef(); }
+    MozExternalRefCountType Release() {
+      return GetBrowsingContext()->Release();
+    }
+
+   protected:
+    friend class RemoteLocationProxy;
+    BrowsingContext* GetBrowsingContext() override {
+      return reinterpret_cast<BrowsingContext*>(
+          uintptr_t(this) - offsetof(BrowsingContext, mLocation));
+    }
+
+    nsIDocShell* GetDocShell() override { return nullptr; }
+  };
+
+  // Send a given `BaseTransaction` object to the correct remote.
+  void SendCommitTransaction(ContentParent* aParent,
+                             const BaseTransaction& aTxn, uint64_t aEpoch);
+  void SendCommitTransaction(ContentChild* aChild, const BaseTransaction& aTxn,
+                             uint64_t aEpoch);
+
+  bool CanSet(FieldIndex<IDX_SessionStoreEpoch>, uint32_t aEpoch,
+              ContentParent* aSource) {
+    return IsTop() && !aSource;
+  }
+
+  void DidSet(FieldIndex<IDX_SessionStoreEpoch>, uint32_t aOldValue);
+
+  using CanSetResult = syncedcontext::CanSetResult;
+
+  // Ensure that opener is in the same BrowsingContextGroup.
+  bool CanSet(FieldIndex<IDX_OpenerId>, const uint64_t& aValue,
+              ContentParent* aSource) {
+    if (aValue != 0) {
+      RefPtr<BrowsingContext> opener = Get(aValue);
+      return opener && opener->Group() == Group();
+    }
+    return true;
+  }
+
+  bool CanSet(FieldIndex<IDX_OpenerPolicy>,
+              nsILoadInfo::CrossOriginOpenerPolicy, ContentParent*);
+
+  bool CanSet(FieldIndex<IDX_ServiceWorkersTestingEnabled>, bool,
+              ContentParent*) {
+    return IsTop();
+  }
+
+  bool CanSet(FieldIndex<IDX_MediumOverride>, const nsString&, ContentParent*) {
+    return IsTop();
+  }
+
+  bool CanSet(FieldIndex<IDX_EmbedderColorSchemes>, const EmbedderColorSchemes&,
+              ContentParent* aSource) {
+    return CheckOnlyEmbedderCanSet(aSource);
+  }
+
+  bool CanSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+              dom::PrefersColorSchemeOverride, ContentParent*) {
+    return IsTop();
+  }
+
+  void DidSet(FieldIndex<IDX_InRDMPane>, bool aOldValue);
+
+  void DidSet(FieldIndex<IDX_EmbedderColorSchemes>,
+              EmbedderColorSchemes&& aOldValue);
+
+  void DidSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+              dom::PrefersColorSchemeOverride aOldValue);
+
+  template <typename Callback>
+  void WalkPresContexts(Callback&&);
+  void PresContextAffectingFieldChanged();
+
+  void DidSet(FieldIndex<IDX_MediumOverride>, nsString&& aOldValue);
+
+  bool CanSet(FieldIndex<IDX_SuspendMediaWhenInactive>, bool, ContentParent*) {
+    return IsTop();
+  }
+
+  bool CanSet(FieldIndex<IDX_TouchEventsOverrideInternal>,
+              dom::TouchEventsOverride aTouchEventsOverride,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_TouchEventsOverrideInternal>,
+              dom::TouchEventsOverride&& aOldValue);
+
+  bool CanSet(FieldIndex<IDX_DisplayMode>, const enum DisplayMode& aDisplayMode,
+              ContentParent* aSource) {
+    return IsTop();
+  }
+
+  void DidSet(FieldIndex<IDX_DisplayMode>, enum DisplayMode aOldValue);
+
+  bool CanSet(FieldIndex<IDX_ExplicitActive>, const ExplicitActiveStatus&,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_ExplicitActive>, ExplicitActiveStatus aOldValue);
+
+  bool CanSet(FieldIndex<IDX_IsActiveBrowserWindowInternal>, const bool& aValue,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_IsActiveBrowserWindowInternal>, bool aOldValue);
+
+  // Ensure that we only set the flag on the top level browsingContext.
+  // And then, we do a pre-order walk in the tree to refresh the
+  // volume of all media elements.
+  void DidSet(FieldIndex<IDX_Muted>);
+
+  bool CanSet(FieldIndex<IDX_IsAppTab>, const bool& aValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_HasSiblings>, const bool& aValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_ShouldDelayMediaFromStart>, const bool& aValue,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_ShouldDelayMediaFromStart>, bool aOldValue);
+
+  bool CanSet(FieldIndex<IDX_OverrideDPPX>, const float& aValue,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_OverrideDPPX>, float aOldValue);
+
+  bool CanSet(FieldIndex<IDX_EmbedderInnerWindowId>, const uint64_t& aValue,
+              ContentParent* aSource);
+
+  CanSetResult CanSet(FieldIndex<IDX_CurrentInnerWindowId>,
+                      const uint64_t& aValue, ContentParent* aSource);
+
+  void DidSet(FieldIndex<IDX_CurrentInnerWindowId>);
+
+  bool CanSet(FieldIndex<IDX_ParentInitiatedNavigationEpoch>,
+              const uint64_t& aValue, ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_IsPopupSpam>, const bool& aValue,
+              ContentParent* aSource);
+
+  void DidSet(FieldIndex<IDX_IsPopupSpam>);
+
+  void DidSet(FieldIndex<IDX_GVAudibleAutoplayRequestStatus>);
+  void DidSet(FieldIndex<IDX_GVInaudibleAutoplayRequestStatus>);
+
+  void DidSet(FieldIndex<IDX_Loading>);
+
+  void DidSet(FieldIndex<IDX_AncestorLoading>);
+
+  void DidSet(FieldIndex<IDX_PlatformOverride>);
+  CanSetResult CanSet(FieldIndex<IDX_PlatformOverride>,
+                      const nsString& aPlatformOverride,
+                      ContentParent* aSource);
+
+  void DidSet(FieldIndex<IDX_UserAgentOverride>);
+  CanSetResult CanSet(FieldIndex<IDX_UserAgentOverride>,
+                      const nsString& aUserAgent, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_OrientationLock>,
+              const mozilla::hal::ScreenOrientation& aOrientationLock,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_EmbedderElementType>,
+              const Maybe<nsString>& aInitiatorType, ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_MessageManagerGroup>,
+              const nsString& aMessageManagerGroup, ContentParent* aSource);
+
+  CanSetResult CanSet(FieldIndex<IDX_AllowContentRetargeting>,
+                      const bool& aAllowContentRetargeting,
+                      ContentParent* aSource);
+  CanSetResult CanSet(FieldIndex<IDX_AllowContentRetargetingOnChildren>,
+                      const bool& aAllowContentRetargetingOnChildren,
+                      ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_FullscreenAllowedByOwner>, const bool&,
+              ContentParent*);
+  bool CanSet(FieldIndex<IDX_WatchedByDevToolsInternal>,
+              const bool& aWatchedByDevToolsInternal, ContentParent* aSource);
+
+  CanSetResult CanSet(FieldIndex<IDX_DefaultLoadFlags>,
+                      const uint32_t& aDefaultLoadFlags,
+                      ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_DefaultLoadFlags>);
+
+  bool CanSet(FieldIndex<IDX_UseGlobalHistory>, const bool& aUseGlobalHistory,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_TargetTopLevelLinkClicksToBlankInternal>,
+              const bool& aTargetTopLevelLinkClicksToBlankInternal,
+              ContentParent* aSource);
+
+  void DidSet(FieldIndex<IDX_HasSessionHistory>, bool aOldValue);
+
+  bool CanSet(FieldIndex<IDX_BrowserId>, const uint32_t& aValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_UseErrorPages>, const bool& aUseErrorPages,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_PendingInitialization>, bool aNewValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_PageAwakeRequestCount>, uint32_t aNewValue,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_PageAwakeRequestCount>, uint32_t aOldValue);
+
+  CanSetResult CanSet(FieldIndex<IDX_AllowJavascript>, bool aValue,
+                      ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_AllowJavascript>, bool aOldValue);
+
+  bool CanSet(FieldIndex<IDX_ForceDesktopViewport>, bool aValue,
+              ContentParent* aSource) {
+    return IsTop() && XRE_IsParentProcess();
+  }
+
+  // TODO(emilio): Maybe handle the flag being set dynamically without
+  // navigating? The previous code didn't do it tho, and a reload is probably
+  // worth it regardless.
+  // void DidSet(FieldIndex<IDX_ForceDesktopViewport>, bool aOldValue);
+
+  bool CanSet(FieldIndex<IDX_HasRestoreData>, bool aNewValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_IsUnderHiddenEmbedderElement>,
+              const bool& aIsUnderHiddenEmbedderElement,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_ForceOffline>, bool aNewValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_EmbeddedInContentDocument>, bool,
+              ContentParent* aSource) {
+    return CheckOnlyEmbedderCanSet(aSource);
+  }
+
+  template <size_t I, typename T>
+  bool CanSet(FieldIndex<I>, const T&, ContentParent*) {
+    return true;
+  }
+
+  // Overload `DidSet` to get notifications for a particular field being set.
+  //
+  // You can also overload the variant that gets the old value if you need it.
+  template <size_t I>
+  void DidSet(FieldIndex<I>) {}
+  template <size_t I, typename T>
+  void DidSet(FieldIndex<I>, T&& aOldValue) {}
+
+  void DidSet(FieldIndex<IDX_FullZoom>, float aOldValue);
+  void DidSet(FieldIndex<IDX_TextZoom>, float aOldValue);
+  void DidSet(FieldIndex<IDX_AuthorStyleDisabledDefault>);
+
+  bool CanSet(FieldIndex<IDX_IsInBFCache>, bool, ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_IsInBFCache>);
+
+  void DidSet(FieldIndex<IDX_SyntheticDocumentContainer>);
+
+  void DidSet(FieldIndex<IDX_IsUnderHiddenEmbedderElement>, bool aOldValue);
+
+  // Allow if the process attemping to set field is the same as the owning
+  // process. Deprecated. New code that might use this should generally be moved
+  // to WindowContext or be settable only by the parent process.
+  CanSetResult LegacyRevertIfNotOwningOrParentProcess(ContentParent* aSource);
+
+  // True if the process attempting to set field is the same as the embedder's
+  // process.
+  bool CheckOnlyEmbedderCanSet(ContentParent* aSource);
+
+  void CreateChildSHistory();
+
+  using PrincipalWithLoadIdentifierTuple =
+      std::tuple<nsCOMPtr<nsIPrincipal>, uint64_t>;
+
+  nsIPrincipal* GetSavedPrincipal(
+      Maybe<PrincipalWithLoadIdentifierTuple> aPrincipalTuple);
+
+  // Type of BrowsingContent
+  const Type mType;
+
+  // Unique id identifying BrowsingContext
+  const uint64_t mBrowsingContextId;
+
+  RefPtr<BrowsingContextGroup> mGroup;
+  RefPtr<WindowContext> mParentWindow;
+  nsCOMPtr<nsIDocShell> mDocShell;
+
+  RefPtr<Element> mEmbedderElement;
+
+  nsTArray<RefPtr<WindowContext>> mWindowContexts;
+  RefPtr<WindowContext> mCurrentWindowContext;
+
+  // This is not a strong reference, but using a JS::Heap for that should be
+  // fine. The JSObject stored in here should be a proxy with a
+  // nsOuterWindowProxy handler, which will update the pointer from its
+  // objectMoved hook and clear it from its finalize hook.
+  JS::Heap<JSObject*> mWindowProxy;
+  LocationProxy mLocation;
+
+  // OriginAttributes for this BrowsingContext. May not be changed after this
+  // BrowsingContext is attached.
+  OriginAttributes mOriginAttributes;
+
+  // The network request context id, representing the nsIRequestContext
+  // associated with this BrowsingContext, and LoadGroups created for it.
+  uint64_t mRequestContextId = 0;
+
+  // Determines if private browsing should be used. May not be changed after
+  // this BrowsingContext is attached. This field matches mOriginAttributes in
+  // content Browsing Contexts. Currently treated as a binary value: 1 - in
+  // private mode, 0 - not private mode.
+  uint32_t mPrivateBrowsingId;
+
+  // True if Attach() has been called on this BrowsingContext already.
+  bool mEverAttached : 1;
+
+  // Is the most recent Document in this BrowsingContext loaded within this
+  // process? This may be true with a null mDocShell after the Window has been
+  // closed.
+  bool mIsInProcess : 1;
+
+  // Has this browsing context been discarded? BrowsingContexts should
+  // only be discarded once.
+  bool mIsDiscarded : 1;
+
+  // True if this BrowsingContext has no associated visible window, and is owned
+  // by whichever process created it, even if top-level.
+  bool mWindowless : 1;
+
+  // This is true if the BrowsingContext was out of process, but is now in
+  // process, and might have remote window proxies that need to be cleaned up.
+  bool mDanglingRemoteOuterProxies : 1;
+
+  // True if this BrowsingContext has been embedded in a element in this
+  // process.
+  bool mEmbeddedByThisProcess : 1;
+
+  // Determines if remote (out-of-process) tabs should be used. May not be
+  // changed after this BrowsingContext is attached.
+  bool mUseRemoteTabs : 1;
+
+  // Determines if out-of-process iframes should be used. May not be changed
+  // after this BrowsingContext is attached.
+  bool mUseRemoteSubframes : 1;
+
+  // True if this BrowsingContext is for a frame that was added dynamically.
+  bool mCreatedDynamically : 1;
+
+  // Set to true if the browsing context is in the bfcache and pagehide has been
+  // dispatched. When coming out from the bfcache, the value is set to false
+  // before dispatching pageshow.
+  bool mIsInBFCache : 1;
+
+  // Determines if we can execute scripts in this BrowsingContext. True if
+  // AllowJavascript() is true and script execution is allowed in the parent
+  // WindowContext.
+  bool mCanExecuteScripts : 1;
+
+  // The original offset of this context in its container. This property is -1
+  // if this BrowsingContext is for a frame that was added dynamically.
+  int32_t mChildOffset;
+
+  // The start time of user gesture, this is only available if the browsing
+  // context is in process.
+  TimeStamp mUserGestureStart;
+
+  // Triggering principal and principal to inherit need to point to original
+  // principal instances if the document is loaded in the same process as the
+  // process that initiated the load. When the load starts we save the
+  // principals along with the current load id.
+  // These principals correspond to the most recent load that took place within
+  // the process of this browsing context.
+  Maybe<PrincipalWithLoadIdentifierTuple> mTriggeringPrincipal;
+  Maybe<PrincipalWithLoadIdentifierTuple> mPrincipalToInherit;
+
+  class DeprioritizedLoadRunner
+      : public mozilla::Runnable,
+        public mozilla::LinkedListElement<DeprioritizedLoadRunner> {
+   public:
+    explicit DeprioritizedLoadRunner(nsIRunnable* aInner)
+        : Runnable("DeprioritizedLoadRunner"), mInner(aInner) {}
+
+    NS_IMETHOD Run() override {
+      if (mInner) {
+        RefPtr<nsIRunnable> inner = std::move(mInner);
+        inner->Run();
+      }
+
+      return NS_OK;
+    }
+
+   private:
+    RefPtr<nsIRunnable> mInner;
+  };
+
+  mozilla::LinkedList<DeprioritizedLoadRunner> mDeprioritizedLoadRunner;
+
+  RefPtr<SessionStorageManager> mSessionStorageManager;
+  RefPtr<ChildSHistory> mChildSessionHistory;
+
+  nsTArray<std::function<void(uint64_t)>> mDiscardListeners;
+
+  // Counter and time span for rate limiting Location and History API calls.
+  // Used by CheckLocationChangeRateLimit. Do not apply cross-process.
+  uint32_t mLocationChangeRateLimitCount;
+  mozilla::TimeStamp mLocationChangeRateLimitSpanStart;
+
+  mozilla::LinkedList<dom::Location> mLocations;
+};
+
+/**
+ * Gets a WindowProxy object for a BrowsingContext that lives in a different
+ * process (creating the object if it doesn't already exist). The WindowProxy
+ * object will be in the compartment that aCx is currently in. This should only
+ * be called if aContext doesn't hold a docshell, otherwise the BrowsingContext
+ * lives in this process, and a same-process WindowProxy should be used (see
+ * nsGlobalWindowOuter). This should only be called by bindings code, ToJSValue
+ * is the right API to get a WindowProxy for a BrowsingContext.
+ *
+ * If aTransplantTo is non-null, then the WindowProxy object will eventually be
+ * transplanted onto it. Therefore it should be used as the value in the remote
+ * proxy map. We assume that in this case the failure is unrecoverable, so we
+ * crash immediately rather than return false.
+ */
+extern bool GetRemoteOuterWindowProxy(JSContext* aCx, BrowsingContext* aContext,
+                                      JS::Handle<JSObject*> aTransplantTo,
+                                      JS::MutableHandle<JSObject*> aRetVal);
+
+using BrowsingContextTransaction = BrowsingContext::BaseTransaction;
+using BrowsingContextInitializer = BrowsingContext::IPCInitializer;
+using MaybeDiscardedBrowsingContext = MaybeDiscarded<BrowsingContext>;
+
+// Specialize the transaction object for every translation unit it's used in.
+extern template class syncedcontext::Transaction<BrowsingContext>;
+
+}  // namespace dom
+
+// Allow sending BrowsingContext objects over IPC.
+namespace ipc {
+template <>
+struct IPDLParamTraits<dom::MaybeDiscarded<dom::BrowsingContext>> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const dom::MaybeDiscarded<dom::BrowsingContext>& aParam);
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   dom::MaybeDiscarded<dom::BrowsingContext>* aResult);
+};
+
+template <>
+struct IPDLParamTraits<dom::BrowsingContext::IPCInitializer> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const dom::BrowsingContext::IPCInitializer& aInitializer);
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   dom::BrowsingContext::IPCInitializer* aInitializer);
+};
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // !defined(mozilla_dom_BrowsingContext_h)
diff --git a/docshell/base/BrowsingContextGroup.cpp b/docshell/base/BrowsingContextGroup.cpp
new file mode 100644
index 0000000000..622ed2a6c8
--- /dev/null
+++ b/docshell/base/BrowsingContextGroup.cpp
@@ -0,0 +1,570 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/BrowsingContextGroup.h"
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/InputTaskManager.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/BrowsingContextBinding.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/ThrottledEventQueue.h"
+#include "nsFocusManager.h"
+#include "nsTHashMap.h"
+
+namespace mozilla::dom {
+
+// Maximum number of successive dialogs before we prompt users to disable
+// dialogs for this window.
+#define MAX_SUCCESSIVE_DIALOG_COUNT 5
+
+static StaticRefPtr<BrowsingContextGroup> sChromeGroup;
+
+static StaticAutoPtr<nsTHashMap<uint64_t, RefPtr<BrowsingContextGroup>>>
+    sBrowsingContextGroups;
+
+already_AddRefed<BrowsingContextGroup> BrowsingContextGroup::GetOrCreate(
+    uint64_t aId) {
+  if (!sBrowsingContextGroups) {
+    sBrowsingContextGroups =
+        new nsTHashMap<nsUint64HashKey, RefPtr<BrowsingContextGroup>>();
+    ClearOnShutdown(&sBrowsingContextGroups);
+  }
+
+  return do_AddRef(sBrowsingContextGroups->LookupOrInsertWith(
+      aId, [&aId] { return do_AddRef(new BrowsingContextGroup(aId)); }));
+}
+
+already_AddRefed<BrowsingContextGroup> BrowsingContextGroup::GetExisting(
+    uint64_t aId) {
+  if (sBrowsingContextGroups) {
+    return do_AddRef(sBrowsingContextGroups->Get(aId));
+  }
+  return nullptr;
+}
+
+// Only use 53 bits for the BrowsingContextGroup ID.
+static constexpr uint64_t kBrowsingContextGroupIdTotalBits = 53;
+static constexpr uint64_t kBrowsingContextGroupIdProcessBits = 22;
+static constexpr uint64_t kBrowsingContextGroupIdFlagBits = 1;
+static constexpr uint64_t kBrowsingContextGroupIdBits =
+    kBrowsingContextGroupIdTotalBits - kBrowsingContextGroupIdProcessBits -
+    kBrowsingContextGroupIdFlagBits;
+
+// IDs for the relevant flags
+static constexpr uint64_t kPotentiallyCrossOriginIsolatedFlag = 0x1;
+
+// The next ID value which will be used.
+static uint64_t sNextBrowsingContextGroupId = 1;
+
+// Generate the next ID with the given flags.
+static uint64_t GenerateBrowsingContextGroupId(uint64_t aFlags) {
+  MOZ_RELEASE_ASSERT(aFlags < (uint64_t(1) << kBrowsingContextGroupIdFlagBits));
+  uint64_t childId = XRE_IsContentProcess()
+                         ? ContentChild::GetSingleton()->GetID()
+                         : uint64_t(0);
+  MOZ_RELEASE_ASSERT(childId <
+                     (uint64_t(1) << kBrowsingContextGroupIdProcessBits));
+  uint64_t id = sNextBrowsingContextGroupId++;
+  MOZ_RELEASE_ASSERT(id < (uint64_t(1) << kBrowsingContextGroupIdBits));
+
+  return (childId << (kBrowsingContextGroupIdBits +
+                      kBrowsingContextGroupIdFlagBits)) |
+         (id << kBrowsingContextGroupIdFlagBits) | aFlags;
+}
+
+// Extract flags from the given ID.
+static uint64_t GetBrowsingContextGroupIdFlags(uint64_t aId) {
+  return aId & ((uint64_t(1) << kBrowsingContextGroupIdFlagBits) - 1);
+}
+
+uint64_t BrowsingContextGroup::CreateId(bool aPotentiallyCrossOriginIsolated) {
+  // We encode the potentially cross-origin isolated bit within the ID so that
+  // the information can be recovered whenever the group needs to be re-created
+  // due to e.g. being garbage-collected.
+  //
+  // In the future if we end up needing more complex information stored within
+  // the ID, we can consider converting it to a more complex type, like a
+  // string.
+  uint64_t flags =
+      aPotentiallyCrossOriginIsolated ? kPotentiallyCrossOriginIsolatedFlag : 0;
+  uint64_t id = GenerateBrowsingContextGroupId(flags);
+  MOZ_ASSERT(GetBrowsingContextGroupIdFlags(id) == flags);
+  return id;
+}
+
+already_AddRefed<BrowsingContextGroup> BrowsingContextGroup::Create(
+    bool aPotentiallyCrossOriginIsolated) {
+  return GetOrCreate(CreateId(aPotentiallyCrossOriginIsolated));
+}
+
+BrowsingContextGroup::BrowsingContextGroup(uint64_t aId) : mId(aId) {
+  mTimerEventQueue = ThrottledEventQueue::Create(
+      GetMainThreadSerialEventTarget(), "BrowsingContextGroup timer queue");
+
+  mWorkerEventQueue = ThrottledEventQueue::Create(
+      GetMainThreadSerialEventTarget(), "BrowsingContextGroup worker queue");
+}
+
+void BrowsingContextGroup::Register(nsISupports* aContext) {
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(aContext);
+  mContexts.Insert(aContext);
+}
+
+void BrowsingContextGroup::Unregister(nsISupports* aContext) {
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(aContext);
+  mContexts.Remove(aContext);
+
+  MaybeDestroy();
+}
+
+void BrowsingContextGroup::EnsureHostProcess(ContentParent* aProcess) {
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(this != sChromeGroup,
+                        "cannot have content host for chrome group");
+  MOZ_DIAGNOSTIC_ASSERT(aProcess->GetRemoteType() != PREALLOC_REMOTE_TYPE,
+                        "cannot use preallocated process as host");
+  MOZ_DIAGNOSTIC_ASSERT(!aProcess->GetRemoteType().IsEmpty(),
+                        "host process must have remote type");
+
+  // XXX: The diagnostic crashes in bug 1816025 seemed to come through caller
+  // ContentParent::GetNewOrUsedLaunchingBrowserProcess where we already
+  // did AssertAlive, so IsDead should be irrelevant here. Still it reads
+  // wrong that we ever might do AddBrowsingContextGroup if aProcess->IsDead().
+  if (aProcess->IsDead() ||
+      mHosts.WithEntryHandle(aProcess->GetRemoteType(), [&](auto&& entry) {
+        if (entry) {
+          // We know from bug 1816025 that this happens quite often and we have
+          // bug 1815480 on file that should harden the entire flow. But in the
+          // meantime we can just live with NOT replacing the found host
+          // process with a new one here if it is still alive.
+          MOZ_ASSERT(
+              entry.Data() == aProcess,
+              "There's already another host process for this remote type");
+          if (!entry.Data()->IsShuttingDown()) {
+            return false;
+          }
+        }
+
+        // This process wasn't already marked as our host, so insert it (or
+        // update if the old process is shutting down), and begin subscribing,
+        // unless the process is still launching.
+        entry.InsertOrUpdate(do_AddRef(aProcess));
+
+        return true;
+      })) {
+    aProcess->AddBrowsingContextGroup(this);
+  }
+}
+
+void BrowsingContextGroup::RemoveHostProcess(ContentParent* aProcess) {
+  MOZ_DIAGNOSTIC_ASSERT(aProcess);
+  MOZ_DIAGNOSTIC_ASSERT(aProcess->GetRemoteType() != PREALLOC_REMOTE_TYPE);
+  auto entry = mHosts.Lookup(aProcess->GetRemoteType());
+  if (entry && entry.Data() == aProcess) {
+    entry.Remove();
+  }
+}
+
+static void CollectContextInitializers(
+    Span<RefPtr<BrowsingContext>> aContexts,
+    nsTArray<SyncedContextInitializer>& aInits) {
+  // The order that we record these initializers is important, as it will keep
+  // the order that children are attached to their parent in the newly connected
+  // content process consistent.
+  for (auto& context : aContexts) {
+    aInits.AppendElement(context->GetIPCInitializer());
+    for (const auto& window : context->GetWindowContexts()) {
+      aInits.AppendElement(window->GetIPCInitializer());
+      CollectContextInitializers(window->Children(), aInits);
+    }
+  }
+}
+
+void BrowsingContextGroup::Subscribe(ContentParent* aProcess) {
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(aProcess && !aProcess->IsLaunching());
+  MOZ_DIAGNOSTIC_ASSERT(aProcess->GetRemoteType() != PREALLOC_REMOTE_TYPE);
+
+  // Check if we're already subscribed to this process.
+  if (!mSubscribers.EnsureInserted(aProcess)) {
+    return;
+  }
+
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  // If the process is already marked as dead, we won't be the host, but may
+  // still need to subscribe to the process due to creating a popup while
+  // shutting down.
+  if (!aProcess->IsDead()) {
+    auto hostEntry = mHosts.Lookup(aProcess->GetRemoteType());
+    MOZ_DIAGNOSTIC_ASSERT(hostEntry && hostEntry.Data() == aProcess,
+                          "Cannot subscribe a non-host process");
+  }
+#endif
+
+  // FIXME: This won't send non-discarded children of discarded BCs, but those
+  // BCs will be in the process of being destroyed anyway.
+  // FIXME: Prevent that situation from occuring.
+  nsTArray<SyncedContextInitializer> inits(mContexts.Count());
+  CollectContextInitializers(mToplevels, inits);
+
+  // Send all of our contexts to the target content process.
+  Unused << aProcess->SendRegisterBrowsingContextGroup(Id(), inits);
+
+  // If the focused or active BrowsingContexts belong in this group, tell the
+  // newly subscribed process.
+  if (nsFocusManager* fm = nsFocusManager::GetFocusManager()) {
+    BrowsingContext* focused = fm->GetFocusedBrowsingContextInChrome();
+    if (focused && focused->Group() != this) {
+      focused = nullptr;
+    }
+    BrowsingContext* active = fm->GetActiveBrowsingContextInChrome();
+    if (active && active->Group() != this) {
+      active = nullptr;
+    }
+
+    if (focused || active) {
+      Unused << aProcess->SendSetupFocusedAndActive(
+          focused, fm->GetActionIdForFocusedBrowsingContextInChrome(), active,
+          fm->GetActionIdForActiveBrowsingContextInChrome());
+    }
+  }
+}
+
+void BrowsingContextGroup::Unsubscribe(ContentParent* aProcess) {
+  MOZ_DIAGNOSTIC_ASSERT(aProcess);
+  MOZ_DIAGNOSTIC_ASSERT(aProcess->GetRemoteType() != PREALLOC_REMOTE_TYPE);
+  mSubscribers.Remove(aProcess);
+  aProcess->RemoveBrowsingContextGroup(this);
+
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  auto hostEntry = mHosts.Lookup(aProcess->GetRemoteType());
+  MOZ_DIAGNOSTIC_ASSERT(!hostEntry || hostEntry.Data() != aProcess,
+                        "Unsubscribing existing host entry");
+#endif
+}
+
+ContentParent* BrowsingContextGroup::GetHostProcess(
+    const nsACString& aRemoteType) {
+  return mHosts.GetWeak(aRemoteType);
+}
+
+void BrowsingContextGroup::UpdateToplevelsSuspendedIfNeeded() {
+  if (!StaticPrefs::dom_suspend_inactive_enabled()) {
+    return;
+  }
+
+  mToplevelsSuspended = ShouldSuspendAllTopLevelContexts();
+  for (const auto& context : mToplevels) {
+    nsPIDOMWindowOuter* outer = context->GetDOMWindow();
+    if (!outer) {
+      continue;
+    }
+    nsCOMPtr<nsPIDOMWindowInner> inner = outer->GetCurrentInnerWindow();
+    if (!inner) {
+      continue;
+    }
+    if (mToplevelsSuspended && !inner->GetWasSuspendedByGroup()) {
+      inner->Suspend();
+      inner->SetWasSuspendedByGroup(true);
+    } else if (!mToplevelsSuspended && inner->GetWasSuspendedByGroup()) {
+      inner->Resume();
+      inner->SetWasSuspendedByGroup(false);
+    }
+  }
+}
+
+bool BrowsingContextGroup::ShouldSuspendAllTopLevelContexts() const {
+  for (const auto& context : mToplevels) {
+    if (!context->InactiveForSuspend()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+BrowsingContextGroup::~BrowsingContextGroup() { Destroy(); }
+
+void BrowsingContextGroup::Destroy() {
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  if (mDestroyed) {
+    MOZ_DIAGNOSTIC_ASSERT(mHosts.Count() == 0);
+    MOZ_DIAGNOSTIC_ASSERT(mSubscribers.Count() == 0);
+    MOZ_DIAGNOSTIC_ASSERT_IF(sBrowsingContextGroups,
+                             !sBrowsingContextGroups->Contains(Id()) ||
+                                 *sBrowsingContextGroups->Lookup(Id()) != this);
+  }
+  mDestroyed = true;
+#endif
+
+  // Make sure to call `RemoveBrowsingContextGroup` for every entry in both
+  // `mHosts` and `mSubscribers`. This will visit most entries twice, but
+  // `RemoveBrowsingContextGroup` is safe to call multiple times.
+  for (const auto& entry : mHosts.Values()) {
+    entry->RemoveBrowsingContextGroup(this);
+  }
+  for (const auto& key : mSubscribers) {
+    key->RemoveBrowsingContextGroup(this);
+  }
+  mHosts.Clear();
+  mSubscribers.Clear();
+
+  if (sBrowsingContextGroups) {
+    sBrowsingContextGroups->Remove(Id());
+  }
+}
+
+void BrowsingContextGroup::AddKeepAlive() {
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+  mKeepAliveCount++;
+}
+
+void BrowsingContextGroup::RemoveKeepAlive() {
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(mKeepAliveCount > 0);
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+  mKeepAliveCount--;
+
+  MaybeDestroy();
+}
+
+auto BrowsingContextGroup::MakeKeepAlivePtr() -> KeepAlivePtr {
+  AddKeepAlive();
+  return KeepAlivePtr{do_AddRef(this).take()};
+}
+
+void BrowsingContextGroup::MaybeDestroy() {
+  // Once there are no synced contexts referencing a `BrowsingContextGroup`, we
+  // can clear subscribers and destroy this group. We only do this in the parent
+  // process, as it will orchestrate destruction of BCGs in content processes.
+  if (XRE_IsParentProcess() && mContexts.IsEmpty() && mKeepAliveCount == 0 &&
+      this != sChromeGroup) {
+    Destroy();
+
+    // We may have been deleted here, as `Destroy()` will clear references. Do
+    // not access any members at this point.
+  }
+}
+
+void BrowsingContextGroup::ChildDestroy() {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsContentProcess());
+  MOZ_DIAGNOSTIC_ASSERT(!mDestroyed);
+  MOZ_DIAGNOSTIC_ASSERT(mContexts.IsEmpty());
+  Destroy();
+}
+
+nsISupports* BrowsingContextGroup::GetParentObject() const {
+  return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
+}
+
+JSObject* BrowsingContextGroup::WrapObject(JSContext* aCx,
+                                           JS::Handle<JSObject*> aGivenProto) {
+  return BrowsingContextGroup_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+nsresult BrowsingContextGroup::QueuePostMessageEvent(nsIRunnable* aRunnable) {
+  MOZ_ASSERT(StaticPrefs::dom_separate_event_queue_for_post_message_enabled());
+
+  if (!mPostMessageEventQueue) {
+    nsCOMPtr<nsISerialEventTarget> target = GetMainThreadSerialEventTarget();
+    mPostMessageEventQueue = ThrottledEventQueue::Create(
+        target, "PostMessage Queue",
+        nsIRunnablePriority::PRIORITY_DEFERRED_TIMERS);
+    nsresult rv = mPostMessageEventQueue->SetIsPaused(false);
+    MOZ_ALWAYS_SUCCEEDS(rv);
+  }
+
+  // Ensure the queue is enabled
+  if (mPostMessageEventQueue->IsPaused()) {
+    nsresult rv = mPostMessageEventQueue->SetIsPaused(false);
+    MOZ_ALWAYS_SUCCEEDS(rv);
+  }
+
+  return mPostMessageEventQueue->Dispatch(aRunnable, NS_DISPATCH_NORMAL);
+}
+
+void BrowsingContextGroup::FlushPostMessageEvents() {
+  if (!mPostMessageEventQueue) {
+    return;
+  }
+  nsresult rv = mPostMessageEventQueue->SetIsPaused(true);
+  MOZ_ALWAYS_SUCCEEDS(rv);
+  nsCOMPtr<nsIRunnable> event;
+  while ((event = mPostMessageEventQueue->GetEvent())) {
+    NS_DispatchToMainThread(event.forget());
+  }
+}
+
+bool BrowsingContextGroup::HasActiveBC() {
+  for (auto& topLevelBC : Toplevels()) {
+    if (topLevelBC->IsActive()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void BrowsingContextGroup::IncInputEventSuspensionLevel() {
+  MOZ_ASSERT(StaticPrefs::dom_input_events_canSuspendInBCG_enabled());
+  if (!mHasIncreasedInputTaskManagerSuspensionLevel && HasActiveBC()) {
+    IncInputTaskManagerSuspensionLevel();
+  }
+  ++mInputEventSuspensionLevel;
+}
+
+void BrowsingContextGroup::DecInputEventSuspensionLevel() {
+  MOZ_ASSERT(StaticPrefs::dom_input_events_canSuspendInBCG_enabled());
+  --mInputEventSuspensionLevel;
+  if (!mInputEventSuspensionLevel &&
+      mHasIncreasedInputTaskManagerSuspensionLevel) {
+    DecInputTaskManagerSuspensionLevel();
+  }
+}
+
+void BrowsingContextGroup::DecInputTaskManagerSuspensionLevel() {
+  MOZ_ASSERT(StaticPrefs::dom_input_events_canSuspendInBCG_enabled());
+  MOZ_ASSERT(mHasIncreasedInputTaskManagerSuspensionLevel);
+
+  InputTaskManager::Get()->DecSuspensionLevel();
+  mHasIncreasedInputTaskManagerSuspensionLevel = false;
+}
+
+void BrowsingContextGroup::IncInputTaskManagerSuspensionLevel() {
+  MOZ_ASSERT(StaticPrefs::dom_input_events_canSuspendInBCG_enabled());
+  MOZ_ASSERT(!mHasIncreasedInputTaskManagerSuspensionLevel);
+  MOZ_ASSERT(HasActiveBC());
+
+  InputTaskManager::Get()->IncSuspensionLevel();
+  mHasIncreasedInputTaskManagerSuspensionLevel = true;
+}
+
+void BrowsingContextGroup::UpdateInputTaskManagerIfNeeded(bool aIsActive) {
+  MOZ_ASSERT(StaticPrefs::dom_input_events_canSuspendInBCG_enabled());
+  if (!aIsActive) {
+    if (mHasIncreasedInputTaskManagerSuspensionLevel) {
+      MOZ_ASSERT(mInputEventSuspensionLevel > 0);
+      if (!HasActiveBC()) {
+        DecInputTaskManagerSuspensionLevel();
+      }
+    }
+  } else {
+    if (mInputEventSuspensionLevel &&
+        !mHasIncreasedInputTaskManagerSuspensionLevel) {
+      IncInputTaskManagerSuspensionLevel();
+    }
+  }
+}
+
+/* static */
+BrowsingContextGroup* BrowsingContextGroup::GetChromeGroup() {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+  if (!sChromeGroup && XRE_IsParentProcess()) {
+    sChromeGroup = BrowsingContextGroup::Create();
+    ClearOnShutdown(&sChromeGroup);
+  }
+
+  return sChromeGroup;
+}
+
+void BrowsingContextGroup::GetDocGroups(nsTArray<DocGroup*>& aDocGroups) {
+  MOZ_ASSERT(NS_IsMainThread());
+  AppendToArray(aDocGroups, mDocGroups.Values());
+}
+
+already_AddRefed<DocGroup> BrowsingContextGroup::AddDocument(
+    const nsACString& aKey, Document* aDocument) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  RefPtr<DocGroup>& docGroup = mDocGroups.LookupOrInsertWith(
+      aKey, [&] { return DocGroup::Create(this, aKey); });
+
+  docGroup->AddDocument(aDocument);
+  return do_AddRef(docGroup);
+}
+
+void BrowsingContextGroup::RemoveDocument(Document* aDocument,
+                                          DocGroup* aDocGroup) {
+  MOZ_ASSERT(NS_IsMainThread());
+  RefPtr<DocGroup> docGroup = aDocGroup;
+  // Removing the last document in DocGroup might decrement the
+  // DocGroup BrowsingContextGroup's refcount to 0.
+  RefPtr<BrowsingContextGroup> kungFuDeathGrip(this);
+  docGroup->RemoveDocument(aDocument);
+
+  if (docGroup->IsEmpty()) {
+    mDocGroups.Remove(docGroup->GetKey());
+  }
+}
+
+already_AddRefed<BrowsingContextGroup> BrowsingContextGroup::Select(
+    WindowContext* aParent, BrowsingContext* aOpener) {
+  if (aParent) {
+    return do_AddRef(aParent->Group());
+  }
+  if (aOpener) {
+    return do_AddRef(aOpener->Group());
+  }
+  return Create();
+}
+
+void BrowsingContextGroup::GetAllGroups(
+    nsTArray<RefPtr<BrowsingContextGroup>>& aGroups) {
+  aGroups.Clear();
+  if (!sBrowsingContextGroups) {
+    return;
+  }
+
+  aGroups = ToArray(sBrowsingContextGroups->Values());
+}
+
+// For tests only.
+void BrowsingContextGroup::ResetDialogAbuseState() {
+  mDialogAbuseCount = 0;
+  // Reset the timer.
+  mLastDialogQuitTime =
+      TimeStamp::Now() -
+      TimeDuration::FromSeconds(DEFAULT_SUCCESSIVE_DIALOG_TIME_LIMIT);
+}
+
+bool BrowsingContextGroup::DialogsAreBeingAbused() {
+  if (mLastDialogQuitTime.IsNull() || nsContentUtils::IsCallerChrome()) {
+    return false;
+  }
+
+  TimeDuration dialogInterval(TimeStamp::Now() - mLastDialogQuitTime);
+  if (dialogInterval.ToSeconds() <
+      Preferences::GetInt("dom.successive_dialog_time_limit",
+                          DEFAULT_SUCCESSIVE_DIALOG_TIME_LIMIT)) {
+    mDialogAbuseCount++;
+
+    return PopupBlocker::GetPopupControlState() > PopupBlocker::openAllowed ||
+           mDialogAbuseCount > MAX_SUCCESSIVE_DIALOG_COUNT;
+  }
+
+  // Reset the abuse counter
+  mDialogAbuseCount = 0;
+
+  return false;
+}
+
+bool BrowsingContextGroup::IsPotentiallyCrossOriginIsolated() {
+  return GetBrowsingContextGroupIdFlags(mId) &
+         kPotentiallyCrossOriginIsolatedFlag;
+}
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(BrowsingContextGroup, mContexts,
+                                      mToplevels, mHosts, mSubscribers,
+                                      mTimerEventQueue, mWorkerEventQueue,
+                                      mDocGroups)
+
+}  // namespace mozilla::dom
diff --git a/docshell/base/BrowsingContextGroup.h b/docshell/base/BrowsingContextGroup.h
new file mode 100644
index 0000000000..2f8649da2d
--- /dev/null
+++ b/docshell/base/BrowsingContextGroup.h
@@ -0,0 +1,318 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BrowsingContextGroup_h
+#define mozilla_dom_BrowsingContextGroup_h
+
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/FunctionRef.h"
+#include "nsRefPtrHashtable.h"
+#include "nsHashKeys.h"
+#include "nsTArray.h"
+#include "nsTHashSet.h"
+#include "nsWrapperCache.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+class ThrottledEventQueue;
+
+namespace dom {
+
+// Amount of time allowed between alert/prompt/confirm before enabling
+// the stop dialog checkbox.
+#define DEFAULT_SUCCESSIVE_DIALOG_TIME_LIMIT 3  // 3 sec
+
+class BrowsingContext;
+class WindowContext;
+class ContentParent;
+class DocGroup;
+
+// A BrowsingContextGroup represents the Unit of Related Browsing Contexts in
+// the standard.
+//
+// A BrowsingContext may not hold references to other BrowsingContext objects
+// which are not in the same BrowsingContextGroup.
+class BrowsingContextGroup final : public nsWrapperCache {
+ public:
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(BrowsingContextGroup)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_WRAPPERCACHE_CLASS(BrowsingContextGroup)
+
+  // Interact with the list of synced contexts. This controls the lifecycle of
+  // the BrowsingContextGroup and contexts loaded within them.
+  void Register(nsISupports* aContext);
+  void Unregister(nsISupports* aContext);
+
+  // Control which processes will be used to host documents loaded in this
+  // BrowsingContextGroup. There should only ever be one host process per remote
+  // type.
+  //
+  // A new host process will be subscribed to the BrowsingContextGroup unless it
+  // is still launching, in which case it will subscribe itself when it is done
+  // launching.
+  void EnsureHostProcess(ContentParent* aProcess);
+
+  // A removed host process will no longer be used to host documents loaded in
+  // this BrowsingContextGroup.
+  void RemoveHostProcess(ContentParent* aProcess);
+
+  // Synchronize the current BrowsingContextGroup state down to the given
+  // content process, and continue updating it.
+  //
+  // You rarely need to call this directly, as it's automatically called by
+  // |EnsureHostProcess| as needed.
+  void Subscribe(ContentParent* aProcess);
+
+  // Stop synchronizing the current BrowsingContextGroup state down to a given
+  // content process. The content process must no longer be a host process.
+  void Unsubscribe(ContentParent* aProcess);
+
+  // Look up the process which should be used to host documents with this
+  // RemoteType. This will be a non-dead process associated with this
+  // BrowsingContextGroup, if possible.
+  ContentParent* GetHostProcess(const nsACString& aRemoteType);
+
+  // When a BrowsingContext is being discarded, we may want to keep the
+  // corresponding BrowsingContextGroup alive until the other process
+  // acknowledges that the BrowsingContext has been discarded. A `KeepAlive`
+  // will be added to the `BrowsingContextGroup`, delaying destruction.
+  void AddKeepAlive();
+  void RemoveKeepAlive();
+
+  // A `KeepAlivePtr` will hold both a strong reference to the
+  // `BrowsingContextGroup` and holds a `KeepAlive`. When the pointer is
+  // dropped, it will release both the strong reference and the keepalive.
+  struct KeepAliveDeleter {
+    void operator()(BrowsingContextGroup* aPtr) {
+      if (RefPtr<BrowsingContextGroup> ptr = already_AddRefed(aPtr)) {
+        ptr->RemoveKeepAlive();
+      }
+    }
+  };
+  using KeepAlivePtr = UniquePtr<BrowsingContextGroup, KeepAliveDeleter>;
+  KeepAlivePtr MakeKeepAlivePtr();
+
+  // Call when we want to check if we should suspend or resume all top level
+  // contexts.
+  void UpdateToplevelsSuspendedIfNeeded();
+
+  // Get a reference to the list of toplevel contexts in this
+  // BrowsingContextGroup.
+  nsTArray<RefPtr<BrowsingContext>>& Toplevels() { return mToplevels; }
+  void GetToplevels(nsTArray<RefPtr<BrowsingContext>>& aToplevels) {
+    aToplevels.AppendElements(mToplevels);
+  }
+
+  uint64_t Id() { return mId; }
+
+  nsISupports* GetParentObject() const;
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  // Get or create a BrowsingContextGroup with the given ID.
+  static already_AddRefed<BrowsingContextGroup> GetOrCreate(uint64_t aId);
+  static already_AddRefed<BrowsingContextGroup> GetExisting(uint64_t aId);
+  static already_AddRefed<BrowsingContextGroup> Create(
+      bool aPotentiallyCrossOriginIsolated = false);
+  static already_AddRefed<BrowsingContextGroup> Select(
+      WindowContext* aParent, BrowsingContext* aOpener);
+
+  // Like `Create` but only generates and reserves a new ID without actually
+  // creating the BrowsingContextGroup object.
+  static uint64_t CreateId(bool aPotentiallyCrossOriginIsolated = false);
+
+  // For each 'ContentParent', except for 'aExcludedParent',
+  // associated with this group call 'aCallback'.
+  template <typename Func>
+  void EachOtherParent(ContentParent* aExcludedParent, Func&& aCallback) {
+    MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+    for (const auto& key : mSubscribers) {
+      if (key != aExcludedParent) {
+        aCallback(key);
+      }
+    }
+  }
+
+  // For each 'ContentParent' associated with
+  // this group call 'aCallback'.
+  template <typename Func>
+  void EachParent(Func&& aCallback) {
+    MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+    for (const auto& key : mSubscribers) {
+      aCallback(key);
+    }
+  }
+
+  nsresult QueuePostMessageEvent(nsIRunnable* aRunnable);
+
+  void FlushPostMessageEvents();
+
+  // Increase or decrease the suspension level in InputTaskManager
+  void UpdateInputTaskManagerIfNeeded(bool aIsActive);
+
+  static BrowsingContextGroup* GetChromeGroup();
+
+  void GetDocGroups(nsTArray<DocGroup*>& aDocGroups);
+
+  // Called by Document when a Document needs to be added to a DocGroup.
+  already_AddRefed<DocGroup> AddDocument(const nsACString& aKey,
+                                         Document* aDocument);
+
+  // Called by Document when a Document needs to be removed from a DocGroup.
+  // aDocGroup should be from aDocument. This is done to avoid the assert
+  // in GetDocGroup() which can crash when called during unlinking.
+  void RemoveDocument(Document* aDocument, DocGroup* aDocGroup);
+
+  mozilla::ThrottledEventQueue* GetTimerEventQueue() const {
+    return mTimerEventQueue;
+  }
+
+  mozilla::ThrottledEventQueue* GetWorkerEventQueue() const {
+    return mWorkerEventQueue;
+  }
+
+  void SetAreDialogsEnabled(bool aAreDialogsEnabled) {
+    mAreDialogsEnabled = aAreDialogsEnabled;
+  }
+
+  bool GetAreDialogsEnabled() { return mAreDialogsEnabled; }
+
+  bool GetDialogAbuseCount() { return mDialogAbuseCount; }
+
+  // For tests only.
+  void ResetDialogAbuseState();
+
+  bool DialogsAreBeingAbused();
+
+  TimeStamp GetLastDialogQuitTime() { return mLastDialogQuitTime; }
+
+  void SetLastDialogQuitTime(TimeStamp aLastDialogQuitTime) {
+    mLastDialogQuitTime = aLastDialogQuitTime;
+  }
+
+  // Whether all toplevel documents loaded in this group are allowed to be
+  // Cross-Origin Isolated.
+  //
+  // This does not reflect the actual value of `crossOriginIsolated`, as that
+  // also requires that the document is loaded within a `webCOOP+COEP` content
+  // process.
+  bool IsPotentiallyCrossOriginIsolated();
+
+  static void GetAllGroups(nsTArray<RefPtr<BrowsingContextGroup>>& aGroups);
+
+  void IncInputEventSuspensionLevel();
+  void DecInputEventSuspensionLevel();
+
+  void ChildDestroy();
+
+ private:
+  friend class CanonicalBrowsingContext;
+
+  explicit BrowsingContextGroup(uint64_t aId);
+  ~BrowsingContextGroup();
+
+  void MaybeDestroy();
+  void Destroy();
+
+  bool ShouldSuspendAllTopLevelContexts() const;
+
+  bool HasActiveBC();
+  void DecInputTaskManagerSuspensionLevel();
+  void IncInputTaskManagerSuspensionLevel();
+
+  uint64_t mId;
+
+  uint32_t mKeepAliveCount = 0;
+
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  bool mDestroyed = false;
+#endif
+
+  // A BrowsingContextGroup contains a series of {Browsing,Window}Context
+  // objects. They are addressed using a hashtable to avoid linear lookup when
+  // adding or removing elements from the set.
+  //
+  // FIXME: This list is only required over a counter to keep nested
+  // non-discarded contexts within discarded contexts alive. It should be
+  // removed in the future.
+  // FIXME: Consider introducing a better common base than `nsISupports`?
+  nsTHashSet<nsRefPtrHashKey<nsISupports>> mContexts;
+
+  // The set of toplevel browsing contexts in the current BrowsingContextGroup.
+  nsTArray<RefPtr<BrowsingContext>> mToplevels;
+
+  //  Whether or not all toplevels in this group should be suspended
+  bool mToplevelsSuspended = false;
+
+  // DocGroups are thread-safe, and not able to be cycle collected,
+  // but we still keep strong pointers. When all Documents are removed
+  // from DocGroup (by the BrowsingContextGroup), the DocGroup is
+  // removed from here.
+  nsRefPtrHashtable<nsCStringHashKey, DocGroup> mDocGroups;
+
+  // The content process which will host documents in this BrowsingContextGroup
+  // which need to be loaded with a given remote type.
+  //
+  // A non-launching host process must also be a subscriber, though a launching
+  // host process may not yet be subscribed, and a subscriber need not be a host
+  // process.
+  nsRefPtrHashtable<nsCStringHashKey, ContentParent> mHosts;
+
+  nsTHashSet<nsRefPtrHashKey<ContentParent>> mSubscribers;
+
+  // A queue to store postMessage events during page load, the queue will be
+  // flushed once the page is loaded
+  RefPtr<mozilla::ThrottledEventQueue> mPostMessageEventQueue;
+
+  RefPtr<mozilla::ThrottledEventQueue> mTimerEventQueue;
+  RefPtr<mozilla::ThrottledEventQueue> mWorkerEventQueue;
+
+  // A counter to keep track of the input event suspension level of this BCG
+  //
+  // We use BrowsingContextGroup to emulate process isolation in Fission, so
+  // documents within the same the same BCG will behave like they share
+  // the same input task queue.
+  uint32_t mInputEventSuspensionLevel = 0;
+  // Whether this BCG has increased the suspension level in InputTaskManager
+  bool mHasIncreasedInputTaskManagerSuspensionLevel = false;
+
+  // This flag keeps track of whether dialogs are
+  // currently enabled for windows of this group.
+  // It's OK to have these local to each process only because even if
+  // frames from two/three different sites (and thus, processes) coordinate a
+  // dialog abuse attack, they would only the double/triple number of dialogs,
+  // as it is still limited per-site.
+  bool mAreDialogsEnabled = true;
+
+  // This counts the number of windows that have been opened in rapid succession
+  // (i.e. within dom.successive_dialog_time_limit of each other). It is reset
+  // to 0 once a dialog is opened after dom.successive_dialog_time_limit seconds
+  // have elapsed without any other dialogs.
+  // See comment for mAreDialogsEnabled as to why it's ok to have this local to
+  // each process.
+  uint32_t mDialogAbuseCount = 0;
+
+  // This holds the time when the last modal dialog was shown. If more than
+  // MAX_DIALOG_LIMIT dialogs are shown within the time span defined by
+  // dom.successive_dialog_time_limit, we show a checkbox or confirmation prompt
+  // to allow disabling of further dialogs from windows in this BC group.
+  TimeStamp mLastDialogQuitTime;
+};
+}  // namespace dom
+}  // namespace mozilla
+
+inline void ImplCycleCollectionUnlink(
+    mozilla::dom::BrowsingContextGroup::KeepAlivePtr& aField) {
+  aField = nullptr;
+}
+
+inline void ImplCycleCollectionTraverse(
+    nsCycleCollectionTraversalCallback& aCallback,
+    mozilla::dom::BrowsingContextGroup::KeepAlivePtr& aField, const char* aName,
+    uint32_t aFlags = 0) {
+  CycleCollectionNoteChild(aCallback, aField.get(), aName, aFlags);
+}
+
+#endif  // !defined(mozilla_dom_BrowsingContextGroup_h)
diff --git a/docshell/base/BrowsingContextWebProgress.cpp b/docshell/base/BrowsingContextWebProgress.cpp
new file mode 100644
index 0000000000..7c915bd666
--- /dev/null
+++ b/docshell/base/BrowsingContextWebProgress.cpp
@@ -0,0 +1,443 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BrowsingContextWebProgress.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/BounceTrackingState.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/ErrorNames.h"
+#include "mozilla/Logging.h"
+#include "nsCOMPtr.h"
+#include "nsIWebProgressListener.h"
+#include "nsString.h"
+#include "nsPrintfCString.h"
+#include "nsIChannel.h"
+#include "xptinfo.h"
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+namespace dom {
+
+static mozilla::LazyLogModule gBCWebProgressLog("BCWebProgress");
+
+static nsCString DescribeBrowsingContext(CanonicalBrowsingContext* aContext);
+static nsCString DescribeWebProgress(nsIWebProgress* aWebProgress);
+static nsCString DescribeRequest(nsIRequest* aRequest);
+static nsCString DescribeWebProgressFlags(uint32_t aFlags,
+                                          const nsACString& aPrefix);
+static nsCString DescribeError(nsresult aError);
+
+NS_IMPL_CYCLE_COLLECTION(BrowsingContextWebProgress, mCurrentBrowsingContext)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(BrowsingContextWebProgress)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(BrowsingContextWebProgress)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(BrowsingContextWebProgress)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIWebProgress)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgress)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener)
+NS_INTERFACE_MAP_END
+
+BrowsingContextWebProgress::BrowsingContextWebProgress(
+    CanonicalBrowsingContext* aBrowsingContext)
+    : mCurrentBrowsingContext(aBrowsingContext) {}
+
+BrowsingContextWebProgress::~BrowsingContextWebProgress() = default;
+
+NS_IMETHODIMP BrowsingContextWebProgress::AddProgressListener(
+    nsIWebProgressListener* aListener, uint32_t aNotifyMask) {
+  nsWeakPtr listener = do_GetWeakReference(aListener);
+  if (!listener) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (mListenerInfoList.Contains(listener)) {
+    // The listener is already registered!
+    return NS_ERROR_FAILURE;
+  }
+
+  mListenerInfoList.AppendElement(ListenerInfo(listener, aNotifyMask));
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::RemoveProgressListener(
+    nsIWebProgressListener* aListener) {
+  nsWeakPtr listener = do_GetWeakReference(aListener);
+  if (!listener) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return mListenerInfoList.RemoveElement(listener) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::GetBrowsingContextXPCOM(
+    BrowsingContext** aBrowsingContext) {
+  NS_IF_ADDREF(*aBrowsingContext = mCurrentBrowsingContext);
+  return NS_OK;
+}
+
+BrowsingContext* BrowsingContextWebProgress::GetBrowsingContext() {
+  return mCurrentBrowsingContext;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::GetDOMWindow(
+    mozIDOMWindowProxy** aDOMWindow) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::GetIsTopLevel(bool* aIsTopLevel) {
+  *aIsTopLevel = mCurrentBrowsingContext->IsTop();
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::GetIsLoadingDocument(
+    bool* aIsLoadingDocument) {
+  *aIsLoadingDocument = mIsLoadingDocument;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::GetLoadType(uint32_t* aLoadType) {
+  *aLoadType = mLoadType;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::GetTarget(nsIEventTarget** aTarget) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP BrowsingContextWebProgress::SetTarget(nsIEventTarget* aTarget) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+void BrowsingContextWebProgress::UpdateAndNotifyListeners(
+    uint32_t aFlag,
+    const std::function<void(nsIWebProgressListener*)>& aCallback) {
+  RefPtr<BrowsingContextWebProgress> kungFuDeathGrip = this;
+
+  ListenerArray::ForwardIterator iter(mListenerInfoList);
+  while (iter.HasMore()) {
+    ListenerInfo& info = iter.GetNext();
+    if (!(info.mNotifyMask & aFlag)) {
+      continue;
+    }
+
+    nsCOMPtr<nsIWebProgressListener> listener =
+        do_QueryReferent(info.mWeakListener);
+    if (!listener) {
+      mListenerInfoList.RemoveElement(info);
+      continue;
+    }
+
+    aCallback(listener);
+  }
+
+  mListenerInfoList.Compact();
+
+  // Notify the parent BrowsingContextWebProgress of the event to continue
+  // propagating.
+  auto* parent = mCurrentBrowsingContext->GetParent();
+  if (parent && parent->GetWebProgress()) {
+    aCallback(parent->GetWebProgress());
+  }
+}
+
+void BrowsingContextWebProgress::ContextDiscarded() {
+  if (!mIsLoadingDocument) {
+    return;
+  }
+
+  // If our BrowsingContext is being discarded while still loading a document,
+  // fire a synthetic `STATE_STOP` to end the ongoing load.
+  MOZ_LOG(gBCWebProgressLog, LogLevel::Info,
+          ("Discarded while loading %s",
+           DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+
+  // This matches what nsDocLoader::doStopDocumentLoad does, except we don't
+  // bother notifying for `STATE_STOP | STATE_IS_DOCUMENT`,
+  // nsBrowserStatusFilter would filter it out before it gets to the parent
+  // process.
+  nsCOMPtr<nsIRequest> request = mLoadingDocumentRequest;
+  OnStateChange(this, request, STATE_STOP | STATE_IS_WINDOW | STATE_IS_NETWORK,
+                NS_ERROR_ABORT);
+}
+
+void BrowsingContextWebProgress::ContextReplaced(
+    CanonicalBrowsingContext* aNewContext) {
+  mCurrentBrowsingContext = aNewContext;
+}
+
+already_AddRefed<BounceTrackingState>
+BrowsingContextWebProgress::GetBounceTrackingState() {
+  if (!mBounceTrackingState) {
+    mBounceTrackingState = BounceTrackingState::GetOrCreate(this);
+  }
+  return do_AddRef(mBounceTrackingState);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIWebProgressListener
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::OnStateChange(nsIWebProgress* aWebProgress,
+                                          nsIRequest* aRequest,
+                                          uint32_t aStateFlags,
+                                          nsresult aStatus) {
+  MOZ_LOG(
+      gBCWebProgressLog, LogLevel::Info,
+      ("OnStateChange(%s, %s, %s, %s) on %s",
+       DescribeWebProgress(aWebProgress).get(), DescribeRequest(aRequest).get(),
+       DescribeWebProgressFlags(aStateFlags, "STATE_"_ns).get(),
+       DescribeError(aStatus).get(),
+       DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+
+  bool targetIsThis = aWebProgress == this;
+
+  // We may receive a request from an in-process nsDocShell which doesn't have
+  // `aWebProgress == this` which we should still consider as targeting
+  // ourselves.
+  if (nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(aWebProgress);
+      docShell && docShell->GetBrowsingContext() == mCurrentBrowsingContext) {
+    targetIsThis = true;
+    aWebProgress->GetLoadType(&mLoadType);
+  }
+
+  // Track `mIsLoadingDocument` based on the notifications we've received so far
+  // if the nsIWebProgress being targeted is this one.
+  if (targetIsThis) {
+    constexpr uint32_t startFlags = nsIWebProgressListener::STATE_START |
+                                    nsIWebProgressListener::STATE_IS_DOCUMENT |
+                                    nsIWebProgressListener::STATE_IS_REQUEST |
+                                    nsIWebProgressListener::STATE_IS_WINDOW |
+                                    nsIWebProgressListener::STATE_IS_NETWORK;
+    constexpr uint32_t stopFlags = nsIWebProgressListener::STATE_STOP |
+                                   nsIWebProgressListener::STATE_IS_WINDOW;
+    constexpr uint32_t redirectFlags =
+        nsIWebProgressListener::STATE_IS_REDIRECTED_DOCUMENT;
+    if ((aStateFlags & startFlags) == startFlags) {
+      if (mIsLoadingDocument) {
+        // We received a duplicate `STATE_START` notification, silence this
+        // notification until we receive the matching `STATE_STOP` to not fire
+        // duplicate `STATE_START` notifications into frontend on process
+        // switches.
+        return NS_OK;
+      }
+      mIsLoadingDocument = true;
+
+      // Record the request we started the load with, so we can emit a synthetic
+      // `STATE_STOP` notification if the BrowsingContext is discarded before
+      // the notification arrives.
+      mLoadingDocumentRequest = aRequest;
+    } else if ((aStateFlags & stopFlags) == stopFlags) {
+      // We've received a `STATE_STOP` notification targeting this web progress,
+      // clear our loading document flag.
+      mIsLoadingDocument = false;
+      mLoadingDocumentRequest = nullptr;
+    } else if (mIsLoadingDocument &&
+               (aStateFlags & redirectFlags) == redirectFlags) {
+      // If we see a redirected document load, update the loading request which
+      // we'll emit the synthetic STATE_STOP notification with.
+      mLoadingDocumentRequest = aRequest;
+    }
+  }
+
+  UpdateAndNotifyListeners(
+      ((aStateFlags >> 16) & nsIWebProgress::NOTIFY_STATE_ALL),
+      [&](nsIWebProgressListener* listener) {
+        listener->OnStateChange(aWebProgress, aRequest, aStateFlags, aStatus);
+      });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::OnProgressChange(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             int32_t aCurSelfProgress,
+                                             int32_t aMaxSelfProgress,
+                                             int32_t aCurTotalProgress,
+                                             int32_t aMaxTotalProgress) {
+  MOZ_LOG(
+      gBCWebProgressLog, LogLevel::Info,
+      ("OnProgressChange(%s, %s, %d, %d, %d, %d) on %s",
+       DescribeWebProgress(aWebProgress).get(), DescribeRequest(aRequest).get(),
+       aCurSelfProgress, aMaxSelfProgress, aCurTotalProgress, aMaxTotalProgress,
+       DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+  UpdateAndNotifyListeners(
+      nsIWebProgress::NOTIFY_PROGRESS, [&](nsIWebProgressListener* listener) {
+        listener->OnProgressChange(aWebProgress, aRequest, aCurSelfProgress,
+                                   aMaxSelfProgress, aCurTotalProgress,
+                                   aMaxTotalProgress);
+      });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::OnLocationChange(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             nsIURI* aLocation,
+                                             uint32_t aFlags) {
+  MOZ_LOG(
+      gBCWebProgressLog, LogLevel::Info,
+      ("OnLocationChange(%s, %s, %s, %s) on %s",
+       DescribeWebProgress(aWebProgress).get(), DescribeRequest(aRequest).get(),
+       aLocation ? aLocation->GetSpecOrDefault().get() : "<null>",
+       DescribeWebProgressFlags(aFlags, "LOCATION_CHANGE_"_ns).get(),
+       DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+  UpdateAndNotifyListeners(
+      nsIWebProgress::NOTIFY_LOCATION, [&](nsIWebProgressListener* listener) {
+        listener->OnLocationChange(aWebProgress, aRequest, aLocation, aFlags);
+      });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::OnStatusChange(nsIWebProgress* aWebProgress,
+                                           nsIRequest* aRequest,
+                                           nsresult aStatus,
+                                           const char16_t* aMessage) {
+  MOZ_LOG(
+      gBCWebProgressLog, LogLevel::Info,
+      ("OnStatusChange(%s, %s, %s, \"%s\") on %s",
+       DescribeWebProgress(aWebProgress).get(), DescribeRequest(aRequest).get(),
+       DescribeError(aStatus).get(), NS_ConvertUTF16toUTF8(aMessage).get(),
+       DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+  UpdateAndNotifyListeners(
+      nsIWebProgress::NOTIFY_STATUS, [&](nsIWebProgressListener* listener) {
+        listener->OnStatusChange(aWebProgress, aRequest, aStatus, aMessage);
+      });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::OnSecurityChange(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             uint32_t aState) {
+  MOZ_LOG(
+      gBCWebProgressLog, LogLevel::Info,
+      ("OnSecurityChange(%s, %s, %x) on %s",
+       DescribeWebProgress(aWebProgress).get(), DescribeRequest(aRequest).get(),
+       aState, DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+  UpdateAndNotifyListeners(
+      nsIWebProgress::NOTIFY_SECURITY, [&](nsIWebProgressListener* listener) {
+        listener->OnSecurityChange(aWebProgress, aRequest, aState);
+      });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                                   nsIRequest* aRequest,
+                                                   uint32_t aEvent) {
+  MOZ_LOG(
+      gBCWebProgressLog, LogLevel::Info,
+      ("OnContentBlockingEvent(%s, %s, %x) on %s",
+       DescribeWebProgress(aWebProgress).get(), DescribeRequest(aRequest).get(),
+       aEvent, DescribeBrowsingContext(mCurrentBrowsingContext).get()));
+  UpdateAndNotifyListeners(nsIWebProgress::NOTIFY_CONTENT_BLOCKING,
+                           [&](nsIWebProgressListener* listener) {
+                             listener->OnContentBlockingEvent(aWebProgress,
+                                                              aRequest, aEvent);
+                           });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowsingContextWebProgress::GetDocumentRequest(nsIRequest** aRequest) {
+  NS_IF_ADDREF(*aRequest = mLoadingDocumentRequest);
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Helper methods for notification logging
+
+static nsCString DescribeBrowsingContext(CanonicalBrowsingContext* aContext) {
+  if (!aContext) {
+    return "<null>"_ns;
+  }
+
+  nsCOMPtr<nsIURI> currentURI = aContext->GetCurrentURI();
+  return nsPrintfCString(
+      "{top:%d, id:%" PRIx64 ", url:%s}", aContext->IsTop(), aContext->Id(),
+      currentURI ? currentURI->GetSpecOrDefault().get() : "<null>");
+}
+
+static nsCString DescribeWebProgress(nsIWebProgress* aWebProgress) {
+  if (!aWebProgress) {
+    return "<null>"_ns;
+  }
+
+  bool isTopLevel = false;
+  aWebProgress->GetIsTopLevel(&isTopLevel);
+  bool isLoadingDocument = false;
+  aWebProgress->GetIsLoadingDocument(&isLoadingDocument);
+  return nsPrintfCString("{isTopLevel:%d, isLoadingDocument:%d}", isTopLevel,
+                         isLoadingDocument);
+}
+
+static nsCString DescribeRequest(nsIRequest* aRequest) {
+  if (!aRequest) {
+    return "<null>"_ns;
+  }
+
+  nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);
+  if (!channel) {
+    return "<non-channel>"_ns;
+  }
+
+  nsCOMPtr<nsIURI> originalURI;
+  channel->GetOriginalURI(getter_AddRefs(originalURI));
+  nsCOMPtr<nsIURI> uri;
+  channel->GetURI(getter_AddRefs(uri));
+
+  return nsPrintfCString(
+      "{URI:%s, originalURI:%s}",
+      uri ? uri->GetSpecOrDefault().get() : "<null>",
+      originalURI ? originalURI->GetSpecOrDefault().get() : "<null>");
+}
+
+static nsCString DescribeWebProgressFlags(uint32_t aFlags,
+                                          const nsACString& aPrefix) {
+  nsCString flags;
+  uint32_t remaining = aFlags;
+
+  // Hackily fetch the names of each constant from the XPT information used for
+  // reflecting it into JS. This doesn't need to be reliable and just exists as
+  // a logging aid.
+  //
+  // If a change to xpt in the future breaks this code, just delete it and
+  // replace it with a normal hex log.
+  if (const auto* ifaceInfo =
+          nsXPTInterfaceInfo::ByIID(NS_GET_IID(nsIWebProgressListener))) {
+    for (uint16_t i = 0; i < ifaceInfo->ConstantCount(); ++i) {
+      const auto& constInfo = ifaceInfo->Constant(i);
+      nsDependentCString name(constInfo.Name());
+      if (!StringBeginsWith(name, aPrefix)) {
+        continue;
+      }
+
+      if (remaining & constInfo.mValue) {
+        remaining &= ~constInfo.mValue;
+        if (!flags.IsEmpty()) {
+          flags.AppendLiteral("|");
+        }
+        flags.Append(name);
+      }
+    }
+  }
+  if (remaining != 0 || flags.IsEmpty()) {
+    if (!flags.IsEmpty()) {
+      flags.AppendLiteral("|");
+    }
+    flags.AppendInt(remaining, 16);
+  }
+  return flags;
+}
+
+static nsCString DescribeError(nsresult aError) {
+  nsCString name;
+  GetErrorName(aError, name);
+  return name;
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/docshell/base/BrowsingContextWebProgress.h b/docshell/base/BrowsingContextWebProgress.h
new file mode 100644
index 0000000000..81610886b9
--- /dev/null
+++ b/docshell/base/BrowsingContextWebProgress.h
@@ -0,0 +1,103 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BrowsingContextWebProgress_h
+#define mozilla_dom_BrowsingContextWebProgress_h
+
+#include "nsIWebProgress.h"
+#include "nsIWebProgressListener.h"
+#include "nsTObserverArray.h"
+#include "nsWeakReference.h"
+#include "nsCycleCollectionParticipant.h"
+#include "mozilla/BounceTrackingState.h"
+
+namespace mozilla::dom {
+
+class CanonicalBrowsingContext;
+
+/// Object acting as the nsIWebProgress instance for a BrowsingContext over its
+/// lifetime.
+///
+/// An active toplevel CanonicalBrowsingContext will always have a
+/// BrowsingContextWebProgress, which will be moved between contexts as
+/// BrowsingContextGroup-changing loads are performed.
+///
+/// Subframes will only have a `BrowsingContextWebProgress` if they are loaded
+/// in a content process, and will use the nsDocShell instead if they are loaded
+/// in the parent process, as parent process documents cannot have or be
+/// out-of-process iframes.
+class BrowsingContextWebProgress final : public nsIWebProgress,
+                                         public nsIWebProgressListener {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(BrowsingContextWebProgress,
+                                           nsIWebProgress)
+  NS_DECL_NSIWEBPROGRESS
+  NS_DECL_NSIWEBPROGRESSLISTENER
+
+  explicit BrowsingContextWebProgress(
+      CanonicalBrowsingContext* aBrowsingContext);
+
+  struct ListenerInfo {
+    ListenerInfo(nsIWeakReference* aListener, unsigned long aNotifyMask)
+        : mWeakListener(aListener), mNotifyMask(aNotifyMask) {}
+
+    bool operator==(const ListenerInfo& aOther) const {
+      return mWeakListener == aOther.mWeakListener;
+    }
+    bool operator==(const nsWeakPtr& aOther) const {
+      return mWeakListener == aOther;
+    }
+
+    // Weak pointer for the nsIWebProgressListener...
+    nsWeakPtr mWeakListener;
+
+    // Mask indicating which notifications the listener wants to receive.
+    unsigned long mNotifyMask;
+  };
+
+  void ContextDiscarded();
+  void ContextReplaced(CanonicalBrowsingContext* aNewContext);
+
+  void SetLoadType(uint32_t aLoadType) { mLoadType = aLoadType; }
+
+  already_AddRefed<BounceTrackingState> GetBounceTrackingState();
+
+ private:
+  virtual ~BrowsingContextWebProgress();
+
+  void UpdateAndNotifyListeners(
+      uint32_t aFlag,
+      const std::function<void(nsIWebProgressListener*)>& aCallback);
+
+  using ListenerArray = nsAutoTObserverArray<ListenerInfo, 4>;
+  ListenerArray mListenerInfoList;
+
+  // The current BrowsingContext which owns this BrowsingContextWebProgress.
+  // This context may change during navigations and may not be fully attached at
+  // all times.
+  RefPtr<CanonicalBrowsingContext> mCurrentBrowsingContext;
+
+  // The current request being actively loaded by the BrowsingContext. Only set
+  // while mIsLoadingDocument is true, and is used to fire STATE_STOP
+  // notifications if the BrowsingContext is discarded while the load is
+  // ongoing.
+  nsCOMPtr<nsIRequest> mLoadingDocumentRequest;
+
+  // The most recent load type observed for this BrowsingContextWebProgress.
+  uint32_t mLoadType = 0;
+
+  // Are we currently in the process of loading a document? This is true between
+  // the `STATE_START` notification from content and the `STATE_STOP`
+  // notification being received. Duplicate `STATE_START` events may be
+  // discarded while loading a document to avoid noise caused by process
+  // switches.
+  bool mIsLoadingDocument = false;
+
+  RefPtr<mozilla::BounceTrackingState> mBounceTrackingState;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_BrowsingContextWebProgress_h
diff --git a/docshell/base/CanonicalBrowsingContext.cpp b/docshell/base/CanonicalBrowsingContext.cpp
new file mode 100644
index 0000000000..33ed5aab28
--- /dev/null
+++ b/docshell/base/CanonicalBrowsingContext.cpp
@@ -0,0 +1,3104 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+
+#include "ErrorList.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/AsyncEventDispatcher.h"
+#include "mozilla/dom/BrowserParent.h"
+#include "mozilla/dom/BrowsingContextBinding.h"
+#include "mozilla/dom/BrowsingContextGroup.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/EventTarget.h"
+#include "mozilla/dom/PBrowserParent.h"
+#include "mozilla/dom/PBackgroundSessionStorageCache.h"
+#include "mozilla/dom/PWindowGlobalParent.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/Promise-inl.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/dom/ContentProcessManager.h"
+#include "mozilla/dom/MediaController.h"
+#include "mozilla/dom/MediaControlService.h"
+#include "mozilla/dom/ContentPlaybackController.h"
+#include "mozilla/dom/SessionStorageManager.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/layers/CompositorBridgeChild.h"
+#ifdef NS_PRINTING
+#  include "mozilla/layout/RemotePrintJobParent.h"
+#endif
+#include "mozilla/net/DocumentLoadListener.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/StaticPrefs_docshell.h"
+#include "mozilla/StaticPrefs_fission.h"
+#include "mozilla/Telemetry.h"
+#include "nsILayoutHistoryState.h"
+#include "nsIPrintSettings.h"
+#include "nsIPrintSettingsService.h"
+#include "nsISupports.h"
+#include "nsIWebNavigation.h"
+#include "nsDocShell.h"
+#include "nsFrameLoader.h"
+#include "nsFrameLoaderOwner.h"
+#include "nsGlobalWindowOuter.h"
+#include "nsIWebBrowserChrome.h"
+#include "nsIXULRuntime.h"
+#include "nsNetUtil.h"
+#include "nsSHistory.h"
+#include "nsSecureBrowserUI.h"
+#include "nsQueryObject.h"
+#include "nsBrowserStatusFilter.h"
+#include "nsIBrowser.h"
+#include "nsTHashSet.h"
+#include "SessionStoreFunctions.h"
+#include "nsIXPConnect.h"
+#include "nsImportModule.h"
+#include "UnitTransforms.h"
+
+using namespace mozilla::ipc;
+
+extern mozilla::LazyLogModule gAutoplayPermissionLog;
+extern mozilla::LazyLogModule gSHLog;
+extern mozilla::LazyLogModule gSHIPBFCacheLog;
+
+#define AUTOPLAY_LOG(msg, ...) \
+  MOZ_LOG(gAutoplayPermissionLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
+static mozilla::LazyLogModule sPBContext("PBContext");
+
+// Global count of canonical browsing contexts with the private attribute set
+static uint32_t gNumberOfPrivateContexts = 0;
+
+// Current parent process epoch for parent initiated navigations
+static uint64_t gParentInitiatedNavigationEpoch = 0;
+
+static void IncreasePrivateCount() {
+  gNumberOfPrivateContexts++;
+  MOZ_LOG(sPBContext, mozilla::LogLevel::Debug,
+          ("%s: Private browsing context count %d -> %d", __func__,
+           gNumberOfPrivateContexts - 1, gNumberOfPrivateContexts));
+  if (gNumberOfPrivateContexts > 1) {
+    return;
+  }
+
+  static bool sHasSeenPrivateContext = false;
+  if (!sHasSeenPrivateContext) {
+    sHasSeenPrivateContext = true;
+    mozilla::Telemetry::ScalarSet(
+        mozilla::Telemetry::ScalarID::DOM_PARENTPROCESS_PRIVATE_WINDOW_USED,
+        true);
+  }
+}
+
+static void DecreasePrivateCount() {
+  MOZ_ASSERT(gNumberOfPrivateContexts > 0);
+  gNumberOfPrivateContexts--;
+
+  MOZ_LOG(sPBContext, mozilla::LogLevel::Debug,
+          ("%s: Private browsing context count %d -> %d", __func__,
+           gNumberOfPrivateContexts + 1, gNumberOfPrivateContexts));
+  if (!gNumberOfPrivateContexts &&
+      !mozilla::StaticPrefs::browser_privatebrowsing_autostart()) {
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+    if (observerService) {
+      MOZ_LOG(sPBContext, mozilla::LogLevel::Debug,
+              ("%s: last-pb-context-exited fired", __func__));
+      observerService->NotifyObservers(nullptr, "last-pb-context-exited",
+                                       nullptr);
+    }
+  }
+}
+
+namespace mozilla::dom {
+
+extern mozilla::LazyLogModule gUserInteractionPRLog;
+
+#define USER_ACTIVATION_LOG(msg, ...) \
+  MOZ_LOG(gUserInteractionPRLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
+CanonicalBrowsingContext::CanonicalBrowsingContext(WindowContext* aParentWindow,
+                                                   BrowsingContextGroup* aGroup,
+                                                   uint64_t aBrowsingContextId,
+                                                   uint64_t aOwnerProcessId,
+                                                   uint64_t aEmbedderProcessId,
+                                                   BrowsingContext::Type aType,
+                                                   FieldValues&& aInit)
+    : BrowsingContext(aParentWindow, aGroup, aBrowsingContextId, aType,
+                      std::move(aInit)),
+      mProcessId(aOwnerProcessId),
+      mEmbedderProcessId(aEmbedderProcessId),
+      mPermanentKey(JS::NullValue()) {
+  // You are only ever allowed to create CanonicalBrowsingContexts in the
+  // parent process.
+  MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+
+  // The initial URI in a BrowsingContext is always "about:blank".
+  MOZ_ALWAYS_SUCCEEDS(
+      NS_NewURI(getter_AddRefs(mCurrentRemoteURI), "about:blank"));
+
+  mozilla::HoldJSObjects(this);
+}
+
+CanonicalBrowsingContext::~CanonicalBrowsingContext() {
+  mPermanentKey.setNull();
+
+  mozilla::DropJSObjects(this);
+
+  if (mSessionHistory) {
+    mSessionHistory->SetBrowsingContext(nullptr);
+  }
+}
+
+/* static */
+already_AddRefed<CanonicalBrowsingContext> CanonicalBrowsingContext::Get(
+    uint64_t aId) {
+  MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+  return BrowsingContext::Get(aId).downcast<CanonicalBrowsingContext>();
+}
+
+/* static */
+CanonicalBrowsingContext* CanonicalBrowsingContext::Cast(
+    BrowsingContext* aContext) {
+  MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+  return static_cast<CanonicalBrowsingContext*>(aContext);
+}
+
+/* static */
+const CanonicalBrowsingContext* CanonicalBrowsingContext::Cast(
+    const BrowsingContext* aContext) {
+  MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+  return static_cast<const CanonicalBrowsingContext*>(aContext);
+}
+
+already_AddRefed<CanonicalBrowsingContext> CanonicalBrowsingContext::Cast(
+    already_AddRefed<BrowsingContext>&& aContext) {
+  MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+  return aContext.downcast<CanonicalBrowsingContext>();
+}
+
+ContentParent* CanonicalBrowsingContext::GetContentParent() const {
+  if (mProcessId == 0) {
+    return nullptr;
+  }
+
+  ContentProcessManager* cpm = ContentProcessManager::GetSingleton();
+  if (!cpm) {
+    return nullptr;
+  }
+  return cpm->GetContentProcessById(ContentParentId(mProcessId));
+}
+
+void CanonicalBrowsingContext::GetCurrentRemoteType(nsACString& aRemoteType,
+                                                    ErrorResult& aRv) const {
+  // If we're in the parent process, dump out the void string.
+  if (mProcessId == 0) {
+    aRemoteType = NOT_REMOTE_TYPE;
+    return;
+  }
+
+  ContentParent* cp = GetContentParent();
+  if (!cp) {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+    return;
+  }
+
+  aRemoteType = cp->GetRemoteType();
+}
+
+void CanonicalBrowsingContext::SetOwnerProcessId(uint64_t aProcessId) {
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("SetOwnerProcessId for 0x%08" PRIx64 " (0x%08" PRIx64
+           " -> 0x%08" PRIx64 ")",
+           Id(), mProcessId, aProcessId));
+
+  mProcessId = aProcessId;
+}
+
+nsISecureBrowserUI* CanonicalBrowsingContext::GetSecureBrowserUI() {
+  if (!IsTop()) {
+    return nullptr;
+  }
+  if (!mSecureBrowserUI) {
+    mSecureBrowserUI = new nsSecureBrowserUI(this);
+  }
+  return mSecureBrowserUI;
+}
+
+namespace {
+// The DocShellProgressBridge is attached to a root content docshell loaded in
+// the parent process. Notifications are paired up with the docshell which they
+// came from, so that they can be fired to the correct
+// BrowsingContextWebProgress and bubble through this tree separately.
+//
+// Notifications are filtered by a nsBrowserStatusFilter before being received
+// by the DocShellProgressBridge.
+class DocShellProgressBridge : public nsIWebProgressListener {
+ public:
+  NS_DECL_ISUPPORTS
+  // NOTE: This relies in the expansion of `NS_FORWARD_SAFE` and all listener
+  // methods accepting an `aWebProgress` argument. If this changes in the
+  // future, this may need to be written manually.
+  NS_FORWARD_SAFE_NSIWEBPROGRESSLISTENER(GetTargetContext(aWebProgress))
+
+  explicit DocShellProgressBridge(uint64_t aTopContextId)
+      : mTopContextId(aTopContextId) {}
+
+ private:
+  virtual ~DocShellProgressBridge() = default;
+
+  nsIWebProgressListener* GetTargetContext(nsIWebProgress* aWebProgress) {
+    RefPtr<CanonicalBrowsingContext> context;
+    if (nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(aWebProgress)) {
+      context = docShell->GetBrowsingContext()->Canonical();
+    } else {
+      context = CanonicalBrowsingContext::Get(mTopContextId);
+    }
+    return context && !context->IsDiscarded() ? context->GetWebProgress()
+                                              : nullptr;
+  }
+
+  uint64_t mTopContextId = 0;
+};
+
+NS_IMPL_ISUPPORTS(DocShellProgressBridge, nsIWebProgressListener)
+}  // namespace
+
+void CanonicalBrowsingContext::MaybeAddAsProgressListener(
+    nsIWebProgress* aWebProgress) {
+  // Only add as a listener if the created docshell is a toplevel content
+  // docshell. We'll get notifications for all of our subframes through a single
+  // listener.
+  if (!IsTopContent()) {
+    return;
+  }
+
+  if (!mDocShellProgressBridge) {
+    mDocShellProgressBridge = new DocShellProgressBridge(Id());
+    mStatusFilter = new nsBrowserStatusFilter();
+    mStatusFilter->AddProgressListener(mDocShellProgressBridge,
+                                       nsIWebProgress::NOTIFY_ALL);
+  }
+
+  aWebProgress->AddProgressListener(mStatusFilter, nsIWebProgress::NOTIFY_ALL);
+}
+
+void CanonicalBrowsingContext::ReplacedBy(
+    CanonicalBrowsingContext* aNewContext,
+    const NavigationIsolationOptions& aRemotenessOptions) {
+  MOZ_ASSERT(!aNewContext->mWebProgress);
+  MOZ_ASSERT(!aNewContext->mSessionHistory);
+  MOZ_ASSERT(IsTop() && aNewContext->IsTop());
+
+  mIsReplaced = true;
+  aNewContext->mIsReplaced = false;
+
+  if (mStatusFilter) {
+    mStatusFilter->RemoveProgressListener(mDocShellProgressBridge);
+    mStatusFilter = nullptr;
+  }
+
+  mWebProgress->ContextReplaced(aNewContext);
+  aNewContext->mWebProgress = std::move(mWebProgress);
+
+  // Use the Transaction for the fields which need to be updated whether or not
+  // the new context has been attached before.
+  // SetWithoutSyncing can be used if context hasn't been attached.
+  Transaction txn;
+  txn.SetBrowserId(GetBrowserId());
+  txn.SetIsAppTab(GetIsAppTab());
+  txn.SetHasSiblings(GetHasSiblings());
+  txn.SetHistoryID(GetHistoryID());
+  txn.SetExplicitActive(GetExplicitActive());
+  txn.SetEmbedderColorSchemes(GetEmbedderColorSchemes());
+  txn.SetHasRestoreData(GetHasRestoreData());
+  txn.SetShouldDelayMediaFromStart(GetShouldDelayMediaFromStart());
+  txn.SetForceOffline(GetForceOffline());
+
+  // Propagate some settings on BrowsingContext replacement so they're not lost
+  // on bfcached navigations. These are important for GeckoView (see bug
+  // 1781936).
+  txn.SetAllowJavascript(GetAllowJavascript());
+  txn.SetForceEnableTrackingProtection(GetForceEnableTrackingProtection());
+  txn.SetUserAgentOverride(GetUserAgentOverride());
+  txn.SetSuspendMediaWhenInactive(GetSuspendMediaWhenInactive());
+  txn.SetDisplayMode(GetDisplayMode());
+  txn.SetForceDesktopViewport(GetForceDesktopViewport());
+  txn.SetIsUnderHiddenEmbedderElement(GetIsUnderHiddenEmbedderElement());
+
+  // When using site-specific zoom, we let the front-end manage it, otherwise it
+  // can cause weirdness like bug 1846141.
+  if (!StaticPrefs::browser_zoom_siteSpecific()) {
+    txn.SetFullZoom(GetFullZoom());
+    txn.SetTextZoom(GetTextZoom());
+  }
+
+  // Propagate the default load flags so that the TRR mode flags are forwarded
+  // to the new browsing context. See bug 1828643.
+  txn.SetDefaultLoadFlags(GetDefaultLoadFlags());
+
+  // As this is a different BrowsingContext, set InitialSandboxFlags to the
+  // current flags in the new context so that they also apply to any initial
+  // about:blank documents created in it.
+  txn.SetSandboxFlags(GetSandboxFlags());
+  txn.SetInitialSandboxFlags(GetSandboxFlags());
+  txn.SetTargetTopLevelLinkClicksToBlankInternal(
+      TargetTopLevelLinkClicksToBlank());
+  if (aNewContext->EverAttached()) {
+    MOZ_ALWAYS_SUCCEEDS(txn.Commit(aNewContext));
+  } else {
+    txn.CommitWithoutSyncing(aNewContext);
+  }
+
+  aNewContext->mRestoreState = mRestoreState.forget();
+  MOZ_ALWAYS_SUCCEEDS(SetHasRestoreData(false));
+
+  // XXXBFCache name handling is still a bit broken in Fission in general,
+  // at least in case name should be cleared.
+  if (aRemotenessOptions.mTryUseBFCache) {
+    MOZ_ASSERT(!aNewContext->EverAttached());
+    aNewContext->mFields.SetWithoutSyncing<IDX_Name>(GetName());
+    // We don't copy over HasLoadedNonInitialDocument here, we'll actually end
+    // up loading a new initial document at this point, before the real load.
+    // The real load will then end up setting HasLoadedNonInitialDocument to
+    // true.
+  }
+
+  if (mSessionHistory) {
+    mSessionHistory->SetBrowsingContext(aNewContext);
+    // At this point we will be creating a new ChildSHistory in the child.
+    // That means that the child's epoch will be reset, so it makes sense to
+    // reset the epoch in the parent too.
+    mSessionHistory->SetEpoch(0, Nothing());
+    mSessionHistory.swap(aNewContext->mSessionHistory);
+    RefPtr<ChildSHistory> childSHistory = ForgetChildSHistory();
+    aNewContext->SetChildSHistory(childSHistory);
+  }
+
+  BackgroundSessionStorageManager::PropagateManager(Id(), aNewContext->Id());
+
+  // Transfer the ownership of the priority active status from the old context
+  // to the new context.
+  aNewContext->mPriorityActive = mPriorityActive;
+  mPriorityActive = false;
+
+  MOZ_ASSERT(aNewContext->mLoadingEntries.IsEmpty());
+  mLoadingEntries.SwapElements(aNewContext->mLoadingEntries);
+  MOZ_ASSERT(!aNewContext->mActiveEntry);
+  mActiveEntry.swap(aNewContext->mActiveEntry);
+
+  aNewContext->mPermanentKey = mPermanentKey;
+  mPermanentKey.setNull();
+}
+
+void CanonicalBrowsingContext::UpdateSecurityState() {
+  if (mSecureBrowserUI) {
+    mSecureBrowserUI->RecomputeSecurityFlags();
+  }
+}
+
+void CanonicalBrowsingContext::GetWindowGlobals(
+    nsTArray<RefPtr<WindowGlobalParent>>& aWindows) {
+  aWindows.SetCapacity(GetWindowContexts().Length());
+  for (auto& window : GetWindowContexts()) {
+    aWindows.AppendElement(static_cast<WindowGlobalParent*>(window.get()));
+  }
+}
+
+WindowGlobalParent* CanonicalBrowsingContext::GetCurrentWindowGlobal() const {
+  return static_cast<WindowGlobalParent*>(GetCurrentWindowContext());
+}
+
+WindowGlobalParent* CanonicalBrowsingContext::GetParentWindowContext() {
+  return static_cast<WindowGlobalParent*>(
+      BrowsingContext::GetParentWindowContext());
+}
+
+WindowGlobalParent* CanonicalBrowsingContext::GetTopWindowContext() {
+  return static_cast<WindowGlobalParent*>(
+      BrowsingContext::GetTopWindowContext());
+}
+
+already_AddRefed<nsIWidget>
+CanonicalBrowsingContext::GetParentProcessWidgetContaining() {
+  // If our document is loaded in-process, such as chrome documents, get the
+  // widget directly from our outer window. Otherwise, try to get the widget
+  // from the toplevel content's browser's element.
+  nsCOMPtr<nsIWidget> widget;
+  if (nsGlobalWindowOuter* window = nsGlobalWindowOuter::Cast(GetDOMWindow())) {
+    widget = window->GetNearestWidget();
+  } else if (Element* topEmbedder = Top()->GetEmbedderElement()) {
+    widget = nsContentUtils::WidgetForContent(topEmbedder);
+    if (!widget) {
+      widget = nsContentUtils::WidgetForDocument(topEmbedder->OwnerDoc());
+    }
+  }
+
+  if (widget) {
+    widget = widget->GetTopLevelWidget();
+  }
+
+  return widget.forget();
+}
+
+already_AddRefed<nsIBrowserDOMWindow>
+CanonicalBrowsingContext::GetBrowserDOMWindow() {
+  RefPtr<CanonicalBrowsingContext> chromeTop = TopCrossChromeBoundary();
+  nsGlobalWindowOuter* topWin;
+  if ((topWin = nsGlobalWindowOuter::Cast(chromeTop->GetDOMWindow())) &&
+      topWin->IsChromeWindow()) {
+    return do_AddRef(topWin->GetBrowserDOMWindow());
+  }
+  return nullptr;
+}
+
+already_AddRefed<WindowGlobalParent>
+CanonicalBrowsingContext::GetEmbedderWindowGlobal() const {
+  uint64_t windowId = GetEmbedderInnerWindowId();
+  if (windowId == 0) {
+    return nullptr;
+  }
+
+  return WindowGlobalParent::GetByInnerWindowId(windowId);
+}
+
+CanonicalBrowsingContext*
+CanonicalBrowsingContext::GetParentCrossChromeBoundary() {
+  if (GetParent()) {
+    return Cast(GetParent());
+  }
+  if (auto* embedder = GetEmbedderElement()) {
+    return Cast(embedder->OwnerDoc()->GetBrowsingContext());
+  }
+  return nullptr;
+}
+
+CanonicalBrowsingContext* CanonicalBrowsingContext::TopCrossChromeBoundary() {
+  CanonicalBrowsingContext* bc = this;
+  while (auto* parent = bc->GetParentCrossChromeBoundary()) {
+    bc = parent;
+  }
+  return bc;
+}
+
+Nullable<WindowProxyHolder> CanonicalBrowsingContext::GetTopChromeWindow() {
+  RefPtr<CanonicalBrowsingContext> bc = TopCrossChromeBoundary();
+  if (bc->IsChrome()) {
+    return WindowProxyHolder(bc.forget());
+  }
+  return nullptr;
+}
+
+nsISHistory* CanonicalBrowsingContext::GetSessionHistory() {
+  if (!IsTop()) {
+    return Cast(Top())->GetSessionHistory();
+  }
+
+  // Check GetChildSessionHistory() to make sure that this BrowsingContext has
+  // session history enabled.
+  if (!mSessionHistory && GetChildSessionHistory()) {
+    mSessionHistory = new nsSHistory(this);
+  }
+
+  return mSessionHistory;
+}
+
+SessionHistoryEntry* CanonicalBrowsingContext::GetActiveSessionHistoryEntry() {
+  return mActiveEntry;
+}
+
+void CanonicalBrowsingContext::SetActiveSessionHistoryEntry(
+    SessionHistoryEntry* aEntry) {
+  mActiveEntry = aEntry;
+}
+
+bool CanonicalBrowsingContext::HasHistoryEntry(nsISHEntry* aEntry) {
+  // XXX Should we check also loading entries?
+  return aEntry && mActiveEntry == aEntry;
+}
+
+void CanonicalBrowsingContext::SwapHistoryEntries(nsISHEntry* aOldEntry,
+                                                  nsISHEntry* aNewEntry) {
+  // XXX Should we check also loading entries?
+  if (mActiveEntry == aOldEntry) {
+    nsCOMPtr<SessionHistoryEntry> newEntry = do_QueryInterface(aNewEntry);
+    mActiveEntry = newEntry.forget();
+  }
+}
+
+void CanonicalBrowsingContext::AddLoadingSessionHistoryEntry(
+    uint64_t aLoadId, SessionHistoryEntry* aEntry) {
+  Unused << SetHistoryID(aEntry->DocshellID());
+  mLoadingEntries.AppendElement(LoadingSessionHistoryEntry{aLoadId, aEntry});
+}
+
+void CanonicalBrowsingContext::GetLoadingSessionHistoryInfoFromParent(
+    Maybe<LoadingSessionHistoryInfo>& aLoadingInfo) {
+  nsISHistory* shistory = GetSessionHistory();
+  if (!shistory || !GetParent()) {
+    return;
+  }
+
+  SessionHistoryEntry* parentSHE =
+      GetParent()->Canonical()->GetActiveSessionHistoryEntry();
+  if (parentSHE) {
+    int32_t index = -1;
+    for (BrowsingContext* sibling : GetParent()->Children()) {
+      ++index;
+      if (sibling == this) {
+        nsCOMPtr<nsISHEntry> shEntry;
+        parentSHE->GetChildSHEntryIfHasNoDynamicallyAddedChild(
+            index, getter_AddRefs(shEntry));
+        nsCOMPtr<SessionHistoryEntry> she = do_QueryInterface(shEntry);
+        if (she) {
+          aLoadingInfo.emplace(she);
+          mLoadingEntries.AppendElement(LoadingSessionHistoryEntry{
+              aLoadingInfo.value().mLoadId, she.get()});
+          Unused << SetHistoryID(she->DocshellID());
+        }
+        break;
+      }
+    }
+  }
+}
+
+UniquePtr<LoadingSessionHistoryInfo>
+CanonicalBrowsingContext::CreateLoadingSessionHistoryEntryForLoad(
+    nsDocShellLoadState* aLoadState, SessionHistoryEntry* existingEntry,
+    nsIChannel* aChannel) {
+  RefPtr<SessionHistoryEntry> entry;
+  const LoadingSessionHistoryInfo* existingLoadingInfo =
+      aLoadState->GetLoadingSessionHistoryInfo();
+  MOZ_ASSERT_IF(!existingLoadingInfo, !existingEntry);
+  if (existingLoadingInfo) {
+    if (existingEntry) {
+      entry = existingEntry;
+    } else {
+      MOZ_ASSERT(!existingLoadingInfo->mLoadIsFromSessionHistory);
+
+      SessionHistoryEntry::LoadingEntry* loadingEntry =
+          SessionHistoryEntry::GetByLoadId(existingLoadingInfo->mLoadId);
+      MOZ_LOG(gSHLog, LogLevel::Verbose,
+              ("SHEntry::GetByLoadId(%" PRIu64 ") -> %p",
+               existingLoadingInfo->mLoadId, entry.get()));
+      if (!loadingEntry) {
+        return nullptr;
+      }
+      entry = loadingEntry->mEntry;
+    }
+
+    // If the entry was updated, update also the LoadingSessionHistoryInfo.
+    UniquePtr<LoadingSessionHistoryInfo> lshi =
+        MakeUnique<LoadingSessionHistoryInfo>(entry, existingLoadingInfo);
+    aLoadState->SetLoadingSessionHistoryInfo(std::move(lshi));
+    existingLoadingInfo = aLoadState->GetLoadingSessionHistoryInfo();
+    Unused << SetHistoryEntryCount(entry->BCHistoryLength());
+  } else if (aLoadState->LoadType() == LOAD_REFRESH &&
+             !ShouldAddEntryForRefresh(aLoadState->URI(),
+                                       aLoadState->PostDataStream()) &&
+             mActiveEntry) {
+    entry = mActiveEntry;
+  } else {
+    entry = new SessionHistoryEntry(aLoadState, aChannel);
+    if (IsTop()) {
+      // Only top level pages care about Get/SetPersist.
+      entry->SetPersist(
+          nsDocShell::ShouldAddToSessionHistory(aLoadState->URI(), aChannel));
+    } else if (mActiveEntry || !mLoadingEntries.IsEmpty()) {
+      entry->SetIsSubFrame(true);
+    }
+    entry->SetDocshellID(GetHistoryID());
+    entry->SetIsDynamicallyAdded(CreatedDynamically());
+    entry->SetForInitialLoad(true);
+  }
+  MOZ_DIAGNOSTIC_ASSERT(entry);
+
+  UniquePtr<LoadingSessionHistoryInfo> loadingInfo;
+  if (existingLoadingInfo) {
+    loadingInfo = MakeUnique<LoadingSessionHistoryInfo>(*existingLoadingInfo);
+  } else {
+    loadingInfo = MakeUnique<LoadingSessionHistoryInfo>(entry);
+    mLoadingEntries.AppendElement(
+        LoadingSessionHistoryEntry{loadingInfo->mLoadId, entry});
+  }
+
+  MOZ_ASSERT(SessionHistoryEntry::GetByLoadId(loadingInfo->mLoadId)->mEntry ==
+             entry);
+
+  return loadingInfo;
+}
+
+UniquePtr<LoadingSessionHistoryInfo>
+CanonicalBrowsingContext::ReplaceLoadingSessionHistoryEntryForLoad(
+    LoadingSessionHistoryInfo* aInfo, nsIChannel* aNewChannel) {
+  MOZ_ASSERT(aInfo);
+  MOZ_ASSERT(aNewChannel);
+
+  SessionHistoryInfo newInfo = SessionHistoryInfo(
+      aNewChannel, aInfo->mInfo.LoadType(),
+      aInfo->mInfo.GetPartitionedPrincipalToInherit(), aInfo->mInfo.GetCsp());
+
+  for (size_t i = 0; i < mLoadingEntries.Length(); ++i) {
+    if (mLoadingEntries[i].mLoadId == aInfo->mLoadId) {
+      RefPtr<SessionHistoryEntry> loadingEntry = mLoadingEntries[i].mEntry;
+      loadingEntry->SetInfo(&newInfo);
+
+      if (IsTop()) {
+        // Only top level pages care about Get/SetPersist.
+        nsCOMPtr<nsIURI> uri;
+        aNewChannel->GetURI(getter_AddRefs(uri));
+        loadingEntry->SetPersist(
+            nsDocShell::ShouldAddToSessionHistory(uri, aNewChannel));
+      } else {
+        loadingEntry->SetIsSubFrame(aInfo->mInfo.IsSubFrame());
+      }
+      loadingEntry->SetDocshellID(GetHistoryID());
+      loadingEntry->SetIsDynamicallyAdded(CreatedDynamically());
+      return MakeUnique<LoadingSessionHistoryInfo>(loadingEntry, aInfo);
+    }
+  }
+  return nullptr;
+}
+
+using PrintPromise = CanonicalBrowsingContext::PrintPromise;
+#ifdef NS_PRINTING
+class PrintListenerAdapter final : public nsIWebProgressListener {
+ public:
+  explicit PrintListenerAdapter(PrintPromise::Private* aPromise)
+      : mPromise(aPromise) {}
+
+  NS_DECL_ISUPPORTS
+
+  // NS_DECL_NSIWEBPROGRESSLISTENER
+  NS_IMETHOD OnStateChange(nsIWebProgress* aWebProgress, nsIRequest* aRequest,
+                           uint32_t aStateFlags, nsresult aStatus) override {
+    if (aStateFlags & nsIWebProgressListener::STATE_STOP &&
+        aStateFlags & nsIWebProgressListener::STATE_IS_DOCUMENT && mPromise) {
+      mPromise->Resolve(true, __func__);
+      mPromise = nullptr;
+    }
+    return NS_OK;
+  }
+  NS_IMETHOD OnStatusChange(nsIWebProgress* aWebProgress, nsIRequest* aRequest,
+                            nsresult aStatus,
+                            const char16_t* aMessage) override {
+    if (aStatus != NS_OK && mPromise) {
+      mPromise->Reject(aStatus, __func__);
+      mPromise = nullptr;
+    }
+    return NS_OK;
+  }
+  NS_IMETHOD OnProgressChange(nsIWebProgress* aWebProgress,
+                              nsIRequest* aRequest, int32_t aCurSelfProgress,
+                              int32_t aMaxSelfProgress,
+                              int32_t aCurTotalProgress,
+                              int32_t aMaxTotalProgress) override {
+    return NS_OK;
+  }
+  NS_IMETHOD OnLocationChange(nsIWebProgress* aWebProgress,
+                              nsIRequest* aRequest, nsIURI* aLocation,
+                              uint32_t aFlags) override {
+    return NS_OK;
+  }
+  NS_IMETHOD OnSecurityChange(nsIWebProgress* aWebProgress,
+                              nsIRequest* aRequest, uint32_t aState) override {
+    return NS_OK;
+  }
+  NS_IMETHOD OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                    nsIRequest* aRequest,
+                                    uint32_t aEvent) override {
+    return NS_OK;
+  }
+
+ private:
+  ~PrintListenerAdapter() = default;
+
+  RefPtr<PrintPromise::Private> mPromise;
+};
+
+NS_IMPL_ISUPPORTS(PrintListenerAdapter, nsIWebProgressListener)
+#endif
+
+already_AddRefed<Promise> CanonicalBrowsingContext::PrintJS(
+    nsIPrintSettings* aPrintSettings, ErrorResult& aRv) {
+  RefPtr<Promise> promise = Promise::Create(GetIncumbentGlobal(), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return promise.forget();
+  }
+
+  Print(aPrintSettings)
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [promise](bool) { promise->MaybeResolveWithUndefined(); },
+          [promise](nsresult aResult) { promise->MaybeReject(aResult); });
+  return promise.forget();
+}
+
+RefPtr<PrintPromise> CanonicalBrowsingContext::Print(
+    nsIPrintSettings* aPrintSettings) {
+#ifndef NS_PRINTING
+  return PrintPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+#else
+
+  auto promise = MakeRefPtr<PrintPromise::Private>(__func__);
+  auto listener = MakeRefPtr<PrintListenerAdapter>(promise);
+  if (IsInProcess()) {
+    RefPtr<nsGlobalWindowOuter> outerWindow =
+        nsGlobalWindowOuter::Cast(GetDOMWindow());
+    if (NS_WARN_IF(!outerWindow)) {
+      promise->Reject(NS_ERROR_FAILURE, __func__);
+      return promise;
+    }
+
+    ErrorResult rv;
+    outerWindow->Print(aPrintSettings,
+                       /* aRemotePrintJob = */ nullptr, listener,
+                       /* aDocShellToCloneInto = */ nullptr,
+                       nsGlobalWindowOuter::IsPreview::No,
+                       nsGlobalWindowOuter::IsForWindowDotPrint::No,
+                       /* aPrintPreviewCallback = */ nullptr, rv);
+    if (rv.Failed()) {
+      promise->Reject(rv.StealNSResult(), __func__);
+    }
+    return promise;
+  }
+
+  auto* browserParent = GetBrowserParent();
+  if (NS_WARN_IF(!browserParent)) {
+    promise->Reject(NS_ERROR_FAILURE, __func__);
+    return promise;
+  }
+
+  nsCOMPtr<nsIPrintSettingsService> printSettingsSvc =
+      do_GetService("@mozilla.org/gfx/printsettings-service;1");
+  if (NS_WARN_IF(!printSettingsSvc)) {
+    promise->Reject(NS_ERROR_FAILURE, __func__);
+    return promise;
+  }
+
+  nsresult rv;
+  nsCOMPtr<nsIPrintSettings> printSettings = aPrintSettings;
+  if (!printSettings) {
+    rv =
+        printSettingsSvc->CreateNewPrintSettings(getter_AddRefs(printSettings));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      promise->Reject(rv, __func__);
+      return promise;
+    }
+  }
+
+  embedding::PrintData printData;
+  rv = printSettingsSvc->SerializeToPrintData(printSettings, &printData);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    promise->Reject(rv, __func__);
+    return promise;
+  }
+
+  layout::RemotePrintJobParent* remotePrintJob =
+      new layout::RemotePrintJobParent(printSettings);
+  printData.remotePrintJob() =
+      browserParent->Manager()->SendPRemotePrintJobConstructor(remotePrintJob);
+
+  if (listener) {
+    remotePrintJob->RegisterListener(listener);
+  }
+
+  if (NS_WARN_IF(!browserParent->SendPrint(this, printData))) {
+    promise->Reject(NS_ERROR_FAILURE, __func__);
+  }
+  return promise.forget();
+#endif
+}
+
+void CanonicalBrowsingContext::CallOnAllTopDescendants(
+    const FunctionRef<CallState(CanonicalBrowsingContext*)>& aCallback,
+    bool aIncludeNestedBrowsers) {
+  MOZ_ASSERT(IsTop(), "Should only call on top BC");
+  MOZ_ASSERT(
+      !aIncludeNestedBrowsers ||
+          (IsChrome() && !GetParentCrossChromeBoundary()),
+      "If aIncludeNestedBrowsers is set, should only call on top chrome BC");
+
+  if (!IsInProcess()) {
+    // We rely on top levels having to be embedded in the parent process, so
+    // we can only have top level descendants if embedded here..
+    return;
+  }
+
+  AutoTArray<RefPtr<BrowsingContextGroup>, 32> groups;
+  BrowsingContextGroup::GetAllGroups(groups);
+  for (auto& browsingContextGroup : groups) {
+    for (auto& bc : browsingContextGroup->Toplevels()) {
+      if (bc == this) {
+        // Cannot be a descendent of myself so skip.
+        continue;
+      }
+
+      if (aIncludeNestedBrowsers) {
+        if (this != bc->Canonical()->TopCrossChromeBoundary()) {
+          continue;
+        }
+      } else {
+        auto* parent = bc->Canonical()->GetParentCrossChromeBoundary();
+        if (!parent || this != parent->Top()) {
+          continue;
+        }
+      }
+
+      if (aCallback(bc->Canonical()) == CallState::Stop) {
+        return;
+      }
+    }
+  }
+}
+
+void CanonicalBrowsingContext::SessionHistoryCommit(
+    uint64_t aLoadId, const nsID& aChangeID, uint32_t aLoadType, bool aPersist,
+    bool aCloneEntryChildren, bool aChannelExpired, uint32_t aCacheKey) {
+  MOZ_LOG(gSHLog, LogLevel::Verbose,
+          ("CanonicalBrowsingContext::SessionHistoryCommit %p %" PRIu64, this,
+           aLoadId));
+  MOZ_ASSERT(aLoadId != UINT64_MAX,
+             "Must not send special about:blank loadinfo to parent.");
+  for (size_t i = 0; i < mLoadingEntries.Length(); ++i) {
+    if (mLoadingEntries[i].mLoadId == aLoadId) {
+      nsSHistory* shistory = static_cast<nsSHistory*>(GetSessionHistory());
+      if (!shistory) {
+        SessionHistoryEntry::RemoveLoadId(aLoadId);
+        mLoadingEntries.RemoveElementAt(i);
+        return;
+      }
+
+      RefPtr<SessionHistoryEntry> newActiveEntry = mLoadingEntries[i].mEntry;
+      if (aCacheKey != 0) {
+        newActiveEntry->SetCacheKey(aCacheKey);
+      }
+
+      if (aChannelExpired) {
+        newActiveEntry->SharedInfo()->mExpired = true;
+      }
+
+      bool loadFromSessionHistory = !newActiveEntry->ForInitialLoad();
+      newActiveEntry->SetForInitialLoad(false);
+      SessionHistoryEntry::RemoveLoadId(aLoadId);
+      mLoadingEntries.RemoveElementAt(i);
+
+      int32_t indexOfHistoryLoad = -1;
+      if (loadFromSessionHistory) {
+        nsCOMPtr<nsISHEntry> root = nsSHistory::GetRootSHEntry(newActiveEntry);
+        indexOfHistoryLoad = shistory->GetIndexOfEntry(root);
+        if (indexOfHistoryLoad < 0) {
+          // Entry has been removed from the session history.
+          return;
+        }
+      }
+
+      CallerWillNotifyHistoryIndexAndLengthChanges caller(shistory);
+
+      // If there is a name in the new entry, clear the name of all contiguous
+      // entries. This is for https://html.spec.whatwg.org/#history-traversal
+      // Step 4.4.2.
+      nsAutoString nameOfNewEntry;
+      newActiveEntry->GetName(nameOfNewEntry);
+      if (!nameOfNewEntry.IsEmpty()) {
+        nsSHistory::WalkContiguousEntries(
+            newActiveEntry,
+            [](nsISHEntry* aEntry) { aEntry->SetName(EmptyString()); });
+      }
+
+      bool addEntry = ShouldUpdateSessionHistory(aLoadType);
+      if (IsTop()) {
+        if (mActiveEntry && !mActiveEntry->GetFrameLoader()) {
+          bool sharesDocument = true;
+          mActiveEntry->SharesDocumentWith(newActiveEntry, &sharesDocument);
+          if (!sharesDocument) {
+            // If the old page won't be in the bfcache,
+            // clear the dynamic entries.
+            RemoveDynEntriesFromActiveSessionHistoryEntry();
+          }
+        }
+
+        if (LOAD_TYPE_HAS_FLAGS(aLoadType,
+                                nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY)) {
+          // Replace the current entry with the new entry.
+          int32_t index = shistory->GetIndexForReplace();
+
+          // If we're trying to replace an inexistant shistory entry then we
+          // should append instead.
+          addEntry = index < 0;
+          if (!addEntry) {
+            shistory->ReplaceEntry(index, newActiveEntry);
+          }
+          mActiveEntry = newActiveEntry;
+        } else if (LOAD_TYPE_HAS_FLAGS(
+                       aLoadType, nsIWebNavigation::LOAD_FLAGS_IS_REFRESH) &&
+                   !ShouldAddEntryForRefresh(newActiveEntry) && mActiveEntry) {
+          addEntry = false;
+          mActiveEntry->ReplaceWith(*newActiveEntry);
+        } else {
+          mActiveEntry = newActiveEntry;
+        }
+
+        if (loadFromSessionHistory) {
+          // XXX Synchronize browsing context tree and session history tree?
+          shistory->InternalSetRequestedIndex(indexOfHistoryLoad);
+          shistory->UpdateIndex();
+
+          if (IsTop()) {
+            mActiveEntry->SetWireframe(Nothing());
+          }
+        } else if (addEntry) {
+          shistory->AddEntry(mActiveEntry, aPersist);
+          shistory->InternalSetRequestedIndex(-1);
+        }
+      } else {
+        // FIXME The old implementations adds it to the parent's mLSHE if there
+        //       is one, need to figure out if that makes sense here (peterv
+        //       doesn't think it would).
+        if (loadFromSessionHistory) {
+          if (mActiveEntry) {
+            // mActiveEntry is null if we're loading iframes from session
+            // history while also parent page is loading from session history.
+            // In that case there isn't anything to sync.
+            mActiveEntry->SyncTreesForSubframeNavigation(newActiveEntry, Top(),
+                                                         this);
+          }
+          mActiveEntry = newActiveEntry;
+
+          shistory->InternalSetRequestedIndex(indexOfHistoryLoad);
+          // FIXME UpdateIndex() here may update index too early (but even the
+          //       old implementation seems to have similar issues).
+          shistory->UpdateIndex();
+        } else if (addEntry) {
+          if (mActiveEntry) {
+            if (LOAD_TYPE_HAS_FLAGS(
+                    aLoadType, nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY) ||
+                (LOAD_TYPE_HAS_FLAGS(aLoadType,
+                                     nsIWebNavigation::LOAD_FLAGS_IS_REFRESH) &&
+                 !ShouldAddEntryForRefresh(newActiveEntry))) {
+              // FIXME We need to make sure that when we create the info we
+              //       make a copy of the shared state.
+              mActiveEntry->ReplaceWith(*newActiveEntry);
+            } else {
+              // AddChildSHEntryHelper does update the index of the session
+              // history!
+              shistory->AddChildSHEntryHelper(mActiveEntry, newActiveEntry,
+                                              Top(), aCloneEntryChildren);
+              mActiveEntry = newActiveEntry;
+            }
+          } else {
+            SessionHistoryEntry* parentEntry = GetParent()->mActiveEntry;
+            // XXX What should happen if parent doesn't have mActiveEntry?
+            //     Or can that even happen ever?
+            if (parentEntry) {
+              mActiveEntry = newActiveEntry;
+              // FIXME Using IsInProcess for aUseRemoteSubframes isn't quite
+              //       right, but aUseRemoteSubframes should be going away.
+              parentEntry->AddChild(
+                  mActiveEntry,
+                  CreatedDynamically() ? -1 : GetParent()->IndexOf(this),
+                  IsInProcess());
+            }
+          }
+          shistory->InternalSetRequestedIndex(-1);
+        }
+      }
+
+      ResetSHEntryHasUserInteractionCache();
+
+      HistoryCommitIndexAndLength(aChangeID, caller);
+
+      shistory->LogHistory();
+
+      return;
+    }
+    // XXX Should the loading entries before [i] be removed?
+  }
+  // FIXME Should we throw an error if we don't find an entry for
+  // aSessionHistoryEntryId?
+}
+
+already_AddRefed<nsDocShellLoadState> CanonicalBrowsingContext::CreateLoadInfo(
+    SessionHistoryEntry* aEntry) {
+  const SessionHistoryInfo& info = aEntry->Info();
+  RefPtr<nsDocShellLoadState> loadState(new nsDocShellLoadState(info.GetURI()));
+  info.FillLoadInfo(*loadState);
+  UniquePtr<LoadingSessionHistoryInfo> loadingInfo;
+  loadingInfo = MakeUnique<LoadingSessionHistoryInfo>(aEntry);
+  mLoadingEntries.AppendElement(
+      LoadingSessionHistoryEntry{loadingInfo->mLoadId, aEntry});
+  loadState->SetLoadingSessionHistoryInfo(std::move(loadingInfo));
+
+  return loadState.forget();
+}
+
+void CanonicalBrowsingContext::NotifyOnHistoryReload(
+    bool aForceReload, bool& aCanReload,
+    Maybe<NotNull<RefPtr<nsDocShellLoadState>>>& aLoadState,
+    Maybe<bool>& aReloadActiveEntry) {
+  MOZ_DIAGNOSTIC_ASSERT(!aLoadState);
+
+  aCanReload = true;
+  nsISHistory* shistory = GetSessionHistory();
+  NS_ENSURE_TRUE_VOID(shistory);
+
+  shistory->NotifyOnHistoryReload(&aCanReload);
+  if (!aCanReload) {
+    return;
+  }
+
+  if (mActiveEntry) {
+    aLoadState.emplace(WrapMovingNotNull(RefPtr{CreateLoadInfo(mActiveEntry)}));
+    aReloadActiveEntry.emplace(true);
+    if (aForceReload) {
+      shistory->RemoveFrameEntries(mActiveEntry);
+    }
+  } else if (!mLoadingEntries.IsEmpty()) {
+    const LoadingSessionHistoryEntry& loadingEntry =
+        mLoadingEntries.LastElement();
+    uint64_t loadId = loadingEntry.mLoadId;
+    aLoadState.emplace(
+        WrapMovingNotNull(RefPtr{CreateLoadInfo(loadingEntry.mEntry)}));
+    aReloadActiveEntry.emplace(false);
+    if (aForceReload) {
+      SessionHistoryEntry::LoadingEntry* entry =
+          SessionHistoryEntry::GetByLoadId(loadId);
+      if (entry) {
+        shistory->RemoveFrameEntries(entry->mEntry);
+      }
+    }
+  }
+
+  if (aLoadState) {
+    // Use 0 as the offset, since aLoadState will be be used for reload.
+    aLoadState.ref()->SetLoadIsFromSessionHistory(0,
+                                                  aReloadActiveEntry.value());
+  }
+  // If we don't have an active entry and we don't have a loading entry then
+  // the nsDocShell will create a load state based on its document.
+}
+
+void CanonicalBrowsingContext::SetActiveSessionHistoryEntry(
+    const Maybe<nsPoint>& aPreviousScrollPos, SessionHistoryInfo* aInfo,
+    uint32_t aLoadType, uint32_t aUpdatedCacheKey, const nsID& aChangeID) {
+  nsISHistory* shistory = GetSessionHistory();
+  if (!shistory) {
+    return;
+  }
+  CallerWillNotifyHistoryIndexAndLengthChanges caller(shistory);
+
+  RefPtr<SessionHistoryEntry> oldActiveEntry = mActiveEntry;
+  if (aPreviousScrollPos.isSome() && oldActiveEntry) {
+    oldActiveEntry->SetScrollPosition(aPreviousScrollPos.ref().x,
+                                      aPreviousScrollPos.ref().y);
+  }
+  mActiveEntry = new SessionHistoryEntry(aInfo);
+  mActiveEntry->SetDocshellID(GetHistoryID());
+  mActiveEntry->AdoptBFCacheEntry(oldActiveEntry);
+  if (aUpdatedCacheKey != 0) {
+    mActiveEntry->SharedInfo()->mCacheKey = aUpdatedCacheKey;
+  }
+
+  if (IsTop()) {
+    Maybe<int32_t> previousEntryIndex, loadedEntryIndex;
+    shistory->AddToRootSessionHistory(
+        true, oldActiveEntry, this, mActiveEntry, aLoadType,
+        nsDocShell::ShouldAddToSessionHistory(aInfo->GetURI(), nullptr),
+        &previousEntryIndex, &loadedEntryIndex);
+  } else {
+    if (oldActiveEntry) {
+      shistory->AddChildSHEntryHelper(oldActiveEntry, mActiveEntry, Top(),
+                                      true);
+    } else if (GetParent() && GetParent()->mActiveEntry) {
+      GetParent()->mActiveEntry->AddChild(
+          mActiveEntry, CreatedDynamically() ? -1 : GetParent()->IndexOf(this),
+          UseRemoteSubframes());
+    }
+  }
+
+  ResetSHEntryHasUserInteractionCache();
+
+  shistory->InternalSetRequestedIndex(-1);
+
+  // FIXME Need to do the equivalent of EvictDocumentViewersOrReplaceEntry.
+  HistoryCommitIndexAndLength(aChangeID, caller);
+
+  static_cast<nsSHistory*>(shistory)->LogHistory();
+}
+
+void CanonicalBrowsingContext::ReplaceActiveSessionHistoryEntry(
+    SessionHistoryInfo* aInfo) {
+  if (!mActiveEntry) {
+    return;
+  }
+
+  mActiveEntry->SetInfo(aInfo);
+  // Notify children of the update
+  nsSHistory* shistory = static_cast<nsSHistory*>(GetSessionHistory());
+  if (shistory) {
+    shistory->NotifyOnHistoryReplaceEntry();
+    shistory->UpdateRootBrowsingContextState();
+  }
+
+  ResetSHEntryHasUserInteractionCache();
+
+  if (IsTop()) {
+    mActiveEntry->SetWireframe(Nothing());
+  }
+
+  // FIXME Need to do the equivalent of EvictDocumentViewersOrReplaceEntry.
+}
+
+void CanonicalBrowsingContext::RemoveDynEntriesFromActiveSessionHistoryEntry() {
+  nsISHistory* shistory = GetSessionHistory();
+  // In theory shistory can be null here if the method is called right after
+  // CanonicalBrowsingContext::ReplacedBy call.
+  NS_ENSURE_TRUE_VOID(shistory);
+  nsCOMPtr<nsISHEntry> root = nsSHistory::GetRootSHEntry(mActiveEntry);
+  shistory->RemoveDynEntries(shistory->GetIndexOfEntry(root), mActiveEntry);
+}
+
+void CanonicalBrowsingContext::RemoveFromSessionHistory(const nsID& aChangeID) {
+  nsSHistory* shistory = static_cast<nsSHistory*>(GetSessionHistory());
+  if (shistory) {
+    CallerWillNotifyHistoryIndexAndLengthChanges caller(shistory);
+    nsCOMPtr<nsISHEntry> root = nsSHistory::GetRootSHEntry(mActiveEntry);
+    bool didRemove;
+    AutoTArray<nsID, 16> ids({GetHistoryID()});
+    shistory->RemoveEntries(ids, shistory->GetIndexOfEntry(root), &didRemove);
+    if (didRemove) {
+      RefPtr<BrowsingContext> rootBC = shistory->GetBrowsingContext();
+      if (rootBC) {
+        if (!rootBC->IsInProcess()) {
+          if (ContentParent* cp = rootBC->Canonical()->GetContentParent()) {
+            Unused << cp->SendDispatchLocationChangeEvent(rootBC);
+          }
+        } else if (rootBC->GetDocShell()) {
+          rootBC->GetDocShell()->DispatchLocationChangeEvent();
+        }
+      }
+    }
+    HistoryCommitIndexAndLength(aChangeID, caller);
+  }
+}
+
+Maybe<int32_t> CanonicalBrowsingContext::HistoryGo(
+    int32_t aOffset, uint64_t aHistoryEpoch, bool aRequireUserInteraction,
+    bool aUserActivation, Maybe<ContentParentId> aContentId) {
+  if (aRequireUserInteraction && aOffset != -1 && aOffset != 1) {
+    NS_ERROR(
+        "aRequireUserInteraction may only be used with an offset of -1 or 1");
+    return Nothing();
+  }
+
+  nsSHistory* shistory = static_cast<nsSHistory*>(GetSessionHistory());
+  if (!shistory) {
+    return Nothing();
+  }
+
+  CheckedInt<int32_t> index = shistory->GetRequestedIndex() >= 0
+                                  ? shistory->GetRequestedIndex()
+                                  : shistory->Index();
+  MOZ_LOG(gSHLog, LogLevel::Debug,
+          ("HistoryGo(%d->%d) epoch %" PRIu64 "/id %" PRIu64, aOffset,
+           (index + aOffset).value(), aHistoryEpoch,
+           (uint64_t)(aContentId.isSome() ? aContentId.value() : 0)));
+
+  while (true) {
+    index += aOffset;
+    if (!index.isValid()) {
+      MOZ_LOG(gSHLog, LogLevel::Debug, ("Invalid index"));
+      return Nothing();
+    }
+
+    // Check for user interaction if desired, except for the first and last
+    // history entries. We compare with >= to account for the case where
+    // aOffset >= length.
+    if (!aRequireUserInteraction || index.value() >= shistory->Length() - 1 ||
+        index.value() <= 0) {
+      break;
+    }
+    if (shistory->HasUserInteractionAtIndex(index.value())) {
+      break;
+    }
+  }
+
+  // Implement aborting additional history navigations from within the same
+  // event spin of the content process.
+
+  uint64_t epoch;
+  bool sameEpoch = false;
+  Maybe<ContentParentId> id;
+  shistory->GetEpoch(epoch, id);
+
+  if (aContentId == id && epoch >= aHistoryEpoch) {
+    sameEpoch = true;
+    MOZ_LOG(gSHLog, LogLevel::Debug, ("Same epoch/id"));
+  }
+  // Don't update the epoch until we know if the target index is valid
+
+  // GoToIndex checks that index is >= 0 and < length.
+  nsTArray<nsSHistory::LoadEntryResult> loadResults;
+  nsresult rv = shistory->GotoIndex(index.value(), loadResults, sameEpoch,
+                                    aOffset == 0, aUserActivation);
+  if (NS_FAILED(rv)) {
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("Dropping HistoryGo - bad index or same epoch (not in same doc)"));
+    return Nothing();
+  }
+  if (epoch < aHistoryEpoch || aContentId != id) {
+    MOZ_LOG(gSHLog, LogLevel::Debug, ("Set epoch"));
+    shistory->SetEpoch(aHistoryEpoch, aContentId);
+  }
+  int32_t requestedIndex = shistory->GetRequestedIndex();
+  nsSHistory::LoadURIs(loadResults);
+  return Some(requestedIndex);
+}
+
+JSObject* CanonicalBrowsingContext::WrapObject(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return CanonicalBrowsingContext_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void CanonicalBrowsingContext::DispatchWheelZoomChange(bool aIncrease) {
+  Element* element = Top()->GetEmbedderElement();
+  if (!element) {
+    return;
+  }
+
+  auto event = aIncrease ? u"DoZoomEnlargeBy10"_ns : u"DoZoomReduceBy10"_ns;
+  auto dispatcher = MakeRefPtr<AsyncEventDispatcher>(
+      element, event, CanBubble::eYes, ChromeOnlyDispatch::eYes);
+  dispatcher->PostDOMEvent();
+}
+
+void CanonicalBrowsingContext::CanonicalDiscard() {
+  if (mTabMediaController) {
+    mTabMediaController->Shutdown();
+    mTabMediaController = nullptr;
+  }
+
+  if (mCurrentLoad) {
+    mCurrentLoad->Cancel(NS_BINDING_ABORTED,
+                         "CanonicalBrowsingContext::CanonicalDiscard"_ns);
+  }
+
+  if (mWebProgress) {
+    RefPtr<BrowsingContextWebProgress> progress = mWebProgress;
+    progress->ContextDiscarded();
+  }
+
+  if (IsTop()) {
+    BackgroundSessionStorageManager::RemoveManager(Id());
+  }
+
+  CancelSessionStoreUpdate();
+
+  if (UsePrivateBrowsing() && EverAttached() && IsContent()) {
+    DecreasePrivateCount();
+  }
+}
+
+void CanonicalBrowsingContext::CanonicalAttach() {
+  if (UsePrivateBrowsing() && IsContent()) {
+    IncreasePrivateCount();
+  }
+}
+
+void CanonicalBrowsingContext::AddPendingDiscard() {
+  MOZ_ASSERT(!mFullyDiscarded);
+  mPendingDiscards++;
+}
+
+void CanonicalBrowsingContext::RemovePendingDiscard() {
+  mPendingDiscards--;
+  if (!mPendingDiscards) {
+    mFullyDiscarded = true;
+    auto listeners = std::move(mFullyDiscardedListeners);
+    for (const auto& listener : listeners) {
+      listener(Id());
+    }
+  }
+}
+
+void CanonicalBrowsingContext::AddFinalDiscardListener(
+    std::function<void(uint64_t)>&& aListener) {
+  if (mFullyDiscarded) {
+    aListener(Id());
+    return;
+  }
+  mFullyDiscardedListeners.AppendElement(std::move(aListener));
+}
+
+void CanonicalBrowsingContext::SetForceAppWindowActive(bool aForceActive,
+                                                       ErrorResult& aRv) {
+  MOZ_DIAGNOSTIC_ASSERT(IsChrome());
+  MOZ_DIAGNOSTIC_ASSERT(IsTop());
+  if (!IsChrome() || !IsTop()) {
+    return aRv.ThrowNotAllowedError(
+        "You shouldn't need to force this BrowsingContext to be active, use "
+        ".isActive instead");
+  }
+  if (mForceAppWindowActive == aForceActive) {
+    return;
+  }
+  mForceAppWindowActive = aForceActive;
+  RecomputeAppWindowVisibility();
+}
+
+void CanonicalBrowsingContext::RecomputeAppWindowVisibility() {
+  MOZ_RELEASE_ASSERT(IsChrome());
+  MOZ_RELEASE_ASSERT(IsTop());
+
+  const bool wasAlreadyActive = IsActive();
+
+  nsCOMPtr<nsIWidget> widget;
+  if (auto* docShell = GetDocShell()) {
+    nsDocShell::Cast(docShell)->GetMainWidget(getter_AddRefs(widget));
+  }
+
+  Unused << NS_WARN_IF(!widget);
+  const bool isNowActive =
+      ForceAppWindowActive() || (widget && !widget->IsFullyOccluded() &&
+                                 widget->SizeMode() != nsSizeMode_Minimized);
+
+  if (isNowActive == wasAlreadyActive) {
+    return;
+  }
+
+  SetIsActiveInternal(isNowActive, IgnoreErrors());
+  if (widget) {
+    // Pause if we are not active, resume if we are active.
+    widget->PauseOrResumeCompositor(!isNowActive);
+  }
+}
+
+void CanonicalBrowsingContext::AdjustPrivateBrowsingCount(
+    bool aPrivateBrowsing) {
+  if (IsDiscarded() || !EverAttached() || IsChrome()) {
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(aPrivateBrowsing == UsePrivateBrowsing());
+  if (aPrivateBrowsing) {
+    IncreasePrivateCount();
+  } else {
+    DecreasePrivateCount();
+  }
+}
+
+void CanonicalBrowsingContext::NotifyStartDelayedAutoplayMedia() {
+  WindowContext* windowContext = GetCurrentWindowContext();
+  if (!windowContext) {
+    return;
+  }
+
+  // As this function would only be called when user click the play icon on the
+  // tab bar. That's clear user intent to play, so gesture activate the window
+  // context so that the block-autoplay logic allows the media to autoplay.
+  windowContext->NotifyUserGestureActivation();
+  AUTOPLAY_LOG("NotifyStartDelayedAutoplayMedia for chrome bc 0x%08" PRIx64,
+               Id());
+  StartDelayedAutoplayMediaComponents();
+  // Notfiy all content browsing contexts which are related with the canonical
+  // browsing content tree to start delayed autoplay media.
+
+  Group()->EachParent([&](ContentParent* aParent) {
+    Unused << aParent->SendStartDelayedAutoplayMediaComponents(this);
+  });
+}
+
+void CanonicalBrowsingContext::NotifyMediaMutedChanged(bool aMuted,
+                                                       ErrorResult& aRv) {
+  MOZ_ASSERT(!GetParent(),
+             "Notify media mute change on non top-level context!");
+  SetMuted(aMuted, aRv);
+}
+
+uint32_t CanonicalBrowsingContext::CountSiteOrigins(
+    GlobalObject& aGlobal,
+    const Sequence<OwningNonNull<BrowsingContext>>& aRoots) {
+  nsTHashSet<nsCString> uniqueSiteOrigins;
+
+  for (const auto& root : aRoots) {
+    root->PreOrderWalk([&](BrowsingContext* aContext) {
+      WindowGlobalParent* windowGlobalParent =
+          aContext->Canonical()->GetCurrentWindowGlobal();
+      if (windowGlobalParent) {
+        nsIPrincipal* documentPrincipal =
+            windowGlobalParent->DocumentPrincipal();
+
+        bool isContentPrincipal = documentPrincipal->GetIsContentPrincipal();
+        if (isContentPrincipal) {
+          nsCString siteOrigin;
+          documentPrincipal->GetSiteOrigin(siteOrigin);
+          uniqueSiteOrigins.Insert(siteOrigin);
+        }
+      }
+    });
+  }
+
+  return uniqueSiteOrigins.Count();
+}
+
+/* static */
+bool CanonicalBrowsingContext::IsPrivateBrowsingActive() {
+  return gNumberOfPrivateContexts > 0;
+}
+
+void CanonicalBrowsingContext::UpdateMediaControlAction(
+    const MediaControlAction& aAction) {
+  if (IsDiscarded()) {
+    return;
+  }
+  ContentMediaControlKeyHandler::HandleMediaControlAction(this, aAction);
+  Group()->EachParent([&](ContentParent* aParent) {
+    Unused << aParent->SendUpdateMediaControlAction(this, aAction);
+  });
+}
+
+void CanonicalBrowsingContext::LoadURI(nsIURI* aURI,
+                                       const LoadURIOptions& aOptions,
+                                       ErrorResult& aError) {
+  RefPtr<nsDocShellLoadState> loadState;
+  nsresult rv = nsDocShellLoadState::CreateFromLoadURIOptions(
+      this, aURI, aOptions, getter_AddRefs(loadState));
+  MOZ_ASSERT(rv != NS_ERROR_MALFORMED_URI);
+
+  if (NS_FAILED(rv)) {
+    aError.Throw(rv);
+    return;
+  }
+
+  LoadURI(loadState, true);
+}
+
+void CanonicalBrowsingContext::FixupAndLoadURIString(
+    const nsAString& aURI, const LoadURIOptions& aOptions,
+    ErrorResult& aError) {
+  RefPtr<nsDocShellLoadState> loadState;
+  nsresult rv = nsDocShellLoadState::CreateFromLoadURIOptions(
+      this, aURI, aOptions, getter_AddRefs(loadState));
+
+  if (rv == NS_ERROR_MALFORMED_URI) {
+    DisplayLoadError(aURI);
+    return;
+  }
+
+  if (NS_FAILED(rv)) {
+    aError.Throw(rv);
+    return;
+  }
+
+  LoadURI(loadState, true);
+}
+
+void CanonicalBrowsingContext::GoBack(
+    const Optional<int32_t>& aCancelContentJSEpoch,
+    bool aRequireUserInteraction, bool aUserActivation) {
+  if (IsDiscarded()) {
+    return;
+  }
+
+  // Stop any known network loads if necessary.
+  if (mCurrentLoad) {
+    mCurrentLoad->Cancel(NS_BINDING_CANCELLED_OLD_LOAD, ""_ns);
+  }
+
+  if (RefPtr<nsDocShell> docShell = nsDocShell::Cast(GetDocShell())) {
+    if (aCancelContentJSEpoch.WasPassed()) {
+      docShell->SetCancelContentJSEpoch(aCancelContentJSEpoch.Value());
+    }
+    docShell->GoBack(aRequireUserInteraction, aUserActivation);
+  } else if (ContentParent* cp = GetContentParent()) {
+    Maybe<int32_t> cancelContentJSEpoch;
+    if (aCancelContentJSEpoch.WasPassed()) {
+      cancelContentJSEpoch = Some(aCancelContentJSEpoch.Value());
+    }
+    Unused << cp->SendGoBack(this, cancelContentJSEpoch,
+                             aRequireUserInteraction, aUserActivation);
+  }
+}
+void CanonicalBrowsingContext::GoForward(
+    const Optional<int32_t>& aCancelContentJSEpoch,
+    bool aRequireUserInteraction, bool aUserActivation) {
+  if (IsDiscarded()) {
+    return;
+  }
+
+  // Stop any known network loads if necessary.
+  if (mCurrentLoad) {
+    mCurrentLoad->Cancel(NS_BINDING_CANCELLED_OLD_LOAD, ""_ns);
+  }
+
+  if (RefPtr<nsDocShell> docShell = nsDocShell::Cast(GetDocShell())) {
+    if (aCancelContentJSEpoch.WasPassed()) {
+      docShell->SetCancelContentJSEpoch(aCancelContentJSEpoch.Value());
+    }
+    docShell->GoForward(aRequireUserInteraction, aUserActivation);
+  } else if (ContentParent* cp = GetContentParent()) {
+    Maybe<int32_t> cancelContentJSEpoch;
+    if (aCancelContentJSEpoch.WasPassed()) {
+      cancelContentJSEpoch.emplace(aCancelContentJSEpoch.Value());
+    }
+    Unused << cp->SendGoForward(this, cancelContentJSEpoch,
+                                aRequireUserInteraction, aUserActivation);
+  }
+}
+void CanonicalBrowsingContext::GoToIndex(
+    int32_t aIndex, const Optional<int32_t>& aCancelContentJSEpoch,
+    bool aUserActivation) {
+  if (IsDiscarded()) {
+    return;
+  }
+
+  // Stop any known network loads if necessary.
+  if (mCurrentLoad) {
+    mCurrentLoad->Cancel(NS_BINDING_CANCELLED_OLD_LOAD, ""_ns);
+  }
+
+  if (RefPtr<nsDocShell> docShell = nsDocShell::Cast(GetDocShell())) {
+    if (aCancelContentJSEpoch.WasPassed()) {
+      docShell->SetCancelContentJSEpoch(aCancelContentJSEpoch.Value());
+    }
+    docShell->GotoIndex(aIndex, aUserActivation);
+  } else if (ContentParent* cp = GetContentParent()) {
+    Maybe<int32_t> cancelContentJSEpoch;
+    if (aCancelContentJSEpoch.WasPassed()) {
+      cancelContentJSEpoch.emplace(aCancelContentJSEpoch.Value());
+    }
+    Unused << cp->SendGoToIndex(this, aIndex, cancelContentJSEpoch,
+                                aUserActivation);
+  }
+}
+void CanonicalBrowsingContext::Reload(uint32_t aReloadFlags) {
+  if (IsDiscarded()) {
+    return;
+  }
+
+  // Stop any known network loads if necessary.
+  if (mCurrentLoad) {
+    mCurrentLoad->Cancel(NS_BINDING_CANCELLED_OLD_LOAD, ""_ns);
+  }
+
+  if (RefPtr<nsDocShell> docShell = nsDocShell::Cast(GetDocShell())) {
+    docShell->Reload(aReloadFlags);
+  } else if (ContentParent* cp = GetContentParent()) {
+    Unused << cp->SendReload(this, aReloadFlags);
+  }
+}
+
+void CanonicalBrowsingContext::Stop(uint32_t aStopFlags) {
+  if (IsDiscarded()) {
+    return;
+  }
+
+  // Stop any known network loads if necessary.
+  if (mCurrentLoad && (aStopFlags & nsIWebNavigation::STOP_NETWORK)) {
+    mCurrentLoad->Cancel(NS_BINDING_ABORTED,
+                         "CanonicalBrowsingContext::Stop"_ns);
+  }
+
+  // Ask the docshell to stop to handle loads that haven't
+  // yet reached here, as well as non-network activity.
+  if (auto* docShell = nsDocShell::Cast(GetDocShell())) {
+    docShell->Stop(aStopFlags);
+  } else if (ContentParent* cp = GetContentParent()) {
+    Unused << cp->SendStopLoad(this, aStopFlags);
+  }
+}
+
+void CanonicalBrowsingContext::PendingRemotenessChange::ProcessLaunched() {
+  if (!mPromise) {
+    return;
+  }
+
+  if (mContentParent) {
+    // If our new content process is still unloading from a previous process
+    // switch, wait for that unload to complete before continuing.
+    auto found = mTarget->FindUnloadingHost(mContentParent->ChildID());
+    if (found != mTarget->mUnloadingHosts.end()) {
+      found->mCallbacks.AppendElement(
+          [self = RefPtr{this}]() { self->ProcessReady(); });
+      return;
+    }
+  }
+
+  ProcessReady();
+}
+
+void CanonicalBrowsingContext::PendingRemotenessChange::ProcessReady() {
+  if (!mPromise) {
+    return;
+  }
+
+  MOZ_ASSERT(!mProcessReady);
+  mProcessReady = true;
+  MaybeFinish();
+}
+
+void CanonicalBrowsingContext::PendingRemotenessChange::MaybeFinish() {
+  if (!mPromise) {
+    return;
+  }
+
+  if (!mProcessReady || mWaitingForPrepareToChange) {
+    return;
+  }
+
+  // If this BrowsingContext is embedded within the parent process, perform the
+  // process switch directly.
+  nsresult rv = mTarget->IsTopContent() ? FinishTopContent() : FinishSubframe();
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Error finishing PendingRemotenessChange!");
+    Cancel(rv);
+  } else {
+    Clear();
+  }
+}
+
+// Logic for finishing a toplevel process change embedded within the parent
+// process. Due to frontend integration the logic differs substantially from
+// subframe process switches, and is handled separately.
+nsresult CanonicalBrowsingContext::PendingRemotenessChange::FinishTopContent() {
+  MOZ_DIAGNOSTIC_ASSERT(mTarget->IsTop(),
+                        "We shouldn't be trying to change the remoteness of "
+                        "non-remote iframes");
+
+  // Abort if our ContentParent died while process switching.
+  if (mContentParent && NS_WARN_IF(mContentParent->IsShuttingDown())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // While process switching, we need to check if any of our ancestors are
+  // discarded or no longer current, in which case the process switch needs to
+  // be aborted.
+  RefPtr<CanonicalBrowsingContext> target(mTarget);
+  if (target->IsDiscarded() || !target->AncestorsAreCurrent()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  Element* browserElement = target->GetEmbedderElement();
+  if (!browserElement) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIBrowser> browser = browserElement->AsBrowser();
+  if (!browser) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<nsFrameLoaderOwner> frameLoaderOwner = do_QueryObject(browserElement);
+  MOZ_RELEASE_ASSERT(frameLoaderOwner,
+                     "embedder browser must be nsFrameLoaderOwner");
+
+  // If we're process switching a browsing context in private browsing
+  // mode we might decrease the private browsing count to '0', which
+  // would make us fire "last-pb-context-exited" and drop the private
+  // session. To prevent that we artificially increment the number of
+  // private browsing contexts with '1' until the process switch is done.
+  bool usePrivateBrowsing = mTarget->UsePrivateBrowsing();
+  if (usePrivateBrowsing) {
+    IncreasePrivateCount();
+  }
+
+  auto restorePrivateCount = MakeScopeExit([usePrivateBrowsing]() {
+    if (usePrivateBrowsing) {
+      DecreasePrivateCount();
+    }
+  });
+
+  // Tell frontend code that this browser element is about to change process.
+  nsresult rv = browser->BeforeChangeRemoteness();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // Some frontend code checks the value of the `remote` attribute on the
+  // browser to determine if it is remote, so update the value.
+  browserElement->SetAttr(kNameSpaceID_None, nsGkAtoms::remote,
+                          mContentParent ? u"true"_ns : u"false"_ns,
+                          /* notify */ true);
+
+  // The process has been created, hand off to nsFrameLoaderOwner to finish
+  // the process switch.
+  ErrorResult error;
+  frameLoaderOwner->ChangeRemotenessToProcess(mContentParent, mOptions,
+                                              mSpecificGroup, error);
+  if (error.Failed()) {
+    return error.StealNSResult();
+  }
+
+  // Tell frontend the load is done.
+  bool loadResumed = false;
+  rv = browser->FinishChangeRemoteness(mPendingSwitchId, &loadResumed);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // We did it! The process switch is complete.
+  RefPtr<nsFrameLoader> frameLoader = frameLoaderOwner->GetFrameLoader();
+  RefPtr<BrowserParent> newBrowser = frameLoader->GetBrowserParent();
+  if (!newBrowser) {
+    if (mContentParent) {
+      // Failed to create the BrowserParent somehow! Abort the process switch
+      // attempt.
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    if (!loadResumed) {
+      RefPtr<nsDocShell> newDocShell = frameLoader->GetDocShell(error);
+      if (error.Failed()) {
+        return error.StealNSResult();
+      }
+
+      rv = newDocShell->ResumeRedirectedLoad(mPendingSwitchId,
+                                             /* aHistoryIndex */ -1);
+      if (NS_FAILED(rv)) {
+        return rv;
+      }
+    }
+  } else if (!loadResumed) {
+    newBrowser->ResumeLoad(mPendingSwitchId);
+  }
+
+  mPromise->Resolve(newBrowser, __func__);
+  return NS_OK;
+}
+
+nsresult CanonicalBrowsingContext::PendingRemotenessChange::FinishSubframe() {
+  MOZ_DIAGNOSTIC_ASSERT(!mOptions.mReplaceBrowsingContext,
+                        "Cannot replace BC for subframe");
+  MOZ_DIAGNOSTIC_ASSERT(!mTarget->IsTop());
+
+  // While process switching, we need to check if any of our ancestors are
+  // discarded or no longer current, in which case the process switch needs to
+  // be aborted.
+  RefPtr<CanonicalBrowsingContext> target(mTarget);
+  if (target->IsDiscarded() || !target->AncestorsAreCurrent()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (NS_WARN_IF(!mContentParent)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<WindowGlobalParent> embedderWindow = target->GetParentWindowContext();
+  if (NS_WARN_IF(!embedderWindow) || NS_WARN_IF(!embedderWindow->CanSend())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<BrowserParent> embedderBrowser = embedderWindow->GetBrowserParent();
+  if (NS_WARN_IF(!embedderBrowser)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // If we're creating a new remote browser, and the host process is already
+  // dead, abort the process switch.
+  if (mContentParent != embedderBrowser->Manager() &&
+      NS_WARN_IF(mContentParent->IsShuttingDown())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<BrowserParent> oldBrowser = target->GetBrowserParent();
+  target->SetCurrentBrowserParent(nullptr);
+
+  // If we were in a remote frame, trigger unloading of the remote window. The
+  // previous BrowserParent is registered in `mUnloadingHosts` and will only be
+  // cleared when the BrowserParent is fully destroyed.
+  bool wasRemote = oldBrowser && oldBrowser->GetBrowsingContext() == target;
+  if (wasRemote) {
+    MOZ_DIAGNOSTIC_ASSERT(oldBrowser != embedderBrowser);
+    MOZ_DIAGNOSTIC_ASSERT(oldBrowser->IsDestroyed() ||
+                          oldBrowser->GetBrowserBridgeParent());
+
+    // `oldBrowser` will clear the `UnloadingHost` status once the actor has
+    // been destroyed.
+    if (oldBrowser->CanSend()) {
+      target->StartUnloadingHost(oldBrowser->Manager()->ChildID());
+      Unused << oldBrowser->SendWillChangeProcess();
+      oldBrowser->Destroy();
+    }
+  }
+
+  // Update which process is considered the current owner
+  target->SetOwnerProcessId(mContentParent->ChildID());
+
+  // If we're switching from remote to local, we don't need to create a
+  // BrowserBridge, and can instead perform the switch directly.
+  if (mContentParent == embedderBrowser->Manager()) {
+    MOZ_DIAGNOSTIC_ASSERT(
+        mPendingSwitchId,
+        "We always have a PendingSwitchId, except for print-preview loads, "
+        "which will never perform a process-switch to being in-process with "
+        "their embedder");
+    MOZ_DIAGNOSTIC_ASSERT(wasRemote,
+                          "Attempt to process-switch from local to local?");
+
+    target->SetCurrentBrowserParent(embedderBrowser);
+    Unused << embedderWindow->SendMakeFrameLocal(target, mPendingSwitchId);
+    mPromise->Resolve(embedderBrowser, __func__);
+    return NS_OK;
+  }
+
+  // The BrowsingContext will be remote, either as an already-remote frame
+  // changing processes, or as a local frame becoming remote. Construct a new
+  // BrowserBridgeParent to host the remote content.
+  target->SetCurrentBrowserParent(nullptr);
+
+  MOZ_DIAGNOSTIC_ASSERT(target->UseRemoteTabs() && target->UseRemoteSubframes(),
+                        "Not supported without fission");
+  uint32_t chromeFlags = nsIWebBrowserChrome::CHROME_REMOTE_WINDOW |
+                         nsIWebBrowserChrome::CHROME_FISSION_WINDOW;
+  if (target->UsePrivateBrowsing()) {
+    chromeFlags |= nsIWebBrowserChrome::CHROME_PRIVATE_WINDOW;
+  }
+
+  nsCOMPtr<nsIPrincipal> initialPrincipal =
+      NullPrincipal::Create(target->OriginAttributesRef());
+  WindowGlobalInit windowInit =
+      WindowGlobalActor::AboutBlankInitializer(target, initialPrincipal);
+
+  // Create and initialize our new BrowserBridgeParent.
+  TabId tabId(nsContentUtils::GenerateTabId());
+  RefPtr<BrowserBridgeParent> bridge = new BrowserBridgeParent();
+  nsresult rv = bridge->InitWithProcess(embedderBrowser, mContentParent,
+                                        windowInit, chromeFlags, tabId);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    // If we've already destroyed our previous document, make a best-effort
+    // attempt to recover from this failure and show the crashed tab UI. We only
+    // do this in the previously-remote case, as previously in-process frames
+    // will have their navigation cancelled, and will remain visible.
+    if (wasRemote) {
+      target->ShowSubframeCrashedUI(oldBrowser->GetBrowserBridgeParent());
+    }
+    return rv;
+  }
+
+  // Tell the embedder process a remoteness change is in-process. When this is
+  // acknowledged, reset the in-flight ID if it used to be an in-process load.
+  RefPtr<BrowserParent> newBrowser = bridge->GetBrowserParent();
+  {
+    // If we weren't remote, mark our embedder window browser as unloading until
+    // our embedder process has acked our MakeFrameRemote message.
+    Maybe<uint64_t> clearChildID;
+    if (!wasRemote) {
+      clearChildID = Some(embedderBrowser->Manager()->ChildID());
+      target->StartUnloadingHost(*clearChildID);
+    }
+    auto callback = [target, clearChildID](auto&&) {
+      if (clearChildID) {
+        target->ClearUnloadingHost(*clearChildID);
+      }
+    };
+
+    ManagedEndpoint<PBrowserBridgeChild> endpoint =
+        embedderBrowser->OpenPBrowserBridgeEndpoint(bridge);
+    MOZ_DIAGNOSTIC_ASSERT(endpoint.IsValid());
+    embedderWindow->SendMakeFrameRemote(target, std::move(endpoint), tabId,
+                                        newBrowser->GetLayersId(), callback,
+                                        callback);
+  }
+
+  // Resume the pending load in our new process.
+  if (mPendingSwitchId) {
+    newBrowser->ResumeLoad(mPendingSwitchId);
+  }
+
+  // We did it! The process switch is complete.
+  mPromise->Resolve(newBrowser, __func__);
+  return NS_OK;
+}
+
+void CanonicalBrowsingContext::PendingRemotenessChange::Cancel(nsresult aRv) {
+  if (!mPromise) {
+    return;
+  }
+
+  mPromise->Reject(aRv, __func__);
+  Clear();
+}
+
+void CanonicalBrowsingContext::PendingRemotenessChange::Clear() {
+  // Make sure we don't die while we're doing cleanup.
+  RefPtr<PendingRemotenessChange> kungFuDeathGrip(this);
+  if (mTarget) {
+    MOZ_DIAGNOSTIC_ASSERT(mTarget->mPendingRemotenessChange == this);
+    mTarget->mPendingRemotenessChange = nullptr;
+  }
+
+  // When this PendingRemotenessChange was created, it was given a
+  // `mContentParent`.
+  if (mContentParent) {
+    mContentParent->RemoveKeepAlive();
+    mContentParent = nullptr;
+  }
+
+  // If we were given a specific group, stop keeping that group alive manually.
+  if (mSpecificGroup) {
+    mSpecificGroup->RemoveKeepAlive();
+    mSpecificGroup = nullptr;
+  }
+
+  mPromise = nullptr;
+  mTarget = nullptr;
+}
+
+CanonicalBrowsingContext::PendingRemotenessChange::PendingRemotenessChange(
+    CanonicalBrowsingContext* aTarget, RemotenessPromise::Private* aPromise,
+    uint64_t aPendingSwitchId, const NavigationIsolationOptions& aOptions)
+    : mTarget(aTarget),
+      mPromise(aPromise),
+      mPendingSwitchId(aPendingSwitchId),
+      mOptions(aOptions) {}
+
+CanonicalBrowsingContext::PendingRemotenessChange::~PendingRemotenessChange() {
+  MOZ_ASSERT(!mPromise && !mTarget && !mContentParent && !mSpecificGroup,
+             "should've already been Cancel() or Complete()-ed");
+}
+
+BrowserParent* CanonicalBrowsingContext::GetBrowserParent() const {
+  return mCurrentBrowserParent;
+}
+
+void CanonicalBrowsingContext::SetCurrentBrowserParent(
+    BrowserParent* aBrowserParent) {
+  MOZ_DIAGNOSTIC_ASSERT(!mCurrentBrowserParent || !aBrowserParent,
+                        "BrowsingContext already has a current BrowserParent!");
+  MOZ_DIAGNOSTIC_ASSERT_IF(aBrowserParent, aBrowserParent->CanSend());
+  MOZ_DIAGNOSTIC_ASSERT_IF(aBrowserParent,
+                           aBrowserParent->Manager()->ChildID() == mProcessId);
+
+  // BrowserParent must either be directly for this BrowsingContext, or the
+  // manager out our embedder WindowGlobal.
+  MOZ_DIAGNOSTIC_ASSERT_IF(
+      aBrowserParent && aBrowserParent->GetBrowsingContext() != this,
+      GetParentWindowContext() &&
+          GetParentWindowContext()->Manager() == aBrowserParent);
+
+  if (aBrowserParent && IsTopContent() && !ManuallyManagesActiveness()) {
+    aBrowserParent->SetRenderLayers(IsActive());
+  }
+
+  mCurrentBrowserParent = aBrowserParent;
+}
+
+bool CanonicalBrowsingContext::ManuallyManagesActiveness() const {
+  auto* el = GetEmbedderElement();
+  return el && el->IsXULElement() && el->HasAttr(nsGkAtoms::manualactiveness);
+}
+
+RefPtr<CanonicalBrowsingContext::RemotenessPromise>
+CanonicalBrowsingContext::ChangeRemoteness(
+    const NavigationIsolationOptions& aOptions, uint64_t aPendingSwitchId) {
+  MOZ_DIAGNOSTIC_ASSERT(IsContent(),
+                        "cannot change the process of chrome contexts");
+  MOZ_DIAGNOSTIC_ASSERT(
+      IsTop() == IsEmbeddedInProcess(0),
+      "toplevel content must be embedded in the parent process");
+  MOZ_DIAGNOSTIC_ASSERT(!aOptions.mReplaceBrowsingContext || IsTop(),
+                        "Cannot replace BrowsingContext for subframes");
+  MOZ_DIAGNOSTIC_ASSERT(
+      aOptions.mSpecificGroupId == 0 || aOptions.mReplaceBrowsingContext,
+      "Cannot specify group ID unless replacing BC");
+  MOZ_DIAGNOSTIC_ASSERT(aPendingSwitchId || !IsTop(),
+                        "Should always have aPendingSwitchId for top-level "
+                        "frames");
+
+  if (!AncestorsAreCurrent()) {
+    NS_WARNING("An ancestor context is no longer current");
+    return RemotenessPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
+  }
+
+  // Ensure our embedder hasn't been destroyed or asked to shutdown already.
+  RefPtr<WindowGlobalParent> embedderWindowGlobal = GetEmbedderWindowGlobal();
+  if (!embedderWindowGlobal) {
+    NS_WARNING("Non-embedded BrowsingContext");
+    return RemotenessPromise::CreateAndReject(NS_ERROR_UNEXPECTED, __func__);
+  }
+
+  if (!embedderWindowGlobal->CanSend()) {
+    NS_WARNING("Embedder already been destroyed.");
+    return RemotenessPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+  }
+
+  RefPtr<BrowserParent> embedderBrowser =
+      embedderWindowGlobal->GetBrowserParent();
+  if (embedderBrowser && embedderBrowser->Manager()->IsShuttingDown()) {
+    NS_WARNING("Embedder already asked to shutdown.");
+    return RemotenessPromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE, __func__);
+  }
+
+  if (aOptions.mRemoteType.IsEmpty() && (!IsTop() || !GetEmbedderElement())) {
+    NS_WARNING("Cannot load non-remote subframes");
+    return RemotenessPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
+  }
+
+  // Cancel ongoing remoteness changes.
+  if (mPendingRemotenessChange) {
+    mPendingRemotenessChange->Cancel(NS_ERROR_ABORT);
+    MOZ_DIAGNOSTIC_ASSERT(!mPendingRemotenessChange, "Should have cleared");
+  }
+
+  auto promise = MakeRefPtr<RemotenessPromise::Private>(__func__);
+  promise->UseDirectTaskDispatch(__func__);
+
+  RefPtr<PendingRemotenessChange> change =
+      new PendingRemotenessChange(this, promise, aPendingSwitchId, aOptions);
+  mPendingRemotenessChange = change;
+
+  // If a specific BrowsingContextGroup ID was specified for this load, make
+  // sure to keep it alive until the process switch is completed.
+  if (aOptions.mSpecificGroupId) {
+    change->mSpecificGroup =
+        BrowsingContextGroup::GetOrCreate(aOptions.mSpecificGroupId);
+    change->mSpecificGroup->AddKeepAlive();
+  }
+
+  // Call `prepareToChangeRemoteness` in parallel with starting a new process
+  // for <browser> loads.
+  if (IsTop() && GetEmbedderElement()) {
+    nsCOMPtr<nsIBrowser> browser = GetEmbedderElement()->AsBrowser();
+    if (!browser) {
+      change->Cancel(NS_ERROR_FAILURE);
+      return promise.forget();
+    }
+
+    RefPtr<Promise> blocker;
+    nsresult rv = browser->PrepareToChangeRemoteness(getter_AddRefs(blocker));
+    if (NS_FAILED(rv)) {
+      change->Cancel(rv);
+      return promise.forget();
+    }
+
+    // Mark prepareToChange as unresolved, and wait for it to become resolved.
+    if (blocker && blocker->State() != Promise::PromiseState::Resolved) {
+      change->mWaitingForPrepareToChange = true;
+      blocker->AddCallbacksWithCycleCollectedArgs(
+          [change](JSContext*, JS::Handle<JS::Value>, ErrorResult&) {
+            change->mWaitingForPrepareToChange = false;
+            change->MaybeFinish();
+          },
+          [change](JSContext*, JS::Handle<JS::Value> aValue, ErrorResult&) {
+            change->Cancel(
+                Promise::TryExtractNSResultFromRejectionValue(aValue));
+          });
+    }
+  }
+
+  // Switching a subframe to be local within it's embedding process.
+  if (embedderBrowser &&
+      aOptions.mRemoteType == embedderBrowser->Manager()->GetRemoteType()) {
+    MOZ_DIAGNOSTIC_ASSERT(
+        aPendingSwitchId,
+        "We always have a PendingSwitchId, except for print-preview loads, "
+        "which will never perform a process-switch to being in-process with "
+        "their embedder");
+    MOZ_DIAGNOSTIC_ASSERT(!aOptions.mReplaceBrowsingContext);
+    MOZ_DIAGNOSTIC_ASSERT(!aOptions.mRemoteType.IsEmpty());
+    MOZ_DIAGNOSTIC_ASSERT(!change->mWaitingForPrepareToChange);
+    MOZ_DIAGNOSTIC_ASSERT(!change->mSpecificGroup);
+
+    // Switching to local, so we don't need to create a new process, and will
+    // instead use our embedder process.
+    change->mContentParent = embedderBrowser->Manager();
+    change->mContentParent->AddKeepAlive();
+    change->ProcessLaunched();
+    return promise.forget();
+  }
+
+  // Switching to the parent process.
+  if (aOptions.mRemoteType.IsEmpty()) {
+    change->ProcessLaunched();
+    return promise.forget();
+  }
+
+  // If we're aiming to end up in a new process of the same type as our old
+  // process, and then putting our previous document in the BFCache, try to stay
+  // in the same process to avoid creating new processes unnecessarily.
+  RefPtr<ContentParent> existingProcess = GetContentParent();
+  if (existingProcess && !existingProcess->IsShuttingDown() &&
+      aOptions.mReplaceBrowsingContext &&
+      aOptions.mRemoteType == existingProcess->GetRemoteType()) {
+    change->mContentParent = existingProcess;
+    change->mContentParent->AddKeepAlive();
+    change->ProcessLaunched();
+    return promise.forget();
+  }
+
+  // Try to predict which BrowsingContextGroup will be used for the final load
+  // in this BrowsingContext. This has to be accurate if switching into an
+  // existing group, as it will control what pool of processes will be used
+  // for process selection.
+  //
+  // It's _technically_ OK to provide a group here if we're actually going to
+  // switch into a brand new group, though it's sub-optimal, as it can
+  // restrict the set of processes we're using.
+  BrowsingContextGroup* finalGroup =
+      aOptions.mReplaceBrowsingContext ? change->mSpecificGroup.get() : Group();
+
+  bool preferUsed =
+      StaticPrefs::browser_tabs_remote_subframesPreferUsed() && !IsTop();
+
+  change->mContentParent = ContentParent::GetNewOrUsedLaunchingBrowserProcess(
+      /* aRemoteType = */ aOptions.mRemoteType,
+      /* aGroup = */ finalGroup,
+      /* aPriority = */ hal::PROCESS_PRIORITY_FOREGROUND,
+      /* aPreferUsed = */ preferUsed);
+  if (!change->mContentParent) {
+    change->Cancel(NS_ERROR_FAILURE);
+    return promise.forget();
+  }
+
+  // Add a KeepAlive used by this ContentParent, which will be cleared when
+  // the change is complete. This should prevent the process dying before
+  // we're ready to use it.
+  change->mContentParent->AddKeepAlive();
+  if (change->mContentParent->IsLaunching()) {
+    change->mContentParent->WaitForLaunchAsync()->Then(
+        GetMainThreadSerialEventTarget(), __func__,
+        [change](ContentParent*) { change->ProcessLaunched(); },
+        [change]() { change->Cancel(NS_ERROR_FAILURE); });
+  } else {
+    change->ProcessLaunched();
+  }
+  return promise.forget();
+}
+
+void CanonicalBrowsingContext::MaybeSetPermanentKey(Element* aEmbedder) {
+  MOZ_DIAGNOSTIC_ASSERT(IsTop());
+
+  if (aEmbedder) {
+    if (nsCOMPtr<nsIBrowser> browser = aEmbedder->AsBrowser()) {
+      JS::Rooted<JS::Value> key(RootingCx());
+      if (NS_SUCCEEDED(browser->GetPermanentKey(&key)) && key.isObject()) {
+        mPermanentKey = key;
+      }
+    }
+  }
+}
+
+MediaController* CanonicalBrowsingContext::GetMediaController() {
+  // We would only create one media controller per tab, so accessing the
+  // controller via the top-level browsing context.
+  if (GetParent()) {
+    return Cast(Top())->GetMediaController();
+  }
+
+  MOZ_ASSERT(!GetParent(),
+             "Must access the controller from the top-level browsing context!");
+  // Only content browsing context can create media controller, we won't create
+  // controller for chrome document, such as the browser UI.
+  if (!mTabMediaController && !IsDiscarded() && IsContent()) {
+    mTabMediaController = new MediaController(Id());
+  }
+  return mTabMediaController;
+}
+
+bool CanonicalBrowsingContext::HasCreatedMediaController() const {
+  return !!mTabMediaController;
+}
+
+bool CanonicalBrowsingContext::SupportsLoadingInParent(
+    nsDocShellLoadState* aLoadState, uint64_t* aOuterWindowId) {
+  // We currently don't support initiating loads in the parent when they are
+  // watched by devtools. This is because devtools tracks loads using content
+  // process notifications, which happens after the load is initiated in this
+  // case. Devtools clears all prior requests when it detects a new navigation,
+  // so it drops the main document load that happened here.
+  if (WatchedByDevTools()) {
+    return false;
+  }
+
+  // Session-history-in-parent implementation relies currently on getting a
+  // round trip through a child process.
+  if (aLoadState->LoadIsFromSessionHistory()) {
+    return false;
+  }
+
+  // DocumentChannel currently only supports connecting channels into the
+  // content process, so we can only support schemes that will always be loaded
+  // there for now. Restrict to just http(s) for simplicity.
+  if (!net::SchemeIsHTTP(aLoadState->URI()) &&
+      !net::SchemeIsHTTPS(aLoadState->URI())) {
+    return false;
+  }
+
+  if (WindowGlobalParent* global = GetCurrentWindowGlobal()) {
+    nsCOMPtr<nsIURI> currentURI = global->GetDocumentURI();
+    if (currentURI) {
+      bool newURIHasRef = false;
+      aLoadState->URI()->GetHasRef(&newURIHasRef);
+      bool equalsExceptRef = false;
+      aLoadState->URI()->EqualsExceptRef(currentURI, &equalsExceptRef);
+
+      if (equalsExceptRef && newURIHasRef) {
+        // This navigation is same-doc WRT the current one, we should pass it
+        // down to the docshell to be handled.
+        return false;
+      }
+    }
+    // If the current document has a beforeunload listener, then we need to
+    // start the load in that process after we fire the event.
+    if (global->HasBeforeUnload()) {
+      return false;
+    }
+
+    *aOuterWindowId = global->OuterWindowId();
+  }
+  return true;
+}
+
+bool CanonicalBrowsingContext::LoadInParent(nsDocShellLoadState* aLoadState,
+                                            bool aSetNavigating) {
+  // We currently only support starting loads directly from the
+  // CanonicalBrowsingContext for top-level BCs.
+  // We currently only support starting loads directly from the
+  // CanonicalBrowsingContext for top-level BCs.
+  if (!IsTopContent() || !GetContentParent() ||
+      !StaticPrefs::browser_tabs_documentchannel_parent_controlled()) {
+    return false;
+  }
+
+  uint64_t outerWindowId = 0;
+  if (!SupportsLoadingInParent(aLoadState, &outerWindowId)) {
+    return false;
+  }
+
+  MOZ_ASSERT(!net::SchemeIsJavascript(aLoadState->URI()));
+
+  MOZ_ALWAYS_SUCCEEDS(
+      SetParentInitiatedNavigationEpoch(++gParentInitiatedNavigationEpoch));
+  // Note: If successful, this will recurse into StartDocumentLoad and
+  // set mCurrentLoad to the DocumentLoadListener instance created.
+  // Ideally in the future we will only start loads from here, and we can
+  // just set this directly instead.
+  return net::DocumentLoadListener::LoadInParent(this, aLoadState,
+                                                 aSetNavigating);
+}
+
+bool CanonicalBrowsingContext::AttemptSpeculativeLoadInParent(
+    nsDocShellLoadState* aLoadState) {
+  // We currently only support starting loads directly from the
+  // CanonicalBrowsingContext for top-level BCs.
+  // We currently only support starting loads directly from the
+  // CanonicalBrowsingContext for top-level BCs.
+  if (!IsTopContent() || !GetContentParent() ||
+      (StaticPrefs::browser_tabs_documentchannel_parent_controlled())) {
+    return false;
+  }
+
+  uint64_t outerWindowId = 0;
+  if (!SupportsLoadingInParent(aLoadState, &outerWindowId)) {
+    return false;
+  }
+
+  // If we successfully open the DocumentChannel, then it'll register
+  // itself using aLoadIdentifier and be kept alive until it completes
+  // loading.
+  return net::DocumentLoadListener::SpeculativeLoadInParent(this, aLoadState);
+}
+
+bool CanonicalBrowsingContext::StartDocumentLoad(
+    net::DocumentLoadListener* aLoad) {
+  // If we're controlling loads from the parent, then starting a new load means
+  // that we need to cancel any existing ones.
+  if (StaticPrefs::browser_tabs_documentchannel_parent_controlled() &&
+      mCurrentLoad) {
+    // Make sure we are not loading a javascript URI.
+    MOZ_ASSERT(!aLoad->IsLoadingJSURI());
+
+    // If we want to do a download, don't cancel the current navigation.
+    if (!aLoad->IsDownload()) {
+      mCurrentLoad->Cancel(NS_BINDING_CANCELLED_OLD_LOAD, ""_ns);
+    }
+  }
+  mCurrentLoad = aLoad;
+
+  if (NS_FAILED(SetCurrentLoadIdentifier(Some(aLoad->GetLoadIdentifier())))) {
+    mCurrentLoad = nullptr;
+    return false;
+  }
+
+  return true;
+}
+
+void CanonicalBrowsingContext::EndDocumentLoad(bool aContinueNavigating) {
+  mCurrentLoad = nullptr;
+
+  if (!aContinueNavigating) {
+    // Resetting the current load identifier on a discarded context
+    // has no effect when a document load has finished.
+    Unused << SetCurrentLoadIdentifier(Nothing());
+  }
+}
+
+already_AddRefed<nsIURI> CanonicalBrowsingContext::GetCurrentURI() const {
+  nsCOMPtr<nsIURI> currentURI;
+  if (nsIDocShell* docShell = GetDocShell()) {
+    MOZ_ALWAYS_SUCCEEDS(
+        nsDocShell::Cast(docShell)->GetCurrentURI(getter_AddRefs(currentURI)));
+  } else {
+    currentURI = mCurrentRemoteURI;
+  }
+  return currentURI.forget();
+}
+
+void CanonicalBrowsingContext::SetCurrentRemoteURI(nsIURI* aCurrentRemoteURI) {
+  MOZ_ASSERT(!GetDocShell());
+  mCurrentRemoteURI = aCurrentRemoteURI;
+}
+
+void CanonicalBrowsingContext::ResetSHEntryHasUserInteractionCache() {
+  WindowContext* topWc = GetTopWindowContext();
+  if (topWc && !topWc->IsDiscarded()) {
+    MOZ_ALWAYS_SUCCEEDS(topWc->SetSHEntryHasUserInteraction(false));
+  }
+}
+
+void CanonicalBrowsingContext::HistoryCommitIndexAndLength() {
+  nsID changeID = {};
+  CallerWillNotifyHistoryIndexAndLengthChanges caller(nullptr);
+  HistoryCommitIndexAndLength(changeID, caller);
+}
+void CanonicalBrowsingContext::HistoryCommitIndexAndLength(
+    const nsID& aChangeID,
+    const CallerWillNotifyHistoryIndexAndLengthChanges& aProofOfCaller) {
+  if (!IsTop()) {
+    Cast(Top())->HistoryCommitIndexAndLength(aChangeID, aProofOfCaller);
+    return;
+  }
+
+  nsISHistory* shistory = GetSessionHistory();
+  if (!shistory) {
+    return;
+  }
+  int32_t index = 0;
+  shistory->GetIndex(&index);
+  int32_t length = shistory->GetCount();
+
+  GetChildSessionHistory()->SetIndexAndLength(index, length, aChangeID);
+
+  shistory->EvictOutOfRangeDocumentViewers(index);
+
+  Group()->EachParent([&](ContentParent* aParent) {
+    Unused << aParent->SendHistoryCommitIndexAndLength(this, index, length,
+                                                       aChangeID);
+  });
+}
+
+void CanonicalBrowsingContext::SynchronizeLayoutHistoryState() {
+  if (mActiveEntry) {
+    if (IsInProcess()) {
+      nsIDocShell* docShell = GetDocShell();
+      if (docShell) {
+        docShell->PersistLayoutHistoryState();
+
+        nsCOMPtr<nsILayoutHistoryState> state;
+        docShell->GetLayoutHistoryState(getter_AddRefs(state));
+        if (state) {
+          mActiveEntry->SetLayoutHistoryState(state);
+        }
+      }
+    } else if (ContentParent* cp = GetContentParent()) {
+      cp->SendGetLayoutHistoryState(this)->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [activeEntry = mActiveEntry](
+              const std::tuple<RefPtr<nsILayoutHistoryState>, Maybe<Wireframe>>&
+                  aResult) {
+            if (std::get<0>(aResult)) {
+              activeEntry->SetLayoutHistoryState(std::get<0>(aResult));
+            }
+            if (std::get<1>(aResult)) {
+              activeEntry->SetWireframe(std::get<1>(aResult));
+            }
+          },
+          []() {});
+    }
+  }
+}
+
+void CanonicalBrowsingContext::ResetScalingZoom() {
+  // This currently only ever gets called in the parent process, and we
+  // pass the message on to the WindowGlobalChild for the rootmost browsing
+  // context.
+  if (WindowGlobalParent* topWindow = GetTopWindowContext()) {
+    Unused << topWindow->SendResetScalingZoom();
+  }
+}
+
+void CanonicalBrowsingContext::SetRestoreData(SessionStoreRestoreData* aData,
+                                              ErrorResult& aError) {
+  MOZ_DIAGNOSTIC_ASSERT(aData);
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(GetParentObject());
+  RefPtr<Promise> promise = Promise::Create(global, aError);
+  if (aError.Failed()) {
+    return;
+  }
+
+  if (NS_WARN_IF(NS_FAILED(SetHasRestoreData(true)))) {
+    aError.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  mRestoreState = new RestoreState();
+  mRestoreState->mData = aData;
+  mRestoreState->mPromise = promise;
+}
+
+already_AddRefed<Promise> CanonicalBrowsingContext::GetRestorePromise() {
+  if (mRestoreState) {
+    return do_AddRef(mRestoreState->mPromise);
+  }
+  return nullptr;
+}
+
+void CanonicalBrowsingContext::ClearRestoreState() {
+  if (!mRestoreState) {
+    MOZ_DIAGNOSTIC_ASSERT(!GetHasRestoreData());
+    return;
+  }
+  if (mRestoreState->mPromise) {
+    mRestoreState->mPromise->MaybeRejectWithUndefined();
+  }
+  mRestoreState = nullptr;
+  MOZ_ALWAYS_SUCCEEDS(SetHasRestoreData(false));
+}
+
+void CanonicalBrowsingContext::RequestRestoreTabContent(
+    WindowGlobalParent* aWindow) {
+  MOZ_DIAGNOSTIC_ASSERT(IsTop());
+
+  if (IsDiscarded() || !mRestoreState || !mRestoreState->mData) {
+    return;
+  }
+
+  CanonicalBrowsingContext* context = aWindow->GetBrowsingContext();
+  MOZ_DIAGNOSTIC_ASSERT(!context->IsDiscarded());
+
+  RefPtr<SessionStoreRestoreData> data =
+      mRestoreState->mData->FindDataForChild(context);
+
+  if (context->IsTop()) {
+    MOZ_DIAGNOSTIC_ASSERT(context == this);
+
+    // We need to wait until the appropriate load event has fired before we
+    // can "complete" the restore process, so if we're holding an empty data
+    // object, just resolve the promise immediately.
+    if (mRestoreState->mData->IsEmpty()) {
+      MOZ_DIAGNOSTIC_ASSERT(!data || data->IsEmpty());
+      mRestoreState->Resolve();
+      ClearRestoreState();
+      return;
+    }
+
+    // Since we're following load event order, we'll only arrive here for a
+    // toplevel context after we've already sent down data for all child frames,
+    // so it's safe to clear this reference now. The completion callback below
+    // relies on the mData field being null to determine if all requests have
+    // been sent out.
+    mRestoreState->ClearData();
+    MOZ_ALWAYS_SUCCEEDS(SetHasRestoreData(false));
+  }
+
+  if (data && !data->IsEmpty()) {
+    auto onTabRestoreComplete = [self = RefPtr{this},
+                                 state = RefPtr{mRestoreState}](auto) {
+      state->mResolves++;
+      if (!state->mData && state->mRequests == state->mResolves) {
+        state->Resolve();
+        if (state == self->mRestoreState) {
+          self->ClearRestoreState();
+        }
+      }
+    };
+
+    mRestoreState->mRequests++;
+
+    if (data->CanRestoreInto(aWindow->GetDocumentURI())) {
+      if (!aWindow->IsInProcess()) {
+        aWindow->SendRestoreTabContent(WrapNotNull(data.get()),
+                                       onTabRestoreComplete,
+                                       onTabRestoreComplete);
+        return;
+      }
+      data->RestoreInto(context);
+    }
+
+    // This must be called both when we're doing an in-process restore, and when
+    // we didn't do a restore at all due to a URL mismatch.
+    onTabRestoreComplete(true);
+  }
+}
+
+void CanonicalBrowsingContext::RestoreState::Resolve() {
+  MOZ_DIAGNOSTIC_ASSERT(mPromise);
+  mPromise->MaybeResolveWithUndefined();
+  mPromise = nullptr;
+}
+
+nsresult CanonicalBrowsingContext::WriteSessionStorageToSessionStore(
+    const nsTArray<SSCacheCopy>& aSesssionStorage, uint32_t aEpoch) {
+  nsCOMPtr<nsISessionStoreFunctions> funcs = do_ImportESModule(
+      "resource://gre/modules/SessionStoreFunctions.sys.mjs", fallible);
+  if (!funcs) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIXPConnectWrappedJS> wrapped = do_QueryInterface(funcs);
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(wrapped->GetJSObjectGlobal())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  JS::Rooted<JS::Value> key(jsapi.cx(), Top()->PermanentKey());
+
+  Record<nsCString, Record<nsString, nsString>> storage;
+  JS::Rooted<JS::Value> update(jsapi.cx());
+
+  if (!aSesssionStorage.IsEmpty()) {
+    SessionStoreUtils::ConstructSessionStorageValues(this, aSesssionStorage,
+                                                     storage);
+    if (!ToJSValue(jsapi.cx(), storage, &update)) {
+      return NS_ERROR_FAILURE;
+    }
+  } else {
+    update.setNull();
+  }
+
+  return funcs->UpdateSessionStoreForStorage(Top()->GetEmbedderElement(), this,
+                                             key, aEpoch, update);
+}
+
+void CanonicalBrowsingContext::UpdateSessionStoreSessionStorage(
+    const std::function<void()>& aDone) {
+  if (!StaticPrefs::browser_sessionstore_collect_session_storage_AtStartup()) {
+    aDone();
+    return;
+  }
+
+  using DataPromise = BackgroundSessionStorageManager::DataPromise;
+  BackgroundSessionStorageManager::GetData(
+      this, StaticPrefs::browser_sessionstore_dom_storage_limit(),
+      /* aClearSessionStoreTimer = */ true)
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [self = RefPtr{this}, aDone, epoch = GetSessionStoreEpoch()](
+                 const DataPromise::ResolveOrRejectValue& valueList) {
+               if (valueList.IsResolve()) {
+                 self->WriteSessionStorageToSessionStore(
+                     valueList.ResolveValue(), epoch);
+               }
+               aDone();
+             });
+}
+
+/* static */
+void CanonicalBrowsingContext::UpdateSessionStoreForStorage(
+    uint64_t aBrowsingContextId) {
+  RefPtr<CanonicalBrowsingContext> browsingContext = Get(aBrowsingContextId);
+
+  if (!browsingContext) {
+    return;
+  }
+
+  browsingContext->UpdateSessionStoreSessionStorage([]() {});
+}
+
+void CanonicalBrowsingContext::MaybeScheduleSessionStoreUpdate() {
+  if (!StaticPrefs::browser_sessionstore_platform_collection_AtStartup()) {
+    return;
+  }
+
+  if (!IsTop()) {
+    Top()->MaybeScheduleSessionStoreUpdate();
+    return;
+  }
+
+  if (IsInBFCache()) {
+    return;
+  }
+
+  if (mSessionStoreSessionStorageUpdateTimer) {
+    return;
+  }
+
+  if (!StaticPrefs::browser_sessionstore_debug_no_auto_updates()) {
+    auto result = NS_NewTimerWithFuncCallback(
+        [](nsITimer*, void* aClosure) {
+          auto* context = static_cast<CanonicalBrowsingContext*>(aClosure);
+          context->UpdateSessionStoreSessionStorage([]() {});
+        },
+        this, StaticPrefs::browser_sessionstore_interval(),
+        nsITimer::TYPE_ONE_SHOT,
+        "CanonicalBrowsingContext::MaybeScheduleSessionStoreUpdate");
+
+    if (result.isErr()) {
+      return;
+    }
+
+    mSessionStoreSessionStorageUpdateTimer = result.unwrap();
+  }
+}
+
+void CanonicalBrowsingContext::CancelSessionStoreUpdate() {
+  if (mSessionStoreSessionStorageUpdateTimer) {
+    mSessionStoreSessionStorageUpdateTimer->Cancel();
+    mSessionStoreSessionStorageUpdateTimer = nullptr;
+  }
+}
+
+void CanonicalBrowsingContext::SetContainerFeaturePolicy(
+    FeaturePolicy* aContainerFeaturePolicy) {
+  mContainerFeaturePolicy = aContainerFeaturePolicy;
+
+  if (WindowGlobalParent* current = GetCurrentWindowGlobal()) {
+    Unused << current->SendSetContainerFeaturePolicy(mContainerFeaturePolicy);
+  }
+}
+
+void CanonicalBrowsingContext::SetCrossGroupOpenerId(uint64_t aOpenerId) {
+  MOZ_DIAGNOSTIC_ASSERT(IsTopContent());
+  MOZ_DIAGNOSTIC_ASSERT(mCrossGroupOpenerId == 0,
+                        "Can only set CrossGroupOpenerId once");
+  mCrossGroupOpenerId = aOpenerId;
+}
+
+void CanonicalBrowsingContext::SetCrossGroupOpener(
+    CanonicalBrowsingContext& aCrossGroupOpener, ErrorResult& aRv) {
+  if (!IsTopContent()) {
+    aRv.ThrowNotAllowedError(
+        "Can only set crossGroupOpener on toplevel content");
+    return;
+  }
+  if (mCrossGroupOpenerId != 0) {
+    aRv.ThrowNotAllowedError("Can only set crossGroupOpener once");
+    return;
+  }
+
+  SetCrossGroupOpenerId(aCrossGroupOpener.Id());
+}
+
+auto CanonicalBrowsingContext::FindUnloadingHost(uint64_t aChildID)
+    -> nsTArray<UnloadingHost>::iterator {
+  return std::find_if(
+      mUnloadingHosts.begin(), mUnloadingHosts.end(),
+      [&](const auto& host) { return host.mChildID == aChildID; });
+}
+
+void CanonicalBrowsingContext::ClearUnloadingHost(uint64_t aChildID) {
+  // Notify any callbacks which were waiting for the host to finish unloading
+  // that it has.
+  auto found = FindUnloadingHost(aChildID);
+  if (found != mUnloadingHosts.end()) {
+    auto callbacks = std::move(found->mCallbacks);
+    mUnloadingHosts.RemoveElementAt(found);
+    for (const auto& callback : callbacks) {
+      callback();
+    }
+  }
+}
+
+void CanonicalBrowsingContext::StartUnloadingHost(uint64_t aChildID) {
+  MOZ_DIAGNOSTIC_ASSERT(FindUnloadingHost(aChildID) == mUnloadingHosts.end());
+  mUnloadingHosts.AppendElement(UnloadingHost{aChildID, {}});
+}
+
+void CanonicalBrowsingContext::BrowserParentDestroyed(
+    BrowserParent* aBrowserParent, bool aAbnormalShutdown) {
+  ClearUnloadingHost(aBrowserParent->Manager()->ChildID());
+
+  // Handling specific to when the current BrowserParent has been destroyed.
+  if (mCurrentBrowserParent == aBrowserParent) {
+    mCurrentBrowserParent = nullptr;
+
+    // If this BrowserParent is for a subframe, attempt to recover from a
+    // subframe crash by rendering the subframe crashed page in the embedding
+    // content.
+    if (aAbnormalShutdown) {
+      ShowSubframeCrashedUI(aBrowserParent->GetBrowserBridgeParent());
+    }
+  }
+}
+
+void CanonicalBrowsingContext::ShowSubframeCrashedUI(
+    BrowserBridgeParent* aBridge) {
+  if (!aBridge || IsDiscarded() || !aBridge->CanSend()) {
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(!aBridge->GetBrowsingContext() ||
+                        aBridge->GetBrowsingContext() == this);
+
+  // There is no longer a current inner window within this
+  // BrowsingContext, update the `CurrentInnerWindowId` field to reflect
+  // this.
+  MOZ_ALWAYS_SUCCEEDS(SetCurrentInnerWindowId(0));
+
+  // The owning process will now be the embedder to render the subframe
+  // crashed page, switch ownership back over.
+  SetOwnerProcessId(aBridge->Manager()->Manager()->ChildID());
+  SetCurrentBrowserParent(aBridge->Manager());
+
+  Unused << aBridge->SendSubFrameCrashed();
+}
+
+static void LogBFCacheBlockingForDoc(BrowsingContext* aBrowsingContext,
+                                     uint32_t aBFCacheCombo, bool aIsSubDoc) {
+  if (aIsSubDoc) {
+    nsAutoCString uri("[no uri]");
+    nsCOMPtr<nsIURI> currentURI =
+        aBrowsingContext->Canonical()->GetCurrentURI();
+    if (currentURI) {
+      uri = currentURI->GetSpecOrDefault();
+    }
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug,
+            (" ** Blocked for document %s", uri.get()));
+  }
+  if (aBFCacheCombo & BFCacheStatus::EVENT_HANDLING_SUPPRESSED) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug,
+            (" * event handling suppression"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::SUSPENDED) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * suspended Window"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::UNLOAD_LISTENER) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * unload listener"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::REQUEST) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * requests in the loadgroup"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::ACTIVE_GET_USER_MEDIA) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * GetUserMedia"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::ACTIVE_PEER_CONNECTION) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * PeerConnection"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::CONTAINS_EME_CONTENT) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * EME content"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::CONTAINS_MSE_CONTENT) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * MSE use"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::HAS_ACTIVE_SPEECH_SYNTHESIS) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * Speech use"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::HAS_USED_VR) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * used VR"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::BEFOREUNLOAD_LISTENER) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * beforeunload listener"));
+  }
+  if (aBFCacheCombo & BFCacheStatus::ACTIVE_LOCK) {
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * has active Web Locks"));
+  }
+}
+
+bool CanonicalBrowsingContext::AllowedInBFCache(
+    const Maybe<uint64_t>& aChannelId, nsIURI* aNewURI) {
+  if (MOZ_UNLIKELY(MOZ_LOG_TEST(gSHIPBFCacheLog, LogLevel::Debug))) {
+    nsAutoCString uri("[no uri]");
+    nsCOMPtr<nsIURI> currentURI = GetCurrentURI();
+    if (currentURI) {
+      uri = currentURI->GetSpecOrDefault();
+    }
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, ("Checking %s", uri.get()));
+  }
+
+  if (IsInProcess()) {
+    return false;
+  }
+
+  uint32_t bfcacheCombo = 0;
+  if (mRestoreState) {
+    bfcacheCombo |= BFCacheStatus::RESTORING;
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * during session restore"));
+  }
+
+  if (Group()->Toplevels().Length() > 1) {
+    bfcacheCombo |= BFCacheStatus::NOT_ONLY_TOPLEVEL_IN_BCG;
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug,
+            (" * auxiliary BrowsingContexts"));
+  }
+
+  // There are not a lot of about:* pages that are allowed to load in
+  // subframes, so it's OK to allow those few about:* pages enter BFCache.
+  MOZ_ASSERT(IsTop(), "Trying to put a non top level BC into BFCache");
+
+  WindowGlobalParent* wgp = GetCurrentWindowGlobal();
+  if (wgp && wgp->GetDocumentURI()) {
+    nsCOMPtr<nsIURI> currentURI = wgp->GetDocumentURI();
+    // Exempt about:* pages from bfcache, with the exception of about:blank
+    if (currentURI->SchemeIs("about") &&
+        !currentURI->GetSpecOrDefault().EqualsLiteral("about:blank")) {
+      bfcacheCombo |= BFCacheStatus::ABOUT_PAGE;
+      MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug, (" * about:* page"));
+    }
+
+    if (aNewURI) {
+      bool equalUri = false;
+      aNewURI->Equals(currentURI, &equalUri);
+      if (equalUri) {
+        // When loading the same uri, disable bfcache so that
+        // nsDocShell::OnNewURI transforms the load to LOAD_NORMAL_REPLACE.
+        return false;
+      }
+    }
+  }
+
+  // For telemetry we're collecting all the flags for all the BCs hanging
+  // from this top-level BC.
+  PreOrderWalk([&](BrowsingContext* aBrowsingContext) {
+    WindowGlobalParent* wgp =
+        aBrowsingContext->Canonical()->GetCurrentWindowGlobal();
+    uint32_t subDocBFCacheCombo = wgp ? wgp->GetBFCacheStatus() : 0;
+    if (wgp) {
+      const Maybe<uint64_t>& singleChannelId = wgp->GetSingleChannelId();
+      if (singleChannelId.isSome()) {
+        if (singleChannelId.value() == 0 || aChannelId.isNothing() ||
+            singleChannelId.value() != aChannelId.value()) {
+          subDocBFCacheCombo |= BFCacheStatus::REQUEST;
+        }
+      }
+    }
+
+    if (MOZ_UNLIKELY(MOZ_LOG_TEST(gSHIPBFCacheLog, LogLevel::Debug))) {
+      LogBFCacheBlockingForDoc(aBrowsingContext, subDocBFCacheCombo,
+                               aBrowsingContext != this);
+    }
+
+    bfcacheCombo |= subDocBFCacheCombo;
+  });
+
+  nsDocShell::ReportBFCacheComboTelemetry(bfcacheCombo);
+  if (MOZ_UNLIKELY(MOZ_LOG_TEST(gSHIPBFCacheLog, LogLevel::Debug))) {
+    nsAutoCString uri("[no uri]");
+    nsCOMPtr<nsIURI> currentURI = GetCurrentURI();
+    if (currentURI) {
+      uri = currentURI->GetSpecOrDefault();
+    }
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Debug,
+            (" +> %s %s be blocked from going into the BFCache", uri.get(),
+             bfcacheCombo == 0 ? "shouldn't" : "should"));
+  }
+
+  if (StaticPrefs::docshell_shistory_bfcache_allow_unload_listeners()) {
+    bfcacheCombo &= ~BFCacheStatus::UNLOAD_LISTENER;
+  }
+
+  return bfcacheCombo == 0;
+}
+
+void CanonicalBrowsingContext::SetTouchEventsOverride(
+    dom::TouchEventsOverride aOverride, ErrorResult& aRv) {
+  SetTouchEventsOverrideInternal(aOverride, aRv);
+}
+
+void CanonicalBrowsingContext::SetTargetTopLevelLinkClicksToBlank(
+    bool aTargetTopLevelLinkClicksToBlank, ErrorResult& aRv) {
+  SetTargetTopLevelLinkClicksToBlankInternal(aTargetTopLevelLinkClicksToBlank,
+                                             aRv);
+}
+
+void CanonicalBrowsingContext::AddPageAwakeRequest() {
+  MOZ_ASSERT(IsTop());
+  auto count = GetPageAwakeRequestCount();
+  MOZ_ASSERT(count < UINT32_MAX);
+  Unused << SetPageAwakeRequestCount(++count);
+}
+
+void CanonicalBrowsingContext::RemovePageAwakeRequest() {
+  MOZ_ASSERT(IsTop());
+  auto count = GetPageAwakeRequestCount();
+  MOZ_ASSERT(count > 0);
+  Unused << SetPageAwakeRequestCount(--count);
+}
+
+void CanonicalBrowsingContext::CloneDocumentTreeInto(
+    CanonicalBrowsingContext* aSource, const nsACString& aRemoteType,
+    embedding::PrintData&& aPrintData) {
+  NavigationIsolationOptions options;
+  options.mRemoteType = aRemoteType;
+
+  mClonePromise =
+      ChangeRemoteness(options, /* aPendingSwitchId = */ 0)
+          ->Then(
+              GetMainThreadSerialEventTarget(), __func__,
+              [source = MaybeDiscardedBrowsingContext{aSource},
+               data = std::move(aPrintData)](
+                  BrowserParent* aBp) -> RefPtr<GenericNonExclusivePromise> {
+                RefPtr<BrowserBridgeParent> bridge =
+                    aBp->GetBrowserBridgeParent();
+                return aBp->SendCloneDocumentTreeIntoSelf(source, data)
+                    ->Then(
+                        GetMainThreadSerialEventTarget(), __func__,
+                        [bridge](
+                            BrowserParent::CloneDocumentTreeIntoSelfPromise::
+                                ResolveOrRejectValue&& aValue) {
+                          // We're cloning a remote iframe, so we created a
+                          // BrowserBridge which makes us register an OOP load
+                          // (see Document::OOPChildLoadStarted), even though
+                          // this isn't a real load. We call
+                          // SendMaybeFireEmbedderLoadEvents here so that we do
+                          // register the end of the load (see
+                          // Document::OOPChildLoadDone).
+                          if (bridge) {
+                            Unused << bridge->SendMaybeFireEmbedderLoadEvents(
+                                EmbedderElementEventType::NoEvent);
+                          }
+                          if (aValue.IsResolve() && aValue.ResolveValue()) {
+                            return GenericNonExclusivePromise::CreateAndResolve(
+                                true, __func__);
+                          }
+                          return GenericNonExclusivePromise::CreateAndReject(
+                              NS_ERROR_FAILURE, __func__);
+                        });
+              },
+              [](nsresult aRv) -> RefPtr<GenericNonExclusivePromise> {
+                NS_WARNING(
+                    nsPrintfCString("Remote clone failed: %x\n", unsigned(aRv))
+                        .get());
+                return GenericNonExclusivePromise::CreateAndReject(
+                    NS_ERROR_FAILURE, __func__);
+              });
+
+  mClonePromise->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [self = RefPtr{this}]() { self->mClonePromise = nullptr; });
+}
+
+bool CanonicalBrowsingContext::StartApzAutoscroll(float aAnchorX,
+                                                  float aAnchorY,
+                                                  nsViewID aScrollId,
+                                                  uint32_t aPresShellId) {
+  nsCOMPtr<nsIWidget> widget;
+  mozilla::layers::LayersId layersId{0};
+
+  if (IsInProcess()) {
+    nsCOMPtr<nsPIDOMWindowOuter> outer = GetDOMWindow();
+    if (!outer) {
+      return false;
+    }
+
+    widget = widget::WidgetUtils::DOMWindowToWidget(outer);
+    if (widget) {
+      layersId = widget->GetRootLayerTreeId();
+    }
+  } else {
+    RefPtr<BrowserParent> parent = GetBrowserParent();
+    if (!parent) {
+      return false;
+    }
+
+    widget = parent->GetWidget();
+    layersId = parent->GetLayersId();
+  }
+
+  if (!widget || !widget->AsyncPanZoomEnabled()) {
+    return false;
+  }
+
+  // The anchor coordinates that are passed in are relative to the origin of the
+  // screen, but we are sending them to APZ which only knows about coordinates
+  // relative to the widget, so convert them accordingly.
+  const LayoutDeviceIntPoint anchor =
+      RoundedToInt(LayoutDevicePoint(aAnchorX, aAnchorY)) -
+      widget->WidgetToScreenOffset();
+
+  mozilla::layers::ScrollableLayerGuid guid(layersId, aPresShellId, aScrollId);
+
+  return widget->StartAsyncAutoscroll(
+      ViewAs<ScreenPixel>(
+          anchor, PixelCastJustification::LayoutDeviceIsScreenForBounds),
+      guid);
+}
+
+void CanonicalBrowsingContext::StopApzAutoscroll(nsViewID aScrollId,
+                                                 uint32_t aPresShellId) {
+  nsCOMPtr<nsIWidget> widget;
+  mozilla::layers::LayersId layersId{0};
+
+  if (IsInProcess()) {
+    nsCOMPtr<nsPIDOMWindowOuter> outer = GetDOMWindow();
+    if (!outer) {
+      return;
+    }
+
+    widget = widget::WidgetUtils::DOMWindowToWidget(outer);
+    if (widget) {
+      layersId = widget->GetRootLayerTreeId();
+    }
+  } else {
+    RefPtr<BrowserParent> parent = GetBrowserParent();
+    if (!parent) {
+      return;
+    }
+
+    widget = parent->GetWidget();
+    layersId = parent->GetLayersId();
+  }
+
+  if (!widget || !widget->AsyncPanZoomEnabled()) {
+    return;
+  }
+
+  mozilla::layers::ScrollableLayerGuid guid(layersId, aPresShellId, aScrollId);
+  widget->StopAsyncAutoscroll(guid);
+}
+
+already_AddRefed<nsISHEntry>
+CanonicalBrowsingContext::GetMostRecentLoadingSessionHistoryEntry() {
+  if (mLoadingEntries.IsEmpty()) {
+    return nullptr;
+  }
+
+  RefPtr<SessionHistoryEntry> entry = mLoadingEntries.LastElement().mEntry;
+  return entry.forget();
+}
+
+already_AddRefed<BounceTrackingState>
+CanonicalBrowsingContext::GetBounceTrackingState() {
+  if (!mWebProgress) {
+    return nullptr;
+  }
+  return mWebProgress->GetBounceTrackingState();
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(CanonicalBrowsingContext)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(CanonicalBrowsingContext,
+                                                BrowsingContext)
+  tmp->mPermanentKey.setNull();
+  if (tmp->mSessionHistory) {
+    tmp->mSessionHistory->SetBrowsingContext(nullptr);
+  }
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSessionHistory, mContainerFeaturePolicy,
+                                  mCurrentBrowserParent, mWebProgress,
+                                  mSessionStoreSessionStorageUpdateTimer)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(CanonicalBrowsingContext,
+                                                  BrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSessionHistory, mContainerFeaturePolicy,
+                                    mCurrentBrowserParent, mWebProgress,
+                                    mSessionStoreSessionStorageUpdateTimer)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(CanonicalBrowsingContext,
+                                               BrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mPermanentKey)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_ADDREF_INHERITED(CanonicalBrowsingContext, BrowsingContext)
+NS_IMPL_RELEASE_INHERITED(CanonicalBrowsingContext, BrowsingContext)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(CanonicalBrowsingContext)
+NS_INTERFACE_MAP_END_INHERITING(BrowsingContext)
+
+}  // namespace mozilla::dom
diff --git a/docshell/base/CanonicalBrowsingContext.h b/docshell/base/CanonicalBrowsingContext.h
new file mode 100644
index 0000000000..132c9f2157
--- /dev/null
+++ b/docshell/base/CanonicalBrowsingContext.h
@@ -0,0 +1,620 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_CanonicalBrowsingContext_h
+#define mozilla_dom_CanonicalBrowsingContext_h
+
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/MediaControlKeySource.h"
+#include "mozilla/dom/BrowsingContextWebProgress.h"
+#include "mozilla/dom/ProcessIsolation.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/SessionHistoryEntry.h"
+#include "mozilla/dom/SessionStoreRestoreData.h"
+#include "mozilla/dom/SessionStoreUtils.h"
+#include "mozilla/dom/ipc/IdType.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/MozPromise.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsWrapperCache.h"
+#include "nsTArray.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsISecureBrowserUI.h"
+
+class nsIBrowserDOMWindow;
+class nsISHistory;
+class nsIWidget;
+class nsIPrintSettings;
+class nsSHistory;
+class nsBrowserStatusFilter;
+class nsSecureBrowserUI;
+class CallerWillNotifyHistoryIndexAndLengthChanges;
+class nsITimer;
+
+namespace mozilla {
+enum class CallState;
+class BounceTrackingState;
+
+namespace embedding {
+class PrintData;
+}
+
+namespace net {
+class DocumentLoadListener;
+}
+
+namespace dom {
+
+class BrowserParent;
+class BrowserBridgeParent;
+class FeaturePolicy;
+struct LoadURIOptions;
+class MediaController;
+struct LoadingSessionHistoryInfo;
+class SSCacheCopy;
+class WindowGlobalParent;
+class SessionStoreFormData;
+class SessionStoreScrollData;
+
+// CanonicalBrowsingContext is a BrowsingContext living in the parent
+// process, with whatever extra data that a BrowsingContext in the
+// parent needs.
+class CanonicalBrowsingContext final : public BrowsingContext {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(
+      CanonicalBrowsingContext, BrowsingContext)
+
+  static already_AddRefed<CanonicalBrowsingContext> Get(uint64_t aId);
+  static CanonicalBrowsingContext* Cast(BrowsingContext* aContext);
+  static const CanonicalBrowsingContext* Cast(const BrowsingContext* aContext);
+  static already_AddRefed<CanonicalBrowsingContext> Cast(
+      already_AddRefed<BrowsingContext>&& aContext);
+
+  bool IsOwnedByProcess(uint64_t aProcessId) const {
+    return mProcessId == aProcessId;
+  }
+  bool IsEmbeddedInProcess(uint64_t aProcessId) const {
+    return mEmbedderProcessId == aProcessId;
+  }
+  uint64_t OwnerProcessId() const { return mProcessId; }
+  uint64_t EmbedderProcessId() const { return mEmbedderProcessId; }
+  ContentParent* GetContentParent() const;
+
+  void GetCurrentRemoteType(nsACString& aRemoteType, ErrorResult& aRv) const;
+
+  void SetOwnerProcessId(uint64_t aProcessId);
+
+  // The ID of the BrowsingContext which caused this BrowsingContext to be
+  // opened, or `0` if this is unknown.
+  // Only set for toplevel content BrowsingContexts, and may be from a different
+  // BrowsingContextGroup.
+  uint64_t GetCrossGroupOpenerId() const { return mCrossGroupOpenerId; }
+  void SetCrossGroupOpenerId(uint64_t aOpenerId);
+  void SetCrossGroupOpener(CanonicalBrowsingContext& aCrossGroupOpener,
+                           ErrorResult& aRv);
+
+  void GetWindowGlobals(nsTArray<RefPtr<WindowGlobalParent>>& aWindows);
+
+  // The current active WindowGlobal.
+  WindowGlobalParent* GetCurrentWindowGlobal() const;
+
+  // Same as the methods on `BrowsingContext`, but with the types already cast
+  // to the parent process type.
+  CanonicalBrowsingContext* GetParent() {
+    return Cast(BrowsingContext::GetParent());
+  }
+  CanonicalBrowsingContext* Top() { return Cast(BrowsingContext::Top()); }
+  WindowGlobalParent* GetParentWindowContext();
+  WindowGlobalParent* GetTopWindowContext();
+
+  already_AddRefed<nsIWidget> GetParentProcessWidgetContaining();
+  already_AddRefed<nsIBrowserDOMWindow> GetBrowserDOMWindow();
+
+  // Same as `GetParentWindowContext`, but will also cross <browser> and
+  // content/chrome boundaries.
+  already_AddRefed<WindowGlobalParent> GetEmbedderWindowGlobal() const;
+
+  CanonicalBrowsingContext* GetParentCrossChromeBoundary();
+  CanonicalBrowsingContext* TopCrossChromeBoundary();
+  Nullable<WindowProxyHolder> GetTopChromeWindow();
+
+  nsISHistory* GetSessionHistory();
+  SessionHistoryEntry* GetActiveSessionHistoryEntry();
+  void SetActiveSessionHistoryEntry(SessionHistoryEntry* aEntry);
+
+  bool ManuallyManagesActiveness() const;
+
+  UniquePtr<LoadingSessionHistoryInfo> CreateLoadingSessionHistoryEntryForLoad(
+      nsDocShellLoadState* aLoadState, SessionHistoryEntry* aExistingEntry,
+      nsIChannel* aChannel);
+
+  UniquePtr<LoadingSessionHistoryInfo> ReplaceLoadingSessionHistoryEntryForLoad(
+      LoadingSessionHistoryInfo* aInfo, nsIChannel* aNewChannel);
+
+  using PrintPromise = MozPromise</* unused */ bool, nsresult, false>;
+  MOZ_CAN_RUN_SCRIPT RefPtr<PrintPromise> Print(nsIPrintSettings*);
+  MOZ_CAN_RUN_SCRIPT already_AddRefed<Promise> PrintJS(nsIPrintSettings*,
+                                                       ErrorResult&);
+
+  // Call the given callback on all top-level descendant BrowsingContexts.
+  // Return Callstate::Stop from the callback to stop calling further children.
+  //
+  // If aIncludeNestedBrowsers is true, then all top descendants are included,
+  // even those inside a nested top browser.
+  void CallOnAllTopDescendants(
+      const FunctionRef<CallState(CanonicalBrowsingContext*)>& aCallback,
+      bool aIncludeNestedBrowsers);
+
+  void SessionHistoryCommit(uint64_t aLoadId, const nsID& aChangeID,
+                            uint32_t aLoadType, bool aPersist,
+                            bool aCloneEntryChildren, bool aChannelExpired,
+                            uint32_t aCacheKey);
+
+  // Calls the session history listeners' OnHistoryReload, storing the result in
+  // aCanReload. If aCanReload is set to true and we have an active or a loading
+  // entry then aLoadState will be initialized from that entry, and
+  // aReloadActiveEntry will be true if we have an active entry. If aCanReload
+  // is true and aLoadState and aReloadActiveEntry are not set then we should
+  // attempt to reload based on the current document in the docshell.
+  void NotifyOnHistoryReload(
+      bool aForceReload, bool& aCanReload,
+      Maybe<NotNull<RefPtr<nsDocShellLoadState>>>& aLoadState,
+      Maybe<bool>& aReloadActiveEntry);
+
+  // See BrowsingContext::SetActiveSessionHistoryEntry.
+  void SetActiveSessionHistoryEntry(const Maybe<nsPoint>& aPreviousScrollPos,
+                                    SessionHistoryInfo* aInfo,
+                                    uint32_t aLoadType,
+                                    uint32_t aUpdatedCacheKey,
+                                    const nsID& aChangeID);
+
+  void ReplaceActiveSessionHistoryEntry(SessionHistoryInfo* aInfo);
+
+  void RemoveDynEntriesFromActiveSessionHistoryEntry();
+
+  void RemoveFromSessionHistory(const nsID& aChangeID);
+
+  Maybe<int32_t> HistoryGo(int32_t aOffset, uint64_t aHistoryEpoch,
+                           bool aRequireUserInteraction, bool aUserActivation,
+                           Maybe<ContentParentId> aContentId);
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  // Dispatches a wheel zoom change to the embedder element.
+  void DispatchWheelZoomChange(bool aIncrease);
+
+  // This function is used to start the autoplay media which are delayed to
+  // start. If needed, it would also notify the content browsing context which
+  // are related with the canonical browsing content tree to start delayed
+  // autoplay media.
+  void NotifyStartDelayedAutoplayMedia();
+
+  // This function is used to mute or unmute all media within a tab. It would
+  // set the media mute property for the top level window and propagate it to
+  // other top level windows in other processes.
+  void NotifyMediaMutedChanged(bool aMuted, ErrorResult& aRv);
+
+  // Return the number of unique site origins by iterating all given BCs,
+  // including their subtrees.
+  static uint32_t CountSiteOrigins(
+      GlobalObject& aGlobal,
+      const Sequence<mozilla::OwningNonNull<BrowsingContext>>& aRoots);
+
+  // Return true if a private browsing session is active.
+  static bool IsPrivateBrowsingActive();
+
+  // This function would propogate the action to its all child browsing contexts
+  // in content processes.
+  void UpdateMediaControlAction(const MediaControlAction& aAction);
+
+  // Triggers a load in the process
+  using BrowsingContext::LoadURI;
+  void FixupAndLoadURIString(const nsAString& aURI,
+                             const LoadURIOptions& aOptions,
+                             ErrorResult& aError);
+  void LoadURI(nsIURI* aURI, const LoadURIOptions& aOptions,
+               ErrorResult& aError);
+
+  void GoBack(const Optional<int32_t>& aCancelContentJSEpoch,
+              bool aRequireUserInteraction, bool aUserActivation);
+  void GoForward(const Optional<int32_t>& aCancelContentJSEpoch,
+                 bool aRequireUserInteraction, bool aUserActivation);
+  void GoToIndex(int32_t aIndex, const Optional<int32_t>& aCancelContentJSEpoch,
+                 bool aUserActivation);
+  void Reload(uint32_t aReloadFlags);
+  void Stop(uint32_t aStopFlags);
+
+  // Get the publicly exposed current URI loaded in this BrowsingContext.
+  already_AddRefed<nsIURI> GetCurrentURI() const;
+  void SetCurrentRemoteURI(nsIURI* aCurrentRemoteURI);
+
+  BrowserParent* GetBrowserParent() const;
+  void SetCurrentBrowserParent(BrowserParent* aBrowserParent);
+
+  // Internal method to change which process a BrowsingContext is being loaded
+  // in. The returned promise will resolve when the process switch is completed.
+  //
+  // A NOT_REMOTE_TYPE aRemoteType argument will perform a process switch into
+  // the parent process, and the method will resolve with a null BrowserParent.
+  using RemotenessPromise = MozPromise<RefPtr<BrowserParent>, nsresult, false>;
+  RefPtr<RemotenessPromise> ChangeRemoteness(
+      const NavigationIsolationOptions& aOptions, uint64_t aPendingSwitchId);
+
+  // Return a media controller from the top-level browsing context that can
+  // control all media belonging to this browsing context tree. Return nullptr
+  // if the top-level browsing context has been discarded.
+  MediaController* GetMediaController();
+  bool HasCreatedMediaController() const;
+
+  // Attempts to start loading the given load state in this BrowsingContext,
+  // without requiring any communication from a docshell. This will handle
+  // computing the right process to load in, and organising handoff to
+  // the right docshell when we get a response.
+  bool LoadInParent(nsDocShellLoadState* aLoadState, bool aSetNavigating);
+
+  // Attempts to start loading the given load state in this BrowsingContext,
+  // in parallel with a DocumentChannelChild being created in the docshell.
+  // Requires the DocumentChannel to connect with this load for it to
+  // complete successfully.
+  bool AttemptSpeculativeLoadInParent(nsDocShellLoadState* aLoadState);
+
+  // Get or create a secure browser UI for this BrowsingContext
+  nsISecureBrowserUI* GetSecureBrowserUI();
+
+  BrowsingContextWebProgress* GetWebProgress() { return mWebProgress; }
+
+  // Called when the current URI changes (from an
+  // nsIWebProgressListener::OnLocationChange event, so that we
+  // can update our security UI for the new location, or when the
+  // mixed content/https-only state for our current window is changed.
+  void UpdateSecurityState();
+
+  void MaybeAddAsProgressListener(nsIWebProgress* aWebProgress);
+
+  // Called when a navigation forces us to recreate our browsing
+  // context (for example, when switching in or out of the parent
+  // process).
+  // aNewContext is the newly created BrowsingContext that is replacing
+  // us.
+  void ReplacedBy(CanonicalBrowsingContext* aNewContext,
+                  const NavigationIsolationOptions& aRemotenessOptions);
+
+  bool HasHistoryEntry(nsISHEntry* aEntry);
+  bool HasLoadingHistoryEntry(nsISHEntry* aEntry) {
+    for (const LoadingSessionHistoryEntry& loading : mLoadingEntries) {
+      if (loading.mEntry == aEntry) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  void SwapHistoryEntries(nsISHEntry* aOldEntry, nsISHEntry* aNewEntry);
+
+  void AddLoadingSessionHistoryEntry(uint64_t aLoadId,
+                                     SessionHistoryEntry* aEntry);
+
+  void GetLoadingSessionHistoryInfoFromParent(
+      Maybe<LoadingSessionHistoryInfo>& aLoadingInfo);
+
+  void HistoryCommitIndexAndLength();
+
+  void SynchronizeLayoutHistoryState();
+
+  void ResetScalingZoom();
+
+  void SetContainerFeaturePolicy(FeaturePolicy* aContainerFeaturePolicy);
+  FeaturePolicy* GetContainerFeaturePolicy() const {
+    return mContainerFeaturePolicy;
+  }
+
+  void SetRestoreData(SessionStoreRestoreData* aData, ErrorResult& aError);
+  void ClearRestoreState();
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void RequestRestoreTabContent(
+      WindowGlobalParent* aWindow);
+  already_AddRefed<Promise> GetRestorePromise();
+
+  nsresult WriteSessionStorageToSessionStore(
+      const nsTArray<SSCacheCopy>& aSesssionStorage, uint32_t aEpoch);
+
+  void UpdateSessionStoreSessionStorage(const std::function<void()>& aDone);
+
+  static void UpdateSessionStoreForStorage(uint64_t aBrowsingContextId);
+
+  // Called when a BrowserParent for this BrowsingContext has been fully
+  // destroyed (i.e. `ActorDestroy` was called).
+  void BrowserParentDestroyed(BrowserParent* aBrowserParent,
+                              bool aAbnormalShutdown);
+
+  void StartUnloadingHost(uint64_t aChildID);
+  void ClearUnloadingHost(uint64_t aChildID);
+
+  bool AllowedInBFCache(const Maybe<uint64_t>& aChannelId, nsIURI* aNewURI);
+
+  // Methods for getting and setting the active state for top level
+  // browsing contexts, for the process priority manager.
+  bool IsPriorityActive() const {
+    MOZ_RELEASE_ASSERT(IsTop());
+    return mPriorityActive;
+  }
+  void SetPriorityActive(bool aIsActive) {
+    MOZ_RELEASE_ASSERT(IsTop());
+    mPriorityActive = aIsActive;
+  }
+
+  void SetIsActive(bool aIsActive, ErrorResult& aRv) {
+    MOZ_ASSERT(ManuallyManagesActiveness(),
+               "Shouldn't be setting active status of this browsing context if "
+               "not manually managed");
+    SetIsActiveInternal(aIsActive, aRv);
+  }
+
+  void SetIsActiveInternal(bool aIsActive, ErrorResult& aRv) {
+    SetExplicitActive(aIsActive ? ExplicitActiveStatus::Active
+                                : ExplicitActiveStatus::Inactive,
+                      aRv);
+  }
+
+  void SetTouchEventsOverride(dom::TouchEventsOverride, ErrorResult& aRv);
+  void SetTargetTopLevelLinkClicksToBlank(bool aTargetTopLevelLinkClicksToBlank,
+                                          ErrorResult& aRv);
+
+  bool IsReplaced() const { return mIsReplaced; }
+
+  const JS::Heap<JS::Value>& PermanentKey() { return mPermanentKey; }
+  void ClearPermanentKey() { mPermanentKey.setNull(); }
+  void MaybeSetPermanentKey(Element* aEmbedder);
+
+  // When request for page awake, it would increase a count that is used to
+  // prevent whole browsing context tree from being suspended. The request can
+  // be called multiple times. When calling the revoke, it would decrease the
+  // count and once the count reaches to zero, the browsing context tree could
+  // be suspended when the tree is inactive.
+  void AddPageAwakeRequest();
+  void RemovePageAwakeRequest();
+
+  void CloneDocumentTreeInto(CanonicalBrowsingContext* aSource,
+                             const nsACString& aRemoteType,
+                             embedding::PrintData&& aPrintData);
+
+  // Returns a Promise which resolves when cloning documents for printing
+  // finished if this browsing context is cloning document tree.
+  RefPtr<GenericNonExclusivePromise> GetClonePromise() const {
+    return mClonePromise;
+  }
+
+  bool StartApzAutoscroll(float aAnchorX, float aAnchorY, nsViewID aScrollId,
+                          uint32_t aPresShellId);
+  void StopApzAutoscroll(nsViewID aScrollId, uint32_t aPresShellId);
+
+  void AddFinalDiscardListener(std::function<void(uint64_t)>&& aListener);
+
+  bool ForceAppWindowActive() const { return mForceAppWindowActive; }
+  void SetForceAppWindowActive(bool, ErrorResult&);
+  void RecomputeAppWindowVisibility();
+
+  already_AddRefed<nsISHEntry> GetMostRecentLoadingSessionHistoryEntry();
+
+  already_AddRefed<BounceTrackingState> GetBounceTrackingState();
+
+ protected:
+  // Called when the browsing context is being discarded.
+  void CanonicalDiscard();
+
+  // Called when the browsing context is being attached.
+  void CanonicalAttach();
+
+  // Called when the browsing context private mode is changed after
+  // being attached, but before being discarded.
+  void AdjustPrivateBrowsingCount(bool aPrivateBrowsing);
+
+  using Type = BrowsingContext::Type;
+  CanonicalBrowsingContext(WindowContext* aParentWindow,
+                           BrowsingContextGroup* aGroup,
+                           uint64_t aBrowsingContextId,
+                           uint64_t aOwnerProcessId,
+                           uint64_t aEmbedderProcessId, Type aType,
+                           FieldValues&& aInit);
+
+ private:
+  friend class BrowsingContext;
+
+  virtual ~CanonicalBrowsingContext();
+
+  class PendingRemotenessChange {
+   public:
+    NS_INLINE_DECL_REFCOUNTING(PendingRemotenessChange)
+
+    PendingRemotenessChange(CanonicalBrowsingContext* aTarget,
+                            RemotenessPromise::Private* aPromise,
+                            uint64_t aPendingSwitchId,
+                            const NavigationIsolationOptions& aOptions);
+
+    void Cancel(nsresult aRv);
+
+   private:
+    friend class CanonicalBrowsingContext;
+
+    ~PendingRemotenessChange();
+    void ProcessLaunched();
+    void ProcessReady();
+    void MaybeFinish();
+    void Clear();
+
+    nsresult FinishTopContent();
+    nsresult FinishSubframe();
+
+    RefPtr<CanonicalBrowsingContext> mTarget;
+    RefPtr<RemotenessPromise::Private> mPromise;
+    RefPtr<ContentParent> mContentParent;
+    RefPtr<BrowsingContextGroup> mSpecificGroup;
+
+    bool mProcessReady = false;
+    bool mWaitingForPrepareToChange = false;
+
+    uint64_t mPendingSwitchId;
+    NavigationIsolationOptions mOptions;
+  };
+
+  struct RestoreState {
+    NS_INLINE_DECL_REFCOUNTING(RestoreState)
+
+    void ClearData() { mData = nullptr; }
+    void Resolve();
+
+    RefPtr<SessionStoreRestoreData> mData;
+    RefPtr<Promise> mPromise;
+    uint32_t mRequests = 0;
+    uint32_t mResolves = 0;
+
+   private:
+    ~RestoreState() = default;
+  };
+
+  friend class net::DocumentLoadListener;
+  // Called when a DocumentLoadListener is created to start a load for
+  // this browsing context. Returns false if a higher priority load is
+  // already in-progress and the new one has been rejected.
+  bool StartDocumentLoad(net::DocumentLoadListener* aLoad);
+  // Called once DocumentLoadListener completes handling a load, and it
+  // is either complete, or handed off to the final channel to deliver
+  // data to the destination docshell.
+  // If aContinueNavigating it set, the reference to the DocumentLoadListener
+  // will be cleared to prevent it being cancelled, however the current load ID
+  // will be preserved until `EndDocumentLoad` is called again.
+  void EndDocumentLoad(bool aContinueNavigating);
+
+  bool SupportsLoadingInParent(nsDocShellLoadState* aLoadState,
+                               uint64_t* aOuterWindowId);
+
+  void HistoryCommitIndexAndLength(
+      const nsID& aChangeID,
+      const CallerWillNotifyHistoryIndexAndLengthChanges& aProofOfCaller);
+
+  struct UnloadingHost {
+    uint64_t mChildID;
+    nsTArray<std::function<void()>> mCallbacks;
+  };
+  nsTArray<UnloadingHost>::iterator FindUnloadingHost(uint64_t aChildID);
+
+  // Called when we want to show the subframe crashed UI as our previous browser
+  // has become unloaded for one reason or another.
+  void ShowSubframeCrashedUI(BrowserBridgeParent* aBridge);
+
+  void MaybeScheduleSessionStoreUpdate();
+
+  void CancelSessionStoreUpdate();
+
+  void AddPendingDiscard();
+
+  void RemovePendingDiscard();
+
+  bool ShouldAddEntryForRefresh(const SessionHistoryEntry* aEntry) {
+    return ShouldAddEntryForRefresh(aEntry->Info().GetURI(),
+                                    aEntry->Info().HasPostData());
+  }
+  bool ShouldAddEntryForRefresh(nsIURI* aNewURI, bool aHasPostData) {
+    nsCOMPtr<nsIURI> currentURI = GetCurrentURI();
+    return BrowsingContext::ShouldAddEntryForRefresh(currentURI, aNewURI,
+                                                     aHasPostData);
+  }
+
+  already_AddRefed<nsDocShellLoadState> CreateLoadInfo(
+      SessionHistoryEntry* aEntry);
+
+  // XXX(farre): Store a ContentParent pointer here rather than mProcessId?
+  // Indicates which process owns the docshell.
+  uint64_t mProcessId;
+
+  // Indicates which process owns the embedder element.
+  uint64_t mEmbedderProcessId;
+
+  uint64_t mCrossGroupOpenerId = 0;
+
+  // This function will make the top window context reset its
+  // "SHEntryHasUserInteraction" cache that prevents documents from repeatedly
+  // setting user interaction on SH entries. Should be called anytime SH
+  // entries are added or replaced.
+  void ResetSHEntryHasUserInteractionCache();
+
+  RefPtr<BrowserParent> mCurrentBrowserParent;
+
+  nsTArray<UnloadingHost> mUnloadingHosts;
+
+  // The current URI loaded in this BrowsingContext. This value is only set for
+  // BrowsingContexts loaded in content processes.
+  nsCOMPtr<nsIURI> mCurrentRemoteURI;
+
+  // The current remoteness change which is in a pending state.
+  RefPtr<PendingRemotenessChange> mPendingRemotenessChange;
+
+  RefPtr<nsSHistory> mSessionHistory;
+
+  // Tab media controller is used to control all media existing in the same
+  // browsing context tree, so it would only exist in the top level browsing
+  // context.
+  RefPtr<MediaController> mTabMediaController;
+
+  RefPtr<net::DocumentLoadListener> mCurrentLoad;
+
+  struct LoadingSessionHistoryEntry {
+    uint64_t mLoadId = 0;
+    RefPtr<SessionHistoryEntry> mEntry;
+  };
+  nsTArray<LoadingSessionHistoryEntry> mLoadingEntries;
+  RefPtr<SessionHistoryEntry> mActiveEntry;
+
+  RefPtr<nsSecureBrowserUI> mSecureBrowserUI;
+  RefPtr<BrowsingContextWebProgress> mWebProgress;
+
+  nsCOMPtr<nsIWebProgressListener> mDocShellProgressBridge;
+  RefPtr<nsBrowserStatusFilter> mStatusFilter;
+
+  RefPtr<FeaturePolicy> mContainerFeaturePolicy;
+
+  friend class BrowserSessionStore;
+  WeakPtr<SessionStoreFormData>& GetSessionStoreFormDataRef() {
+    return mFormdata;
+  }
+  WeakPtr<SessionStoreScrollData>& GetSessionStoreScrollDataRef() {
+    return mScroll;
+  }
+
+  WeakPtr<SessionStoreFormData> mFormdata;
+  WeakPtr<SessionStoreScrollData> mScroll;
+
+  RefPtr<RestoreState> mRestoreState;
+
+  nsCOMPtr<nsITimer> mSessionStoreSessionStorageUpdateTimer;
+
+  // If this is a top level context, this is true if our browser ID is marked as
+  // active in the process priority manager.
+  bool mPriorityActive = false;
+
+  // See CanonicalBrowsingContext.forceAppWindowActive.
+  bool mForceAppWindowActive = false;
+
+  bool mIsReplaced = false;
+
+  // A Promise created when cloning documents for printing.
+  RefPtr<GenericNonExclusivePromise> mClonePromise;
+
+  JS::Heap<JS::Value> mPermanentKey;
+
+  uint32_t mPendingDiscards = 0;
+
+  bool mFullyDiscarded = false;
+
+  nsTArray<std::function<void(uint64_t)>> mFullyDiscardedListeners;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // !defined(mozilla_dom_CanonicalBrowsingContext_h)
diff --git a/docshell/base/ChildProcessChannelListener.cpp b/docshell/base/ChildProcessChannelListener.cpp
new file mode 100644
index 0000000000..628d75abb1
--- /dev/null
+++ b/docshell/base/ChildProcessChannelListener.cpp
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/ChildProcessChannelListener.h"
+
+#include "mozilla/ipc/Endpoint.h"
+#include "nsDocShellLoadState.h"
+
+namespace mozilla {
+namespace dom {
+
+static StaticRefPtr<ChildProcessChannelListener> sCPCLSingleton;
+
+void ChildProcessChannelListener::RegisterCallback(uint64_t aIdentifier,
+                                                   Callback&& aCallback) {
+  if (auto args = mChannelArgs.Extract(aIdentifier)) {
+    nsresult rv =
+        aCallback(args->mLoadState, std::move(args->mStreamFilterEndpoints),
+                  args->mTiming);
+    args->mResolver(rv);
+  } else {
+    mCallbacks.InsertOrUpdate(aIdentifier, std::move(aCallback));
+  }
+}
+
+void ChildProcessChannelListener::OnChannelReady(
+    nsDocShellLoadState* aLoadState, uint64_t aIdentifier,
+    nsTArray<Endpoint>&& aStreamFilterEndpoints, nsDOMNavigationTiming* aTiming,
+    Resolver&& aResolver) {
+  if (auto callback = mCallbacks.Extract(aIdentifier)) {
+    nsresult rv =
+        (*callback)(aLoadState, std::move(aStreamFilterEndpoints), aTiming);
+    aResolver(rv);
+  } else {
+    mChannelArgs.InsertOrUpdate(
+        aIdentifier, CallbackArgs{aLoadState, std::move(aStreamFilterEndpoints),
+                                  aTiming, std::move(aResolver)});
+  }
+}
+
+ChildProcessChannelListener::~ChildProcessChannelListener() {
+  for (const auto& args : mChannelArgs.Values()) {
+    args.mResolver(NS_ERROR_FAILURE);
+  }
+}
+
+already_AddRefed<ChildProcessChannelListener>
+ChildProcessChannelListener::GetSingleton() {
+  if (!sCPCLSingleton) {
+    sCPCLSingleton = new ChildProcessChannelListener();
+    ClearOnShutdown(&sCPCLSingleton);
+  }
+  RefPtr<ChildProcessChannelListener> cpcl = sCPCLSingleton;
+  return cpcl.forget();
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/docshell/base/ChildProcessChannelListener.h b/docshell/base/ChildProcessChannelListener.h
new file mode 100644
index 0000000000..c00c2ff5a7
--- /dev/null
+++ b/docshell/base/ChildProcessChannelListener.h
@@ -0,0 +1,54 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_ChildProcessChannelListener_h
+#define mozilla_dom_ChildProcessChannelListener_h
+
+#include <functional>
+
+#include "mozilla/extensions/StreamFilterParent.h"
+#include "mozilla/net/NeckoChannelParams.h"
+#include "nsDOMNavigationTiming.h"
+#include "nsTHashMap.h"
+#include "nsIChannel.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+
+namespace mozilla::dom {
+
+class ChildProcessChannelListener final {
+  NS_INLINE_DECL_REFCOUNTING(ChildProcessChannelListener)
+
+  using Endpoint = mozilla::ipc::Endpoint<extensions::PStreamFilterParent>;
+  using Resolver = std::function<void(const nsresult&)>;
+  using Callback = std::function<nsresult(
+      nsDocShellLoadState*, nsTArray<Endpoint>&&, nsDOMNavigationTiming*)>;
+
+  void RegisterCallback(uint64_t aIdentifier, Callback&& aCallback);
+
+  void OnChannelReady(nsDocShellLoadState* aLoadState, uint64_t aIdentifier,
+                      nsTArray<Endpoint>&& aStreamFilterEndpoints,
+                      nsDOMNavigationTiming* aTiming, Resolver&& aResolver);
+
+  static already_AddRefed<ChildProcessChannelListener> GetSingleton();
+
+ private:
+  ChildProcessChannelListener() = default;
+  ~ChildProcessChannelListener();
+  struct CallbackArgs {
+    RefPtr<nsDocShellLoadState> mLoadState;
+    nsTArray<Endpoint> mStreamFilterEndpoints;
+    RefPtr<nsDOMNavigationTiming> mTiming;
+    Resolver mResolver;
+  };
+
+  // TODO Backtrack.
+  nsTHashMap<nsUint64HashKey, Callback> mCallbacks;
+  nsTHashMap<nsUint64HashKey, CallbackArgs> mChannelArgs;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // !defined(mozilla_dom_ChildProcessChannelListener_h)
diff --git a/docshell/base/IHistory.h b/docshell/base/IHistory.h
new file mode 100644
index 0000000000..30da778f45
--- /dev/null
+++ b/docshell/base/IHistory.h
@@ -0,0 +1,175 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_IHistory_h_
+#define mozilla_IHistory_h_
+
+#include "nsISupports.h"
+#include "nsURIHashKey.h"
+#include "nsTHashSet.h"
+#include "nsTObserverArray.h"
+
+class nsIURI;
+class nsIWidget;
+
+namespace mozilla {
+
+namespace dom {
+class ContentParent;
+class Document;
+class Link;
+}  // namespace dom
+
+// 0057c9d3-b98e-4933-bdc5-0275d06705e1
+#define IHISTORY_IID                                 \
+  {                                                  \
+    0x0057c9d3, 0xb98e, 0x4933, {                    \
+      0xbd, 0xc5, 0x02, 0x75, 0xd0, 0x67, 0x05, 0xe1 \
+    }                                                \
+  }
+
+class IHistory : public nsISupports {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(IHISTORY_IID)
+
+  using ContentParentSet = nsTHashSet<RefPtr<dom::ContentParent>>;
+
+  /**
+   * Registers the Link for notifications about the visited-ness of aURI.
+   * Consumers should assume that the URI is unvisited after calling this, and
+   * they will be notified if that state (unvisited) changes by having
+   * VisitedQueryFinished called on themselves. Note that it may call
+   * synchronously if the answer is already known.
+   *
+   * @note VisitedQueryFinished must not call RegisterVisitedCallback or
+   *       UnregisterVisitedCallback.
+   *
+   * @pre aURI must not be null.
+   * @pre aLink may be null only in the parent (chrome) process.
+   *
+   * @param aURI
+   *        The URI to check.
+   * @param aLink
+   *        The link to update whenever the history status changes.  The
+   *        implementation will only hold onto a raw pointer, so if this
+   *        object should be destroyed, be sure to call
+   *        UnregisterVistedCallback first.
+   */
+  virtual void RegisterVisitedCallback(nsIURI* aURI, dom::Link* aLink) = 0;
+
+  /**
+   * Schedules a single visited query from a given child process.
+   *
+   * @param aURI the URI to query.
+   * @param ContentParent the process interested in knowing about the visited
+   *                      state of this URI.
+   */
+  virtual void ScheduleVisitedQuery(nsIURI* aURI, dom::ContentParent*) = 0;
+
+  /**
+   * Unregisters a previously registered Link object.  This must be called
+   * before destroying the registered object, and asserts when misused.
+   *
+   * @pre aURI must not be null.
+   * @pre aLink must not be null.
+   *
+   * @param aURI
+   *        The URI that aLink was registered for.
+   * @param aLink
+   *        The link object to unregister for aURI.
+   */
+  virtual void UnregisterVisitedCallback(nsIURI* aURI, dom::Link* aLink) = 0;
+
+  enum class VisitedStatus : uint8_t {
+    Unknown,
+    Visited,
+    Unvisited,
+  };
+
+  /**
+   * Notifies about the visited status of a given URI. The visited status cannot
+   * be unknown, otherwise there's no point in notifying of anything.
+   *
+   * @param ContentParentSet a set of content processes that are interested on
+   *                         this change. If null, it is broadcasted to all
+   *                         child processes.
+   */
+  virtual void NotifyVisited(nsIURI*, VisitedStatus,
+                             const ContentParentSet* = nullptr) = 0;
+
+  enum VisitFlags {
+    /**
+     * Indicates whether the URI was loaded in a top-level window.
+     */
+    TOP_LEVEL = 1 << 0,
+    /**
+     * Indicates whether the URI is the target of a permanent redirect.
+     */
+    REDIRECT_PERMANENT = 1 << 1,
+    /**
+     * Indicates whether the URI is the target of a temporary redirect.
+     */
+    REDIRECT_TEMPORARY = 1 << 2,
+    /**
+     * Indicates the URI will redirect  (Response code 3xx).
+     */
+    REDIRECT_SOURCE = 1 << 3,
+    /**
+     * Indicates the URI caused an error that is unlikely fixable by a
+     * retry, like a not found or unfetchable page.
+     */
+    UNRECOVERABLE_ERROR = 1 << 4,
+    /**
+     * If REDIRECT_SOURCE is set, this indicates that the redirect is permanent.
+     * Note this differs from REDIRECT_PERMANENT because that one refers to how
+     * we reached the URI, while this is used when the URI itself redirects.
+     */
+    REDIRECT_SOURCE_PERMANENT = 1 << 5,
+    /**
+     * If REDIRECT_SOURCE is set, this indicates that this is a special redirect
+     * caused by HSTS or HTTPS-Only/First upgrading to the HTTPS version of the
+     * URI.
+     */
+    REDIRECT_SOURCE_UPGRADED = 1 << 6
+  };
+
+  /**
+   * Adds a history visit for the URI.
+   *
+   * @pre aURI must not be null.
+   *
+   * @param aWidget
+   *        The widget for the DocShell.
+   * @param aURI
+   *        The URI of the page being visited.
+   * @param aLastVisitedURI
+   *        The URI of the last visit in the chain.
+   * @param aFlags
+   *        The VisitFlags describing this visit.
+   * @param aBrowserId
+   *        The id of browser used for this visit.
+   */
+  NS_IMETHOD VisitURI(nsIWidget* aWidget, nsIURI* aURI, nsIURI* aLastVisitedURI,
+                      uint32_t aFlags, uint64_t aBrowserId) = 0;
+
+  /**
+   * Set the title of the URI.
+   *
+   * @pre aURI must not be null.
+   *
+   * @param aURI
+   *        The URI to set the title for.
+   * @param aTitle
+   *        The title string.
+   */
+  NS_IMETHOD SetURITitle(nsIURI* aURI, const nsAString& aTitle) = 0;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(IHistory, IHISTORY_IID)
+
+}  // namespace mozilla
+
+#endif  // mozilla_IHistory_h_
diff --git a/docshell/base/LoadContext.cpp b/docshell/base/LoadContext.cpp
new file mode 100644
index 0000000000..2e501be221
--- /dev/null
+++ b/docshell/base/LoadContext.cpp
@@ -0,0 +1,236 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Assertions.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/LoadContext.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/ScriptSettings.h"  // for AutoJSAPI
+#include "mozilla/dom/BrowsingContext.h"
+#include "nsContentUtils.h"
+#include "xpcpublic.h"
+
+namespace mozilla {
+
+NS_IMPL_ISUPPORTS(LoadContext, nsILoadContext, nsIInterfaceRequestor)
+
+LoadContext::LoadContext(const IPC::SerializedLoadContext& aToCopy,
+                         dom::Element* aTopFrameElement,
+                         OriginAttributes& aAttrs)
+    : mTopFrameElement(do_GetWeakReference(aTopFrameElement)),
+      mIsContent(aToCopy.mIsContent),
+      mUseRemoteTabs(aToCopy.mUseRemoteTabs),
+      mUseRemoteSubframes(aToCopy.mUseRemoteSubframes),
+      mUseTrackingProtection(aToCopy.mUseTrackingProtection),
+#ifdef DEBUG
+      mIsNotNull(aToCopy.mIsNotNull),
+#endif
+      mOriginAttributes(aAttrs) {
+}
+
+LoadContext::LoadContext(OriginAttributes& aAttrs)
+    : mTopFrameElement(nullptr),
+      mIsContent(false),
+      mUseRemoteTabs(false),
+      mUseRemoteSubframes(false),
+      mUseTrackingProtection(false),
+#ifdef DEBUG
+      mIsNotNull(true),
+#endif
+      mOriginAttributes(aAttrs) {
+}
+
+LoadContext::LoadContext(nsIPrincipal* aPrincipal,
+                         nsILoadContext* aOptionalBase)
+    : mTopFrameElement(nullptr),
+      mIsContent(true),
+      mUseRemoteTabs(false),
+      mUseRemoteSubframes(false),
+      mUseTrackingProtection(false),
+#ifdef DEBUG
+      mIsNotNull(true),
+#endif
+      mOriginAttributes(aPrincipal->OriginAttributesRef()) {
+  if (!aOptionalBase) {
+    return;
+  }
+
+  MOZ_ALWAYS_SUCCEEDS(aOptionalBase->GetIsContent(&mIsContent));
+  MOZ_ALWAYS_SUCCEEDS(aOptionalBase->GetUseRemoteTabs(&mUseRemoteTabs));
+  MOZ_ALWAYS_SUCCEEDS(
+      aOptionalBase->GetUseRemoteSubframes(&mUseRemoteSubframes));
+  MOZ_ALWAYS_SUCCEEDS(
+      aOptionalBase->GetUseTrackingProtection(&mUseTrackingProtection));
+}
+
+LoadContext::~LoadContext() = default;
+
+//-----------------------------------------------------------------------------
+// LoadContext::nsILoadContext
+//-----------------------------------------------------------------------------
+
+NS_IMETHODIMP
+LoadContext::GetAssociatedWindow(mozIDOMWindowProxy**) {
+  MOZ_ASSERT(mIsNotNull);
+
+  // can't support this in the parent process
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+LoadContext::GetTopWindow(mozIDOMWindowProxy**) {
+  MOZ_ASSERT(mIsNotNull);
+
+  // can't support this in the parent process
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+LoadContext::GetTopFrameElement(dom::Element** aElement) {
+  nsCOMPtr<dom::Element> element = do_QueryReferent(mTopFrameElement);
+  element.forget(aElement);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadContext::GetIsContent(bool* aIsContent) {
+  MOZ_ASSERT(mIsNotNull);
+
+  NS_ENSURE_ARG_POINTER(aIsContent);
+
+  *aIsContent = mIsContent;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadContext::GetUsePrivateBrowsing(bool* aUsePrivateBrowsing) {
+  MOZ_ASSERT(mIsNotNull);
+
+  NS_ENSURE_ARG_POINTER(aUsePrivateBrowsing);
+
+  *aUsePrivateBrowsing = mOriginAttributes.mPrivateBrowsingId > 0;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadContext::SetUsePrivateBrowsing(bool aUsePrivateBrowsing) {
+  MOZ_ASSERT(mIsNotNull);
+
+  // We shouldn't need this on parent...
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+LoadContext::SetPrivateBrowsing(bool aUsePrivateBrowsing) {
+  MOZ_ASSERT(mIsNotNull);
+
+  // We shouldn't need this on parent...
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+LoadContext::GetUseRemoteTabs(bool* aUseRemoteTabs) {
+  MOZ_ASSERT(mIsNotNull);
+
+  NS_ENSURE_ARG_POINTER(aUseRemoteTabs);
+
+  *aUseRemoteTabs = mUseRemoteTabs;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadContext::SetRemoteTabs(bool aUseRemoteTabs) {
+  MOZ_ASSERT(mIsNotNull);
+
+  // We shouldn't need this on parent...
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+LoadContext::GetUseRemoteSubframes(bool* aUseRemoteSubframes) {
+  MOZ_ASSERT(mIsNotNull);
+
+  NS_ENSURE_ARG_POINTER(aUseRemoteSubframes);
+
+  *aUseRemoteSubframes = mUseRemoteSubframes;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadContext::SetRemoteSubframes(bool aUseRemoteSubframes) {
+  MOZ_ASSERT(mIsNotNull);
+
+  // We shouldn't need this on parent...
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+LoadContext::GetScriptableOriginAttributes(
+    JSContext* aCx, JS::MutableHandle<JS::Value> aAttrs) {
+  bool ok = ToJSValue(aCx, mOriginAttributes, aAttrs);
+  NS_ENSURE_TRUE(ok, NS_ERROR_FAILURE);
+  return NS_OK;
+}
+
+NS_IMETHODIMP_(void)
+LoadContext::GetOriginAttributes(mozilla::OriginAttributes& aAttrs) {
+  aAttrs = mOriginAttributes;
+}
+
+NS_IMETHODIMP
+LoadContext::GetUseTrackingProtection(bool* aUseTrackingProtection) {
+  MOZ_ASSERT(mIsNotNull);
+
+  NS_ENSURE_ARG_POINTER(aUseTrackingProtection);
+
+  *aUseTrackingProtection = mUseTrackingProtection;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+LoadContext::SetUseTrackingProtection(bool aUseTrackingProtection) {
+  MOZ_ASSERT_UNREACHABLE("Should only be set through nsDocShell");
+
+  return NS_ERROR_UNEXPECTED;
+}
+
+//-----------------------------------------------------------------------------
+// LoadContext::nsIInterfaceRequestor
+//-----------------------------------------------------------------------------
+NS_IMETHODIMP
+LoadContext::GetInterface(const nsIID& aIID, void** aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+  *aResult = nullptr;
+
+  if (aIID.Equals(NS_GET_IID(nsILoadContext))) {
+    *aResult = static_cast<nsILoadContext*>(this);
+    NS_ADDREF_THIS();
+    return NS_OK;
+  }
+
+  return NS_NOINTERFACE;
+}
+
+static already_AddRefed<nsILoadContext> CreateInstance(bool aPrivate) {
+  OriginAttributes oa;
+  oa.mPrivateBrowsingId = aPrivate ? 1 : 0;
+
+  nsCOMPtr<nsILoadContext> lc = new LoadContext(oa);
+
+  return lc.forget();
+}
+
+already_AddRefed<nsILoadContext> CreateLoadContext() {
+  return CreateInstance(false);
+}
+
+already_AddRefed<nsILoadContext> CreatePrivateLoadContext() {
+  return CreateInstance(true);
+}
+
+}  // namespace mozilla
diff --git a/docshell/base/LoadContext.h b/docshell/base/LoadContext.h
new file mode 100644
index 0000000000..5cb71ff347
--- /dev/null
+++ b/docshell/base/LoadContext.h
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef LoadContext_h
+#define LoadContext_h
+
+#include "SerializedLoadContext.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BasePrincipal.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsILoadContext.h"
+
+namespace mozilla::dom {
+class Element;
+}
+
+namespace mozilla {
+
+/**
+ * Class that provides nsILoadContext info in Parent process.  Typically copied
+ * from Child via SerializedLoadContext.
+ *
+ * Note: this is not the "normal" or "original" nsILoadContext.  That is
+ * typically provided by BrowsingContext.  This is only used when the original
+ * docshell is in a different process and we need to copy certain values from
+ * it.
+ */
+
+class LoadContext final : public nsILoadContext, public nsIInterfaceRequestor {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSILOADCONTEXT
+  NS_DECL_NSIINTERFACEREQUESTOR
+
+  LoadContext(const IPC::SerializedLoadContext& aToCopy,
+              dom::Element* aTopFrameElement, OriginAttributes& aAttrs);
+
+  // Constructor taking reserved origin attributes.
+  explicit LoadContext(OriginAttributes& aAttrs);
+
+  // Constructor for creating a LoadContext with a given browser flag.
+  explicit LoadContext(nsIPrincipal* aPrincipal,
+                       nsILoadContext* aOptionalBase = nullptr);
+
+ private:
+  ~LoadContext();
+
+  nsWeakPtr mTopFrameElement;
+  bool mIsContent;
+  bool mUseRemoteTabs;
+  bool mUseRemoteSubframes;
+  bool mUseTrackingProtection;
+#ifdef DEBUG
+  bool mIsNotNull;
+#endif
+  OriginAttributes mOriginAttributes;
+};
+
+already_AddRefed<nsILoadContext> CreateLoadContext();
+already_AddRefed<nsILoadContext> CreatePrivateLoadContext();
+
+}  // namespace mozilla
+
+#endif  // LoadContext_h
diff --git a/docshell/base/SerializedLoadContext.cpp b/docshell/base/SerializedLoadContext.cpp
new file mode 100644
index 0000000000..cb598b43fe
--- /dev/null
+++ b/docshell/base/SerializedLoadContext.cpp
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SerializedLoadContext.h"
+#include "nsNetUtil.h"
+#include "nsIChannel.h"
+#include "nsILoadContext.h"
+#include "nsIPrivateBrowsingChannel.h"
+#include "nsIWebSocketChannel.h"
+
+namespace IPC {
+
+SerializedLoadContext::SerializedLoadContext(nsILoadContext* aLoadContext)
+    : mIsContent(false),
+      mUseRemoteTabs(false),
+      mUseRemoteSubframes(false),
+      mUseTrackingProtection(false) {
+  Init(aLoadContext);
+}
+
+SerializedLoadContext::SerializedLoadContext(nsIChannel* aChannel)
+    : mIsContent(false),
+      mUseRemoteTabs(false),
+      mUseRemoteSubframes(false),
+      mUseTrackingProtection(false) {
+  if (!aChannel) {
+    Init(nullptr);
+    return;
+  }
+
+  nsCOMPtr<nsILoadContext> loadContext;
+  NS_QueryNotificationCallbacks(aChannel, loadContext);
+  Init(loadContext);
+
+  if (!loadContext) {
+    // Attempt to retrieve the private bit from the channel if it has been
+    // overriden.
+    bool isPrivate = false;
+    bool isOverriden = false;
+    nsCOMPtr<nsIPrivateBrowsingChannel> pbChannel = do_QueryInterface(aChannel);
+    if (pbChannel &&
+        NS_SUCCEEDED(
+            pbChannel->IsPrivateModeOverriden(&isPrivate, &isOverriden)) &&
+        isOverriden) {
+      mIsPrivateBitValid = true;
+    }
+    mOriginAttributes.SyncAttributesWithPrivateBrowsing(isPrivate);
+  }
+}
+
+SerializedLoadContext::SerializedLoadContext(nsIWebSocketChannel* aChannel)
+    : mIsContent(false),
+      mUseRemoteTabs(false),
+      mUseRemoteSubframes(false),
+      mUseTrackingProtection(false) {
+  nsCOMPtr<nsILoadContext> loadContext;
+  if (aChannel) {
+    NS_QueryNotificationCallbacks(aChannel, loadContext);
+  }
+  Init(loadContext);
+}
+
+void SerializedLoadContext::Init(nsILoadContext* aLoadContext) {
+  if (aLoadContext) {
+    mIsNotNull = true;
+    mIsPrivateBitValid = true;
+    aLoadContext->GetIsContent(&mIsContent);
+    aLoadContext->GetUseRemoteTabs(&mUseRemoteTabs);
+    aLoadContext->GetUseRemoteSubframes(&mUseRemoteSubframes);
+    aLoadContext->GetUseTrackingProtection(&mUseTrackingProtection);
+    aLoadContext->GetOriginAttributes(mOriginAttributes);
+  } else {
+    mIsNotNull = false;
+    mIsPrivateBitValid = false;
+    // none of below values really matter when mIsNotNull == false:
+    // we won't be GetInterfaced to nsILoadContext
+    mIsContent = true;
+    mUseRemoteTabs = false;
+    mUseRemoteSubframes = false;
+    mUseTrackingProtection = false;
+  }
+}
+
+}  // namespace IPC
diff --git a/docshell/base/SerializedLoadContext.h b/docshell/base/SerializedLoadContext.h
new file mode 100644
index 0000000000..d47ad08003
--- /dev/null
+++ b/docshell/base/SerializedLoadContext.h
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef SerializedLoadContext_h
+#define SerializedLoadContext_h
+
+#include "base/basictypes.h"
+#include "ipc/IPCMessageUtils.h"
+#include "ipc/IPCMessageUtilsSpecializations.h"
+#include "mozilla/BasePrincipal.h"
+
+class nsILoadContext;
+
+/*
+ *  This file contains the IPC::SerializedLoadContext class, which is used to
+ *  copy data across IPDL from Child process contexts so it is available in the
+ *  Parent.
+ */
+
+class nsIChannel;
+class nsIWebSocketChannel;
+
+namespace IPC {
+
+class SerializedLoadContext {
+ public:
+  SerializedLoadContext()
+      : mIsNotNull(false),
+        mIsPrivateBitValid(false),
+        mIsContent(false),
+        mUseRemoteTabs(false),
+        mUseRemoteSubframes(false),
+        mUseTrackingProtection(false) {
+    Init(nullptr);
+  }
+
+  explicit SerializedLoadContext(nsILoadContext* aLoadContext);
+  explicit SerializedLoadContext(nsIChannel* aChannel);
+  explicit SerializedLoadContext(nsIWebSocketChannel* aChannel);
+
+  void Init(nsILoadContext* aLoadContext);
+
+  bool IsNotNull() const { return mIsNotNull; }
+  bool IsPrivateBitValid() const { return mIsPrivateBitValid; }
+
+  // used to indicate if child-side LoadContext * was null.
+  bool mIsNotNull;
+  // used to indicate if child-side mUsePrivateBrowsing flag is valid, even if
+  // mIsNotNull is false, i.e., child LoadContext was null.
+  bool mIsPrivateBitValid;
+  bool mIsContent;
+  bool mUseRemoteTabs;
+  bool mUseRemoteSubframes;
+  bool mUseTrackingProtection;
+  mozilla::OriginAttributes mOriginAttributes;
+};
+
+// Function to serialize over IPDL
+template <>
+struct ParamTraits<SerializedLoadContext> {
+  typedef SerializedLoadContext paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    nsAutoCString suffix;
+    aParam.mOriginAttributes.CreateSuffix(suffix);
+
+    WriteParam(aWriter, aParam.mIsNotNull);
+    WriteParam(aWriter, aParam.mIsContent);
+    WriteParam(aWriter, aParam.mIsPrivateBitValid);
+    WriteParam(aWriter, aParam.mUseRemoteTabs);
+    WriteParam(aWriter, aParam.mUseRemoteSubframes);
+    WriteParam(aWriter, aParam.mUseTrackingProtection);
+    WriteParam(aWriter, suffix);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    nsAutoCString suffix;
+    if (!ReadParam(aReader, &aResult->mIsNotNull) ||
+        !ReadParam(aReader, &aResult->mIsContent) ||
+        !ReadParam(aReader, &aResult->mIsPrivateBitValid) ||
+        !ReadParam(aReader, &aResult->mUseRemoteTabs) ||
+        !ReadParam(aReader, &aResult->mUseRemoteSubframes) ||
+        !ReadParam(aReader, &aResult->mUseTrackingProtection) ||
+        !ReadParam(aReader, &suffix)) {
+      return false;
+    }
+    return aResult->mOriginAttributes.PopulateFromSuffix(suffix);
+  }
+};
+
+}  // namespace IPC
+
+#endif  // SerializedLoadContext_h
diff --git a/docshell/base/SyncedContext.h b/docshell/base/SyncedContext.h
new file mode 100644
index 0000000000..679e07edc2
--- /dev/null
+++ b/docshell/base/SyncedContext.h
@@ -0,0 +1,402 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_SyncedContext_h
+#define mozilla_dom_SyncedContext_h
+
+#include <array>
+#include <type_traits>
+#include <utility>
+#include "mozilla/Attributes.h"
+#include "mozilla/BitSet.h"
+#include "mozilla/EnumSet.h"
+#include "nsStringFwd.h"
+#include "nscore.h"
+
+// Referenced via macro definitions
+#include "mozilla/ErrorResult.h"
+
+class PickleIterator;
+
+namespace IPC {
+class Message;
+class MessageReader;
+class MessageWriter;
+}  // namespace IPC
+
+namespace mozilla {
+namespace ipc {
+class IProtocol;
+class IPCResult;
+template <typename T>
+struct IPDLParamTraits;
+}  // namespace ipc
+
+namespace dom {
+class ContentParent;
+class ContentChild;
+template <typename T>
+class MaybeDiscarded;
+
+namespace syncedcontext {
+
+template <size_t I>
+using Index = typename std::integral_constant<size_t, I>;
+
+// We're going to use the empty base optimization for synced fields of different
+// sizes, so we define an empty class for that purpose.
+template <size_t I, size_t S>
+struct Empty {};
+
+// A templated container for a synced field. I is the index and T is the type.
+template <size_t I, typename T>
+struct Field {
+  T mField{};
+};
+
+// SizedField is a Field with a helper to define either an "empty" field, or a
+// field of a given type.
+template <size_t I, typename T, size_t S>
+using SizedField = std::conditional_t<((sizeof(T) > 8) ? 8 : sizeof(T)) == S,
+                                      Field<I, T>, Empty<I, S>>;
+
+template <typename Context>
+class Transaction {
+ public:
+  using IndexSet = EnumSet<size_t, BitSet<Context::FieldValues::count>>;
+
+  // Set a field at the given index in this `Transaction`. Creating a
+  // `Transaction` object and setting multiple fields on it allows for
+  // multiple mutations to be performed atomically.
+  template <size_t I, typename U>
+  void Set(U&& aValue) {
+    mValues.Get(Index<I>{}) = std::forward<U>(aValue);
+    mModified += I;
+  }
+
+  // Apply the changes from this transaction to the specified Context in all
+  // processes. This method will call the correct `CanSet` and `DidSet` methods,
+  // as well as move the value.
+  //
+  // If the target has been discarded, changes will be ignored.
+  //
+  // NOTE: This method mutates `this`, clearing the modified field set.
+  [[nodiscard]] nsresult Commit(Context* aOwner);
+
+  // Called from `ContentParent` in response to a transaction from content.
+  mozilla::ipc::IPCResult CommitFromIPC(const MaybeDiscarded<Context>& aOwner,
+                                        ContentParent* aSource);
+
+  // Called from `ContentChild` in response to a transaction from the parent.
+  mozilla::ipc::IPCResult CommitFromIPC(const MaybeDiscarded<Context>& aOwner,
+                                        uint64_t aEpoch, ContentChild* aSource);
+
+  // Apply the changes from this transaction to the specified Context WITHOUT
+  // syncing the changes to other processes.
+  //
+  // Unlike `Commit`, this method will NOT call the corresponding `CanSet` or
+  // `DidSet` methods, and can be performed when the target context is
+  // unattached or discarded.
+  //
+  // NOTE: YOU PROBABLY DO NOT WANT TO USE THIS METHOD
+  void CommitWithoutSyncing(Context* aOwner);
+
+ private:
+  friend struct mozilla::ipc::IPDLParamTraits<Transaction<Context>>;
+
+  void Write(IPC::MessageWriter* aWriter,
+             mozilla::ipc::IProtocol* aActor) const;
+  bool Read(IPC::MessageReader* aReader, mozilla::ipc::IProtocol* aActor);
+
+  // You probably don't want to directly call this method - instead call
+  // `Commit`, which will perform the necessary synchronization.
+  //
+  // `Validate` must be called before calling this method.
+  void Apply(Context* aOwner, bool aFromIPC);
+
+  // Returns the set of fields which failed to validate, or an empty set if
+  // there were no validation errors.
+  //
+  // NOTE: This method mutates `this` if any changes were reverted.
+  IndexSet Validate(Context* aOwner, ContentParent* aSource);
+
+  template <typename F>
+  static void EachIndex(F&& aCallback) {
+    Context::FieldValues::EachIndex(aCallback);
+  }
+
+  template <size_t I>
+  static uint64_t& FieldEpoch(Index<I>, Context* aContext) {
+    return std::get<I>(aContext->mFields.mEpochs);
+  }
+
+  typename Context::FieldValues mValues;
+  IndexSet mModified;
+};
+
+template <typename Base, size_t Count>
+class FieldValues : public Base {
+ public:
+  // The number of fields stored by this type.
+  static constexpr size_t count = Count;
+
+  // The base type will define a series of `Get` methods for looking up a field
+  // by its field index.
+  using Base::Get;
+
+  // Calls a generic lambda with an `Index<I>` for each index less than the
+  // field count.
+  template <typename F>
+  static void EachIndex(F&& aCallback) {
+    EachIndexInner(std::make_index_sequence<count>(),
+                   std::forward<F>(aCallback));
+  }
+
+ private:
+  friend struct mozilla::ipc::IPDLParamTraits<FieldValues<Base, Count>>;
+
+  void Write(IPC::MessageWriter* aWriter,
+             mozilla::ipc::IProtocol* aActor) const;
+  bool Read(IPC::MessageReader* aReader, mozilla::ipc::IProtocol* aActor);
+
+  template <typename F, size_t... Indexes>
+  static void EachIndexInner(std::index_sequence<Indexes...> aIndexes,
+                             F&& aCallback) {
+    (aCallback(Index<Indexes>()), ...);
+  }
+};
+
+// Storage related to synchronized context fields. Contains both a tuple of
+// individual field values, and epoch information for field synchronization.
+template <typename Values>
+class FieldStorage {
+ public:
+  // Unsafely grab a reference directly to the internal values structure which
+  // can be modified without telling other processes about the change.
+  //
+  // This is only sound in specific code which is already messaging other
+  // processes, and doesn't need to worry about epochs or other properties of
+  // field synchronization.
+  Values& RawValues() { return mValues; }
+  const Values& RawValues() const { return mValues; }
+
+  // Get an individual field by index.
+  template <size_t I>
+  const auto& Get() const {
+    return RawValues().Get(Index<I>{});
+  }
+
+  // Set the value of a field without telling other processes about the change.
+  //
+  // This is only sound in specific code which is already messaging other
+  // processes, and doesn't need to worry about epochs or other properties of
+  // field synchronization.
+  template <size_t I, typename U>
+  void SetWithoutSyncing(U&& aValue) {
+    GetNonSyncingReference<I>() = std::move(aValue);
+  }
+
+  // Get a reference to a field that can modify without telling other
+  // processes about the change.
+  //
+  // This is only sound in specific code which is already messaging other
+  // processes, and doesn't need to worry about epochs or other properties of
+  // field synchronization.
+  template <size_t I>
+  auto& GetNonSyncingReference() {
+    return RawValues().Get(Index<I>{});
+  }
+
+  FieldStorage() = default;
+  explicit FieldStorage(Values&& aInit) : mValues(std::move(aInit)) {}
+
+ private:
+  template <typename Context>
+  friend class Transaction;
+
+  // Data Members
+  std::array<uint64_t, Values::count> mEpochs{};
+  Values mValues;
+};
+
+// Alternative return type enum for `CanSet` validators which allows specifying
+// more behaviour.
+enum class CanSetResult : uint8_t {
+  // The set attempt is denied. This is equivalent to returning `false`.
+  Deny,
+  // The set attempt is allowed. This is equivalent to returning `true`.
+  Allow,
+  // The set attempt is reverted non-fatally.
+  Revert,
+};
+
+// Helper type traits to use concrete types rather than generic forwarding
+// references for the `SetXXX` methods defined on the synced context type.
+//
+// This helps avoid potential issues where someone accidentally declares an
+// overload of these methods with slightly different types and different
+// behaviours. See bug 1659520.
+template <typename T>
+struct GetFieldSetterType {
+  using SetterArg = T;
+};
+template <>
+struct GetFieldSetterType<nsString> {
+  using SetterArg = const nsAString&;
+};
+template <>
+struct GetFieldSetterType<nsCString> {
+  using SetterArg = const nsACString&;
+};
+template <typename T>
+using FieldSetterType = typename GetFieldSetterType<T>::SetterArg;
+
+#define MOZ_DECL_SYNCED_CONTEXT_FIELD_INDEX(name, type) IDX_##name,
+
+#define MOZ_DECL_SYNCED_CONTEXT_FIELD_GETSET(name, type)                       \
+  const type& Get##name() const { return mFields.template Get<IDX_##name>(); } \
+                                                                               \
+  [[nodiscard]] nsresult Set##name(                                            \
+      ::mozilla::dom::syncedcontext::FieldSetterType<type> aValue) {           \
+    Transaction txn;                                                           \
+    txn.template Set<IDX_##name>(std::move(aValue));                           \
+    return txn.Commit(this);                                                   \
+  }                                                                            \
+  void Set##name(::mozilla::dom::syncedcontext::FieldSetterType<type> aValue,  \
+                 ErrorResult& aRv) {                                           \
+    nsresult rv = this->Set##name(std::move(aValue));                          \
+    if (NS_FAILED(rv)) {                                                       \
+      aRv.ThrowInvalidStateError("cannot set synced field '" #name             \
+                                 "': context is discarded");                   \
+    }                                                                          \
+  }
+
+#define MOZ_DECL_SYNCED_CONTEXT_TRANSACTION_SET(name, type)  \
+  template <typename U>                                      \
+  void Set##name(U&& aValue) {                               \
+    this->template Set<IDX_##name>(std::forward<U>(aValue)); \
+  }
+#define MOZ_DECL_SYNCED_CONTEXT_INDEX_TO_NAME(name, type) \
+  case IDX_##name:                                        \
+    return #name;
+
+#define MOZ_DECL_SYNCED_FIELD_INHERIT(name, type) \
+ public                                           \
+  syncedcontext::SizedField<IDX_##name, type, Size>,
+
+#define MOZ_DECL_SYNCED_CONTEXT_BASE_FIELD_GETTER(name, type) \
+  type& Get(FieldIndex<IDX_##name>) {                         \
+    return Field<IDX_##name, type>::mField;                   \
+  }                                                           \
+  const type& Get(FieldIndex<IDX_##name>) const {             \
+    return Field<IDX_##name, type>::mField;                   \
+  }
+
+// Declare a type as a synced context type.
+//
+// clazz is the name of the type being declared, and `eachfield` is a macro
+// which, when called with the name of the macro, will call that macro once for
+// each field in the synced context.
+#define MOZ_DECL_SYNCED_CONTEXT(clazz, eachfield)                              \
+ public:                                                                       \
+  /* Index constants for referring to each field in generic code */            \
+  enum FieldIndexes {                                                          \
+    eachfield(MOZ_DECL_SYNCED_CONTEXT_FIELD_INDEX) SYNCED_FIELD_COUNT          \
+  };                                                                           \
+                                                                               \
+  /* Helper for overloading methods like `CanSet` and `DidSet` */              \
+  template <size_t I>                                                          \
+  using FieldIndex = typename ::mozilla::dom::syncedcontext::Index<I>;         \
+                                                                               \
+  /* Fields contain all synced fields defined by                               \
+   * `eachfield(MOZ_DECL_SYNCED_FIELD_INHERIT)`, but only those where the size \
+   * of the field is equal to size Size will be present. We use SizedField to  \
+   * remove fields of the wrong size. */                                       \
+  template <size_t Size>                                                       \
+  struct Fields : eachfield(MOZ_DECL_SYNCED_FIELD_INHERIT)                     \
+                      syncedcontext::Empty<SYNCED_FIELD_COUNT, Size> {};       \
+                                                                               \
+  /* Struct containing the data for all synced fields as members. We filter    \
+   * sizes to lay out fields of size 1, then 2, then 4 and last 8 or greater.  \
+   * This way we don't need to consider packing when defining fields, but      \
+   * we'll just reorder them here.                                             \
+   */                                                                          \
+  struct BaseFieldValues : public Fields<1>,                                   \
+                           public Fields<2>,                                   \
+                           public Fields<4>,                                   \
+                           public Fields<8> {                                  \
+    template <size_t I>                                                        \
+    auto& Get() {                                                              \
+      return Get(FieldIndex<I>{});                                             \
+    }                                                                          \
+    template <size_t I>                                                        \
+    const auto& Get() const {                                                  \
+      return Get(FieldIndex<I>{});                                             \
+    }                                                                          \
+    eachfield(MOZ_DECL_SYNCED_CONTEXT_BASE_FIELD_GETTER)                       \
+  };                                                                           \
+  using FieldValues =                                                          \
+      typename ::mozilla::dom::syncedcontext::FieldValues<BaseFieldValues,     \
+                                                          SYNCED_FIELD_COUNT>; \
+                                                                               \
+ protected:                                                                    \
+  friend class ::mozilla::dom::syncedcontext::Transaction<clazz>;              \
+  ::mozilla::dom::syncedcontext::FieldStorage<FieldValues> mFields;            \
+                                                                               \
+ public:                                                                       \
+  /* Transaction types for bulk mutations */                                   \
+  using BaseTransaction = ::mozilla::dom::syncedcontext::Transaction<clazz>;   \
+  class Transaction final : public BaseTransaction {                           \
+   public:                                                                     \
+    eachfield(MOZ_DECL_SYNCED_CONTEXT_TRANSACTION_SET)                         \
+  };                                                                           \
+                                                                               \
+  /* Field name getter by field index */                                       \
+  static const char* FieldIndexToName(size_t aIndex) {                         \
+    switch (aIndex) { eachfield(MOZ_DECL_SYNCED_CONTEXT_INDEX_TO_NAME) }       \
+    return "<unknown>";                                                        \
+  }                                                                            \
+  eachfield(MOZ_DECL_SYNCED_CONTEXT_FIELD_GETSET)
+
+}  // namespace syncedcontext
+}  // namespace dom
+
+namespace ipc {
+
+template <typename Context>
+struct IPDLParamTraits<dom::syncedcontext::Transaction<Context>> {
+  typedef dom::syncedcontext::Transaction<Context> paramType;
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const paramType& aParam) {
+    aParam.Write(aWriter, aActor);
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   paramType* aResult) {
+    return aResult->Read(aReader, aActor);
+  }
+};
+
+template <typename Base, size_t Count>
+struct IPDLParamTraits<dom::syncedcontext::FieldValues<Base, Count>> {
+  typedef dom::syncedcontext::FieldValues<Base, Count> paramType;
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const paramType& aParam) {
+    aParam.Write(aWriter, aActor);
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   paramType* aResult) {
+    return aResult->Read(aReader, aActor);
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // !defined(mozilla_dom_SyncedContext_h)
diff --git a/docshell/base/SyncedContextInlines.h b/docshell/base/SyncedContextInlines.h
new file mode 100644
index 0000000000..e386e75b35
--- /dev/null
+++ b/docshell/base/SyncedContextInlines.h
@@ -0,0 +1,359 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_SyncedContextInlines_h
+#define mozilla_dom_SyncedContextInlines_h
+
+#include "mozilla/dom/SyncedContext.h"
+#include "mozilla/dom/BrowsingContextGroup.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/ContentChild.h"
+#include "nsReadableUtils.h"
+#include "mozilla/HalIPCUtils.h"
+
+namespace mozilla {
+namespace dom {
+namespace syncedcontext {
+
+template <typename T>
+struct IsMozillaMaybe : std::false_type {};
+template <typename T>
+struct IsMozillaMaybe<Maybe<T>> : std::true_type {};
+
+// A super-sketchy logging only function for generating a human-readable version
+// of the value of a synced context field.
+template <typename T>
+void FormatFieldValue(nsACString& aStr, const T& aValue) {
+  if constexpr (std::is_same_v<bool, T>) {
+    if (aValue) {
+      aStr.AppendLiteral("true");
+    } else {
+      aStr.AppendLiteral("false");
+    }
+  } else if constexpr (std::is_same_v<nsID, T>) {
+    aStr.Append(nsIDToCString(aValue).get());
+  } else if constexpr (std::is_integral_v<T>) {
+    aStr.AppendInt(aValue);
+  } else if constexpr (std::is_enum_v<T>) {
+    aStr.AppendInt(static_cast<std::underlying_type_t<T>>(aValue));
+  } else if constexpr (std::is_floating_point_v<T>) {
+    aStr.AppendFloat(aValue);
+  } else if constexpr (std::is_base_of_v<nsAString, T>) {
+    AppendUTF16toUTF8(aValue, aStr);
+  } else if constexpr (std::is_base_of_v<nsACString, T>) {
+    aStr.Append(aValue);
+  } else if constexpr (IsMozillaMaybe<T>::value) {
+    if (aValue) {
+      aStr.AppendLiteral("Some(");
+      FormatFieldValue(aStr, aValue.ref());
+      aStr.AppendLiteral(")");
+    } else {
+      aStr.AppendLiteral("Nothing");
+    }
+  } else {
+    aStr.AppendLiteral("???");
+  }
+}
+
+// Sketchy logging-only logic to generate a human-readable output of the actions
+// a synced context transaction is going to perform.
+template <typename Context>
+nsAutoCString FormatTransaction(
+    typename Transaction<Context>::IndexSet aModified,
+    const typename Context::FieldValues& aOldValues,
+    const typename Context::FieldValues& aNewValues) {
+  nsAutoCString result;
+  Context::FieldValues::EachIndex([&](auto idx) {
+    if (aModified.contains(idx)) {
+      result.Append(Context::FieldIndexToName(idx));
+      result.AppendLiteral("(");
+      FormatFieldValue(result, aOldValues.Get(idx));
+      result.AppendLiteral("->");
+      FormatFieldValue(result, aNewValues.Get(idx));
+      result.AppendLiteral(") ");
+    }
+  });
+  return result;
+}
+
+template <typename Context>
+nsCString FormatValidationError(
+    typename Transaction<Context>::IndexSet aFailedFields, const char* prefix) {
+  MOZ_ASSERT(!aFailedFields.isEmpty());
+  return nsDependentCString{prefix} +
+         StringJoin(", "_ns, aFailedFields,
+                    [](nsACString& dest, const auto& idx) {
+                      dest.Append(Context::FieldIndexToName(idx));
+                    });
+}
+
+template <typename Context>
+nsresult Transaction<Context>::Commit(Context* aOwner) {
+  if (NS_WARN_IF(aOwner->IsDiscarded())) {
+    return NS_ERROR_DOM_INVALID_STATE_ERR;
+  }
+
+  IndexSet failedFields = Validate(aOwner, nullptr);
+  if (!failedFields.isEmpty()) {
+    nsCString error = FormatValidationError<Context>(
+        failedFields, "CanSet failed for field(s): ");
+    MOZ_CRASH_UNSAFE_PRINTF("%s", error.get());
+  }
+
+  if (mModified.isEmpty()) {
+    return NS_OK;
+  }
+
+  if (XRE_IsContentProcess()) {
+    ContentChild* cc = ContentChild::GetSingleton();
+
+    // Increment the field epoch for fields affected by this transaction.
+    uint64_t epoch = cc->NextBrowsingContextFieldEpoch();
+    EachIndex([&](auto idx) {
+      if (mModified.contains(idx)) {
+        FieldEpoch(idx, aOwner) = epoch;
+      }
+    });
+
+    // Tell our derived class to send the correct "Commit" IPC message.
+    aOwner->SendCommitTransaction(cc, *this, epoch);
+  } else {
+    MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+
+    // Tell our derived class to send the correct "Commit" IPC messages.
+    BrowsingContextGroup* group = aOwner->Group();
+    group->EachParent([&](ContentParent* aParent) {
+      aOwner->SendCommitTransaction(aParent, *this,
+                                    aParent->GetBrowsingContextFieldEpoch());
+    });
+  }
+
+  Apply(aOwner, /* aFromIPC */ false);
+  return NS_OK;
+}
+
+template <typename Context>
+mozilla::ipc::IPCResult Transaction<Context>::CommitFromIPC(
+    const MaybeDiscarded<Context>& aOwner, ContentParent* aSource) {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+  if (aOwner.IsNullOrDiscarded()) {
+    MOZ_LOG(Context::GetSyncLog(), LogLevel::Debug,
+            ("IPC: Trying to send a message to dead or detached context"));
+    return IPC_OK();
+  }
+  Context* owner = aOwner.get();
+
+  // Validate that the set from content is allowed before continuing.
+  IndexSet failedFields = Validate(owner, aSource);
+  if (!failedFields.isEmpty()) {
+    nsCString error = FormatValidationError<Context>(
+        failedFields,
+        "Invalid Transaction from Child - CanSet failed for field(s): ");
+    // data-review+ at https://bugzilla.mozilla.org/show_bug.cgi?id=1618992#c7
+    return IPC_FAIL_UNSAFE_PRINTF(aSource, "%s", error.get());
+  }
+
+  // Validate may have dropped some fields from the transaction, check it's not
+  // empty before continuing.
+  if (mModified.isEmpty()) {
+    return IPC_OK();
+  }
+
+  BrowsingContextGroup* group = owner->Group();
+  group->EachOtherParent(aSource, [&](ContentParent* aParent) {
+    owner->SendCommitTransaction(aParent, *this,
+                                 aParent->GetBrowsingContextFieldEpoch());
+  });
+
+  Apply(owner, /* aFromIPC */ true);
+  return IPC_OK();
+}
+
+template <typename Context>
+mozilla::ipc::IPCResult Transaction<Context>::CommitFromIPC(
+    const MaybeDiscarded<Context>& aOwner, uint64_t aEpoch,
+    ContentChild* aSource) {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsContentProcess());
+  if (aOwner.IsNullOrDiscarded()) {
+    MOZ_LOG(Context::GetSyncLog(), LogLevel::Debug,
+            ("ChildIPC: Trying to send a message to dead or detached context"));
+    return IPC_OK();
+  }
+  Context* owner = aOwner.get();
+
+  // Clear any fields which have been obsoleted by the epoch.
+  EachIndex([&](auto idx) {
+    if (mModified.contains(idx) && FieldEpoch(idx, owner) > aEpoch) {
+      MOZ_LOG(
+          Context::GetSyncLog(), LogLevel::Debug,
+          ("Transaction::Obsoleted(#%" PRIx64 ", %" PRIu64 ">%" PRIu64 "): %s",
+           owner->Id(), FieldEpoch(idx, owner), aEpoch,
+           Context::FieldIndexToName(idx)));
+      mModified -= idx;
+    }
+  });
+
+  if (mModified.isEmpty()) {
+    return IPC_OK();
+  }
+
+  Apply(owner, /* aFromIPC */ true);
+  return IPC_OK();
+}
+
+template <typename Context>
+void Transaction<Context>::Apply(Context* aOwner, bool aFromIPC) {
+  MOZ_ASSERT(!mModified.isEmpty());
+
+  MOZ_LOG(
+      Context::GetSyncLog(), LogLevel::Debug,
+      ("Transaction::Apply(#%" PRIx64 ", %s): %s", aOwner->Id(),
+       aFromIPC ? "ipc" : "local",
+       FormatTransaction<Context>(mModified, aOwner->mFields.mValues, mValues)
+           .get()));
+
+  EachIndex([&](auto idx) {
+    if (mModified.contains(idx)) {
+      auto& txnField = mValues.Get(idx);
+      auto& ownerField = aOwner->mFields.mValues.Get(idx);
+      std::swap(ownerField, txnField);
+      aOwner->DidSet(idx);
+      aOwner->DidSet(idx, std::move(txnField));
+    }
+  });
+  mModified.clear();
+}
+
+template <typename Context>
+void Transaction<Context>::CommitWithoutSyncing(Context* aOwner) {
+  MOZ_LOG(
+      Context::GetSyncLog(), LogLevel::Debug,
+      ("Transaction::CommitWithoutSyncing(#%" PRIx64 "): %s", aOwner->Id(),
+       FormatTransaction<Context>(mModified, aOwner->mFields.mValues, mValues)
+           .get()));
+
+  EachIndex([&](auto idx) {
+    if (mModified.contains(idx)) {
+      aOwner->mFields.mValues.Get(idx) = std::move(mValues.Get(idx));
+    }
+  });
+  mModified.clear();
+}
+
+inline CanSetResult AsCanSetResult(CanSetResult aValue) { return aValue; }
+inline CanSetResult AsCanSetResult(bool aValue) {
+  return aValue ? CanSetResult::Allow : CanSetResult::Deny;
+}
+
+template <typename Context>
+typename Transaction<Context>::IndexSet Transaction<Context>::Validate(
+    Context* aOwner, ContentParent* aSource) {
+  IndexSet failedFields;
+  Transaction<Context> revertTxn;
+
+  EachIndex([&](auto idx) {
+    if (!mModified.contains(idx)) {
+      return;
+    }
+
+    switch (AsCanSetResult(aOwner->CanSet(idx, mValues.Get(idx), aSource))) {
+      case CanSetResult::Allow:
+        break;
+      case CanSetResult::Deny:
+        failedFields += idx;
+        break;
+      case CanSetResult::Revert:
+        revertTxn.mValues.Get(idx) = aOwner->mFields.mValues.Get(idx);
+        revertTxn.mModified += idx;
+        break;
+    }
+  });
+
+  // If any changes need to be reverted, log them, remove them from this
+  // transaction, and optionally send a message to the source process.
+  if (!revertTxn.mModified.isEmpty()) {
+    // NOTE: Logging with modified IndexSet from revert transaction, and values
+    // from this transaction, so we log the failed values we're going to revert.
+    MOZ_LOG(
+        Context::GetSyncLog(), LogLevel::Debug,
+        ("Transaction::PartialRevert(#%" PRIx64 ", pid %" PRIPID "): %s",
+         aOwner->Id(), aSource ? aSource->OtherPid() : base::kInvalidProcessId,
+         FormatTransaction<Context>(revertTxn.mModified, mValues,
+                                    revertTxn.mValues)
+             .get()));
+
+    mModified -= revertTxn.mModified;
+
+    if (aSource) {
+      aOwner->SendCommitTransaction(aSource, revertTxn,
+                                    aSource->GetBrowsingContextFieldEpoch());
+    }
+  }
+  return failedFields;
+}
+
+template <typename Context>
+void Transaction<Context>::Write(IPC::MessageWriter* aWriter,
+                                 mozilla::ipc::IProtocol* aActor) const {
+  // Record which field indices will be included, and then write those fields
+  // out.
+  typename IndexSet::serializedType modified = mModified.serialize();
+  WriteIPDLParam(aWriter, aActor, modified);
+  EachIndex([&](auto idx) {
+    if (mModified.contains(idx)) {
+      WriteIPDLParam(aWriter, aActor, mValues.Get(idx));
+    }
+  });
+}
+
+template <typename Context>
+bool Transaction<Context>::Read(IPC::MessageReader* aReader,
+                                mozilla::ipc::IProtocol* aActor) {
+  // Read in which field indices were sent by the remote, followed by the fields
+  // identified by those indices.
+  typename IndexSet::serializedType modified =
+      typename IndexSet::serializedType{};
+  if (!ReadIPDLParam(aReader, aActor, &modified)) {
+    return false;
+  }
+  mModified.deserialize(modified);
+
+  bool ok = true;
+  EachIndex([&](auto idx) {
+    if (ok && mModified.contains(idx)) {
+      ok = ReadIPDLParam(aReader, aActor, &mValues.Get(idx));
+    }
+  });
+  return ok;
+}
+
+template <typename Base, size_t Count>
+void FieldValues<Base, Count>::Write(IPC::MessageWriter* aWriter,
+                                     mozilla::ipc::IProtocol* aActor) const {
+  // XXX The this-> qualification is necessary to work around a bug in older gcc
+  // versions causing an ICE.
+  EachIndex([&](auto idx) { WriteIPDLParam(aWriter, aActor, this->Get(idx)); });
+}
+
+template <typename Base, size_t Count>
+bool FieldValues<Base, Count>::Read(IPC::MessageReader* aReader,
+                                    mozilla::ipc::IProtocol* aActor) {
+  bool ok = true;
+  EachIndex([&](auto idx) {
+    if (ok) {
+      // XXX The this-> qualification is necessary to work around a bug in older
+      // gcc versions causing an ICE.
+      ok = ReadIPDLParam(aReader, aActor, &this->Get(idx));
+    }
+  });
+  return ok;
+}
+
+}  // namespace syncedcontext
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // !defined(mozilla_dom_SyncedContextInlines_h)
diff --git a/docshell/base/URIFixup.sys.mjs b/docshell/base/URIFixup.sys.mjs
new file mode 100644
index 0000000000..6fde38a310
--- /dev/null
+++ b/docshell/base/URIFixup.sys.mjs
@@ -0,0 +1,1306 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
+ * vim: sw=2 ts=2 sts=2 expandtab
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This component handles fixing up URIs, by correcting obvious typos and adding
+ * missing schemes.
+ * URI references:
+ *   http://www.faqs.org/rfcs/rfc1738.html
+ *   http://www.faqs.org/rfcs/rfc2396.html
+ */
+
+// TODO (Bug 1641220) getFixupURIInfo has a complex logic, that likely could be
+// simplified, but the risk of regressing its behavior is high.
+/* eslint complexity: ["error", 43] */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "externalProtocolService",
+  "@mozilla.org/uriloader/external-protocol-service;1",
+  "nsIExternalProtocolService"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "defaultProtocolHandler",
+  "@mozilla.org/network/protocol;1?name=default",
+  "nsIProtocolHandler"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "fileProtocolHandler",
+  "@mozilla.org/network/protocol;1?name=file",
+  "nsIFileProtocolHandler"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "handlerService",
+  "@mozilla.org/uriloader/handler-service;1",
+  "nsIHandlerService"
+);
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "fixupSchemeTypos",
+  "browser.fixup.typo.scheme",
+  true
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "dnsFirstForSingleWords",
+  "browser.fixup.dns_first_for_single_words",
+  false
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "keywordEnabled",
+  "keyword.enabled",
+  true
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "alternateProtocol",
+  "browser.fixup.alternate.protocol",
+  "https"
+);
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "dnsResolveFullyQualifiedNames",
+  "browser.urlbar.dnsResolveFullyQualifiedNames",
+  true
+);
+
+const {
+  FIXUP_FLAG_NONE,
+  FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP,
+  FIXUP_FLAGS_MAKE_ALTERNATE_URI,
+  FIXUP_FLAG_PRIVATE_CONTEXT,
+  FIXUP_FLAG_FIX_SCHEME_TYPOS,
+} = Ci.nsIURIFixup;
+
+const COMMON_PROTOCOLS = ["http", "https", "file"];
+
+// Regex used to identify user:password tokens in url strings.
+// This is not a strict valid characters check, because we try to fixup this
+// part of the url too.
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "userPasswordRegex",
+  () => /^([a-z+.-]+:\/{0,3})*([^\/@]+@).+/i
+);
+
+// Regex used to identify the string that starts with port expression.
+ChromeUtils.defineLazyGetter(lazy, "portRegex", () => /^:\d{1,5}([?#/]|$)/);
+
+// Regex used to identify numbers.
+ChromeUtils.defineLazyGetter(lazy, "numberRegex", () => /^[0-9]+(\.[0-9]+)?$/);
+
+// Regex used to identify tab separated content (having at least 2 tabs).
+ChromeUtils.defineLazyGetter(lazy, "maxOneTabRegex", () => /^[^\t]*\t?[^\t]*$/);
+
+// Regex used to test if a string with a protocol might instead be a url
+// without a protocol but with a port:
+//
+//   <hostname>:<port> or
+//   <hostname>:<port>/
+//
+// Where <hostname> is a string of alphanumeric characters and dashes
+// separated by dots.
+// and <port> is a 5 or less digits. This actually breaks the rfc2396
+// definition of a scheme which allows dots in schemes.
+//
+// Note:
+//   People expecting this to work with
+//   <user>:<password>@<host>:<port>/<url-path> will be disappointed!
+//
+// Note: Parser could be a lot tighter, tossing out silly hostnames
+//       such as those containing consecutive dots and so on.
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "possiblyHostPortRegex",
+  () => /^[a-z0-9-]+(\.[a-z0-9-]+)*:[0-9]{1,5}([/?#]|$)/i
+);
+
+// Regex used to strip newlines.
+ChromeUtils.defineLazyGetter(lazy, "newLinesRegex", () => /[\r\n]/g);
+
+// Regex used to match a possible protocol.
+// This resembles the logic in Services.io.extractScheme, thus \t is admitted
+// and stripped later. We don't use Services.io.extractScheme because of
+// performance bottleneck caused by crossing XPConnect.
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "possibleProtocolRegex",
+  () => /^([a-z][a-z0-9.+\t-]*)(:|;)?(\/\/)?/i
+);
+
+// Regex used to match IPs. Note that these are not made to validate IPs, but
+// just to detect strings that look like an IP. They also skip protocol.
+// For IPv4 this also accepts a shorthand format with just 2 dots.
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "IPv4LikeRegex",
+  () => /^(?:[a-z+.-]+:\/*(?!\/))?(?:\d{1,3}\.){2,3}\d{1,3}(?::\d+|\/)?/i
+);
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "IPv6LikeRegex",
+  () =>
+    /^(?:[a-z+.-]+:\/*(?!\/))?\[(?:[0-9a-f]{0,4}:){0,7}[0-9a-f]{0,4}\]?(?::\d+|\/)?/i
+);
+
+// Regex used to detect spaces in URL credentials.
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "DetectSpaceInCredentialsRegex",
+  () => /^[^/]*\s[^/]*@/
+);
+
+// Cache of known domains.
+ChromeUtils.defineLazyGetter(lazy, "knownDomains", () => {
+  const branch = "browser.fixup.domainwhitelist.";
+  let domains = new Set(
+    Services.prefs
+      .getChildList(branch)
+      .filter(p => Services.prefs.getBoolPref(p, false))
+      .map(p => p.substring(branch.length))
+  );
+  // Hold onto the observer to avoid it being GC-ed.
+  domains._observer = {
+    observe(subject, topic, data) {
+      let domain = data.substring(branch.length);
+      if (Services.prefs.getBoolPref(data, false)) {
+        domains.add(domain);
+      } else {
+        domains.delete(domain);
+      }
+    },
+    QueryInterface: ChromeUtils.generateQI([
+      "nsIObserver",
+      "nsISupportsWeakReference",
+    ]),
+  };
+  Services.prefs.addObserver(branch, domains._observer, true);
+  return domains;
+});
+
+// Cache of known suffixes.
+// This works differently from the known domains, because when we examine a
+// domain we can't tell how many dot-separated parts constitute the suffix.
+// We create a Map keyed by the last dotted part, containing a Set of
+// all the suffixes ending with that part:
+//   "two" => ["two"]
+//   "three" => ["some.three", "three"]
+// When searching we can restrict the linear scan based on the last part.
+// The ideal structure for this would be a Directed Acyclic Word Graph, but
+// since we expect this list to be small it's not worth the complication.
+ChromeUtils.defineLazyGetter(lazy, "knownSuffixes", () => {
+  const branch = "browser.fixup.domainsuffixwhitelist.";
+  let suffixes = new Map();
+  let prefs = Services.prefs
+    .getChildList(branch)
+    .filter(p => Services.prefs.getBoolPref(p, false));
+  for (let pref of prefs) {
+    let suffix = pref.substring(branch.length);
+    let lastPart = suffix.substr(suffix.lastIndexOf(".") + 1);
+    if (lastPart) {
+      let entries = suffixes.get(lastPart);
+      if (!entries) {
+        entries = new Set();
+        suffixes.set(lastPart, entries);
+      }
+      entries.add(suffix);
+    }
+  }
+  // Hold onto the observer to avoid it being GC-ed.
+  suffixes._observer = {
+    observe(subject, topic, data) {
+      let suffix = data.substring(branch.length);
+      let lastPart = suffix.substr(suffix.lastIndexOf(".") + 1);
+      let entries = suffixes.get(lastPart);
+      if (Services.prefs.getBoolPref(data, false)) {
+        // Add the suffix.
+        if (!entries) {
+          entries = new Set();
+          suffixes.set(lastPart, entries);
+        }
+        entries.add(suffix);
+      } else if (entries) {
+        // Remove the suffix.
+        entries.delete(suffix);
+        if (!entries.size) {
+          suffixes.delete(lastPart);
+        }
+      }
+    },
+    QueryInterface: ChromeUtils.generateQI([
+      "nsIObserver",
+      "nsISupportsWeakReference",
+    ]),
+  };
+  Services.prefs.addObserver(branch, suffixes._observer, true);
+  return suffixes;
+});
+
+export function URIFixup() {
+  // There are cases that nsIExternalProtocolService.externalProtocolHandlerExists() does
+  // not work well and returns always true due to flatpak. In this case, in order to
+  // fallback to nsIHandlerService.exits(), we test whether can trust
+  // nsIExternalProtocolService here.
+  this._trustExternalProtocolService =
+    !lazy.externalProtocolService.externalProtocolHandlerExists(
+      `__dummy${Date.now()}__`
+    );
+}
+
+URIFixup.prototype = {
+  get FIXUP_FLAG_NONE() {
+    return FIXUP_FLAG_NONE;
+  },
+  get FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP() {
+    return FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP;
+  },
+  get FIXUP_FLAGS_MAKE_ALTERNATE_URI() {
+    return FIXUP_FLAGS_MAKE_ALTERNATE_URI;
+  },
+  get FIXUP_FLAG_PRIVATE_CONTEXT() {
+    return FIXUP_FLAG_PRIVATE_CONTEXT;
+  },
+  get FIXUP_FLAG_FIX_SCHEME_TYPOS() {
+    return FIXUP_FLAG_FIX_SCHEME_TYPOS;
+  },
+
+  getFixupURIInfo(uriString, fixupFlags = FIXUP_FLAG_NONE) {
+    let isPrivateContext = fixupFlags & FIXUP_FLAG_PRIVATE_CONTEXT;
+    let untrimmedURIString = uriString;
+
+    // Eliminate embedded newlines, which single-line text fields now allow,
+    // and cleanup the empty spaces and tabs that might be on each end.
+    uriString = uriString.trim().replace(lazy.newLinesRegex, "");
+
+    if (!uriString) {
+      throw new Components.Exception(
+        "Should pass a non-null uri",
+        Cr.NS_ERROR_FAILURE
+      );
+    }
+
+    let info = new URIFixupInfo(uriString);
+
+    const { scheme, fixedSchemeUriString, fixupChangedProtocol } =
+      extractScheme(uriString, fixupFlags);
+    uriString = fixedSchemeUriString;
+    info.fixupChangedProtocol = fixupChangedProtocol;
+
+    if (scheme == "view-source") {
+      let { preferredURI, postData } = fixupViewSource(uriString, fixupFlags);
+      info.preferredURI = info.fixedURI = preferredURI;
+      info.postData = postData;
+      return info;
+    }
+
+    if (scheme.length < 2) {
+      // Check if it is a file path. We skip most schemes because the only case
+      // where a file path may look like having a scheme is "X:" on Windows.
+      let fileURI = fileURIFixup(uriString);
+      if (fileURI) {
+        info.preferredURI = info.fixedURI = fileURI;
+        info.fixupChangedProtocol = true;
+        return info;
+      }
+    }
+
+    const isCommonProtocol = COMMON_PROTOCOLS.includes(scheme);
+
+    let canHandleProtocol =
+      scheme &&
+      (isCommonProtocol ||
+        Services.io.getProtocolHandler(scheme) != lazy.defaultProtocolHandler ||
+        this._isKnownExternalProtocol(scheme));
+
+    if (
+      canHandleProtocol ||
+      // If it's an unknown handler and the given URL looks like host:port or
+      // has a user:password we can't pass it to the external protocol handler.
+      // We'll instead try fixing it with http later.
+      (!lazy.possiblyHostPortRegex.test(uriString) &&
+        !lazy.userPasswordRegex.test(uriString))
+    ) {
+      // Just try to create an URL out of it.
+      try {
+        info.fixedURI = Services.io.newURI(uriString);
+      } catch (ex) {
+        if (ex.result != Cr.NS_ERROR_MALFORMED_URI) {
+          throw ex;
+        }
+      }
+    }
+
+    // We're dealing with a theoretically valid URI but we have no idea how to
+    // load it. (e.g. "christmas:humbug")
+    // It's more likely the user wants to search, and so we chuck this over to
+    // their preferred search provider.
+    // TODO (Bug 1588118): Should check FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP
+    // instead of FIXUP_FLAG_FIX_SCHEME_TYPOS.
+    if (
+      info.fixedURI &&
+      lazy.keywordEnabled &&
+      fixupFlags & FIXUP_FLAG_FIX_SCHEME_TYPOS &&
+      scheme &&
+      !canHandleProtocol
+    ) {
+      tryKeywordFixupForURIInfo(uriString, info, isPrivateContext);
+    }
+
+    if (info.fixedURI) {
+      if (!info.preferredURI) {
+        maybeSetAlternateFixedURI(info, fixupFlags);
+        info.preferredURI = info.fixedURI;
+      }
+      fixupConsecutiveDotsHost(info);
+      return info;
+    }
+
+    // Fix up protocol string before calling KeywordURIFixup, because
+    // it cares about the hostname of such URIs.
+    // Prune duff protocol schemes:
+    //   ://totallybroken.url.com
+    //   //shorthand.url.com
+    let inputHadDuffProtocol =
+      uriString.startsWith("://") || uriString.startsWith("//");
+    if (inputHadDuffProtocol) {
+      uriString = uriString.replace(/^:?\/\//, "");
+    }
+
+    // Avoid fixing up content that looks like tab-separated values.
+    // Assume that 1 tab is accidental, but more than 1 implies this is
+    // supposed to be tab-separated content.
+    if (
+      !isCommonProtocol &&
+      lazy.maxOneTabRegex.test(uriString) &&
+      !lazy.DetectSpaceInCredentialsRegex.test(untrimmedURIString)
+    ) {
+      let uriWithProtocol = fixupURIProtocol(uriString);
+      if (uriWithProtocol) {
+        info.fixedURI = uriWithProtocol;
+        info.fixupChangedProtocol = true;
+        info.wasSchemelessInput = true;
+        maybeSetAlternateFixedURI(info, fixupFlags);
+        info.preferredURI = info.fixedURI;
+        // Check if it's a forced visit. The user can enforce a visit by
+        // appending a slash, but the string must be in a valid uri format.
+        if (uriString.endsWith("/")) {
+          fixupConsecutiveDotsHost(info);
+          return info;
+        }
+      }
+    }
+
+    // Handle "www.<something>" as a URI.
+    const asciiHost = info.fixedURI?.asciiHost;
+    if (
+      asciiHost?.length > 4 &&
+      asciiHost?.startsWith("www.") &&
+      asciiHost?.lastIndexOf(".") == 3
+    ) {
+      return info;
+    }
+
+    // Memoize the public suffix check, since it may be expensive and should
+    // only run once when necessary.
+    let suffixInfo;
+    function checkSuffix(info) {
+      if (!suffixInfo) {
+        suffixInfo = checkAndFixPublicSuffix(info);
+      }
+      return suffixInfo;
+    }
+
+    // See if it is a keyword and whether a keyword must be fixed up.
+    if (
+      lazy.keywordEnabled &&
+      fixupFlags & FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP &&
+      !inputHadDuffProtocol &&
+      !checkSuffix(info).suffix &&
+      keywordURIFixup(uriString, info, isPrivateContext)
+    ) {
+      fixupConsecutiveDotsHost(info);
+      return info;
+    }
+
+    if (
+      info.fixedURI &&
+      (!info.fixupChangedProtocol || !checkSuffix(info).hasUnknownSuffix)
+    ) {
+      fixupConsecutiveDotsHost(info);
+      return info;
+    }
+
+    // If we still haven't been able to construct a valid URI, try to force a
+    // keyword match.
+    if (lazy.keywordEnabled && fixupFlags & FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP) {
+      tryKeywordFixupForURIInfo(info.originalInput, info, isPrivateContext);
+    }
+
+    if (!info.preferredURI) {
+      // We couldn't salvage anything.
+      throw new Components.Exception(
+        "Couldn't build a valid uri",
+        Cr.NS_ERROR_MALFORMED_URI
+      );
+    }
+
+    fixupConsecutiveDotsHost(info);
+    return info;
+  },
+
+  webNavigationFlagsToFixupFlags(href, navigationFlags) {
+    try {
+      Services.io.newURI(href);
+      // Remove LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP for valid uris.
+      navigationFlags &=
+        ~Ci.nsIWebNavigation.LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+    } catch (ex) {}
+
+    let fixupFlags = FIXUP_FLAG_NONE;
+    if (
+      navigationFlags & Ci.nsIWebNavigation.LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP
+    ) {
+      fixupFlags |= FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP;
+    }
+    if (navigationFlags & Ci.nsIWebNavigation.LOAD_FLAGS_FIXUP_SCHEME_TYPOS) {
+      fixupFlags |= FIXUP_FLAG_FIX_SCHEME_TYPOS;
+    }
+    return fixupFlags;
+  },
+
+  keywordToURI(keyword, isPrivateContext) {
+    if (Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT) {
+      // There's no search service in the content process, thus all the calls
+      // from it that care about keywords conversion should go through the
+      // parent process.
+      throw new Components.Exception(
+        "Can't invoke URIFixup in the content process",
+        Cr.NS_ERROR_NOT_AVAILABLE
+      );
+    }
+    let info = new URIFixupInfo(keyword);
+
+    // Strip leading "?" and leading/trailing spaces from aKeyword
+    if (keyword.startsWith("?")) {
+      keyword = keyword.substring(1);
+    }
+    keyword = keyword.trim();
+
+    if (!Services.search.hasSuccessfullyInitialized) {
+      return info;
+    }
+
+    // Try falling back to the search service's default search engine
+    // We must use an appropriate search engine depending on the private
+    // context.
+    let engine = isPrivateContext
+      ? Services.search.defaultPrivateEngine
+      : Services.search.defaultEngine;
+
+    // We allow default search plugins to specify alternate parameters that are
+    // specific to keyword searches.
+    let responseType = null;
+    if (engine.supportsResponseType("application/x-moz-keywordsearch")) {
+      responseType = "application/x-moz-keywordsearch";
+    }
+    let submission = engine.getSubmission(keyword, responseType, "keyword");
+    if (
+      !submission ||
+      // For security reasons (avoid redirecting to file, data, or other unsafe
+      // protocols) we only allow fixup to http/https search engines.
+      !submission.uri.scheme.startsWith("http")
+    ) {
+      throw new Components.Exception(
+        "Invalid search submission uri",
+        Cr.NS_ERROR_NOT_AVAILABLE
+      );
+    }
+    let submissionPostDataStream = submission.postData;
+    if (submissionPostDataStream) {
+      info.postData = submissionPostDataStream;
+    }
+
+    info.keywordProviderName = engine.name;
+    info.keywordAsSent = keyword;
+    info.preferredURI = submission.uri;
+    return info;
+  },
+
+  forceHttpFixup(uriString) {
+    if (!uriString) {
+      throw new Components.Exception(
+        "Should pass a non-null uri",
+        Cr.NS_ERROR_FAILURE
+      );
+    }
+
+    let info = new URIFixupInfo(uriString);
+    let { scheme, fixedSchemeUriString, fixupChangedProtocol } = extractScheme(
+      uriString,
+      FIXUP_FLAG_FIX_SCHEME_TYPOS
+    );
+
+    if (scheme != "http" && scheme != "https") {
+      throw new Components.Exception(
+        "Scheme should be either http or https",
+        Cr.NS_ERROR_FAILURE
+      );
+    }
+
+    info.fixupChangedProtocol = fixupChangedProtocol;
+    info.fixedURI = Services.io.newURI(fixedSchemeUriString);
+
+    let host = info.fixedURI.host;
+    if (host != "http" && host != "https" && host != "localhost") {
+      let modifiedHostname = maybeAddPrefixAndSuffix(host);
+      updateHostAndScheme(info, modifiedHostname);
+      info.preferredURI = info.fixedURI;
+    }
+
+    return info;
+  },
+
+  checkHost(uri, listener, originAttributes) {
+    let { displayHost, asciiHost } = uri;
+    if (!displayHost) {
+      throw new Components.Exception(
+        "URI must have displayHost",
+        Cr.NS_ERROR_FAILURE
+      );
+    }
+    if (!asciiHost) {
+      throw new Components.Exception(
+        "URI must have asciiHost",
+        Cr.NS_ERROR_FAILURE
+      );
+    }
+
+    let isIPv4Address = host => {
+      let parts = host.split(".");
+      if (parts.length != 4) {
+        return false;
+      }
+      return parts.every(part => {
+        let n = parseInt(part, 10);
+        return n >= 0 && n <= 255;
+      });
+    };
+
+    // Avoid showing fixup information if we're suggesting an IP. Note that
+    // decimal representations of IPs are normalized to a 'regular'
+    // dot-separated IP address by network code, but that only happens for
+    // numbers that don't overflow. Longer numbers do not get normalized,
+    // but still work to access IP addresses. So for instance,
+    // 1097347366913 (ff7f000001) gets resolved by using the final bytes,
+    // making it the same as 7f000001, which is 127.0.0.1 aka localhost.
+    // While 2130706433 would get normalized by network, 1097347366913
+    // does not, and we have to deal with both cases here:
+    if (isIPv4Address(asciiHost) || /^(?:\d+|0x[a-f0-9]+)$/i.test(asciiHost)) {
+      return;
+    }
+
+    // For dotless hostnames, we want to ensure this ends with a '.' but don't
+    // want the . showing up in the UI if we end up notifying the user, so we
+    // use a separate variable.
+    let lookupName = displayHost;
+    if (lazy.dnsResolveFullyQualifiedNames && !lookupName.includes(".")) {
+      lookupName += ".";
+    }
+
+    Services.obs.notifyObservers(null, "uri-fixup-check-dns");
+    Services.dns.asyncResolve(
+      lookupName,
+      Ci.nsIDNSService.RESOLVE_TYPE_DEFAULT,
+      0,
+      null,
+      listener,
+      Services.tm.mainThread,
+      originAttributes
+    );
+  },
+
+  isDomainKnown,
+
+  _isKnownExternalProtocol(scheme) {
+    if (this._trustExternalProtocolService) {
+      return lazy.externalProtocolService.externalProtocolHandlerExists(scheme);
+    }
+
+    try {
+      // nsIExternalProtocolService.getProtocolHandlerInfo() on Android throws
+      // error due to not implemented.
+      return lazy.handlerService.exists(
+        lazy.externalProtocolService.getProtocolHandlerInfo(scheme)
+      );
+    } catch (e) {
+      return false;
+    }
+  },
+
+  classID: Components.ID("{c6cf88b7-452e-47eb-bdc9-86e3561648ef}"),
+  QueryInterface: ChromeUtils.generateQI(["nsIURIFixup"]),
+};
+
+export function URIFixupInfo(originalInput = "") {
+  this._originalInput = originalInput;
+}
+
+URIFixupInfo.prototype = {
+  set consumer(consumer) {
+    this._consumer = consumer || null;
+  },
+  get consumer() {
+    return this._consumer || null;
+  },
+
+  set preferredURI(uri) {
+    this._preferredURI = uri;
+  },
+  get preferredURI() {
+    return this._preferredURI || null;
+  },
+
+  set fixedURI(uri) {
+    this._fixedURI = uri;
+  },
+  get fixedURI() {
+    return this._fixedURI || null;
+  },
+
+  set keywordProviderName(name) {
+    this._keywordProviderName = name;
+  },
+  get keywordProviderName() {
+    return this._keywordProviderName || "";
+  },
+
+  set keywordAsSent(keyword) {
+    this._keywordAsSent = keyword;
+  },
+  get keywordAsSent() {
+    return this._keywordAsSent || "";
+  },
+
+  set wasSchemelessInput(changed) {
+    this._wasSchemelessInput = changed;
+  },
+  get wasSchemelessInput() {
+    return !!this._wasSchemelessInput;
+  },
+
+  set fixupChangedProtocol(changed) {
+    this._fixupChangedProtocol = changed;
+  },
+  get fixupChangedProtocol() {
+    return !!this._fixupChangedProtocol;
+  },
+
+  set fixupCreatedAlternateURI(changed) {
+    this._fixupCreatedAlternateURI = changed;
+  },
+  get fixupCreatedAlternateURI() {
+    return !!this._fixupCreatedAlternateURI;
+  },
+
+  set originalInput(input) {
+    this._originalInput = input;
+  },
+  get originalInput() {
+    return this._originalInput || "";
+  },
+
+  set postData(postData) {
+    this._postData = postData;
+  },
+  get postData() {
+    return this._postData || null;
+  },
+
+  classID: Components.ID("{33d75835-722f-42c0-89cc-44f328e56a86}"),
+  QueryInterface: ChromeUtils.generateQI(["nsIURIFixupInfo"]),
+};
+
+// Helpers
+
+/**
+ * Implementation of isDomainKnown, so we don't have to go through the
+ * service.
+ * @param {string} asciiHost
+ * @returns {boolean} whether the domain is known
+ */
+function isDomainKnown(asciiHost) {
+  if (lazy.dnsFirstForSingleWords) {
+    return true;
+  }
+  // Check if this domain is known as an actual
+  // domain (which will prevent a keyword query)
+  // Note that any processing of the host here should stay in sync with
+  // code in the front-end(s) that set the pref.
+  let lastDotIndex = asciiHost.lastIndexOf(".");
+  if (lastDotIndex == asciiHost.length - 1) {
+    asciiHost = asciiHost.substring(0, asciiHost.length - 1);
+    lastDotIndex = asciiHost.lastIndexOf(".");
+  }
+  if (lazy.knownDomains.has(asciiHost.toLowerCase())) {
+    return true;
+  }
+  // If there's no dot or only a leading dot we are done, otherwise we'll check
+  // against the known suffixes.
+  if (lastDotIndex <= 0) {
+    return false;
+  }
+  // Don't use getPublicSuffix here, since the suffix is not in the PSL,
+  // thus it couldn't tell if the suffix is made up of one or multiple
+  // dot-separated parts.
+  let lastPart = asciiHost.substr(lastDotIndex + 1);
+  let suffixes = lazy.knownSuffixes.get(lastPart);
+  if (suffixes) {
+    return Array.from(suffixes).some(s => asciiHost.endsWith(s));
+  }
+  return false;
+}
+
+/**
+ * Checks the suffix of info.fixedURI against the Public Suffix List.
+ * If the suffix is unknown due to a typo this will try to fix it up.
+ * @param {URIFixupInfo} info about the uri to check.
+ * @note this may modify the public suffix of info.fixedURI.
+ * @returns {object} result The lookup result.
+ * @returns {string} result.suffix The public suffix if one can be identified.
+ * @returns {boolean} result.hasUnknownSuffix True when the suffix is not in the
+ *     Public Suffix List and it's not in knownSuffixes. False in the other cases.
+ */
+function checkAndFixPublicSuffix(info) {
+  let uri = info.fixedURI;
+  let asciiHost = uri?.asciiHost;
+  if (
+    !asciiHost ||
+    !asciiHost.includes(".") ||
+    asciiHost.endsWith(".") ||
+    isDomainKnown(asciiHost)
+  ) {
+    return { suffix: "", hasUnknownSuffix: false };
+  }
+
+  // Quick bailouts for most common cases, according to Alexa Top 1 million.
+  if (
+    /^\w/.test(asciiHost) &&
+    (asciiHost.endsWith(".com") ||
+      asciiHost.endsWith(".net") ||
+      asciiHost.endsWith(".org") ||
+      asciiHost.endsWith(".ru") ||
+      asciiHost.endsWith(".de"))
+  ) {
+    return {
+      suffix: asciiHost.substring(asciiHost.lastIndexOf(".") + 1),
+      hasUnknownSuffix: false,
+    };
+  }
+  try {
+    let suffix = Services.eTLD.getKnownPublicSuffix(uri);
+    if (suffix) {
+      return { suffix, hasUnknownSuffix: false };
+    }
+  } catch (ex) {
+    return { suffix: "", hasUnknownSuffix: false };
+  }
+  // Suffix is unknown, try to fix most common 3 chars TLDs typos.
+  // .com is the most commonly mistyped tld, so it has more cases.
+  let suffix = Services.eTLD.getPublicSuffix(uri);
+  if (!suffix || lazy.numberRegex.test(suffix)) {
+    return { suffix: "", hasUnknownSuffix: false };
+  }
+  for (let [typo, fixed] of [
+    ["ocm", "com"],
+    ["con", "com"],
+    ["cmo", "com"],
+    ["xom", "com"],
+    ["vom", "com"],
+    ["cpm", "com"],
+    ["com'", "com"],
+    ["ent", "net"],
+    ["ner", "net"],
+    ["nte", "net"],
+    ["met", "net"],
+    ["rog", "org"],
+    ["ogr", "org"],
+    ["prg", "org"],
+    ["orh", "org"],
+  ]) {
+    if (suffix == typo) {
+      let host = uri.host.substring(0, uri.host.length - typo.length) + fixed;
+      let updatePreferredURI = info.preferredURI == info.fixedURI;
+      info.fixedURI = uri.mutate().setHost(host).finalize();
+      if (updatePreferredURI) {
+        info.preferredURI = info.fixedURI;
+      }
+      return { suffix: fixed, hasUnknownSuffix: false };
+    }
+  }
+  return { suffix: "", hasUnknownSuffix: true };
+}
+
+function tryKeywordFixupForURIInfo(uriString, fixupInfo, isPrivateContext) {
+  try {
+    let keywordInfo = Services.uriFixup.keywordToURI(
+      uriString,
+      isPrivateContext
+    );
+    fixupInfo.keywordProviderName = keywordInfo.keywordProviderName;
+    fixupInfo.keywordAsSent = keywordInfo.keywordAsSent;
+    fixupInfo.preferredURI = keywordInfo.preferredURI;
+    return true;
+  } catch (ex) {}
+  return false;
+}
+
+/**
+ * This generates an alternate fixedURI, by adding a prefix and a suffix to
+ * the fixedURI host, if and only if the protocol is http. It should _never_
+ * modify URIs with other protocols.
+ * @param {URIFixupInfo} info an URIInfo object
+ * @param {integer} fixupFlags the fixup flags
+ * @returns {boolean} Whether an alternate uri was generated
+ */
+function maybeSetAlternateFixedURI(info, fixupFlags) {
+  let uri = info.fixedURI;
+  if (
+    !(fixupFlags & FIXUP_FLAGS_MAKE_ALTERNATE_URI) ||
+    // Code only works for http. Not for any other protocol including https!
+    !uri.schemeIs("http") ||
+    // Security - URLs with user / password info should NOT be fixed up
+    uri.userPass ||
+    // Don't fix up hosts with ports
+    uri.port != -1
+  ) {
+    return false;
+  }
+
+  let oldHost = uri.host;
+  // Don't create an alternate uri for localhost, because it would be confusing.
+  // Ditto for 'http' and 'https' as these are frequently the result of typos, e.g.
+  // 'https//foo' (note missing : ).
+  if (oldHost == "localhost" || oldHost == "http" || oldHost == "https") {
+    return false;
+  }
+
+  // Get the prefix and suffix to stick onto the new hostname. By default these
+  // are www. & .com but they could be any other value, e.g. www. & .org
+  let newHost = maybeAddPrefixAndSuffix(oldHost);
+
+  if (newHost == oldHost) {
+    return false;
+  }
+
+  return updateHostAndScheme(info, newHost);
+}
+
+/**
+ * Try to fixup a file URI.
+ * @param {string} uriString The file URI to fix.
+ * @returns {nsIURI} a fixed uri or null.
+ * @note FileURIFixup only returns a URI if it has to add the file: protocol.
+ */
+function fileURIFixup(uriString) {
+  let attemptFixup = false;
+  let path = uriString;
+  if (AppConstants.platform == "win") {
+    // Check for "\"" in the url-string, just a drive (e.g. C:),
+    // or 'A:/...' where the "protocol" is also a single letter.
+    attemptFixup =
+      uriString.includes("\\") ||
+      (uriString[1] == ":" && (uriString.length == 2 || uriString[2] == "/"));
+    if (uriString[1] == ":" && uriString[2] == "/") {
+      path = uriString.replace(/\//g, "\\");
+    }
+  } else {
+    // UNIX: Check if it starts with "/" or "~".
+    attemptFixup = /^[~/]/.test(uriString);
+  }
+  if (attemptFixup) {
+    try {
+      // Test if this is a valid path by trying to create a local file
+      // object. The URL of that is returned if successful.
+      let file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+      file.initWithPath(path);
+      return Services.io.newURI(
+        lazy.fileProtocolHandler.getURLSpecFromActualFile(file)
+      );
+    } catch (ex) {
+      // Not a file uri.
+    }
+  }
+  return null;
+}
+
+/**
+ * Tries to fixup a string to an nsIURI by adding the default protocol.
+ *
+ * Should fix things like:
+ *    no-scheme.com
+ *    ftp.no-scheme.com
+ *    ftp4.no-scheme.com
+ *    no-scheme.com/query?foo=http://www.foo.com
+ *    user:pass@no-scheme.com
+ *
+ * @param {string} uriString The string to fixup.
+ * @returns {nsIURI} an nsIURI built adding the default protocol to the string,
+ *          or null if fixing was not possible.
+ */
+function fixupURIProtocol(uriString) {
+  let schemePos = uriString.indexOf("://");
+  if (schemePos == -1 || schemePos > uriString.search(/[:\/]/)) {
+    uriString = "http://" + uriString;
+  }
+  try {
+    return Services.io.newURI(uriString);
+  } catch (ex) {
+    // We generated an invalid uri.
+  }
+  return null;
+}
+
+/**
+ * Tries to fixup a string to a search url.
+ * @param {string} uriString the string to fixup.
+ * @param {URIFixupInfo} fixupInfo The fixup info object, modified in-place.
+ * @param {boolean} isPrivateContext Whether this happens in a private context.
+ * @param {nsIInputStream} postData optional POST data for the search
+ * @returns {boolean} Whether the keyword fixup was succesful.
+ */
+function keywordURIFixup(uriString, fixupInfo, isPrivateContext) {
+  // Here is a few examples of strings that should be searched:
+  // "what is mozilla"
+  // "what is mozilla?"
+  // "docshell site:mozilla.org" - has a space in the origin part
+  // "?site:mozilla.org - anything that begins with a question mark
+  // "mozilla'.org" - Things that have a quote before the first dot/colon
+  // "mozilla/test" - unknown host
+  // ".mozilla", "mozilla." - starts or ends with a dot ()
+  // "user@nonQualifiedHost"
+
+  // These other strings should not be searched, because they could be URIs:
+  // "www.blah.com" - Domain with a standard or known suffix
+  // "knowndomain" - known domain
+  // "nonQualifiedHost:8888?something" - has a port
+  // "user:pass@nonQualifiedHost"
+  // "blah.com."
+
+  // We do keyword lookups if the input starts with a question mark.
+  if (uriString.startsWith("?")) {
+    return tryKeywordFixupForURIInfo(
+      fixupInfo.originalInput,
+      fixupInfo,
+      isPrivateContext
+    );
+  }
+
+  // Check for IPs.
+  const userPassword = lazy.userPasswordRegex.exec(uriString);
+  const ipString = userPassword
+    ? uriString.replace(userPassword[2], "")
+    : uriString;
+  if (lazy.IPv4LikeRegex.test(ipString) || lazy.IPv6LikeRegex.test(ipString)) {
+    return false;
+  }
+
+  // Avoid keyword lookup if we can identify a host and it's known, or ends
+  // with a dot and has some path.
+  // Note that if dnsFirstForSingleWords is true isDomainKnown will always
+  // return true, so we can avoid checking dnsFirstForSingleWords after this.
+  let asciiHost = fixupInfo.fixedURI?.asciiHost;
+  if (
+    asciiHost &&
+    (isDomainKnown(asciiHost) ||
+      (asciiHost.endsWith(".") &&
+        asciiHost.indexOf(".") != asciiHost.length - 1))
+  ) {
+    return false;
+  }
+
+  // Avoid keyword lookup if the url seems to have password.
+  if (fixupInfo.fixedURI?.password) {
+    return false;
+  }
+
+  // Even if the host is unknown, avoid keyword lookup if the string has
+  // uri-like characteristics, unless it looks like "user@unknownHost".
+  // Note we already excluded passwords at this point.
+  if (
+    !isURILike(uriString, fixupInfo.fixedURI?.displayHost) ||
+    (fixupInfo.fixedURI?.userPass && fixupInfo.fixedURI?.pathQueryRef === "/")
+  ) {
+    return tryKeywordFixupForURIInfo(
+      fixupInfo.originalInput,
+      fixupInfo,
+      isPrivateContext
+    );
+  }
+
+  return false;
+}
+
+/**
+ * Mimics the logic in Services.io.extractScheme, but avoids crossing XPConnect.
+ * This also tries to fixup the scheme if it was clearly mistyped.
+ * @param {string} uriString the string to examine
+ * @param {integer} fixupFlags The original fixup flags
+ * @returns {object}
+ *          scheme: a typo fixed scheme or empty string if one could not be identified
+ *          fixedSchemeUriString: uri string with a typo fixed scheme
+ *          fixupChangedProtocol: true if the scheme is fixed up
+ */
+function extractScheme(uriString, fixupFlags = FIXUP_FLAG_NONE) {
+  const matches = uriString.match(lazy.possibleProtocolRegex);
+  const hasColon = matches?.[2] === ":";
+  const hasSlash2 = matches?.[3] === "//";
+
+  const isFixupSchemeTypos =
+    lazy.fixupSchemeTypos && fixupFlags & FIXUP_FLAG_FIX_SCHEME_TYPOS;
+
+  if (
+    !matches ||
+    (!hasColon && !hasSlash2) ||
+    (!hasColon && !isFixupSchemeTypos)
+  ) {
+    return {
+      scheme: "",
+      fixedSchemeUriString: uriString,
+      fixupChangedProtocol: false,
+    };
+  }
+
+  let scheme = matches[1].replace("\t", "").toLowerCase();
+  let fixedSchemeUriString = uriString;
+
+  if (isFixupSchemeTypos && hasSlash2) {
+    // Fix up typos for string that user would have intented as protocol.
+    const afterProtocol = uriString.substring(matches[0].length);
+    fixedSchemeUriString = `${scheme}://${afterProtocol}`;
+  }
+
+  let fixupChangedProtocol = false;
+
+  if (isFixupSchemeTypos) {
+    // Fix up common scheme typos.
+    // TODO: Use levenshtein distance here?
+    fixupChangedProtocol = [
+      ["ttp", "http"],
+      ["htp", "http"],
+      ["ttps", "https"],
+      ["tps", "https"],
+      ["ps", "https"],
+      ["htps", "https"],
+      ["ile", "file"],
+      ["le", "file"],
+    ].some(([typo, fixed]) => {
+      if (scheme === typo) {
+        scheme = fixed;
+        fixedSchemeUriString =
+          scheme + fixedSchemeUriString.substring(typo.length);
+        return true;
+      }
+      return false;
+    });
+  }
+
+  return {
+    scheme,
+    fixedSchemeUriString,
+    fixupChangedProtocol,
+  };
+}
+
+/**
+ * View-source is a pseudo scheme. We're interested in fixing up the stuff
+ * after it. The easiest way to do that is to call this method again with
+ * the "view-source:" lopped off and then prepend it again afterwards.
+ * @param {string} uriString The original string to fixup
+ * @param {integer} fixupFlags The original fixup flags
+ * @param {nsIInputStream} postData Optional POST data for the search
+ * @returns {object} {preferredURI, postData} The fixed URI and relative postData
+ * @throws if it's not possible to fixup the url
+ */
+function fixupViewSource(uriString, fixupFlags) {
+  // We disable keyword lookup and alternate URIs so that small typos don't
+  // cause us to look at very different domains.
+  let newFixupFlags = fixupFlags & ~FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP;
+  let innerURIString = uriString.substring(12).trim();
+
+  // Prevent recursion.
+  const { scheme: innerScheme } = extractScheme(innerURIString);
+  if (innerScheme == "view-source") {
+    throw new Components.Exception(
+      "Prevent view-source recursion",
+      Cr.NS_ERROR_FAILURE
+    );
+  }
+
+  let info = Services.uriFixup.getFixupURIInfo(innerURIString, newFixupFlags);
+  if (!info.preferredURI) {
+    throw new Components.Exception(
+      "Couldn't build a valid uri",
+      Cr.NS_ERROR_MALFORMED_URI
+    );
+  }
+  return {
+    preferredURI: Services.io.newURI("view-source:" + info.preferredURI.spec),
+    postData: info.postData,
+  };
+}
+
+/**
+ * Fixup the host of fixedURI if it contains consecutive dots.
+ * @param {URIFixupInfo} info an URIInfo object
+ */
+function fixupConsecutiveDotsHost(fixupInfo) {
+  const uri = fixupInfo.fixedURI;
+
+  try {
+    if (!uri?.host.includes("..")) {
+      return;
+    }
+  } catch (e) {
+    return;
+  }
+
+  try {
+    const isPreferredEqualsToFixed = fixupInfo.preferredURI?.equals(uri);
+
+    fixupInfo.fixedURI = uri
+      .mutate()
+      .setHost(uri.host.replace(/\.+/g, "."))
+      .finalize();
+
+    if (isPreferredEqualsToFixed) {
+      fixupInfo.preferredURI = fixupInfo.fixedURI;
+    }
+  } catch (e) {
+    if (e.result !== Cr.NS_ERROR_MALFORMED_URI) {
+      throw e;
+    }
+  }
+}
+
+/**
+ * Return whether or not given string is uri like.
+ * This function returns true like following strings.
+ * - ":8080"
+ * - "localhost:8080" (if given host is "localhost")
+ * - "/foo?bar"
+ * - "/foo#bar"
+ * @param {string} uriString.
+ * @param {string} host.
+ * @param {boolean} true if uri like.
+ */
+function isURILike(uriString, host) {
+  const indexOfSlash = uriString.indexOf("/");
+  if (
+    indexOfSlash >= 0 &&
+    (indexOfSlash < uriString.indexOf("?", indexOfSlash) ||
+      indexOfSlash < uriString.indexOf("#", indexOfSlash))
+  ) {
+    return true;
+  }
+
+  if (uriString.startsWith(host)) {
+    uriString = uriString.substring(host.length);
+  }
+
+  return lazy.portRegex.test(uriString);
+}
+
+/**
+ * Add prefix and suffix to a hostname if both are missing.
+ *
+ * If the host does not start with the prefix, add the prefix to
+ * the hostname.
+ *
+ * By default the prefix and suffix are www. and .com but they could
+ * be any value e.g. www. and .org as they use the preferences
+ * "browser.fixup.alternate.prefix" and "browser.fixup.alternative.suffix"
+ *
+ * If no changes were made, it returns an empty string.
+ *
+ * @param {string} oldHost.
+ * @return {String} Fixed up hostname or an empty string.
+ */
+function maybeAddPrefixAndSuffix(oldHost) {
+  let prefix = Services.prefs.getCharPref(
+    "browser.fixup.alternate.prefix",
+    "www."
+  );
+  let suffix = Services.prefs.getCharPref(
+    "browser.fixup.alternate.suffix",
+    ".com"
+  );
+  let newHost = "";
+  let numDots = (oldHost.match(/\./g) || []).length;
+  if (numDots == 0) {
+    newHost = prefix + oldHost + suffix;
+  } else if (numDots == 1) {
+    if (prefix && oldHost == prefix) {
+      newHost = oldHost + suffix;
+    } else if (suffix && !oldHost.startsWith(prefix)) {
+      newHost = prefix + oldHost;
+    }
+  }
+  return newHost ? newHost : oldHost;
+}
+
+/**
+ * Given an instance of URIFixupInfo, update its fixedURI.
+ *
+ * First, change the protocol to the one stored in
+ * "browser.fixup.alternate.protocol".
+ *
+ * Then, try to update fixedURI's host to newHost.
+ *
+ * @param {URIFixupInfo} info.
+ * @param {string} newHost.
+ * @return {boolean}
+ *          True, if info was updated without any errors.
+ *          False, if NS_ERROR_MALFORMED_URI error.
+ * @throws If a non-NS_ERROR_MALFORMED_URI error occurs.
+ */
+function updateHostAndScheme(info, newHost) {
+  let oldHost = info.fixedURI.host;
+  let oldScheme = info.fixedURI.scheme;
+  try {
+    info.fixedURI = info.fixedURI
+      .mutate()
+      .setScheme(lazy.alternateProtocol)
+      .setHost(newHost)
+      .finalize();
+  } catch (ex) {
+    if (ex.result != Cr.NS_ERROR_MALFORMED_URI) {
+      throw ex;
+    }
+    return false;
+  }
+  if (oldScheme != info.fixedURI.scheme) {
+    info.fixupChangedProtocol = true;
+  }
+  if (oldHost != info.fixedURI.host) {
+    info.fixupCreatedAlternateURI = true;
+  }
+  return true;
+}
diff --git a/docshell/base/WindowContext.cpp b/docshell/base/WindowContext.cpp
new file mode 100644
index 0000000000..d2032bc551
--- /dev/null
+++ b/docshell/base/WindowContext.cpp
@@ -0,0 +1,697 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/WindowContext.h"
+#include "mozilla/dom/WindowGlobalActorsBinding.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/dom/SyncedContextInlines.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/UserActivationIPCUtils.h"
+#include "mozilla/PermissionDelegateIPCUtils.h"
+#include "mozilla/RFPTargetIPCUtils.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "nsGlobalWindowInner.h"
+#include "nsIScriptError.h"
+#include "nsIWebProgressListener.h"
+#include "nsIXULRuntime.h"
+#include "nsRefPtrHashtable.h"
+#include "nsContentUtils.h"
+
+namespace mozilla {
+namespace dom {
+
+// Explicit specialization of the `Transaction` type. Required by the `extern
+// template class` declaration in the header.
+template class syncedcontext::Transaction<WindowContext>;
+
+static LazyLogModule gWindowContextLog("WindowContext");
+static LazyLogModule gWindowContextSyncLog("WindowContextSync");
+
+extern mozilla::LazyLogModule gUserInteractionPRLog;
+
+#define USER_ACTIVATION_LOG(msg, ...) \
+  MOZ_LOG(gUserInteractionPRLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
+using WindowContextByIdMap = nsTHashMap<nsUint64HashKey, WindowContext*>;
+static StaticAutoPtr<WindowContextByIdMap> gWindowContexts;
+
+/* static */
+LogModule* WindowContext::GetLog() { return gWindowContextLog; }
+
+/* static */
+LogModule* WindowContext::GetSyncLog() { return gWindowContextSyncLog; }
+
+/* static */
+already_AddRefed<WindowContext> WindowContext::GetById(
+    uint64_t aInnerWindowId) {
+  if (!gWindowContexts) {
+    return nullptr;
+  }
+  return do_AddRef(gWindowContexts->Get(aInnerWindowId));
+}
+
+BrowsingContextGroup* WindowContext::Group() const {
+  return mBrowsingContext->Group();
+}
+
+WindowGlobalParent* WindowContext::Canonical() {
+  MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+  return static_cast<WindowGlobalParent*>(this);
+}
+
+bool WindowContext::IsCurrent() const {
+  return mBrowsingContext->mCurrentWindowContext == this;
+}
+
+bool WindowContext::IsInBFCache() {
+  if (mozilla::SessionHistoryInParent()) {
+    return mBrowsingContext->IsInBFCache();
+  }
+  return TopWindowContext()->GetWindowStateSaved();
+}
+
+nsGlobalWindowInner* WindowContext::GetInnerWindow() const {
+  return mWindowGlobalChild ? mWindowGlobalChild->GetWindowGlobal() : nullptr;
+}
+
+Document* WindowContext::GetDocument() const {
+  nsGlobalWindowInner* innerWindow = GetInnerWindow();
+  return innerWindow ? innerWindow->GetDocument() : nullptr;
+}
+
+Document* WindowContext::GetExtantDoc() const {
+  nsGlobalWindowInner* innerWindow = GetInnerWindow();
+  return innerWindow ? innerWindow->GetExtantDoc() : nullptr;
+}
+
+WindowGlobalChild* WindowContext::GetWindowGlobalChild() const {
+  return mWindowGlobalChild;
+}
+
+WindowContext* WindowContext::GetParentWindowContext() {
+  return mBrowsingContext->GetParentWindowContext();
+}
+
+WindowContext* WindowContext::TopWindowContext() {
+  WindowContext* current = this;
+  while (current->GetParentWindowContext()) {
+    current = current->GetParentWindowContext();
+  }
+  return current;
+}
+
+bool WindowContext::IsTop() const { return mBrowsingContext->IsTop(); }
+
+bool WindowContext::SameOriginWithTop() const {
+  return mBrowsingContext->SameOriginWithTop();
+}
+
+nsIGlobalObject* WindowContext::GetParentObject() const {
+  return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
+}
+
+void WindowContext::AppendChildBrowsingContext(
+    BrowsingContext* aBrowsingContext) {
+  MOZ_DIAGNOSTIC_ASSERT(Group() == aBrowsingContext->Group(),
+                        "Mismatched groups?");
+  MOZ_DIAGNOSTIC_ASSERT(!mChildren.Contains(aBrowsingContext));
+
+  mChildren.AppendElement(aBrowsingContext);
+  if (!aBrowsingContext->IsEmbedderTypeObjectOrEmbed()) {
+    mNonSyntheticChildren.AppendElement(aBrowsingContext);
+  }
+
+  // If we're the current WindowContext in our BrowsingContext, make sure to
+  // clear any cached `children` value.
+  if (IsCurrent()) {
+    BrowsingContext_Binding::ClearCachedChildrenValue(mBrowsingContext);
+  }
+}
+
+void WindowContext::RemoveChildBrowsingContext(
+    BrowsingContext* aBrowsingContext) {
+  MOZ_DIAGNOSTIC_ASSERT(Group() == aBrowsingContext->Group(),
+                        "Mismatched groups?");
+
+  mChildren.RemoveElement(aBrowsingContext);
+  mNonSyntheticChildren.RemoveElement(aBrowsingContext);
+
+  // If we're the current WindowContext in our BrowsingContext, make sure to
+  // clear any cached `children` value.
+  if (IsCurrent()) {
+    BrowsingContext_Binding::ClearCachedChildrenValue(mBrowsingContext);
+  }
+}
+
+void WindowContext::UpdateChildSynthetic(BrowsingContext* aBrowsingContext,
+                                         bool aIsSynthetic) {
+  if (aIsSynthetic) {
+    mNonSyntheticChildren.RemoveElement(aBrowsingContext);
+  } else {
+    // The same BrowsingContext will be reused for error pages, so it can be in
+    // the list already.
+    if (!mNonSyntheticChildren.Contains(aBrowsingContext)) {
+      mNonSyntheticChildren.AppendElement(aBrowsingContext);
+    }
+  }
+}
+
+void WindowContext::SendCommitTransaction(ContentParent* aParent,
+                                          const BaseTransaction& aTxn,
+                                          uint64_t aEpoch) {
+  Unused << aParent->SendCommitWindowContextTransaction(this, aTxn, aEpoch);
+}
+
+void WindowContext::SendCommitTransaction(ContentChild* aChild,
+                                          const BaseTransaction& aTxn,
+                                          uint64_t aEpoch) {
+  aChild->SendCommitWindowContextTransaction(this, aTxn, aEpoch);
+}
+
+bool WindowContext::CheckOnlyOwningProcessCanSet(ContentParent* aSource) {
+  if (IsInProcess()) {
+    return true;
+  }
+
+  if (XRE_IsParentProcess() && aSource) {
+    return Canonical()->GetContentParent() == aSource;
+  }
+
+  return false;
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsSecure>, const bool& aIsSecure,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_AllowMixedContent>,
+                           const bool& aAllowMixedContent,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_HasBeforeUnload>,
+                           const bool& aHasBeforeUnload,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_CookieBehavior>,
+                           const Maybe<uint32_t>& aValue,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsOnContentBlockingAllowList>,
+                           const bool& aValue, ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsThirdPartyWindow>,
+                           const bool& IsThirdPartyWindow,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsThirdPartyTrackingResourceWindow>,
+                           const bool& aIsThirdPartyTrackingResourceWindow,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_UsingStorageAccess>,
+                           const bool& aUsingStorageAccess,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_ShouldResistFingerprinting>,
+                           const bool& aShouldResistFingerprinting,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_OverriddenFingerprintingSettings>,
+                           const Maybe<RFPTarget>& aValue,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsSecureContext>,
+                           const bool& aIsSecureContext,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsOriginalFrameSource>,
+                           const bool& aIsOriginalFrameSource,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_DocTreeHadMedia>, const bool& aValue,
+                           ContentParent* aSource) {
+  return IsTop();
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_AutoplayPermission>,
+                           const uint32_t& aValue, ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_ShortcutsPermission>,
+                           const uint32_t& aValue, ContentParent* aSource) {
+  return IsTop() && CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_ActiveMediaSessionContextId>,
+                           const Maybe<uint64_t>& aValue,
+                           ContentParent* aSource) {
+  return IsTop();
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_PopupPermission>, const uint32_t&,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(
+    FieldIndex<IDX_DelegatedPermissions>,
+    const PermissionDelegateHandler::DelegatedPermissionList& aValue,
+    ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(
+    FieldIndex<IDX_DelegatedExactHostMatchPermissions>,
+    const PermissionDelegateHandler::DelegatedPermissionList& aValue,
+    ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_IsLocalIP>, const bool& aValue,
+                           ContentParent* aSource) {
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_AllowJavascript>, bool aValue,
+                           ContentParent* aSource) {
+  return (XRE_IsParentProcess() && !aSource) ||
+         CheckOnlyOwningProcessCanSet(aSource);
+}
+
+void WindowContext::DidSet(FieldIndex<IDX_AllowJavascript>, bool aOldValue) {
+  RecomputeCanExecuteScripts();
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_HasActivePeerConnections>, bool,
+                           ContentParent*) {
+  return XRE_IsParentProcess() && IsTop();
+}
+
+void WindowContext::RecomputeCanExecuteScripts(bool aApplyChanges) {
+  const bool old = mCanExecuteScripts;
+  if (!AllowJavascript()) {
+    // Scripting has been explicitly disabled on our WindowContext.
+    mCanExecuteScripts = false;
+  } else {
+    // Otherwise, inherit.
+    mCanExecuteScripts = mBrowsingContext->CanExecuteScripts();
+  }
+
+  if (aApplyChanges && old != mCanExecuteScripts) {
+    // Inform our active DOM window.
+    if (nsGlobalWindowInner* window = GetInnerWindow()) {
+      // Only update scriptability if the window is current. Windows will have
+      // scriptability disabled when entering the bfcache and updated when
+      // coming out.
+      if (window->IsCurrentInnerWindow()) {
+        auto& scriptability =
+            xpc::Scriptability::Get(window->GetGlobalJSObject());
+        scriptability.SetWindowAllowsScript(mCanExecuteScripts);
+      }
+    }
+
+    for (const RefPtr<BrowsingContext>& child : Children()) {
+      child->RecomputeCanExecuteScripts();
+    }
+  }
+}
+
+void WindowContext::DidSet(FieldIndex<IDX_SHEntryHasUserInteraction>,
+                           bool aOldValue) {
+  MOZ_ASSERT(
+      TopWindowContext() == this,
+      "SHEntryHasUserInteraction can only be set on the top window context");
+  // This field is set when the child notifies us of new user interaction, so we
+  // also set the currently active shentry in the parent as having interaction.
+  if (XRE_IsParentProcess() && mBrowsingContext) {
+    SessionHistoryEntry* activeEntry =
+        mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+    if (activeEntry && GetSHEntryHasUserInteraction()) {
+      activeEntry->SetHasUserInteraction(true);
+    }
+  }
+}
+
+void WindowContext::DidSet(FieldIndex<IDX_UserActivationStateAndModifiers>) {
+  MOZ_ASSERT_IF(!IsInProcess(), mUserGestureStart.IsNull());
+  USER_ACTIVATION_LOG("Set user gesture activation 0x%02" PRIu8
+                      " for %s browsing context 0x%08" PRIx64,
+                      GetUserActivationStateAndModifiers(),
+                      XRE_IsParentProcess() ? "Parent" : "Child", Id());
+  if (IsInProcess()) {
+    USER_ACTIVATION_LOG(
+        "Set user gesture start time for %s browsing context 0x%08" PRIx64,
+        XRE_IsParentProcess() ? "Parent" : "Child", Id());
+    if (GetUserActivationState() == UserActivation::State::FullActivated) {
+      mUserGestureStart = TimeStamp::Now();
+    } else if (GetUserActivationState() == UserActivation::State::None) {
+      mUserGestureStart = TimeStamp();
+    }
+  }
+}
+
+void WindowContext::DidSet(FieldIndex<IDX_HasReportedShadowDOMUsage>,
+                           bool aOldValue) {
+  if (!aOldValue && GetHasReportedShadowDOMUsage() && IsInProcess()) {
+    MOZ_ASSERT(TopWindowContext() == this);
+    if (mBrowsingContext) {
+      Document* topLevelDoc = mBrowsingContext->GetDocument();
+      if (topLevelDoc) {
+        nsAutoString uri;
+        Unused << topLevelDoc->GetDocumentURI(uri);
+        if (!uri.IsEmpty()) {
+          nsAutoString msg = u"Shadow DOM used in ["_ns + uri +
+                             u"] or in some of its subdocuments."_ns;
+          nsContentUtils::ReportToConsoleNonLocalized(
+              msg, nsIScriptError::infoFlag, "DOM"_ns, topLevelDoc);
+        }
+      }
+    }
+  }
+}
+
+bool WindowContext::CanSet(FieldIndex<IDX_WindowStateSaved>, bool aValue,
+                           ContentParent* aSource) {
+  return !mozilla::SessionHistoryInParent() && IsTop() &&
+         CheckOnlyOwningProcessCanSet(aSource);
+}
+
+void WindowContext::CreateFromIPC(IPCInitializer&& aInit) {
+  MOZ_RELEASE_ASSERT(XRE_IsContentProcess(),
+                     "Should be a WindowGlobalParent in the parent");
+
+  RefPtr<BrowsingContext> bc = BrowsingContext::Get(aInit.mBrowsingContextId);
+  MOZ_RELEASE_ASSERT(bc);
+
+  if (bc->IsDiscarded()) {
+    // If we have already closed our browsing context, the
+    // WindowGlobalChild actor is bound to be destroyed soon and it's
+    // safe to ignore creating the WindowContext.
+    return;
+  }
+
+  RefPtr<WindowContext> context = new WindowContext(
+      bc, aInit.mInnerWindowId, aInit.mOuterWindowId, std::move(aInit.mFields));
+  context->Init();
+}
+
+void WindowContext::Init() {
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("Registering 0x%" PRIx64 " (bc=0x%" PRIx64 ")", mInnerWindowId,
+           mBrowsingContext->Id()));
+
+  // Register the WindowContext in the `WindowContextByIdMap`.
+  if (!gWindowContexts) {
+    gWindowContexts = new WindowContextByIdMap();
+    ClearOnShutdown(&gWindowContexts);
+  }
+  auto& entry = gWindowContexts->LookupOrInsert(mInnerWindowId);
+  MOZ_RELEASE_ASSERT(!entry, "Duplicate WindowContext for ID!");
+  entry = this;
+
+  // Register this to the browsing context.
+  mBrowsingContext->RegisterWindowContext(this);
+  Group()->Register(this);
+}
+
+void WindowContext::Discard() {
+  MOZ_LOG(GetLog(), LogLevel::Debug,
+          ("Discarding 0x%" PRIx64 " (bc=0x%" PRIx64 ")", mInnerWindowId,
+           mBrowsingContext->Id()));
+  if (mIsDiscarded) {
+    return;
+  }
+
+  mIsDiscarded = true;
+  if (gWindowContexts) {
+    gWindowContexts->Remove(InnerWindowId());
+  }
+  mBrowsingContext->UnregisterWindowContext(this);
+  Group()->Unregister(this);
+}
+
+void WindowContext::AddSecurityState(uint32_t aStateFlags) {
+  MOZ_ASSERT(TopWindowContext() == this);
+  MOZ_ASSERT((aStateFlags &
+              (nsIWebProgressListener::STATE_LOADED_MIXED_DISPLAY_CONTENT |
+               nsIWebProgressListener::STATE_LOADED_MIXED_ACTIVE_CONTENT |
+               nsIWebProgressListener::STATE_BLOCKED_MIXED_DISPLAY_CONTENT |
+               nsIWebProgressListener::STATE_BLOCKED_MIXED_ACTIVE_CONTENT |
+               nsIWebProgressListener::STATE_HTTPS_ONLY_MODE_UPGRADED |
+               nsIWebProgressListener::STATE_HTTPS_ONLY_MODE_UPGRADE_FAILED |
+               nsIWebProgressListener::STATE_HTTPS_ONLY_MODE_UPGRADED_FIRST)) ==
+                 aStateFlags,
+             "Invalid flags specified!");
+
+  if (XRE_IsParentProcess()) {
+    Canonical()->AddSecurityState(aStateFlags);
+  } else {
+    ContentChild* child = ContentChild::GetSingleton();
+    child->SendAddSecurityState(this, aStateFlags);
+  }
+}
+
+void WindowContext::NotifyUserGestureActivation(
+    UserActivation::Modifiers
+        aModifiers /* = UserActivation::Modifiers::None() */) {
+  UserActivation::StateAndModifiers stateAndModifiers;
+  stateAndModifiers.SetState(UserActivation::State::FullActivated);
+  stateAndModifiers.SetModifiers(aModifiers);
+  Unused << SetUserActivationStateAndModifiers(stateAndModifiers.GetRawData());
+}
+
+void WindowContext::NotifyResetUserGestureActivation() {
+  UserActivation::StateAndModifiers stateAndModifiers;
+  stateAndModifiers.SetState(UserActivation::State::None);
+  Unused << SetUserActivationStateAndModifiers(stateAndModifiers.GetRawData());
+}
+
+bool WindowContext::HasBeenUserGestureActivated() {
+  return GetUserActivationState() != UserActivation::State::None;
+}
+
+const TimeStamp& WindowContext::GetUserGestureStart() const {
+  MOZ_ASSERT(IsInProcess());
+  return mUserGestureStart;
+}
+
+bool WindowContext::HasValidTransientUserGestureActivation() {
+  MOZ_ASSERT(IsInProcess());
+
+  if (GetUserActivationState() != UserActivation::State::FullActivated) {
+    // mUserGestureStart should be null if the document hasn't ever been
+    // activated by user gesture
+    MOZ_ASSERT_IF(GetUserActivationState() == UserActivation::State::None,
+                  mUserGestureStart.IsNull());
+    return false;
+  }
+
+  MOZ_ASSERT(!mUserGestureStart.IsNull(),
+             "mUserGestureStart shouldn't be null if the document has ever "
+             "been activated by user gesture");
+  TimeDuration timeout = TimeDuration::FromMilliseconds(
+      StaticPrefs::dom_user_activation_transient_timeout());
+
+  return timeout <= TimeDuration() ||
+         (TimeStamp::Now() - mUserGestureStart) <= timeout;
+}
+
+bool WindowContext::ConsumeTransientUserGestureActivation() {
+  MOZ_ASSERT(IsInProcess());
+  MOZ_ASSERT(IsCurrent());
+
+  if (!HasValidTransientUserGestureActivation()) {
+    return false;
+  }
+
+  BrowsingContext* top = mBrowsingContext->Top();
+  top->PreOrderWalk([&](BrowsingContext* aBrowsingContext) {
+    WindowContext* windowContext = aBrowsingContext->GetCurrentWindowContext();
+    if (windowContext && windowContext->GetUserActivationState() ==
+                             UserActivation::State::FullActivated) {
+      auto stateAndModifiers = UserActivation::StateAndModifiers(
+          GetUserActivationStateAndModifiers());
+      stateAndModifiers.SetState(UserActivation::State::HasBeenActivated);
+      Unused << windowContext->SetUserActivationStateAndModifiers(
+          stateAndModifiers.GetRawData());
+    }
+  });
+
+  return true;
+}
+
+bool WindowContext::GetTransientUserGestureActivationModifiers(
+    UserActivation::Modifiers* aModifiers) {
+  if (!HasValidTransientUserGestureActivation()) {
+    return false;
+  }
+
+  auto stateAndModifiers =
+      UserActivation::StateAndModifiers(GetUserActivationStateAndModifiers());
+  *aModifiers = stateAndModifiers.GetModifiers();
+  return true;
+}
+
+bool WindowContext::CanShowPopup() {
+  uint32_t permit = GetPopupPermission();
+  if (permit == nsIPermissionManager::ALLOW_ACTION) {
+    return true;
+  }
+  if (permit == nsIPermissionManager::DENY_ACTION) {
+    return false;
+  }
+
+  return !StaticPrefs::dom_disable_open_during_load();
+}
+
+void WindowContext::TransientSetHasActivePeerConnections() {
+  if (!IsTop()) {
+    return;
+  }
+
+  mFields.SetWithoutSyncing<IDX_HasActivePeerConnections>(true);
+}
+
+WindowContext::IPCInitializer WindowContext::GetIPCInitializer() {
+  IPCInitializer init;
+  init.mInnerWindowId = mInnerWindowId;
+  init.mOuterWindowId = mOuterWindowId;
+  init.mBrowsingContextId = mBrowsingContext->Id();
+  init.mFields = mFields.RawValues();
+  return init;
+}
+
+WindowContext::WindowContext(BrowsingContext* aBrowsingContext,
+                             uint64_t aInnerWindowId, uint64_t aOuterWindowId,
+                             FieldValues&& aInit)
+    : mFields(std::move(aInit)),
+      mInnerWindowId(aInnerWindowId),
+      mOuterWindowId(aOuterWindowId),
+      mBrowsingContext(aBrowsingContext) {
+  MOZ_ASSERT(mBrowsingContext);
+  MOZ_ASSERT(mInnerWindowId);
+  MOZ_ASSERT(mOuterWindowId);
+  RecomputeCanExecuteScripts(/* aApplyChanges */ false);
+}
+
+WindowContext::~WindowContext() {
+  if (gWindowContexts) {
+    gWindowContexts->Remove(InnerWindowId());
+  }
+}
+
+JSObject* WindowContext::WrapObject(JSContext* cx,
+                                    JS::Handle<JSObject*> aGivenProto) {
+  return WindowContext_Binding::Wrap(cx, this, aGivenProto);
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(WindowContext)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(WindowContext)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(WindowContext)
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(WindowContext)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(WindowContext)
+  if (gWindowContexts) {
+    gWindowContexts->Remove(tmp->InnerWindowId());
+  }
+
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mBrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mChildren)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mNonSyntheticChildren)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(WindowContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mBrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mChildren)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mNonSyntheticChildren)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+}  // namespace dom
+
+namespace ipc {
+
+void IPDLParamTraits<dom::MaybeDiscarded<dom::WindowContext>>::Write(
+    IPC::MessageWriter* aWriter, IProtocol* aActor,
+    const dom::MaybeDiscarded<dom::WindowContext>& aParam) {
+  uint64_t id = aParam.ContextId();
+  WriteIPDLParam(aWriter, aActor, id);
+}
+
+bool IPDLParamTraits<dom::MaybeDiscarded<dom::WindowContext>>::Read(
+    IPC::MessageReader* aReader, IProtocol* aActor,
+    dom::MaybeDiscarded<dom::WindowContext>* aResult) {
+  uint64_t id = 0;
+  if (!ReadIPDLParam(aReader, aActor, &id)) {
+    return false;
+  }
+
+  if (id == 0) {
+    *aResult = nullptr;
+  } else if (RefPtr<dom::WindowContext> wc = dom::WindowContext::GetById(id)) {
+    *aResult = std::move(wc);
+  } else {
+    aResult->SetDiscarded(id);
+  }
+  return true;
+}
+
+void IPDLParamTraits<dom::WindowContext::IPCInitializer>::Write(
+    IPC::MessageWriter* aWriter, IProtocol* aActor,
+    const dom::WindowContext::IPCInitializer& aInit) {
+  // Write actor ID parameters.
+  WriteIPDLParam(aWriter, aActor, aInit.mInnerWindowId);
+  WriteIPDLParam(aWriter, aActor, aInit.mOuterWindowId);
+  WriteIPDLParam(aWriter, aActor, aInit.mBrowsingContextId);
+  WriteIPDLParam(aWriter, aActor, aInit.mFields);
+}
+
+bool IPDLParamTraits<dom::WindowContext::IPCInitializer>::Read(
+    IPC::MessageReader* aReader, IProtocol* aActor,
+    dom::WindowContext::IPCInitializer* aInit) {
+  // Read actor ID parameters.
+  return ReadIPDLParam(aReader, aActor, &aInit->mInnerWindowId) &&
+         ReadIPDLParam(aReader, aActor, &aInit->mOuterWindowId) &&
+         ReadIPDLParam(aReader, aActor, &aInit->mBrowsingContextId) &&
+         ReadIPDLParam(aReader, aActor, &aInit->mFields);
+}
+
+template struct IPDLParamTraits<dom::WindowContext::BaseTransaction>;
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/docshell/base/WindowContext.h b/docshell/base/WindowContext.h
new file mode 100644
index 0000000000..fda4030045
--- /dev/null
+++ b/docshell/base/WindowContext.h
@@ -0,0 +1,429 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_WindowContext_h
+#define mozilla_dom_WindowContext_h
+
+#include "mozilla/PermissionDelegateHandler.h"
+#include "mozilla/WeakPtr.h"
+#include "mozilla/Span.h"
+#include "mozilla/dom/MaybeDiscarded.h"
+#include "mozilla/dom/SyncedContext.h"
+#include "mozilla/dom/UserActivation.h"
+#include "nsDOMNavigationTiming.h"
+#include "nsILoadInfo.h"
+#include "nsWrapperCache.h"
+
+class nsIGlobalObject;
+
+class nsGlobalWindowInner;
+
+namespace mozilla {
+class LogModule;
+
+namespace dom {
+
+class WindowGlobalChild;
+class WindowGlobalParent;
+class WindowGlobalInit;
+class BrowsingContext;
+class BrowsingContextGroup;
+
+#define MOZ_EACH_WC_FIELD(FIELD)                                         \
+  /* Whether the SHEntry associated with the current top-level           \
+   * window has already seen user interaction.                           \
+   * As such, this will be reset to false when a new SHEntry is          \
+   * created without changing the WC (e.g. when using pushState or       \
+   * sub-frame navigation)                                               \
+   * This flag is set for optimization purposes, to avoid                \
+   * having to get the top SHEntry and update it on every                \
+   * user interaction.                                                   \
+   * This is only meaningful on the top-level WC. */                     \
+  FIELD(SHEntryHasUserInteraction, bool)                                 \
+  FIELD(CookieBehavior, Maybe<uint32_t>)                                 \
+  FIELD(IsOnContentBlockingAllowList, bool)                              \
+  /* Whether the given window hierarchy is third party. See              \
+   * ThirdPartyUtil::IsThirdPartyWindow for details */                   \
+  FIELD(IsThirdPartyWindow, bool)                                        \
+  /* Whether this window's channel has been marked as a third-party      \
+   * tracking resource */                                                \
+  FIELD(IsThirdPartyTrackingResourceWindow, bool)                        \
+  /* Whether this window is using its unpartitioned cookies due to       \
+   * the Storage Access API */                                           \
+  FIELD(UsingStorageAccess, bool)                                        \
+  FIELD(ShouldResistFingerprinting, bool)                                \
+  FIELD(OverriddenFingerprintingSettings, Maybe<RFPTarget>)              \
+  FIELD(IsSecureContext, bool)                                           \
+  FIELD(IsOriginalFrameSource, bool)                                     \
+  /* Mixed-Content: If the corresponding documentURI is https,           \
+   * then this flag is true. */                                          \
+  FIELD(IsSecure, bool)                                                  \
+  /* Whether the user has overriden the mixed content blocker to allow   \
+   * mixed content loads to happen */                                    \
+  FIELD(AllowMixedContent, bool)                                         \
+  /* Whether this window has registered a "beforeunload" event           \
+   * handler */                                                          \
+  FIELD(HasBeforeUnload, bool)                                           \
+  /* Controls whether the WindowContext is currently considered to be    \
+   * activated by a gesture */                                           \
+  FIELD(UserActivationStateAndModifiers,                                 \
+        UserActivation::StateAndModifiers::DataT)                        \
+  FIELD(EmbedderPolicy, nsILoadInfo::CrossOriginEmbedderPolicy)          \
+  /* True if this document tree contained at least a HTMLMediaElement.   \
+   * This should only be set on top level context. */                    \
+  FIELD(DocTreeHadMedia, bool)                                           \
+  FIELD(AutoplayPermission, uint32_t)                                    \
+  FIELD(ShortcutsPermission, uint32_t)                                   \
+  /* Store the Id of the browsing context where active media session     \
+   * exists on the top level window context */                           \
+  FIELD(ActiveMediaSessionContextId, Maybe<uint64_t>)                    \
+  /* ALLOW_ACTION if it is allowed to open popups for the sub-tree       \
+   * starting and including the current WindowContext */                 \
+  FIELD(PopupPermission, uint32_t)                                       \
+  FIELD(DelegatedPermissions,                                            \
+        PermissionDelegateHandler::DelegatedPermissionList)              \
+  FIELD(DelegatedExactHostMatchPermissions,                              \
+        PermissionDelegateHandler::DelegatedPermissionList)              \
+  FIELD(HasReportedShadowDOMUsage, bool)                                 \
+  /* Whether the principal of this window is for a local                 \
+   * IP address */                                                       \
+  FIELD(IsLocalIP, bool)                                                 \
+  /* Whether any of the windows in the subtree rooted at this window has \
+   * active peer connections or not (only set on the top window). */     \
+  FIELD(HasActivePeerConnections, bool)                                  \
+  /* Whether we can execute scripts in this WindowContext. Has no effect \
+   * unless scripts are also allowed in the BrowsingContext. */          \
+  FIELD(AllowJavascript, bool)                                           \
+  /* If this field is `true`, it means that this WindowContext's         \
+   * WindowState was saved to be stored in the legacy (non-SHIP) BFCache \
+   * implementation. Always false for SHIP */                            \
+  FIELD(WindowStateSaved, bool)
+
+class WindowContext : public nsISupports, public nsWrapperCache {
+  MOZ_DECL_SYNCED_CONTEXT(WindowContext, MOZ_EACH_WC_FIELD)
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(WindowContext)
+
+ public:
+  static already_AddRefed<WindowContext> GetById(uint64_t aInnerWindowId);
+  static LogModule* GetLog();
+  static LogModule* GetSyncLog();
+
+  BrowsingContext* GetBrowsingContext() const { return mBrowsingContext; }
+  BrowsingContextGroup* Group() const;
+  uint64_t Id() const { return InnerWindowId(); }
+  uint64_t InnerWindowId() const { return mInnerWindowId; }
+  uint64_t OuterWindowId() const { return mOuterWindowId; }
+  bool IsDiscarded() const { return mIsDiscarded; }
+
+  // Returns `true` if this WindowContext is the current WindowContext in its
+  // BrowsingContext.
+  bool IsCurrent() const;
+
+  // Returns `true` if this WindowContext is currently in the BFCache.
+  bool IsInBFCache();
+
+  bool IsInProcess() const { return mIsInProcess; }
+
+  bool HasBeforeUnload() const { return GetHasBeforeUnload(); }
+
+  bool IsLocalIP() const { return GetIsLocalIP(); }
+
+  bool ShouldResistFingerprinting() const {
+    return GetShouldResistFingerprinting();
+  }
+
+  Nullable<uint64_t> GetOverriddenFingerprintingSettingsWebIDL() const {
+    Maybe<RFPTarget> overriddenFingerprintingSettings =
+        GetOverriddenFingerprintingSettings();
+
+    return overriddenFingerprintingSettings.isSome()
+               ? Nullable<uint64_t>(
+                     uint64_t(overriddenFingerprintingSettings.ref()))
+               : Nullable<uint64_t>();
+  }
+
+  nsGlobalWindowInner* GetInnerWindow() const;
+  Document* GetDocument() const;
+  Document* GetExtantDoc() const;
+
+  WindowGlobalChild* GetWindowGlobalChild() const;
+
+  // Get the parent WindowContext of this WindowContext, taking the BFCache into
+  // account. This will not cross chrome/content <browser> boundaries.
+  WindowContext* GetParentWindowContext();
+  WindowContext* TopWindowContext();
+
+  bool SameOriginWithTop() const;
+
+  bool IsTop() const;
+
+  Span<RefPtr<BrowsingContext>> Children() { return mChildren; }
+
+  // The filtered version of `Children()`, which contains no browsing contexts
+  // for synthetic documents as created by object loading content.
+  Span<RefPtr<BrowsingContext>> NonSyntheticChildren() {
+    return mNonSyntheticChildren;
+  }
+
+  // Cast this object to it's parent-process canonical form.
+  WindowGlobalParent* Canonical();
+
+  nsIGlobalObject* GetParentObject() const;
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  void Discard();
+
+  struct IPCInitializer {
+    uint64_t mInnerWindowId;
+    uint64_t mOuterWindowId;
+    uint64_t mBrowsingContextId;
+
+    FieldValues mFields;
+  };
+  IPCInitializer GetIPCInitializer();
+
+  static void CreateFromIPC(IPCInitializer&& aInit);
+
+  // Add new security state flags.
+  // These should be some of the nsIWebProgressListener 'HTTPS_ONLY_MODE' or
+  // 'MIXED' state flags, and should only be called on the top window context.
+  void AddSecurityState(uint32_t aStateFlags);
+
+  UserActivation::State GetUserActivationState() const {
+    return UserActivation::StateAndModifiers(
+               GetUserActivationStateAndModifiers())
+        .GetState();
+  }
+
+  // This function would be called when its corresponding window is activated
+  // by user gesture.
+  void NotifyUserGestureActivation(
+      UserActivation::Modifiers aModifiers = UserActivation::Modifiers::None());
+
+  // This function would be called when we want to reset the user gesture
+  // activation flag.
+  void NotifyResetUserGestureActivation();
+
+  // Return true if its corresponding window has been activated by user
+  // gesture.
+  bool HasBeenUserGestureActivated();
+
+  // Return true if its corresponding window has transient user gesture
+  // activation and the transient user gesture activation haven't yet timed
+  // out.
+  bool HasValidTransientUserGestureActivation();
+
+  // See `mUserGestureStart`.
+  const TimeStamp& GetUserGestureStart() const;
+
+  // Return true if the corresponding window has valid transient user gesture
+  // activation and the transient user gesture activation had been consumed
+  // successfully.
+  bool ConsumeTransientUserGestureActivation();
+
+  bool GetTransientUserGestureActivationModifiers(
+      UserActivation::Modifiers* aModifiers);
+
+  bool CanShowPopup();
+
+  bool AllowJavascript() const { return GetAllowJavascript(); }
+  bool CanExecuteScripts() const { return mCanExecuteScripts; }
+
+  void TransientSetHasActivePeerConnections();
+
+ protected:
+  WindowContext(BrowsingContext* aBrowsingContext, uint64_t aInnerWindowId,
+                uint64_t aOuterWindowId, FieldValues&& aFields);
+  virtual ~WindowContext();
+
+  virtual void Init();
+
+ private:
+  friend class BrowsingContext;
+  friend class WindowGlobalChild;
+  friend class WindowGlobalActor;
+
+  void AppendChildBrowsingContext(BrowsingContext* aBrowsingContext);
+  void RemoveChildBrowsingContext(BrowsingContext* aBrowsingContext);
+
+  // Update non-synthetic children based on whether `aBrowsingContext`
+  // is synthetic or not. Regardless the synthetic of `aBrowsingContext`, it is
+  // kept in this WindowContext's all children list.
+  void UpdateChildSynthetic(BrowsingContext* aBrowsingContext,
+                            bool aIsSynthetic);
+
+  // Send a given `BaseTransaction` object to the correct remote.
+  void SendCommitTransaction(ContentParent* aParent,
+                             const BaseTransaction& aTxn, uint64_t aEpoch);
+  void SendCommitTransaction(ContentChild* aChild, const BaseTransaction& aTxn,
+                             uint64_t aEpoch);
+
+  bool CheckOnlyOwningProcessCanSet(ContentParent* aSource);
+
+  // Overload `CanSet` to get notifications for a particular field being set.
+  bool CanSet(FieldIndex<IDX_IsSecure>, const bool& aIsSecure,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_AllowMixedContent>, const bool& aAllowMixedContent,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_HasBeforeUnload>, const bool& aHasBeforeUnload,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_CookieBehavior>, const Maybe<uint32_t>& aValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_IsOnContentBlockingAllowList>, const bool& aValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_EmbedderPolicy>, const bool& aValue,
+              ContentParent* aSource) {
+    return true;
+  }
+
+  bool CanSet(FieldIndex<IDX_IsThirdPartyWindow>,
+              const bool& IsThirdPartyWindow, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_IsThirdPartyTrackingResourceWindow>,
+              const bool& aIsThirdPartyTrackingResourceWindow,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_UsingStorageAccess>,
+              const bool& aUsingStorageAccess, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_ShouldResistFingerprinting>,
+              const bool& aShouldResistFingerprinting, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_OverriddenFingerprintingSettings>,
+              const Maybe<RFPTarget>& aValue, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_IsSecureContext>, const bool& aIsSecureContext,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_IsOriginalFrameSource>,
+              const bool& aIsOriginalFrameSource, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_DocTreeHadMedia>, const bool& aValue,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_AutoplayPermission>, const uint32_t& aValue,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_ShortcutsPermission>, const uint32_t& aValue,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_ActiveMediaSessionContextId>,
+              const Maybe<uint64_t>& aValue, ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_PopupPermission>, const uint32_t&,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_SHEntryHasUserInteraction>,
+              const bool& aSHEntryHasUserInteraction, ContentParent* aSource) {
+    return true;
+  }
+  bool CanSet(FieldIndex<IDX_DelegatedPermissions>,
+              const PermissionDelegateHandler::DelegatedPermissionList& aValue,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_DelegatedExactHostMatchPermissions>,
+              const PermissionDelegateHandler::DelegatedPermissionList& aValue,
+              ContentParent* aSource);
+  bool CanSet(FieldIndex<IDX_UserActivationStateAndModifiers>,
+              const UserActivation::StateAndModifiers::DataT&
+                  aUserActivationStateAndModifiers,
+              ContentParent* aSource) {
+    return true;
+  }
+
+  bool CanSet(FieldIndex<IDX_HasReportedShadowDOMUsage>, const bool& aValue,
+              ContentParent* aSource) {
+    return true;
+  }
+
+  bool CanSet(FieldIndex<IDX_IsLocalIP>, const bool& aValue,
+              ContentParent* aSource);
+
+  bool CanSet(FieldIndex<IDX_AllowJavascript>, bool aValue,
+              ContentParent* aSource);
+  void DidSet(FieldIndex<IDX_AllowJavascript>, bool aOldValue);
+
+  bool CanSet(FieldIndex<IDX_HasActivePeerConnections>, bool, ContentParent*);
+
+  void DidSet(FieldIndex<IDX_HasReportedShadowDOMUsage>, bool aOldValue);
+
+  void DidSet(FieldIndex<IDX_SHEntryHasUserInteraction>, bool aOldValue);
+
+  bool CanSet(FieldIndex<IDX_WindowStateSaved>, bool aValue,
+              ContentParent* aSource);
+
+  // Overload `DidSet` to get notifications for a particular field being set.
+  //
+  // You can also overload the variant that gets the old value if you need it.
+  template <size_t I>
+  void DidSet(FieldIndex<I>) {}
+  template <size_t I, typename T>
+  void DidSet(FieldIndex<I>, T&& aOldValue) {}
+  void DidSet(FieldIndex<IDX_UserActivationStateAndModifiers>);
+
+  // Recomputes whether we can execute scripts in this WindowContext based on
+  // the value of AllowJavascript() and whether scripts are allowed in the
+  // BrowsingContext.
+  void RecomputeCanExecuteScripts(bool aApplyChanges = true);
+
+  const uint64_t mInnerWindowId;
+  const uint64_t mOuterWindowId;
+  RefPtr<BrowsingContext> mBrowsingContext;
+  WeakPtr<WindowGlobalChild> mWindowGlobalChild;
+
+  // --- NEVER CHANGE `mChildren` DIRECTLY! ---
+  // Changes to this list need to be synchronized to the list within our
+  // `mBrowsingContext`, and should only be performed through the
+  // `AppendChildBrowsingContext` and `RemoveChildBrowsingContext` methods.
+  nsTArray<RefPtr<BrowsingContext>> mChildren;
+
+  // --- NEVER CHANGE `mNonSyntheticChildren` DIRECTLY! ---
+  // Same reason as for mChildren.
+  // mNonSyntheticChildren contains the same browsing contexts except browsing
+  // contexts created by the synthetic document for object loading contents
+  // loading images. This is used to discern browsing contexts created when
+  // loading images in <object> or <embed> elements, so that they can be hidden
+  // from named targeting, `Window.frames` etc.
+  nsTArray<RefPtr<BrowsingContext>> mNonSyntheticChildren;
+
+  bool mIsDiscarded = false;
+  bool mIsInProcess = false;
+
+  // Determines if we can execute scripts in this WindowContext. True if
+  // AllowJavascript() is true and script execution is allowed in the
+  // BrowsingContext.
+  bool mCanExecuteScripts = true;
+
+  // The start time of user gesture, this is only available if the window
+  // context is in process.
+  TimeStamp mUserGestureStart;
+};
+
+using WindowContextTransaction = WindowContext::BaseTransaction;
+using WindowContextInitializer = WindowContext::IPCInitializer;
+using MaybeDiscardedWindowContext = MaybeDiscarded<WindowContext>;
+
+// Don't specialize the `Transaction` object for every translation unit it's
+// used in. This should help keep code size down.
+extern template class syncedcontext::Transaction<WindowContext>;
+
+}  // namespace dom
+
+namespace ipc {
+template <>
+struct IPDLParamTraits<dom::MaybeDiscarded<dom::WindowContext>> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const dom::MaybeDiscarded<dom::WindowContext>& aParam);
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   dom::MaybeDiscarded<dom::WindowContext>* aResult);
+};
+
+template <>
+struct IPDLParamTraits<dom::WindowContext::IPCInitializer> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const dom::WindowContext::IPCInitializer& aInitializer);
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   dom::WindowContext::IPCInitializer* aInitializer);
+};
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // !defined(mozilla_dom_WindowContext_h)
diff --git a/docshell/base/crashtests/1257730-1.html b/docshell/base/crashtests/1257730-1.html
new file mode 100644
index 0000000000..028a1adb88
--- /dev/null
+++ b/docshell/base/crashtests/1257730-1.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="UTF-8">
+<!--
+user_pref("browser.send_pings", true);
+-->
+<script>
+
+function boom() {
+  var aLink = document.createElement('a');
+  document.body.appendChild(aLink);
+  aLink.ping = "ping";
+  aLink.href = "href";
+  aLink.click();
+
+  var baseElement = document.createElement('base');
+  baseElement.setAttribute("href", "javascript:void 0");
+  document.head.appendChild(baseElement);
+}
+
+</script>
+</head>
+<body onload="boom();"></body>
+</html>
diff --git a/docshell/base/crashtests/1331295.html b/docshell/base/crashtests/1331295.html
new file mode 100644
index 0000000000..cdcb29e7fe
--- /dev/null
+++ b/docshell/base/crashtests/1331295.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="UTF-8">
+<script>
+function boom() {
+  setTimeout(function(){
+    var o=document.getElementById('b');
+    document.getElementById('a').appendChild(o.parentNode.removeChild(o));
+  },0);
+  var o=document.getElementById('c');
+  var p=document.getElementById('b');
+  p.id=[o.id, o.id=p.id][0];
+  o=document.getElementById('b');
+  o.setAttribute('sandbox', 'disc');
+  window.location.reload(true);
+}
+</script>
+</head>
+<body onload="boom();">
+<header id='a'></header>
+<output id='b'></output>
+<iframe id='c' sandbox='allow-same-origin' src='http://a'></iframe>
+</body>
+</html>
diff --git a/docshell/base/crashtests/1341657.html b/docshell/base/crashtests/1341657.html
new file mode 100644
index 0000000000..d68fa1eb03
--- /dev/null
+++ b/docshell/base/crashtests/1341657.html
@@ -0,0 +1,18 @@
+<html class="reftest-wait">
+    <head>
+        <script>
+          function boom() {
+            o1 = document.createElement("script");
+            o2 = document.implementation.createDocument('', '', null);
+            o3 = document.createElement("iframe");
+            document.documentElement.appendChild(o3);
+            o4 = o3.contentWindow;
+            o5 = document.createTextNode('o2.adoptNode(o3); try { o4.location = "" } catch(e) {}');
+            o1.appendChild(o5);
+            document.documentElement.appendChild(o1);
+            document.documentElement.classList.remove("reftest-wait");
+          }
+        </script>
+    </head>
+    <body onload="boom();"></body>
+</html>
diff --git a/docshell/base/crashtests/1584467.html b/docshell/base/crashtests/1584467.html
new file mode 100644
index 0000000000..5509808bcc
--- /dev/null
+++ b/docshell/base/crashtests/1584467.html
@@ -0,0 +1,12 @@
+<script>
+window.onload = () => {
+  a.addEventListener("DOMSubtreeModified", () => {
+    document.body.appendChild(b)
+    document.body.removeChild(b)
+    window[1]
+  })
+  a.type = ""
+}
+</script>
+<embed id="a">
+<iframe id="b"></iframe>
diff --git a/docshell/base/crashtests/1614211-1.html b/docshell/base/crashtests/1614211-1.html
new file mode 100644
index 0000000000..1d683e0714
--- /dev/null
+++ b/docshell/base/crashtests/1614211-1.html
@@ -0,0 +1,15 @@
+<script>
+window.onload = () => {
+  b.addEventListener('DOMSubtreeModified', () => {
+    var o = document.getElementById('a')
+    var a = o.attributes
+    for (let j = 0; j < a.length; j++) {
+      o.setAttribute(a[j].name, 'i')
+      o.parentNode.appendChild(o)
+    }
+  })
+  b.setAttribute('a', b)
+}
+</script>
+<iframe id='a' sandbox='' allowfullscreen=''></iframe>
+<dfn id='b'>
diff --git a/docshell/base/crashtests/1617315-1.html b/docshell/base/crashtests/1617315-1.html
new file mode 100644
index 0000000000..05d9a704dc
--- /dev/null
+++ b/docshell/base/crashtests/1617315-1.html
@@ -0,0 +1,8 @@
+<script>
+document.addEventListener("DOMContentLoaded", () => {
+  let o = document.getElementById('a')
+  o.setAttribute('id', '')
+  o.setAttribute('sandbox', '')
+})
+</script>
+<iframe id='a' sandbox='s' src='http://%CF'></iframe>
diff --git a/docshell/base/crashtests/1667491.html b/docshell/base/crashtests/1667491.html
new file mode 100644
index 0000000000..ecc77a5e9b
--- /dev/null
+++ b/docshell/base/crashtests/1667491.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+  <meta charset="UTF-8">
+<script>
+  function go() {
+    let win = window.open("1667491_1.html");
+    win.finish = function() {
+      document.documentElement.removeAttribute("class");
+    };
+  }
+</script>
+</head>
+<body onload="go()">
+</body>
+</html>
diff --git a/docshell/base/crashtests/1667491_1.html b/docshell/base/crashtests/1667491_1.html
new file mode 100644
index 0000000000..3df3353f72
--- /dev/null
+++ b/docshell/base/crashtests/1667491_1.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="UTF-8">
+  <script>
+  function go() {
+    document.body.appendChild(a)
+    window.frames[0].onbeforeunload = document.createElement("body").onload;
+    window.requestIdleCallback(() => {
+      window.close();
+      finish();
+    });
+  }
+  </script>
+</head>
+<body onload="go()">
+<iframe id="a"></iframe>
+<iframe></iframe>
+</body>
+</html>
+
diff --git a/docshell/base/crashtests/1672873.html b/docshell/base/crashtests/1672873.html
new file mode 100644
index 0000000000..33aa92f0ef
--- /dev/null
+++ b/docshell/base/crashtests/1672873.html
@@ -0,0 +1,6 @@
+<script>
+document.addEventListener('DOMContentLoaded', () => {
+  var x = new Blob([undefined, ''], { })
+  self.history.pushState(x, 'x', 'missing.file')
+})
+</script>
diff --git a/docshell/base/crashtests/1690169-1.html b/docshell/base/crashtests/1690169-1.html
new file mode 100644
index 0000000000..6c9be20be3
--- /dev/null
+++ b/docshell/base/crashtests/1690169-1.html
@@ -0,0 +1,11 @@
+<script>
+var woff = "data:font/woff2;base64,";
+for (let i = 0; i < 20000; i++) {
+	woff += "d09GMgABAAAA";
+}
+window.onload = () => {
+    try { window.open('data:text/html,<spacer>', 'pu9', 'width=911').close() } catch (e) {}
+    document.getElementById('a').setAttribute('src', woff)
+}
+</script>
+<iframe id='a' hidden src='http://a'></iframe>
diff --git a/docshell/base/crashtests/1753136.html b/docshell/base/crashtests/1753136.html
new file mode 100644
index 0000000000..22f679309e
--- /dev/null
+++ b/docshell/base/crashtests/1753136.html
@@ -0,0 +1,2 @@
+<meta charset="UTF-8">
+<iframe sandbox='' src='http://🙅🎂งิ'></iframe>
diff --git a/docshell/base/crashtests/1804803.html b/docshell/base/crashtests/1804803.html
new file mode 100644
index 0000000000..5103c00416
--- /dev/null
+++ b/docshell/base/crashtests/1804803.html
@@ -0,0 +1,13 @@
+<html class="reftest-wait">
+<script>
+function test() {
+  // If the reload in the iframe succeeds we might crash, so wait for it.
+  setTimeout(function() {
+    document.documentElement.className = "";
+  }, 500);
+}
+</script>
+<body onload="test()">
+    <iframe src="1804803.sjs"></iframe>
+</body>
+</html>
diff --git a/docshell/base/crashtests/1804803.sjs b/docshell/base/crashtests/1804803.sjs
new file mode 100644
index 0000000000..0486e32048
--- /dev/null
+++ b/docshell/base/crashtests/1804803.sjs
@@ -0,0 +1,18 @@
+function handleRequest(request, response) {
+  let counter = Number(getState("load"));
+  const reload = counter == 0 ? "self.history.go(0);" : "";
+  setState("load", String(++counter));
+  const document = `
+<script>
+    document.addEventListener('DOMContentLoaded', () => {
+      ${reload}
+      let url = window.location.href;
+      for (let i = 0; i < 50; i++) {
+        self.history.pushState({x: i}, '', url + "#" + i);
+      }
+    });
+</script>
+`;
+
+  response.write(document);
+}
diff --git a/docshell/base/crashtests/369126-1.html b/docshell/base/crashtests/369126-1.html
new file mode 100644
index 0000000000..e9dacec301
--- /dev/null
+++ b/docshell/base/crashtests/369126-1.html
@@ -0,0 +1,16 @@
+<html class="reftest-wait">
+<head>
+<script>
+function boom()
+{
+  document.getElementById("frameset").removeChild(document.getElementById("frame"));
+  document.documentElement.removeAttribute("class");
+}
+</script>
+</head>
+
+<frameset id="frameset" onload="setTimeout(boom, 100)">
+  <frame id="frame" src="data:text/html,<body onUnload=&quot;location = 'http://www.mozilla.org/'&quot;>This frame's onunload tries to load another page.">
+</frameset>
+
+</html>
diff --git a/docshell/base/crashtests/40929-1-inner.html b/docshell/base/crashtests/40929-1-inner.html
new file mode 100644
index 0000000000..313046a348
--- /dev/null
+++ b/docshell/base/crashtests/40929-1-inner.html
@@ -0,0 +1,14 @@
+<html><head><title>Infinite Loop</title></head>
+<body onLoad="initNav(); initNav();">
+
+<script language="JavaScript">
+
+function initNav() {
+  ++parent.i;
+  if (parent.i < 10)
+  	window.location.href=window.location.href;
+}
+
+</script>
+
+</body></html>
diff --git a/docshell/base/crashtests/40929-1.html b/docshell/base/crashtests/40929-1.html
new file mode 100644
index 0000000000..90685d9f1f
--- /dev/null
+++ b/docshell/base/crashtests/40929-1.html
@@ -0,0 +1,6 @@
+<html>
+<head><title>Infinite Loop</title><script>var i=0;</script></head>
+<body>
+<iframe src="40929-1-inner.html"></iframe>
+</body>
+</html>
diff --git a/docshell/base/crashtests/430124-1.html b/docshell/base/crashtests/430124-1.html
new file mode 100644
index 0000000000..8cdbc1d077
--- /dev/null
+++ b/docshell/base/crashtests/430124-1.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<html>
+<head></head>
+<body onpagehide="document.getElementById('a').focus();"><div id="a"></div></body>
+</html>
diff --git a/docshell/base/crashtests/430628-1.html b/docshell/base/crashtests/430628-1.html
new file mode 100644
index 0000000000..4a68a5a015
--- /dev/null
+++ b/docshell/base/crashtests/430628-1.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body onpagehide="document.body.removeChild(document.getElementById('s'));">
+<span id="s" contenteditable="true"></span>
+</body>
+</html>
diff --git a/docshell/base/crashtests/432114-1.html b/docshell/base/crashtests/432114-1.html
new file mode 100644
index 0000000000..8878d6605a
--- /dev/null
+++ b/docshell/base/crashtests/432114-1.html
@@ -0,0 +1,8 @@
+<html>
+<head>
+<title>Bug - Crash [@ PL_DHashTableOperate] with DOMNodeInserted event listener removing window and frameset contenteditable</title>
+</head>
+<body>
+<iframe id="content" src="data:text/html;charset=utf-8,%3Cscript%3E%0Awindow.addEventListener%28%27DOMNodeInserted%27%2C%20function%28%29%20%7Bwindow.frameElement.parentNode.removeChild%28window.frameElement%29%3B%7D%2C%20true%29%3B%0A%3C/script%3E%0A%3Cframeset%20contenteditable%3D%22true%22%3E"></iframe>
+</body>
+</html>
diff --git a/docshell/base/crashtests/432114-2.html b/docshell/base/crashtests/432114-2.html
new file mode 100644
index 0000000000..da77287b61
--- /dev/null
+++ b/docshell/base/crashtests/432114-2.html
@@ -0,0 +1,21 @@
+<html class="reftest-wait">
+<head>
+<title>testcase2 Bug 432114 � Crash [@ PL_DHashTableOperate] with DOMNodeInserted event listener removing window and frameset contenteditable</title>
+</head>
+<body>
+<script>
+  window.addEventListener("DOMNodeRemoved", function() {
+    setTimeout(function() {
+      document.documentElement.removeAttribute("class");
+    }, 0);
+  });
+  var iframe = document.getElementById("content");
+  iframe.onload=function() {
+    dump("iframe onload\n");
+    console.log("iframe onload");
+  };
+</script>
+<iframe id="content" src="file_432114-2.xhtml" style="width:1000px;height: 200px;"></iframe>
+
+</body>
+</html>
diff --git a/docshell/base/crashtests/436900-1-inner.html b/docshell/base/crashtests/436900-1-inner.html
new file mode 100644
index 0000000000..6fe35ccb1a
--- /dev/null
+++ b/docshell/base/crashtests/436900-1-inner.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+<head>
+
+<meta http-equiv="refresh" content="0">
+
+<script language="javascript">
+
+location.hash += "+++";
+
+function done()
+{
+  parent.document.documentElement.removeAttribute("class");    
+}
+
+</script>
+</head>
+<body onload="setTimeout(done, 10)">
+
+</body>
+</html>
diff --git a/docshell/base/crashtests/436900-1.html b/docshell/base/crashtests/436900-1.html
new file mode 100644
index 0000000000..582d1919d1
--- /dev/null
+++ b/docshell/base/crashtests/436900-1.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+</head>
+<body>
+<iframe src="436900-1-inner.html#foo"></iframe>
+</body>
+</html>
diff --git a/docshell/base/crashtests/436900-2-inner.html b/docshell/base/crashtests/436900-2-inner.html
new file mode 100644
index 0000000000..ea79f75e88
--- /dev/null
+++ b/docshell/base/crashtests/436900-2-inner.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+<head>
+
+<meta http-equiv="refresh" content="0">
+
+<script language="javascript" id="foo+++">
+
+location.hash += "+++";
+
+function done()
+{
+  parent.document.documentElement.removeAttribute("class");    
+}
+
+</script>
+</head>
+<body onload="setTimeout(done, 10)">
+
+</body>
+</html>
diff --git a/docshell/base/crashtests/436900-2.html b/docshell/base/crashtests/436900-2.html
new file mode 100644
index 0000000000..2e1f0c1def
--- /dev/null
+++ b/docshell/base/crashtests/436900-2.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+</head>
+<body>
+<iframe src="436900-2-inner.html#foo"></iframe>
+</body>
+</html>
diff --git a/docshell/base/crashtests/443655.html b/docshell/base/crashtests/443655.html
new file mode 100644
index 0000000000..ce0a8c18b8
--- /dev/null
+++ b/docshell/base/crashtests/443655.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+
+<body onload="document.removeChild(document.documentElement)">
+
+<!-- The order of the two iframes matters! -->
+
+<iframe src='data:text/html,<body onload="s = parent.document.getElementById(&apos;s&apos;).contentWindow;" onunload="s.location = s.location;">'></iframe>
+
+<iframe id="s"></iframe>
+
+</body>
+</html>
diff --git a/docshell/base/crashtests/500328-1.html b/docshell/base/crashtests/500328-1.html
new file mode 100644
index 0000000000..fd97f84ae1
--- /dev/null
+++ b/docshell/base/crashtests/500328-1.html
@@ -0,0 +1,17 @@
+<!DOCTYPE HTML>
+<html>
+<body onload="test();">
+<script>
+  function test() {
+    // Test that calling pushState() with a state object which calls
+    // history.back() doesn't crash. We need to make sure that there's at least
+    // one entry in the history before we do anything else.
+    history.pushState(null, "");
+
+    x = {};
+    x.toJSON = { history.back(); return "{a:1}"; };
+    history.pushState(x, "");
+  }
+</script>
+</body>
+</html>
diff --git a/docshell/base/crashtests/514779-1.xhtml b/docshell/base/crashtests/514779-1.xhtml
new file mode 100644
index 0000000000..16ac3d9d66
--- /dev/null
+++ b/docshell/base/crashtests/514779-1.xhtml
@@ -0,0 +1,9 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head></head>
+
+<body onunload="document.getElementById('tbody').appendChild(document.createElementNS('http://www.w3.org/1999/xhtml', 'span'))">
+  <iframe/>
+  <tbody contenteditable="true" id="tbody">xy</tbody>
+</body>
+
+</html>
diff --git a/docshell/base/crashtests/614499-1.html b/docshell/base/crashtests/614499-1.html
new file mode 100644
index 0000000000..7053a3f52f
--- /dev/null
+++ b/docshell/base/crashtests/614499-1.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+<head>
+<script>
+
+function boom()
+{
+  var f = document.getElementById("f");
+
+  for (var i = 0; i < 50; ++i) {
+    f.contentWindow.history.pushState({}, "");
+  }
+
+  document.body.removeChild(f);
+}
+
+</script>
+</head>
+<body onload="boom();"><iframe id="f" src="data:text/html,1"></iframe></body>
+</html>
+\ No newline at end of file
diff --git a/docshell/base/crashtests/678872-1.html b/docshell/base/crashtests/678872-1.html
new file mode 100644
index 0000000000..294b3e689b
--- /dev/null
+++ b/docshell/base/crashtests/678872-1.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<html>
+<head>
+<script>
+
+var f1, f2;
+
+function b1()
+{
+  f1 = document.getElementById("f1");
+  f2 = document.getElementById("f2");
+  f1.contentWindow.document.write("11");
+  f1.contentWindow.history.back();
+  setTimeout(b2, 0);
+}
+
+function b2()
+{
+  f2.contentWindow.history.forward();
+  f2.contentWindow.location.reload();
+  f1.remove();
+}
+
+</script>
+
+
+</script>
+</head>
+
+<body onload="setTimeout(b1, 0);">
+
+<iframe id="f1" src="data:text/html,1"></iframe>
+<iframe id="f2" src="data:text/html,2"></iframe>
+
+</body>
+</html>
diff --git a/docshell/base/crashtests/914521.html b/docshell/base/crashtests/914521.html
new file mode 100644
index 0000000000..8196e43016
--- /dev/null
+++ b/docshell/base/crashtests/914521.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+<meta charset="UTF-8">
+<script>
+
+function f()
+{
+    function spin() {
+        for (var i = 0; i < 8; ++i) {
+            var x = new XMLHttpRequest();
+            x.open('GET', 'data:text/html,' + i, false);
+            x.send();
+        }
+    }
+
+    window.addEventListener("popstate", spin);
+    window.close();
+    window.location = "#c";
+    setTimeout(finish,0);
+}
+
+var win;
+function finish() {
+    win.close();
+    document.documentElement.removeAttribute("class");
+}
+
+function start()
+{
+    win = window.open("javascript:'<html><body>dummy</body></html>';", null, "width=300,height=300");
+    win.onload = f;
+}
+
+</script>
+</head>
+<body onload="start();"></body>
+</html>
diff --git a/docshell/base/crashtests/crashtests.list b/docshell/base/crashtests/crashtests.list
new file mode 100644
index 0000000000..f9b214bfa2
--- /dev/null
+++ b/docshell/base/crashtests/crashtests.list
@@ -0,0 +1,25 @@
+load 40929-1.html
+load 369126-1.html
+load 430124-1.html
+load 430628-1.html
+load 432114-1.html
+load 432114-2.html
+load 436900-1.html
+asserts(0-1) load 436900-2.html # bug 566159
+load 443655.html
+load 500328-1.html
+load 514779-1.xhtml
+load 614499-1.html
+load 678872-1.html
+skip-if(Android) pref(dom.disable_open_during_load,false) load 914521.html # Android bug 1584562
+pref(browser.send_pings,true) asserts(0-2) load 1257730-1.html # bug 566159
+load 1331295.html
+load 1341657.html
+load 1584467.html
+load 1614211-1.html
+load 1617315-1.html
+skip-if(Android) pref(dom.disable_open_during_load,false) load 1667491.html
+pref(dom.disable_open_during_load,false) load 1690169-1.html
+load 1672873.html
+load 1753136.html
+HTTP load 1804803.html
diff --git a/docshell/base/crashtests/file_432114-2.xhtml b/docshell/base/crashtests/file_432114-2.xhtml
new file mode 100644
index 0000000000..40bf886b8e
--- /dev/null
+++ b/docshell/base/crashtests/file_432114-2.xhtml
@@ -0,0 +1 @@
+<html xmlns='http://www.w3.org/1999/xhtml'><frameset contenteditable='true'/><script>function doExecCommand(){dump("doExecCommand\n");document.execCommand('formatBlock', false, 'p');}setTimeout(doExecCommand,100); window.addEventListener('DOMNodeRemoved', function() {window.frameElement.parentNode.removeChild(window.frameElement);}, true);</script></html>
diff --git a/docshell/base/metrics.yaml b/docshell/base/metrics.yaml
new file mode 100644
index 0000000000..ddb3457945
--- /dev/null
+++ b/docshell/base/metrics.yaml
@@ -0,0 +1,29 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Adding a new metric? We have docs for that!
+# https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/new_definitions_file.html
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - 'Core :: DOM: Navigation'
+
+performance.page:
+  total_content_page_load:
+    type: timing_distribution
+    time_unit: millisecond
+    telemetry_mirror: TOTAL_CONTENT_PAGE_LOAD_TIME
+    description: >
+      Time to load all of a page's resources and render.
+      (Migrated from the geckoview metric of the same name.)
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1580077
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1877842
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1580077#c10
+    notification_emails:
+      - perf-telemetry-alerts@mozilla.com
+      - bdekoz@mozilla.com
+    expires: never
diff --git a/docshell/base/moz.build b/docshell/base/moz.build
new file mode 100644
index 0000000000..3520e9d75a
--- /dev/null
+++ b/docshell/base/moz.build
@@ -0,0 +1,126 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "DOM: Navigation")
+
+with Files("crashtests/430628*"):
+    BUG_COMPONENT = ("Core", "DOM: Editor")
+
+with Files("crashtests/432114*"):
+    BUG_COMPONENT = ("Core", "DOM: Editor")
+
+with Files("crashtests/500328*"):
+    BUG_COMPONENT = ("Firefox", "Bookmarks & History")
+
+with Files("IHistory.h"):
+    BUG_COMPONENT = ("Toolkit", "Places")
+
+with Files("*LoadContext.*"):
+    BUG_COMPONENT = ("Core", "Networking")
+
+with Files("nsAboutRedirector.*"):
+    BUG_COMPONENT = ("Core", "General")
+
+with Files("nsIScrollObserver.*"):
+    BUG_COMPONENT = ("Core", "Panning and Zooming")
+
+XPIDL_SOURCES += [
+    "nsIDocShell.idl",
+    "nsIDocShellTreeItem.idl",
+    "nsIDocShellTreeOwner.idl",
+    "nsIDocumentLoaderFactory.idl",
+    "nsIDocumentViewer.idl",
+    "nsIDocumentViewerEdit.idl",
+    "nsILoadContext.idl",
+    "nsILoadURIDelegate.idl",
+    "nsIPrivacyTransitionObserver.idl",
+    "nsIReflowObserver.idl",
+    "nsIRefreshURI.idl",
+    "nsITooltipListener.idl",
+    "nsITooltipTextProvider.idl",
+    "nsIURIFixup.idl",
+    "nsIWebNavigation.idl",
+    "nsIWebNavigationInfo.idl",
+    "nsIWebPageDescriptor.idl",
+]
+
+XPIDL_MODULE = "docshell"
+
+EXPORTS += [
+    "nsCTooltipTextProvider.h",
+    "nsDocShell.h",
+    "nsDocShellLoadState.h",
+    "nsDocShellLoadTypes.h",
+    "nsDocShellTreeOwner.h",
+    "nsDSURIContentListener.h",
+    "nsIScrollObserver.h",
+    "nsWebNavigationInfo.h",
+    "SerializedLoadContext.h",
+]
+
+EXPORTS.mozilla += [
+    "BaseHistory.h",
+    "IHistory.h",
+    "LoadContext.h",
+]
+
+EXPORTS.mozilla.dom += [
+    "BrowsingContext.h",
+    "BrowsingContextGroup.h",
+    "BrowsingContextWebProgress.h",
+    "CanonicalBrowsingContext.h",
+    "ChildProcessChannelListener.h",
+    "SyncedContext.h",
+    "SyncedContextInlines.h",
+    "WindowContext.h",
+]
+
+UNIFIED_SOURCES += [
+    "BaseHistory.cpp",
+    "BrowsingContext.cpp",
+    "BrowsingContextGroup.cpp",
+    "BrowsingContextWebProgress.cpp",
+    "CanonicalBrowsingContext.cpp",
+    "ChildProcessChannelListener.cpp",
+    "LoadContext.cpp",
+    "nsAboutRedirector.cpp",
+    "nsDocShell.cpp",
+    "nsDocShellEditorData.cpp",
+    "nsDocShellEnumerator.cpp",
+    "nsDocShellLoadState.cpp",
+    "nsDocShellTelemetryUtils.cpp",
+    "nsDocShellTreeOwner.cpp",
+    "nsDSURIContentListener.cpp",
+    "nsPingListener.cpp",
+    "nsRefreshTimer.cpp",
+    "nsWebNavigationInfo.cpp",
+    "SerializedLoadContext.cpp",
+    "WindowContext.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+LOCAL_INCLUDES += [
+    "/docshell/shistory",
+    "/dom/base",
+    "/dom/bindings",
+    "/js/xpconnect/src",
+    "/layout/base",
+    "/layout/generic",
+    "/layout/style",
+    "/layout/xul",
+    "/netwerk/base",
+    "/netwerk/protocol/viewsource",
+    "/toolkit/components/browser",
+    "/toolkit/components/find",
+    "/tools/profiler",
+]
+
+EXTRA_JS_MODULES += ["URIFixup.sys.mjs"]
+
+include("/tools/fuzzing/libfuzzer-config.mozbuild")
diff --git a/docshell/base/nsAboutRedirector.cpp b/docshell/base/nsAboutRedirector.cpp
new file mode 100644
index 0000000000..fdae228b90
--- /dev/null
+++ b/docshell/base/nsAboutRedirector.cpp
@@ -0,0 +1,318 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsAboutRedirector.h"
+#include "nsNetUtil.h"
+#include "nsAboutProtocolUtils.h"
+#include "nsBaseChannel.h"
+#include "mozilla/ArrayUtils.h"
+#include "nsIProtocolHandler.h"
+#include "nsXULAppAPI.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/RemoteType.h"
+#include "mozilla/gfx/GPUProcessManager.h"
+
+#define ABOUT_CONFIG_ENABLED_PREF "general.aboutConfig.enable"
+
+NS_IMPL_ISUPPORTS(nsAboutRedirector, nsIAboutModule)
+
+struct RedirEntry {
+  const char* id;
+  const char* url;
+  uint32_t flags;
+};
+
+class CrashChannel final : public nsBaseChannel {
+ public:
+  explicit CrashChannel(nsIURI* aURI) { SetURI(aURI); }
+
+  nsresult OpenContentStream(bool async, nsIInputStream** stream,
+                             nsIChannel** channel) override {
+    nsAutoCString spec;
+    mURI->GetSpec(spec);
+
+    if (spec.EqualsASCII("about:crashparent") && XRE_IsParentProcess()) {
+      MOZ_CRASH("Crash via about:crashparent");
+    }
+
+    if (spec.EqualsASCII("about:crashgpu") && XRE_IsParentProcess()) {
+      if (auto* gpu = mozilla::gfx::GPUProcessManager::Get()) {
+        gpu->CrashProcess();
+      }
+    }
+
+    if (spec.EqualsASCII("about:crashcontent") && XRE_IsContentProcess()) {
+      MOZ_CRASH("Crash via about:crashcontent");
+    }
+
+    if (spec.EqualsASCII("about:crashextensions") && XRE_IsParentProcess()) {
+      using ContentParent = mozilla::dom::ContentParent;
+      nsTArray<RefPtr<ContentParent>> toKill;
+      for (auto* cp : ContentParent::AllProcesses(ContentParent::eLive)) {
+        if (cp->GetRemoteType() == EXTENSION_REMOTE_TYPE) {
+          toKill.AppendElement(cp);
+        }
+      }
+      for (auto& cp : toKill) {
+        cp->KillHard("Killed via about:crashextensions");
+      }
+    }
+
+    NS_WARNING("Unhandled about:crash* URI or wrong process");
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+ protected:
+  virtual ~CrashChannel() = default;
+};
+
+/*
+  Entries which do not have URI_SAFE_FOR_UNTRUSTED_CONTENT will run with chrome
+  privileges. This is potentially dangerous. Please use
+  URI_SAFE_FOR_UNTRUSTED_CONTENT in the third argument to each map item below
+  unless your about: page really needs chrome privileges. Security review is
+  required before adding new map entries without
+  URI_SAFE_FOR_UNTRUSTED_CONTENT.
+
+  URI_SAFE_FOR_UNTRUSTED_CONTENT is not enough to let web pages load that page,
+  for that you need MAKE_LINKABLE.
+
+  NOTE: changes to this redir map need to be accompanied with changes to
+    docshell/build/components.conf
+ */
+static const RedirEntry kRedirMap[] = {
+    {"about", "chrome://global/content/aboutAbout.html", 0},
+    {"addons", "chrome://mozapps/content/extensions/aboutaddons.html",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
+    {"buildconfig", "chrome://global/content/buildconfig.html",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::IS_SECURE_CHROME_UI},
+    {"checkerboard", "chrome://global/content/aboutCheckerboard.html",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::ALLOW_SCRIPT},
+#ifndef MOZ_WIDGET_ANDROID
+    {"config", "chrome://global/content/aboutconfig/aboutconfig.html",
+     nsIAboutModule::IS_SECURE_CHROME_UI},
+#else
+    {"config", "chrome://geckoview/content/config.xhtml",
+     nsIAboutModule::IS_SECURE_CHROME_UI},
+#endif
+#ifdef MOZ_CRASHREPORTER
+    {"crashes", "chrome://global/content/crashes.html",
+     nsIAboutModule::IS_SECURE_CHROME_UI},
+#endif
+    {"credits", "https://www.mozilla.org/credits/",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::URI_MUST_LOAD_IN_CHILD},
+    {"httpsonlyerror", "chrome://global/content/httpsonlyerror/errorpage.html",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::URI_CAN_LOAD_IN_CHILD | nsIAboutModule::ALLOW_SCRIPT |
+         nsIAboutModule::HIDE_FROM_ABOUTABOUT},
+    {"license", "chrome://global/content/license.html",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::IS_SECURE_CHROME_UI},
+    {"logging", "chrome://global/content/aboutLogging.html",
+     nsIAboutModule::ALLOW_SCRIPT},
+    {"logo", "chrome://branding/content/about.png",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         // Linkable for testing reasons.
+         nsIAboutModule::MAKE_LINKABLE},
+    {"memory", "chrome://global/content/aboutMemory.xhtml",
+     nsIAboutModule::ALLOW_SCRIPT},
+    {"certificate", "chrome://global/content/certviewer/certviewer.html",
+     nsIAboutModule::ALLOW_SCRIPT |
+         nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::URI_MUST_LOAD_IN_CHILD |
+         nsIAboutModule::URI_CAN_LOAD_IN_PRIVILEGEDABOUT_PROCESS |
+         nsIAboutModule::IS_SECURE_CHROME_UI},
+    {"mozilla", "chrome://global/content/mozilla.html",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT},
+#if !defined(ANDROID) && !defined(XP_WIN)
+    {"webauthn", "chrome://global/content/aboutWebauthn.html",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
+#endif
+    {"neterror", "chrome://global/content/aboutNetError.html",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::URI_CAN_LOAD_IN_CHILD | nsIAboutModule::ALLOW_SCRIPT |
+         nsIAboutModule::HIDE_FROM_ABOUTABOUT},
+    {"networking", "chrome://global/content/aboutNetworking.html",
+     nsIAboutModule::ALLOW_SCRIPT},
+    {"performance", "about:processes",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI |
+         nsIAboutModule::HIDE_FROM_ABOUTABOUT},
+    {"processes", "chrome://global/content/aboutProcesses.html",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
+    // about:serviceworkers always wants to load in the parent process because
+    // the only place nsIServiceWorkerManager has any data is in the parent
+    // process.
+    //
+    // There is overlap without about:debugging, but about:debugging is not
+    // available on mobile at this time, and it's useful to be able to know if
+    // a ServiceWorker is registered directly from the mobile browser without
+    // having to connect the device to a desktop machine and all that entails.
+    {"serviceworkers", "chrome://global/content/aboutServiceWorkers.xhtml",
+     nsIAboutModule::ALLOW_SCRIPT},
+#ifndef ANDROID
+    {"profiles", "chrome://global/content/aboutProfiles.xhtml",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
+#endif
+    // about:srcdoc is unresolvable by specification.  It is included here
+    // because the security manager would disallow srcdoc iframes otherwise.
+    {"srcdoc", "about:blank",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::HIDE_FROM_ABOUTABOUT |
+         // Needs to be linkable so content can touch its own srcdoc frames
+         nsIAboutModule::MAKE_LINKABLE | nsIAboutModule::URI_CAN_LOAD_IN_CHILD},
+    {"support", "chrome://global/content/aboutSupport.xhtml",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
+#ifdef XP_WIN
+    {"third-party", "chrome://global/content/aboutThirdParty.html",
+     nsIAboutModule::ALLOW_SCRIPT},
+    {"windows-messages", "chrome://global/content/aboutWindowsMessages.html",
+     nsIAboutModule::ALLOW_SCRIPT},
+#endif
+#ifndef MOZ_GLEAN_ANDROID
+    {"glean", "chrome://global/content/aboutGlean.html",
+#  if !defined(NIGHTLY_BUILD) && defined(MOZILLA_OFFICIAL)
+     nsIAboutModule::HIDE_FROM_ABOUTABOUT |
+#  endif
+         nsIAboutModule::ALLOW_SCRIPT},
+#endif
+    {"telemetry", "chrome://global/content/aboutTelemetry.xhtml",
+     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
+    {"translations", "chrome://global/content/translations/translations.html",
+     nsIAboutModule::ALLOW_SCRIPT |
+         nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::URI_MUST_LOAD_IN_CHILD |
+         nsIAboutModule::URI_CAN_LOAD_IN_PRIVILEGEDABOUT_PROCESS |
+         nsIAboutModule::HIDE_FROM_ABOUTABOUT},
+    {"url-classifier", "chrome://global/content/aboutUrlClassifier.xhtml",
+     nsIAboutModule::ALLOW_SCRIPT},
+    {"webrtc", "chrome://global/content/aboutwebrtc/aboutWebrtc.html",
+     nsIAboutModule::ALLOW_SCRIPT},
+    {"crashparent", "about:blank", nsIAboutModule::HIDE_FROM_ABOUTABOUT},
+    {"crashcontent", "about:blank",
+     nsIAboutModule::HIDE_FROM_ABOUTABOUT |
+         nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+         nsIAboutModule::URI_CAN_LOAD_IN_CHILD |
+         nsIAboutModule::URI_MUST_LOAD_IN_CHILD},
+    {"crashgpu", "about:blank", nsIAboutModule::HIDE_FROM_ABOUTABOUT},
+    {"crashextensions", "about:blank", nsIAboutModule::HIDE_FROM_ABOUTABOUT}};
+static const int kRedirTotal = mozilla::ArrayLength(kRedirMap);
+
+NS_IMETHODIMP
+nsAboutRedirector::NewChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo,
+                              nsIChannel** aResult) {
+  NS_ENSURE_ARG_POINTER(aURI);
+  NS_ENSURE_ARG_POINTER(aLoadInfo);
+  NS_ASSERTION(aResult, "must not be null");
+
+  nsAutoCString path;
+  nsresult rv = NS_GetAboutModuleName(aURI, path);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIIOService> ioService = do_GetIOService(&rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (path.EqualsASCII("crashparent") || path.EqualsASCII("crashcontent") ||
+      path.EqualsASCII("crashgpu") || path.EqualsASCII("crashextensions")) {
+    bool isExternal;
+    aLoadInfo->GetLoadTriggeredFromExternal(&isExternal);
+    if (isExternal || !aLoadInfo->TriggeringPrincipal() ||
+        !aLoadInfo->TriggeringPrincipal()->IsSystemPrincipal()) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+
+    nsCOMPtr<nsIChannel> channel = new CrashChannel(aURI);
+    channel->SetLoadInfo(aLoadInfo);
+    channel.forget(aResult);
+    return NS_OK;
+  }
+
+  if (path.EqualsASCII("config") &&
+      !mozilla::Preferences::GetBool(ABOUT_CONFIG_ENABLED_PREF, true)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  for (int i = 0; i < kRedirTotal; i++) {
+    if (!strcmp(path.get(), kRedirMap[i].id)) {
+      nsCOMPtr<nsIChannel> tempChannel;
+      nsCOMPtr<nsIURI> tempURI;
+      rv = NS_NewURI(getter_AddRefs(tempURI), kRedirMap[i].url);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      rv = NS_NewChannelInternal(getter_AddRefs(tempChannel), tempURI,
+                                 aLoadInfo);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      // If tempURI links to an external URI (i.e. something other than
+      // chrome:// or resource://) then set result principal URI on the
+      // load info which forces the channel principal to reflect the displayed
+      // URL rather then being the systemPrincipal.
+      bool isUIResource = false;
+      rv = NS_URIChainHasFlags(tempURI, nsIProtocolHandler::URI_IS_UI_RESOURCE,
+                               &isUIResource);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      bool isAboutBlank = NS_IsAboutBlank(tempURI);
+
+      if (!isUIResource && !isAboutBlank) {
+        aLoadInfo->SetResultPrincipalURI(tempURI);
+      }
+
+      tempChannel->SetOriginalURI(aURI);
+
+      tempChannel.forget(aResult);
+      return rv;
+    }
+  }
+
+  NS_ERROR("nsAboutRedirector called for unknown case");
+  return NS_ERROR_ILLEGAL_VALUE;
+}
+
+NS_IMETHODIMP
+nsAboutRedirector::GetURIFlags(nsIURI* aURI, uint32_t* aResult) {
+  NS_ENSURE_ARG_POINTER(aURI);
+
+  nsAutoCString name;
+  nsresult rv = NS_GetAboutModuleName(aURI, name);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  for (int i = 0; i < kRedirTotal; i++) {
+    if (name.EqualsASCII(kRedirMap[i].id)) {
+      *aResult = kRedirMap[i].flags;
+      return NS_OK;
+    }
+  }
+
+  NS_ERROR("nsAboutRedirector called for unknown case");
+  return NS_ERROR_ILLEGAL_VALUE;
+}
+
+NS_IMETHODIMP
+nsAboutRedirector::GetChromeURI(nsIURI* aURI, nsIURI** chromeURI) {
+  NS_ENSURE_ARG_POINTER(aURI);
+
+  nsAutoCString name;
+  nsresult rv = NS_GetAboutModuleName(aURI, name);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  for (const auto& redir : kRedirMap) {
+    if (name.EqualsASCII(redir.id)) {
+      return NS_NewURI(chromeURI, redir.url);
+    }
+  }
+
+  NS_ERROR("nsAboutRedirector called for unknown case");
+  return NS_ERROR_ILLEGAL_VALUE;
+}
+
+nsresult nsAboutRedirector::Create(REFNSIID aIID, void** aResult) {
+  RefPtr<nsAboutRedirector> about = new nsAboutRedirector();
+  return about->QueryInterface(aIID, aResult);
+}
diff --git a/docshell/base/nsAboutRedirector.h b/docshell/base/nsAboutRedirector.h
new file mode 100644
index 0000000000..0bf021cc31
--- /dev/null
+++ b/docshell/base/nsAboutRedirector.h
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsAboutRedirector_h__
+#define nsAboutRedirector_h__
+
+#include "nsIAboutModule.h"
+
+class nsAboutRedirector : public nsIAboutModule {
+ public:
+  NS_DECL_ISUPPORTS
+
+  NS_DECL_NSIABOUTMODULE
+
+  nsAboutRedirector() {}
+
+  static nsresult Create(REFNSIID aIID, void** aResult);
+
+ protected:
+  virtual ~nsAboutRedirector() {}
+};
+
+#endif  // nsAboutRedirector_h__
diff --git a/docshell/base/nsCTooltipTextProvider.h b/docshell/base/nsCTooltipTextProvider.h
new file mode 100644
index 0000000000..731edf1170
--- /dev/null
+++ b/docshell/base/nsCTooltipTextProvider.h
@@ -0,0 +1,15 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef NSCTOOLTIPTEXTPROVIDER_H
+#define NSCTOOLTIPTEXTPROVIDER_H
+
+#define NS_TOOLTIPTEXTPROVIDER_CONTRACTID \
+  "@mozilla.org/embedcomp/tooltiptextprovider;1"
+#define NS_DEFAULTTOOLTIPTEXTPROVIDER_CONTRACTID \
+  "@mozilla.org/embedcomp/default-tooltiptextprovider;1"
+
+#endif
diff --git a/docshell/base/nsDSURIContentListener.cpp b/docshell/base/nsDSURIContentListener.cpp
new file mode 100644
index 0000000000..2eccb74da9
--- /dev/null
+++ b/docshell/base/nsDSURIContentListener.cpp
@@ -0,0 +1,297 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDocShell.h"
+#include "nsDSURIContentListener.h"
+#include "nsIChannel.h"
+#include "nsServiceManagerUtils.h"
+#include "nsDocShellCID.h"
+#include "nsIWebNavigationInfo.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/Unused.h"
+#include "nsError.h"
+#include "nsContentSecurityManager.h"
+#include "nsDocShellLoadTypes.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIMultiPartChannel.h"
+#include "nsWebNavigationInfo.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+NS_IMPL_ADDREF(MaybeCloseWindowHelper)
+NS_IMPL_RELEASE(MaybeCloseWindowHelper)
+
+NS_INTERFACE_MAP_BEGIN(MaybeCloseWindowHelper)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsITimerCallback)
+  NS_INTERFACE_MAP_ENTRY(nsITimerCallback)
+  NS_INTERFACE_MAP_ENTRY(nsINamed)
+NS_INTERFACE_MAP_END
+
+MaybeCloseWindowHelper::MaybeCloseWindowHelper(BrowsingContext* aContentContext)
+    : mBrowsingContext(aContentContext),
+      mTimer(nullptr),
+      mShouldCloseWindow(false) {}
+
+MaybeCloseWindowHelper::~MaybeCloseWindowHelper() {}
+
+void MaybeCloseWindowHelper::SetShouldCloseWindow(bool aShouldCloseWindow) {
+  mShouldCloseWindow = aShouldCloseWindow;
+}
+
+BrowsingContext* MaybeCloseWindowHelper::MaybeCloseWindow() {
+  if (!mShouldCloseWindow) {
+    return mBrowsingContext;
+  }
+
+  // This method should not be called more than once, but it's better to avoid
+  // closing the current window again.
+  mShouldCloseWindow = false;
+
+  // Reset the window context to the opener window so that the dependent
+  // dialogs have a parent
+  RefPtr<BrowsingContext> newBC = ChooseNewBrowsingContext(mBrowsingContext);
+
+  if (newBC != mBrowsingContext && newBC && !newBC->IsDiscarded()) {
+    mBCToClose = mBrowsingContext;
+    mBrowsingContext = newBC;
+
+    // Now close the old window.  Do it on a timer so that we don't run
+    // into issues trying to close the window before it has fully opened.
+    NS_ASSERTION(!mTimer, "mTimer was already initialized once!");
+    NS_NewTimerWithCallback(getter_AddRefs(mTimer), this, 0,
+                            nsITimer::TYPE_ONE_SHOT);
+  }
+
+  return mBrowsingContext;
+}
+
+already_AddRefed<BrowsingContext>
+MaybeCloseWindowHelper::ChooseNewBrowsingContext(BrowsingContext* aBC) {
+  RefPtr<BrowsingContext> opener = aBC->GetOpener();
+  if (opener && !opener->IsDiscarded()) {
+    return opener.forget();
+  }
+
+  if (!XRE_IsParentProcess()) {
+    return nullptr;
+  }
+
+  opener = BrowsingContext::Get(aBC->Canonical()->GetCrossGroupOpenerId());
+  if (!opener || opener->IsDiscarded()) {
+    return nullptr;
+  }
+  return opener.forget();
+}
+
+NS_IMETHODIMP
+MaybeCloseWindowHelper::Notify(nsITimer* timer) {
+  NS_ASSERTION(mBCToClose, "No window to close after timer fired");
+
+  mBCToClose->Close(CallerType::System, IgnoreErrors());
+  mBCToClose = nullptr;
+  mTimer = nullptr;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MaybeCloseWindowHelper::GetName(nsACString& aName) {
+  aName.AssignLiteral("MaybeCloseWindowHelper");
+  return NS_OK;
+}
+
+nsDSURIContentListener::nsDSURIContentListener(nsDocShell* aDocShell)
+    : mDocShell(aDocShell),
+      mExistingJPEGRequest(nullptr),
+      mParentContentListener(nullptr) {}
+
+nsDSURIContentListener::~nsDSURIContentListener() {}
+
+NS_IMPL_ADDREF(nsDSURIContentListener)
+NS_IMPL_RELEASE(nsDSURIContentListener)
+
+NS_INTERFACE_MAP_BEGIN(nsDSURIContentListener)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIURIContentListener)
+  NS_INTERFACE_MAP_ENTRY(nsIURIContentListener)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+NS_INTERFACE_MAP_END
+
+NS_IMETHODIMP
+nsDSURIContentListener::DoContent(const nsACString& aContentType,
+                                  bool aIsContentPreferred,
+                                  nsIRequest* aRequest,
+                                  nsIStreamListener** aContentHandler,
+                                  bool* aAbortProcess) {
+  nsresult rv;
+  NS_ENSURE_ARG_POINTER(aContentHandler);
+  NS_ENSURE_TRUE(mDocShell, NS_ERROR_FAILURE);
+  RefPtr<nsDocShell> docShell = mDocShell;
+
+  *aAbortProcess = false;
+
+  // determine if the channel has just been retargeted to us...
+  nsLoadFlags loadFlags = 0;
+  if (nsCOMPtr<nsIChannel> openedChannel = do_QueryInterface(aRequest)) {
+    openedChannel->GetLoadFlags(&loadFlags);
+  }
+
+  if (loadFlags & nsIChannel::LOAD_RETARGETED_DOCUMENT_URI) {
+    // XXX: Why does this not stop the content too?
+    docShell->Stop(nsIWebNavigation::STOP_NETWORK);
+    NS_ENSURE_TRUE(mDocShell, NS_ERROR_FAILURE);
+    docShell->SetLoadType(aIsContentPreferred ? LOAD_LINK : LOAD_NORMAL);
+  }
+
+  // In case of multipart jpeg request (mjpeg) we don't really want to
+  // create new viewer since the one we already have is capable of
+  // rendering multipart jpeg correctly (see bug 625012)
+  nsCOMPtr<nsIChannel> baseChannel;
+  if (nsCOMPtr<nsIMultiPartChannel> mpchan = do_QueryInterface(aRequest)) {
+    mpchan->GetBaseChannel(getter_AddRefs(baseChannel));
+  }
+
+  bool reuseCV = baseChannel && baseChannel == mExistingJPEGRequest &&
+                 aContentType.EqualsLiteral("image/jpeg");
+
+  if (mExistingJPEGStreamListener && reuseCV) {
+    RefPtr<nsIStreamListener> copy(mExistingJPEGStreamListener);
+    copy.forget(aContentHandler);
+    rv = NS_OK;
+  } else {
+    rv =
+        docShell->CreateDocumentViewer(aContentType, aRequest, aContentHandler);
+    if (NS_SUCCEEDED(rv) && reuseCV) {
+      mExistingJPEGStreamListener = *aContentHandler;
+    } else {
+      mExistingJPEGStreamListener = nullptr;
+    }
+    mExistingJPEGRequest = baseChannel;
+  }
+
+  if (rv == NS_ERROR_DOCSHELL_DYING) {
+    aRequest->Cancel(rv);
+    *aAbortProcess = true;
+    return NS_OK;
+  }
+
+  if (NS_FAILED(rv)) {
+    // we don't know how to handle the content
+    nsCOMPtr<nsIStreamListener> forget = dont_AddRef(*aContentHandler);
+    *aContentHandler = nullptr;
+    return rv;
+  }
+
+  if (loadFlags & nsIChannel::LOAD_RETARGETED_DOCUMENT_URI) {
+    nsCOMPtr<nsPIDOMWindowOuter> domWindow =
+        mDocShell ? mDocShell->GetWindow() : nullptr;
+    NS_ENSURE_TRUE(domWindow, NS_ERROR_FAILURE);
+    domWindow->Focus(mozilla::dom::CallerType::System);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDSURIContentListener::IsPreferred(const char* aContentType,
+                                    char** aDesiredContentType,
+                                    bool* aCanHandle) {
+  NS_ENSURE_ARG_POINTER(aCanHandle);
+  NS_ENSURE_ARG_POINTER(aDesiredContentType);
+
+  // the docshell has no idea if it is the preferred content provider or not.
+  // It needs to ask its parent if it is the preferred content handler or not...
+
+  nsCOMPtr<nsIURIContentListener> parentListener;
+  GetParentContentListener(getter_AddRefs(parentListener));
+  if (parentListener) {
+    return parentListener->IsPreferred(aContentType, aDesiredContentType,
+                                       aCanHandle);
+  }
+  // we used to return false here if we didn't have a parent properly registered
+  // at the top of the docshell hierarchy to dictate what content types this
+  // docshell should be a preferred handler for. But this really makes it hard
+  // for developers using iframe or browser tags because then they need to make
+  // sure they implement nsIURIContentListener otherwise all link clicks would
+  // get sent to another window because we said we weren't the preferred handler
+  // type. I'm going to change the default now... if we can handle the content,
+  // and someone didn't EXPLICITLY set a nsIURIContentListener at the top of our
+  // docshell chain, then we'll now always attempt to process the content
+  // ourselves...
+  return CanHandleContent(aContentType, true, aDesiredContentType, aCanHandle);
+}
+
+NS_IMETHODIMP
+nsDSURIContentListener::CanHandleContent(const char* aContentType,
+                                         bool aIsContentPreferred,
+                                         char** aDesiredContentType,
+                                         bool* aCanHandleContent) {
+  MOZ_ASSERT(aCanHandleContent, "Null out param?");
+  NS_ENSURE_ARG_POINTER(aDesiredContentType);
+
+  *aCanHandleContent = false;
+  *aDesiredContentType = nullptr;
+
+  if (aContentType) {
+    uint32_t canHandle =
+        nsWebNavigationInfo::IsTypeSupported(nsDependentCString(aContentType));
+    *aCanHandleContent = (canHandle != nsIWebNavigationInfo::UNSUPPORTED);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDSURIContentListener::GetLoadCookie(nsISupports** aLoadCookie) {
+  NS_IF_ADDREF(*aLoadCookie = nsDocShell::GetAsSupports(mDocShell));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDSURIContentListener::SetLoadCookie(nsISupports* aLoadCookie) {
+#ifdef DEBUG
+  RefPtr<nsDocLoader> cookieAsDocLoader =
+      nsDocLoader::GetAsDocLoader(aLoadCookie);
+  NS_ASSERTION(cookieAsDocLoader && cookieAsDocLoader == mDocShell,
+               "Invalid load cookie being set!");
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDSURIContentListener::GetParentContentListener(
+    nsIURIContentListener** aParentListener) {
+  if (mWeakParentContentListener) {
+    nsCOMPtr<nsIURIContentListener> tempListener =
+        do_QueryReferent(mWeakParentContentListener);
+    *aParentListener = tempListener;
+    NS_IF_ADDREF(*aParentListener);
+  } else {
+    *aParentListener = mParentContentListener;
+    NS_IF_ADDREF(*aParentListener);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDSURIContentListener::SetParentContentListener(
+    nsIURIContentListener* aParentListener) {
+  if (aParentListener) {
+    // Store the parent listener as a weak ref. Parents not supporting
+    // nsISupportsWeakReference assert but may still be used.
+    mParentContentListener = nullptr;
+    mWeakParentContentListener = do_GetWeakReference(aParentListener);
+    if (!mWeakParentContentListener) {
+      mParentContentListener = aParentListener;
+    }
+  } else {
+    mWeakParentContentListener = nullptr;
+    mParentContentListener = nullptr;
+  }
+  return NS_OK;
+}
diff --git a/docshell/base/nsDSURIContentListener.h b/docshell/base/nsDSURIContentListener.h
new file mode 100644
index 0000000000..61ed36456f
--- /dev/null
+++ b/docshell/base/nsDSURIContentListener.h
@@ -0,0 +1,100 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDSURIContentListener_h__
+#define nsDSURIContentListener_h__
+
+#include "nsCOMPtr.h"
+#include "nsIURIContentListener.h"
+#include "nsWeakReference.h"
+#include "nsITimer.h"
+
+class nsDocShell;
+class nsIInterfaceRequestor;
+class nsIWebNavigationInfo;
+class nsPIDOMWindowOuter;
+
+// Helper Class to eventually close an already opened window
+class MaybeCloseWindowHelper final : public nsITimerCallback, public nsINamed {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSITIMERCALLBACK
+  NS_DECL_NSINAMED
+
+  explicit MaybeCloseWindowHelper(
+      mozilla::dom::BrowsingContext* aContentContext);
+
+  /**
+   * Closes the provided window async (if mShouldCloseWindow is true) and
+   * returns a valid browsingContext to be used instead as parent for dialogs or
+   * similar things.
+   * In case mShouldCloseWindow is true, the returned BrowsingContext will be
+   * the window's opener (or original cross-group opener in the case of a
+   * `noopener` popup).
+   */
+  mozilla::dom::BrowsingContext* MaybeCloseWindow();
+
+  void SetShouldCloseWindow(bool aShouldCloseWindow);
+
+ protected:
+  ~MaybeCloseWindowHelper();
+
+ private:
+  already_AddRefed<mozilla::dom::BrowsingContext> ChooseNewBrowsingContext(
+      mozilla::dom::BrowsingContext* aBC);
+
+  /**
+   * The dom window associated to handle content.
+   */
+  RefPtr<mozilla::dom::BrowsingContext> mBrowsingContext;
+
+  /**
+   * Used to close the window on a timer, to avoid any exceptions that are
+   * thrown if we try to close the window before it's fully loaded.
+   */
+  RefPtr<mozilla::dom::BrowsingContext> mBCToClose;
+  nsCOMPtr<nsITimer> mTimer;
+
+  /**
+   * This is set based on whether the channel indicates that a new window
+   * was opened, e.g. for a download, or was blocked. If so, then we
+   * close it.
+   */
+  bool mShouldCloseWindow;
+};
+
+class nsDSURIContentListener final : public nsIURIContentListener,
+                                     public nsSupportsWeakReference {
+  friend class nsDocShell;
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIURICONTENTLISTENER
+
+ protected:
+  explicit nsDSURIContentListener(nsDocShell* aDocShell);
+  virtual ~nsDSURIContentListener();
+
+  void DropDocShellReference() {
+    mDocShell = nullptr;
+    mExistingJPEGRequest = nullptr;
+    mExistingJPEGStreamListener = nullptr;
+  }
+
+ protected:
+  nsDocShell* mDocShell;
+  // Hack to handle multipart images without creating a new viewer
+  nsCOMPtr<nsIStreamListener> mExistingJPEGStreamListener;
+  nsCOMPtr<nsIChannel> mExistingJPEGRequest;
+
+  // Store the parent listener in either of these depending on
+  // if supports weak references or not. Proper weak refs are
+  // preferred and encouraged!
+  nsWeakPtr mWeakParentContentListener;
+  nsIURIContentListener* mParentContentListener;
+};
+
+#endif /* nsDSURIContentListener_h__ */
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
new file mode 100644
index 0000000000..f2a9e0fa59
--- /dev/null
+++ b/docshell/base/nsDocShell.cpp
@@ -0,0 +1,13763 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDocShell.h"
+
+#include <algorithm>
+
+#ifdef XP_WIN
+#  include <process.h>
+#  define getpid _getpid
+#else
+#  include <unistd.h>  // for getpid()
+#endif
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/AutoRestore.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/Casting.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Components.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/EventStateManager.h"
+#include "mozilla/HTMLEditor.h"
+#include "mozilla/InputTaskManager.h"
+#include "mozilla/LoadInfo.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MediaFeatureChange.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/ScrollTypes.h"
+#include "mozilla/SimpleEnumerator.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/StaticPrefs_docshell.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_extensions.h"
+#include "mozilla/StaticPrefs_privacy.h"
+#include "mozilla/StaticPrefs_security.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/StaticPrefs_fission.h"
+#include "mozilla/StartupTimeline.h"
+#include "mozilla/StorageAccess.h"
+#include "mozilla/StoragePrincipalHelper.h"
+#include "mozilla/Telemetry.h"
+
+#include "mozilla/Unused.h"
+#include "mozilla/WidgetUtils.h"
+
+#include "mozilla/dom/AutoEntryScript.h"
+#include "mozilla/dom/ChildProcessChannelListener.h"
+#include "mozilla/dom/ClientChannelHelper.h"
+#include "mozilla/dom/ClientHandle.h"
+#include "mozilla/dom/ClientInfo.h"
+#include "mozilla/dom/ClientManager.h"
+#include "mozilla/dom/ClientSource.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentFrameMessageManager.h"
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLAnchorElement.h"
+#include "mozilla/dom/HTMLIFrameElement.h"
+#include "mozilla/dom/PerformanceNavigation.h"
+#include "mozilla/dom/PermissionMessageUtils.h"
+#include "mozilla/dom/PopupBlocker.h"
+#include "mozilla/dom/ScreenOrientation.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/ServiceWorkerInterceptController.h"
+#include "mozilla/dom/ServiceWorkerUtils.h"
+#include "mozilla/dom/SessionHistoryEntry.h"
+#include "mozilla/dom/SessionStorageManager.h"
+#include "mozilla/dom/SessionStoreChangeListener.h"
+#include "mozilla/dom/SessionStoreChild.h"
+#include "mozilla/dom/SessionStoreUtils.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/UserActivation.h"
+#include "mozilla/dom/ChildSHistory.h"
+#include "mozilla/dom/nsCSPContext.h"
+#include "mozilla/dom/nsHTTPSOnlyUtils.h"
+#include "mozilla/dom/LoadURIOptionsBinding.h"
+#include "mozilla/dom/JSWindowActorChild.h"
+#include "mozilla/dom/DocumentBinding.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/net/DocumentChannel.h"
+#include "mozilla/net/DocumentChannelChild.h"
+#include "mozilla/net/ParentChannelWrapper.h"
+#include "mozilla/net/UrlClassifierFeatureFactory.h"
+#include "ReferrerInfo.h"
+
+#include "nsIAuthPrompt.h"
+#include "nsIAuthPrompt2.h"
+#include "nsICachingChannel.h"
+#include "nsICaptivePortalService.h"
+#include "nsIChannel.h"
+#include "nsIChannelEventSink.h"
+#include "nsIClassOfService.h"
+#include "nsIConsoleReportCollector.h"
+#include "nsIContent.h"
+#include "nsIContentInlines.h"
+#include "nsIContentSecurityPolicy.h"
+#include "nsIController.h"
+#include "nsIDocShellTreeItem.h"
+#include "nsIDocShellTreeOwner.h"
+#include "nsIDocumentViewer.h"
+#include "mozilla/dom/Document.h"
+#include "nsHTMLDocument.h"
+#include "nsIDocumentLoaderFactory.h"
+#include "nsIDOMWindow.h"
+#include "nsIEditingSession.h"
+#include "nsIEffectiveTLDService.h"
+#include "nsIExternalProtocolService.h"
+#include "nsIFormPOSTActionChannel.h"
+#include "nsIFrame.h"
+#include "nsIGlobalObject.h"
+#include "nsIHttpChannel.h"
+#include "nsIHttpChannelInternal.h"
+#include "nsIIDNService.h"
+#include "nsIInputStreamChannel.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsILayoutHistoryState.h"
+#include "nsILoadInfo.h"
+#include "nsILoadURIDelegate.h"
+#include "nsIMultiPartChannel.h"
+#include "nsINestedURI.h"
+#include "nsINetworkPredictor.h"
+#include "nsINode.h"
+#include "nsINSSErrorsService.h"
+#include "nsIObserverService.h"
+#include "nsIOService.h"
+#include "nsIPrincipal.h"
+#include "nsIPrivacyTransitionObserver.h"
+#include "nsIPrompt.h"
+#include "nsIPromptCollection.h"
+#include "nsIPromptFactory.h"
+#include "nsIPublicKeyPinningService.h"
+#include "nsIReflowObserver.h"
+#include "nsIScriptChannel.h"
+#include "nsIScriptObjectPrincipal.h"
+#include "nsIScriptSecurityManager.h"
+#include "nsIScrollableFrame.h"
+#include "nsIScrollObserver.h"
+#include "nsISupportsPrimitives.h"
+#include "nsISecureBrowserUI.h"
+#include "nsISeekableStream.h"
+#include "nsISelectionDisplay.h"
+#include "nsISHEntry.h"
+#include "nsISiteSecurityService.h"
+#include "nsISocketProvider.h"
+#include "nsIStringBundle.h"
+#include "nsIStructuredCloneContainer.h"
+#include "nsIBrowserChild.h"
+#include "nsITextToSubURI.h"
+#include "nsITimedChannel.h"
+#include "nsITimer.h"
+#include "nsITransportSecurityInfo.h"
+#include "nsIUploadChannel.h"
+#include "nsIURIFixup.h"
+#include "nsIURIMutator.h"
+#include "nsIURILoader.h"
+#include "nsIViewSourceChannel.h"
+#include "nsIWebBrowserChrome.h"
+#include "nsIWebBrowserChromeFocus.h"
+#include "nsIWebBrowserFind.h"
+#include "nsIWebProgress.h"
+#include "nsIWidget.h"
+#include "nsIWindowWatcher.h"
+#include "nsIWritablePropertyBag2.h"
+#include "nsIX509Cert.h"
+#include "nsIXULRuntime.h"
+
+#include "nsCommandManager.h"
+#include "nsPIDOMWindow.h"
+#include "nsPIWindowRoot.h"
+
+#include "IHistory.h"
+#include "IUrlClassifierUITelemetry.h"
+
+#include "nsArray.h"
+#include "nsArrayUtils.h"
+#include "nsCExternalHandlerService.h"
+#include "nsContentDLF.h"
+#include "nsContentPolicyUtils.h"  // NS_CheckContentLoadPolicy(...)
+#include "nsContentSecurityManager.h"
+#include "nsContentSecurityUtils.h"
+#include "nsContentUtils.h"
+#include "nsCURILoader.h"
+#include "nsDocShellCID.h"
+#include "nsDocShellEditorData.h"
+#include "nsDocShellEnumerator.h"
+#include "nsDocShellLoadState.h"
+#include "nsDocShellLoadTypes.h"
+#include "nsDOMCID.h"
+#include "nsDOMNavigationTiming.h"
+#include "nsDSURIContentListener.h"
+#include "nsEditingSession.h"
+#include "nsError.h"
+#include "nsEscape.h"
+#include "nsFocusManager.h"
+#include "nsGlobalWindowInner.h"
+#include "nsGlobalWindowOuter.h"
+#include "nsJSEnvironment.h"
+#include "nsNetCID.h"
+#include "nsNetUtil.h"
+#include "nsObjectLoadingContent.h"
+#include "nsPingListener.h"
+#include "nsPoint.h"
+#include "nsQueryObject.h"
+#include "nsQueryActor.h"
+#include "nsRect.h"
+#include "nsRefreshTimer.h"
+#include "nsSandboxFlags.h"
+#include "nsSHEntry.h"
+#include "nsSHistory.h"
+#include "nsSHEntry.h"
+#include "nsStructuredCloneContainer.h"
+#include "nsSubDocumentFrame.h"
+#include "nsURILoader.h"
+#include "nsURLHelper.h"
+#include "nsView.h"
+#include "nsViewManager.h"
+#include "nsViewSourceHandler.h"
+#include "nsWebBrowserFind.h"
+#include "nsWhitespaceTokenizer.h"
+#include "nsWidgetsCID.h"
+#include "nsXULAppAPI.h"
+
+#include "ThirdPartyUtil.h"
+#include "GeckoProfiler.h"
+#include "mozilla/NullPrincipal.h"
+#include "Navigator.h"
+#include "prenv.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "sslerr.h"
+#include "mozpkix/pkix.h"
+#include "NSSErrorsService.h"
+
+#include "nsDocShellTelemetryUtils.h"
+
+#ifdef MOZ_PLACES
+#  include "nsIFaviconService.h"
+#  include "mozIPlacesPendingOperation.h"
+#endif
+
+#if NS_PRINT_PREVIEW
+#  include "nsIDocumentViewerPrint.h"
+#  include "nsIWebBrowserPrint.h"
+#endif
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::net;
+
+using mozilla::ipc::Endpoint;
+
+// Threshold value in ms for META refresh based redirects
+#define REFRESH_REDIRECT_TIMER 15000
+
+static mozilla::LazyLogModule gCharsetMenuLog("CharsetMenu");
+
+#define LOGCHARSETMENU(args) \
+  MOZ_LOG(gCharsetMenuLog, mozilla::LogLevel::Debug, args)
+
+#ifdef DEBUG
+unsigned long nsDocShell::gNumberOfDocShells = 0;
+static uint64_t gDocshellIDCounter = 0;
+
+static mozilla::LazyLogModule gDocShellLog("nsDocShell");
+static mozilla::LazyLogModule gDocShellAndDOMWindowLeakLogging(
+    "DocShellAndDOMWindowLeak");
+#endif
+static mozilla::LazyLogModule gDocShellLeakLog("nsDocShellLeak");
+extern mozilla::LazyLogModule gPageCacheLog;
+mozilla::LazyLogModule gSHLog("SessionHistory");
+extern mozilla::LazyLogModule gSHIPBFCacheLog;
+
+const char kAppstringsBundleURL[] =
+    "chrome://global/locale/appstrings.properties";
+
+static bool IsTopLevelDoc(BrowsingContext* aBrowsingContext,
+                          nsILoadInfo* aLoadInfo) {
+  MOZ_ASSERT(aBrowsingContext);
+  MOZ_ASSERT(aLoadInfo);
+
+  if (aLoadInfo->GetExternalContentPolicyType() !=
+      ExtContentPolicy::TYPE_DOCUMENT) {
+    return false;
+  }
+
+  return aBrowsingContext->IsTopContent();
+}
+
+// True if loading for top level document loading in active tab.
+static bool IsUrgentStart(BrowsingContext* aBrowsingContext,
+                          nsILoadInfo* aLoadInfo, uint32_t aLoadType) {
+  MOZ_ASSERT(aBrowsingContext);
+  MOZ_ASSERT(aLoadInfo);
+
+  if (!IsTopLevelDoc(aBrowsingContext, aLoadInfo)) {
+    return false;
+  }
+
+  if (aLoadType &
+      (nsIDocShell::LOAD_CMD_NORMAL | nsIDocShell::LOAD_CMD_HISTORY)) {
+    return true;
+  }
+
+  return aBrowsingContext->IsActive();
+}
+
+nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
+                       uint64_t aContentWindowID)
+    : nsDocLoader(true),
+      mContentWindowID(aContentWindowID),
+      mBrowsingContext(aBrowsingContext),
+      mParentCharset(nullptr),
+      mTreeOwner(nullptr),
+      mScrollbarPref(ScrollbarPreference::Auto),
+      mCharsetReloadState(eCharsetReloadInit),
+      mParentCharsetSource(0),
+      mFrameMargins(-1, -1),
+      mItemType(aBrowsingContext->IsContent() ? typeContent : typeChrome),
+      mPreviousEntryIndex(-1),
+      mLoadedEntryIndex(-1),
+      mBusyFlags(BUSY_FLAGS_NONE),
+      mAppType(nsIDocShell::APP_TYPE_UNKNOWN),
+      mLoadType(0),
+      mFailedLoadType(0),
+      mMetaViewportOverride(nsIDocShell::META_VIEWPORT_OVERRIDE_NONE),
+      mChannelToDisconnectOnPageHide(0),
+      mCreatingDocument(false),
+#ifdef DEBUG
+      mInEnsureScriptEnv(false),
+#endif
+      mInitialized(false),
+      mAllowSubframes(true),
+      mAllowMetaRedirects(true),
+      mAllowImages(true),
+      mAllowMedia(true),
+      mAllowDNSPrefetch(true),
+      mAllowWindowControl(true),
+      mCSSErrorReportingEnabled(false),
+      mAllowAuth(mItemType == typeContent),
+      mAllowKeywordFixup(false),
+      mDisableMetaRefreshWhenInactive(false),
+      mWindowDraggingAllowed(false),
+      mInFrameSwap(false),
+      mFiredUnloadEvent(false),
+      mEODForCurrentDocument(false),
+      mURIResultedInDocument(false),
+      mIsBeingDestroyed(false),
+      mIsExecutingOnLoadHandler(false),
+      mSavingOldViewer(false),
+      mInvisible(false),
+      mHasLoadedNonBlankURI(false),
+      mBlankTiming(false),
+      mTitleValidForCurrentURI(false),
+      mWillChangeProcess(false),
+      mIsNavigating(false),
+      mForcedAutodetection(false),
+      mCheckingSessionHistory(false),
+      mNeedToReportActiveAfterLoadingBecomesActive(false) {
+  // If no outer window ID was provided, generate a new one.
+  if (aContentWindowID == 0) {
+    mContentWindowID = nsContentUtils::GenerateWindowId();
+  }
+
+  MOZ_LOG(gDocShellLeakLog, LogLevel::Debug, ("DOCSHELL %p created\n", this));
+
+#ifdef DEBUG
+  mDocShellID = gDocshellIDCounter++;
+  // We're counting the number of |nsDocShells| to help find leaks
+  ++gNumberOfDocShells;
+  MOZ_LOG(gDocShellAndDOMWindowLeakLogging, LogLevel::Info,
+          ("++DOCSHELL %p == %ld [pid = %d] [id = %" PRIu64 "]\n", (void*)this,
+           gNumberOfDocShells, getpid(), mDocShellID));
+#endif
+}
+
+nsDocShell::~nsDocShell() {
+  // Avoid notifying observers while we're in the dtor.
+  mIsBeingDestroyed = true;
+
+  Destroy();
+
+  if (mDocumentViewer) {
+    mDocumentViewer->Close(nullptr);
+    mDocumentViewer->Destroy();
+    mDocumentViewer = nullptr;
+  }
+
+  MOZ_LOG(gDocShellLeakLog, LogLevel::Debug, ("DOCSHELL %p destroyed\n", this));
+
+#ifdef DEBUG
+  if (MOZ_LOG_TEST(gDocShellAndDOMWindowLeakLogging, LogLevel::Info)) {
+    nsAutoCString url;
+    if (mLastOpenedURI) {
+      url = mLastOpenedURI->GetSpecOrDefault();
+
+      // Data URLs can be very long, so truncate to avoid flooding the log.
+      const uint32_t maxURLLength = 1000;
+      if (url.Length() > maxURLLength) {
+        url.Truncate(maxURLLength);
+      }
+    }
+
+    // We're counting the number of |nsDocShells| to help find leaks
+    --gNumberOfDocShells;
+    MOZ_LOG(
+        gDocShellAndDOMWindowLeakLogging, LogLevel::Info,
+        ("--DOCSHELL %p == %ld [pid = %d] [id = %" PRIu64 "] [url = %s]\n",
+         (void*)this, gNumberOfDocShells, getpid(), mDocShellID, url.get()));
+  }
+#endif
+}
+
+bool nsDocShell::Initialize() {
+  if (mInitialized) {
+    // We've already been initialized.
+    return true;
+  }
+
+  NS_ASSERTION(mItemType == typeContent || mItemType == typeChrome,
+               "Unexpected item type in docshell");
+
+  NS_ENSURE_TRUE(Preferences::GetRootBranch(), false);
+  mInitialized = true;
+
+  mDisableMetaRefreshWhenInactive =
+      Preferences::GetBool("browser.meta_refresh_when_inactive.disabled",
+                           mDisableMetaRefreshWhenInactive);
+
+  if (nsCOMPtr<nsIObserverService> serv = services::GetObserverService()) {
+    const char* msg = mItemType == typeContent ? NS_WEBNAVIGATION_CREATE
+                                               : NS_CHROME_WEBNAVIGATION_CREATE;
+    serv->NotifyWhenScriptSafe(GetAsSupports(this), msg, nullptr);
+  }
+
+  return true;
+}
+
+/* static */
+already_AddRefed<nsDocShell> nsDocShell::Create(
+    BrowsingContext* aBrowsingContext, uint64_t aContentWindowID) {
+  MOZ_ASSERT(aBrowsingContext, "DocShell without a BrowsingContext!");
+
+  nsresult rv;
+  RefPtr<nsDocShell> ds = new nsDocShell(aBrowsingContext, aContentWindowID);
+
+  // Initialize the underlying nsDocLoader.
+  rv = ds->nsDocLoader::InitWithBrowsingContext(aBrowsingContext);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // Create our ContentListener
+  ds->mContentListener = new nsDSURIContentListener(ds);
+
+  // We enable if we're in the parent process in order to support non-e10s
+  // configurations.
+  // Note: This check is duplicated in SharedWorkerInterfaceRequestor's
+  // constructor.
+  if (XRE_IsParentProcess()) {
+    ds->mInterceptController = new ServiceWorkerInterceptController();
+  }
+
+  // We want to hold a strong ref to the loadgroup, so it better hold a weak
+  // ref to us...  use an InterfaceRequestorProxy to do this.
+  nsCOMPtr<nsIInterfaceRequestor> proxy = new InterfaceRequestorProxy(ds);
+  ds->mLoadGroup->SetNotificationCallbacks(proxy);
+
+  // XXX(nika): We have our BrowsingContext, so we might be able to skip this.
+  // It could be nice to directly set up our DocLoader tree?
+  rv = nsDocLoader::AddDocLoaderAsChildOfRoot(ds);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // Add |ds| as a progress listener to itself.  A little weird, but simpler
+  // than reproducing all the listener-notification logic in overrides of the
+  // various methods via which nsDocLoader can be notified.   Note that this
+  // holds an nsWeakPtr to |ds|, so it's ok.
+  rv = ds->AddProgressListener(ds, nsIWebProgress::NOTIFY_STATE_DOCUMENT |
+                                       nsIWebProgress::NOTIFY_STATE_NETWORK |
+                                       nsIWebProgress::NOTIFY_LOCATION);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // If our BrowsingContext has private browsing enabled, update the number of
+  // private browsing docshells.
+  if (aBrowsingContext->UsePrivateBrowsing()) {
+    ds->NotifyPrivateBrowsingChanged();
+  }
+
+  // If our parent window is present in this process, set up our parent now.
+  RefPtr<WindowContext> parentWC = aBrowsingContext->GetParentWindowContext();
+  if (parentWC && parentWC->IsInProcess()) {
+    // If we don't have a parent element anymore, we can't finish this load!
+    // How'd we get here?
+    RefPtr<Element> parentElement = aBrowsingContext->GetEmbedderElement();
+    if (!parentElement) {
+      MOZ_ASSERT_UNREACHABLE("nsDocShell::Create() - !parentElement");
+      return nullptr;
+    }
+
+    // We have an in-process parent window, but don't have a parent nsDocShell?
+    // How'd we get here!
+    nsCOMPtr<nsIDocShell> parentShell =
+        parentElement->OwnerDoc()->GetDocShell();
+    if (!parentShell) {
+      MOZ_ASSERT_UNREACHABLE("nsDocShell::Create() - !parentShell");
+      return nullptr;
+    }
+    parentShell->AddChild(ds);
+  }
+
+  // Make |ds| the primary DocShell for the given context.
+  aBrowsingContext->SetDocShell(ds);
+
+  // Set |ds| default load flags on load group.
+  ds->SetLoadGroupDefaultLoadFlags(aBrowsingContext->GetDefaultLoadFlags());
+
+  if (XRE_IsParentProcess()) {
+    aBrowsingContext->Canonical()->MaybeAddAsProgressListener(ds);
+  }
+
+  return ds.forget();
+}
+
+void nsDocShell::DestroyChildren() {
+  for (auto* child : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShellTreeItem> shell = do_QueryObject(child);
+    NS_ASSERTION(shell, "docshell has null child");
+
+    if (shell) {
+      shell->SetTreeOwner(nullptr);
+    }
+  }
+
+  nsDocLoader::DestroyChildren();
+}
+
+NS_IMPL_CYCLE_COLLECTION_WEAK_PTR_INHERITED(nsDocShell, nsDocLoader,
+                                            mScriptGlobal, mInitialClientSource,
+                                            mBrowsingContext,
+                                            mChromeEventHandler)
+
+NS_IMPL_ADDREF_INHERITED(nsDocShell, nsDocLoader)
+NS_IMPL_RELEASE_INHERITED(nsDocShell, nsDocLoader)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsDocShell)
+  NS_INTERFACE_MAP_ENTRY(nsIDocShell)
+  NS_INTERFACE_MAP_ENTRY(nsIDocShellTreeItem)
+  NS_INTERFACE_MAP_ENTRY(nsIWebNavigation)
+  NS_INTERFACE_MAP_ENTRY(nsIBaseWindow)
+  NS_INTERFACE_MAP_ENTRY(nsIRefreshURI)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+  NS_INTERFACE_MAP_ENTRY(nsIWebPageDescriptor)
+  NS_INTERFACE_MAP_ENTRY(nsIAuthPromptProvider)
+  NS_INTERFACE_MAP_ENTRY(nsILoadContext)
+  NS_INTERFACE_MAP_ENTRY_CONDITIONAL(nsINetworkInterceptController,
+                                     mInterceptController)
+NS_INTERFACE_MAP_END_INHERITING(nsDocLoader)
+
+NS_IMETHODIMP
+nsDocShell::GetInterface(const nsIID& aIID, void** aSink) {
+  MOZ_ASSERT(aSink, "null out param");
+
+  *aSink = nullptr;
+
+  if (aIID.Equals(NS_GET_IID(nsICommandManager))) {
+    NS_ENSURE_SUCCESS(EnsureCommandHandler(), NS_ERROR_FAILURE);
+    *aSink = static_cast<nsICommandManager*>(mCommandManager.get());
+  } else if (aIID.Equals(NS_GET_IID(nsIURIContentListener))) {
+    *aSink = mContentListener;
+  } else if ((aIID.Equals(NS_GET_IID(nsIScriptGlobalObject)) ||
+              aIID.Equals(NS_GET_IID(nsIGlobalObject)) ||
+              aIID.Equals(NS_GET_IID(nsPIDOMWindowOuter)) ||
+              aIID.Equals(NS_GET_IID(mozIDOMWindowProxy)) ||
+              aIID.Equals(NS_GET_IID(nsIDOMWindow))) &&
+             NS_SUCCEEDED(EnsureScriptEnvironment())) {
+    return mScriptGlobal->QueryInterface(aIID, aSink);
+  } else if (aIID.Equals(NS_GET_IID(Document)) &&
+             NS_SUCCEEDED(EnsureDocumentViewer())) {
+    RefPtr<Document> doc = mDocumentViewer->GetDocument();
+    doc.forget(aSink);
+    return *aSink ? NS_OK : NS_NOINTERFACE;
+  } else if (aIID.Equals(NS_GET_IID(nsIPrompt)) &&
+             NS_SUCCEEDED(EnsureScriptEnvironment())) {
+    nsresult rv;
+    nsCOMPtr<nsIWindowWatcher> wwatch =
+        do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Get the an auth prompter for our window so that the parenting
+    // of the dialogs works as it should when using tabs.
+    nsIPrompt* prompt;
+    rv = wwatch->GetNewPrompter(mScriptGlobal, &prompt);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    *aSink = prompt;
+    return NS_OK;
+  } else if (aIID.Equals(NS_GET_IID(nsIAuthPrompt)) ||
+             aIID.Equals(NS_GET_IID(nsIAuthPrompt2))) {
+    return NS_SUCCEEDED(GetAuthPrompt(PROMPT_NORMAL, aIID, aSink))
+               ? NS_OK
+               : NS_NOINTERFACE;
+  } else if (aIID.Equals(NS_GET_IID(nsISHistory))) {
+    // This is deprecated, you should instead directly get
+    // ChildSHistory from the browsing context.
+    MOZ_DIAGNOSTIC_ASSERT(
+        false, "Do not try to get a nsISHistory interface from nsIDocShell");
+    return NS_NOINTERFACE;
+  } else if (aIID.Equals(NS_GET_IID(nsIWebBrowserFind))) {
+    nsresult rv = EnsureFind();
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    *aSink = mFind;
+    NS_ADDREF((nsISupports*)*aSink);
+    return NS_OK;
+  } else if (aIID.Equals(NS_GET_IID(nsISelectionDisplay))) {
+    if (PresShell* presShell = GetPresShell()) {
+      return presShell->QueryInterface(aIID, aSink);
+    }
+  } else if (aIID.Equals(NS_GET_IID(nsIDocShellTreeOwner))) {
+    nsCOMPtr<nsIDocShellTreeOwner> treeOwner;
+    nsresult rv = GetTreeOwner(getter_AddRefs(treeOwner));
+    if (NS_SUCCEEDED(rv) && treeOwner) {
+      return treeOwner->QueryInterface(aIID, aSink);
+    }
+  } else if (aIID.Equals(NS_GET_IID(nsIBrowserChild))) {
+    *aSink = GetBrowserChild().take();
+    return *aSink ? NS_OK : NS_ERROR_FAILURE;
+  } else {
+    return nsDocLoader::GetInterface(aIID, aSink);
+  }
+
+  NS_IF_ADDREF(((nsISupports*)*aSink));
+  return *aSink ? NS_OK : NS_NOINTERFACE;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetCancelContentJSEpoch(int32_t aEpoch) {
+  // Note: this gets called fairly early (before a pageload actually starts).
+  // We could probably defer this even longer.
+  nsCOMPtr<nsIBrowserChild> browserChild = GetBrowserChild();
+  static_cast<BrowserChild*>(browserChild.get())
+      ->SetCancelContentJSEpoch(aEpoch);
+  return NS_OK;
+}
+
+nsresult nsDocShell::CheckDisallowedJavascriptLoad(
+    nsDocShellLoadState* aLoadState) {
+  if (!net::SchemeIsJavascript(aLoadState->URI())) {
+    return NS_OK;
+  }
+
+  if (nsCOMPtr<nsIPrincipal> targetPrincipal =
+          GetInheritedPrincipal(/* aConsiderCurrentDocument */ true)) {
+    if (!aLoadState->TriggeringPrincipal()->Subsumes(targetPrincipal)) {
+      return NS_ERROR_DOM_BAD_CROSS_ORIGIN_URI;
+    }
+    return NS_OK;
+  }
+  return NS_ERROR_DOM_BAD_CROSS_ORIGIN_URI;
+}
+
+NS_IMETHODIMP
+nsDocShell::LoadURI(nsDocShellLoadState* aLoadState, bool aSetNavigating) {
+  return LoadURI(aLoadState, aSetNavigating, false);
+}
+
+nsresult nsDocShell::LoadURI(nsDocShellLoadState* aLoadState,
+                             bool aSetNavigating,
+                             bool aContinueHandlingSubframeHistory) {
+  MOZ_ASSERT(aLoadState, "Must have a valid load state!");
+  // NOTE: This comparison between what appears to be internal/external load
+  // flags is intentional, as it's ensuring that the caller isn't using any of
+  // the flags reserved for implementations by the `nsIWebNavigation` interface.
+  // In the future, this check may be dropped.
+  MOZ_ASSERT(
+      (aLoadState->LoadFlags() & INTERNAL_LOAD_FLAGS_LOADURI_SETUP_FLAGS) == 0,
+      "Should not have these flags set");
+  MOZ_ASSERT(aLoadState->TargetBrowsingContext().IsNull(),
+             "Targeting doesn't occur until InternalLoad");
+
+  if (!aLoadState->TriggeringPrincipal()) {
+    MOZ_ASSERT(false, "LoadURI must have a triggering principal");
+    return NS_ERROR_FAILURE;
+  }
+
+  MOZ_TRY(CheckDisallowedJavascriptLoad(aLoadState));
+
+  bool oldIsNavigating = mIsNavigating;
+  auto cleanupIsNavigating =
+      MakeScopeExit([&]() { mIsNavigating = oldIsNavigating; });
+  if (aSetNavigating) {
+    mIsNavigating = true;
+  }
+
+  PopupBlocker::PopupControlState popupState = PopupBlocker::openOverridden;
+  if (aLoadState->HasLoadFlags(LOAD_FLAGS_ALLOW_POPUPS)) {
+    popupState = PopupBlocker::openAllowed;
+    // If we allow popups as part of the navigation, ensure we fake a user
+    // interaction, so that popups can, in fact, be allowed to open.
+    if (WindowContext* wc = mBrowsingContext->GetCurrentWindowContext()) {
+      wc->NotifyUserGestureActivation();
+    }
+  }
+
+  AutoPopupStatePusher statePusher(popupState);
+
+  if (aLoadState->GetCancelContentJSEpoch().isSome()) {
+    SetCancelContentJSEpoch(*aLoadState->GetCancelContentJSEpoch());
+  }
+
+  // Note: we allow loads to get through here even if mFiredUnloadEvent is
+  // true; that case will get handled in LoadInternal or LoadHistoryEntry,
+  // so we pass false as the second parameter to IsNavigationAllowed.
+  // However, we don't allow the page to change location *in the middle of*
+  // firing beforeunload, so we do need to check if *beforeunload* is currently
+  // firing, so we call IsNavigationAllowed rather than just IsPrintingOrPP.
+  if (!IsNavigationAllowed(true, false)) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+
+  nsLoadFlags defaultLoadFlags = mBrowsingContext->GetDefaultLoadFlags();
+  if (aLoadState->HasLoadFlags(LOAD_FLAGS_FORCE_TRR)) {
+    defaultLoadFlags |= nsIRequest::LOAD_TRR_ONLY_MODE;
+  } else if (aLoadState->HasLoadFlags(LOAD_FLAGS_DISABLE_TRR)) {
+    defaultLoadFlags |= nsIRequest::LOAD_TRR_DISABLED_MODE;
+  }
+
+  MOZ_ALWAYS_SUCCEEDS(mBrowsingContext->SetDefaultLoadFlags(defaultLoadFlags));
+
+  if (!StartupTimeline::HasRecord(StartupTimeline::FIRST_LOAD_URI) &&
+      mItemType == typeContent && !NS_IsAboutBlank(aLoadState->URI())) {
+    StartupTimeline::RecordOnce(StartupTimeline::FIRST_LOAD_URI);
+  }
+
+  // LoadType used to be set to a default value here, if no LoadInfo/LoadState
+  // object was passed in. That functionality has been removed as of bug
+  // 1492648. LoadType should now be set up by the caller at the time they
+  // create their nsDocShellLoadState object to pass into LoadURI.
+
+  MOZ_LOG(
+      gDocShellLeakLog, LogLevel::Debug,
+      ("nsDocShell[%p]: loading %s with flags 0x%08x", this,
+       aLoadState->URI()->GetSpecOrDefault().get(), aLoadState->LoadFlags()));
+
+  if ((!aLoadState->LoadIsFromSessionHistory() &&
+       !LOAD_TYPE_HAS_FLAGS(aLoadState->LoadType(),
+                            LOAD_FLAGS_REPLACE_HISTORY)) ||
+      aContinueHandlingSubframeHistory) {
+    // This is possibly a subframe, so handle it accordingly.
+    //
+    // If history exists, it will be loaded into the aLoadState object, and the
+    // LoadType will be changed.
+    if (MaybeHandleSubframeHistory(aLoadState,
+                                   aContinueHandlingSubframeHistory)) {
+      // MaybeHandleSubframeHistory returns true if we need to continue loading
+      // asynchronously.
+      return NS_OK;
+    }
+  }
+
+  if (aLoadState->LoadIsFromSessionHistory()) {
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("nsDocShell[%p]: loading from session history", this));
+
+    if (!mozilla::SessionHistoryInParent()) {
+      nsCOMPtr<nsISHEntry> entry = aLoadState->SHEntry();
+      return LoadHistoryEntry(entry, aLoadState->LoadType(),
+                              aLoadState->HasValidUserGestureActivation());
+    }
+
+    // FIXME Null check aLoadState->GetLoadingSessionHistoryInfo()?
+    return LoadHistoryEntry(*aLoadState->GetLoadingSessionHistoryInfo(),
+                            aLoadState->LoadType(),
+                            aLoadState->HasValidUserGestureActivation());
+  }
+
+  // On history navigation via Back/Forward buttons, don't execute
+  // automatic JavaScript redirection such as |location.href = ...| or
+  // |window.open()|
+  //
+  // LOAD_NORMAL:        window.open(...) etc.
+  // LOAD_STOP_CONTENT:  location.href = ..., location.assign(...)
+  if ((aLoadState->LoadType() == LOAD_NORMAL ||
+       aLoadState->LoadType() == LOAD_STOP_CONTENT) &&
+      ShouldBlockLoadingForBackButton()) {
+    return NS_OK;
+  }
+
+  BrowsingContext::Type bcType = mBrowsingContext->GetType();
+
+  // Set up the inheriting principal in LoadState.
+  nsresult rv = aLoadState->SetupInheritingPrincipal(
+      bcType, mBrowsingContext->OriginAttributesRef());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadState->SetupTriggeringPrincipal(
+      mBrowsingContext->OriginAttributesRef());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aLoadState->CalculateLoadURIFlags();
+
+  MOZ_ASSERT(aLoadState->TypeHint().IsVoid(),
+             "Typehint should be null when calling InternalLoad from LoadURI");
+  MOZ_ASSERT(aLoadState->FileName().IsVoid(),
+             "FileName should be null when calling InternalLoad from LoadURI");
+  MOZ_ASSERT(!aLoadState->LoadIsFromSessionHistory(),
+             "Shouldn't be loading from an entry when calling InternalLoad "
+             "from LoadURI");
+
+  // If we have a system triggering principal, we can assume that this load was
+  // triggered by some UI in the browser chrome, such as the URL bar or
+  // bookmark bar. This should count as a user interaction for the current sh
+  // entry, so that the user may navigate back to the current entry, from the
+  // entry that is going to be added as part of this load.
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal =
+      aLoadState->TriggeringPrincipal();
+  if (triggeringPrincipal && triggeringPrincipal->IsSystemPrincipal()) {
+    if (mozilla::SessionHistoryInParent()) {
+      WindowContext* topWc = mBrowsingContext->GetTopWindowContext();
+      if (topWc && !topWc->IsDiscarded()) {
+        MOZ_ALWAYS_SUCCEEDS(topWc->SetSHEntryHasUserInteraction(true));
+      }
+    } else {
+      bool oshe = false;
+      nsCOMPtr<nsISHEntry> currentSHEntry;
+      GetCurrentSHEntry(getter_AddRefs(currentSHEntry), &oshe);
+      if (currentSHEntry) {
+        currentSHEntry->SetHasUserInteraction(true);
+      }
+    }
+  }
+
+  rv = InternalLoad(aLoadState);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (aLoadState->GetOriginalURIString().isSome()) {
+    // Save URI string in case it's needed later when
+    // sending to search engine service in EndPageLoad()
+    mOriginalUriString = *aLoadState->GetOriginalURIString();
+  }
+
+  return NS_OK;
+}
+
+bool nsDocShell::IsLoadingFromSessionHistory() {
+  return mActiveEntryIsLoadingFromSessionHistory;
+}
+
+// StopDetector is modeled similarly to OnloadBlocker; it is a rather
+// dummy nsIRequest implementation which can be added to an nsILoadGroup to
+// detect Cancel calls.
+class StopDetector final : public nsIRequest {
+ public:
+  StopDetector() = default;
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIREQUEST
+
+  bool Canceled() { return mCanceled; }
+
+ private:
+  ~StopDetector() = default;
+
+  bool mCanceled = false;
+};
+
+NS_IMPL_ISUPPORTS(StopDetector, nsIRequest)
+
+NS_IMETHODIMP
+StopDetector::GetName(nsACString& aResult) {
+  aResult.AssignLiteral("about:stop-detector");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StopDetector::IsPending(bool* aRetVal) {
+  *aRetVal = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StopDetector::GetStatus(nsresult* aStatus) {
+  *aStatus = NS_OK;
+  return NS_OK;
+}
+
+NS_IMETHODIMP StopDetector::SetCanceledReason(const nsACString& aReason) {
+  return SetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP StopDetector::GetCanceledReason(nsACString& aReason) {
+  return GetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP StopDetector::CancelWithReason(nsresult aStatus,
+                                             const nsACString& aReason) {
+  return CancelWithReasonImpl(aStatus, aReason);
+}
+
+NS_IMETHODIMP
+StopDetector::Cancel(nsresult aStatus) {
+  mCanceled = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StopDetector::Suspend(void) { return NS_OK; }
+NS_IMETHODIMP
+StopDetector::Resume(void) { return NS_OK; }
+
+NS_IMETHODIMP
+StopDetector::GetLoadGroup(nsILoadGroup** aLoadGroup) {
+  *aLoadGroup = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StopDetector::SetLoadGroup(nsILoadGroup* aLoadGroup) { return NS_OK; }
+
+NS_IMETHODIMP
+StopDetector::GetLoadFlags(nsLoadFlags* aLoadFlags) {
+  *aLoadFlags = nsIRequest::LOAD_NORMAL;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StopDetector::GetTRRMode(nsIRequest::TRRMode* aTRRMode) {
+  return GetTRRModeImpl(aTRRMode);
+}
+
+NS_IMETHODIMP
+StopDetector::SetTRRMode(nsIRequest::TRRMode aTRRMode) {
+  return SetTRRModeImpl(aTRRMode);
+}
+
+NS_IMETHODIMP
+StopDetector::SetLoadFlags(nsLoadFlags aLoadFlags) { return NS_OK; }
+
+bool nsDocShell::MaybeHandleSubframeHistory(
+    nsDocShellLoadState* aLoadState, bool aContinueHandlingSubframeHistory) {
+  // First, verify if this is a subframe.
+  // Note, it is ok to rely on docshell here and not browsing context since when
+  // an iframe is created, it has first in-process docshell.
+  nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
+  GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
+  nsCOMPtr<nsIDocShell> parentDS(do_QueryInterface(parentAsItem));
+
+  if (!parentDS || parentDS == static_cast<nsIDocShell*>(this)) {
+    if (mBrowsingContext && mBrowsingContext->IsTop()) {
+      // This is the root docshell. If we got here while
+      // executing an onLoad Handler,this load will not go
+      // into session history.
+      // XXX Why is this code in a method which deals with iframes!
+      if (aLoadState->IsFormSubmission()) {
+#ifdef DEBUG
+        if (!mEODForCurrentDocument) {
+          const MaybeDiscarded<BrowsingContext>& targetBC =
+              aLoadState->TargetBrowsingContext();
+          MOZ_ASSERT_IF(GetBrowsingContext() == targetBC.get(),
+                        aLoadState->LoadType() == LOAD_NORMAL_REPLACE);
+        }
+#endif
+      } else {
+        bool inOnLoadHandler = false;
+        GetIsExecutingOnLoadHandler(&inOnLoadHandler);
+        if (inOnLoadHandler) {
+          aLoadState->SetLoadType(LOAD_NORMAL_REPLACE);
+        }
+      }
+    }
+    return false;
+  }
+
+  /* OK. It is a subframe. Checkout the parent's loadtype. If the parent was
+   * loaded through a history mechanism, then get the SH entry for the child
+   * from the parent. This is done to restore frameset navigation while going
+   * back/forward. If the parent was loaded through any other loadType, set the
+   * child's loadType too accordingly, so that session history does not get
+   * confused.
+   */
+
+  // Get the parent's load type
+  uint32_t parentLoadType;
+  parentDS->GetLoadType(&parentLoadType);
+
+  if (!aContinueHandlingSubframeHistory) {
+    if (mozilla::SessionHistoryInParent()) {
+      if (nsDocShell::Cast(parentDS.get())->IsLoadingFromSessionHistory() &&
+          !GetCreatedDynamically()) {
+        if (XRE_IsContentProcess()) {
+          dom::ContentChild* contentChild = dom::ContentChild::GetSingleton();
+          nsCOMPtr<nsILoadGroup> loadGroup;
+          GetLoadGroup(getter_AddRefs(loadGroup));
+          if (contentChild && loadGroup && !mCheckingSessionHistory) {
+            RefPtr<Document> parentDoc = parentDS->GetDocument();
+            parentDoc->BlockOnload();
+            RefPtr<BrowsingContext> browsingContext = mBrowsingContext;
+            Maybe<uint64_t> currentLoadIdentifier =
+                mBrowsingContext->GetCurrentLoadIdentifier();
+            RefPtr<nsDocShellLoadState> loadState = aLoadState;
+            bool isNavigating = mIsNavigating;
+            RefPtr<StopDetector> stopDetector = new StopDetector();
+            loadGroup->AddRequest(stopDetector, nullptr);
+            // Need to set mCheckingSessionHistory so that
+            // GetIsAttemptingToNavigate() returns true.
+            mCheckingSessionHistory = true;
+
+            auto resolve =
+                [currentLoadIdentifier, browsingContext, parentDoc, loadState,
+                 isNavigating, loadGroup, stopDetector](
+                    mozilla::Maybe<LoadingSessionHistoryInfo>&& aResult) {
+                  RefPtr<nsDocShell> docShell =
+                      static_cast<nsDocShell*>(browsingContext->GetDocShell());
+                  auto unblockParent = MakeScopeExit(
+                      [loadGroup, stopDetector, parentDoc, docShell]() {
+                        if (docShell) {
+                          docShell->mCheckingSessionHistory = false;
+                        }
+                        loadGroup->RemoveRequest(stopDetector, nullptr, NS_OK);
+                        parentDoc->UnblockOnload(false);
+                      });
+
+                  if (!docShell || !docShell->mCheckingSessionHistory) {
+                    return;
+                  }
+
+                  if (stopDetector->Canceled()) {
+                    return;
+                  }
+                  if (currentLoadIdentifier ==
+                          browsingContext->GetCurrentLoadIdentifier() &&
+                      aResult.isSome()) {
+                    loadState->SetLoadingSessionHistoryInfo(aResult.value());
+                    // This is an initial subframe load from the session
+                    // history, index doesn't need to be updated.
+                    loadState->SetLoadIsFromSessionHistory(0, false);
+                  }
+
+                  // We got the results back from the parent process, call
+                  // LoadURI again with the possibly updated data.
+                  docShell->LoadURI(loadState, isNavigating, true);
+                };
+            auto reject = [loadGroup, stopDetector, browsingContext,
+                           parentDoc](mozilla::ipc::ResponseRejectReason) {
+              RefPtr<nsDocShell> docShell =
+                  static_cast<nsDocShell*>(browsingContext->GetDocShell());
+              if (docShell) {
+                docShell->mCheckingSessionHistory = false;
+              }
+              // In practise reject shouldn't be called ever.
+              loadGroup->RemoveRequest(stopDetector, nullptr, NS_OK);
+              parentDoc->UnblockOnload(false);
+            };
+            contentChild->SendGetLoadingSessionHistoryInfoFromParent(
+                mBrowsingContext, std::move(resolve), std::move(reject));
+            return true;
+          }
+        } else {
+          Maybe<LoadingSessionHistoryInfo> info;
+          mBrowsingContext->Canonical()->GetLoadingSessionHistoryInfoFromParent(
+              info);
+          if (info.isSome()) {
+            aLoadState->SetLoadingSessionHistoryInfo(info.value());
+            // This is an initial subframe load from the session
+            // history, index doesn't need to be updated.
+            aLoadState->SetLoadIsFromSessionHistory(0, false);
+          }
+        }
+      }
+    } else {
+      // Get the ShEntry for the child from the parent
+      nsCOMPtr<nsISHEntry> currentSH;
+      bool oshe = false;
+      parentDS->GetCurrentSHEntry(getter_AddRefs(currentSH), &oshe);
+      bool dynamicallyAddedChild = GetCreatedDynamically();
+
+      if (!dynamicallyAddedChild && !oshe && currentSH) {
+        // Only use the old SHEntry, if we're sure enough that
+        // it wasn't originally for some other frame.
+        nsCOMPtr<nsISHEntry> shEntry;
+        currentSH->GetChildSHEntryIfHasNoDynamicallyAddedChild(
+            mBrowsingContext->ChildOffset(), getter_AddRefs(shEntry));
+        if (shEntry) {
+          aLoadState->SetSHEntry(shEntry);
+        }
+      }
+    }
+  }
+
+  // Make some decisions on the child frame's loadType based on the
+  // parent's loadType, if the subframe hasn't loaded anything into it.
+  //
+  // In some cases privileged scripts may try to get the DOMWindow
+  // reference of this docshell before the loading starts, causing the
+  // initial about:blank content viewer being created and mCurrentURI being
+  // set. To handle this case we check if mCurrentURI is about:blank and
+  // currentSHEntry is null.
+  bool oshe = false;
+  nsCOMPtr<nsISHEntry> currentChildEntry;
+  GetCurrentSHEntry(getter_AddRefs(currentChildEntry), &oshe);
+
+  if (mCurrentURI && (!NS_IsAboutBlank(mCurrentURI) || currentChildEntry ||
+                      mLoadingEntry || mActiveEntry)) {
+    // This is a pre-existing subframe. If
+    // 1. The load of this frame was not originally initiated by session
+    //    history directly (i.e. (!shEntry) condition succeeded, but it can
+    //    still be a history load on parent which causes this frame being
+    //    loaded), which we checked with the above assert, and
+    // 2. mCurrentURI is not null, nor the initial about:blank,
+    // it is possible that a parent's onLoadHandler or even self's
+    // onLoadHandler is loading a new page in this child. Check parent's and
+    // self's busy flag and if it is set, we don't want this onLoadHandler
+    // load to get in to session history.
+    BusyFlags parentBusy = parentDS->GetBusyFlags();
+    BusyFlags selfBusy = GetBusyFlags();
+
+    if (parentBusy & BUSY_FLAGS_BUSY || selfBusy & BUSY_FLAGS_BUSY) {
+      aLoadState->SetLoadType(LOAD_NORMAL_REPLACE);
+      aLoadState->ClearLoadIsFromSessionHistory();
+    }
+    return false;
+  }
+
+  // This is a newly created frame. Check for exception cases first.
+  // By default the subframe will inherit the parent's loadType.
+  if (aLoadState->LoadIsFromSessionHistory() &&
+      (parentLoadType == LOAD_NORMAL || parentLoadType == LOAD_LINK)) {
+    // The parent was loaded normally. In this case, this *brand new*
+    // child really shouldn't have a SHEntry. If it does, it could be
+    // because the parent is replacing an existing frame with a new frame,
+    // in the onLoadHandler. We don't want this url to get into session
+    // history. Clear off shEntry, and set load type to
+    // LOAD_BYPASS_HISTORY.
+    bool inOnLoadHandler = false;
+    parentDS->GetIsExecutingOnLoadHandler(&inOnLoadHandler);
+    if (inOnLoadHandler) {
+      aLoadState->SetLoadType(LOAD_NORMAL_REPLACE);
+      aLoadState->ClearLoadIsFromSessionHistory();
+    }
+  } else if (parentLoadType == LOAD_REFRESH) {
+    // Clear shEntry. For refresh loads, we have to load
+    // what comes through the pipe, not what's in history.
+    aLoadState->ClearLoadIsFromSessionHistory();
+  } else if ((parentLoadType == LOAD_BYPASS_HISTORY) ||
+             (aLoadState->LoadIsFromSessionHistory() &&
+              ((parentLoadType & LOAD_CMD_HISTORY) ||
+               (parentLoadType == LOAD_RELOAD_NORMAL) ||
+               (parentLoadType == LOAD_RELOAD_CHARSET_CHANGE) ||
+               (parentLoadType == LOAD_RELOAD_CHARSET_CHANGE_BYPASS_CACHE) ||
+               (parentLoadType ==
+                LOAD_RELOAD_CHARSET_CHANGE_BYPASS_PROXY_AND_CACHE)))) {
+    // If the parent url, bypassed history or was loaded from
+    // history, pass on the parent's loadType to the new child
+    // frame too, so that the child frame will also
+    // avoid getting into history.
+    aLoadState->SetLoadType(parentLoadType);
+  } else if (parentLoadType == LOAD_ERROR_PAGE) {
+    // If the parent document is an error page, we don't
+    // want to update global/session history. However,
+    // this child frame is not an error page.
+    aLoadState->SetLoadType(LOAD_BYPASS_HISTORY);
+  } else if ((parentLoadType == LOAD_RELOAD_BYPASS_CACHE) ||
+             (parentLoadType == LOAD_RELOAD_BYPASS_PROXY) ||
+             (parentLoadType == LOAD_RELOAD_BYPASS_PROXY_AND_CACHE)) {
+    // the new frame should inherit the parent's load type so that it also
+    // bypasses the cache and/or proxy
+    aLoadState->SetLoadType(parentLoadType);
+  }
+
+  return false;
+}
+
+/*
+ * Reset state to a new content model within the current document and the
+ * document viewer. Called by the document before initiating an out of band
+ * document.write().
+ */
+NS_IMETHODIMP
+nsDocShell::PrepareForNewContentModel() {
+  // Clear out our form control state, because the state of controls
+  // in the pre-open() document should not affect the state of
+  // controls that are now going to be written.
+  SetLayoutHistoryState(nullptr);
+  mEODForCurrentDocument = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::FirePageHideNotification(bool aIsUnload) {
+  FirePageHideNotificationInternal(aIsUnload, false);
+  return NS_OK;
+}
+
+void nsDocShell::FirePageHideNotificationInternal(
+    bool aIsUnload, bool aSkipCheckingDynEntries) {
+  if (mDocumentViewer && !mFiredUnloadEvent) {
+    // Keep an explicit reference since calling PageHide could release
+    // mDocumentViewer
+    nsCOMPtr<nsIDocumentViewer> viewer(mDocumentViewer);
+    mFiredUnloadEvent = true;
+
+    if (mTiming) {
+      mTiming->NotifyUnloadEventStart();
+    }
+
+    viewer->PageHide(aIsUnload);
+
+    if (mTiming) {
+      mTiming->NotifyUnloadEventEnd();
+    }
+
+    AutoTArray<nsCOMPtr<nsIDocShell>, 8> kids;
+    uint32_t n = mChildList.Length();
+    kids.SetCapacity(n);
+    for (uint32_t i = 0; i < n; i++) {
+      kids.AppendElement(do_QueryInterface(ChildAt(i)));
+    }
+
+    n = kids.Length();
+    for (uint32_t i = 0; i < n; ++i) {
+      RefPtr<nsDocShell> child = static_cast<nsDocShell*>(kids[i].get());
+      if (child) {
+        // Skip checking dynamic subframe entries in our children.
+        child->FirePageHideNotificationInternal(aIsUnload, true);
+      }
+    }
+
+    // If the document is unloading, remove all dynamic subframe entries.
+    if (aIsUnload && !aSkipCheckingDynEntries) {
+      RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+      if (rootSH) {
+        MOZ_LOG(
+            gSHLog, LogLevel::Debug,
+            ("nsDocShell %p unloading, remove dynamic subframe entries", this));
+        if (mozilla::SessionHistoryInParent()) {
+          if (mActiveEntry) {
+            mBrowsingContext->RemoveDynEntriesFromActiveSessionHistoryEntry();
+          }
+          MOZ_LOG(gSHLog, LogLevel::Debug,
+                  ("nsDocShell %p unloading, no active entries", this));
+        } else if (mOSHE) {
+          int32_t index = rootSH->Index();
+          rootSH->LegacySHistory()->RemoveDynEntries(index, mOSHE);
+        }
+      }
+    }
+
+    // Now make sure our editor, if any, is detached before we go
+    // any farther.
+    DetachEditorFromWindow();
+  }
+}
+
+void nsDocShell::ThawFreezeNonRecursive(bool aThaw) {
+  MOZ_ASSERT(mozilla::BFCacheInParent());
+
+  if (!mScriptGlobal) {
+    return;
+  }
+
+  if (RefPtr<nsGlobalWindowInner> inner =
+          nsGlobalWindowInner::Cast(mScriptGlobal->GetCurrentInnerWindow())) {
+    if (aThaw) {
+      inner->Thaw(false);
+    } else {
+      inner->Freeze(false);
+    }
+  }
+}
+
+void nsDocShell::FirePageHideShowNonRecursive(bool aShow) {
+  MOZ_ASSERT(mozilla::BFCacheInParent());
+
+  if (!mDocumentViewer) {
+    return;
+  }
+
+  // Emulate what non-SHIP BFCache does too. In pageshow case
+  // add and remove a request and before that call SetCurrentURI to get
+  // the location change notification.
+  // For pagehide, set mFiredUnloadEvent to true, so that unload doesn't fire.
+  nsCOMPtr<nsIDocumentViewer> viewer(mDocumentViewer);
+  if (aShow) {
+    viewer->SetIsHidden(false);
+    mRefreshURIList = std::move(mBFCachedRefreshURIList);
+    RefreshURIFromQueue();
+    mFiredUnloadEvent = false;
+    RefPtr<Document> doc = viewer->GetDocument();
+    if (doc) {
+      doc->NotifyActivityChanged();
+      nsCOMPtr<nsPIDOMWindowInner> inner =
+          mScriptGlobal ? mScriptGlobal->GetCurrentInnerWindow() : nullptr;
+      if (mBrowsingContext->IsTop()) {
+        doc->NotifyPossibleTitleChange(false);
+        doc->SetLoadingOrRestoredFromBFCacheTimeStampToNow();
+        if (inner) {
+          // Now that we have found the inner window of the page restored
+          // from the history, we have to make sure that
+          // performance.navigation.type is 2.
+          // Traditionally this type change has been done to the top level page
+          // only.
+          Performance* performance = inner->GetPerformance();
+          if (performance) {
+            performance->GetDOMTiming()->NotifyRestoreStart();
+          }
+        }
+      }
+
+      nsCOMPtr<nsIChannel> channel = doc->GetChannel();
+      if (channel) {
+        SetLoadType(LOAD_HISTORY);
+        mEODForCurrentDocument = false;
+        mIsRestoringDocument = true;
+        mLoadGroup->AddRequest(channel, nullptr);
+        SetCurrentURI(doc->GetDocumentURI(), channel,
+                      /* aFireOnLocationChange */ true,
+                      /* aIsInitialAboutBlank */ false,
+                      /* aLocationFlags */ 0);
+        mLoadGroup->RemoveRequest(channel, nullptr, NS_OK);
+        mIsRestoringDocument = false;
+      }
+      RefPtr<PresShell> presShell = GetPresShell();
+      if (presShell) {
+        presShell->Thaw(false);
+      }
+
+      if (inner) {
+        inner->FireDelayedDOMEvents(false);
+      }
+    }
+  } else if (!mFiredUnloadEvent) {
+    // XXXBFCache check again that the page can enter bfcache.
+    // XXXBFCache should mTiming->NotifyUnloadEventStart()/End() be called here?
+
+    if (mRefreshURIList) {
+      RefreshURIToQueue();
+      mBFCachedRefreshURIList = std::move(mRefreshURIList);
+    } else {
+      // If Stop was called, the list was moved to mSavedRefreshURIList after
+      // calling SuspendRefreshURIs, which calls RefreshURIToQueue.
+      mBFCachedRefreshURIList = std::move(mSavedRefreshURIList);
+    }
+
+    mFiredUnloadEvent = true;
+    viewer->PageHide(false);
+
+    RefPtr<PresShell> presShell = GetPresShell();
+    if (presShell) {
+      presShell->Freeze(false);
+    }
+  }
+}
+
+nsresult nsDocShell::Dispatch(already_AddRefed<nsIRunnable>&& aRunnable) {
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+  if (NS_WARN_IF(!GetWindow())) {
+    // Window should only be unavailable after destroyed.
+    MOZ_ASSERT(mIsBeingDestroyed);
+    return NS_ERROR_FAILURE;
+  }
+  return SchedulerGroup::Dispatch(runnable.forget());
+}
+
+NS_IMETHODIMP
+nsDocShell::DispatchLocationChangeEvent() {
+  return Dispatch(NewRunnableMethod("nsDocShell::FireDummyOnLocationChange",
+                                    this,
+                                    &nsDocShell::FireDummyOnLocationChange));
+}
+
+NS_IMETHODIMP
+nsDocShell::StartDelayedAutoplayMediaComponents() {
+  RefPtr<nsPIDOMWindowOuter> outerWindow = GetWindow();
+  if (outerWindow) {
+    outerWindow->ActivateMediaComponents();
+  }
+  return NS_OK;
+}
+
+bool nsDocShell::MaybeInitTiming() {
+  if (mTiming && !mBlankTiming) {
+    return false;
+  }
+
+  bool canBeReset = false;
+
+  if (mScriptGlobal && mBlankTiming) {
+    nsPIDOMWindowInner* innerWin = mScriptGlobal->GetCurrentInnerWindow();
+    if (innerWin && innerWin->GetPerformance()) {
+      mTiming = innerWin->GetPerformance()->GetDOMTiming();
+      mBlankTiming = false;
+    }
+  }
+
+  if (!mTiming) {
+    mTiming = new nsDOMNavigationTiming(this);
+    canBeReset = true;
+  }
+
+  mTiming->NotifyNavigationStart(
+      mBrowsingContext->IsActive()
+          ? nsDOMNavigationTiming::DocShellState::eActive
+          : nsDOMNavigationTiming::DocShellState::eInactive);
+
+  return canBeReset;
+}
+
+void nsDocShell::MaybeResetInitTiming(bool aReset) {
+  if (aReset) {
+    mTiming = nullptr;
+  }
+}
+
+nsDOMNavigationTiming* nsDocShell::GetNavigationTiming() const {
+  return mTiming;
+}
+
+nsPresContext* nsDocShell::GetEldestPresContext() {
+  nsIDocumentViewer* viewer = mDocumentViewer;
+  while (viewer) {
+    nsIDocumentViewer* prevViewer = viewer->GetPreviousViewer();
+    if (!prevViewer) {
+      return viewer->GetPresContext();
+    }
+    viewer = prevViewer;
+  }
+
+  return nullptr;
+}
+
+nsPresContext* nsDocShell::GetPresContext() {
+  if (!mDocumentViewer) {
+    return nullptr;
+  }
+
+  return mDocumentViewer->GetPresContext();
+}
+
+PresShell* nsDocShell::GetPresShell() {
+  nsPresContext* presContext = GetPresContext();
+  return presContext ? presContext->GetPresShell() : nullptr;
+}
+
+PresShell* nsDocShell::GetEldestPresShell() {
+  nsPresContext* presContext = GetEldestPresContext();
+
+  if (presContext) {
+    return presContext->GetPresShell();
+  }
+
+  return nullptr;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDocViewer(nsIDocumentViewer** aDocumentViewer) {
+  NS_ENSURE_ARG_POINTER(aDocumentViewer);
+
+  *aDocumentViewer = mDocumentViewer;
+  NS_IF_ADDREF(*aDocumentViewer);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetOuterWindowID(uint64_t* aWindowID) {
+  *aWindowID = mContentWindowID;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetChromeEventHandler(EventTarget* aChromeEventHandler) {
+  mChromeEventHandler = aChromeEventHandler;
+
+  if (mScriptGlobal) {
+    mScriptGlobal->SetChromeEventHandler(mChromeEventHandler);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetChromeEventHandler(EventTarget** aChromeEventHandler) {
+  NS_ENSURE_ARG_POINTER(aChromeEventHandler);
+  RefPtr<EventTarget> handler = mChromeEventHandler;
+  handler.forget(aChromeEventHandler);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetCurrentURIForSessionStore(nsIURI* aURI) {
+  // Note that securityUI will set STATE_IS_INSECURE, even if
+  // the scheme of |aURI| is "https".
+  SetCurrentURI(aURI, nullptr,
+                /* aFireOnLocationChange */
+                true,
+                /* aIsInitialAboutBlank */
+                false,
+                /* aLocationFlags */
+                nsIWebProgressListener::LOCATION_CHANGE_SESSION_STORE);
+  return NS_OK;
+}
+
+bool nsDocShell::SetCurrentURI(nsIURI* aURI, nsIRequest* aRequest,
+                               bool aFireOnLocationChange,
+                               bool aIsInitialAboutBlank,
+                               uint32_t aLocationFlags) {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  MOZ_LOG(gDocShellLeakLog, LogLevel::Debug,
+          ("DOCSHELL %p SetCurrentURI %s\n", this,
+           aURI ? aURI->GetSpecOrDefault().get() : ""));
+
+  // We don't want to send a location change when we're displaying an error
+  // page, and we don't want to change our idea of "current URI" either
+  if (mLoadType == LOAD_ERROR_PAGE) {
+    return false;
+  }
+
+  bool uriIsEqual = false;
+  if (!mCurrentURI || !aURI ||
+      NS_FAILED(mCurrentURI->Equals(aURI, &uriIsEqual)) || !uriIsEqual) {
+    mTitleValidForCurrentURI = false;
+  }
+
+  SetCurrentURIInternal(aURI);
+
+#ifdef DEBUG
+  mLastOpenedURI = aURI;
+#endif
+
+  if (!NS_IsAboutBlank(mCurrentURI)) {
+    mHasLoadedNonBlankURI = true;
+  }
+
+  // Don't fire onLocationChange when creating a subframe's initial about:blank
+  // document, as this can happen when it's not safe for us to run script.
+  if (aIsInitialAboutBlank && !mHasLoadedNonBlankURI &&
+      !mBrowsingContext->IsTop()) {
+    MOZ_ASSERT(!aRequest && aLocationFlags == 0);
+    return false;
+  }
+
+  MOZ_ASSERT(nsContentUtils::IsSafeToRunScript());
+
+  if (aFireOnLocationChange) {
+    FireOnLocationChange(this, aRequest, aURI, aLocationFlags);
+  }
+  return !aFireOnLocationChange;
+}
+
+void nsDocShell::SetCurrentURIInternal(nsIURI* aURI) {
+  mCurrentURI = aURI;
+  if (mBrowsingContext) {
+    mBrowsingContext->ClearCachedValuesOfLocations();
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCharset(nsACString& aCharset) {
+  aCharset.Truncate();
+
+  PresShell* presShell = GetPresShell();
+  NS_ENSURE_TRUE(presShell, NS_ERROR_FAILURE);
+  Document* doc = presShell->GetDocument();
+  NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
+  doc->GetDocumentCharacterSet()->Name(aCharset);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::ForceEncodingDetection() {
+  nsCOMPtr<nsIDocumentViewer> viewer;
+  GetDocViewer(getter_AddRefs(viewer));
+  if (!viewer) {
+    return NS_OK;
+  }
+
+  Document* doc = viewer->GetDocument();
+  if (!doc || doc->WillIgnoreCharsetOverride()) {
+    return NS_OK;
+  }
+
+  mForcedAutodetection = true;
+
+  nsIURI* url = doc->GetOriginalURI();
+  bool isFileURL = url && SchemeIsFile(url);
+
+  int32_t charsetSource = doc->GetDocumentCharacterSetSource();
+  auto encoding = doc->GetDocumentCharacterSet();
+  // AsHTMLDocument is valid, because we called
+  // WillIgnoreCharsetOverride() above.
+  if (doc->AsHTMLDocument()->IsPlainText()) {
+    switch (charsetSource) {
+      case kCharsetFromInitialAutoDetectionASCII:
+        // Deliberately no final version
+        LOGCHARSETMENU(("TEXT:UnlabeledAscii"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::UnlabeledAscii);
+        break;
+      case kCharsetFromInitialAutoDetectionWouldNotHaveBeenUTF8Generic:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8Generic:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8GenericInitialWasASCII:
+      case kCharsetFromInitialAutoDetectionWouldNotHaveBeenUTF8Content:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8Content:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8ContentInitialWasASCII:
+        LOGCHARSETMENU(("TEXT:UnlabeledNonUtf8"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::
+                UnlabeledNonUtf8);
+        break;
+      case kCharsetFromInitialAutoDetectionWouldNotHaveBeenUTF8DependedOnTLD:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8DependedOnTLD:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8DependedOnTLDInitialWasASCII:
+        LOGCHARSETMENU(("TEXT:UnlabeledNonUtf8TLD"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::
+                UnlabeledNonUtf8TLD);
+        break;
+      case kCharsetFromInitialAutoDetectionWouldHaveBeenUTF8:
+      case kCharsetFromFinalAutoDetectionWouldHaveBeenUTF8InitialWasASCII:
+        LOGCHARSETMENU(("TEXT:UnlabeledUtf8"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::UnlabeledUtf8);
+        break;
+      case kCharsetFromChannel:
+        if (encoding == UTF_8_ENCODING) {
+          LOGCHARSETMENU(("TEXT:ChannelUtf8"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::ChannelUtf8);
+        } else {
+          LOGCHARSETMENU(("TEXT:ChannelNonUtf8"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::
+                  ChannelNonUtf8);
+        }
+        break;
+      default:
+        LOGCHARSETMENU(("TEXT:Bug"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_TEXT::Bug);
+        break;
+    }
+  } else {
+    switch (charsetSource) {
+      case kCharsetFromInitialAutoDetectionASCII:
+        // Deliberately no final version
+        LOGCHARSETMENU(("HTML:UnlabeledAscii"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::UnlabeledAscii);
+        break;
+      case kCharsetFromInitialAutoDetectionWouldNotHaveBeenUTF8Generic:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8Generic:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8GenericInitialWasASCII:
+      case kCharsetFromInitialAutoDetectionWouldNotHaveBeenUTF8Content:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8Content:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8ContentInitialWasASCII:
+        LOGCHARSETMENU(("HTML:UnlabeledNonUtf8"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::
+                UnlabeledNonUtf8);
+        break;
+      case kCharsetFromInitialAutoDetectionWouldNotHaveBeenUTF8DependedOnTLD:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8DependedOnTLD:
+      case kCharsetFromFinalAutoDetectionWouldNotHaveBeenUTF8DependedOnTLDInitialWasASCII:
+        LOGCHARSETMENU(("HTML:UnlabeledNonUtf8TLD"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::
+                UnlabeledNonUtf8TLD);
+        break;
+      case kCharsetFromInitialAutoDetectionWouldHaveBeenUTF8:
+      case kCharsetFromFinalAutoDetectionWouldHaveBeenUTF8InitialWasASCII:
+        LOGCHARSETMENU(("HTML:UnlabeledUtf8"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::UnlabeledUtf8);
+        break;
+      case kCharsetFromChannel:
+        if (encoding == UTF_8_ENCODING) {
+          LOGCHARSETMENU(("HTML:ChannelUtf8"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::ChannelUtf8);
+        } else {
+          LOGCHARSETMENU(("HTML:ChannelNonUtf8"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::
+                  ChannelNonUtf8);
+        }
+        break;
+      case kCharsetFromXmlDeclaration:
+      case kCharsetFromMetaTag:
+        if (isFileURL) {
+          LOGCHARSETMENU(("HTML:LocalLabeled"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::LocalLabeled);
+        } else if (encoding == UTF_8_ENCODING) {
+          LOGCHARSETMENU(("HTML:MetaUtf8"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::InternalUtf8);
+        } else {
+          LOGCHARSETMENU(("HTML:MetaNonUtf8"));
+          Telemetry::AccumulateCategorical(
+              Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::
+                  InternalNonUtf8);
+        }
+        break;
+      default:
+        LOGCHARSETMENU(("HTML:Bug"));
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_ENCODING_OVERRIDE_SITUATION_HTML::Bug);
+        break;
+    }
+  }
+  return NS_OK;
+}
+
+void nsDocShell::SetParentCharset(const Encoding*& aCharset,
+                                  int32_t aCharsetSource,
+                                  nsIPrincipal* aPrincipal) {
+  mParentCharset = aCharset;
+  mParentCharsetSource = aCharsetSource;
+  mParentCharsetPrincipal = aPrincipal;
+}
+
+void nsDocShell::GetParentCharset(const Encoding*& aCharset,
+                                  int32_t* aCharsetSource,
+                                  nsIPrincipal** aPrincipal) {
+  aCharset = mParentCharset;
+  *aCharsetSource = mParentCharsetSource;
+  NS_IF_ADDREF(*aPrincipal = mParentCharsetPrincipal);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetHasTrackingContentBlocked(Promise** aPromise) {
+  MOZ_ASSERT(aPromise);
+
+  ErrorResult rv;
+  RefPtr<Document> doc(GetDocument());
+  RefPtr<Promise> retPromise = Promise::Create(doc->GetOwnerGlobal(), rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  // Retrieve the document's content blocking events from the parent process.
+  RefPtr<Document::GetContentBlockingEventsPromise> promise =
+      doc->GetContentBlockingEvents();
+  if (promise) {
+    promise->Then(
+        GetCurrentSerialEventTarget(), __func__,
+        [retPromise](const Document::GetContentBlockingEventsPromise::
+                         ResolveOrRejectValue& aValue) {
+          if (aValue.IsResolve()) {
+            bool has = aValue.ResolveValue() &
+                       nsIWebProgressListener::STATE_BLOCKED_TRACKING_CONTENT;
+            retPromise->MaybeResolve(has);
+          } else {
+            retPromise->MaybeResolve(false);
+          }
+        });
+  } else {
+    retPromise->MaybeResolve(false);
+  }
+
+  retPromise.forget(aPromise);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCssErrorReportingEnabled(bool* aEnabled) {
+  MOZ_ASSERT(aEnabled);
+  *aEnabled = mCSSErrorReportingEnabled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetCssErrorReportingEnabled(bool aEnabled) {
+  mCSSErrorReportingEnabled = aEnabled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetUsePrivateBrowsing(bool* aUsePrivateBrowsing) {
+  NS_ENSURE_ARG_POINTER(aUsePrivateBrowsing);
+  return mBrowsingContext->GetUsePrivateBrowsing(aUsePrivateBrowsing);
+}
+
+void nsDocShell::NotifyPrivateBrowsingChanged() {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mPrivacyObservers);
+  while (iter.HasMore()) {
+    nsWeakPtr ref = iter.GetNext();
+    nsCOMPtr<nsIPrivacyTransitionObserver> obs = do_QueryReferent(ref);
+    if (!obs) {
+      iter.Remove();
+    } else {
+      obs->PrivateModeChanged(UsePrivateBrowsing());
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::SetUsePrivateBrowsing(bool aUsePrivateBrowsing) {
+  return mBrowsingContext->SetUsePrivateBrowsing(aUsePrivateBrowsing);
+}
+
+NS_IMETHODIMP
+nsDocShell::SetPrivateBrowsing(bool aUsePrivateBrowsing) {
+  return mBrowsingContext->SetPrivateBrowsing(aUsePrivateBrowsing);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetHasLoadedNonBlankURI(bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+
+  *aResult = mHasLoadedNonBlankURI;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetUseRemoteTabs(bool* aUseRemoteTabs) {
+  NS_ENSURE_ARG_POINTER(aUseRemoteTabs);
+  return mBrowsingContext->GetUseRemoteTabs(aUseRemoteTabs);
+}
+
+NS_IMETHODIMP
+nsDocShell::SetRemoteTabs(bool aUseRemoteTabs) {
+  return mBrowsingContext->SetRemoteTabs(aUseRemoteTabs);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetUseRemoteSubframes(bool* aUseRemoteSubframes) {
+  NS_ENSURE_ARG_POINTER(aUseRemoteSubframes);
+  return mBrowsingContext->GetUseRemoteSubframes(aUseRemoteSubframes);
+}
+
+NS_IMETHODIMP
+nsDocShell::SetRemoteSubframes(bool aUseRemoteSubframes) {
+  return mBrowsingContext->SetRemoteSubframes(aUseRemoteSubframes);
+}
+
+NS_IMETHODIMP
+nsDocShell::AddWeakPrivacyTransitionObserver(
+    nsIPrivacyTransitionObserver* aObserver) {
+  nsWeakPtr weakObs = do_GetWeakReference(aObserver);
+  if (!weakObs) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  mPrivacyObservers.AppendElement(weakObs);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::AddWeakReflowObserver(nsIReflowObserver* aObserver) {
+  nsWeakPtr weakObs = do_GetWeakReference(aObserver);
+  if (!weakObs) {
+    return NS_ERROR_FAILURE;
+  }
+  mReflowObservers.AppendElement(weakObs);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::RemoveWeakReflowObserver(nsIReflowObserver* aObserver) {
+  nsWeakPtr obs = do_GetWeakReference(aObserver);
+  return mReflowObservers.RemoveElement(obs) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsDocShell::NotifyReflowObservers(bool aInterruptible,
+                                  DOMHighResTimeStamp aStart,
+                                  DOMHighResTimeStamp aEnd) {
+  nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mReflowObservers);
+  while (iter.HasMore()) {
+    nsWeakPtr ref = iter.GetNext();
+    nsCOMPtr<nsIReflowObserver> obs = do_QueryReferent(ref);
+    if (!obs) {
+      iter.Remove();
+    } else if (aInterruptible) {
+      obs->ReflowInterruptible(aStart, aEnd);
+    } else {
+      obs->Reflow(aStart, aEnd);
+    }
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowMetaRedirects(bool* aReturn) {
+  NS_ENSURE_ARG_POINTER(aReturn);
+
+  *aReturn = mAllowMetaRedirects;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowMetaRedirects(bool aValue) {
+  mAllowMetaRedirects = aValue;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowSubframes(bool* aAllowSubframes) {
+  NS_ENSURE_ARG_POINTER(aAllowSubframes);
+
+  *aAllowSubframes = mAllowSubframes;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowSubframes(bool aAllowSubframes) {
+  mAllowSubframes = aAllowSubframes;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowImages(bool* aAllowImages) {
+  NS_ENSURE_ARG_POINTER(aAllowImages);
+
+  *aAllowImages = mAllowImages;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowImages(bool aAllowImages) {
+  mAllowImages = aAllowImages;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowMedia(bool* aAllowMedia) {
+  *aAllowMedia = mAllowMedia;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowMedia(bool aAllowMedia) {
+  mAllowMedia = aAllowMedia;
+
+  // Mute or unmute audio contexts attached to the inner window.
+  if (mScriptGlobal) {
+    if (nsPIDOMWindowInner* innerWin = mScriptGlobal->GetCurrentInnerWindow()) {
+      if (aAllowMedia) {
+        innerWin->UnmuteAudioContexts();
+      } else {
+        innerWin->MuteAudioContexts();
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowDNSPrefetch(bool* aAllowDNSPrefetch) {
+  *aAllowDNSPrefetch = mAllowDNSPrefetch;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowDNSPrefetch(bool aAllowDNSPrefetch) {
+  mAllowDNSPrefetch = aAllowDNSPrefetch;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowWindowControl(bool* aAllowWindowControl) {
+  *aAllowWindowControl = mAllowWindowControl;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowWindowControl(bool aAllowWindowControl) {
+  mAllowWindowControl = aAllowWindowControl;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowContentRetargeting(bool* aAllowContentRetargeting) {
+  *aAllowContentRetargeting = mBrowsingContext->GetAllowContentRetargeting();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowContentRetargeting(bool aAllowContentRetargeting) {
+  BrowsingContext::Transaction txn;
+  txn.SetAllowContentRetargeting(aAllowContentRetargeting);
+  txn.SetAllowContentRetargetingOnChildren(aAllowContentRetargeting);
+  return txn.Commit(mBrowsingContext);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowContentRetargetingOnChildren(
+    bool* aAllowContentRetargetingOnChildren) {
+  *aAllowContentRetargetingOnChildren =
+      mBrowsingContext->GetAllowContentRetargetingOnChildren();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowContentRetargetingOnChildren(
+    bool aAllowContentRetargetingOnChildren) {
+  return mBrowsingContext->SetAllowContentRetargetingOnChildren(
+      aAllowContentRetargetingOnChildren);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetMayEnableCharacterEncodingMenu(
+    bool* aMayEnableCharacterEncodingMenu) {
+  *aMayEnableCharacterEncodingMenu = false;
+  if (!mDocumentViewer) {
+    return NS_OK;
+  }
+  Document* doc = mDocumentViewer->GetDocument();
+  if (!doc) {
+    return NS_OK;
+  }
+  if (doc->WillIgnoreCharsetOverride()) {
+    return NS_OK;
+  }
+
+  *aMayEnableCharacterEncodingMenu = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllDocShellsInSubtree(int32_t aItemType,
+                                     DocShellEnumeratorDirection aDirection,
+                                     nsTArray<RefPtr<nsIDocShell>>& aResult) {
+  aResult.Clear();
+
+  nsDocShellEnumerator docShellEnum(
+      (aDirection == ENUMERATE_FORWARDS)
+          ? nsDocShellEnumerator::EnumerationDirection::Forwards
+          : nsDocShellEnumerator::EnumerationDirection::Backwards,
+      aItemType, *this);
+
+  nsresult rv = docShellEnum.BuildDocShellArray(aResult);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAppType(AppType* aAppType) {
+  *aAppType = mAppType;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAppType(AppType aAppType) {
+  mAppType = aAppType;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAllowAuth(bool* aAllowAuth) {
+  *aAllowAuth = mAllowAuth;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetAllowAuth(bool aAllowAuth) {
+  mAllowAuth = aAllowAuth;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetZoom(float* aZoom) {
+  NS_ENSURE_ARG_POINTER(aZoom);
+  *aZoom = 1.0f;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetZoom(float aZoom) { return NS_ERROR_NOT_IMPLEMENTED; }
+
+NS_IMETHODIMP
+nsDocShell::GetBusyFlags(BusyFlags* aBusyFlags) {
+  NS_ENSURE_ARG_POINTER(aBusyFlags);
+
+  *aBusyFlags = mBusyFlags;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::TabToTreeOwner(bool aForward, bool aForDocumentNavigation,
+                           bool* aTookFocus) {
+  NS_ENSURE_ARG_POINTER(aTookFocus);
+
+  nsCOMPtr<nsIWebBrowserChromeFocus> chromeFocus = do_GetInterface(mTreeOwner);
+  if (chromeFocus) {
+    if (aForward) {
+      *aTookFocus =
+          NS_SUCCEEDED(chromeFocus->FocusNextElement(aForDocumentNavigation));
+    } else {
+      *aTookFocus =
+          NS_SUCCEEDED(chromeFocus->FocusPrevElement(aForDocumentNavigation));
+    }
+  } else {
+    *aTookFocus = false;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetLoadURIDelegate(nsILoadURIDelegate** aLoadURIDelegate) {
+  nsCOMPtr<nsILoadURIDelegate> delegate = GetLoadURIDelegate();
+  delegate.forget(aLoadURIDelegate);
+  return NS_OK;
+}
+
+already_AddRefed<nsILoadURIDelegate> nsDocShell::GetLoadURIDelegate() {
+  if (nsCOMPtr<nsILoadURIDelegate> result =
+          do_QueryActor("LoadURIDelegate", GetDocument())) {
+    return result.forget();
+  }
+
+  return nullptr;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetUseErrorPages(bool* aUseErrorPages) {
+  *aUseErrorPages = mBrowsingContext->GetUseErrorPages();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetUseErrorPages(bool aUseErrorPages) {
+  return mBrowsingContext->SetUseErrorPages(aUseErrorPages);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetPreviousEntryIndex(int32_t* aPreviousEntryIndex) {
+  *aPreviousEntryIndex = mPreviousEntryIndex;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetLoadedEntryIndex(int32_t* aLoadedEntryIndex) {
+  *aLoadedEntryIndex = mLoadedEntryIndex;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::HistoryPurged(int32_t aNumEntries) {
+  // These indices are used for fastback cache eviction, to determine
+  // which session history entries are candidates for content viewer
+  // eviction.  We need to adjust by the number of entries that we
+  // just purged from history, so that we look at the right session history
+  // entries during eviction.
+  mPreviousEntryIndex = std::max(-1, mPreviousEntryIndex - aNumEntries);
+  mLoadedEntryIndex = std::max(0, mLoadedEntryIndex - aNumEntries);
+
+  for (auto* child : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> shell = do_QueryObject(child);
+    if (shell) {
+      shell->HistoryPurged(aNumEntries);
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::HistoryEntryRemoved(int32_t aIndex) {
+  // These indices are used for fastback cache eviction, to determine
+  // which session history entries are candidates for content viewer
+  // eviction.  We need to adjust by the number of entries that we
+  // just purged from history, so that we look at the right session history
+  // entries during eviction.
+  if (aIndex == mPreviousEntryIndex) {
+    mPreviousEntryIndex = -1;
+  } else if (aIndex < mPreviousEntryIndex) {
+    --mPreviousEntryIndex;
+  }
+  if (mLoadedEntryIndex == aIndex) {
+    mLoadedEntryIndex = 0;
+  } else if (aIndex < mLoadedEntryIndex) {
+    --mLoadedEntryIndex;
+  }
+
+  for (auto* child : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> shell = do_QueryObject(child);
+    if (shell) {
+      static_cast<nsDocShell*>(shell.get())->HistoryEntryRemoved(aIndex);
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::Now(DOMHighResTimeStamp* aWhen) {
+  *aWhen = (TimeStamp::Now() - TimeStamp::ProcessCreation()).ToMilliseconds();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetWindowDraggingAllowed(bool aValue) {
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
+  if (!aValue && mItemType == typeChrome && !parent) {
+    // Window dragging is always allowed for top level
+    // chrome docshells.
+    return NS_ERROR_FAILURE;
+  }
+  mWindowDraggingAllowed = aValue;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetWindowDraggingAllowed(bool* aValue) {
+  // window dragging regions in CSS (-moz-window-drag:drag)
+  // can be slow. Default behavior is to only allow it for
+  // chrome top level windows.
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
+  if (mItemType == typeChrome && !parent) {
+    // Top level chrome window
+    *aValue = true;
+  } else {
+    *aValue = mWindowDraggingAllowed;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCurrentDocumentChannel(nsIChannel** aResult) {
+  NS_IF_ADDREF(*aResult = GetCurrentDocChannel());
+  return NS_OK;
+}
+
+nsIChannel* nsDocShell::GetCurrentDocChannel() {
+  if (mDocumentViewer) {
+    Document* doc = mDocumentViewer->GetDocument();
+    if (doc) {
+      return doc->GetChannel();
+    }
+  }
+  return nullptr;
+}
+
+NS_IMETHODIMP
+nsDocShell::AddWeakScrollObserver(nsIScrollObserver* aObserver) {
+  nsWeakPtr weakObs = do_GetWeakReference(aObserver);
+  if (!weakObs) {
+    return NS_ERROR_FAILURE;
+  }
+  mScrollObservers.AppendElement(weakObs);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::RemoveWeakScrollObserver(nsIScrollObserver* aObserver) {
+  nsWeakPtr obs = do_GetWeakReference(aObserver);
+  return mScrollObservers.RemoveElement(obs) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+void nsDocShell::NotifyAsyncPanZoomStarted() {
+  nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mScrollObservers);
+  while (iter.HasMore()) {
+    nsWeakPtr ref = iter.GetNext();
+    nsCOMPtr<nsIScrollObserver> obs = do_QueryReferent(ref);
+    if (obs) {
+      obs->AsyncPanZoomStarted();
+    } else {
+      iter.Remove();
+    }
+  }
+}
+
+void nsDocShell::NotifyAsyncPanZoomStopped() {
+  nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mScrollObservers);
+  while (iter.HasMore()) {
+    nsWeakPtr ref = iter.GetNext();
+    nsCOMPtr<nsIScrollObserver> obs = do_QueryReferent(ref);
+    if (obs) {
+      obs->AsyncPanZoomStopped();
+    } else {
+      iter.Remove();
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::NotifyScrollObservers() {
+  nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mScrollObservers);
+  while (iter.HasMore()) {
+    nsWeakPtr ref = iter.GetNext();
+    nsCOMPtr<nsIScrollObserver> obs = do_QueryReferent(ref);
+    if (obs) {
+      obs->ScrollPositionChanged();
+    } else {
+      iter.Remove();
+    }
+  }
+  return NS_OK;
+}
+
+//*****************************************************************************
+// nsDocShell::nsIDocShellTreeItem
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::GetName(nsAString& aName) {
+  aName = mBrowsingContext->Name();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetName(const nsAString& aName) {
+  return mBrowsingContext->SetName(aName);
+}
+
+NS_IMETHODIMP
+nsDocShell::NameEquals(const nsAString& aName, bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+  *aResult = mBrowsingContext->NameEquals(aName);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCustomUserAgent(nsAString& aCustomUserAgent) {
+  mBrowsingContext->GetCustomUserAgent(aCustomUserAgent);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetCustomUserAgent(const nsAString& aCustomUserAgent) {
+  if (mWillChangeProcess) {
+    NS_WARNING("SetCustomUserAgent: Process is changing. Ignoring set");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mBrowsingContext->SetCustomUserAgent(aCustomUserAgent);
+}
+
+NS_IMETHODIMP
+nsDocShell::ClearCachedPlatform() {
+  nsCOMPtr<nsPIDOMWindowInner> win =
+      mScriptGlobal ? mScriptGlobal->GetCurrentInnerWindow() : nullptr;
+  if (win) {
+    Navigator* navigator = win->Navigator();
+    if (navigator) {
+      navigator->ClearPlatformCache();
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::ClearCachedUserAgent() {
+  nsCOMPtr<nsPIDOMWindowInner> win =
+      mScriptGlobal ? mScriptGlobal->GetCurrentInnerWindow() : nullptr;
+  if (win) {
+    Navigator* navigator = win->Navigator();
+    if (navigator) {
+      navigator->ClearUserAgentCache();
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetMetaViewportOverride(
+    MetaViewportOverride* aMetaViewportOverride) {
+  NS_ENSURE_ARG_POINTER(aMetaViewportOverride);
+
+  *aMetaViewportOverride = mMetaViewportOverride;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetMetaViewportOverride(
+    MetaViewportOverride aMetaViewportOverride) {
+  // We don't have a way to verify this coming from Javascript, so this check is
+  // still needed.
+  if (!(aMetaViewportOverride == META_VIEWPORT_OVERRIDE_NONE ||
+        aMetaViewportOverride == META_VIEWPORT_OVERRIDE_ENABLED ||
+        aMetaViewportOverride == META_VIEWPORT_OVERRIDE_DISABLED)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  mMetaViewportOverride = aMetaViewportOverride;
+
+  // Inform our presShell that it needs to re-check its need for a viewport
+  // override.
+  if (RefPtr<PresShell> presShell = GetPresShell()) {
+    presShell->MaybeRecreateMobileViewportManager(true);
+  }
+
+  return NS_OK;
+}
+
+/* virtual */
+int32_t nsDocShell::ItemType() { return mItemType; }
+
+NS_IMETHODIMP
+nsDocShell::GetItemType(int32_t* aItemType) {
+  NS_ENSURE_ARG_POINTER(aItemType);
+
+  MOZ_DIAGNOSTIC_ASSERT(
+      (mBrowsingContext->IsContent() ? typeContent : typeChrome) == mItemType);
+  *aItemType = mItemType;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetInProcessParent(nsIDocShellTreeItem** aParent) {
+  if (!mParent) {
+    *aParent = nullptr;
+  } else {
+    CallQueryInterface(mParent, aParent);
+  }
+  // Note that in the case when the parent is not an nsIDocShellTreeItem we
+  // don't want to throw; we just want to return null.
+  return NS_OK;
+}
+
+// With Fission, related nsDocShell objects may exist in a different process. In
+// that case, this method will return `nullptr`, despite a parent nsDocShell
+// object existing.
+//
+// Prefer using `BrowsingContext::Parent()`, which will succeed even if the
+// parent entry is not in the current process, and handle the case where the
+// parent nsDocShell is inaccessible.
+already_AddRefed<nsDocShell> nsDocShell::GetInProcessParentDocshell() {
+  nsCOMPtr<nsIDocShell> docshell = do_QueryInterface(GetAsSupports(mParent));
+  return docshell.forget().downcast<nsDocShell>();
+}
+
+void nsDocShell::MaybeCreateInitialClientSource(nsIPrincipal* aPrincipal) {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  // If there is an existing document then there is no need to create
+  // a client for a future initial about:blank document.
+  if (mScriptGlobal && mScriptGlobal->GetCurrentInnerWindow() &&
+      mScriptGlobal->GetCurrentInnerWindow()->GetExtantDoc()) {
+    MOZ_DIAGNOSTIC_ASSERT(
+        mScriptGlobal->GetCurrentInnerWindow()->GetClientInfo().isSome());
+    MOZ_DIAGNOSTIC_ASSERT(!mInitialClientSource);
+    return;
+  }
+
+  // Don't recreate the initial client source.  We call this multiple times
+  // when DoChannelLoad() is called before CreateAboutBlankDocumentViewer.
+  if (mInitialClientSource) {
+    return;
+  }
+
+  // Don't pre-allocate the client when we are sandboxed.  The inherited
+  // principal does not take sandboxing into account.
+  // TODO: Refactor sandboxing principal code out so we can use it here.
+  if (!aPrincipal && mBrowsingContext->GetSandboxFlags()) {
+    return;
+  }
+
+  // We cannot get inherited foreign partitioned principal here. Instead, we
+  // directly check which principal we want to inherit for the service worker.
+  nsIPrincipal* principal =
+      aPrincipal
+          ? aPrincipal
+          : GetInheritedPrincipal(
+                false, StoragePrincipalHelper::
+                           ShouldUsePartitionPrincipalForServiceWorker(this));
+
+  // Sometimes there is no principal available when we are called from
+  // CreateAboutBlankDocumentViewer.  For example, sometimes the principal
+  // is only extracted from the load context after the document is created
+  // in Document::ResetToURI().  Ideally we would do something similar
+  // here, but for now lets just avoid the issue by not preallocating the
+  // client.
+  if (!principal) {
+    return;
+  }
+
+  nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
+  if (!win) {
+    return;
+  }
+
+  mInitialClientSource = ClientManager::CreateSource(
+      ClientType::Window, GetMainThreadSerialEventTarget(), principal);
+  MOZ_DIAGNOSTIC_ASSERT(mInitialClientSource);
+
+  // Mark the initial client as execution ready, but owned by the docshell.
+  // If the client is actually used this will cause ClientSource to force
+  // the creation of the initial about:blank by calling
+  // nsDocShell::GetDocument().
+  mInitialClientSource->DocShellExecutionReady(this);
+
+  // Next, check to see if the parent is controlled.
+  nsCOMPtr<nsIDocShell> parent = GetInProcessParentDocshell();
+  nsPIDOMWindowOuter* parentOuter = parent ? parent->GetWindow() : nullptr;
+  nsPIDOMWindowInner* parentInner =
+      parentOuter ? parentOuter->GetCurrentInnerWindow() : nullptr;
+  if (!parentInner) {
+    return;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  MOZ_ALWAYS_SUCCEEDS(NS_NewURI(getter_AddRefs(uri), "about:blank"_ns));
+
+  // We're done if there is no parent controller or if this docshell
+  // is not permitted to control for some reason.
+  Maybe<ServiceWorkerDescriptor> controller(parentInner->GetController());
+  if (controller.isNothing() ||
+      !ServiceWorkerAllowedToControlWindow(principal, uri)) {
+    return;
+  }
+
+  mInitialClientSource->InheritController(controller.ref());
+}
+
+Maybe<ClientInfo> nsDocShell::GetInitialClientInfo() const {
+  if (mInitialClientSource) {
+    Maybe<ClientInfo> result;
+    result.emplace(mInitialClientSource->Info());
+    return result;
+  }
+
+  nsPIDOMWindowInner* innerWindow =
+      mScriptGlobal ? mScriptGlobal->GetCurrentInnerWindow() : nullptr;
+  Document* doc = innerWindow ? innerWindow->GetExtantDoc() : nullptr;
+
+  if (!doc || !doc->IsInitialDocument()) {
+    return Maybe<ClientInfo>();
+  }
+
+  return innerWindow->GetClientInfo();
+}
+
+nsresult nsDocShell::SetDocLoaderParent(nsDocLoader* aParent) {
+  bool wasFrame = IsSubframe();
+
+  nsresult rv = nsDocLoader::SetDocLoaderParent(aParent);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsISupportsPriority> priorityGroup = do_QueryInterface(mLoadGroup);
+  if (wasFrame != IsSubframe() && priorityGroup) {
+    priorityGroup->AdjustPriority(wasFrame ? -1 : 1);
+  }
+
+  // Curse ambiguous nsISupports inheritance!
+  nsISupports* parent = GetAsSupports(aParent);
+
+  // If parent is another docshell, we inherit all their flags for
+  // allowing plugins, scripting etc.
+  bool value;
+  nsCOMPtr<nsIDocShell> parentAsDocShell(do_QueryInterface(parent));
+
+  if (parentAsDocShell) {
+    if (mAllowMetaRedirects &&
+        NS_SUCCEEDED(parentAsDocShell->GetAllowMetaRedirects(&value))) {
+      SetAllowMetaRedirects(value);
+    }
+    if (mAllowSubframes &&
+        NS_SUCCEEDED(parentAsDocShell->GetAllowSubframes(&value))) {
+      SetAllowSubframes(value);
+    }
+    if (mAllowImages &&
+        NS_SUCCEEDED(parentAsDocShell->GetAllowImages(&value))) {
+      SetAllowImages(value);
+    }
+    SetAllowMedia(parentAsDocShell->GetAllowMedia() && mAllowMedia);
+    if (mAllowWindowControl &&
+        NS_SUCCEEDED(parentAsDocShell->GetAllowWindowControl(&value))) {
+      SetAllowWindowControl(value);
+    }
+    if (NS_FAILED(parentAsDocShell->GetAllowDNSPrefetch(&value))) {
+      value = false;
+    }
+    SetAllowDNSPrefetch(mAllowDNSPrefetch && value);
+
+    // We don't need to inherit metaViewportOverride, because the viewport
+    // is only relevant for the outermost nsDocShell, not for any iframes
+    // like this that might be embedded within it.
+  }
+
+  nsCOMPtr<nsIURIContentListener> parentURIListener(do_GetInterface(parent));
+  if (parentURIListener) {
+    mContentListener->SetParentContentListener(parentURIListener);
+  }
+
+  return NS_OK;
+}
+
+void nsDocShell::MaybeRestoreWindowName() {
+  if (!StaticPrefs::privacy_window_name_update_enabled()) {
+    return;
+  }
+
+  // We only restore window.name for the top-level content.
+  if (!mBrowsingContext->IsTopContent()) {
+    return;
+  }
+
+  nsAutoString name;
+
+  // Following implements https://html.spec.whatwg.org/#history-traversal:
+  // Step 4.4. Check if the loading entry has a name.
+
+  if (mLSHE) {
+    mLSHE->GetName(name);
+  }
+
+  if (mLoadingEntry) {
+    name = mLoadingEntry->mInfo.GetName();
+  }
+
+  if (name.IsEmpty()) {
+    return;
+  }
+
+  // Step 4.4.1. Set the name to the browsing context.
+  Unused << mBrowsingContext->SetName(name);
+
+  // Step 4.4.2. Clear the name of all entries that are contiguous and
+  // same-origin with the loading entry.
+  if (mLSHE) {
+    nsSHistory::WalkContiguousEntries(
+        mLSHE, [](nsISHEntry* aEntry) { aEntry->SetName(EmptyString()); });
+  }
+
+  if (mLoadingEntry) {
+    // Clear the name of the session entry in the child side. For parent side,
+    // the clearing will be done when we commit the history to the parent.
+    mLoadingEntry->mInfo.SetName(EmptyString());
+  }
+}
+
+void nsDocShell::StoreWindowNameToSHEntries() {
+  MOZ_ASSERT(mBrowsingContext->IsTopContent());
+
+  nsAutoString name;
+  mBrowsingContext->GetName(name);
+
+  if (mOSHE) {
+    nsSHistory::WalkContiguousEntries(
+        mOSHE, [&](nsISHEntry* aEntry) { aEntry->SetName(name); });
+  }
+
+  if (mozilla::SessionHistoryInParent()) {
+    if (XRE_IsParentProcess()) {
+      SessionHistoryEntry* entry =
+          mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+      if (entry) {
+        nsSHistory::WalkContiguousEntries(
+            entry, [&](nsISHEntry* aEntry) { aEntry->SetName(name); });
+      }
+    } else {
+      // Ask parent process to store the name in entries.
+      mozilla::Unused
+          << ContentChild::GetSingleton()
+                 ->SendSessionHistoryEntryStoreWindowNameInContiguousEntries(
+                     mBrowsingContext, name);
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::GetInProcessSameTypeParent(nsIDocShellTreeItem** aParent) {
+  if (BrowsingContext* parentBC = mBrowsingContext->GetParent()) {
+    *aParent = do_AddRef(parentBC->GetDocShell()).take();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetInProcessRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
+  NS_ENSURE_ARG_POINTER(aRootTreeItem);
+
+  RefPtr<nsDocShell> root = this;
+  RefPtr<nsDocShell> parent = root->GetInProcessParentDocshell();
+  while (parent) {
+    root = parent;
+    parent = root->GetInProcessParentDocshell();
+  }
+
+  root.forget(aRootTreeItem);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetInProcessSameTypeRootTreeItem(
+    nsIDocShellTreeItem** aRootTreeItem) {
+  NS_ENSURE_ARG_POINTER(aRootTreeItem);
+  *aRootTreeItem = static_cast<nsIDocShellTreeItem*>(this);
+
+  nsCOMPtr<nsIDocShellTreeItem> parent;
+  NS_ENSURE_SUCCESS(GetInProcessSameTypeParent(getter_AddRefs(parent)),
+                    NS_ERROR_FAILURE);
+  while (parent) {
+    *aRootTreeItem = parent;
+    NS_ENSURE_SUCCESS(
+        (*aRootTreeItem)->GetInProcessSameTypeParent(getter_AddRefs(parent)),
+        NS_ERROR_FAILURE);
+  }
+  NS_ADDREF(*aRootTreeItem);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetTreeOwner(nsIDocShellTreeOwner** aTreeOwner) {
+  NS_ENSURE_ARG_POINTER(aTreeOwner);
+
+  *aTreeOwner = mTreeOwner;
+  NS_IF_ADDREF(*aTreeOwner);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetTreeOwner(nsIDocShellTreeOwner* aTreeOwner) {
+  if (mIsBeingDestroyed && aTreeOwner) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Don't automatically set the progress based on the tree owner for frames
+  if (!IsSubframe()) {
+    nsCOMPtr<nsIWebProgress> webProgress =
+        do_QueryInterface(GetAsSupports(this));
+
+    if (webProgress) {
+      nsCOMPtr<nsIWebProgressListener> oldListener =
+          do_QueryInterface(mTreeOwner);
+      nsCOMPtr<nsIWebProgressListener> newListener =
+          do_QueryInterface(aTreeOwner);
+
+      if (oldListener) {
+        webProgress->RemoveProgressListener(oldListener);
+      }
+
+      if (newListener) {
+        webProgress->AddProgressListener(newListener,
+                                         nsIWebProgress::NOTIFY_ALL);
+      }
+    }
+  }
+
+  mTreeOwner = aTreeOwner;  // Weak reference per API
+
+  for (auto* childDocLoader : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShellTreeItem> child = do_QueryObject(childDocLoader);
+    NS_ENSURE_TRUE(child, NS_ERROR_FAILURE);
+
+    if (child->ItemType() == mItemType) {
+      child->SetTreeOwner(aTreeOwner);
+    }
+  }
+
+  // If we're in the content process and have had a TreeOwner set on us, extract
+  // our BrowserChild actor. If we've already had our BrowserChild set, assert
+  // that it hasn't changed.
+  if (mTreeOwner && XRE_IsContentProcess()) {
+    nsCOMPtr<nsIBrowserChild> newBrowserChild = do_GetInterface(mTreeOwner);
+    MOZ_ASSERT(newBrowserChild,
+               "No BrowserChild actor for tree owner in Content!");
+
+    if (mBrowserChild) {
+      nsCOMPtr<nsIBrowserChild> oldBrowserChild =
+          do_QueryReferent(mBrowserChild);
+      MOZ_RELEASE_ASSERT(
+          oldBrowserChild == newBrowserChild,
+          "Cannot change BrowserChild during nsDocShell lifetime!");
+    } else {
+      mBrowserChild = do_GetWeakReference(newBrowserChild);
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetHistoryID(nsID& aID) {
+  aID = mBrowsingContext->GetHistoryID();
+  return NS_OK;
+}
+
+const nsID& nsDocShell::HistoryID() { return mBrowsingContext->GetHistoryID(); }
+
+NS_IMETHODIMP
+nsDocShell::GetIsInUnload(bool* aIsInUnload) {
+  *aIsInUnload = mFiredUnloadEvent;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetInProcessChildCount(int32_t* aChildCount) {
+  NS_ENSURE_ARG_POINTER(aChildCount);
+  *aChildCount = mChildList.Length();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::AddChild(nsIDocShellTreeItem* aChild) {
+  NS_ENSURE_ARG_POINTER(aChild);
+
+  RefPtr<nsDocLoader> childAsDocLoader = GetAsDocLoader(aChild);
+  NS_ENSURE_TRUE(childAsDocLoader, NS_ERROR_UNEXPECTED);
+
+  // Make sure we're not creating a loop in the docshell tree
+  nsDocLoader* ancestor = this;
+  do {
+    if (childAsDocLoader == ancestor) {
+      return NS_ERROR_ILLEGAL_VALUE;
+    }
+    ancestor = ancestor->GetParent();
+  } while (ancestor);
+
+  // Make sure to remove the child from its current parent.
+  nsDocLoader* childsParent = childAsDocLoader->GetParent();
+  if (childsParent) {
+    nsresult rv = childsParent->RemoveChildLoader(childAsDocLoader);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // Make sure to clear the treeowner in case this child is a different type
+  // from us.
+  aChild->SetTreeOwner(nullptr);
+
+  nsresult res = AddChildLoader(childAsDocLoader);
+  NS_ENSURE_SUCCESS(res, res);
+  NS_ASSERTION(!mChildList.IsEmpty(),
+               "child list must not be empty after a successful add");
+
+  /* Set the child's global history if the parent has one */
+  if (mBrowsingContext->GetUseGlobalHistory()) {
+    // childDocShell->SetUseGlobalHistory(true);
+    // this should be set through BC inherit
+    MOZ_ASSERT(aChild->GetBrowsingContext()->GetUseGlobalHistory());
+  }
+
+  if (aChild->ItemType() != mItemType) {
+    return NS_OK;
+  }
+
+  aChild->SetTreeOwner(mTreeOwner);
+
+  nsCOMPtr<nsIDocShell> childAsDocShell(do_QueryInterface(aChild));
+  if (!childAsDocShell) {
+    return NS_OK;
+  }
+
+  // charset, style-disabling, and zoom will be inherited in SetupNewViewer()
+
+  // Now take this document's charset and set the child's parentCharset field
+  // to it. We'll later use that field, in the loading process, for the
+  // charset choosing algorithm.
+  // If we fail, at any point, we just return NS_OK.
+  // This code has some performance impact. But this will be reduced when
+  // the current charset will finally be stored as an Atom, avoiding the
+  // alias resolution extra look-up.
+
+  // we are NOT going to propagate the charset is this Chrome's docshell
+  if (mItemType == nsIDocShellTreeItem::typeChrome) {
+    return NS_OK;
+  }
+
+  // get the parent's current charset
+  if (!mDocumentViewer) {
+    return NS_OK;
+  }
+  Document* doc = mDocumentViewer->GetDocument();
+  if (!doc) {
+    return NS_OK;
+  }
+
+  const Encoding* parentCS = doc->GetDocumentCharacterSet();
+  int32_t charsetSource = doc->GetDocumentCharacterSetSource();
+  // set the child's parentCharset
+  childAsDocShell->SetParentCharset(parentCS, charsetSource,
+                                    doc->NodePrincipal());
+
+  // printf("### 1 >>> Adding child. Parent CS = %s. ItemType = %d.\n",
+  //        NS_LossyConvertUTF16toASCII(parentCS).get(), mItemType);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::RemoveChild(nsIDocShellTreeItem* aChild) {
+  NS_ENSURE_ARG_POINTER(aChild);
+
+  RefPtr<nsDocLoader> childAsDocLoader = GetAsDocLoader(aChild);
+  NS_ENSURE_TRUE(childAsDocLoader, NS_ERROR_UNEXPECTED);
+
+  nsresult rv = RemoveChildLoader(childAsDocLoader);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aChild->SetTreeOwner(nullptr);
+
+  return nsDocLoader::AddDocLoaderAsChildOfRoot(childAsDocLoader);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetInProcessChildAt(int32_t aIndex, nsIDocShellTreeItem** aChild) {
+  NS_ENSURE_ARG_POINTER(aChild);
+
+  RefPtr<nsDocShell> child = GetInProcessChildAt(aIndex);
+  NS_ENSURE_TRUE(child, NS_ERROR_UNEXPECTED);
+
+  child.forget(aChild);
+
+  return NS_OK;
+}
+
+nsDocShell* nsDocShell::GetInProcessChildAt(int32_t aIndex) {
+#ifdef DEBUG
+  if (aIndex < 0) {
+    NS_WARNING("Negative index passed to GetChildAt");
+  } else if (static_cast<uint32_t>(aIndex) >= mChildList.Length()) {
+    NS_WARNING("Too large an index passed to GetChildAt");
+  }
+#endif
+
+  nsIDocumentLoader* child = ChildAt(aIndex);
+
+  // child may be nullptr here.
+  return static_cast<nsDocShell*>(child);
+}
+
+nsresult nsDocShell::AddChildSHEntry(nsISHEntry* aCloneRef,
+                                     nsISHEntry* aNewEntry,
+                                     int32_t aChildOffset, uint32_t aLoadType,
+                                     bool aCloneChildren) {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+  nsresult rv = NS_OK;
+
+  if (mLSHE && aLoadType != LOAD_PUSHSTATE) {
+    /* You get here if you are currently building a
+     * hierarchy ie.,you just visited a frameset page
+     */
+    if (NS_FAILED(mLSHE->ReplaceChild(aNewEntry))) {
+      rv = mLSHE->AddChild(aNewEntry, aChildOffset);
+    }
+  } else if (!aCloneRef) {
+    /* This is an initial load in some subframe.  Just append it if we can */
+    if (mOSHE) {
+      rv = mOSHE->AddChild(aNewEntry, aChildOffset, UseRemoteSubframes());
+    }
+  } else {
+    RefPtr<ChildSHistory> shistory = GetRootSessionHistory();
+    if (shistory) {
+      rv = shistory->LegacySHistory()->AddChildSHEntryHelper(
+          aCloneRef, aNewEntry, mBrowsingContext->Top(), aCloneChildren);
+    }
+  }
+  return rv;
+}
+
+nsresult nsDocShell::AddChildSHEntryToParent(nsISHEntry* aNewEntry,
+                                             int32_t aChildOffset,
+                                             bool aCloneChildren) {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+  /* You will get here when you are in a subframe and
+   * a new url has been loaded on you.
+   * The mOSHE in this subframe will be the previous url's
+   * mOSHE. This mOSHE will be used as the identification
+   * for this subframe in the  CloneAndReplace function.
+   */
+
+  // In this case, we will end up calling AddEntry, which increases the
+  // current index by 1
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (rootSH) {
+    mPreviousEntryIndex = rootSH->Index();
+  }
+
+  nsresult rv;
+  // XXX(farre): this is not Fission safe, expect errors. This never
+  // get's executed once session history in the parent is enabled.
+  nsCOMPtr<nsIDocShell> parent = do_QueryInterface(GetAsSupports(mParent), &rv);
+  NS_WARNING_ASSERTION(
+      parent || !UseRemoteSubframes(),
+      "Failed to add child session history entry! This will be resolved once "
+      "session history in the parent is enabled.");
+  if (parent) {
+    rv = nsDocShell::Cast(parent)->AddChildSHEntry(
+        mOSHE, aNewEntry, aChildOffset, mLoadType, aCloneChildren);
+  }
+
+  if (rootSH) {
+    mLoadedEntryIndex = rootSH->Index();
+
+    if (MOZ_UNLIKELY(MOZ_LOG_TEST(gPageCacheLog, LogLevel::Verbose))) {
+      MOZ_LOG(gPageCacheLog, LogLevel::Verbose,
+              ("Previous index: %d, Loaded index: %d", mPreviousEntryIndex,
+               mLoadedEntryIndex));
+    }
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCurrentSHEntry(nsISHEntry** aEntry, bool* aOSHE) {
+  *aOSHE = false;
+  *aEntry = nullptr;
+  if (mLSHE) {
+    NS_ADDREF(*aEntry = mLSHE);
+  } else if (mOSHE) {
+    NS_ADDREF(*aEntry = mOSHE);
+    *aOSHE = true;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsDocShell::SynchronizeLayoutHistoryState() {
+  if (mActiveEntry && mActiveEntry->GetLayoutHistoryState() &&
+      mBrowsingContext) {
+    if (XRE_IsContentProcess()) {
+      dom::ContentChild* contentChild = dom::ContentChild::GetSingleton();
+      if (contentChild) {
+        contentChild->SendSynchronizeLayoutHistoryState(
+            mBrowsingContext, mActiveEntry->GetLayoutHistoryState());
+      }
+    } else {
+      SessionHistoryEntry* entry =
+          mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+      if (entry) {
+        entry->SetLayoutHistoryState(mActiveEntry->GetLayoutHistoryState());
+      }
+    }
+    if (mLoadingEntry &&
+        mLoadingEntry->mInfo.SharedId() == mActiveEntry->SharedId()) {
+      mLoadingEntry->mInfo.SetLayoutHistoryState(
+          mActiveEntry->GetLayoutHistoryState());
+    }
+  }
+
+  return NS_OK;
+}
+
+void nsDocShell::SetLoadGroupDefaultLoadFlags(nsLoadFlags aLoadFlags) {
+  if (mLoadGroup) {
+    mLoadGroup->SetDefaultLoadFlags(aLoadFlags);
+  } else {
+    NS_WARNING(
+        "nsDocShell::SetLoadGroupDefaultLoadFlags has no loadGroup to "
+        "propagate the mode to");
+  }
+}
+
+nsIScriptGlobalObject* nsDocShell::GetScriptGlobalObject() {
+  NS_ENSURE_SUCCESS(EnsureScriptEnvironment(), nullptr);
+  return mScriptGlobal;
+}
+
+Document* nsDocShell::GetDocument() {
+  NS_ENSURE_SUCCESS(EnsureDocumentViewer(), nullptr);
+  return mDocumentViewer->GetDocument();
+}
+
+Document* nsDocShell::GetExtantDocument() {
+  return mDocumentViewer ? mDocumentViewer->GetDocument() : nullptr;
+}
+
+nsPIDOMWindowOuter* nsDocShell::GetWindow() {
+  if (NS_FAILED(EnsureScriptEnvironment())) {
+    return nullptr;
+  }
+  return mScriptGlobal;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDomWindow(mozIDOMWindowProxy** aWindow) {
+  NS_ENSURE_ARG_POINTER(aWindow);
+
+  nsresult rv = EnsureScriptEnvironment();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  RefPtr<nsGlobalWindowOuter> window = mScriptGlobal;
+  window.forget(aWindow);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
+  RefPtr<ContentFrameMessageManager> mm;
+  if (RefPtr<BrowserChild> browserChild = BrowserChild::GetFrom(this)) {
+    mm = browserChild->GetMessageManager();
+  } else if (nsPIDOMWindowOuter* win = GetWindow()) {
+    mm = win->GetMessageManager();
+  }
+  mm.forget(aMessageManager);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetIsNavigating(bool* aOut) {
+  *aOut = mIsNavigating;
+  return NS_OK;
+}
+
+void nsDocShell::ClearFrameHistory(nsISHEntry* aEntry) {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (!rootSH || !aEntry) {
+    return;
+  }
+
+  rootSH->LegacySHistory()->RemoveFrameEntries(aEntry);
+}
+
+//-------------------------------------
+//-- Helper Method for Print discovery
+//-------------------------------------
+bool nsDocShell::NavigationBlockedByPrinting(bool aDisplayErrorDialog) {
+  if (!mBrowsingContext->Top()->GetIsPrinting()) {
+    return false;
+  }
+  if (aDisplayErrorDialog) {
+    DisplayLoadError(NS_ERROR_DOCUMENT_IS_PRINTMODE, nullptr, nullptr, nullptr);
+  }
+  return true;
+}
+
+bool nsDocShell::IsNavigationAllowed(bool aDisplayPrintErrorDialog,
+                                     bool aCheckIfUnloadFired) {
+  bool isAllowed = !NavigationBlockedByPrinting(aDisplayPrintErrorDialog) &&
+                   (!aCheckIfUnloadFired || !mFiredUnloadEvent);
+  if (!isAllowed) {
+    return false;
+  }
+  if (!mDocumentViewer) {
+    return true;
+  }
+  bool firingBeforeUnload;
+  mDocumentViewer->GetBeforeUnloadFiring(&firingBeforeUnload);
+  return !firingBeforeUnload;
+}
+
+//*****************************************************************************
+// nsDocShell::nsIWebNavigation
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::GetCanGoBack(bool* aCanGoBack) {
+  *aCanGoBack = false;
+  if (!IsNavigationAllowed(false)) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (rootSH) {
+    *aCanGoBack = rootSH->CanGo(-1);
+    MOZ_LOG(gSHLog, LogLevel::Verbose,
+            ("nsDocShell %p CanGoBack()->%d", this, *aCanGoBack));
+
+    return NS_OK;
+  }
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCanGoForward(bool* aCanGoForward) {
+  *aCanGoForward = false;
+  if (!IsNavigationAllowed(false)) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (rootSH) {
+    *aCanGoForward = rootSH->CanGo(1);
+    MOZ_LOG(gSHLog, LogLevel::Verbose,
+            ("nsDocShell %p CanGoForward()->%d", this, *aCanGoForward));
+    return NS_OK;
+  }
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsDocShell::GoBack(bool aRequireUserInteraction, bool aUserActivation) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+
+  auto cleanupIsNavigating = MakeScopeExit([&]() { mIsNavigating = false; });
+  mIsNavigating = true;
+
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  NS_ENSURE_TRUE(rootSH, NS_ERROR_FAILURE);
+  ErrorResult rv;
+  rootSH->Go(-1, aRequireUserInteraction, aUserActivation, rv);
+  return rv.StealNSResult();
+}
+
+NS_IMETHODIMP
+nsDocShell::GoForward(bool aRequireUserInteraction, bool aUserActivation) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+
+  auto cleanupIsNavigating = MakeScopeExit([&]() { mIsNavigating = false; });
+  mIsNavigating = true;
+
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  NS_ENSURE_TRUE(rootSH, NS_ERROR_FAILURE);
+  ErrorResult rv;
+  rootSH->Go(1, aRequireUserInteraction, aUserActivation, rv);
+  return rv.StealNSResult();
+}
+
+// XXX(nika): We may want to stop exposing this API in the child process? Going
+// to a specific index from multiple different processes could definitely race.
+NS_IMETHODIMP
+nsDocShell::GotoIndex(int32_t aIndex, bool aUserActivation) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+
+  auto cleanupIsNavigating = MakeScopeExit([&]() { mIsNavigating = false; });
+  mIsNavigating = true;
+
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  NS_ENSURE_TRUE(rootSH, NS_ERROR_FAILURE);
+
+  ErrorResult rv;
+  rootSH->GotoIndex(aIndex, aIndex - rootSH->Index(), false, aUserActivation,
+                    rv);
+  return rv.StealNSResult();
+}
+
+nsresult nsDocShell::LoadURI(nsIURI* aURI,
+                             const LoadURIOptions& aLoadURIOptions) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+  RefPtr<nsDocShellLoadState> loadState;
+  nsresult rv = nsDocShellLoadState::CreateFromLoadURIOptions(
+      mBrowsingContext, aURI, aLoadURIOptions, getter_AddRefs(loadState));
+  MOZ_ASSERT(rv != NS_ERROR_MALFORMED_URI);
+  if (NS_FAILED(rv) || !loadState) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return LoadURI(loadState, true);
+}
+
+NS_IMETHODIMP
+nsDocShell::LoadURIFromScript(nsIURI* aURI,
+                              JS::Handle<JS::Value> aLoadURIOptions,
+                              JSContext* aCx) {
+  // generate dictionary for aLoadURIOptions and forward call
+  LoadURIOptions loadURIOptions;
+  if (!loadURIOptions.Init(aCx, aLoadURIOptions)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  return LoadURI(aURI, loadURIOptions);
+}
+
+nsresult nsDocShell::FixupAndLoadURIString(
+    const nsAString& aURIString, const LoadURIOptions& aLoadURIOptions) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+
+  RefPtr<nsDocShellLoadState> loadState;
+  nsresult rv = nsDocShellLoadState::CreateFromLoadURIOptions(
+      mBrowsingContext, aURIString, aLoadURIOptions, getter_AddRefs(loadState));
+
+  uint32_t loadFlags = aLoadURIOptions.mLoadFlags;
+  if (NS_ERROR_MALFORMED_URI == rv) {
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("Creating an active entry on nsDocShell %p to %s (because "
+             "we're showing an error page)",
+             this, NS_ConvertUTF16toUTF8(aURIString).get()));
+
+    // We need to store a session history entry. We don't have a valid URI, so
+    // we use about:blank instead.
+    nsCOMPtr<nsIURI> uri;
+    MOZ_ALWAYS_SUCCEEDS(NS_NewURI(getter_AddRefs(uri), "about:blank"_ns));
+    nsCOMPtr<nsIPrincipal> triggeringPrincipal;
+    if (aLoadURIOptions.mTriggeringPrincipal) {
+      triggeringPrincipal = aLoadURIOptions.mTriggeringPrincipal;
+    } else {
+      triggeringPrincipal = nsContentUtils::GetSystemPrincipal();
+    }
+    if (mozilla::SessionHistoryInParent()) {
+      mActiveEntry = MakeUnique<SessionHistoryInfo>(
+          uri, triggeringPrincipal, nullptr, nullptr, nullptr,
+          nsLiteralCString("text/html"));
+      mBrowsingContext->SetActiveSessionHistoryEntry(
+          Nothing(), mActiveEntry.get(), MAKE_LOAD_TYPE(LOAD_NORMAL, loadFlags),
+          /* aUpdatedCacheKey = */ 0);
+    }
+    if (DisplayLoadError(rv, nullptr, PromiseFlatString(aURIString).get(),
+                         nullptr) &&
+        (loadFlags & LOAD_FLAGS_ERROR_LOAD_CHANGES_RV) != 0) {
+      return NS_ERROR_LOAD_SHOWED_ERRORPAGE;
+    }
+  }
+
+  if (NS_FAILED(rv) || !loadState) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return LoadURI(loadState, true);
+}
+
+NS_IMETHODIMP
+nsDocShell::FixupAndLoadURIStringFromScript(
+    const nsAString& aURIString, JS::Handle<JS::Value> aLoadURIOptions,
+    JSContext* aCx) {
+  // generate dictionary for aLoadURIOptions and forward call
+  LoadURIOptions loadURIOptions;
+  if (!loadURIOptions.Init(aCx, aLoadURIOptions)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  return FixupAndLoadURIString(aURIString, loadURIOptions);
+}
+
+void nsDocShell::UnblockEmbedderLoadEventForFailure(bool aFireFrameErrorEvent) {
+  // If we're not in a content frame, or are at a BrowsingContext tree boundary,
+  // such as the content-chrome boundary, don't fire the error event.
+  if (mBrowsingContext->IsTopContent() || mBrowsingContext->IsChrome()) {
+    return;
+  }
+
+  // If embedder is same-process, then unblocking the load event is already
+  // handled by nsDocLoader. Fire the error event on our embedder element if
+  // requested.
+  //
+  // XXX: Bug 1440212 is looking into potentially changing this behaviour to act
+  // more like the remote case when in-process.
+  RefPtr<Element> element = mBrowsingContext->GetEmbedderElement();
+  if (element) {
+    if (aFireFrameErrorEvent) {
+      if (RefPtr<nsFrameLoaderOwner> flo = do_QueryObject(element)) {
+        if (RefPtr<nsFrameLoader> fl = flo->GetFrameLoader()) {
+          fl->FireErrorEvent();
+        }
+      }
+    }
+    return;
+  }
+
+  // If we have a cross-process parent document, we must notify it that we no
+  // longer block its load event.  This is necessary for OOP sub-documents
+  // because error documents do not result in a call to
+  // SendMaybeFireEmbedderLoadEvents via any of the normal call paths.
+  // (Obviously, we must do this before any of the returns below.)
+  RefPtr<BrowserChild> browserChild = BrowserChild::GetFrom(this);
+  if (browserChild &&
+      !mBrowsingContext->GetParentWindowContext()->IsInProcess()) {
+    mozilla::Unused << browserChild->SendMaybeFireEmbedderLoadEvents(
+        aFireFrameErrorEvent ? EmbedderElementEventType::ErrorEvent
+                             : EmbedderElementEventType::NoEvent);
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::DisplayLoadError(nsresult aError, nsIURI* aURI,
+                             const char16_t* aURL, nsIChannel* aFailedChannel,
+                             bool* aDisplayedErrorPage) {
+  MOZ_LOG(gDocShellLeakLog, LogLevel::Debug,
+          ("DOCSHELL %p DisplayLoadError %s\n", this,
+           aURI ? aURI->GetSpecOrDefault().get() : ""));
+
+  *aDisplayedErrorPage = false;
+  // Get prompt and string bundle services
+  nsCOMPtr<nsIPrompt> prompter;
+  nsCOMPtr<nsIStringBundle> stringBundle;
+  GetPromptAndStringBundle(getter_AddRefs(prompter),
+                           getter_AddRefs(stringBundle));
+
+  NS_ENSURE_TRUE(stringBundle, NS_ERROR_FAILURE);
+  NS_ENSURE_TRUE(prompter, NS_ERROR_FAILURE);
+
+  const char* error = nullptr;
+  // The key used to select the appropriate error message from the properties
+  // file.
+  const char* errorDescriptionID = nullptr;
+  AutoTArray<nsString, 3> formatStrs;
+  bool addHostPort = false;
+  bool isBadStsCertError = false;
+  nsresult rv = NS_OK;
+  nsAutoString messageStr;
+  nsAutoCString cssClass;
+  nsAutoCString errorPage;
+
+  errorPage.AssignLiteral("neterror");
+
+  // Turn the error code into a human readable error message.
+  if (NS_ERROR_UNKNOWN_PROTOCOL == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+
+    // Extract the schemes into a comma delimited list.
+    nsAutoCString scheme;
+    aURI->GetScheme(scheme);
+    CopyASCIItoUTF16(scheme, *formatStrs.AppendElement());
+    nsCOMPtr<nsINestedURI> nestedURI = do_QueryInterface(aURI);
+    while (nestedURI) {
+      nsCOMPtr<nsIURI> tempURI;
+      nsresult rv2;
+      rv2 = nestedURI->GetInnerURI(getter_AddRefs(tempURI));
+      if (NS_SUCCEEDED(rv2) && tempURI) {
+        tempURI->GetScheme(scheme);
+        formatStrs[0].AppendLiteral(", ");
+        AppendASCIItoUTF16(scheme, formatStrs[0]);
+      }
+      nestedURI = do_QueryInterface(tempURI);
+    }
+    error = "unknownProtocolFound";
+  } else if (NS_ERROR_FILE_NOT_FOUND == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+    error = "fileNotFound";
+  } else if (NS_ERROR_FILE_ACCESS_DENIED == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+    error = "fileAccessDenied";
+  } else if (NS_ERROR_UNKNOWN_HOST == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+    // Get the host
+    nsAutoCString host;
+    nsCOMPtr<nsIURI> innermostURI = NS_GetInnermostURI(aURI);
+    innermostURI->GetHost(host);
+    CopyUTF8toUTF16(host, *formatStrs.AppendElement());
+    errorDescriptionID = "dnsNotFound2";
+    error = "dnsNotFound";
+  } else if (NS_ERROR_CONNECTION_REFUSED == aError ||
+             NS_ERROR_PROXY_BAD_GATEWAY == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+    addHostPort = true;
+    error = "connectionFailure";
+  } else if (NS_ERROR_NET_INTERRUPT == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+    addHostPort = true;
+    error = "netInterrupt";
+  } else if (NS_ERROR_NET_TIMEOUT == aError ||
+             NS_ERROR_PROXY_GATEWAY_TIMEOUT == aError ||
+             NS_ERROR_NET_TIMEOUT_EXTERNAL == aError) {
+    NS_ENSURE_ARG_POINTER(aURI);
+    // Get the host
+    nsAutoCString host;
+    aURI->GetHost(host);
+    CopyUTF8toUTF16(host, *formatStrs.AppendElement());
+    error = "netTimeout";
+  } else if (NS_ERROR_CSP_FRAME_ANCESTOR_VIOLATION == aError ||
+             NS_ERROR_CSP_FORM_ACTION_VIOLATION == aError) {
+    // CSP error
+    cssClass.AssignLiteral("neterror");
+    error = "cspBlocked";
+  } else if (NS_ERROR_XFO_VIOLATION == aError) {
+    // XFO error
+    cssClass.AssignLiteral("neterror");
+    error = "xfoBlocked";
+  } else if (NS_ERROR_GET_MODULE(aError) == NS_ERROR_MODULE_SECURITY) {
+    nsCOMPtr<nsINSSErrorsService> nsserr =
+        do_GetService(NS_NSS_ERRORS_SERVICE_CONTRACTID);
+
+    uint32_t errorClass;
+    if (!nsserr || NS_FAILED(nsserr->GetErrorClass(aError, &errorClass))) {
+      errorClass = nsINSSErrorsService::ERROR_CLASS_SSL_PROTOCOL;
+    }
+
+    nsCOMPtr<nsITransportSecurityInfo> tsi;
+    if (aFailedChannel) {
+      aFailedChannel->GetSecurityInfo(getter_AddRefs(tsi));
+    }
+    if (tsi) {
+      uint32_t securityState;
+      tsi->GetSecurityState(&securityState);
+      if (securityState & nsIWebProgressListener::STATE_USES_SSL_3) {
+        error = "sslv3Used";
+        addHostPort = true;
+      } else if (securityState &
+                 nsIWebProgressListener::STATE_USES_WEAK_CRYPTO) {
+        error = "weakCryptoUsed";
+        addHostPort = true;
+      }
+    } else {
+      // No channel, let's obtain the generic error message
+      if (nsserr) {
+        nsserr->GetErrorMessage(aError, messageStr);
+      }
+    }
+    // We don't have a message string here anymore but DisplayLoadError
+    // requires a non-empty messageStr.
+    messageStr.Truncate();
+    messageStr.AssignLiteral(u" ");
+    if (errorClass == nsINSSErrorsService::ERROR_CLASS_BAD_CERT) {
+      error = "nssBadCert";
+
+      // If this is an HTTP Strict Transport Security host or a pinned host
+      // and the certificate is bad, don't allow overrides (RFC 6797 section
+      // 12.1).
+      bool isStsHost = false;
+      bool isPinnedHost = false;
+      OriginAttributes attrsForHSTS;
+      if (aFailedChannel) {
+        StoragePrincipalHelper::GetOriginAttributesForHSTS(aFailedChannel,
+                                                           attrsForHSTS);
+      } else {
+        attrsForHSTS = GetOriginAttributes();
+      }
+
+      if (XRE_IsParentProcess()) {
+        nsCOMPtr<nsISiteSecurityService> sss =
+            do_GetService(NS_SSSERVICE_CONTRACTID, &rv);
+        NS_ENSURE_SUCCESS(rv, rv);
+        rv = sss->IsSecureURI(aURI, attrsForHSTS, &isStsHost);
+        NS_ENSURE_SUCCESS(rv, rv);
+      } else {
+        mozilla::dom::ContentChild* cc =
+            mozilla::dom::ContentChild::GetSingleton();
+        cc->SendIsSecureURI(aURI, attrsForHSTS, &isStsHost);
+      }
+      nsCOMPtr<nsIPublicKeyPinningService> pkps =
+          do_GetService(NS_PKPSERVICE_CONTRACTID, &rv);
+      NS_ENSURE_SUCCESS(rv, rv);
+      rv = pkps->HostHasPins(aURI, &isPinnedHost);
+
+      if (Preferences::GetBool("browser.xul.error_pages.expert_bad_cert",
+                               false)) {
+        cssClass.AssignLiteral("expertBadCert");
+      }
+
+      // HSTS/pinning takes precedence over the expert bad cert pref. We
+      // never want to show the "Add Exception" button for these sites.
+      // In the future we should differentiate between an HSTS host and a
+      // pinned host and display a more informative message to the user.
+      if (isStsHost || isPinnedHost) {
+        isBadStsCertError = true;
+        cssClass.AssignLiteral("badStsCert");
+      }
+
+      errorPage.Assign("certerror");
+    } else {
+      error = "nssFailure2";
+    }
+  } else if (NS_ERROR_PHISHING_URI == aError ||
+             NS_ERROR_MALWARE_URI == aError ||
+             NS_ERROR_UNWANTED_URI == aError ||
+             NS_ERROR_HARMFUL_URI == aError) {
+    nsAutoCString host;
+    aURI->GetHost(host);
+    CopyUTF8toUTF16(host, *formatStrs.AppendElement());
+
+    // Malware and phishing detectors may want to use an alternate error
+    // page, but if the pref's not set, we'll fall back on the standard page
+    nsAutoCString alternateErrorPage;
+    nsresult rv = Preferences::GetCString("urlclassifier.alternate_error_page",
+                                          alternateErrorPage);
+    if (NS_SUCCEEDED(rv)) {
+      errorPage.Assign(alternateErrorPage);
+    }
+
+    if (NS_ERROR_PHISHING_URI == aError) {
+      error = "deceptiveBlocked";
+    } else if (NS_ERROR_MALWARE_URI == aError) {
+      error = "malwareBlocked";
+    } else if (NS_ERROR_UNWANTED_URI == aError) {
+      error = "unwantedBlocked";
+    } else if (NS_ERROR_HARMFUL_URI == aError) {
+      error = "harmfulBlocked";
+    }
+
+    cssClass.AssignLiteral("blacklist");
+  } else if (NS_ERROR_CONTENT_CRASHED == aError) {
+    errorPage.AssignLiteral("tabcrashed");
+    error = "tabcrashed";
+
+    RefPtr<EventTarget> handler = mChromeEventHandler;
+    if (handler) {
+      nsCOMPtr<Element> element = do_QueryInterface(handler);
+      element->GetAttribute(u"crashedPageTitle"_ns, messageStr);
+    }
+
+    // DisplayLoadError requires a non-empty messageStr to proceed and call
+    // LoadErrorPage. If the page doesn't have a title, we will use a blank
+    // space which will be trimmed and thus treated as empty by the front-end.
+    if (messageStr.IsEmpty()) {
+      messageStr.AssignLiteral(u" ");
+    }
+  } else if (NS_ERROR_FRAME_CRASHED == aError) {
+    errorPage.AssignLiteral("framecrashed");
+    error = "framecrashed";
+    messageStr.AssignLiteral(u" ");
+  } else if (NS_ERROR_BUILDID_MISMATCH == aError) {
+    errorPage.AssignLiteral("restartrequired");
+    error = "restartrequired";
+
+    // DisplayLoadError requires a non-empty messageStr to proceed and call
+    // LoadErrorPage. If the page doesn't have a title, we will use a blank
+    // space which will be trimmed and thus treated as empty by the front-end.
+    if (messageStr.IsEmpty()) {
+      messageStr.AssignLiteral(u" ");
+    }
+  } else {
+    // Errors requiring simple formatting
+    switch (aError) {
+      case NS_ERROR_MALFORMED_URI:
+        // URI is malformed
+        error = "malformedURI";
+        errorDescriptionID = "malformedURI2";
+        break;
+      case NS_ERROR_REDIRECT_LOOP:
+        // Doc failed to load because the server generated too many redirects
+        error = "redirectLoop";
+        break;
+      case NS_ERROR_UNKNOWN_SOCKET_TYPE:
+        // Doc failed to load because PSM is not installed
+        error = "unknownSocketType";
+        break;
+      case NS_ERROR_NET_RESET:
+        // Doc failed to load because the server kept reseting the connection
+        // before we could read any data from it
+        error = "netReset";
+        break;
+      case NS_ERROR_DOCUMENT_NOT_CACHED:
+        // Doc failed to load because the cache does not contain a copy of
+        // the document.
+        error = "notCached";
+        break;
+      case NS_ERROR_OFFLINE:
+        // Doc failed to load because we are offline.
+        error = "netOffline";
+        break;
+      case NS_ERROR_DOCUMENT_IS_PRINTMODE:
+        // Doc navigation attempted while Printing or Print Preview
+        error = "isprinting";
+        break;
+      case NS_ERROR_PORT_ACCESS_NOT_ALLOWED:
+        // Port blocked for security reasons
+        addHostPort = true;
+        error = "deniedPortAccess";
+        break;
+      case NS_ERROR_UNKNOWN_PROXY_HOST:
+        // Proxy hostname could not be resolved.
+        error = "proxyResolveFailure";
+        break;
+      case NS_ERROR_PROXY_CONNECTION_REFUSED:
+      case NS_ERROR_PROXY_FORBIDDEN:
+      case NS_ERROR_PROXY_NOT_IMPLEMENTED:
+      case NS_ERROR_PROXY_AUTHENTICATION_FAILED:
+      case NS_ERROR_PROXY_TOO_MANY_REQUESTS:
+        // Proxy connection was refused.
+        error = "proxyConnectFailure";
+        break;
+      case NS_ERROR_INVALID_CONTENT_ENCODING:
+        // Bad Content Encoding.
+        error = "contentEncodingError";
+        break;
+      case NS_ERROR_UNSAFE_CONTENT_TYPE:
+        // Channel refused to load from an unrecognized content type.
+        error = "unsafeContentType";
+        break;
+      case NS_ERROR_CORRUPTED_CONTENT:
+        // Broken Content Detected. e.g. Content-MD5 check failure.
+        error = "corruptedContentErrorv2";
+        break;
+      case NS_ERROR_INTERCEPTION_FAILED:
+        // ServiceWorker intercepted request, but something went wrong.
+        error = "corruptedContentErrorv2";
+        break;
+      case NS_ERROR_NET_INADEQUATE_SECURITY:
+        // Server negotiated bad TLS for HTTP/2.
+        error = "inadequateSecurityError";
+        addHostPort = true;
+        break;
+      case NS_ERROR_BLOCKED_BY_POLICY:
+      case NS_ERROR_DOM_COOP_FAILED:
+      case NS_ERROR_DOM_COEP_FAILED:
+        // Page blocked by policy
+        error = "blockedByPolicy";
+        break;
+      case NS_ERROR_NET_HTTP2_SENT_GOAWAY:
+      case NS_ERROR_NET_HTTP3_PROTOCOL_ERROR:
+        // HTTP/2 or HTTP/3 stack detected a protocol error
+        error = "networkProtocolError";
+        break;
+
+      default:
+        break;
+    }
+  }
+
+  nsresult delegateErrorCode = aError;
+  // If the HTTPS-Only Mode upgraded this request and the upgrade might have
+  // caused this error, we replace the error-page with about:httpsonlyerror
+  if (nsHTTPSOnlyUtils::CouldBeHttpsOnlyError(aFailedChannel, aError)) {
+    errorPage.AssignLiteral("httpsonlyerror");
+    delegateErrorCode = NS_ERROR_HTTPS_ONLY;
+  } else if (isBadStsCertError) {
+    delegateErrorCode = NS_ERROR_BAD_HSTS_CERT;
+  }
+
+  if (nsCOMPtr<nsILoadURIDelegate> loadURIDelegate = GetLoadURIDelegate()) {
+    nsCOMPtr<nsIURI> errorPageURI;
+    rv = loadURIDelegate->HandleLoadError(
+        aURI, delegateErrorCode, NS_ERROR_GET_MODULE(delegateErrorCode),
+        getter_AddRefs(errorPageURI));
+    // If the docshell is going away there's no point in showing an error page.
+    if (NS_FAILED(rv) || mIsBeingDestroyed) {
+      *aDisplayedErrorPage = false;
+      return NS_OK;
+    }
+
+    if (errorPageURI) {
+      *aDisplayedErrorPage =
+          NS_SUCCEEDED(LoadErrorPage(errorPageURI, aURI, aFailedChannel));
+      return NS_OK;
+    }
+  }
+
+  // Test if the error should be displayed
+  if (!error) {
+    return NS_OK;
+  }
+
+  if (!errorDescriptionID) {
+    errorDescriptionID = error;
+  }
+
+  Telemetry::AccumulateCategoricalKeyed(
+      IsSubframe() ? "frame"_ns : "top"_ns,
+      mozilla::dom::LoadErrorToTelemetryLabel(aError));
+
+  // Test if the error needs to be formatted
+  if (!messageStr.IsEmpty()) {
+    // already obtained message
+  } else {
+    if (addHostPort) {
+      // Build up the host:port string.
+      nsAutoCString hostport;
+      if (aURI) {
+        aURI->GetHostPort(hostport);
+      } else {
+        hostport.Assign('?');
+      }
+      CopyUTF8toUTF16(hostport, *formatStrs.AppendElement());
+    }
+
+    nsAutoCString spec;
+    rv = NS_ERROR_NOT_AVAILABLE;
+    auto& nextFormatStr = *formatStrs.AppendElement();
+    if (aURI) {
+      // displaying "file://" is aesthetically unpleasing and could even be
+      // confusing to the user
+      if (SchemeIsFile(aURI)) {
+        aURI->GetPathQueryRef(spec);
+      } else {
+        aURI->GetSpec(spec);
+      }
+
+      nsCOMPtr<nsITextToSubURI> textToSubURI(
+          do_GetService(NS_ITEXTTOSUBURI_CONTRACTID, &rv));
+      if (NS_SUCCEEDED(rv)) {
+        rv = textToSubURI->UnEscapeURIForUI(spec, nextFormatStr);
+      }
+    } else {
+      spec.Assign('?');
+    }
+    if (NS_FAILED(rv)) {
+      CopyUTF8toUTF16(spec, nextFormatStr);
+    }
+    rv = NS_OK;
+
+    nsAutoString str;
+    rv =
+        stringBundle->FormatStringFromName(errorDescriptionID, formatStrs, str);
+    NS_ENSURE_SUCCESS(rv, rv);
+    messageStr.Assign(str);
+  }
+
+  // Display the error as a page or an alert prompt
+  NS_ENSURE_FALSE(messageStr.IsEmpty(), NS_ERROR_FAILURE);
+
+  if ((NS_ERROR_NET_INTERRUPT == aError || NS_ERROR_NET_RESET == aError) &&
+      SchemeIsHTTPS(aURI)) {
+    // Maybe TLS intolerant. Treat this as an SSL error.
+    error = "nssFailure2";
+  }
+
+  if (mBrowsingContext->GetUseErrorPages()) {
+    // Display an error page
+    nsresult loadedPage =
+        LoadErrorPage(aURI, aURL, errorPage.get(), error, messageStr.get(),
+                      cssClass.get(), aFailedChannel);
+    *aDisplayedErrorPage = NS_SUCCEEDED(loadedPage);
+  } else {
+    // The prompter reqires that our private window has a document (or it
+    // asserts). Satisfy that assertion now since GetDoc will force
+    // creation of one if it hasn't already been created.
+    if (mScriptGlobal) {
+      Unused << mScriptGlobal->GetDoc();
+    }
+
+    // Display a message box
+    prompter->Alert(nullptr, messageStr.get());
+  }
+
+  return NS_OK;
+}
+
+#define PREF_SAFEBROWSING_ALLOWOVERRIDE "browser.safebrowsing.allowOverride"
+
+nsresult nsDocShell::LoadErrorPage(nsIURI* aURI, const char16_t* aURL,
+                                   const char* aErrorPage,
+                                   const char* aErrorType,
+                                   const char16_t* aDescription,
+                                   const char* aCSSClass,
+                                   nsIChannel* aFailedChannel) {
+  if (mIsBeingDestroyed) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+#if defined(DEBUG)
+  if (MOZ_LOG_TEST(gDocShellLog, LogLevel::Debug)) {
+    nsAutoCString chanName;
+    if (aFailedChannel) {
+      aFailedChannel->GetName(chanName);
+    } else {
+      chanName.AssignLiteral("<no channel>");
+    }
+
+    MOZ_LOG(gDocShellLog, LogLevel::Debug,
+            ("nsDocShell[%p]::LoadErrorPage(\"%s\", \"%s\", {...}, [%s])\n",
+             this, aURI ? aURI->GetSpecOrDefault().get() : "",
+             NS_ConvertUTF16toUTF8(aURL).get(), chanName.get()));
+  }
+#endif
+
+  nsAutoCString url;
+  if (aURI) {
+    nsresult rv = aURI->GetSpec(url);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else if (aURL) {
+    CopyUTF16toUTF8(MakeStringSpan(aURL), url);
+  } else {
+    return NS_ERROR_INVALID_POINTER;
+  }
+
+  // Create a URL to pass all the error information through to the page.
+
+#undef SAFE_ESCAPE
+#define SAFE_ESCAPE(output, input, params)             \
+  if (NS_WARN_IF(!NS_Escape(input, output, params))) { \
+    return NS_ERROR_OUT_OF_MEMORY;                     \
+  }
+
+  nsCString escapedUrl, escapedError, escapedDescription, escapedCSSClass;
+  SAFE_ESCAPE(escapedUrl, url, url_Path);
+  SAFE_ESCAPE(escapedError, nsDependentCString(aErrorType), url_Path);
+  SAFE_ESCAPE(escapedDescription, NS_ConvertUTF16toUTF8(aDescription),
+              url_Path);
+  if (aCSSClass) {
+    nsCString cssClass(aCSSClass);
+    SAFE_ESCAPE(escapedCSSClass, cssClass, url_Path);
+  }
+  nsCString errorPageUrl("about:");
+  errorPageUrl.AppendASCII(aErrorPage);
+  errorPageUrl.AppendLiteral("?e=");
+
+  errorPageUrl.AppendASCII(escapedError.get());
+  errorPageUrl.AppendLiteral("&u=");
+  errorPageUrl.AppendASCII(escapedUrl.get());
+  if ((strcmp(aErrorPage, "blocked") == 0) &&
+      Preferences::GetBool(PREF_SAFEBROWSING_ALLOWOVERRIDE, true)) {
+    errorPageUrl.AppendLiteral("&o=1");
+  }
+  if (!escapedCSSClass.IsEmpty()) {
+    errorPageUrl.AppendLiteral("&s=");
+    errorPageUrl.AppendASCII(escapedCSSClass.get());
+  }
+  errorPageUrl.AppendLiteral("&c=UTF-8");
+
+  nsCOMPtr<nsICaptivePortalService> cps = do_GetService(NS_CAPTIVEPORTAL_CID);
+  int32_t cpsState;
+  if (cps && NS_SUCCEEDED(cps->GetState(&cpsState)) &&
+      cpsState == nsICaptivePortalService::LOCKED_PORTAL) {
+    errorPageUrl.AppendLiteral("&captive=true");
+  }
+
+  errorPageUrl.AppendLiteral("&d=");
+  errorPageUrl.AppendASCII(escapedDescription.get());
+
+  nsCOMPtr<nsIURI> errorPageURI;
+  nsresult rv = NS_NewURI(getter_AddRefs(errorPageURI), errorPageUrl);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return LoadErrorPage(errorPageURI, aURI, aFailedChannel);
+}
+
+nsresult nsDocShell::LoadErrorPage(nsIURI* aErrorURI, nsIURI* aFailedURI,
+                                   nsIChannel* aFailedChannel) {
+  mFailedChannel = aFailedChannel;
+  mFailedURI = aFailedURI;
+  mFailedLoadType = mLoadType;
+
+  if (mLSHE) {
+    // Abandon mLSHE's BFCache entry and create a new one.  This way, if
+    // we go back or forward to another SHEntry with the same doc
+    // identifier, the error page won't persist.
+    mLSHE->AbandonBFCacheEntry();
+  }
+
+  RefPtr<nsDocShellLoadState> loadState = new nsDocShellLoadState(aErrorURI);
+  loadState->SetTriggeringPrincipal(nsContentUtils::GetSystemPrincipal());
+  if (mBrowsingContext) {
+    loadState->SetTriggeringSandboxFlags(mBrowsingContext->GetSandboxFlags());
+    loadState->SetTriggeringWindowId(
+        mBrowsingContext->GetCurrentInnerWindowId());
+    nsPIDOMWindowInner* innerWin = mScriptGlobal->GetCurrentInnerWindow();
+    if (innerWin) {
+      loadState->SetTriggeringStorageAccess(innerWin->UsingStorageAccess());
+    }
+  }
+  loadState->SetLoadType(LOAD_ERROR_PAGE);
+  loadState->SetFirstParty(true);
+  loadState->SetSourceBrowsingContext(mBrowsingContext);
+  if (mozilla::SessionHistoryInParent() && mLoadingEntry) {
+    // We keep the loading entry for the load that failed here. If the user
+    // reloads we want to try to reload the original load, not the error page.
+    loadState->SetLoadingSessionHistoryInfo(
+        MakeUnique<LoadingSessionHistoryInfo>(*mLoadingEntry));
+  }
+  return InternalLoad(loadState);
+}
+
+NS_IMETHODIMP
+nsDocShell::Reload(uint32_t aReloadFlags) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;  // JS may not handle returning of an error code
+  }
+
+  NS_ASSERTION(((aReloadFlags & INTERNAL_LOAD_FLAGS_LOADURI_SETUP_FLAGS) == 0),
+               "Reload command not updated to use load flags!");
+  NS_ASSERTION((aReloadFlags & EXTRA_LOAD_FLAGS) == 0,
+               "Don't pass these flags to Reload");
+
+  uint32_t loadType = MAKE_LOAD_TYPE(LOAD_RELOAD_NORMAL, aReloadFlags);
+  NS_ENSURE_TRUE(IsValidLoadType(loadType), NS_ERROR_INVALID_ARG);
+
+  // Send notifications to the HistoryListener if any, about the impending
+  // reload
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (mozilla::SessionHistoryInParent()) {
+    MOZ_LOG(gSHLog, LogLevel::Debug, ("nsDocShell %p Reload", this));
+    bool forceReload = IsForceReloadType(loadType);
+    if (!XRE_IsParentProcess()) {
+      ++mPendingReloadCount;
+      RefPtr<nsDocShell> docShell(this);
+      nsCOMPtr<nsIDocumentViewer> viewer(mDocumentViewer);
+      NS_ENSURE_STATE(viewer);
+
+      bool okToUnload = true;
+      MOZ_TRY(viewer->PermitUnload(&okToUnload));
+      if (!okToUnload) {
+        return NS_OK;
+      }
+
+      RefPtr<Document> doc(GetDocument());
+      RefPtr<BrowsingContext> browsingContext(mBrowsingContext);
+      nsCOMPtr<nsIURI> currentURI(mCurrentURI);
+      nsCOMPtr<nsIReferrerInfo> referrerInfo(mReferrerInfo);
+      RefPtr<StopDetector> stopDetector = new StopDetector();
+      nsCOMPtr<nsILoadGroup> loadGroup;
+      GetLoadGroup(getter_AddRefs(loadGroup));
+      if (loadGroup) {
+        // loadGroup may be null in theory. In that case stopDetector just
+        // doesn't do anything.
+        loadGroup->AddRequest(stopDetector, nullptr);
+      }
+
+      ContentChild::GetSingleton()->SendNotifyOnHistoryReload(
+          mBrowsingContext, forceReload,
+          [docShell, doc, loadType, browsingContext, currentURI, referrerInfo,
+           loadGroup, stopDetector](
+              std::tuple<bool, Maybe<NotNull<RefPtr<nsDocShellLoadState>>>,
+                         Maybe<bool>>&& aResult) {
+            auto scopeExit = MakeScopeExit([loadGroup, stopDetector]() {
+              if (loadGroup) {
+                loadGroup->RemoveRequest(stopDetector, nullptr, NS_OK);
+              }
+            });
+
+            // Decrease mPendingReloadCount before any other early returns!
+            if (--(docShell->mPendingReloadCount) > 0) {
+              return;
+            }
+
+            if (stopDetector->Canceled()) {
+              return;
+            }
+            bool canReload;
+            Maybe<NotNull<RefPtr<nsDocShellLoadState>>> loadState;
+            Maybe<bool> reloadingActiveEntry;
+
+            std::tie(canReload, loadState, reloadingActiveEntry) = aResult;
+
+            if (!canReload) {
+              return;
+            }
+
+            if (loadState.isSome()) {
+              MOZ_LOG(
+                  gSHLog, LogLevel::Debug,
+                  ("nsDocShell %p Reload - LoadHistoryEntry", docShell.get()));
+              loadState.ref()->SetNotifiedBeforeUnloadListeners(true);
+              docShell->LoadHistoryEntry(loadState.ref(), loadType,
+                                         reloadingActiveEntry.ref());
+            } else {
+              MOZ_LOG(gSHLog, LogLevel::Debug,
+                      ("nsDocShell %p ReloadDocument", docShell.get()));
+              ReloadDocument(docShell, doc, loadType, browsingContext,
+                             currentURI, referrerInfo,
+                             /* aNotifiedBeforeUnloadListeners */ true);
+            }
+          },
+          [](mozilla::ipc::ResponseRejectReason) {});
+    } else {
+      // Parent process
+      bool canReload = false;
+      Maybe<NotNull<RefPtr<nsDocShellLoadState>>> loadState;
+      Maybe<bool> reloadingActiveEntry;
+      if (!mBrowsingContext->IsDiscarded()) {
+        mBrowsingContext->Canonical()->NotifyOnHistoryReload(
+            forceReload, canReload, loadState, reloadingActiveEntry);
+      }
+      if (canReload) {
+        if (loadState.isSome()) {
+          MOZ_LOG(gSHLog, LogLevel::Debug,
+                  ("nsDocShell %p Reload - LoadHistoryEntry", this));
+          LoadHistoryEntry(loadState.ref(), loadType,
+                           reloadingActiveEntry.ref());
+        } else {
+          MOZ_LOG(gSHLog, LogLevel::Debug,
+                  ("nsDocShell %p ReloadDocument", this));
+          RefPtr<Document> doc = GetDocument();
+          RefPtr<BrowsingContext> bc = mBrowsingContext;
+          nsCOMPtr<nsIURI> currentURI = mCurrentURI;
+          nsCOMPtr<nsIReferrerInfo> referrerInfo = mReferrerInfo;
+          ReloadDocument(this, doc, loadType, bc, currentURI, referrerInfo);
+        }
+      }
+    }
+    return NS_OK;
+  }
+
+  bool canReload = true;
+  if (rootSH) {
+    rootSH->LegacySHistory()->NotifyOnHistoryReload(&canReload);
+  }
+
+  if (!canReload) {
+    return NS_OK;
+  }
+
+  /* If you change this part of code, make sure bug 45297 does not re-occur */
+  if (mOSHE) {
+    nsCOMPtr<nsISHEntry> oshe = mOSHE;
+    return LoadHistoryEntry(
+        oshe, loadType,
+        aReloadFlags & nsIWebNavigation::LOAD_FLAGS_USER_ACTIVATION);
+  }
+
+  if (mLSHE) {  // In case a reload happened before the current load is done
+    nsCOMPtr<nsISHEntry> lshe = mLSHE;
+    return LoadHistoryEntry(
+        lshe, loadType,
+        aReloadFlags & nsIWebNavigation::LOAD_FLAGS_USER_ACTIVATION);
+  }
+
+  RefPtr<Document> doc = GetDocument();
+  RefPtr<BrowsingContext> bc = mBrowsingContext;
+  nsCOMPtr<nsIURI> currentURI = mCurrentURI;
+  nsCOMPtr<nsIReferrerInfo> referrerInfo = mReferrerInfo;
+  return ReloadDocument(this, doc, loadType, bc, currentURI, referrerInfo);
+}
+
+/* static */
+nsresult nsDocShell::ReloadDocument(nsDocShell* aDocShell, Document* aDocument,
+                                    uint32_t aLoadType,
+                                    BrowsingContext* aBrowsingContext,
+                                    nsIURI* aCurrentURI,
+                                    nsIReferrerInfo* aReferrerInfo,
+                                    bool aNotifiedBeforeUnloadListeners) {
+  if (!aDocument) {
+    return NS_OK;
+  }
+
+  // Do not inherit owner from document
+  uint32_t flags = INTERNAL_LOAD_FLAGS_NONE;
+  nsAutoString srcdoc;
+  nsIURI* baseURI = nullptr;
+  nsCOMPtr<nsIURI> originalURI;
+  nsCOMPtr<nsIURI> resultPrincipalURI;
+  bool loadReplace = false;
+
+  nsIPrincipal* triggeringPrincipal = aDocument->NodePrincipal();
+  nsCOMPtr<nsIContentSecurityPolicy> csp = aDocument->GetCsp();
+  uint32_t triggeringSandboxFlags = aDocument->GetSandboxFlags();
+  uint64_t triggeringWindowId = aDocument->InnerWindowID();
+  bool triggeringStorageAccess = aDocument->UsingStorageAccess();
+
+  nsAutoString contentTypeHint;
+  aDocument->GetContentType(contentTypeHint);
+
+  if (aDocument->IsSrcdocDocument()) {
+    aDocument->GetSrcdocData(srcdoc);
+    flags |= INTERNAL_LOAD_FLAGS_IS_SRCDOC;
+    baseURI = aDocument->GetBaseURI();
+  } else {
+    srcdoc = VoidString();
+  }
+  nsCOMPtr<nsIChannel> chan = aDocument->GetChannel();
+  if (chan) {
+    uint32_t loadFlags;
+    chan->GetLoadFlags(&loadFlags);
+    loadReplace = loadFlags & nsIChannel::LOAD_REPLACE;
+    nsCOMPtr<nsIHttpChannel> httpChan(do_QueryInterface(chan));
+    if (httpChan) {
+      httpChan->GetOriginalURI(getter_AddRefs(originalURI));
+    }
+
+    nsCOMPtr<nsILoadInfo> loadInfo = chan->LoadInfo();
+    loadInfo->GetResultPrincipalURI(getter_AddRefs(resultPrincipalURI));
+  }
+
+  if (!triggeringPrincipal) {
+    MOZ_ASSERT(false, "Reload needs a valid triggeringPrincipal");
+    return NS_ERROR_FAILURE;
+  }
+
+  // Stack variables to ensure changes to the member variables don't affect to
+  // the call.
+  nsCOMPtr<nsIURI> currentURI = aCurrentURI;
+
+  // Reload always rewrites result principal URI.
+  Maybe<nsCOMPtr<nsIURI>> emplacedResultPrincipalURI;
+  emplacedResultPrincipalURI.emplace(std::move(resultPrincipalURI));
+
+  RefPtr<WindowContext> context = aBrowsingContext->GetCurrentWindowContext();
+  RefPtr<nsDocShellLoadState> loadState = new nsDocShellLoadState(currentURI);
+  loadState->SetReferrerInfo(aReferrerInfo);
+  loadState->SetOriginalURI(originalURI);
+  loadState->SetMaybeResultPrincipalURI(emplacedResultPrincipalURI);
+  loadState->SetLoadReplace(loadReplace);
+  loadState->SetTriggeringPrincipal(triggeringPrincipal);
+  loadState->SetTriggeringSandboxFlags(triggeringSandboxFlags);
+  loadState->SetTriggeringWindowId(triggeringWindowId);
+  loadState->SetTriggeringStorageAccess(triggeringStorageAccess);
+  loadState->SetPrincipalToInherit(triggeringPrincipal);
+  loadState->SetCsp(csp);
+  loadState->SetInternalLoadFlags(flags);
+  loadState->SetTypeHint(NS_ConvertUTF16toUTF8(contentTypeHint));
+  loadState->SetLoadType(aLoadType);
+  loadState->SetFirstParty(true);
+  loadState->SetSrcdocData(srcdoc);
+  loadState->SetSourceBrowsingContext(aBrowsingContext);
+  loadState->SetBaseURI(baseURI);
+  loadState->SetHasValidUserGestureActivation(
+      context && context->HasValidTransientUserGestureActivation());
+  loadState->SetNotifiedBeforeUnloadListeners(aNotifiedBeforeUnloadListeners);
+  return aDocShell->InternalLoad(loadState);
+}
+
+NS_IMETHODIMP
+nsDocShell::Stop(uint32_t aStopFlags) {
+  // Revoke any pending event related to content viewer restoration
+  mRestorePresentationEvent.Revoke();
+
+  if (mLoadType == LOAD_ERROR_PAGE) {
+    if (mLSHE) {
+      // Since error page loads never unset mLSHE, do so now
+      SetHistoryEntryAndUpdateBC(Some(nullptr), Some<nsISHEntry*>(mLSHE));
+    }
+    mActiveEntryIsLoadingFromSessionHistory = false;
+
+    mFailedChannel = nullptr;
+    mFailedURI = nullptr;
+  }
+
+  if (nsIWebNavigation::STOP_CONTENT & aStopFlags) {
+    // Stop the document loading and animations
+    if (mDocumentViewer) {
+      nsCOMPtr<nsIDocumentViewer> viewer = mDocumentViewer;
+      viewer->Stop();
+    }
+  } else if (nsIWebNavigation::STOP_NETWORK & aStopFlags) {
+    // Stop the document loading only
+    if (mDocumentViewer) {
+      RefPtr<Document> doc = mDocumentViewer->GetDocument();
+      if (doc) {
+        doc->StopDocumentLoad();
+      }
+    }
+  }
+
+  if (nsIWebNavigation::STOP_NETWORK & aStopFlags) {
+    // Suspend any timers that were set for this loader.  We'll clear
+    // them out for good in CreateDocumentViewer.
+    if (mRefreshURIList) {
+      SuspendRefreshURIs();
+      mSavedRefreshURIList.swap(mRefreshURIList);
+      mRefreshURIList = nullptr;
+    }
+
+    // XXXbz We could also pass |this| to nsIURILoader::Stop.  That will
+    // just call Stop() on us as an nsIDocumentLoader... We need fewer
+    // redundant apis!
+    Stop();
+
+    // Clear out mChannelToDisconnectOnPageHide. This page won't go in the
+    // BFCache now, and the Stop above will have removed the DocumentChannel
+    // from the loadgroup.
+    mChannelToDisconnectOnPageHide = 0;
+  }
+
+  for (auto* child : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIWebNavigation> shellAsNav(do_QueryObject(child));
+    if (shellAsNav) {
+      shellAsNav->Stop(aStopFlags);
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDocument(Document** aDocument) {
+  NS_ENSURE_ARG_POINTER(aDocument);
+  NS_ENSURE_SUCCESS(EnsureDocumentViewer(), NS_ERROR_FAILURE);
+
+  RefPtr<Document> doc = mDocumentViewer->GetDocument();
+  if (!doc) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  doc.forget(aDocument);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCurrentURI(nsIURI** aURI) {
+  NS_ENSURE_ARG_POINTER(aURI);
+
+  nsCOMPtr<nsIURI> uri = mCurrentURI;
+  uri.forget(aURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetSessionHistoryXPCOM(nsISupports** aSessionHistory) {
+  NS_ENSURE_ARG_POINTER(aSessionHistory);
+  RefPtr<ChildSHistory> shistory = GetSessionHistory();
+  shistory.forget(aSessionHistory);
+  return NS_OK;
+}
+
+//*****************************************************************************
+// nsDocShell::nsIWebPageDescriptor
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::LoadPageAsViewSource(nsIDocShell* aOtherDocShell,
+                                 const nsAString& aURI) {
+  if (!aOtherDocShell) {
+    return NS_ERROR_INVALID_POINTER;
+  }
+  nsCOMPtr<nsIURI> newURI;
+  nsresult rv = NS_NewURI(getter_AddRefs(newURI), aURI);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  RefPtr<nsDocShellLoadState> loadState;
+  uint32_t cacheKey;
+  auto* otherDocShell = nsDocShell::Cast(aOtherDocShell);
+  if (mozilla::SessionHistoryInParent()) {
+    loadState = new nsDocShellLoadState(newURI);
+    if (!otherDocShell->FillLoadStateFromCurrentEntry(*loadState)) {
+      return NS_ERROR_INVALID_POINTER;
+    }
+    cacheKey = otherDocShell->GetCacheKeyFromCurrentEntry().valueOr(0);
+  } else {
+    nsCOMPtr<nsISHEntry> entry;
+    bool isOriginalSHE;
+    otherDocShell->GetCurrentSHEntry(getter_AddRefs(entry), &isOriginalSHE);
+    if (!entry) {
+      return NS_ERROR_INVALID_POINTER;
+    }
+    rv = entry->CreateLoadInfo(getter_AddRefs(loadState));
+    NS_ENSURE_SUCCESS(rv, rv);
+    entry->GetCacheKey(&cacheKey);
+    loadState->SetURI(newURI);
+    loadState->SetSHEntry(nullptr);
+  }
+
+  // We're doing a load of the page, via an API that
+  // is only exposed to system code.  The triggering principal for this load
+  // should be the system principal.
+  loadState->SetTriggeringPrincipal(nsContentUtils::GetSystemPrincipal());
+  loadState->SetOriginalURI(nullptr);
+  loadState->SetResultPrincipalURI(nullptr);
+
+  return InternalLoad(loadState, Some(cacheKey));
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCurrentDescriptor(nsISupports** aPageDescriptor) {
+  MOZ_ASSERT(aPageDescriptor, "Null out param?");
+
+  *aPageDescriptor = nullptr;
+
+  nsISHEntry* src = mOSHE ? mOSHE : mLSHE;
+  if (src) {
+    nsCOMPtr<nsISHEntry> dest;
+
+    nsresult rv = src->Clone(getter_AddRefs(dest));
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    // null out inappropriate cloned attributes...
+    dest->SetParent(nullptr);
+    dest->SetIsSubFrame(false);
+
+    return CallQueryInterface(dest, aPageDescriptor);
+  }
+
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+already_AddRefed<nsIInputStream> nsDocShell::GetPostDataFromCurrentEntry()
+    const {
+  nsCOMPtr<nsIInputStream> postData;
+  if (mozilla::SessionHistoryInParent()) {
+    if (mActiveEntry) {
+      postData = mActiveEntry->GetPostData();
+    } else if (mLoadingEntry) {
+      postData = mLoadingEntry->mInfo.GetPostData();
+    }
+  } else {
+    if (mOSHE) {
+      postData = mOSHE->GetPostData();
+    } else if (mLSHE) {
+      postData = mLSHE->GetPostData();
+    }
+  }
+
+  return postData.forget();
+}
+
+Maybe<uint32_t> nsDocShell::GetCacheKeyFromCurrentEntry() const {
+  if (mozilla::SessionHistoryInParent()) {
+    if (mActiveEntry) {
+      return Some(mActiveEntry->GetCacheKey());
+    }
+
+    if (mLoadingEntry) {
+      return Some(mLoadingEntry->mInfo.GetCacheKey());
+    }
+  } else {
+    if (mOSHE) {
+      return Some(mOSHE->GetCacheKey());
+    }
+
+    if (mLSHE) {
+      return Some(mLSHE->GetCacheKey());
+    }
+  }
+
+  return Nothing();
+}
+
+bool nsDocShell::FillLoadStateFromCurrentEntry(
+    nsDocShellLoadState& aLoadState) {
+  if (mLoadingEntry) {
+    mLoadingEntry->mInfo.FillLoadInfo(aLoadState);
+    return true;
+  }
+  if (mActiveEntry) {
+    mActiveEntry->FillLoadInfo(aLoadState);
+    return true;
+  }
+  return false;
+}
+
+//*****************************************************************************
+// nsDocShell::nsIBaseWindow
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::InitWindow(nativeWindow aParentNativeWindow,
+                       nsIWidget* aParentWidget, int32_t aX, int32_t aY,
+                       int32_t aWidth, int32_t aHeight) {
+  SetParentWidget(aParentWidget);
+  SetPositionAndSize(aX, aY, aWidth, aHeight, 0);
+  NS_ENSURE_TRUE(Initialize(), NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::Destroy() {
+  // XXX: We allow this function to be called just once.  If you are going to
+  // reset new variables in this function, please make sure the variables will
+  // never be re-initialized.  Adding assertions to check |mIsBeingDestroyed|
+  // in the setter functions for the variables would be enough.
+  if (mIsBeingDestroyed) {
+    return NS_ERROR_DOCSHELL_DYING;
+  }
+
+  NS_ASSERTION(mItemType == typeContent || mItemType == typeChrome,
+               "Unexpected item type in docshell");
+
+  nsCOMPtr<nsIObserverService> serv = services::GetObserverService();
+  if (serv) {
+    const char* msg = mItemType == typeContent
+                          ? NS_WEBNAVIGATION_DESTROY
+                          : NS_CHROME_WEBNAVIGATION_DESTROY;
+    serv->NotifyObservers(GetAsSupports(this), msg, nullptr);
+  }
+
+  mIsBeingDestroyed = true;
+
+  // Brak the cycle with the initial client, if present.
+  mInitialClientSource.reset();
+
+  // Make sure to blow away our mLoadingURI just in case.  No loads
+  // from inside this pagehide.
+  mLoadingURI = nullptr;
+
+  // Fire unload event before we blow anything away.
+  (void)FirePageHideNotification(true);
+
+  // Clear pointers to any detached nsEditorData that's lying
+  // around in shistory entries. Breaks cycle. See bug 430921.
+  if (mOSHE) {
+    mOSHE->SetEditorData(nullptr);
+  }
+  if (mLSHE) {
+    mLSHE->SetEditorData(nullptr);
+  }
+
+  // Note: mContentListener can be null if Init() failed and we're being
+  // called from the destructor.
+  if (mContentListener) {
+    mContentListener->DropDocShellReference();
+    mContentListener->SetParentContentListener(nullptr);
+    // Note that we do NOT set mContentListener to null here; that
+    // way if someone tries to do a load in us after this point
+    // the nsDSURIContentListener will block it.  All of which
+    // means that we should do this before calling Stop(), of
+    // course.
+  }
+
+  // Stop any URLs that are currently being loaded...
+  Stop(nsIWebNavigation::STOP_ALL);
+
+  mEditorData = nullptr;
+
+  // Save the state of the current document, before destroying the window.
+  // This is needed to capture the state of a frameset when the new document
+  // causes the frameset to be destroyed...
+  PersistLayoutHistoryState();
+
+  // Remove this docshell from its parent's child list
+  nsCOMPtr<nsIDocShellTreeItem> docShellParentAsItem =
+      do_QueryInterface(GetAsSupports(mParent));
+  if (docShellParentAsItem) {
+    docShellParentAsItem->RemoveChild(this);
+  }
+
+  if (mDocumentViewer) {
+    mDocumentViewer->Close(nullptr);
+    mDocumentViewer->Destroy();
+    mDocumentViewer = nullptr;
+  }
+
+  nsDocLoader::Destroy();
+
+  mParentWidget = nullptr;
+  SetCurrentURIInternal(nullptr);
+
+  if (mScriptGlobal) {
+    mScriptGlobal->DetachFromDocShell(!mWillChangeProcess);
+    mScriptGlobal = nullptr;
+  }
+
+  if (GetSessionHistory()) {
+    // We want to destroy these content viewers now rather than
+    // letting their destruction wait for the session history
+    // entries to get garbage collected.  (Bug 488394)
+    GetSessionHistory()->EvictLocalDocumentViewers();
+  }
+
+  if (mWillChangeProcess && !mBrowsingContext->IsDiscarded()) {
+    mBrowsingContext->PrepareForProcessChange();
+  }
+
+  SetTreeOwner(nullptr);
+
+  mBrowserChild = nullptr;
+
+  mChromeEventHandler = nullptr;
+
+  // Cancel any timers that were set for this docshell; this is needed
+  // to break the cycle between us and the timers.
+  CancelRefreshURITimers();
+
+  return NS_OK;
+}
+
+double nsDocShell::GetWidgetCSSToDeviceScale() {
+  if (mParentWidget) {
+    return mParentWidget->GetDefaultScale().scale;
+  }
+  if (nsCOMPtr<nsIBaseWindow> ownerWindow = do_QueryInterface(mTreeOwner)) {
+    return ownerWindow->GetWidgetCSSToDeviceScale();
+  }
+  return 1.0;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDevicePixelsPerDesktopPixel(double* aScale) {
+  if (mParentWidget) {
+    *aScale = mParentWidget->GetDesktopToDeviceScale().scale;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIBaseWindow> ownerWindow(do_QueryInterface(mTreeOwner));
+  if (ownerWindow) {
+    return ownerWindow->GetDevicePixelsPerDesktopPixel(aScale);
+  }
+
+  *aScale = 1.0;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetPosition(int32_t aX, int32_t aY) {
+  mBounds.MoveTo(aX, aY);
+
+  if (mDocumentViewer) {
+    NS_ENSURE_SUCCESS(mDocumentViewer->Move(aX, aY), NS_ERROR_FAILURE);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetPositionDesktopPix(int32_t aX, int32_t aY) {
+  nsCOMPtr<nsIBaseWindow> ownerWindow(do_QueryInterface(mTreeOwner));
+  if (ownerWindow) {
+    return ownerWindow->SetPositionDesktopPix(aX, aY);
+  }
+
+  double scale = 1.0;
+  GetDevicePixelsPerDesktopPixel(&scale);
+  return SetPosition(NSToIntRound(aX * scale), NSToIntRound(aY * scale));
+}
+
+NS_IMETHODIMP
+nsDocShell::GetPosition(int32_t* aX, int32_t* aY) {
+  return GetPositionAndSize(aX, aY, nullptr, nullptr);
+}
+
+NS_IMETHODIMP
+nsDocShell::SetSize(int32_t aWidth, int32_t aHeight, bool aRepaint) {
+  int32_t x = 0, y = 0;
+  GetPosition(&x, &y);
+  return SetPositionAndSize(x, y, aWidth, aHeight,
+                            aRepaint ? nsIBaseWindow::eRepaint : 0);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetSize(int32_t* aWidth, int32_t* aHeight) {
+  return GetPositionAndSize(nullptr, nullptr, aWidth, aHeight);
+}
+
+NS_IMETHODIMP
+nsDocShell::SetPositionAndSize(int32_t aX, int32_t aY, int32_t aWidth,
+                               int32_t aHeight, uint32_t aFlags) {
+  mBounds.SetRect(aX, aY, aWidth, aHeight);
+
+  // Hold strong ref, since SetBounds can make us null out mDocumentViewer
+  nsCOMPtr<nsIDocumentViewer> viewer = mDocumentViewer;
+  if (viewer) {
+    uint32_t cvflags = (aFlags & nsIBaseWindow::eDelayResize)
+                           ? nsIDocumentViewer::eDelayResize
+                           : 0;
+    // XXX Border figured in here or is that handled elsewhere?
+    nsresult rv = viewer->SetBoundsWithFlags(mBounds, cvflags);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetPositionAndSize(int32_t* aX, int32_t* aY, int32_t* aWidth,
+                               int32_t* aHeight) {
+  if (mParentWidget) {
+    // ensure size is up-to-date if window has changed resolution
+    LayoutDeviceIntRect r = mParentWidget->GetClientBounds();
+    SetPositionAndSize(mBounds.X(), mBounds.Y(), r.Width(), r.Height(), 0);
+  }
+
+  // We should really consider just getting this information from
+  // our window instead of duplicating the storage and code...
+  if (aWidth || aHeight) {
+    // Caller wants to know our size; make sure to give them up to
+    // date information.
+    RefPtr<Document> doc(do_GetInterface(GetAsSupports(mParent)));
+    if (doc) {
+      doc->FlushPendingNotifications(FlushType::Layout);
+    }
+  }
+
+  DoGetPositionAndSize(aX, aY, aWidth, aHeight);
+  return NS_OK;
+}
+
+void nsDocShell::DoGetPositionAndSize(int32_t* aX, int32_t* aY, int32_t* aWidth,
+                                      int32_t* aHeight) {
+  if (aX) {
+    *aX = mBounds.X();
+  }
+  if (aY) {
+    *aY = mBounds.Y();
+  }
+  if (aWidth) {
+    *aWidth = mBounds.Width();
+  }
+  if (aHeight) {
+    *aHeight = mBounds.Height();
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::SetDimensions(DimensionRequest&& aRequest) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDimensions(DimensionKind aDimensionKind, int32_t* aX,
+                          int32_t* aY, int32_t* aCX, int32_t* aCY) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShell::Repaint(bool aForce) {
+  PresShell* presShell = GetPresShell();
+  NS_ENSURE_TRUE(presShell, NS_ERROR_FAILURE);
+
+  RefPtr<nsViewManager> viewManager = presShell->GetViewManager();
+  NS_ENSURE_TRUE(viewManager, NS_ERROR_FAILURE);
+
+  viewManager->InvalidateAllViews();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetParentWidget(nsIWidget** aParentWidget) {
+  NS_ENSURE_ARG_POINTER(aParentWidget);
+
+  *aParentWidget = mParentWidget;
+  NS_IF_ADDREF(*aParentWidget);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetParentWidget(nsIWidget* aParentWidget) {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+  mParentWidget = aParentWidget;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetParentNativeWindow(nativeWindow* aParentNativeWindow) {
+  NS_ENSURE_ARG_POINTER(aParentNativeWindow);
+
+  if (mParentWidget) {
+    *aParentNativeWindow = mParentWidget->GetNativeData(NS_NATIVE_WIDGET);
+  } else {
+    *aParentNativeWindow = nullptr;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetParentNativeWindow(nativeWindow aParentNativeWindow) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetNativeHandle(nsAString& aNativeHandle) {
+  // the nativeHandle should be accessed from nsIAppWindow
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetVisibility(bool* aVisibility) {
+  NS_ENSURE_ARG_POINTER(aVisibility);
+
+  *aVisibility = false;
+
+  if (!mDocumentViewer) {
+    return NS_OK;
+  }
+
+  PresShell* presShell = GetPresShell();
+  if (!presShell) {
+    return NS_OK;
+  }
+
+  // get the view manager
+  nsViewManager* vm = presShell->GetViewManager();
+  NS_ENSURE_TRUE(vm, NS_ERROR_FAILURE);
+
+  // get the root view
+  nsView* view = vm->GetRootView();  // views are not ref counted
+  NS_ENSURE_TRUE(view, NS_ERROR_FAILURE);
+
+  // if our root view is hidden, we are not visible
+  if (view->GetVisibility() == ViewVisibility::Hide) {
+    return NS_OK;
+  }
+
+  // otherwise, we must walk up the document and view trees checking
+  // for a hidden view, unless we're an off screen browser, which
+  // would make this test meaningless.
+
+  RefPtr<nsDocShell> docShell = this;
+  RefPtr<nsDocShell> parentItem = docShell->GetInProcessParentDocshell();
+  while (parentItem) {
+    // Null-check for crash in bug 267804
+    if (!parentItem->GetPresShell()) {
+      MOZ_ASSERT_UNREACHABLE("parent docshell has null pres shell");
+      return NS_OK;
+    }
+
+    vm = docShell->GetPresShell()->GetViewManager();
+    if (vm) {
+      view = vm->GetRootView();
+    }
+
+    if (view) {
+      view = view->GetParent();  // anonymous inner view
+      if (view) {
+        view = view->GetParent();  // subdocumentframe's view
+      }
+    }
+
+    nsIFrame* frame = view ? view->GetFrame() : nullptr;
+    if (frame && !frame->IsVisibleConsideringAncestors(
+                     nsIFrame::VISIBILITY_CROSS_CHROME_CONTENT_BOUNDARY)) {
+      return NS_OK;
+    }
+
+    docShell = parentItem;
+    parentItem = docShell->GetInProcessParentDocshell();
+  }
+
+  nsCOMPtr<nsIBaseWindow> treeOwnerAsWin(do_QueryInterface(mTreeOwner));
+  if (!treeOwnerAsWin) {
+    *aVisibility = true;
+    return NS_OK;
+  }
+
+  // Check with the tree owner as well to give embedders a chance to
+  // expose visibility as well.
+  nsresult rv = treeOwnerAsWin->GetVisibility(aVisibility);
+  if (rv == NS_ERROR_NOT_IMPLEMENTED) {
+    // The tree owner had no opinion on our visibility.
+    *aVisibility = true;
+    return NS_OK;
+  }
+  return rv;
+}
+
+void nsDocShell::ActivenessMaybeChanged() {
+  const bool isActive = mBrowsingContext->IsActive();
+  if (RefPtr<PresShell> presShell = GetPresShell()) {
+    presShell->ActivenessMaybeChanged();
+  }
+
+  // Tell the window about it
+  if (mScriptGlobal) {
+    mScriptGlobal->SetIsBackground(!isActive);
+    if (RefPtr<Document> doc = mScriptGlobal->GetExtantDoc()) {
+      // Update orientation when the top-level browsing context becomes active.
+      if (isActive && mBrowsingContext->IsTop()) {
+        // We only care about the top-level browsing context.
+        auto orientation = mBrowsingContext->GetOrientationLock();
+        ScreenOrientation::UpdateActiveOrientationLock(orientation);
+      }
+
+      doc->PostVisibilityUpdateEvent();
+    }
+  }
+
+  // Tell the nsDOMNavigationTiming about it
+  RefPtr<nsDOMNavigationTiming> timing = mTiming;
+  if (!timing && mDocumentViewer) {
+    if (Document* doc = mDocumentViewer->GetDocument()) {
+      timing = doc->GetNavigationTiming();
+    }
+  }
+  if (timing) {
+    timing->NotifyDocShellStateChanged(
+        isActive ? nsDOMNavigationTiming::DocShellState::eActive
+                 : nsDOMNavigationTiming::DocShellState::eInactive);
+  }
+
+  // Restart or stop meta refresh timers if necessary
+  if (mDisableMetaRefreshWhenInactive) {
+    if (isActive) {
+      ResumeRefreshURIs();
+    } else {
+      SuspendRefreshURIs();
+    }
+  }
+
+  if (InputTaskManager::CanSuspendInputEvent()) {
+    mBrowsingContext->Group()->UpdateInputTaskManagerIfNeeded(isActive);
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::SetDefaultLoadFlags(uint32_t aDefaultLoadFlags) {
+  if (!mWillChangeProcess) {
+    // Intentionally ignoring handling discarded browsing contexts.
+    Unused << mBrowsingContext->SetDefaultLoadFlags(aDefaultLoadFlags);
+  } else {
+    // Bug 1623565: DevTools tries to clean up defaultLoadFlags on
+    // shutdown. Sorry DevTools, your DocShell is in another process.
+    NS_WARNING("nsDocShell::SetDefaultLoadFlags called on Zombie DocShell");
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDefaultLoadFlags(uint32_t* aDefaultLoadFlags) {
+  *aDefaultLoadFlags = mBrowsingContext->GetDefaultLoadFlags();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetFailedChannel(nsIChannel** aFailedChannel) {
+  NS_ENSURE_ARG_POINTER(aFailedChannel);
+  Document* doc = GetDocument();
+  if (!doc) {
+    *aFailedChannel = nullptr;
+    return NS_OK;
+  }
+  NS_IF_ADDREF(*aFailedChannel = doc->GetFailedChannel());
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetVisibility(bool aVisibility) {
+  // Show()/Hide() may change mDocumentViewer.
+  nsCOMPtr<nsIDocumentViewer> viewer = mDocumentViewer;
+  if (!viewer) {
+    return NS_OK;
+  }
+  if (aVisibility) {
+    viewer->Show();
+  } else {
+    viewer->Hide();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetEnabled(bool* aEnabled) {
+  NS_ENSURE_ARG_POINTER(aEnabled);
+  *aEnabled = true;
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetEnabled(bool aEnabled) { return NS_ERROR_NOT_IMPLEMENTED; }
+
+NS_IMETHODIMP
+nsDocShell::GetMainWidget(nsIWidget** aMainWidget) {
+  // We don't create our own widget, so simply return the parent one.
+  return GetParentWidget(aMainWidget);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetTitle(nsAString& aTitle) {
+  aTitle = mTitle;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetTitle(const nsAString& aTitle) {
+  // Avoid unnecessary updates of the title if the URI and the title haven't
+  // changed.
+  if (mTitleValidForCurrentURI && mTitle == aTitle) {
+    return NS_OK;
+  }
+
+  // Store local title
+  mTitle = aTitle;
+  mTitleValidForCurrentURI = true;
+
+  // When title is set on the top object it should then be passed to the
+  // tree owner.
+  if (mBrowsingContext->IsTop()) {
+    nsCOMPtr<nsIBaseWindow> treeOwnerAsWin(do_QueryInterface(mTreeOwner));
+    if (treeOwnerAsWin) {
+      treeOwnerAsWin->SetTitle(aTitle);
+    }
+  }
+
+  if (mCurrentURI && mLoadType != LOAD_ERROR_PAGE) {
+    UpdateGlobalHistoryTitle(mCurrentURI);
+  }
+
+  // Update SessionHistory with the document's title.
+  if (mLoadType != LOAD_BYPASS_HISTORY && mLoadType != LOAD_ERROR_PAGE) {
+    SetTitleOnHistoryEntry(true);
+  }
+
+  return NS_OK;
+}
+
+void nsDocShell::SetTitleOnHistoryEntry(bool aUpdateEntryInSessionHistory) {
+  if (mOSHE) {
+    mOSHE->SetTitle(mTitle);
+  }
+
+  if (mActiveEntry && mBrowsingContext) {
+    mActiveEntry->SetTitle(mTitle);
+    if (aUpdateEntryInSessionHistory) {
+      if (XRE_IsParentProcess()) {
+        SessionHistoryEntry* entry =
+            mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+        if (entry) {
+          entry->SetTitle(mTitle);
+        }
+      } else {
+        mozilla::Unused
+            << ContentChild::GetSingleton()->SendSessionHistoryEntryTitle(
+                   mBrowsingContext, mTitle);
+      }
+    }
+  }
+}
+
+nsPoint nsDocShell::GetCurScrollPos() {
+  nsPoint scrollPos;
+  if (nsIScrollableFrame* sf = GetRootScrollFrame()) {
+    scrollPos = sf->GetVisualViewportOffset();
+  }
+  return scrollPos;
+}
+
+nsresult nsDocShell::SetCurScrollPosEx(int32_t aCurHorizontalPos,
+                                       int32_t aCurVerticalPos) {
+  nsIScrollableFrame* sf = GetRootScrollFrame();
+  NS_ENSURE_TRUE(sf, NS_ERROR_FAILURE);
+
+  ScrollMode scrollMode =
+      sf->IsSmoothScroll() ? ScrollMode::SmoothMsd : ScrollMode::Instant;
+
+  nsPoint targetPos(aCurHorizontalPos, aCurVerticalPos);
+  sf->ScrollTo(targetPos, scrollMode);
+
+  // Set the visual viewport offset as well.
+
+  RefPtr<PresShell> presShell = GetPresShell();
+  NS_ENSURE_TRUE(presShell, NS_ERROR_FAILURE);
+
+  nsPresContext* presContext = presShell->GetPresContext();
+  NS_ENSURE_TRUE(presContext, NS_ERROR_FAILURE);
+
+  // Only the root content document can have a distinct visual viewport offset.
+  if (!presContext->IsRootContentDocumentCrossProcess()) {
+    return NS_OK;
+  }
+
+  // Not on a platform with a distinct visual viewport - don't bother setting
+  // the visual viewport offset.
+  if (!presShell->IsVisualViewportSizeSet()) {
+    return NS_OK;
+  }
+
+  presShell->ScrollToVisual(targetPos, layers::FrameMetrics::eMainThread,
+                            scrollMode);
+
+  return NS_OK;
+}
+
+void nsDocShell::SetScrollbarPreference(mozilla::ScrollbarPreference aPref) {
+  if (mScrollbarPref == aPref) {
+    return;
+  }
+  mScrollbarPref = aPref;
+  auto* ps = GetPresShell();
+  if (!ps) {
+    return;
+  }
+  nsIFrame* scrollFrame = ps->GetRootScrollFrame();
+  if (!scrollFrame) {
+    return;
+  }
+  ps->FrameNeedsReflow(scrollFrame,
+                       IntrinsicDirty::FrameAncestorsAndDescendants,
+                       NS_FRAME_IS_DIRTY);
+}
+
+//*****************************************************************************
+// nsDocShell::nsIRefreshURI
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::RefreshURI(nsIURI* aURI, nsIPrincipal* aPrincipal,
+                       uint32_t aDelay) {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  NS_ENSURE_ARG(aURI);
+
+  /* Check if Meta refresh/redirects are permitted. Some
+   * embedded applications may not want to do this.
+   * Must do this before sending out NOTIFY_REFRESH events
+   * because listeners may have side effects (e.g. displaying a
+   * button to manually trigger the refresh later).
+   */
+  bool allowRedirects = true;
+  GetAllowMetaRedirects(&allowRedirects);
+  if (!allowRedirects) {
+    return NS_OK;
+  }
+
+  // If any web progress listeners are listening for NOTIFY_REFRESH events,
+  // give them a chance to block this refresh.
+  bool sameURI;
+  nsresult rv = aURI->Equals(mCurrentURI, &sameURI);
+  if (NS_FAILED(rv)) {
+    sameURI = false;
+  }
+  if (!RefreshAttempted(this, aURI, aDelay, sameURI)) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsITimerCallback> refreshTimer =
+      new nsRefreshTimer(this, aURI, aPrincipal, aDelay);
+
+  BusyFlags busyFlags = GetBusyFlags();
+
+  if (!mRefreshURIList) {
+    mRefreshURIList = nsArray::Create();
+  }
+
+  if (busyFlags & BUSY_FLAGS_BUSY ||
+      (!mBrowsingContext->IsActive() && mDisableMetaRefreshWhenInactive)) {
+    // We don't  want to create the timer right now. Instead queue up the
+    // request and trigger the timer in EndPageLoad() or whenever we become
+    // active.
+    mRefreshURIList->AppendElement(refreshTimer);
+  } else {
+    // There is no page loading going on right now.  Create the
+    // timer and fire it right away.
+    nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
+    NS_ENSURE_TRUE(win, NS_ERROR_FAILURE);
+
+    nsCOMPtr<nsITimer> timer;
+    MOZ_TRY_VAR(timer, NS_NewTimerWithCallback(refreshTimer, aDelay,
+                                               nsITimer::TYPE_ONE_SHOT));
+
+    mRefreshURIList->AppendElement(timer);  // owning timer ref
+  }
+  return NS_OK;
+}
+
+nsresult nsDocShell::ForceRefreshURIFromTimer(nsIURI* aURI,
+                                              nsIPrincipal* aPrincipal,
+                                              uint32_t aDelay,
+                                              nsITimer* aTimer) {
+  MOZ_ASSERT(aTimer, "Must have a timer here");
+
+  // Remove aTimer from mRefreshURIList if needed
+  if (mRefreshURIList) {
+    uint32_t n = 0;
+    mRefreshURIList->GetLength(&n);
+
+    for (uint32_t i = 0; i < n; ++i) {
+      nsCOMPtr<nsITimer> timer = do_QueryElementAt(mRefreshURIList, i);
+      if (timer == aTimer) {
+        mRefreshURIList->RemoveElementAt(i);
+        break;
+      }
+    }
+  }
+
+  return ForceRefreshURI(aURI, aPrincipal, aDelay);
+}
+
+NS_IMETHODIMP
+nsDocShell::ForceRefreshURI(nsIURI* aURI, nsIPrincipal* aPrincipal,
+                            uint32_t aDelay) {
+  NS_ENSURE_ARG(aURI);
+
+  RefPtr<nsDocShellLoadState> loadState = new nsDocShellLoadState(aURI);
+  loadState->SetOriginalURI(mCurrentURI);
+  loadState->SetResultPrincipalURI(aURI);
+  loadState->SetResultPrincipalURIIsSome(true);
+  loadState->SetKeepResultPrincipalURIIfSet(true);
+  loadState->SetIsMetaRefresh(true);
+
+  // Set the triggering pricipal to aPrincipal if available, or current
+  // document's principal otherwise.
+  nsCOMPtr<nsIPrincipal> principal = aPrincipal;
+  RefPtr<Document> doc = GetDocument();
+  if (!principal) {
+    if (!doc) {
+      return NS_ERROR_FAILURE;
+    }
+    principal = doc->NodePrincipal();
+  }
+  loadState->SetTriggeringPrincipal(principal);
+  if (doc) {
+    loadState->SetCsp(doc->GetCsp());
+    loadState->SetHasValidUserGestureActivation(
+        doc->HasValidTransientUserGestureActivation());
+    loadState->SetTriggeringSandboxFlags(doc->GetSandboxFlags());
+    loadState->SetTriggeringWindowId(doc->InnerWindowID());
+    loadState->SetTriggeringStorageAccess(doc->UsingStorageAccess());
+  }
+
+  loadState->SetPrincipalIsExplicit(true);
+
+  /* Check if this META refresh causes a redirection
+   * to another site.
+   */
+  bool equalUri = false;
+  nsresult rv = aURI->Equals(mCurrentURI, &equalUri);
+
+  nsCOMPtr<nsIReferrerInfo> referrerInfo;
+  if (NS_SUCCEEDED(rv) && !equalUri && aDelay <= REFRESH_REDIRECT_TIMER) {
+    /* It is a META refresh based redirection within the threshold time
+     * we have in mind (15000 ms as defined by REFRESH_REDIRECT_TIMER).
+     * Pass a REPLACE flag to LoadURI().
+     */
+    loadState->SetLoadType(LOAD_REFRESH_REPLACE);
+
+    /* For redirects we mimic HTTP, which passes the
+     * original referrer.
+     * We will pass in referrer but will not send to server
+     */
+    if (mReferrerInfo) {
+      referrerInfo = static_cast<ReferrerInfo*>(mReferrerInfo.get())
+                         ->CloneWithNewSendReferrer(false);
+    }
+  } else {
+    loadState->SetLoadType(LOAD_REFRESH);
+    /* We do need to pass in a referrer, but we don't want it to
+     * be sent to the server.
+     * For most refreshes the current URI is an appropriate
+     * internal referrer.
+     */
+    referrerInfo = new ReferrerInfo(mCurrentURI, ReferrerPolicy::_empty, false);
+  }
+
+  loadState->SetReferrerInfo(referrerInfo);
+  loadState->SetLoadFlags(
+      nsIWebNavigation::LOAD_FLAGS_DISALLOW_INHERIT_PRINCIPAL);
+  loadState->SetFirstParty(true);
+
+  /*
+   * LoadURI(...) will cancel all refresh timers... This causes the
+   * Timer and its refreshData instance to be released...
+   */
+  LoadURI(loadState, false);
+
+  return NS_OK;
+}
+
+static const char16_t* SkipASCIIWhitespace(const char16_t* aStart,
+                                           const char16_t* aEnd) {
+  const char16_t* iter = aStart;
+  while (iter != aEnd && mozilla::IsAsciiWhitespace(*iter)) {
+    ++iter;
+  }
+  return iter;
+}
+
+static std::tuple<const char16_t*, const char16_t*> ExtractURLString(
+    const char16_t* aPosition, const char16_t* aEnd) {
+  MOZ_ASSERT(aPosition != aEnd);
+
+  // 1. Let urlString be the substring of input from the code point at
+  //    position to the end of the string.
+  const char16_t* urlStart = aPosition;
+  const char16_t* urlEnd = aEnd;
+
+  // 2. If the code point in input pointed to by position is U+0055 (U) or
+  //    U+0075 (u), then advance position to the next code point.
+  //    Otherwise, jump to the step labeled skip quotes.
+  if (*aPosition == 'U' || *aPosition == 'u') {
+    ++aPosition;
+
+    // 3. If the code point in input pointed to by position is U+0052 (R) or
+    //    U+0072 (r), then advance position to the next code point.
+    //    Otherwise, jump to the step labeled parse.
+    if (aPosition == aEnd || (*aPosition != 'R' && *aPosition != 'r')) {
+      return std::make_tuple(urlStart, urlEnd);
+    }
+
+    ++aPosition;
+
+    // 4. If the code point in input pointed to by position is U+004C (L) or
+    //    U+006C (l), then advance position to the next code point.
+    //    Otherwise, jump to the step labeled parse.
+    if (aPosition == aEnd || (*aPosition != 'L' && *aPosition != 'l')) {
+      return std::make_tuple(urlStart, urlEnd);
+    }
+
+    ++aPosition;
+
+    // 5. Skip ASCII whitespace within input given position.
+    aPosition = SkipASCIIWhitespace(aPosition, aEnd);
+
+    // 6. If the code point in input pointed to by position is U+003D (=),
+    //    then advance position to the next code point. Otherwise, jump to
+    //    the step labeled parse.
+    if (aPosition == aEnd || *aPosition != '=') {
+      return std::make_tuple(urlStart, urlEnd);
+    }
+
+    ++aPosition;
+
+    // 7. Skip ASCII whitespace within input given position.
+    aPosition = SkipASCIIWhitespace(aPosition, aEnd);
+  }
+
+  // 8. Skip quotes: If the code point in input pointed to by position is
+  //    U+0027 (') or U+0022 ("), then let quote be that code point, and
+  //    advance position to the next code point. Otherwise, let quote be
+  //    the empty string.
+  Maybe<char> quote;
+  if (aPosition != aEnd && (*aPosition == '\'' || *aPosition == '"')) {
+    quote.emplace(*aPosition);
+    ++aPosition;
+  }
+
+  // 9. Set urlString to the substring of input from the code point at
+  //    position to the end of the string.
+  urlStart = aPosition;
+  urlEnd = aEnd;
+
+  // 10. If quote is not the empty string, and there is a code point in
+  //     urlString equal to quote, then truncate urlString at that code
+  //     point, so that it and all subsequent code points are removed.
+  const char16_t* quotePos;
+  if (quote.isSome() &&
+      (quotePos = nsCharTraits<char16_t>::find(
+           urlStart, std::distance(urlStart, aEnd), quote.value()))) {
+    urlEnd = quotePos;
+  }
+
+  return std::make_tuple(urlStart, urlEnd);
+}
+
+void nsDocShell::SetupRefreshURIFromHeader(Document* aDocument,
+                                           const nsAString& aHeader) {
+  if (mIsBeingDestroyed) {
+    return;
+  }
+
+  const char16_t* position = aHeader.BeginReading();
+  const char16_t* end = aHeader.EndReading();
+
+  // See
+  // https://html.spec.whatwg.org/#pragma-directives:shared-declarative-refresh-steps.
+
+  // 3. Skip ASCII whitespace
+  position = SkipASCIIWhitespace(position, end);
+
+  // 4. Let time be 0.
+  CheckedInt<uint32_t> milliSeconds;
+
+  // 5. Collect a sequence of code points that are ASCII digits
+  const char16_t* digitsStart = position;
+  while (position != end && mozilla::IsAsciiDigit(*position)) {
+    ++position;
+  }
+
+  if (position == digitsStart) {
+    // 6. If timeString is the empty string, then:
+    //    1. If the code point in input pointed to by position is not U+002E
+    //       (.), then return.
+    if (position == end || *position != '.') {
+      return;
+    }
+  } else {
+    // 7. Otherwise, set time to the result of parsing timeString using the
+    //    rules for parsing non-negative integers.
+    nsContentUtils::ParseHTMLIntegerResultFlags result;
+    uint32_t seconds =
+        nsContentUtils::ParseHTMLInteger(digitsStart, position, &result);
+    MOZ_ASSERT(!(result & nsContentUtils::eParseHTMLInteger_Negative));
+    if (result & nsContentUtils::eParseHTMLInteger_Error) {
+      // The spec assumes no errors here (since we only pass ASCII digits in),
+      // but we can still overflow, so this block should deal with that (and
+      // only that).
+      MOZ_ASSERT(!(result & nsContentUtils::eParseHTMLInteger_ErrorOverflow));
+      return;
+    }
+    MOZ_ASSERT(
+        !(result & nsContentUtils::eParseHTMLInteger_DidNotConsumeAllInput));
+
+    milliSeconds = seconds;
+    milliSeconds *= 1000;
+    if (!milliSeconds.isValid()) {
+      return;
+    }
+  }
+
+  // 8. Collect a sequence of code points that are ASCII digits and U+002E FULL
+  //    STOP characters (.) from input given position. Ignore any collected
+  //    characters.
+  while (position != end &&
+         (mozilla::IsAsciiDigit(*position) || *position == '.')) {
+    ++position;
+  }
+
+  // 9. Let urlRecord be document's URL.
+  nsCOMPtr<nsIURI> urlRecord(aDocument->GetDocumentURI());
+
+  // 10. If position is not past the end of input
+  if (position != end) {
+    // 1. If the code point in input pointed to by position is not U+003B (;),
+    //    U+002C (,), or ASCII whitespace, then return.
+    if (*position != ';' && *position != ',' &&
+        !mozilla::IsAsciiWhitespace(*position)) {
+      return;
+    }
+
+    // 2. Skip ASCII whitespace within input given position.
+    position = SkipASCIIWhitespace(position, end);
+
+    // 3. If the code point in input pointed to by position is U+003B (;) or
+    //    U+002C (,), then advance position to the next code point.
+    if (position != end && (*position == ';' || *position == ',')) {
+      ++position;
+
+      // 4. Skip ASCII whitespace within input given position.
+      position = SkipASCIIWhitespace(position, end);
+    }
+
+    // 11. If position is not past the end of input, then:
+    if (position != end) {
+      const char16_t* urlStart;
+      const char16_t* urlEnd;
+
+      // 1-10. See ExtractURLString.
+      std::tie(urlStart, urlEnd) = ExtractURLString(position, end);
+
+      // 11. Parse: Parse urlString relative to document. If that fails, return.
+      //     Otherwise, set urlRecord to the resulting URL record.
+      nsresult rv =
+          NS_NewURI(getter_AddRefs(urlRecord),
+                    Substring(urlStart, std::distance(urlStart, urlEnd)),
+                    /* charset = */ nullptr, aDocument->GetDocBaseURI());
+      NS_ENSURE_SUCCESS_VOID(rv);
+    }
+  }
+
+  nsIPrincipal* principal = aDocument->NodePrincipal();
+  nsCOMPtr<nsIScriptSecurityManager> securityManager =
+      nsContentUtils::GetSecurityManager();
+  nsresult rv = securityManager->CheckLoadURIWithPrincipal(
+      principal, urlRecord,
+      nsIScriptSecurityManager::LOAD_IS_AUTOMATIC_DOCUMENT_REPLACEMENT,
+      aDocument->InnerWindowID());
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  bool isjs = true;
+  rv = NS_URIChainHasFlags(
+      urlRecord, nsIProtocolHandler::URI_OPENING_EXECUTES_SCRIPT, &isjs);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  if (isjs) {
+    return;
+  }
+
+  RefreshURI(urlRecord, principal, milliSeconds.value());
+}
+
+static void DoCancelRefreshURITimers(nsIMutableArray* aTimerList) {
+  if (!aTimerList) {
+    return;
+  }
+
+  uint32_t n = 0;
+  aTimerList->GetLength(&n);
+
+  while (n) {
+    nsCOMPtr<nsITimer> timer(do_QueryElementAt(aTimerList, --n));
+
+    aTimerList->RemoveElementAt(n);  // bye bye owning timer ref
+
+    if (timer) {
+      timer->Cancel();
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::CancelRefreshURITimers() {
+  DoCancelRefreshURITimers(mRefreshURIList);
+  DoCancelRefreshURITimers(mSavedRefreshURIList);
+  DoCancelRefreshURITimers(mBFCachedRefreshURIList);
+  mRefreshURIList = nullptr;
+  mSavedRefreshURIList = nullptr;
+  mBFCachedRefreshURIList = nullptr;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetRefreshPending(bool* aResult) {
+  if (!mRefreshURIList) {
+    *aResult = false;
+    return NS_OK;
+  }
+
+  uint32_t count;
+  nsresult rv = mRefreshURIList->GetLength(&count);
+  if (NS_SUCCEEDED(rv)) {
+    *aResult = (count != 0);
+  }
+  return rv;
+}
+
+void nsDocShell::RefreshURIToQueue() {
+  if (mRefreshURIList) {
+    uint32_t n = 0;
+    mRefreshURIList->GetLength(&n);
+
+    for (uint32_t i = 0; i < n; ++i) {
+      nsCOMPtr<nsITimer> timer = do_QueryElementAt(mRefreshURIList, i);
+      if (!timer) {
+        continue;  // this must be a nsRefreshURI already
+      }
+
+      // Replace this timer object with a nsRefreshTimer object.
+      nsCOMPtr<nsITimerCallback> callback;
+      timer->GetCallback(getter_AddRefs(callback));
+
+      timer->Cancel();
+
+      mRefreshURIList->ReplaceElementAt(callback, i);
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::SuspendRefreshURIs() {
+  RefreshURIToQueue();
+
+  // Suspend refresh URIs for our child shells as well.
+  for (auto* child : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> shell = do_QueryObject(child);
+    if (shell) {
+      shell->SuspendRefreshURIs();
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::ResumeRefreshURIs() {
+  RefreshURIFromQueue();
+
+  // Resume refresh URIs for our child shells as well.
+  for (auto* child : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> shell = do_QueryObject(child);
+    if (shell) {
+      shell->ResumeRefreshURIs();
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::RefreshURIFromQueue() {
+  if (!mRefreshURIList) {
+    return NS_OK;
+  }
+  uint32_t n = 0;
+  mRefreshURIList->GetLength(&n);
+
+  while (n) {
+    nsCOMPtr<nsITimerCallback> refreshInfo =
+        do_QueryElementAt(mRefreshURIList, --n);
+
+    if (refreshInfo) {
+      // This is the nsRefreshTimer object, waiting to be
+      // setup in a timer object and fired.
+      // Create the timer and  trigger it.
+      uint32_t delay = static_cast<nsRefreshTimer*>(
+                           static_cast<nsITimerCallback*>(refreshInfo))
+                           ->GetDelay();
+      nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
+      if (win) {
+        nsCOMPtr<nsITimer> timer;
+        NS_NewTimerWithCallback(getter_AddRefs(timer), refreshInfo, delay,
+                                nsITimer::TYPE_ONE_SHOT);
+
+        if (timer) {
+          // Replace the nsRefreshTimer element in the queue with
+          // its corresponding timer object, so that in case another
+          // load comes through before the timer can go off, the timer will
+          // get cancelled in CancelRefreshURITimer()
+          mRefreshURIList->ReplaceElementAt(timer, n);
+        }
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+static bool IsFollowupPartOfMultipart(nsIRequest* aRequest) {
+  nsCOMPtr<nsIMultiPartChannel> multiPartChannel = do_QueryInterface(aRequest);
+  bool firstPart = false;
+  return multiPartChannel &&
+         NS_SUCCEEDED(multiPartChannel->GetIsFirstPart(&firstPart)) &&
+         !firstPart;
+}
+
+nsresult nsDocShell::Embed(nsIDocumentViewer* aDocumentViewer,
+                           WindowGlobalChild* aWindowActor,
+                           bool aIsTransientAboutBlank, bool aPersist,
+                           nsIRequest* aRequest, nsIURI* aPreviousURI) {
+  // Save the LayoutHistoryState of the previous document, before
+  // setting up new document
+  PersistLayoutHistoryState();
+
+  nsresult rv = SetupNewViewer(aDocumentViewer, aWindowActor);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // XXX What if SetupNewViewer fails?
+  if (mozilla::SessionHistoryInParent() ? !!mLoadingEntry : !!mLSHE) {
+    // Set history.state
+    SetDocCurrentStateObj(mLSHE,
+                          mLoadingEntry ? &mLoadingEntry->mInfo : nullptr);
+  }
+
+  if (mLSHE) {
+    // Restore the editing state, if it's stored in session history.
+    if (mLSHE->HasDetachedEditor()) {
+      ReattachEditorToWindow(mLSHE);
+    }
+
+    SetHistoryEntryAndUpdateBC(Nothing(), Some<nsISHEntry*>(mLSHE));
+  }
+
+  if (!aIsTransientAboutBlank && mozilla::SessionHistoryInParent() &&
+      !IsFollowupPartOfMultipart(aRequest)) {
+    bool expired = false;
+    uint32_t cacheKey = 0;
+    nsCOMPtr<nsICacheInfoChannel> cacheChannel = do_QueryInterface(aRequest);
+    if (cacheChannel) {
+      // Check if the page has expired from cache
+      uint32_t expTime = 0;
+      cacheChannel->GetCacheTokenExpirationTime(&expTime);
+      uint32_t now = PRTimeToSeconds(PR_Now());
+      if (expTime <= now) {
+        expired = true;
+      }
+
+      // The checks for updating cache key are similar to the old session
+      // history in OnNewURI. Try to update the cache key if
+      //  - we should update session history and aren't doing a session
+      //    history load.
+      //  - we're doing a forced reload.
+      if (((!mLoadingEntry || !mLoadingEntry->mLoadIsFromSessionHistory) &&
+           mBrowsingContext->ShouldUpdateSessionHistory(mLoadType)) ||
+          IsForceReloadType(mLoadType)) {
+        cacheChannel->GetCacheKey(&cacheKey);
+      }
+    }
+
+    MOZ_LOG(gSHLog, LogLevel::Debug, ("document %p Embed", this));
+    MoveLoadingToActiveEntry(aPersist, expired, cacheKey, aPreviousURI);
+  }
+
+  bool updateHistory = true;
+
+  // Determine if this type of load should update history
+  switch (mLoadType) {
+    case LOAD_NORMAL_REPLACE:
+    case LOAD_REFRESH_REPLACE:
+    case LOAD_STOP_CONTENT_AND_REPLACE:
+    case LOAD_RELOAD_BYPASS_CACHE:
+    case LOAD_RELOAD_BYPASS_PROXY:
+    case LOAD_RELOAD_BYPASS_PROXY_AND_CACHE:
+    case LOAD_REPLACE_BYPASS_CACHE:
+      updateHistory = false;
+      break;
+    default:
+      break;
+  }
+
+  if (!updateHistory) {
+    SetLayoutHistoryState(nullptr);
+  }
+
+  return NS_OK;
+}
+
+//*****************************************************************************
+// nsDocShell::nsIWebProgressListener
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::OnProgressChange(nsIWebProgress* aProgress, nsIRequest* aRequest,
+                             int32_t aCurSelfProgress, int32_t aMaxSelfProgress,
+                             int32_t aCurTotalProgress,
+                             int32_t aMaxTotalProgress) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::OnStateChange(nsIWebProgress* aProgress, nsIRequest* aRequest,
+                          uint32_t aStateFlags, nsresult aStatus) {
+  if ((~aStateFlags & (STATE_START | STATE_IS_NETWORK)) == 0) {
+    // Save timing statistics.
+    nsCOMPtr<nsIChannel> channel(do_QueryInterface(aRequest));
+    nsCOMPtr<nsIURI> uri;
+    channel->GetURI(getter_AddRefs(uri));
+    nsAutoCString aURI;
+    uri->GetAsciiSpec(aURI);
+
+    if (this == aProgress) {
+      mozilla::Unused << MaybeInitTiming();
+      mTiming->NotifyFetchStart(uri,
+                                ConvertLoadTypeToNavigationType(mLoadType));
+      // If we are starting a DocumentChannel, we need to pass the timing
+      // statistics so that should a process switch occur, the starting type can
+      // be passed to the new DocShell running in the other content process.
+      if (RefPtr<DocumentChannel> docChannel = do_QueryObject(aRequest)) {
+        docChannel->SetNavigationTiming(mTiming);
+      }
+    }
+
+    // Page has begun to load
+    mBusyFlags = (BusyFlags)(BUSY_FLAGS_BUSY | BUSY_FLAGS_BEFORE_PAGE_LOAD);
+
+    if ((aStateFlags & STATE_RESTORING) == 0) {
+      if (StaticPrefs::browser_sessionstore_platform_collection_AtStartup()) {
+        if (IsForceReloadType(mLoadType)) {
+          if (WindowContext* windowContext =
+                  mBrowsingContext->GetCurrentWindowContext()) {
+            SessionStoreChild::From(windowContext->GetWindowGlobalChild())
+                ->ResetSessionStore(mBrowsingContext,
+                                    mBrowsingContext->GetSessionStoreEpoch());
+          }
+        }
+      }
+    }
+  } else if ((~aStateFlags & (STATE_TRANSFERRING | STATE_IS_DOCUMENT)) == 0) {
+    // Page is loading
+    mBusyFlags = (BusyFlags)(BUSY_FLAGS_BUSY | BUSY_FLAGS_PAGE_LOADING);
+  } else if ((aStateFlags & STATE_STOP) && (aStateFlags & STATE_IS_NETWORK)) {
+    // Page has finished loading
+    mBusyFlags = BUSY_FLAGS_NONE;
+  }
+
+  if ((~aStateFlags & (STATE_IS_DOCUMENT | STATE_STOP)) == 0) {
+    nsCOMPtr<nsIWebProgress> webProgress =
+        do_QueryInterface(GetAsSupports(this));
+    // Is the document stop notification for this document?
+    if (aProgress == webProgress.get()) {
+      nsCOMPtr<nsIChannel> channel(do_QueryInterface(aRequest));
+      EndPageLoad(aProgress, channel, aStatus);
+    }
+  }
+  // note that redirect state changes will go through here as well, but it
+  // is better to handle those in OnRedirectStateChange where more
+  // information is available.
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::OnLocationChange(nsIWebProgress* aProgress, nsIRequest* aRequest,
+                             nsIURI* aURI, uint32_t aFlags) {
+  // Since we've now changed Documents, notify the BrowsingContext that we've
+  // changed. Ideally we'd just let the BrowsingContext do this when it
+  // changes the current window global, but that happens before this and we
+  // have a lot of tests that depend on the specific ordering of messages.
+  bool isTopLevel = false;
+  if (XRE_IsParentProcess() &&
+      !(aFlags & nsIWebProgressListener::LOCATION_CHANGE_SAME_DOCUMENT) &&
+      NS_SUCCEEDED(aProgress->GetIsTopLevel(&isTopLevel)) && isTopLevel) {
+    GetBrowsingContext()->Canonical()->UpdateSecurityState();
+  }
+  return NS_OK;
+}
+
+void nsDocShell::OnRedirectStateChange(nsIChannel* aOldChannel,
+                                       nsIChannel* aNewChannel,
+                                       uint32_t aRedirectFlags,
+                                       uint32_t aStateFlags) {
+  NS_ASSERTION(aStateFlags & STATE_REDIRECTING,
+               "Calling OnRedirectStateChange when there is no redirect");
+
+  if (!(aStateFlags & STATE_IS_DOCUMENT)) {
+    return;  // not a toplevel document
+  }
+
+  nsCOMPtr<nsIURI> oldURI, newURI;
+  aOldChannel->GetURI(getter_AddRefs(oldURI));
+  aNewChannel->GetURI(getter_AddRefs(newURI));
+  if (!oldURI || !newURI) {
+    return;
+  }
+
+  // DocumentChannel adds redirect chain to global history in the parent
+  // process. The redirect chain can't be queried from the content process, so
+  // there's no need to update global history here.
+  RefPtr<DocumentChannel> docChannel = do_QueryObject(aOldChannel);
+  if (!docChannel) {
+    // Below a URI visit is saved (see AddURIVisit method doc).
+    // The visit chain looks something like:
+    //   ...
+    //   Site N - 1
+    //                =>  Site N
+    //   (redirect to =>) Site N + 1 (we are here!)
+
+    // Get N - 1 and transition type
+    nsCOMPtr<nsIURI> previousURI;
+    uint32_t previousFlags = 0;
+    ExtractLastVisit(aOldChannel, getter_AddRefs(previousURI), &previousFlags);
+
+    if (aRedirectFlags & nsIChannelEventSink::REDIRECT_INTERNAL ||
+        net::ChannelIsPost(aOldChannel)) {
+      // 1. Internal redirects are ignored because they are specific to the
+      //    channel implementation.
+      // 2. POSTs are not saved by global history.
+      //
+      // Regardless, we need to propagate the previous visit to the new
+      // channel.
+      SaveLastVisit(aNewChannel, previousURI, previousFlags);
+    } else {
+      // Get the HTTP response code, if available.
+      uint32_t responseStatus = 0;
+      nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aOldChannel);
+      if (httpChannel) {
+        Unused << httpChannel->GetResponseStatus(&responseStatus);
+      }
+
+      // Add visit N -1 => N
+      AddURIVisit(oldURI, previousURI, previousFlags, responseStatus);
+
+      // Since N + 1 could be the final destination, we will not save N => N + 1
+      // here.  OnNewURI will do that, so we will cache it.
+      SaveLastVisit(aNewChannel, oldURI, aRedirectFlags);
+    }
+  }
+
+  if (!(aRedirectFlags & nsIChannelEventSink::REDIRECT_INTERNAL) &&
+      mLoadType & (LOAD_CMD_RELOAD | LOAD_CMD_HISTORY)) {
+    mLoadType = LOAD_NORMAL_REPLACE;
+    SetHistoryEntryAndUpdateBC(Some(nullptr), Nothing());
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::OnStatusChange(nsIWebProgress* aWebProgress, nsIRequest* aRequest,
+                           nsresult aStatus, const char16_t* aMessage) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::OnSecurityChange(nsIWebProgress* aWebProgress, nsIRequest* aRequest,
+                             uint32_t aState) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                   nsIRequest* aRequest, uint32_t aEvent) {
+  MOZ_ASSERT_UNREACHABLE("notification excluded in AddProgressListener(...)");
+  return NS_OK;
+}
+
+already_AddRefed<nsIURIFixupInfo> nsDocShell::KeywordToURI(
+    const nsACString& aKeyword, bool aIsPrivateContext) {
+  nsCOMPtr<nsIURIFixupInfo> info;
+  if (!XRE_IsContentProcess()) {
+    nsCOMPtr<nsIURIFixup> uriFixup = components::URIFixup::Service();
+    if (uriFixup) {
+      uriFixup->KeywordToURI(aKeyword, aIsPrivateContext, getter_AddRefs(info));
+    }
+  }
+  return info.forget();
+}
+
+/* static */
+already_AddRefed<nsIURI> nsDocShell::MaybeFixBadCertDomainErrorURI(
+    nsIChannel* aChannel, nsIURI* aUrl) {
+  if (!aChannel) {
+    return nullptr;
+  }
+
+  nsresult rv = NS_OK;
+  nsAutoCString host;
+  rv = aUrl->GetAsciiHost(host);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // No point in going further if "www." is included in the hostname
+  // already. That is the only hueristic we're applying in this function.
+  if (StringBeginsWith(host, "www."_ns)) {
+    return nullptr;
+  }
+
+  // Return if fixup enable pref is turned off.
+  if (!mozilla::StaticPrefs::security_bad_cert_domain_error_url_fix_enabled()) {
+    return nullptr;
+  }
+
+  // Return if scheme is not HTTPS.
+  if (!SchemeIsHTTPS(aUrl)) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsILoadInfo> info = aChannel->LoadInfo();
+  if (!info) {
+    return nullptr;
+  }
+
+  // Skip doing the fixup if our channel was redirected, because we
+  // shouldn't be guessing things about the post-redirect URI.
+  if (!info->RedirectChain().IsEmpty()) {
+    return nullptr;
+  }
+
+  int32_t port = 0;
+  rv = aUrl->GetPort(&port);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // Don't fix up hosts with ports.
+  if (port != -1) {
+    return nullptr;
+  }
+
+  // Don't fix up localhost url.
+  if (host == "localhost") {
+    return nullptr;
+  }
+
+  // Don't fix up hostnames with IP address.
+  if (net_IsValidIPv4Addr(host) || net_IsValidIPv6Addr(host)) {
+    return nullptr;
+  }
+
+  nsAutoCString userPass;
+  rv = aUrl->GetUserPass(userPass);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  // Security - URLs with user / password info should NOT be modified.
+  if (!userPass.IsEmpty()) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsITransportSecurityInfo> tsi;
+  rv = aChannel->GetSecurityInfo(getter_AddRefs(tsi));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  if (NS_WARN_IF(!tsi)) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIX509Cert> cert;
+  rv = tsi->GetServerCert(getter_AddRefs(cert));
+  if (NS_WARN_IF(NS_FAILED(rv) || !cert)) {
+    return nullptr;
+  }
+
+  nsTArray<uint8_t> certBytes;
+  rv = cert->GetRawDER(certBytes);
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  mozilla::pkix::Input serverCertInput;
+  mozilla::pkix::Result rv1 =
+      serverCertInput.Init(certBytes.Elements(), certBytes.Length());
+  if (rv1 != mozilla::pkix::Success) {
+    return nullptr;
+  }
+
+  nsAutoCString newHost("www."_ns);
+  newHost.Append(host);
+
+  mozilla::pkix::Input newHostInput;
+  rv1 = newHostInput.Init(
+      BitwiseCast<const uint8_t*, const char*>(newHost.BeginReading()),
+      newHost.Length());
+  if (rv1 != mozilla::pkix::Success) {
+    return nullptr;
+  }
+
+  // Check if adding a "www." prefix to the request's hostname will
+  // cause the response's certificate to match.
+  rv1 = mozilla::pkix::CheckCertHostname(serverCertInput, newHostInput);
+  if (rv1 != mozilla::pkix::Success) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIURI> newURI;
+  Unused << NS_MutateURI(aUrl).SetHost(newHost).Finalize(
+      getter_AddRefs(newURI));
+
+  return newURI.forget();
+}
+
+/* static */
+already_AddRefed<nsIURI> nsDocShell::AttemptURIFixup(
+    nsIChannel* aChannel, nsresult aStatus,
+    const mozilla::Maybe<nsCString>& aOriginalURIString, uint32_t aLoadType,
+    bool aIsTopFrame, bool aAllowKeywordFixup, bool aUsePrivateBrowsing,
+    bool aNotifyKeywordSearchLoading, nsIInputStream** aNewPostData,
+    bool* outWasSchemelessInput) {
+  if (aStatus != NS_ERROR_UNKNOWN_HOST && aStatus != NS_ERROR_NET_RESET &&
+      aStatus != NS_ERROR_CONNECTION_REFUSED &&
+      aStatus !=
+          mozilla::psm::GetXPCOMFromNSSError(SSL_ERROR_BAD_CERT_DOMAIN)) {
+    return nullptr;
+  }
+
+  if (!(aLoadType == LOAD_NORMAL && aIsTopFrame) && !aAllowKeywordFixup) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIURI> url;
+  nsresult rv = aChannel->GetURI(getter_AddRefs(url));
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  //
+  // Try and make an alternative URI from the old one
+  //
+  nsCOMPtr<nsIURI> newURI;
+  nsCOMPtr<nsIInputStream> newPostData;
+
+  nsAutoCString oldSpec;
+  url->GetSpec(oldSpec);
+
+  //
+  // First try keyword fixup
+  //
+  nsAutoString keywordProviderName, keywordAsSent;
+  if (aStatus == NS_ERROR_UNKNOWN_HOST && aAllowKeywordFixup) {
+    // we should only perform a keyword search under the following
+    // conditions:
+    // (0) Pref keyword.enabled is true
+    // (1) the url scheme is http (or https)
+    // (2) the url does not have a protocol scheme
+    // If we don't enforce such a policy, then we end up doing
+    // keyword searchs on urls we don't intend like imap, file,
+    // mailbox, etc. This could lead to a security problem where we
+    // send data to the keyword server that we shouldn't be.
+    // Someone needs to clean up keywords in general so we can
+    // determine on a per url basis if we want keywords
+    // enabled...this is just a bandaid...
+    nsAutoCString scheme;
+    Unused << url->GetScheme(scheme);
+    if (Preferences::GetBool("keyword.enabled", false) &&
+        StringBeginsWith(scheme, "http"_ns)) {
+      bool attemptFixup = false;
+      nsAutoCString host;
+      Unused << url->GetHost(host);
+      if (host.FindChar('.') == kNotFound) {
+        attemptFixup = true;
+      } else {
+        // For domains with dots, we check the public suffix validity.
+        nsCOMPtr<nsIEffectiveTLDService> tldService =
+            do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
+        if (tldService) {
+          nsAutoCString suffix;
+          attemptFixup =
+              NS_SUCCEEDED(tldService->GetKnownPublicSuffix(url, suffix)) &&
+              suffix.IsEmpty();
+        }
+      }
+      if (attemptFixup) {
+        nsCOMPtr<nsIURIFixupInfo> info;
+        // only send non-qualified hosts to the keyword server
+        if (aOriginalURIString && !aOriginalURIString->IsEmpty()) {
+          info = KeywordToURI(*aOriginalURIString, aUsePrivateBrowsing);
+        } else {
+          //
+          // If this string was passed through nsStandardURL by
+          // chance, then it may have been converted from UTF-8 to
+          // ACE, which would result in a completely bogus keyword
+          // query.  Here we try to recover the original Unicode
+          // value, but this is not 100% correct since the value may
+          // have been normalized per the IDN normalization rules.
+          //
+          // Since we don't have access to the exact original string
+          // that was entered by the user, this will just have to do.
+          bool isACE;
+          nsAutoCString utf8Host;
+          nsCOMPtr<nsIIDNService> idnSrv =
+              do_GetService(NS_IDNSERVICE_CONTRACTID);
+          if (idnSrv && NS_SUCCEEDED(idnSrv->IsACE(host, &isACE)) && isACE &&
+              NS_SUCCEEDED(idnSrv->ConvertACEtoUTF8(host, utf8Host))) {
+            info = KeywordToURI(utf8Host, aUsePrivateBrowsing);
+
+          } else {
+            info = KeywordToURI(host, aUsePrivateBrowsing);
+          }
+        }
+        if (info) {
+          info->GetPreferredURI(getter_AddRefs(newURI));
+          info->GetWasSchemelessInput(outWasSchemelessInput);
+          if (newURI) {
+            info->GetKeywordAsSent(keywordAsSent);
+            info->GetKeywordProviderName(keywordProviderName);
+            info->GetPostData(getter_AddRefs(newPostData));
+          }
+        }
+      }
+    }
+  }
+
+  //
+  // Now try change the address, e.g. turn http://foo into
+  // http://www.foo.com, and if that doesn't work try https with
+  // https://foo and https://www.foo.com.
+  //
+  if (aStatus == NS_ERROR_UNKNOWN_HOST || aStatus == NS_ERROR_NET_RESET) {
+    // Skip fixup for anything except a normal document load
+    // operation on the topframe.
+    bool doCreateAlternate = aLoadType == LOAD_NORMAL && aIsTopFrame;
+
+    if (doCreateAlternate) {
+      nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
+      nsIPrincipal* principal = loadInfo->TriggeringPrincipal();
+      // Only do this if our channel was loaded directly by the user from the
+      // URL bar or similar (system principal) and not redirected, because we
+      // shouldn't be guessing things about links from other sites, or a
+      // post-redirect URI.
+      doCreateAlternate = principal && principal->IsSystemPrincipal() &&
+                          loadInfo->RedirectChain().IsEmpty();
+    }
+    // Test if keyword lookup produced a new URI or not
+    if (doCreateAlternate && newURI) {
+      bool sameURI = false;
+      url->Equals(newURI, &sameURI);
+      if (!sameURI) {
+        // Keyword lookup made a new URI so no need to try
+        // an alternate one.
+        doCreateAlternate = false;
+      }
+    }
+    if (doCreateAlternate) {
+      newURI = nullptr;
+      newPostData = nullptr;
+      keywordProviderName.Truncate();
+      keywordAsSent.Truncate();
+      nsCOMPtr<nsIURIFixup> uriFixup = components::URIFixup::Service();
+      if (uriFixup) {
+        nsCOMPtr<nsIURIFixupInfo> fixupInfo;
+        uriFixup->GetFixupURIInfo(oldSpec, nsIURIFixup::FIXUP_FLAG_NONE,
+                                  getter_AddRefs(fixupInfo));
+        if (fixupInfo) {
+          fixupInfo->GetPreferredURI(getter_AddRefs(newURI));
+        }
+      }
+    }
+  } else if (aStatus == NS_ERROR_CONNECTION_REFUSED &&
+             Preferences::GetBool("browser.fixup.fallback-to-https", false)) {
+    // Try HTTPS, since http didn't work
+    if (SchemeIsHTTP(url)) {
+      int32_t port = 0;
+      url->GetPort(&port);
+
+      // Fall back to HTTPS only if port is default
+      if (port == -1) {
+        newURI = nullptr;
+        newPostData = nullptr;
+        Unused << NS_MutateURI(url)
+                      .SetScheme("https"_ns)
+                      .Finalize(getter_AddRefs(newURI));
+      }
+    }
+  }
+
+  // If we have a SSL_ERROR_BAD_CERT_DOMAIN error, try prefixing the domain name
+  // with www. to see if we can avoid showing the cert error page. For example,
+  // https://example.com -> https://www.example.com.
+  if (aStatus ==
+      mozilla::psm::GetXPCOMFromNSSError(SSL_ERROR_BAD_CERT_DOMAIN)) {
+    newPostData = nullptr;
+    newURI = MaybeFixBadCertDomainErrorURI(aChannel, url);
+  }
+
+  // Did we make a new URI that is different to the old one? If so
+  // load it.
+  //
+  if (newURI) {
+    // Make sure the new URI is different from the old one,
+    // otherwise there's little point trying to load it again.
+    bool sameURI = false;
+    url->Equals(newURI, &sameURI);
+    if (!sameURI) {
+      if (aNewPostData) {
+        newPostData.forget(aNewPostData);
+      }
+      if (aNotifyKeywordSearchLoading) {
+        // This notification is meant for Firefox Health Report so it
+        // can increment counts from the search engine
+        MaybeNotifyKeywordSearchLoading(keywordProviderName, keywordAsSent);
+      }
+      return newURI.forget();
+    }
+  }
+
+  return nullptr;
+}
+
+nsresult nsDocShell::FilterStatusForErrorPage(
+    nsresult aStatus, nsIChannel* aChannel, uint32_t aLoadType,
+    bool aIsTopFrame, bool aUseErrorPages, bool aIsInitialDocument,
+    bool* aSkippedUnknownProtocolNavigation) {
+  // Errors to be shown only on top-level frames
+  if ((aStatus == NS_ERROR_UNKNOWN_HOST ||
+       aStatus == NS_ERROR_CONNECTION_REFUSED ||
+       aStatus == NS_ERROR_UNKNOWN_PROXY_HOST ||
+       aStatus == NS_ERROR_PROXY_CONNECTION_REFUSED ||
+       aStatus == NS_ERROR_PROXY_FORBIDDEN ||
+       aStatus == NS_ERROR_PROXY_NOT_IMPLEMENTED ||
+       aStatus == NS_ERROR_PROXY_AUTHENTICATION_FAILED ||
+       aStatus == NS_ERROR_PROXY_TOO_MANY_REQUESTS ||
+       aStatus == NS_ERROR_MALFORMED_URI ||
+       aStatus == NS_ERROR_BLOCKED_BY_POLICY ||
+       aStatus == NS_ERROR_DOM_COOP_FAILED ||
+       aStatus == NS_ERROR_DOM_COEP_FAILED) &&
+      (aIsTopFrame || aUseErrorPages)) {
+    return aStatus;
+  }
+
+  if (aStatus == NS_ERROR_NET_TIMEOUT ||
+      aStatus == NS_ERROR_NET_TIMEOUT_EXTERNAL ||
+      aStatus == NS_ERROR_PROXY_GATEWAY_TIMEOUT ||
+      aStatus == NS_ERROR_REDIRECT_LOOP ||
+      aStatus == NS_ERROR_UNKNOWN_SOCKET_TYPE ||
+      aStatus == NS_ERROR_NET_INTERRUPT || aStatus == NS_ERROR_NET_RESET ||
+      aStatus == NS_ERROR_PROXY_BAD_GATEWAY || aStatus == NS_ERROR_OFFLINE ||
+      aStatus == NS_ERROR_MALWARE_URI || aStatus == NS_ERROR_PHISHING_URI ||
+      aStatus == NS_ERROR_UNWANTED_URI || aStatus == NS_ERROR_HARMFUL_URI ||
+      aStatus == NS_ERROR_UNSAFE_CONTENT_TYPE ||
+      aStatus == NS_ERROR_INTERCEPTION_FAILED ||
+      aStatus == NS_ERROR_NET_INADEQUATE_SECURITY ||
+      aStatus == NS_ERROR_NET_HTTP2_SENT_GOAWAY ||
+      aStatus == NS_ERROR_NET_HTTP3_PROTOCOL_ERROR ||
+      aStatus == NS_ERROR_DOM_BAD_URI || aStatus == NS_ERROR_FILE_NOT_FOUND ||
+      aStatus == NS_ERROR_FILE_ACCESS_DENIED ||
+      aStatus == NS_ERROR_CORRUPTED_CONTENT ||
+      aStatus == NS_ERROR_INVALID_CONTENT_ENCODING ||
+      NS_ERROR_GET_MODULE(aStatus) == NS_ERROR_MODULE_SECURITY) {
+    // Errors to be shown for any frame
+    return aStatus;
+  }
+
+  if (aStatus == NS_ERROR_UNKNOWN_PROTOCOL) {
+    // For unknown protocols we only display an error if the load is triggered
+    // by the browser itself, or we're replacing the initial document (and
+    // nothing else). Showing the error for page-triggered navigations causes
+    // annoying behavior for users, see bug 1528305.
+    //
+    // We could, maybe, try to detect if this is in response to some user
+    // interaction (like clicking a link, or something else) and maybe show
+    // the error page in that case. But this allows for ctrl+clicking and such
+    // to see the error page.
+    nsCOMPtr<nsILoadInfo> info = aChannel->LoadInfo();
+    if (!info->TriggeringPrincipal()->IsSystemPrincipal() &&
+        StaticPrefs::dom_no_unknown_protocol_error_enabled() &&
+        !aIsInitialDocument) {
+      if (aSkippedUnknownProtocolNavigation) {
+        *aSkippedUnknownProtocolNavigation = true;
+      }
+      return NS_OK;
+    }
+    return aStatus;
+  }
+
+  if (aStatus == NS_ERROR_DOCUMENT_NOT_CACHED) {
+    // Non-caching channels will simply return NS_ERROR_OFFLINE.
+    // Caching channels would have to look at their flags to work
+    // out which error to return. Or we can fix up the error here.
+    if (!(aLoadType & LOAD_CMD_HISTORY)) {
+      return NS_ERROR_OFFLINE;
+    }
+    return aStatus;
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::EndPageLoad(nsIWebProgress* aProgress,
+                                 nsIChannel* aChannel, nsresult aStatus) {
+  MOZ_LOG(gDocShellLeakLog, LogLevel::Debug,
+          ("DOCSHELL %p EndPageLoad status: %" PRIx32 "\n", this,
+           static_cast<uint32_t>(aStatus)));
+  if (!aChannel) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  // Make sure to discard the initial client if we never created the initial
+  // about:blank document.  Do this before possibly returning from the method
+  // due to an error.
+  mInitialClientSource.reset();
+
+  nsCOMPtr<nsIConsoleReportCollector> reporter = do_QueryInterface(aChannel);
+  if (reporter) {
+    nsCOMPtr<nsILoadGroup> loadGroup;
+    aChannel->GetLoadGroup(getter_AddRefs(loadGroup));
+    if (loadGroup) {
+      reporter->FlushConsoleReports(loadGroup);
+    } else {
+      reporter->FlushConsoleReports(GetDocument());
+    }
+  }
+
+  nsCOMPtr<nsIURI> url;
+  nsresult rv = aChannel->GetURI(getter_AddRefs(url));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  nsCOMPtr<nsITimedChannel> timingChannel = do_QueryInterface(aChannel);
+  if (timingChannel) {
+    TimeStamp channelCreationTime;
+    rv = timingChannel->GetChannelCreation(&channelCreationTime);
+    if (NS_SUCCEEDED(rv) && !channelCreationTime.IsNull()) {
+      glean::performance_page::total_content_page_load.AccumulateRawDuration(
+          TimeStamp::Now() - channelCreationTime);
+    }
+  }
+
+  // Timing is picked up by the window, we don't need it anymore
+  mTiming = nullptr;
+
+  // clean up reload state for meta charset
+  if (eCharsetReloadRequested == mCharsetReloadState) {
+    mCharsetReloadState = eCharsetReloadStopOrigional;
+  } else {
+    mCharsetReloadState = eCharsetReloadInit;
+  }
+
+  // Save a pointer to the currently-loading history entry.
+  // nsDocShell::EndPageLoad will clear mLSHE, but we may need this history
+  // entry further down in this method.
+  nsCOMPtr<nsISHEntry> loadingSHE = mLSHE;
+  mozilla::Unused << loadingSHE;  // XXX: Not sure if we need this anymore
+
+  //
+  // one of many safeguards that prevent death and destruction if
+  // someone is so very very rude as to bring this window down
+  // during this load handler.
+  //
+  nsCOMPtr<nsIDocShell> kungFuDeathGrip(this);
+
+  // Notify the DocumentViewer that the Document has finished loading.  This
+  // will cause any OnLoad(...) and PopState(...) handlers to fire.
+  if (!mEODForCurrentDocument && mDocumentViewer) {
+    mIsExecutingOnLoadHandler = true;
+    nsCOMPtr<nsIDocumentViewer> viewer = mDocumentViewer;
+    viewer->LoadComplete(aStatus);
+    mIsExecutingOnLoadHandler = false;
+
+    mEODForCurrentDocument = true;
+  }
+  /* Check if the httpChannel has any cache-control related response headers,
+   * like no-store, no-cache. If so, update SHEntry so that
+   * when a user goes back/forward to this page, we appropriately do
+   * form value restoration or load from server.
+   */
+  nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(aChannel));
+  if (!httpChannel) {
+    // HttpChannel could be hiding underneath a Multipart channel.
+    GetHttpChannel(aChannel, getter_AddRefs(httpChannel));
+  }
+
+  if (httpChannel) {
+    // figure out if SH should be saving layout state.
+    bool discardLayoutState = ShouldDiscardLayoutState(httpChannel);
+    if (mLSHE && discardLayoutState && (mLoadType & LOAD_CMD_NORMAL) &&
+        (mLoadType != LOAD_BYPASS_HISTORY) && (mLoadType != LOAD_ERROR_PAGE)) {
+      mLSHE->SetSaveLayoutStateFlag(false);
+    }
+  }
+
+  // Clear mLSHE after calling the onLoadHandlers. This way, if the
+  // onLoadHandler tries to load something different in
+  // itself or one of its children, we can deal with it appropriately.
+  if (mLSHE) {
+    mLSHE->SetLoadType(LOAD_HISTORY);
+
+    // Clear the mLSHE reference to indicate document loading is done one
+    // way or another.
+    SetHistoryEntryAndUpdateBC(Some(nullptr), Nothing());
+  }
+  mActiveEntryIsLoadingFromSessionHistory = false;
+
+  // if there's a refresh header in the channel, this method
+  // will set it up for us.
+  if (mBrowsingContext->IsActive() || !mDisableMetaRefreshWhenInactive)
+    RefreshURIFromQueue();
+
+  // Test whether this is the top frame or a subframe
+  bool isTopFrame = mBrowsingContext->IsTop();
+
+  bool hadErrorStatus = false;
+  // If status code indicates an error it means that DocumentChannel already
+  // tried to fixup the uri and failed. Throw an error dialog box here.
+  if (NS_FAILED(aStatus)) {
+    // If we got CONTENT_BLOCKED from EndPageLoad, then we need to fire
+    // the error event to our embedder, since tests are relying on this.
+    // The error event is usually fired by the caller of InternalLoad, but
+    // this particular error can happen asynchronously.
+    // Bug 1629201 is filed for having much clearer decision making around
+    // which cases need error events.
+    bool fireFrameErrorEvent = (aStatus == NS_ERROR_CONTENT_BLOCKED_SHOW_ALT ||
+                                aStatus == NS_ERROR_CONTENT_BLOCKED);
+    UnblockEmbedderLoadEventForFailure(fireFrameErrorEvent);
+
+    bool isInitialDocument =
+        !GetExtantDocument() || GetExtantDocument()->IsInitialDocument();
+    bool skippedUnknownProtocolNavigation = false;
+    aStatus = FilterStatusForErrorPage(aStatus, aChannel, mLoadType, isTopFrame,
+                                       mBrowsingContext->GetUseErrorPages(),
+                                       isInitialDocument,
+                                       &skippedUnknownProtocolNavigation);
+    hadErrorStatus = true;
+    if (NS_FAILED(aStatus)) {
+      if (!mIsBeingDestroyed) {
+        DisplayLoadError(aStatus, url, nullptr, aChannel);
+      }
+    } else if (skippedUnknownProtocolNavigation) {
+      nsTArray<nsString> params;
+      if (NS_FAILED(
+              NS_GetSanitizedURIStringFromURI(url, *params.AppendElement()))) {
+        params.LastElement().AssignLiteral(u"(unknown uri)");
+      }
+      nsContentUtils::ReportToConsole(
+          nsIScriptError::warningFlag, "DOM"_ns, GetExtantDocument(),
+          nsContentUtils::eDOM_PROPERTIES, "UnknownProtocolNavigationPrevented",
+          params);
+    }
+  } else {
+    // If we have a host
+    nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
+    PredictorLearnRedirect(url, aChannel, loadInfo->GetOriginAttributes());
+  }
+
+  if (hadErrorStatus) {
+    // Don't send session store updates if the reason EndPageLoad was called is
+    // because we are process switching. Sometimes the update takes too long and
+    // incorrectly overrides session store data from the following load.
+    return NS_OK;
+  }
+  if (StaticPrefs::browser_sessionstore_platform_collection_AtStartup()) {
+    if (WindowContext* windowContext =
+            mBrowsingContext->GetCurrentWindowContext()) {
+      using Change = SessionStoreChangeListener::Change;
+
+      // We've finished loading the page and now we want to collect all the
+      // session store state that the page is initialized with.
+      SessionStoreChangeListener::CollectSessionStoreData(
+          windowContext,
+          EnumSet<Change>(Change::Input, Change::Scroll, Change::SessionHistory,
+                          Change::WireFrame));
+    }
+  }
+
+  return NS_OK;
+}
+
+//*****************************************************************************
+// nsDocShell: Content Viewer Management
+//*****************************************************************************
+
+nsresult nsDocShell::EnsureDocumentViewer() {
+  if (mDocumentViewer) {
+    return NS_OK;
+  }
+  if (mIsBeingDestroyed) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIContentSecurityPolicy> cspToInheritForAboutBlank;
+  nsCOMPtr<nsIURI> baseURI;
+  nsIPrincipal* principal = GetInheritedPrincipal(false);
+  nsIPrincipal* partitionedPrincipal = GetInheritedPrincipal(false, true);
+
+  nsCOMPtr<nsIDocShellTreeItem> parentItem;
+  GetInProcessSameTypeParent(getter_AddRefs(parentItem));
+  if (parentItem) {
+    if (nsCOMPtr<nsPIDOMWindowOuter> domWin = GetWindow()) {
+      nsCOMPtr<Element> parentElement = domWin->GetFrameElementInternal();
+      if (parentElement) {
+        baseURI = parentElement->GetBaseURI();
+        cspToInheritForAboutBlank = parentElement->GetCsp();
+      }
+    }
+  }
+
+  nsresult rv = CreateAboutBlankDocumentViewer(
+      principal, partitionedPrincipal, cspToInheritForAboutBlank, baseURI,
+      /* aIsInitialDocument */ true);
+
+  NS_ENSURE_STATE(mDocumentViewer);
+
+  if (NS_SUCCEEDED(rv)) {
+    RefPtr<Document> doc(GetDocument());
+    MOZ_ASSERT(doc,
+               "Should have doc if CreateAboutBlankDocumentViewer "
+               "succeeded!");
+    MOZ_ASSERT(doc->IsInitialDocument(), "Document should be initial document");
+
+    // Documents created using EnsureDocumentViewer may be transient
+    // placeholders created by framescripts before content has a
+    // chance to load. In some cases, window.open(..., "noopener")
+    // will create such a document and then synchronously tear it
+    // down, firing a "pagehide" event. Doing so violates our
+    // assertions about DocGroups. It's easier to silence the
+    // assertion here than to avoid creating the extra document.
+    doc->IgnoreDocGroupMismatches();
+  }
+
+  return rv;
+}
+
+nsresult nsDocShell::CreateAboutBlankDocumentViewer(
+    nsIPrincipal* aPrincipal, nsIPrincipal* aPartitionedPrincipal,
+    nsIContentSecurityPolicy* aCSP, nsIURI* aBaseURI, bool aIsInitialDocument,
+    const Maybe<nsILoadInfo::CrossOriginEmbedderPolicy>& aCOEP,
+    bool aTryToSaveOldPresentation, bool aCheckPermitUnload,
+    WindowGlobalChild* aActor) {
+  RefPtr<Document> blankDoc;
+  nsCOMPtr<nsIDocumentViewer> viewer;
+  nsresult rv = NS_ERROR_FAILURE;
+
+  MOZ_ASSERT_IF(aActor, aActor->DocumentPrincipal() == aPrincipal);
+
+  /* mCreatingDocument should never be true at this point. However, it's
+     a theoretical possibility. We want to know about it and make it stop,
+     and this sounds like a job for an assertion. */
+  NS_ASSERTION(!mCreatingDocument,
+               "infinite(?) loop creating document averted");
+  if (mCreatingDocument) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (!mBrowsingContext->AncestorsAreCurrent() ||
+      mBrowsingContext->IsInBFCache()) {
+    mBrowsingContext->RemoveRootFromBFCacheSync();
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // mDocumentViewer->PermitUnload may release |this| docshell.
+  nsCOMPtr<nsIDocShell> kungFuDeathGrip(this);
+
+  AutoRestore<bool> creatingDocument(mCreatingDocument);
+  mCreatingDocument = true;
+
+  if (aPrincipal && !aPrincipal->IsSystemPrincipal() &&
+      mItemType != typeChrome) {
+    MOZ_ASSERT(aPrincipal->OriginAttributesRef() ==
+               mBrowsingContext->OriginAttributesRef());
+  }
+
+  // Make sure timing is created.  But first record whether we had it
+  // already, so we don't clobber the timing for an in-progress load.
+  bool hadTiming = mTiming;
+  bool toBeReset = MaybeInitTiming();
+  if (mDocumentViewer) {
+    if (aCheckPermitUnload) {
+      // We've got a content viewer already. Make sure the user
+      // permits us to discard the current document and replace it
+      // with about:blank. And also ensure we fire the unload events
+      // in the current document.
+
+      // Unload gets fired first for
+      // document loaded from the session history.
+      mTiming->NotifyBeforeUnload();
+
+      bool okToUnload;
+      rv = mDocumentViewer->PermitUnload(&okToUnload);
+
+      if (NS_SUCCEEDED(rv) && !okToUnload) {
+        // The user chose not to unload the page, interrupt the load.
+        MaybeResetInitTiming(toBeReset);
+        return NS_ERROR_FAILURE;
+      }
+      if (mTiming) {
+        mTiming->NotifyUnloadAccepted(mCurrentURI);
+      }
+    }
+
+    mSavingOldViewer =
+        aTryToSaveOldPresentation &&
+        CanSavePresentation(LOAD_NORMAL, nullptr, nullptr,
+                            /* aReportBFCacheComboTelemetry */ true);
+
+    // Make sure to blow away our mLoadingURI just in case.  No loads
+    // from inside this pagehide.
+    mLoadingURI = nullptr;
+
+    // Stop any in-progress loading, so that we don't accidentally trigger any
+    // PageShow notifications from Embed() interrupting our loading below.
+    Stop();
+
+    // Notify the current document that it is about to be unloaded!!
+    //
+    // It is important to fire the unload() notification *before* any state
+    // is changed within the DocShell - otherwise, javascript will get the
+    // wrong information :-(
+    //
+    (void)FirePageHideNotification(!mSavingOldViewer);
+    // pagehide notification might destroy this docshell.
+    if (mIsBeingDestroyed) {
+      return NS_ERROR_DOCSHELL_DYING;
+    }
+  }
+
+  // Now make sure we don't think we're in the middle of firing unload after
+  // this point.  This will make us fire unload when the about:blank document
+  // unloads... but that's ok, more or less.  Would be nice if it fired load
+  // too, of course.
+  mFiredUnloadEvent = false;
+
+  nsCOMPtr<nsIDocumentLoaderFactory> docFactory =
+      nsContentUtils::FindInternalDocumentViewer("text/html"_ns);
+
+  if (docFactory) {
+    nsCOMPtr<nsIPrincipal> principal, partitionedPrincipal;
+    const uint32_t sandboxFlags =
+        mBrowsingContext->GetHasLoadedNonInitialDocument()
+            ? mBrowsingContext->GetSandboxFlags()
+            : mBrowsingContext->GetInitialSandboxFlags();
+    // If we're sandboxed, then create a new null principal. We skip
+    // this if we're being created from WindowGlobalChild, since in
+    // that case we already have a null principal if required.
+    // We can't compare againt the BrowsingContext sandbox flag, since
+    // the value was taken when the load initiated and may have since
+    // changed.
+    if ((sandboxFlags & SANDBOXED_ORIGIN) && !aActor) {
+      if (aPrincipal) {
+        principal = NullPrincipal::CreateWithInheritedAttributes(aPrincipal);
+      } else {
+        principal = NullPrincipal::Create(GetOriginAttributes());
+      }
+      partitionedPrincipal = principal;
+    } else {
+      principal = aPrincipal;
+      partitionedPrincipal = aPartitionedPrincipal;
+    }
+
+    // We cannot get the foreign partitioned prinicpal for the initial
+    // about:blank page. So, we change to check if we need to use the
+    // partitioned principal for the service worker here.
+    MaybeCreateInitialClientSource(
+        StoragePrincipalHelper::ShouldUsePartitionPrincipalForServiceWorker(
+            this)
+            ? partitionedPrincipal
+            : principal);
+
+    // generate (about:blank) document to load
+    blankDoc = nsContentDLF::CreateBlankDocument(mLoadGroup, principal,
+                                                 partitionedPrincipal, this);
+    if (blankDoc) {
+      // Hack: manually set the CSP for the new document
+      // Please create an actual copy of the CSP (do not share the same
+      // reference) otherwise appending a new policy within the new
+      // document will be incorrectly propagated to the opening doc.
+      if (aCSP) {
+        RefPtr<nsCSPContext> cspToInherit = new nsCSPContext();
+        cspToInherit->InitFromOther(static_cast<nsCSPContext*>(aCSP));
+        blankDoc->SetCsp(cspToInherit);
+      }
+
+      blankDoc->SetIsInitialDocument(aIsInitialDocument);
+
+      blankDoc->SetEmbedderPolicy(aCOEP);
+
+      // Hack: set the base URI manually, since this document never
+      // got Reset() with a channel.
+      blankDoc->SetBaseURI(aBaseURI);
+
+      // Copy our sandbox flags to the document. These are immutable
+      // after being set here.
+      blankDoc->SetSandboxFlags(sandboxFlags);
+
+      blankDoc->InitFeaturePolicy();
+
+      // create a content viewer for us and the new document
+      docFactory->CreateInstanceForDocument(
+          NS_ISUPPORTS_CAST(nsIDocShell*, this), blankDoc, "view",
+          getter_AddRefs(viewer));
+
+      // hook 'em up
+      if (viewer) {
+        viewer->SetContainer(this);
+        rv = Embed(viewer, aActor, true, false, nullptr, mCurrentURI);
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        SetCurrentURI(blankDoc->GetDocumentURI(), nullptr,
+                      /* aFireLocationChange */ true,
+                      /* aIsInitialAboutBlank */ true,
+                      /* aLocationFlags */ 0);
+        rv = mIsBeingDestroyed ? NS_ERROR_NOT_AVAILABLE : NS_OK;
+      }
+    }
+  }
+
+  // The transient about:blank viewer doesn't have a session history entry.
+  SetHistoryEntryAndUpdateBC(Nothing(), Some(nullptr));
+
+  // Clear out our mTiming like we would in EndPageLoad, if we didn't
+  // have one before entering this function.
+  if (!hadTiming) {
+    mTiming = nullptr;
+    mBlankTiming = true;
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocShell::CreateAboutBlankDocumentViewer(nsIPrincipal* aPrincipal,
+                                           nsIPrincipal* aPartitionedPrincipal,
+                                           nsIContentSecurityPolicy* aCSP) {
+  return CreateAboutBlankDocumentViewer(aPrincipal, aPartitionedPrincipal, aCSP,
+                                        nullptr,
+                                        /* aIsInitialDocument */ false);
+}
+
+nsresult nsDocShell::CreateDocumentViewerForActor(
+    WindowGlobalChild* aWindowActor) {
+  MOZ_ASSERT(aWindowActor);
+
+  // FIXME: WindowGlobalChild should provide the PartitionedPrincipal.
+  // FIXME: We may want to support non-initial documents here.
+  nsresult rv = CreateAboutBlankDocumentViewer(
+      aWindowActor->DocumentPrincipal(), aWindowActor->DocumentPrincipal(),
+      /* aCsp */ nullptr,
+      /* aBaseURI */ nullptr,
+      /* aIsInitialDocument */ true,
+      /* aCOEP */ Nothing(),
+      /* aTryToSaveOldPresentation */ true,
+      /* aCheckPermitUnload */ true, aWindowActor);
+#ifdef DEBUG
+  if (NS_SUCCEEDED(rv)) {
+    RefPtr<Document> doc(GetDocument());
+    MOZ_ASSERT(
+        doc,
+        "Should have a document if CreateAboutBlankDocumentViewer succeeded");
+    MOZ_ASSERT(doc->GetOwnerGlobal() == aWindowActor->GetWindowGlobal(),
+               "New document should be in the same global as our actor");
+    MOZ_ASSERT(doc->IsInitialDocument(),
+               "New document should be an initial document");
+  }
+#endif
+
+  return rv;
+}
+
+bool nsDocShell::CanSavePresentation(uint32_t aLoadType,
+                                     nsIRequest* aNewRequest,
+                                     Document* aNewDocument,
+                                     bool aReportBFCacheComboTelemetry) {
+  if (!mOSHE) {
+    return false;  // no entry to save into
+  }
+
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent(),
+             "mOSHE cannot be non-null with SHIP");
+  nsCOMPtr<nsIDocumentViewer> viewer = mOSHE->GetDocumentViewer();
+  if (viewer) {
+    NS_WARNING("mOSHE already has a content viewer!");
+    return false;
+  }
+
+  // Only save presentation for "normal" loads and link loads.  Anything else
+  // probably wants to refetch the page, so caching the old presentation
+  // would be incorrect.
+  if (aLoadType != LOAD_NORMAL && aLoadType != LOAD_HISTORY &&
+      aLoadType != LOAD_LINK && aLoadType != LOAD_STOP_CONTENT &&
+      aLoadType != LOAD_STOP_CONTENT_AND_REPLACE &&
+      aLoadType != LOAD_ERROR_PAGE) {
+    return false;
+  }
+
+  // If the session history entry has the saveLayoutState flag set to false,
+  // then we should not cache the presentation.
+  if (!mOSHE->GetSaveLayoutStateFlag()) {
+    return false;
+  }
+
+  // If the document is not done loading, don't cache it.
+  if (!mScriptGlobal || mScriptGlobal->IsLoading()) {
+    MOZ_LOG(gPageCacheLog, mozilla::LogLevel::Verbose,
+            ("Blocked due to document still loading"));
+    return false;
+  }
+
+  if (mScriptGlobal->WouldReuseInnerWindow(aNewDocument)) {
+    return false;
+  }
+
+  // Avoid doing the work of saving the presentation state in the case where
+  // the content viewer cache is disabled.
+  if (nsSHistory::GetMaxTotalViewers() == 0) {
+    return false;
+  }
+
+  // Don't cache the content viewer if we're in a subframe.
+  if (mBrowsingContext->GetParent()) {
+    return false;  // this is a subframe load
+  }
+
+  // If the document does not want its presentation cached, then don't.
+  RefPtr<Document> doc = mScriptGlobal->GetExtantDoc();
+
+  uint32_t bfCacheCombo = 0;
+  bool canSavePresentation =
+      doc->CanSavePresentation(aNewRequest, bfCacheCombo, true);
+  MOZ_ASSERT_IF(canSavePresentation, bfCacheCombo == 0);
+  if (canSavePresentation && doc->IsTopLevelContentDocument()) {
+    auto* browsingContextGroup = mBrowsingContext->Group();
+    nsTArray<RefPtr<BrowsingContext>>& topLevelContext =
+        browsingContextGroup->Toplevels();
+
+    for (const auto& browsingContext : topLevelContext) {
+      if (browsingContext != mBrowsingContext) {
+        if (StaticPrefs::docshell_shistory_bfcache_require_no_opener()) {
+          canSavePresentation = false;
+        }
+        bfCacheCombo |= BFCacheStatus::NOT_ONLY_TOPLEVEL_IN_BCG;
+        break;
+      }
+    }
+  }
+
+  if (aReportBFCacheComboTelemetry) {
+    ReportBFCacheComboTelemetry(bfCacheCombo);
+  }
+  return doc && canSavePresentation;
+}
+
+/* static */
+void nsDocShell::ReportBFCacheComboTelemetry(uint32_t aCombo) {
+  // There are 11 possible reasons to make a request fails to use BFCache
+  // (see BFCacheStatus in dom/base/Document.h), and we'd like to record
+  // the common combinations for reasons which make requests fail to use
+  // BFCache. These combinations are generated based on some local browsings,
+  // we need to adjust them when necessary.
+  enum BFCacheStatusCombo : uint32_t {
+    BFCACHE_SUCCESS,
+    NOT_ONLY_TOPLEVEL = mozilla::dom::BFCacheStatus::NOT_ONLY_TOPLEVEL_IN_BCG,
+    // If both unload and beforeunload listeners are presented, it'll be
+    // recorded as unload
+    UNLOAD = mozilla::dom::BFCacheStatus::UNLOAD_LISTENER,
+    UNLOAD_REQUEST = mozilla::dom::BFCacheStatus::UNLOAD_LISTENER |
+                     mozilla::dom::BFCacheStatus::REQUEST,
+    REQUEST = mozilla::dom::BFCacheStatus::REQUEST,
+    UNLOAD_REQUEST_PEER = mozilla::dom::BFCacheStatus::UNLOAD_LISTENER |
+                          mozilla::dom::BFCacheStatus::REQUEST |
+                          mozilla::dom::BFCacheStatus::ACTIVE_PEER_CONNECTION,
+    UNLOAD_REQUEST_PEER_MSE =
+        mozilla::dom::BFCacheStatus::UNLOAD_LISTENER |
+        mozilla::dom::BFCacheStatus::REQUEST |
+        mozilla::dom::BFCacheStatus::ACTIVE_PEER_CONNECTION |
+        mozilla::dom::BFCacheStatus::CONTAINS_MSE_CONTENT,
+    UNLOAD_REQUEST_MSE = mozilla::dom::BFCacheStatus::UNLOAD_LISTENER |
+                         mozilla::dom::BFCacheStatus::REQUEST |
+                         mozilla::dom::BFCacheStatus::CONTAINS_MSE_CONTENT,
+    SUSPENDED_UNLOAD_REQUEST_PEER =
+        mozilla::dom::BFCacheStatus::SUSPENDED |
+        mozilla::dom::BFCacheStatus::UNLOAD_LISTENER |
+        mozilla::dom::BFCacheStatus::REQUEST |
+        mozilla::dom::BFCacheStatus::ACTIVE_PEER_CONNECTION,
+    REMOTE_SUBFRAMES = mozilla::dom::BFCacheStatus::CONTAINS_REMOTE_SUBFRAMES,
+    BEFOREUNLOAD = mozilla::dom::BFCacheStatus::BEFOREUNLOAD_LISTENER,
+  };
+
+  // Beforeunload is recorded as a blocker only if it is the only one to block
+  // bfcache.
+  if (aCombo != mozilla::dom::BFCacheStatus::BEFOREUNLOAD_LISTENER) {
+    aCombo &= ~mozilla::dom::BFCacheStatus::BEFOREUNLOAD_LISTENER;
+  }
+  switch (aCombo) {
+    case BFCACHE_SUCCESS:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::BFCache_Success);
+      break;
+    case NOT_ONLY_TOPLEVEL:
+      if (StaticPrefs::docshell_shistory_bfcache_require_no_opener()) {
+        Telemetry::AccumulateCategorical(
+            Telemetry::LABELS_BFCACHE_COMBO::Other);
+        break;
+      }
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::BFCache_Success);
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Success_Not_Toplevel);
+      break;
+    case UNLOAD:
+      Telemetry::AccumulateCategorical(Telemetry::LABELS_BFCACHE_COMBO::Unload);
+      break;
+    case BEFOREUNLOAD:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Beforeunload);
+      break;
+    case UNLOAD_REQUEST:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Unload_Req);
+      break;
+    case REQUEST:
+      Telemetry::AccumulateCategorical(Telemetry::LABELS_BFCACHE_COMBO::Req);
+      break;
+    case UNLOAD_REQUEST_PEER:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Unload_Req_Peer);
+      break;
+    case UNLOAD_REQUEST_PEER_MSE:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Unload_Req_Peer_MSE);
+      break;
+    case UNLOAD_REQUEST_MSE:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Unload_Req_MSE);
+      break;
+    case SUSPENDED_UNLOAD_REQUEST_PEER:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::SPD_Unload_Req_Peer);
+      break;
+    case REMOTE_SUBFRAMES:
+      Telemetry::AccumulateCategorical(
+          Telemetry::LABELS_BFCACHE_COMBO::Remote_Subframes);
+      break;
+    default:
+      Telemetry::AccumulateCategorical(Telemetry::LABELS_BFCACHE_COMBO::Other);
+      break;
+  }
+};
+
+void nsDocShell::ReattachEditorToWindow(nsISHEntry* aSHEntry) {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  NS_ASSERTION(!mEditorData,
+               "Why reattach an editor when we already have one?");
+  NS_ASSERTION(aSHEntry && aSHEntry->HasDetachedEditor(),
+               "Reattaching when there's not a detached editor.");
+
+  if (mEditorData || !aSHEntry) {
+    return;
+  }
+
+  mEditorData = WrapUnique(aSHEntry->ForgetEditorData());
+  if (mEditorData) {
+#ifdef DEBUG
+    nsresult rv =
+#endif
+        mEditorData->ReattachToWindow(this);
+    NS_ASSERTION(NS_SUCCEEDED(rv), "Failed to reattach editing session");
+  }
+}
+
+void nsDocShell::DetachEditorFromWindow() {
+  if (!mEditorData || mEditorData->WaitingForLoad()) {
+    // If there's nothing to detach, or if the editor data is actually set
+    // up for the _new_ page that's coming in, don't detach.
+    return;
+  }
+
+  NS_ASSERTION(!mOSHE || !mOSHE->HasDetachedEditor(),
+               "Detaching editor when it's already detached.");
+
+  nsresult res = mEditorData->DetachFromWindow();
+  NS_ASSERTION(NS_SUCCEEDED(res), "Failed to detach editor");
+
+  if (NS_SUCCEEDED(res)) {
+    // Make mOSHE hold the owning ref to the editor data.
+    if (mOSHE) {
+      MOZ_ASSERT(!mIsBeingDestroyed || !mOSHE->HasDetachedEditor(),
+                 "We should not set the editor data again once after we "
+                 "detached the editor data during destroying this docshell");
+      mOSHE->SetEditorData(mEditorData.release());
+    } else {
+      mEditorData = nullptr;
+    }
+  }
+
+#ifdef DEBUG
+  {
+    bool isEditable;
+    GetEditable(&isEditable);
+    NS_ASSERTION(!isEditable,
+                 "Window is still editable after detaching editor.");
+  }
+#endif  // DEBUG
+}
+
+nsresult nsDocShell::CaptureState() {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+
+  if (!mOSHE || mOSHE == mLSHE) {
+    // No entry to save into, or we're replacing the existing entry.
+    return NS_ERROR_FAILURE;
+  }
+
+  if (!mScriptGlobal) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsISupports> windowState = mScriptGlobal->SaveWindowState();
+  NS_ENSURE_TRUE(windowState, NS_ERROR_FAILURE);
+
+  if (MOZ_UNLIKELY(MOZ_LOG_TEST(gPageCacheLog, LogLevel::Debug))) {
+    nsAutoCString spec;
+    nsCOMPtr<nsIURI> uri = mOSHE->GetURI();
+    if (uri) {
+      uri->GetSpec(spec);
+    }
+    MOZ_LOG(gPageCacheLog, LogLevel::Debug,
+            ("Saving presentation into session history, URI: %s", spec.get()));
+  }
+
+  mOSHE->SetWindowState(windowState);
+
+  // Suspend refresh URIs and save off the timer queue
+  mOSHE->SetRefreshURIList(mSavedRefreshURIList);
+
+  // Capture the current content viewer bounds.
+  if (mDocumentViewer) {
+    nsIntRect bounds;
+    mDocumentViewer->GetBounds(bounds);
+    mOSHE->SetViewerBounds(bounds);
+  }
+
+  // Capture the docshell hierarchy.
+  mOSHE->ClearChildShells();
+
+  uint32_t childCount = mChildList.Length();
+  for (uint32_t i = 0; i < childCount; ++i) {
+    nsCOMPtr<nsIDocShellTreeItem> childShell = do_QueryInterface(ChildAt(i));
+    NS_ASSERTION(childShell, "null child shell");
+
+    mOSHE->AddChildShell(childShell);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::RestorePresentationEvent::Run() {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+
+  if (mDocShell && NS_FAILED(mDocShell->RestoreFromHistory())) {
+    NS_WARNING("RestoreFromHistory failed");
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::BeginRestore(nsIDocumentViewer* aDocumentViewer, bool aTop) {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+
+  nsresult rv;
+  if (!aDocumentViewer) {
+    rv = EnsureDocumentViewer();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    aDocumentViewer = mDocumentViewer;
+  }
+
+  // Dispatch events for restoring the presentation.  We try to simulate
+  // the progress notifications loading the document would cause, so we add
+  // the document's channel to the loadgroup to initiate stateChange
+  // notifications.
+
+  RefPtr<Document> doc = aDocumentViewer->GetDocument();
+  if (doc) {
+    nsIChannel* channel = doc->GetChannel();
+    if (channel) {
+      mEODForCurrentDocument = false;
+      mIsRestoringDocument = true;
+      mLoadGroup->AddRequest(channel, nullptr);
+      mIsRestoringDocument = false;
+    }
+  }
+
+  if (!aTop) {
+    // This point corresponds to us having gotten OnStartRequest or
+    // STATE_START, so do the same thing that CreateDocumentViewer does at
+    // this point to ensure that unload/pagehide events for this document
+    // will fire when it's unloaded again.
+    mFiredUnloadEvent = false;
+
+    // For non-top frames, there is no notion of making sure that the
+    // previous document is in the domwindow when STATE_START notifications
+    // happen.  We can just call BeginRestore for all of the child shells
+    // now.
+    rv = BeginRestoreChildren();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::BeginRestoreChildren() {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+
+  for (auto* childDocLoader : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> child = do_QueryObject(childDocLoader);
+    if (child) {
+      nsresult rv = child->BeginRestore(nullptr, false);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::FinishRestore() {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+
+  // First we call finishRestore() on our children.  In the simulated load,
+  // all of the child frames finish loading before the main document.
+
+  for (auto* childDocLoader : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> child = do_QueryObject(childDocLoader);
+    if (child) {
+      child->FinishRestore();
+    }
+  }
+
+  if (mOSHE && mOSHE->HasDetachedEditor()) {
+    ReattachEditorToWindow(mOSHE);
+  }
+
+  RefPtr<Document> doc = GetDocument();
+  if (doc) {
+    // Finally, we remove the request from the loadgroup.  This will
+    // cause onStateChange(STATE_STOP) to fire, which will fire the
+    // pageshow event to the chrome.
+
+    nsIChannel* channel = doc->GetChannel();
+    if (channel) {
+      mIsRestoringDocument = true;
+      mLoadGroup->RemoveRequest(channel, nullptr, NS_OK);
+      mIsRestoringDocument = false;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetRestoringDocument(bool* aRestoring) {
+  *aRestoring = mIsRestoringDocument;
+  return NS_OK;
+}
+
+nsresult nsDocShell::RestorePresentation(nsISHEntry* aSHEntry,
+                                         bool* aRestoring) {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  NS_ASSERTION(mLoadType & LOAD_CMD_HISTORY,
+               "RestorePresentation should only be called for history loads");
+
+  nsCOMPtr<nsIDocumentViewer> viewer = aSHEntry->GetDocumentViewer();
+
+  nsAutoCString spec;
+  if (MOZ_UNLIKELY(MOZ_LOG_TEST(gPageCacheLog, LogLevel::Debug))) {
+    nsCOMPtr<nsIURI> uri = aSHEntry->GetURI();
+    if (uri) {
+      uri->GetSpec(spec);
+    }
+  }
+
+  *aRestoring = false;
+
+  if (!viewer) {
+    MOZ_LOG(gPageCacheLog, LogLevel::Debug,
+            ("no saved presentation for uri: %s", spec.get()));
+    return NS_OK;
+  }
+
+  // We need to make sure the content viewer's container is this docshell.
+  // In subframe navigation, it's possible for the docshell that the
+  // content viewer was originally loaded into to be replaced with a
+  // different one.  We don't currently support restoring the presentation
+  // in that case.
+
+  nsCOMPtr<nsIDocShell> container;
+  viewer->GetContainer(getter_AddRefs(container));
+  if (!::SameCOMIdentity(container, GetAsSupports(this))) {
+    MOZ_LOG(gPageCacheLog, LogLevel::Debug,
+            ("No valid container, clearing presentation"));
+    aSHEntry->SetDocumentViewer(nullptr);
+    return NS_ERROR_FAILURE;
+  }
+
+  NS_ASSERTION(mDocumentViewer != viewer, "Restoring existing presentation");
+
+  MOZ_LOG(gPageCacheLog, LogLevel::Debug,
+          ("restoring presentation from session history: %s", spec.get()));
+
+  SetHistoryEntryAndUpdateBC(Some(aSHEntry), Nothing());
+
+  // Post an event that will remove the request after we've returned
+  // to the event loop.  This mimics the way it is called by nsIChannel
+  // implementations.
+
+  // Revoke any pending restore (just in case).
+  NS_ASSERTION(!mRestorePresentationEvent.IsPending(),
+               "should only have one RestorePresentationEvent");
+  mRestorePresentationEvent.Revoke();
+
+  RefPtr<RestorePresentationEvent> evt = new RestorePresentationEvent(this);
+  nsresult rv = Dispatch(do_AddRef(evt));
+  if (NS_SUCCEEDED(rv)) {
+    mRestorePresentationEvent = evt.get();
+    // The rest of the restore processing will happen on our event
+    // callback.
+    *aRestoring = true;
+  }
+
+  return rv;
+}
+
+namespace {
+class MOZ_STACK_CLASS PresentationEventForgetter {
+ public:
+  explicit PresentationEventForgetter(
+      nsRevocableEventPtr<nsDocShell::RestorePresentationEvent>&
+          aRestorePresentationEvent)
+      : mRestorePresentationEvent(aRestorePresentationEvent),
+        mEvent(aRestorePresentationEvent.get()) {}
+
+  ~PresentationEventForgetter() { Forget(); }
+
+  void Forget() {
+    if (mRestorePresentationEvent.get() == mEvent) {
+      mRestorePresentationEvent.Forget();
+      mEvent = nullptr;
+    }
+  }
+
+ private:
+  nsRevocableEventPtr<nsDocShell::RestorePresentationEvent>&
+      mRestorePresentationEvent;
+  RefPtr<nsDocShell::RestorePresentationEvent> mEvent;
+};
+
+}  // namespace
+
+bool nsDocShell::SandboxFlagsImplyCookies(const uint32_t& aSandboxFlags) {
+  return (aSandboxFlags & (SANDBOXED_ORIGIN | SANDBOXED_SCRIPTS)) == 0;
+}
+
+nsresult nsDocShell::RestoreFromHistory() {
+  MOZ_ASSERT(!mozilla::SessionHistoryInParent());
+  MOZ_ASSERT(mRestorePresentationEvent.IsPending());
+  PresentationEventForgetter forgetter(mRestorePresentationEvent);
+
+  // This section of code follows the same ordering as CreateDocumentViewer.
+  if (!mLSHE) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIDocumentViewer> viewer = mLSHE->GetDocumentViewer();
+  if (!viewer) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (mSavingOldViewer) {
+    // We determined that it was safe to cache the document presentation
+    // at the time we initiated the new load.  We need to check whether
+    // it's still safe to do so, since there may have been DOM mutations
+    // or new requests initiated.
+    RefPtr<Document> doc = viewer->GetDocument();
+    nsIRequest* request = nullptr;
+    if (doc) {
+      request = doc->GetChannel();
+    }
+    mSavingOldViewer = CanSavePresentation(
+        mLoadType, request, doc, /* aReportBFCacheComboTelemetry */ false);
+  }
+
+  // Protect against mLSHE going away via a load triggered from
+  // pagehide or unload.
+  nsCOMPtr<nsISHEntry> origLSHE = mLSHE;
+
+  // Make sure to blow away our mLoadingURI just in case.  No loads
+  // from inside this pagehide.
+  mLoadingURI = nullptr;
+
+  // Notify the old content viewer that it's being hidden.
+  FirePageHideNotification(!mSavingOldViewer);
+  // pagehide notification might destroy this docshell.
+  if (mIsBeingDestroyed) {
+    return NS_ERROR_DOCSHELL_DYING;
+  }
+
+  // If mLSHE was changed as a result of the pagehide event, then
+  // something else was loaded.  Don't finish restoring.
+  if (mLSHE != origLSHE) {
+    return NS_OK;
+  }
+
+  // Add the request to our load group.  We do this before swapping out
+  // the content viewers so that consumers of STATE_START can access
+  // the old document.  We only deal with the toplevel load at this time --
+  // to be consistent with normal document loading, subframes cannot start
+  // loading until after data arrives, which is after STATE_START completes.
+
+  RefPtr<RestorePresentationEvent> currentPresentationRestoration =
+      mRestorePresentationEvent.get();
+  Stop();
+  // Make sure we're still restoring the same presentation.
+  // If we aren't, docshell is in process doing another load already.
+  NS_ENSURE_STATE(currentPresentationRestoration ==
+                  mRestorePresentationEvent.get());
+  BeginRestore(viewer, true);
+  NS_ENSURE_STATE(currentPresentationRestoration ==
+                  mRestorePresentationEvent.get());
+  forgetter.Forget();
+
+  // Set mFiredUnloadEvent = false so that the unload handler for the
+  // *new* document will fire.
+  mFiredUnloadEvent = false;
+
+  mURIResultedInDocument = true;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (rootSH) {
+    mPreviousEntryIndex = rootSH->Index();
+    rootSH->LegacySHistory()->UpdateIndex();
+    mLoadedEntryIndex = rootSH->Index();
+    MOZ_LOG(gPageCacheLog, LogLevel::Verbose,
+            ("Previous index: %d, Loaded index: %d", mPreviousEntryIndex,
+             mLoadedEntryIndex));
+  }
+
+  // Rather than call Embed(), we will retrieve the viewer from the session
+  // history entry and swap it in.
+  // XXX can we refactor this so that we can just call Embed()?
+  PersistLayoutHistoryState();
+  nsresult rv;
+  if (mDocumentViewer) {
+    if (mSavingOldViewer && NS_FAILED(CaptureState())) {
+      if (mOSHE) {
+        mOSHE->SyncPresentationState();
+      }
+      mSavingOldViewer = false;
+    }
+  }
+
+  mSavedRefreshURIList = nullptr;
+
+  // In cases where we use a transient about:blank viewer between loads,
+  // we never show the transient viewer, so _its_ previous viewer is never
+  // unhooked from the view hierarchy.  Destroy any such previous viewer now,
+  // before we grab the root view sibling, so that we don't grab a view
+  // that's about to go away.
+
+  if (mDocumentViewer) {
+    // Make sure to hold a strong ref to previousViewer here while we
+    // drop the reference to it from mDocumentViewer.
+    nsCOMPtr<nsIDocumentViewer> previousViewer =
+        mDocumentViewer->GetPreviousViewer();
+    if (previousViewer) {
+      mDocumentViewer->SetPreviousViewer(nullptr);
+      previousViewer->Destroy();
+    }
+  }
+
+  // Save off the root view's parent and sibling so that we can insert the
+  // new content viewer's root view at the same position.  Also save the
+  // bounds of the root view's widget.
+
+  nsView* rootViewSibling = nullptr;
+  nsView* rootViewParent = nullptr;
+  nsIntRect newBounds(0, 0, 0, 0);
+
+  PresShell* oldPresShell = GetPresShell();
+  if (oldPresShell) {
+    nsViewManager* vm = oldPresShell->GetViewManager();
+    if (vm) {
+      nsView* oldRootView = vm->GetRootView();
+
+      if (oldRootView) {
+        rootViewSibling = oldRootView->GetNextSibling();
+        rootViewParent = oldRootView->GetParent();
+
+        mDocumentViewer->GetBounds(newBounds);
+      }
+    }
+  }
+
+  nsCOMPtr<nsIContent> container;
+  RefPtr<Document> sibling;
+  if (rootViewParent && rootViewParent->GetParent()) {
+    nsIFrame* frame = rootViewParent->GetParent()->GetFrame();
+    container = frame ? frame->GetContent() : nullptr;
+  }
+  if (rootViewSibling) {
+    nsIFrame* frame = rootViewSibling->GetFrame();
+    sibling = frame ? frame->PresShell()->GetDocument() : nullptr;
+  }
+
+  // Transfer ownership to mDocumentViewer.  By ensuring that either the
+  // docshell or the session history, but not both, have references to the
+  // content viewer, we prevent the viewer from being torn down after
+  // Destroy() is called.
+
+  if (mDocumentViewer) {
+    mDocumentViewer->Close(mSavingOldViewer ? mOSHE.get() : nullptr);
+    viewer->SetPreviousViewer(mDocumentViewer);
+  }
+  if (mOSHE && (!mDocumentViewer || !mSavingOldViewer)) {
+    // We don't plan to save a viewer in mOSHE; tell it to drop
+    // any other state it's holding.
+    mOSHE->SyncPresentationState();
+  }
+
+  // Order the mDocumentViewer setup just like Embed does.
+  mDocumentViewer = nullptr;
+
+  // Now that we're about to switch documents, forget all of our children.
+  // Note that we cached them as needed up in CaptureState above.
+  DestroyChildren();
+
+  mDocumentViewer.swap(viewer);
+
+  // Grab all of the related presentation from the SHEntry now.
+  // Clearing the viewer from the SHEntry will clear all of this state.
+  nsCOMPtr<nsISupports> windowState = mLSHE->GetWindowState();
+  mLSHE->SetWindowState(nullptr);
+
+  bool sticky = mLSHE->GetSticky();
+
+  RefPtr<Document> document = mDocumentViewer->GetDocument();
+
+  nsCOMArray<nsIDocShellTreeItem> childShells;
+  int32_t i = 0;
+  nsCOMPtr<nsIDocShellTreeItem> child;
+  while (NS_SUCCEEDED(mLSHE->ChildShellAt(i++, getter_AddRefs(child))) &&
+         child) {
+    childShells.AppendObject(child);
+  }
+
+  // get the previous content viewer size
+  nsIntRect oldBounds(0, 0, 0, 0);
+  mLSHE->GetViewerBounds(oldBounds);
+
+  // Restore the refresh URI list.  The refresh timers will be restarted
+  // when EndPageLoad() is called.
+  nsCOMPtr<nsIMutableArray> refreshURIList = mLSHE->GetRefreshURIList();
+
+  // Reattach to the window object.
+  mIsRestoringDocument = true;  // for MediaDocument::BecomeInteractive
+  rv = mDocumentViewer->Open(windowState, mLSHE);
+  mIsRestoringDocument = false;
+
+  // Hack to keep nsDocShellEditorData alive across the
+  // SetContentViewer(nullptr) call below.
+  UniquePtr<nsDocShellEditorData> data(mLSHE->ForgetEditorData());
+
+  // Now remove it from the cached presentation.
+  mLSHE->SetDocumentViewer(nullptr);
+  mEODForCurrentDocument = false;
+
+  mLSHE->SetEditorData(data.release());
+
+#ifdef DEBUG
+  {
+    nsCOMPtr<nsIMutableArray> refreshURIs = mLSHE->GetRefreshURIList();
+    nsCOMPtr<nsIDocShellTreeItem> childShell;
+    mLSHE->ChildShellAt(0, getter_AddRefs(childShell));
+    NS_ASSERTION(!refreshURIs && !childShell,
+                 "SHEntry should have cleared presentation state");
+  }
+#endif
+
+  // Restore the sticky state of the viewer.  The viewer has set this state
+  // on the history entry in Destroy() just before marking itself non-sticky,
+  // to avoid teardown of the presentation.
+  mDocumentViewer->SetSticky(sticky);
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // mLSHE is now our currently-loaded document.
+  SetHistoryEntryAndUpdateBC(Nothing(), Some<nsISHEntry*>(mLSHE));
+
+  // We aren't going to restore any items from the LayoutHistoryState,
+  // but we don't want them to stay around in case the page is reloaded.
+  SetLayoutHistoryState(nullptr);
+
+  // This is the end of our Embed() replacement
+
+  mSavingOldViewer = false;
+  mEODForCurrentDocument = false;
+
+  if (document) {
+    RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
+    if (parent) {
+      RefPtr<Document> d = parent->GetDocument();
+      if (d) {
+        if (d->EventHandlingSuppressed()) {
+          document->SuppressEventHandling(d->EventHandlingSuppressed());
+        }
+      }
+    }
+
+    // Use the uri from the mLSHE we had when we entered this function
+    // (which need not match the document's URI if anchors are involved),
+    // since that's the history entry we're loading.  Note that if we use
+    // origLSHE we don't have to worry about whether the entry in question
+    // is still mLSHE or whether it's now mOSHE.
+    nsCOMPtr<nsIURI> uri = origLSHE->GetURI();
+    SetCurrentURI(uri, document->GetChannel(), /* aFireLocationChange */ true,
+                  /* aIsInitialAboutBlank */ false,
+                  /* aLocationFlags */ 0);
+  }
+
+  // This is the end of our CreateDocumentViewer() replacement.
+  // Now we simulate a load.  First, we restore the state of the javascript
+  // window object.
+  nsCOMPtr<nsPIDOMWindowOuter> privWin = GetWindow();
+  NS_ASSERTION(privWin, "could not get nsPIDOMWindow interface");
+
+  // Now, dispatch a title change event which would happen as the
+  // <head> is parsed.
+  document->NotifyPossibleTitleChange(false);
+
+  // Now we simulate appending child docshells for subframes.
+  for (i = 0; i < childShells.Count(); ++i) {
+    nsIDocShellTreeItem* childItem = childShells.ObjectAt(i);
+    nsCOMPtr<nsIDocShell> childShell = do_QueryInterface(childItem);
+
+    // Make sure to not clobber the state of the child.  Since AddChild
+    // always clobbers it, save it off first.
+    bool allowRedirects;
+    childShell->GetAllowMetaRedirects(&allowRedirects);
+
+    bool allowSubframes;
+    childShell->GetAllowSubframes(&allowSubframes);
+
+    bool allowImages;
+    childShell->GetAllowImages(&allowImages);
+
+    bool allowMedia = childShell->GetAllowMedia();
+
+    bool allowDNSPrefetch;
+    childShell->GetAllowDNSPrefetch(&allowDNSPrefetch);
+
+    bool allowContentRetargeting = childShell->GetAllowContentRetargeting();
+    bool allowContentRetargetingOnChildren =
+        childShell->GetAllowContentRetargetingOnChildren();
+
+    // this.AddChild(child) calls child.SetDocLoaderParent(this), meaning that
+    // the child inherits our state. Among other things, this means that the
+    // child inherits our mPrivateBrowsingId, which is what we want.
+    AddChild(childItem);
+
+    childShell->SetAllowMetaRedirects(allowRedirects);
+    childShell->SetAllowSubframes(allowSubframes);
+    childShell->SetAllowImages(allowImages);
+    childShell->SetAllowMedia(allowMedia);
+    childShell->SetAllowDNSPrefetch(allowDNSPrefetch);
+    childShell->SetAllowContentRetargeting(allowContentRetargeting);
+    childShell->SetAllowContentRetargetingOnChildren(
+        allowContentRetargetingOnChildren);
+
+    rv = childShell->BeginRestore(nullptr, false);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // Make sure to restore the window state after adding the child shells back
+  // to the tree.  This is necessary for Thaw() and Resume() to propagate
+  // properly.
+  rv = privWin->RestoreWindowState(windowState);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  RefPtr<PresShell> presShell = GetPresShell();
+
+  // We may be displayed on a different monitor (or in a different
+  // HiDPI mode) than when we got into the history list.  So we need
+  // to check if this has happened. See bug 838239.
+
+  // Because the prescontext normally handles resolution changes via
+  // a runnable (see nsPresContext::UIResolutionChanged), its device
+  // context won't be -immediately- updated as a result of calling
+  // presShell->BackingScaleFactorChanged().
+
+  // But we depend on that device context when adjusting the view size
+  // via mDocumentViewer->SetBounds(newBounds) below. So we need to
+  // explicitly tell it to check for changed resolution here.
+  if (presShell) {
+    RefPtr<nsPresContext> pc = presShell->GetPresContext();
+    if (pc->DeviceContext()->CheckDPIChange()) {
+      presShell->BackingScaleFactorChanged();
+    }
+    // Recompute zoom and text-zoom and such.
+    pc->RecomputeBrowsingContextDependentData();
+  }
+
+  nsViewManager* newVM = presShell ? presShell->GetViewManager() : nullptr;
+  nsView* newRootView = newVM ? newVM->GetRootView() : nullptr;
+
+  // Insert the new root view at the correct location in the view tree.
+  if (container) {
+    nsSubDocumentFrame* subDocFrame =
+        do_QueryFrame(container->GetPrimaryFrame());
+    rootViewParent = subDocFrame ? subDocFrame->EnsureInnerView() : nullptr;
+  } else {
+    rootViewParent = nullptr;
+  }
+  if (sibling && sibling->GetPresShell() &&
+      sibling->GetPresShell()->GetViewManager()) {
+    rootViewSibling = sibling->GetPresShell()->GetViewManager()->GetRootView();
+  } else {
+    rootViewSibling = nullptr;
+  }
+  if (rootViewParent && newRootView &&
+      newRootView->GetParent() != rootViewParent) {
+    nsViewManager* parentVM = rootViewParent->GetViewManager();
+    if (parentVM) {
+      // InsertChild(parent, child, sib, true) inserts the child after
+      // sib in content order, which is before sib in view order. BUT
+      // when sib is null it inserts at the end of the the document
+      // order, i.e., first in view order.  But when oldRootSibling is
+      // null, the old root as at the end of the view list --- last in
+      // content order --- and we want to call InsertChild(parent, child,
+      // nullptr, false) in that case.
+      parentVM->InsertChild(rootViewParent, newRootView, rootViewSibling,
+                            rootViewSibling ? true : false);
+
+      NS_ASSERTION(newRootView->GetNextSibling() == rootViewSibling,
+                   "error in InsertChild");
+    }
+  }
+
+  nsCOMPtr<nsPIDOMWindowInner> privWinInner = privWin->GetCurrentInnerWindow();
+
+  // If parent is suspended, increase suspension count.
+  // This can't be done as early as event suppression since this
+  // depends on docshell tree.
+  privWinInner->SyncStateFromParentWindow();
+
+  // Now that all of the child docshells have been put into place, we can
+  // restart the timers for the window and all of the child frames.
+  privWinInner->Resume();
+
+  // Now that we have found the inner window of the page restored
+  // from the history, we have to  make sure that
+  // performance.navigation.type is 2.
+  Performance* performance = privWinInner->GetPerformance();
+  if (performance) {
+    performance->GetDOMTiming()->NotifyRestoreStart();
+  }
+
+  // Restore the refresh URI list.  The refresh timers will be restarted
+  // when EndPageLoad() is called.
+  mRefreshURIList = refreshURIList;
+
+  // Meta-refresh timers have been restarted for this shell, but not
+  // for our children.  Walk the child shells and restart their timers.
+  for (auto* childDocLoader : mChildList.ForwardRange()) {
+    nsCOMPtr<nsIDocShell> child = do_QueryObject(childDocLoader);
+    if (child) {
+      child->ResumeRefreshURIs();
+    }
+  }
+
+  // Make sure this presentation is the same size as the previous
+  // presentation.  If this is not the same size we showed it at last time,
+  // then we need to resize the widget.
+
+  // XXXbryner   This interacts poorly with Firefox's infobar.  If the old
+  // presentation had the infobar visible, then we will resize the new
+  // presentation to that smaller size.  However, firing the locationchanged
+  // event will hide the infobar, which will immediately resize the window
+  // back to the larger size.  A future optimization might be to restore
+  // the presentation at the "wrong" size, then fire the locationchanged
+  // event and check whether the docshell's new size is the same as the
+  // cached viewer size (skipping the resize if they are equal).
+
+  if (newRootView) {
+    if (!newBounds.IsEmpty() && !newBounds.IsEqualEdges(oldBounds)) {
+      MOZ_LOG(gPageCacheLog, LogLevel::Debug,
+              ("resize widget(%d, %d, %d, %d)", newBounds.x, newBounds.y,
+               newBounds.width, newBounds.height));
+      mDocumentViewer->SetBounds(newBounds);
+    } else {
+      nsIScrollableFrame* rootScrollFrame =
+          presShell->GetRootScrollFrameAsScrollable();
+      if (rootScrollFrame) {
+        rootScrollFrame->PostScrolledAreaEventForCurrentArea();
+      }
+    }
+  }
+
+  // The FinishRestore call below can kill these, null them out so we don't
+  // have invalid pointer lying around.
+  newRootView = rootViewSibling = rootViewParent = nullptr;
+  newVM = nullptr;
+
+  // If the IsUnderHiddenEmbedderElement() state has been changed, we need to
+  // update it.
+  if (oldPresShell && presShell &&
+      presShell->IsUnderHiddenEmbedderElement() !=
+          oldPresShell->IsUnderHiddenEmbedderElement()) {
+    presShell->SetIsUnderHiddenEmbedderElement(
+        oldPresShell->IsUnderHiddenEmbedderElement());
+  }
+
+  // Simulate the completion of the load.
+  nsDocShell::FinishRestore();
+
+  // Restart plugins, and paint the content.
+  if (presShell) {
+    presShell->Thaw();
+  }
+
+  return privWin->FireDelayedDOMEvents(true);
+}
+
+nsresult nsDocShell::CreateDocumentViewer(const nsACString& aContentType,
+                                          nsIRequest* aRequest,
+                                          nsIStreamListener** aContentHandler) {
+  *aContentHandler = nullptr;
+
+  if (!mTreeOwner || mIsBeingDestroyed) {
+    // If we don't have a tree owner, then we're in the process of being
+    // destroyed. Rather than continue trying to load something, just give up.
+    return NS_ERROR_DOCSHELL_DYING;
+  }
+
+  if (!mBrowsingContext->AncestorsAreCurrent() ||
+      mBrowsingContext->IsInBFCache()) {
+    mBrowsingContext->RemoveRootFromBFCacheSync();
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // Can we check the content type of the current content viewer
+  // and reuse it without destroying it and re-creating it?
+
+  NS_ASSERTION(mLoadGroup, "Someone ignored return from Init()?");
+
+  // Instantiate the content viewer object
+  nsCOMPtr<nsIDocumentViewer> viewer;
+  nsresult rv = NewDocumentViewerObj(aContentType, aRequest, mLoadGroup,
+                                     aContentHandler, getter_AddRefs(viewer));
+
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // Notify the current document that it is about to be unloaded!!
+  //
+  // It is important to fire the unload() notification *before* any state
+  // is changed within the DocShell - otherwise, javascript will get the
+  // wrong information :-(
+  //
+
+  if (mSavingOldViewer) {
+    // We determined that it was safe to cache the document presentation
+    // at the time we initiated the new load.  We need to check whether
+    // it's still safe to do so, since there may have been DOM mutations
+    // or new requests initiated.
+    RefPtr<Document> doc = viewer->GetDocument();
+    mSavingOldViewer = CanSavePresentation(
+        mLoadType, aRequest, doc, /* aReportBFCacheComboTelemetry */ false);
+  }
+
+  NS_ASSERTION(!mLoadingURI, "Re-entering unload?");
+
+  nsCOMPtr<nsIChannel> aOpenedChannel = do_QueryInterface(aRequest);
+  if (aOpenedChannel) {
+    aOpenedChannel->GetURI(getter_AddRefs(mLoadingURI));
+  }
+
+  // Grab the current URI, we need to pass it to Embed, and OnNewURI will reset
+  // it before we do call Embed.
+  nsCOMPtr<nsIURI> previousURI = mCurrentURI;
+
+  FirePageHideNotification(!mSavingOldViewer);
+  if (mIsBeingDestroyed) {
+    // Force to stop the newly created orphaned viewer.
+    viewer->Stop();
+    return NS_ERROR_DOCSHELL_DYING;
+  }
+  mLoadingURI = nullptr;
+
+  // Set mFiredUnloadEvent = false so that the unload handler for the
+  // *new* document will fire.
+  mFiredUnloadEvent = false;
+
+  // we've created a new document so go ahead and call
+  // OnNewURI(), but don't fire OnLocationChange()
+  // notifications before we've called Embed(). See bug 284993.
+  mURIResultedInDocument = true;
+  bool errorOnLocationChangeNeeded = false;
+  nsCOMPtr<nsIChannel> failedChannel = mFailedChannel;
+  nsCOMPtr<nsIURI> failedURI;
+
+  if (mLoadType == LOAD_ERROR_PAGE) {
+    // We need to set the SH entry and our current URI here and not
+    // at the moment we load the page. We want the same behavior
+    // of Stop() as for a normal page load. See bug 514232 for details.
+
+    // Revert mLoadType to load type to state the page load failed,
+    // following function calls need it.
+    mLoadType = mFailedLoadType;
+
+    Document* doc = viewer->GetDocument();
+    if (doc) {
+      doc->SetFailedChannel(failedChannel);
+    }
+
+    nsCOMPtr<nsIPrincipal> triggeringPrincipal;
+    if (failedChannel) {
+      // Make sure we have a URI to set currentURI.
+      NS_GetFinalChannelURI(failedChannel, getter_AddRefs(failedURI));
+    } else {
+      // if there is no failed channel we have to explicitly provide
+      // a triggeringPrincipal for the history entry.
+      triggeringPrincipal = nsContentUtils::GetSystemPrincipal();
+    }
+
+    if (!failedURI) {
+      failedURI = mFailedURI;
+    }
+    if (!failedURI) {
+      // We need a URI object to store a session history entry, so make up a URI
+      NS_NewURI(getter_AddRefs(failedURI), "about:blank");
+    }
+
+    // When we don't have failedURI, something wrong will happen. See
+    // bug 291876.
+    MOZ_ASSERT(failedURI, "We don't have a URI for history APIs.");
+
+    mFailedChannel = nullptr;
+    mFailedURI = nullptr;
+
+    // Create an shistory entry for the old load.
+    if (failedURI) {
+      errorOnLocationChangeNeeded =
+          OnNewURI(failedURI, failedChannel, triggeringPrincipal, nullptr,
+                   nullptr, nullptr, false, false);
+    }
+
+    // Be sure to have a correct mLSHE, it may have been cleared by
+    // EndPageLoad. See bug 302115.
+    ChildSHistory* shistory = GetSessionHistory();
+    if (!mozilla::SessionHistoryInParent() && shistory && !mLSHE) {
+      int32_t idx = shistory->LegacySHistory()->GetRequestedIndex();
+      if (idx == -1) {
+        idx = shistory->Index();
+      }
+      shistory->LegacySHistory()->GetEntryAtIndex(idx, getter_AddRefs(mLSHE));
+    }
+
+    mLoadType = LOAD_ERROR_PAGE;
+  }
+
+  nsCOMPtr<nsIURI> finalURI;
+  // If this a redirect, use the final url (uri)
+  // else use the original url
+  //
+  // Note that this should match what documents do (see Document::Reset).
+  NS_GetFinalChannelURI(aOpenedChannel, getter_AddRefs(finalURI));
+
+  bool onLocationChangeNeeded = false;
+  if (finalURI) {
+    // Pass false for aCloneSHChildren, since we're loading a new page here.
+    onLocationChangeNeeded = OnNewURI(finalURI, aOpenedChannel, nullptr,
+                                      nullptr, nullptr, nullptr, true, false);
+  }
+
+  // let's try resetting the load group if we need to...
+  nsCOMPtr<nsILoadGroup> currentLoadGroup;
+  NS_ENSURE_SUCCESS(
+      aOpenedChannel->GetLoadGroup(getter_AddRefs(currentLoadGroup)),
+      NS_ERROR_FAILURE);
+
+  if (currentLoadGroup != mLoadGroup) {
+    nsLoadFlags loadFlags = 0;
+
+    // Cancel any URIs that are currently loading...
+    // XXX: Need to do this eventually      Stop();
+    //
+    // Retarget the document to this loadgroup...
+    //
+    /* First attach the channel to the right loadgroup
+     * and then remove from the old loadgroup. This
+     * puts the notifications in the right order and
+     * we don't null-out mLSHE in OnStateChange() for
+     * all redirected urls
+     */
+    aOpenedChannel->SetLoadGroup(mLoadGroup);
+
+    // Mark the channel as being a document URI...
+    aOpenedChannel->GetLoadFlags(&loadFlags);
+    loadFlags |= nsIChannel::LOAD_DOCUMENT_URI;
+    nsCOMPtr<nsILoadInfo> loadInfo = aOpenedChannel->LoadInfo();
+    if (SandboxFlagsImplyCookies(loadInfo->GetSandboxFlags())) {
+      loadFlags |= nsIRequest::LOAD_DOCUMENT_NEEDS_COOKIE;
+    }
+
+    aOpenedChannel->SetLoadFlags(loadFlags);
+
+    mLoadGroup->AddRequest(aRequest, nullptr);
+    if (currentLoadGroup) {
+      currentLoadGroup->RemoveRequest(aRequest, nullptr, NS_BINDING_RETARGETED);
+    }
+
+    // Update the notification callbacks, so that progress and
+    // status information are sent to the right docshell...
+    aOpenedChannel->SetNotificationCallbacks(this);
+  }
+
+  NS_ENSURE_SUCCESS(Embed(viewer, nullptr, false,
+                          ShouldAddToSessionHistory(finalURI, aOpenedChannel),
+                          aOpenedChannel, previousURI),
+                    NS_ERROR_FAILURE);
+
+  if (!mBrowsingContext->GetHasLoadedNonInitialDocument()) {
+    MOZ_ALWAYS_SUCCEEDS(mBrowsingContext->SetHasLoadedNonInitialDocument(true));
+  }
+
+  mSavedRefreshURIList = nullptr;
+  mSavingOldViewer = false;
+  mEODForCurrentDocument = false;
+
+  // if this document is part of a multipart document,
+  // the ID can be used to distinguish it from the other parts.
+  nsCOMPtr<nsIMultiPartChannel> multiPartChannel(do_QueryInterface(aRequest));
+  if (multiPartChannel) {
+    if (PresShell* presShell = GetPresShell()) {
+      if (Document* doc = presShell->GetDocument()) {
+        uint32_t partID;
+        multiPartChannel->GetPartID(&partID);
+        doc->SetPartID(partID);
+      }
+    }
+  }
+
+  if (errorOnLocationChangeNeeded) {
+    FireOnLocationChange(this, failedChannel, failedURI,
+                         LOCATION_CHANGE_ERROR_PAGE);
+  } else if (onLocationChangeNeeded) {
+    uint32_t locationFlags =
+        (mLoadType & LOAD_CMD_RELOAD) ? uint32_t(LOCATION_CHANGE_RELOAD) : 0;
+    FireOnLocationChange(this, aRequest, mCurrentURI, locationFlags);
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::NewDocumentViewerObj(const nsACString& aContentType,
+                                          nsIRequest* aRequest,
+                                          nsILoadGroup* aLoadGroup,
+                                          nsIStreamListener** aContentHandler,
+                                          nsIDocumentViewer** aViewer) {
+  nsCOMPtr<nsIChannel> aOpenedChannel = do_QueryInterface(aRequest);
+
+  nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory =
+      nsContentUtils::FindInternalDocumentViewer(aContentType);
+  if (!docLoaderFactory) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Now create an instance of the content viewer nsLayoutDLF makes the
+  // determination if it should be a "view-source" instead of "view"
+  nsresult rv = docLoaderFactory->CreateInstance(
+      "view", aOpenedChannel, aLoadGroup, aContentType, this, nullptr,
+      aContentHandler, aViewer);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  (*aViewer)->SetContainer(this);
+  return NS_OK;
+}
+
+nsresult nsDocShell::SetupNewViewer(nsIDocumentViewer* aNewViewer,
+                                    WindowGlobalChild* aWindowActor) {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  //
+  // Copy content viewer state from previous or parent content viewer.
+  //
+  // The following logic is mirrored in nsHTMLDocument::StartDocumentLoad!
+  //
+  // Do NOT to maintain a reference to the old content viewer outside
+  // of this "copying" block, or it will not be destroyed until the end of
+  // this routine and all <SCRIPT>s and event handlers fail! (bug 20315)
+  //
+  // In this block of code, if we get an error result, we return it
+  // but if we get a null pointer, that's perfectly legal for parent
+  // and parentContentViewer.
+  //
+
+  int32_t x = 0;
+  int32_t y = 0;
+  int32_t cx = 0;
+  int32_t cy = 0;
+
+  // This will get the size from the current content viewer or from the
+  // Init settings
+  DoGetPositionAndSize(&x, &y, &cx, &cy);
+
+  nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
+  NS_ENSURE_SUCCESS(GetInProcessSameTypeParent(getter_AddRefs(parentAsItem)),
+                    NS_ERROR_FAILURE);
+  nsCOMPtr<nsIDocShell> parent(do_QueryInterface(parentAsItem));
+
+  const Encoding* reloadEncoding = nullptr;
+  int32_t reloadEncodingSource = kCharsetUninitialized;
+  // |newMUDV| also serves as a flag to set the data from the above vars
+  nsCOMPtr<nsIDocumentViewer> newViewer;
+
+  if (mDocumentViewer || parent) {
+    nsCOMPtr<nsIDocumentViewer> oldViewer;
+    if (mDocumentViewer) {
+      // Get any interesting state from old content viewer
+      // XXX: it would be far better to just reuse the document viewer ,
+      //      since we know we're just displaying the same document as before
+      oldViewer = mDocumentViewer;
+
+      // Tell the old content viewer to hibernate in session history when
+      // it is destroyed.
+
+      if (mSavingOldViewer && NS_FAILED(CaptureState())) {
+        if (mOSHE) {
+          mOSHE->SyncPresentationState();
+        }
+        mSavingOldViewer = false;
+      }
+    } else {
+      // No old content viewer, so get state from parent's content viewer
+      parent->GetDocViewer(getter_AddRefs(oldViewer));
+    }
+
+    if (oldViewer) {
+      newViewer = aNewViewer;
+      if (newViewer) {
+        reloadEncoding =
+            oldViewer->GetReloadEncodingAndSource(&reloadEncodingSource);
+      }
+    }
+  }
+
+  nscolor bgcolor = NS_RGBA(0, 0, 0, 0);
+  bool isUnderHiddenEmbedderElement = false;
+  // Ensure that the content viewer is destroyed *after* the GC - bug 71515
+  nsCOMPtr<nsIDocumentViewer> viewer = mDocumentViewer;
+  if (viewer) {
+    // Stop any activity that may be happening in the old document before
+    // releasing it...
+    viewer->Stop();
+
+    // Try to extract the canvas background color from the old
+    // presentation shell, so we can use it for the next document.
+    if (PresShell* presShell = viewer->GetPresShell()) {
+      bgcolor = presShell->GetCanvasBackground();
+      isUnderHiddenEmbedderElement = presShell->IsUnderHiddenEmbedderElement();
+    }
+
+    viewer->Close(mSavingOldViewer ? mOSHE.get() : nullptr);
+    aNewViewer->SetPreviousViewer(viewer);
+  }
+  if (mOSHE && (!mDocumentViewer || !mSavingOldViewer)) {
+    // We don't plan to save a viewer in mOSHE; tell it to drop
+    // any other state it's holding.
+    mOSHE->SyncPresentationState();
+  }
+
+  mDocumentViewer = nullptr;
+
+  // Now that we're about to switch documents, forget all of our children.
+  // Note that we cached them as needed up in CaptureState above.
+  DestroyChildren();
+
+  mDocumentViewer = aNewViewer;
+
+  nsCOMPtr<nsIWidget> widget;
+  NS_ENSURE_SUCCESS(GetMainWidget(getter_AddRefs(widget)), NS_ERROR_FAILURE);
+
+  nsIntRect bounds(x, y, cx, cy);
+
+  mDocumentViewer->SetNavigationTiming(mTiming);
+
+  if (NS_FAILED(mDocumentViewer->Init(widget, bounds, aWindowActor))) {
+    nsCOMPtr<nsIDocumentViewer> viewer = mDocumentViewer;
+    viewer->Close(nullptr);
+    viewer->Destroy();
+    mDocumentViewer = nullptr;
+    SetCurrentURIInternal(nullptr);
+    NS_WARNING("ContentViewer Initialization failed");
+    return NS_ERROR_FAILURE;
+  }
+
+  // If we have old state to copy, set the old state onto the new content
+  // viewer
+  if (newViewer) {
+    newViewer->SetReloadEncodingAndSource(reloadEncoding, reloadEncodingSource);
+  }
+
+  NS_ENSURE_TRUE(mDocumentViewer, NS_ERROR_FAILURE);
+
+  // Stuff the bgcolor from the old pres shell into the new
+  // pres shell. This improves page load continuity.
+  if (RefPtr<PresShell> presShell = mDocumentViewer->GetPresShell()) {
+    presShell->SetCanvasBackground(bgcolor);
+    presShell->ActivenessMaybeChanged();
+    if (isUnderHiddenEmbedderElement) {
+      presShell->SetIsUnderHiddenEmbedderElement(isUnderHiddenEmbedderElement);
+    }
+  }
+
+  // XXX: It looks like the LayoutState gets restored again in Embed()
+  //      right after the call to SetupNewViewer(...)
+
+  // We don't show the mDocumentViewer yet, since we want to draw the old page
+  // until we have enough of the new page to show.  Just return with the new
+  // viewer still set to hidden.
+
+  return NS_OK;
+}
+
+void nsDocShell::SetDocCurrentStateObj(nsISHEntry* aShEntry,
+                                       SessionHistoryInfo* aInfo) {
+  NS_ENSURE_TRUE_VOID(mDocumentViewer);
+
+  RefPtr<Document> document = GetDocument();
+  NS_ENSURE_TRUE_VOID(document);
+
+  nsCOMPtr<nsIStructuredCloneContainer> scContainer;
+  if (mozilla::SessionHistoryInParent()) {
+    // If aInfo is null, just set the document's state object to null.
+    if (aInfo) {
+      scContainer = aInfo->GetStateData();
+    }
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("nsDocShell %p SetCurrentDocState %p", this, scContainer.get()));
+  } else {
+    if (aShEntry) {
+      scContainer = aShEntry->GetStateData();
+
+      // If aShEntry is null, just set the document's state object to null.
+    }
+  }
+
+  // It's OK for scContainer too be null here; that just means there's no
+  // state data associated with this history entry.
+  document->SetStateObject(scContainer);
+}
+
+nsresult nsDocShell::CheckLoadingPermissions() {
+  // This method checks whether the caller may load content into
+  // this docshell. Even though we've done our best to hide windows
+  // from code that doesn't have the right to access them, it's
+  // still possible for an evil site to open a window and access
+  // frames in the new window through window.frames[] (which is
+  // allAccess for historic reasons), so we still need to do this
+  // check on load.
+  nsresult rv = NS_OK;
+
+  if (!IsSubframe()) {
+    // We're not a frame. Permit all loads.
+    return rv;
+  }
+
+  // Note - The check for a current JSContext here isn't necessarily sensical.
+  // It's just designed to preserve the old semantics during a mass-conversion
+  // patch.
+  if (!nsContentUtils::GetCurrentJSContext()) {
+    return NS_OK;
+  }
+
+  // Check if the caller is from the same origin as this docshell,
+  // or any of its ancestors.
+  for (RefPtr<BrowsingContext> bc = mBrowsingContext; bc;
+       bc = bc->GetParent()) {
+    // If the BrowsingContext is not in process, then it
+    // is true by construction that its principal will not
+    // subsume the current docshell principal.
+    if (!bc->IsInProcess()) {
+      continue;
+    }
+
+    nsCOMPtr<nsIScriptGlobalObject> sgo =
+        bc->GetDocShell()->GetScriptGlobalObject();
+    nsCOMPtr<nsIScriptObjectPrincipal> sop(do_QueryInterface(sgo));
+
+    nsIPrincipal* p;
+    if (!sop || !(p = sop->GetPrincipal())) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    if (nsContentUtils::SubjectPrincipal()->Subsumes(p)) {
+      // Same origin, permit load
+      return NS_OK;
+    }
+  }
+
+  return NS_ERROR_DOM_PROP_ACCESS_DENIED;
+}
+
+//*****************************************************************************
+// nsDocShell: Site Loading
+//*****************************************************************************
+
+void nsDocShell::CopyFavicon(nsIURI* aOldURI, nsIURI* aNewURI,
+                             bool aInPrivateBrowsing) {
+  if (XRE_IsContentProcess()) {
+    dom::ContentChild* contentChild = dom::ContentChild::GetSingleton();
+    if (contentChild) {
+      contentChild->SendCopyFavicon(aOldURI, aNewURI, aInPrivateBrowsing);
+    }
+    return;
+  }
+
+#ifdef MOZ_PLACES
+  nsCOMPtr<nsIFaviconService> favSvc =
+      do_GetService("@mozilla.org/browser/favicon-service;1");
+  if (favSvc) {
+    favSvc->CopyFavicons(aOldURI, aNewURI,
+                         aInPrivateBrowsing
+                             ? nsIFaviconService::FAVICON_LOAD_PRIVATE
+                             : nsIFaviconService::FAVICON_LOAD_NON_PRIVATE,
+                         nullptr);
+  }
+#endif
+}
+
+class InternalLoadEvent : public Runnable {
+ public:
+  InternalLoadEvent(nsDocShell* aDocShell, nsDocShellLoadState* aLoadState)
+      : mozilla::Runnable("InternalLoadEvent"),
+        mDocShell(aDocShell),
+        mLoadState(aLoadState) {
+    // For events, both target and filename should be the version of "null" they
+    // expect. By the time the event is fired, both window targeting and file
+    // downloading have been handled, so we should never have an internal load
+    // event that retargets or had a download.
+    mLoadState->SetTarget(u""_ns);
+    mLoadState->SetFileName(VoidString());
+  }
+
+  NS_IMETHOD
+  Run() override {
+#ifndef ANDROID
+    MOZ_ASSERT(mLoadState->TriggeringPrincipal(),
+               "InternalLoadEvent: Should always have a principal here");
+#endif
+    return mDocShell->InternalLoad(mLoadState);
+  }
+
+ private:
+  RefPtr<nsDocShell> mDocShell;
+  RefPtr<nsDocShellLoadState> mLoadState;
+};
+
+/**
+ * Returns true if we started an asynchronous load (i.e., from the network), but
+ * the document we're loading there hasn't yet become this docshell's active
+ * document.
+ *
+ * When JustStartedNetworkLoad is true, you should be careful about modifying
+ * mLoadType and mLSHE.  These are both set when the asynchronous load first
+ * starts, and the load expects that, when it eventually runs InternalLoad,
+ * mLoadType and mLSHE will have their original values.
+ */
+bool nsDocShell::JustStartedNetworkLoad() {
+  return mDocumentRequest && mDocumentRequest != GetCurrentDocChannel();
+}
+
+// The contentType will be INTERNAL_(I)FRAME if this docshell is for a
+// non-toplevel browsing context in spec terms. (frame, iframe, <object>,
+// <embed>, etc)
+//
+// This return value will be used when we call NS_CheckContentLoadPolicy, and
+// later when we call DoURILoad.
+nsContentPolicyType nsDocShell::DetermineContentType() {
+  if (!IsSubframe()) {
+    return nsIContentPolicy::TYPE_DOCUMENT;
+  }
+
+  const auto& maybeEmbedderElementType =
+      GetBrowsingContext()->GetEmbedderElementType();
+  if (!maybeEmbedderElementType) {
+    // If the EmbedderElementType hasn't been set yet, just assume we're
+    // an iframe since that's more common.
+    return nsIContentPolicy::TYPE_INTERNAL_IFRAME;
+  }
+
+  return maybeEmbedderElementType->EqualsLiteral("iframe")
+             ? nsIContentPolicy::TYPE_INTERNAL_IFRAME
+             : nsIContentPolicy::TYPE_INTERNAL_FRAME;
+}
+
+bool nsDocShell::NoopenerForceEnabled() {
+  // If current's top-level browsing context's active document's
+  // cross-origin-opener-policy is "same-origin" or "same-origin + COEP" then
+  // if currentDoc's origin is not same origin with currentDoc's top-level
+  // origin, noopener is force enabled, and name is cleared to "_blank".
+  auto topPolicy = mBrowsingContext->Top()->GetOpenerPolicy();
+  return (topPolicy == nsILoadInfo::OPENER_POLICY_SAME_ORIGIN ||
+          topPolicy ==
+              nsILoadInfo::
+                  OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP) &&
+         !mBrowsingContext->SameOriginWithTop();
+}
+
+nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState) {
+  MOZ_ASSERT(aLoadState, "need a load state!");
+  MOZ_ASSERT(!aLoadState->Target().IsEmpty(), "should have a target here!");
+  MOZ_ASSERT(aLoadState->TargetBrowsingContext().IsNull(),
+             "should not have picked target yet");
+
+  nsresult rv = NS_OK;
+  RefPtr<BrowsingContext> targetContext;
+
+  // Only _self, _parent, and _top are supported in noopener case.  But we
+  // have to be careful to not apply that to the noreferrer case.  See bug
+  // 1358469.
+  bool allowNamedTarget =
+      !aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_NO_OPENER) ||
+      aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER);
+  if (allowNamedTarget ||
+      aLoadState->Target().LowerCaseEqualsLiteral("_self") ||
+      aLoadState->Target().LowerCaseEqualsLiteral("_parent") ||
+      aLoadState->Target().LowerCaseEqualsLiteral("_top")) {
+    Document* document = GetDocument();
+    NS_ENSURE_TRUE(document, NS_ERROR_FAILURE);
+    WindowGlobalChild* wgc = document->GetWindowGlobalChild();
+    NS_ENSURE_TRUE(wgc, NS_ERROR_FAILURE);
+    targetContext = wgc->FindBrowsingContextWithName(
+        aLoadState->Target(), /* aUseEntryGlobalForAccessCheck */ false);
+  }
+
+  if (!targetContext) {
+    // If the targetContext doesn't exist, then this is a new docShell and we
+    // should consider this a TYPE_DOCUMENT load
+    //
+    // For example, when target="_blank"
+
+    // If there's no targetContext, that means we are about to create a new
+    // window. Perform a content policy check before creating the window. Please
+    // note for all other docshell loads content policy checks are performed
+    // within the contentSecurityManager when the channel is about to be
+    // openend.
+    nsISupports* requestingContext = nullptr;
+    if (XRE_IsContentProcess()) {
+      // In e10s the child process doesn't have access to the element that
+      // contains the browsing context (because that element is in the chrome
+      // process). So we just pass mScriptGlobal.
+      requestingContext = ToSupports(mScriptGlobal);
+    } else {
+      // This is for loading non-e10s tabs and toplevel windows of various
+      // sorts.
+      // For the toplevel window cases, requestingElement will be null.
+      nsCOMPtr<Element> requestingElement =
+          mScriptGlobal->GetFrameElementInternal();
+      requestingContext = requestingElement;
+    }
+
+    // Ideally we should use the same loadinfo as within DoURILoad which
+    // should match this one when both are applicable.
+    nsCOMPtr<nsILoadInfo> secCheckLoadInfo =
+        new LoadInfo(mScriptGlobal, aLoadState->URI(),
+                     aLoadState->TriggeringPrincipal(), requestingContext,
+                     nsILoadInfo::SEC_ONLY_FOR_EXPLICIT_CONTENTSEC_CHECK, 0);
+
+    // Since Content Policy checks are performed within docShell as well as
+    // the ContentSecurityManager we need a reliable way to let certain
+    // nsIContentPolicy consumers ignore duplicate calls.
+    secCheckLoadInfo->SetSkipContentPolicyCheckForWebRequest(true);
+
+    int16_t shouldLoad = nsIContentPolicy::ACCEPT;
+    rv = NS_CheckContentLoadPolicy(aLoadState->URI(), secCheckLoadInfo,
+                                   &shouldLoad);
+
+    if (NS_FAILED(rv) || NS_CP_REJECTED(shouldLoad)) {
+      if (NS_SUCCEEDED(rv)) {
+        if (shouldLoad == nsIContentPolicy::REJECT_TYPE) {
+          return NS_ERROR_CONTENT_BLOCKED_SHOW_ALT;
+        }
+        if (shouldLoad == nsIContentPolicy::REJECT_POLICY) {
+          return NS_ERROR_BLOCKED_BY_POLICY;
+        }
+      }
+
+      return NS_ERROR_CONTENT_BLOCKED;
+    }
+  }
+
+  //
+  // Resolve the window target before going any further...
+  // If the load has been targeted to another DocShell, then transfer the
+  // load to it...
+  //
+
+  // We've already done our owner-inheriting.  Mask out that bit, so we
+  // don't try inheriting an owner from the target window if we came up
+  // with a null owner above.
+  aLoadState->UnsetInternalLoadFlag(INTERNAL_LOAD_FLAGS_INHERIT_PRINCIPAL);
+
+  if (!targetContext) {
+    // If the docshell's document is sandboxed, only open a new window
+    // if the document's SANDBOXED_AUXILLARY_NAVIGATION flag is not set.
+    // (i.e. if allow-popups is specified)
+    NS_ENSURE_TRUE(mDocumentViewer, NS_ERROR_FAILURE);
+    Document* doc = mDocumentViewer->GetDocument();
+
+    const bool isDocumentAuxSandboxed =
+        doc && (doc->GetSandboxFlags() & SANDBOXED_AUXILIARY_NAVIGATION);
+
+    if (isDocumentAuxSandboxed) {
+      return NS_ERROR_DOM_INVALID_ACCESS_ERR;
+    }
+
+    nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
+    NS_ENSURE_TRUE(win, NS_ERROR_NOT_AVAILABLE);
+
+    RefPtr<BrowsingContext> newBC;
+    nsAutoCString spec;
+    aLoadState->URI()->GetSpec(spec);
+
+    // If we are a noopener load, we just hand the whole thing over to our
+    // window.
+    if (aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_NO_OPENER) ||
+        NoopenerForceEnabled()) {
+      // Various asserts that we know to hold because NO_OPENER loads can only
+      // happen for links.
+      MOZ_ASSERT(!aLoadState->LoadReplace());
+      MOZ_ASSERT(aLoadState->PrincipalToInherit() ==
+                 aLoadState->TriggeringPrincipal());
+      MOZ_ASSERT(!(aLoadState->InternalLoadFlags() &
+                   ~(INTERNAL_LOAD_FLAGS_NO_OPENER |
+                     INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER)),
+                 "Only INTERNAL_LOAD_FLAGS_NO_OPENER and "
+                 "INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER can be set");
+      MOZ_ASSERT_IF(aLoadState->PostDataStream(),
+                    aLoadState->IsFormSubmission());
+      MOZ_ASSERT(!aLoadState->HeadersStream());
+      // If OnLinkClickSync was invoked inside the onload handler, the load
+      // type would be set to LOAD_NORMAL_REPLACE; otherwise it should be
+      // LOAD_LINK.
+      MOZ_ASSERT(aLoadState->LoadType() == LOAD_LINK ||
+                 aLoadState->LoadType() == LOAD_NORMAL_REPLACE);
+      MOZ_ASSERT(!aLoadState->LoadIsFromSessionHistory());
+      MOZ_ASSERT(aLoadState->FirstParty());  // Windowwatcher will assume this.
+
+      RefPtr<nsDocShellLoadState> loadState =
+          new nsDocShellLoadState(aLoadState->URI());
+
+      // Set up our loadinfo so it will do the load as much like we would have
+      // as possible.
+      loadState->SetReferrerInfo(aLoadState->GetReferrerInfo());
+      loadState->SetOriginalURI(aLoadState->OriginalURI());
+
+      Maybe<nsCOMPtr<nsIURI>> resultPrincipalURI;
+      aLoadState->GetMaybeResultPrincipalURI(resultPrincipalURI);
+
+      loadState->SetMaybeResultPrincipalURI(resultPrincipalURI);
+      loadState->SetKeepResultPrincipalURIIfSet(
+          aLoadState->KeepResultPrincipalURIIfSet());
+      // LoadReplace will always be false due to asserts above, skip setting
+      // it.
+      loadState->SetTriggeringPrincipal(aLoadState->TriggeringPrincipal());
+      loadState->SetTriggeringSandboxFlags(
+          aLoadState->TriggeringSandboxFlags());
+      loadState->SetTriggeringWindowId(aLoadState->TriggeringWindowId());
+      loadState->SetTriggeringStorageAccess(
+          aLoadState->TriggeringStorageAccess());
+      loadState->SetCsp(aLoadState->Csp());
+      loadState->SetInheritPrincipal(aLoadState->HasInternalLoadFlags(
+          INTERNAL_LOAD_FLAGS_INHERIT_PRINCIPAL));
+      // Explicit principal because we do not want any guesses as to what the
+      // principal to inherit is: it should be aTriggeringPrincipal.
+      loadState->SetPrincipalIsExplicit(true);
+      loadState->SetLoadType(aLoadState->LoadType());
+      loadState->SetForceAllowDataURI(aLoadState->HasInternalLoadFlags(
+          INTERNAL_LOAD_FLAGS_FORCE_ALLOW_DATA_URI));
+
+      loadState->SetHasValidUserGestureActivation(
+          aLoadState->HasValidUserGestureActivation());
+
+      // Propagate POST data to the new load.
+      loadState->SetPostDataStream(aLoadState->PostDataStream());
+      loadState->SetIsFormSubmission(aLoadState->IsFormSubmission());
+
+      rv = win->Open(NS_ConvertUTF8toUTF16(spec),
+                     aLoadState->Target(),  // window name
+                     u""_ns,                // Features
+                     loadState,
+                     true,  // aForceNoOpener
+                     getter_AddRefs(newBC));
+      MOZ_ASSERT(!newBC);
+      return rv;
+    }
+
+    rv = win->OpenNoNavigate(NS_ConvertUTF8toUTF16(spec),
+                             aLoadState->Target(),  // window name
+                             u""_ns,                // Features
+                             getter_AddRefs(newBC));
+
+    // In some cases the Open call doesn't actually result in a new
+    // window being opened.  We can detect these cases by examining the
+    // document in |newBC|, if any.
+    nsCOMPtr<nsPIDOMWindowOuter> piNewWin =
+        newBC ? newBC->GetDOMWindow() : nullptr;
+    if (piNewWin) {
+      RefPtr<Document> newDoc = piNewWin->GetExtantDoc();
+      if (!newDoc || newDoc->IsInitialDocument()) {
+        aLoadState->SetInternalLoadFlag(INTERNAL_LOAD_FLAGS_FIRST_LOAD);
+      }
+    }
+
+    if (newBC) {
+      targetContext = newBC;
+    }
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(targetContext, rv);
+
+  // If our target BrowsingContext is still pending initialization, ignore the
+  // navigation request targeting it.
+  if (NS_WARN_IF(targetContext->GetPendingInitialization())) {
+    return NS_OK;
+  }
+
+  aLoadState->SetTargetBrowsingContext(targetContext);
+  if (aLoadState->IsFormSubmission()) {
+    aLoadState->SetLoadType(
+        GetLoadTypeForFormSubmission(targetContext, aLoadState));
+  }
+
+  //
+  // Transfer the load to the target BrowsingContext... Clear the window target
+  // name to the empty string to prevent recursive retargeting!
+  //
+  // No window target
+  aLoadState->SetTarget(u""_ns);
+  // No forced download
+  aLoadState->SetFileName(VoidString());
+  return targetContext->InternalLoad(aLoadState);
+}
+
+static nsAutoCString RefMaybeNull(nsIURI* aURI) {
+  nsAutoCString result;
+  if (NS_FAILED(aURI->GetRef(result))) {
+    result.SetIsVoid(true);
+  }
+  return result;
+}
+
+uint32_t nsDocShell::GetSameDocumentNavigationFlags(nsIURI* aNewURI) {
+  uint32_t flags = LOCATION_CHANGE_SAME_DOCUMENT;
+
+  bool equal = false;
+  if (mCurrentURI &&
+      NS_SUCCEEDED(mCurrentURI->EqualsExceptRef(aNewURI, &equal)) && equal &&
+      RefMaybeNull(mCurrentURI) != RefMaybeNull(aNewURI)) {
+    flags |= LOCATION_CHANGE_HASHCHANGE;
+  }
+
+  return flags;
+}
+
+bool nsDocShell::IsSameDocumentNavigation(nsDocShellLoadState* aLoadState,
+                                          SameDocumentNavigationState& aState) {
+  MOZ_ASSERT(aLoadState);
+  if (!(aLoadState->LoadType() == LOAD_NORMAL ||
+        aLoadState->LoadType() == LOAD_STOP_CONTENT ||
+        LOAD_TYPE_HAS_FLAGS(aLoadState->LoadType(),
+                            LOAD_FLAGS_REPLACE_HISTORY) ||
+        aLoadState->LoadType() == LOAD_HISTORY ||
+        aLoadState->LoadType() == LOAD_LINK)) {
+    return false;
+  }
+
+  nsCOMPtr<nsIURI> currentURI = mCurrentURI;
+
+  nsresult rvURINew = aLoadState->URI()->GetRef(aState.mNewHash);
+  if (NS_SUCCEEDED(rvURINew)) {
+    rvURINew = aLoadState->URI()->GetHasRef(&aState.mNewURIHasRef);
+  }
+
+  if (currentURI && NS_SUCCEEDED(rvURINew)) {
+    nsresult rvURIOld = currentURI->GetRef(aState.mCurrentHash);
+    if (NS_SUCCEEDED(rvURIOld)) {
+      rvURIOld = currentURI->GetHasRef(&aState.mCurrentURIHasRef);
+    }
+    if (NS_SUCCEEDED(rvURIOld)) {
+      if (NS_FAILED(currentURI->EqualsExceptRef(aLoadState->URI(),
+                                                &aState.mSameExceptHashes))) {
+        aState.mSameExceptHashes = false;
+      }
+    }
+  }
+
+  if (!aState.mSameExceptHashes && currentURI && NS_SUCCEEDED(rvURINew)) {
+    // Maybe aLoadState->URI() came from the exposable form of currentURI?
+    nsCOMPtr<nsIURI> currentExposableURI =
+        nsIOService::CreateExposableURI(currentURI);
+    nsresult rvURIOld = currentExposableURI->GetRef(aState.mCurrentHash);
+    if (NS_SUCCEEDED(rvURIOld)) {
+      rvURIOld = currentExposableURI->GetHasRef(&aState.mCurrentURIHasRef);
+    }
+    if (NS_SUCCEEDED(rvURIOld)) {
+      if (NS_FAILED(currentExposableURI->EqualsExceptRef(
+              aLoadState->URI(), &aState.mSameExceptHashes))) {
+        aState.mSameExceptHashes = false;
+      }
+      // HTTPS-Only Mode upgrades schemes from http to https in Necko, hence we
+      // have to perform a special check here to avoid an actual navigation. If
+      // HTTPS-Only Mode is enabled and the two URIs are same-origin (modulo the
+      // fact that the new URI is currently http), then set mSameExceptHashes to
+      // true and only perform a fragment navigation.
+      if (!aState.mSameExceptHashes) {
+        if (nsCOMPtr<nsIChannel> docChannel = GetCurrentDocChannel()) {
+          nsCOMPtr<nsILoadInfo> docLoadInfo = docChannel->LoadInfo();
+          if (!docLoadInfo->GetLoadErrorPage() &&
+              nsHTTPSOnlyUtils::IsEqualURIExceptSchemeAndRef(
+                  currentExposableURI, aLoadState->URI(), docLoadInfo)) {
+            uint32_t status = docLoadInfo->GetHttpsOnlyStatus();
+            if (status & (nsILoadInfo::HTTPS_ONLY_UPGRADED_LISTENER_REGISTERED |
+                          nsILoadInfo::HTTPS_ONLY_UPGRADED_HTTPS_FIRST)) {
+              // At this point the requested URI is for sure a fragment
+              // navigation via HTTP and HTTPS-Only mode or HTTPS-First is
+              // enabled. Also it is not interfering the upgrade order of
+              // https://searchfox.org/mozilla-central/source/netwerk/base/nsNetUtil.cpp#2948-2953.
+              // Since we are on an HTTPS site the fragment
+              // navigation should also be an HTTPS.
+              // For that reason we should upgrade the URI to HTTPS.
+              aState.mSecureUpgradeURI = true;
+              aState.mSameExceptHashes = true;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  if (mozilla::SessionHistoryInParent()) {
+    if (mActiveEntry && aLoadState->LoadIsFromSessionHistory()) {
+      aState.mHistoryNavBetweenSameDoc = mActiveEntry->SharesDocumentWith(
+          aLoadState->GetLoadingSessionHistoryInfo()->mInfo);
+    }
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("nsDocShell::IsSameDocumentNavigation %p NavBetweenSameDoc=%d",
+             this, aState.mHistoryNavBetweenSameDoc));
+  } else {
+    if (mOSHE && aLoadState->LoadIsFromSessionHistory()) {
+      // We're doing a history load.
+
+      mOSHE->SharesDocumentWith(aLoadState->SHEntry(),
+                                &aState.mHistoryNavBetweenSameDoc);
+    }
+  }
+
+  // A same document navigation happens when we navigate between two SHEntries
+  // for the same document. We do a same document navigation under two
+  // circumstances. Either
+  //
+  //  a) we're navigating between two different SHEntries which share a
+  //     document, or
+  //
+  //  b) we're navigating to a new shentry whose URI differs from the
+  //     current URI only in its hash, the new hash is non-empty, and
+  //     we're not doing a POST.
+  //
+  // The restriction that the SHEntries in (a) must be different ensures
+  // that history.go(0) and the like trigger full refreshes, rather than
+  // same document navigations.
+  if (!mozilla::SessionHistoryInParent()) {
+    bool doSameDocumentNavigation =
+        (aState.mHistoryNavBetweenSameDoc && mOSHE != aLoadState->SHEntry()) ||
+        (!aLoadState->SHEntry() && !aLoadState->PostDataStream() &&
+         aState.mSameExceptHashes && aState.mNewURIHasRef);
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("nsDocShell %p NavBetweenSameDoc=%d is same doc = %d", this,
+             aState.mHistoryNavBetweenSameDoc, doSameDocumentNavigation));
+    return doSameDocumentNavigation;
+  }
+
+  if (aState.mHistoryNavBetweenSameDoc &&
+      !aLoadState->GetLoadingSessionHistoryInfo()->mLoadingCurrentEntry) {
+    return true;
+  }
+
+  MOZ_LOG(
+      gSHLog, LogLevel::Debug,
+      ("nsDocShell::IsSameDocumentNavigation %p !LoadIsFromSessionHistory=%s "
+       "!PostDataStream: %s mSameExceptHashes: %s mNewURIHasRef: %s",
+       this, !aLoadState->LoadIsFromSessionHistory() ? "true" : "false",
+       !aLoadState->PostDataStream() ? "true" : "false",
+       aState.mSameExceptHashes ? "true" : "false",
+       aState.mNewURIHasRef ? "true" : "false"));
+  return !aLoadState->LoadIsFromSessionHistory() &&
+         !aLoadState->PostDataStream() && aState.mSameExceptHashes &&
+         aState.mNewURIHasRef;
+}
+
+nsresult nsDocShell::HandleSameDocumentNavigation(
+    nsDocShellLoadState* aLoadState, SameDocumentNavigationState& aState,
+    bool& aSameDocument) {
+  aSameDocument = true;
+#ifdef DEBUG
+  SameDocumentNavigationState state;
+  MOZ_ASSERT(IsSameDocumentNavigation(aLoadState, state));
+#endif
+
+  MOZ_LOG(gSHLog, LogLevel::Debug,
+          ("nsDocShell::HandleSameDocumentNavigation %p %s -> %s", this,
+           mCurrentURI->GetSpecOrDefault().get(),
+           aLoadState->URI()->GetSpecOrDefault().get()));
+
+  RefPtr<Document> doc = GetDocument();
+  NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
+  doc->DoNotifyPossibleTitleChange();
+
+  nsCOMPtr<nsIURI> currentURI = mCurrentURI;
+
+  // We need to upgrade the new URI from http: to https:
+  nsCOMPtr<nsIURI> newURI = aLoadState->URI();
+  if (aState.mSecureUpgradeURI) {
+    MOZ_TRY(NS_GetSecureUpgradedURI(aLoadState->URI(), getter_AddRefs(newURI)));
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("Upgraded URI to %s", newURI->GetSpecOrDefault().get()));
+  }
+
+  if (StaticPrefs::dom_security_setdocumenturi()) {
+    // check if aLoadState->URI(), principalURI, mCurrentURI are same origin
+    // skip handling otherwise
+    nsCOMPtr<nsIPrincipal> origPrincipal = doc->NodePrincipal();
+    nsCOMPtr<nsIURI> principalURI = origPrincipal->GetURI();
+    if (origPrincipal->GetIsNullPrincipal()) {
+      nsCOMPtr<nsIPrincipal> precursor = origPrincipal->GetPrecursorPrincipal();
+      if (precursor) {
+        principalURI = precursor->GetURI();
+      }
+    }
+
+    auto isLoadableViaInternet = [](nsIURI* uri) {
+      return (uri && (net::SchemeIsHTTP(uri) || net::SchemeIsHTTPS(uri)));
+    };
+
+    if (isLoadableViaInternet(principalURI) &&
+        isLoadableViaInternet(mCurrentURI) && isLoadableViaInternet(newURI)) {
+      nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
+      if (!NS_SUCCEEDED(
+              ssm->CheckSameOriginURI(newURI, principalURI, false, false)) ||
+          !NS_SUCCEEDED(ssm->CheckSameOriginURI(mCurrentURI, principalURI,
+                                                false, false))) {
+        MOZ_LOG(gSHLog, LogLevel::Debug,
+                ("nsDocShell[%p]: possible violation of the same origin policy "
+                 "during same document navigation",
+                 this));
+        aSameDocument = false;
+        return NS_OK;
+      }
+    }
+  }
+
+#ifdef DEBUG
+  if (aState.mSameExceptHashes) {
+    bool sameExceptHashes = false;
+    currentURI->EqualsExceptRef(newURI, &sameExceptHashes);
+    MOZ_ASSERT(sameExceptHashes);
+  }
+#endif
+
+  // Save the position of the scrollers.
+  nsPoint scrollPos = GetCurScrollPos();
+
+  // Reset mLoadType to its original value once we exit this block, because this
+  // same document navigation might have started after a normal, network load,
+  // and we don't want to clobber its load type. See bug 737307.
+  AutoRestore<uint32_t> loadTypeResetter(mLoadType);
+
+  // If a non-same-document-navigation (i.e., a network load) is pending, make
+  // this a replacement load, so that we don't add a SHEntry here and the
+  // network load goes into the SHEntry it expects to.
+  if (JustStartedNetworkLoad() && (aLoadState->LoadType() & LOAD_CMD_NORMAL)) {
+    mLoadType = LOAD_NORMAL_REPLACE;
+  } else {
+    mLoadType = aLoadState->LoadType();
+  }
+
+  mURIResultedInDocument = true;
+
+  nsCOMPtr<nsISHEntry> oldLSHE = mLSHE;
+
+  // we need to assign aLoadState->SHEntry() to mLSHE right here, so that on
+  // History loads, SetCurrentURI() called from OnNewURI() will send proper
+  // onLocationChange() notifications to the browser to update back/forward
+  // buttons.
+  SetHistoryEntryAndUpdateBC(Some<nsISHEntry*>(aLoadState->SHEntry()),
+                             Nothing());
+  UniquePtr<mozilla::dom::LoadingSessionHistoryInfo> oldLoadingEntry;
+  mLoadingEntry.swap(oldLoadingEntry);
+  if (aLoadState->GetLoadingSessionHistoryInfo()) {
+    mLoadingEntry = MakeUnique<LoadingSessionHistoryInfo>(
+        *aLoadState->GetLoadingSessionHistoryInfo());
+    mNeedToReportActiveAfterLoadingBecomesActive = false;
+  }
+
+  // Set the doc's URI according to the new history entry's URI.
+  doc->SetDocumentURI(newURI);
+
+  /* This is a anchor traversal within the same page.
+   * call OnNewURI() so that, this traversal will be
+   * recorded in session and global history.
+   */
+  nsCOMPtr<nsIPrincipal> newURITriggeringPrincipal, newURIPrincipalToInherit,
+      newURIPartitionedPrincipalToInherit;
+  nsCOMPtr<nsIContentSecurityPolicy> newCsp;
+  if (mozilla::SessionHistoryInParent() ? !!mActiveEntry : !!mOSHE) {
+    if (mozilla::SessionHistoryInParent()) {
+      newURITriggeringPrincipal = mActiveEntry->GetTriggeringPrincipal();
+      newURIPrincipalToInherit = mActiveEntry->GetPrincipalToInherit();
+      newURIPartitionedPrincipalToInherit =
+          mActiveEntry->GetPartitionedPrincipalToInherit();
+      newCsp = mActiveEntry->GetCsp();
+    } else {
+      newURITriggeringPrincipal = mOSHE->GetTriggeringPrincipal();
+      newURIPrincipalToInherit = mOSHE->GetPrincipalToInherit();
+      newURIPartitionedPrincipalToInherit =
+          mOSHE->GetPartitionedPrincipalToInherit();
+      newCsp = mOSHE->GetCsp();
+    }
+  } else {
+    newURITriggeringPrincipal = aLoadState->TriggeringPrincipal();
+    newURIPrincipalToInherit = doc->NodePrincipal();
+    newURIPartitionedPrincipalToInherit = doc->PartitionedPrincipal();
+    newCsp = doc->GetCsp();
+  }
+
+  uint32_t locationChangeFlags = GetSameDocumentNavigationFlags(newURI);
+
+  // Pass true for aCloneSHChildren, since we're not
+  // changing documents here, so all of our subframes are
+  // still relevant to the new session history entry.
+  //
+  // It also makes OnNewURI(...) set LOCATION_CHANGE_SAME_DOCUMENT
+  // flag on firing onLocationChange(...).
+  // Anyway, aCloneSHChildren param is simply reflecting
+  // doSameDocumentNavigation in this scope.
+  //
+  // Note: we'll actually fire onLocationChange later, in order to preserve
+  // ordering of HistoryCommit() in the parent vs onLocationChange (bug
+  // 1668126)
+  bool locationChangeNeeded = OnNewURI(
+      newURI, nullptr, newURITriggeringPrincipal, newURIPrincipalToInherit,
+      newURIPartitionedPrincipalToInherit, newCsp, true, true);
+
+  nsCOMPtr<nsIInputStream> postData;
+  nsCOMPtr<nsIReferrerInfo> referrerInfo;
+  uint32_t cacheKey = 0;
+
+  bool scrollRestorationIsManual = false;
+  if (!mozilla::SessionHistoryInParent()) {
+    if (mOSHE) {
+      /* save current position of scroller(s) (bug 59774) */
+      mOSHE->SetScrollPosition(scrollPos.x, scrollPos.y);
+      scrollRestorationIsManual = mOSHE->GetScrollRestorationIsManual();
+      // Get the postdata, page ident and referrer info from the current page,
+      // if the new load is being done via normal means.  Note that "normal
+      // means" can be checked for just by checking for LOAD_CMD_NORMAL, given
+      // the loadType and allowScroll check above -- it filters out some
+      // LOAD_CMD_NORMAL cases that we wouldn't want here.
+      if (aLoadState->LoadType() & LOAD_CMD_NORMAL) {
+        postData = mOSHE->GetPostData();
+        cacheKey = mOSHE->GetCacheKey();
+        referrerInfo = mOSHE->GetReferrerInfo();
+      }
+
+      // Link our new SHEntry to the old SHEntry's back/forward
+      // cache data, since the two SHEntries correspond to the
+      // same document.
+      if (mLSHE) {
+        if (!aLoadState->LoadIsFromSessionHistory()) {
+          // If we're not doing a history load, scroll restoration
+          // should be inherited from the previous session history entry.
+          SetScrollRestorationIsManualOnHistoryEntry(mLSHE,
+                                                     scrollRestorationIsManual);
+        }
+        mLSHE->AdoptBFCacheEntry(mOSHE);
+      }
+    }
+  } else {
+    if (mActiveEntry) {
+      mActiveEntry->SetScrollPosition(scrollPos.x, scrollPos.y);
+      if (mBrowsingContext) {
+        CollectWireframe();
+        if (XRE_IsParentProcess()) {
+          SessionHistoryEntry* entry =
+              mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+          if (entry) {
+            entry->SetScrollPosition(scrollPos.x, scrollPos.y);
+          }
+        } else {
+          mozilla::Unused << ContentChild::GetSingleton()
+                                 ->SendSessionHistoryEntryScrollPosition(
+                                     mBrowsingContext, scrollPos.x,
+                                     scrollPos.y);
+        }
+      }
+    }
+    if (mLoadingEntry) {
+      if (!mLoadingEntry->mLoadIsFromSessionHistory) {
+        // If we're not doing a history load, scroll restoration
+        // should be inherited from the previous session history entry.
+        // XXX This needs most probably tweaks once fragment navigation is
+        // fixed to work with session-history-in-parent.
+        SetScrollRestorationIsManualOnHistoryEntry(nullptr,
+                                                   scrollRestorationIsManual);
+      }
+    }
+  }
+
+  // If we're doing a history load, use its scroll restoration state.
+  if (aLoadState->LoadIsFromSessionHistory()) {
+    if (mozilla::SessionHistoryInParent()) {
+      scrollRestorationIsManual = aLoadState->GetLoadingSessionHistoryInfo()
+                                      ->mInfo.GetScrollRestorationIsManual();
+    } else {
+      scrollRestorationIsManual =
+          aLoadState->SHEntry()->GetScrollRestorationIsManual();
+    }
+  }
+
+  /* Assign mLSHE to mOSHE. This will either be a new entry created
+   * by OnNewURI() for normal loads or aLoadState->SHEntry() for history
+   * loads.
+   */
+  if (!mozilla::SessionHistoryInParent()) {
+    if (mLSHE) {
+      SetHistoryEntryAndUpdateBC(Nothing(), Some<nsISHEntry*>(mLSHE));
+      // Save the postData obtained from the previous page
+      // in to the session history entry created for the
+      // anchor page, so that any history load of the anchor
+      // page will restore the appropriate postData.
+      if (postData) {
+        mOSHE->SetPostData(postData);
+      }
+
+      // Make sure we won't just repost without hitting the
+      // cache first
+      if (cacheKey != 0) {
+        mOSHE->SetCacheKey(cacheKey);
+      }
+
+      // As the document has not changed, the referrer info hasn't changed too,
+      // so we can just copy it over.
+      if (referrerInfo) {
+        mOSHE->SetReferrerInfo(referrerInfo);
+      }
+    }
+
+    /* Set the title for the SH entry for this target url so that
+     * SH menus in go/back/forward buttons won't be empty for this.
+     * Note, this happens on mOSHE (and mActiveEntry in the future) because of
+     * the code above.
+     * Note, when session history lives in the parent process, this does not
+     * update the title there.
+     */
+    SetTitleOnHistoryEntry(false);
+  } else {
+    if (aLoadState->LoadIsFromSessionHistory()) {
+      MOZ_LOG(
+          gSHLog, LogLevel::Debug,
+          ("Moving the loading entry to the active entry on nsDocShell %p to "
+           "%s",
+           this, mLoadingEntry->mInfo.GetURI()->GetSpecOrDefault().get()));
+
+      nsCOMPtr<nsILayoutHistoryState> currentLayoutHistoryState;
+      if (mActiveEntry) {
+        currentLayoutHistoryState = mActiveEntry->GetLayoutHistoryState();
+      }
+
+      UniquePtr<SessionHistoryInfo> previousActiveEntry(mActiveEntry.release());
+      mActiveEntry = MakeUnique<SessionHistoryInfo>(mLoadingEntry->mInfo);
+      if (currentLayoutHistoryState) {
+        // Restore the existing nsILayoutHistoryState object, since it is
+        // possibly being used by the layout. When doing a new load, the
+        // shared state is copied from the existing active entry, so this
+        // special case is needed only with the history loads.
+        mActiveEntry->SetLayoutHistoryState(currentLayoutHistoryState);
+      }
+
+      if (cacheKey != 0) {
+        mActiveEntry->SetCacheKey(cacheKey);
+      }
+      // We're passing in mCurrentURI, which could be null. SessionHistoryCommit
+      // does require a non-null uri if this is for a refresh load of the same
+      // URI, but in that case mCurrentURI won't be null here.
+      mBrowsingContext->SessionHistoryCommit(
+          *mLoadingEntry, mLoadType, mCurrentURI, previousActiveEntry.get(),
+          true, true,
+          /* No expiration update on the same document loads*/
+          false, cacheKey);
+      // FIXME Need to set postdata.
+
+      // Set the title for the SH entry for this target url so that
+      // SH menus in go/back/forward buttons won't be empty for this.
+      // Note, when session history lives in the parent process, this does not
+      // update the title there.
+      SetTitleOnHistoryEntry(false);
+    } else {
+      Maybe<bool> scrollRestorationIsManual;
+      if (mActiveEntry) {
+        scrollRestorationIsManual.emplace(
+            mActiveEntry->GetScrollRestorationIsManual());
+
+        // Get the postdata, page ident and referrer info from the current page,
+        // if the new load is being done via normal means.  Note that "normal
+        // means" can be checked for just by checking for LOAD_CMD_NORMAL, given
+        // the loadType and allowScroll check above -- it filters out some
+        // LOAD_CMD_NORMAL cases that we wouldn't want here.
+        if (aLoadState->LoadType() & LOAD_CMD_NORMAL) {
+          postData = mActiveEntry->GetPostData();
+          cacheKey = mActiveEntry->GetCacheKey();
+          referrerInfo = mActiveEntry->GetReferrerInfo();
+        }
+      }
+
+      MOZ_LOG(gSHLog, LogLevel::Debug,
+              ("Creating an active entry on nsDocShell %p to %s", this,
+               newURI->GetSpecOrDefault().get()));
+      if (mActiveEntry) {
+        mActiveEntry = MakeUnique<SessionHistoryInfo>(*mActiveEntry, newURI);
+      } else {
+        mActiveEntry = MakeUnique<SessionHistoryInfo>(
+            newURI, newURITriggeringPrincipal, newURIPrincipalToInherit,
+            newURIPartitionedPrincipalToInherit, newCsp, mContentTypeHint);
+      }
+
+      // Save the postData obtained from the previous page in to the session
+      // history entry created for the anchor page, so that any history load of
+      // the anchor page will restore the appropriate postData.
+      if (postData) {
+        mActiveEntry->SetPostData(postData);
+      }
+
+      // Make sure we won't just repost without hitting the
+      // cache first
+      if (cacheKey != 0) {
+        mActiveEntry->SetCacheKey(cacheKey);
+      }
+
+      // As the document has not changed, the referrer info hasn't changed too,
+      // so we can just copy it over.
+      if (referrerInfo) {
+        mActiveEntry->SetReferrerInfo(referrerInfo);
+      }
+
+      // Set the title for the SH entry for this target url so that
+      // SH menus in go/back/forward buttons won't be empty for this.
+      mActiveEntry->SetTitle(mTitle);
+
+      if (scrollRestorationIsManual.isSome()) {
+        mActiveEntry->SetScrollRestorationIsManual(
+            scrollRestorationIsManual.value());
+      }
+
+      if (LOAD_TYPE_HAS_FLAGS(mLoadType, LOAD_FLAGS_REPLACE_HISTORY)) {
+        mBrowsingContext->ReplaceActiveSessionHistoryEntry(mActiveEntry.get());
+      } else {
+        mBrowsingContext->IncrementHistoryEntryCountForBrowsingContext();
+        // FIXME We should probably just compute mChildOffset in the parent
+        //       instead of passing it over IPC here.
+        mBrowsingContext->SetActiveSessionHistoryEntry(
+            Some(scrollPos), mActiveEntry.get(), mLoadType, cacheKey);
+        // FIXME Do we need to update mPreviousEntryIndex and mLoadedEntryIndex?
+      }
+    }
+  }
+
+  if (locationChangeNeeded) {
+    FireOnLocationChange(this, nullptr, newURI, locationChangeFlags);
+  }
+
+  /* Restore the original LSHE if we were loading something
+   * while same document navigation was initiated.
+   */
+  SetHistoryEntryAndUpdateBC(Some<nsISHEntry*>(oldLSHE), Nothing());
+  mLoadingEntry.swap(oldLoadingEntry);
+
+  /* Set the title for the Global History entry for this anchor url.
+   */
+  UpdateGlobalHistoryTitle(newURI);
+
+  SetDocCurrentStateObj(mOSHE, mActiveEntry.get());
+
+  // Inform the favicon service that the favicon for oldURI also
+  // applies to newURI.
+  CopyFavicon(currentURI, newURI, UsePrivateBrowsing());
+
+  RefPtr<nsGlobalWindowOuter> scriptGlobal = mScriptGlobal;
+  nsCOMPtr<nsPIDOMWindowInner> win =
+      scriptGlobal ? scriptGlobal->GetCurrentInnerWindow() : nullptr;
+
+  // ScrollToAnchor doesn't necessarily cause us to scroll the window;
+  // the function decides whether a scroll is appropriate based on the
+  // arguments it receives.  But even if we don't end up scrolling,
+  // ScrollToAnchor performs other important tasks, such as informing
+  // the presShell that we have a new hash.  See bug 680257.
+  nsresult rv = ScrollToAnchor(aState.mCurrentURIHasRef, aState.mNewURIHasRef,
+                               aState.mNewHash, aLoadState->LoadType());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  /* restore previous position of scroller(s), if we're moving
+   * back in history (bug 59774)
+   */
+  nscoord bx = 0;
+  nscoord by = 0;
+  bool needsScrollPosUpdate = false;
+  if ((mozilla::SessionHistoryInParent() ? !!mActiveEntry : !!mOSHE) &&
+      (aLoadState->LoadType() == LOAD_HISTORY ||
+       aLoadState->LoadType() == LOAD_RELOAD_NORMAL) &&
+      !scrollRestorationIsManual) {
+    needsScrollPosUpdate = true;
+    if (mozilla::SessionHistoryInParent()) {
+      mActiveEntry->GetScrollPosition(&bx, &by);
+    } else {
+      mOSHE->GetScrollPosition(&bx, &by);
+    }
+  }
+
+  // Dispatch the popstate and hashchange events, as appropriate.
+  //
+  // The event dispatch below can cause us to re-enter script and
+  // destroy the docshell, nulling out mScriptGlobal. Hold a stack
+  // reference to avoid null derefs. See bug 914521.
+  if (win) {
+    // Fire a hashchange event URIs differ, and only in their hashes.
+    bool doHashchange = aState.mSameExceptHashes &&
+                        (aState.mCurrentURIHasRef != aState.mNewURIHasRef ||
+                         !aState.mCurrentHash.Equals(aState.mNewHash));
+
+    if (aState.mHistoryNavBetweenSameDoc || doHashchange) {
+      win->DispatchSyncPopState();
+    }
+
+    if (needsScrollPosUpdate && win->HasActiveDocument()) {
+      SetCurScrollPosEx(bx, by);
+    }
+
+    if (doHashchange) {
+      // Note that currentURI hasn't changed because it's on the
+      // stack, so we can just use it directly as the old URI.
+      win->DispatchAsyncHashchange(currentURI, newURI);
+    }
+  }
+
+  return NS_OK;
+}
+
+static bool NavigationShouldTakeFocus(nsDocShell* aDocShell,
+                                      nsDocShellLoadState* aLoadState) {
+  if (!aLoadState->AllowFocusMove()) {
+    return false;
+  }
+  if (!aLoadState->HasValidUserGestureActivation()) {
+    return false;
+  }
+  const auto& sourceBC = aLoadState->SourceBrowsingContext();
+  if (!sourceBC || !sourceBC->IsActive()) {
+    // If the navigation didn't come from a foreground tab, then we don't steal
+    // focus.
+    return false;
+  }
+  auto* bc = aDocShell->GetBrowsingContext();
+  if (sourceBC.get() == bc) {
+    // If it comes from the same tab / frame, don't steal focus either.
+    return false;
+  }
+  auto* fm = nsFocusManager::GetFocusManager();
+  if (fm && bc->IsActive() && fm->IsInActiveWindow(bc)) {
+    // If we're already on the foreground tab of the foreground window, then we
+    // don't need to do this. This helps to e.g. not steal focus from the
+    // browser chrome unnecessarily.
+    return false;
+  }
+  if (auto* doc = aDocShell->GetExtantDocument()) {
+    if (doc->IsInitialDocument()) {
+      // If we're the initial load for the browsing context, the browser
+      // chrome determines what to focus. This is important because the
+      // browser chrome may want to e.g focus the url-bar
+      return false;
+    }
+  }
+  // Take loadDivertedInBackground into account so the behavior would be the
+  // same as how the tab first opened.
+  return !Preferences::GetBool("browser.tabs.loadDivertedInBackground", false);
+}
+
+uint32_t nsDocShell::GetLoadTypeForFormSubmission(
+    BrowsingContext* aTargetBC, nsDocShellLoadState* aLoadState) {
+  MOZ_ASSERT(aLoadState->IsFormSubmission());
+
+  // https://html.spec.whatwg.org/#form-submission-algorithm
+  //  22. Let historyHandling be "push".
+  //  23. If form document equals targetNavigable's active document, and
+  //      form document has not yet completely loaded, then set
+  //      historyHandling to "replace".
+  return GetBrowsingContext() == aTargetBC && !mEODForCurrentDocument
+             ? LOAD_NORMAL_REPLACE
+             : LOAD_LINK;
+}
+
+nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
+                                  Maybe<uint32_t> aCacheKey) {
+  MOZ_ASSERT(aLoadState, "need a load state!");
+  MOZ_ASSERT(aLoadState->TriggeringPrincipal(),
+             "need a valid TriggeringPrincipal");
+
+  if (!aLoadState->TriggeringPrincipal()) {
+    MOZ_ASSERT(false, "InternalLoad needs a valid triggeringPrincipal");
+    return NS_ERROR_FAILURE;
+  }
+  if (NS_WARN_IF(mBrowsingContext->GetPendingInitialization())) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  const bool shouldTakeFocus = NavigationShouldTakeFocus(this, aLoadState);
+
+  mOriginalUriString.Truncate();
+
+  MOZ_LOG(gDocShellLeakLog, LogLevel::Debug,
+          ("DOCSHELL %p InternalLoad %s\n", this,
+           aLoadState->URI()->GetSpecOrDefault().get()));
+
+  NS_ENSURE_TRUE(IsValidLoadType(aLoadState->LoadType()), NS_ERROR_INVALID_ARG);
+
+  // Cancel loads coming from Docshells that are being destroyed.
+  if (mIsBeingDestroyed) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsresult rv = EnsureScriptEnvironment();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // If we have a target to move to, do that now.
+  if (!aLoadState->Target().IsEmpty()) {
+    return PerformRetargeting(aLoadState);
+  }
+
+  // This is the non-retargeting load path, we've already set the right loadtype
+  // for form submissions in nsDocShell::OnLinkClickSync.
+  if (aLoadState->TargetBrowsingContext().IsNull()) {
+    aLoadState->SetTargetBrowsingContext(GetBrowsingContext());
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(
+      aLoadState->TargetBrowsingContext() == GetBrowsingContext(),
+      "Load must be targeting this BrowsingContext");
+
+  MOZ_TRY(CheckDisallowedJavascriptLoad(aLoadState));
+
+  // If we don't have a target, we're loading into ourselves, and our load
+  // delegate may want to intercept that load.
+  SameDocumentNavigationState sameDocumentNavigationState;
+  bool sameDocument =
+      IsSameDocumentNavigation(aLoadState, sameDocumentNavigationState) &&
+      !aLoadState->GetPendingRedirectedChannel();
+
+  // Note: We do this check both here and in BrowsingContext::
+  // LoadURI/InternalLoad, since document-specific sandbox flags are only
+  // available in the process triggering the load, and we don't want the target
+  // process to have to trust the triggering process to do the appropriate
+  // checks for the BrowsingContext's sandbox flags.
+  MOZ_TRY(mBrowsingContext->CheckSandboxFlags(aLoadState));
+
+  NS_ENSURE_STATE(!HasUnloadedParent());
+
+  rv = CheckLoadingPermissions();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (mFiredUnloadEvent) {
+    if (IsOKToLoadURI(aLoadState->URI())) {
+      MOZ_ASSERT(aLoadState->Target().IsEmpty(),
+                 "Shouldn't have a window target here!");
+
+      // If this is a replace load, make whatever load triggered
+      // the unload event also a replace load, so we don't
+      // create extra history entries.
+      if (LOAD_TYPE_HAS_FLAGS(aLoadState->LoadType(),
+                              LOAD_FLAGS_REPLACE_HISTORY)) {
+        mLoadType = LOAD_NORMAL_REPLACE;
+      }
+
+      // Do this asynchronously
+      nsCOMPtr<nsIRunnable> ev = new InternalLoadEvent(this, aLoadState);
+      return Dispatch(ev.forget());
+    }
+
+    // Just ignore this load attempt
+    return NS_OK;
+  }
+
+  // If we are loading a URI that should inherit a security context (basically
+  // javascript: at this point), and the caller has said that principal
+  // inheritance is allowed, there are a few possible cases:
+  //
+  // 1) We are provided with the principal to inherit. In that case, we just use
+  //    it.
+  //
+  // 2) The load is coming from some other application. In this case we don't
+  //    want to inherit from whatever document we have loaded now, since the
+  //    load is unrelated to it.
+  //
+  // 3) It's a load from our application, but does not provide an explicit
+  //    principal to inherit. In that case, we want to inherit the principal of
+  //    our current document, or of our parent document (if any) if we don't
+  //    have a current document.
+  {
+    bool inherits;
+
+    if (!aLoadState->HasLoadFlags(LOAD_FLAGS_FROM_EXTERNAL) &&
+        !aLoadState->PrincipalToInherit() &&
+        (aLoadState->HasInternalLoadFlags(
+            INTERNAL_LOAD_FLAGS_INHERIT_PRINCIPAL)) &&
+        NS_SUCCEEDED(nsContentUtils::URIInheritsSecurityContext(
+            aLoadState->URI(), &inherits)) &&
+        inherits) {
+      aLoadState->SetPrincipalToInherit(GetInheritedPrincipal(true));
+    }
+    // If principalToInherit is still null (e.g. if some of the conditions of
+    // were not satisfied), then no inheritance of any sort will happen: the
+    // load will just get a principal based on the URI being loaded.
+  }
+
+  // If this docshell is owned by a frameloader, make sure to cancel
+  // possible frameloader initialization before loading a new page.
+  nsCOMPtr<nsIDocShellTreeItem> parent = GetInProcessParentDocshell();
+  if (parent) {
+    RefPtr<Document> doc = parent->GetDocument();
+    if (doc) {
+      doc->TryCancelFrameLoaderInitialization(this);
+    }
+  }
+
+  // Before going any further vet loads initiated by external programs.
+  if (aLoadState->HasLoadFlags(LOAD_FLAGS_FROM_EXTERNAL)) {
+    MOZ_DIAGNOSTIC_ASSERT(aLoadState->LoadType() == LOAD_NORMAL);
+
+    // Disallow external chrome: loads targetted at content windows
+    if (SchemeIsChrome(aLoadState->URI())) {
+      NS_WARNING("blocked external chrome: url -- use '--chrome' option");
+      return NS_ERROR_FAILURE;
+    }
+
+    // clear the decks to prevent context bleed-through (bug 298255)
+    rv = CreateAboutBlankDocumentViewer(nullptr, nullptr, nullptr, nullptr,
+                                        /* aIsInitialDocument */ false);
+    if (NS_FAILED(rv)) {
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  mAllowKeywordFixup = aLoadState->HasInternalLoadFlags(
+      INTERNAL_LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP);
+  mURIResultedInDocument = false;  // reset the clock...
+
+  // See if this is actually a load between two history entries for the same
+  // document. If the process fails, or if we successfully navigate within the
+  // same document, return.
+  if (sameDocument) {
+    nsresult rv = HandleSameDocumentNavigation(
+        aLoadState, sameDocumentNavigationState, sameDocument);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (shouldTakeFocus) {
+      mBrowsingContext->Focus(CallerType::System, IgnoreErrors());
+    }
+    if (sameDocument) {
+      return rv;
+    }
+  }
+
+  // mDocumentViewer->PermitUnload can destroy |this| docShell, which
+  // causes the next call of CanSavePresentation to crash.
+  // Hold onto |this| until we return, to prevent a crash from happening.
+  // (bug#331040)
+  nsCOMPtr<nsIDocShell> kungFuDeathGrip(this);
+
+  // Don't init timing for javascript:, since it generally doesn't
+  // actually start a load or anything.  If it does, we'll init
+  // timing then, from OnStateChange.
+
+  // XXXbz mTiming should know what channel it's for, so we don't
+  // need this hackery.
+  bool toBeReset = false;
+  bool isJavaScript = SchemeIsJavascript(aLoadState->URI());
+
+  if (!isJavaScript) {
+    toBeReset = MaybeInitTiming();
+  }
+  bool isNotDownload = aLoadState->FileName().IsVoid();
+  if (mTiming && isNotDownload) {
+    mTiming->NotifyBeforeUnload();
+  }
+  // Check if the page doesn't want to be unloaded. The javascript:
+  // protocol handler deals with this for javascript: URLs.
+  if (!isJavaScript && isNotDownload &&
+      !aLoadState->NotifiedBeforeUnloadListeners() && mDocumentViewer) {
+    bool okToUnload;
+
+    // Check if request is exempted from HTTPSOnlyMode and if https-first is
+    // enabled, if so it means:
+    //    * https-first failed to upgrade request to https
+    //    * we already asked for permission to unload and the user accepted
+    //      otherwise we wouldn't be here.
+    bool isPrivateWin = GetOriginAttributes().mPrivateBrowsingId > 0;
+    bool isHistoryOrReload = false;
+    uint32_t loadType = aLoadState->LoadType();
+
+    // Check if request is a reload.
+    if (loadType == LOAD_RELOAD_NORMAL ||
+        loadType == LOAD_RELOAD_BYPASS_CACHE ||
+        loadType == LOAD_RELOAD_BYPASS_PROXY ||
+        loadType == LOAD_RELOAD_BYPASS_PROXY_AND_CACHE ||
+        loadType == LOAD_HISTORY) {
+      isHistoryOrReload = true;
+    }
+
+    // If it isn't a reload, the request already failed to be upgraded and
+    // https-first is enabled then don't ask the user again for permission to
+    // unload and just unload.
+    if (!isHistoryOrReload && aLoadState->IsExemptFromHTTPSFirstMode() &&
+        nsHTTPSOnlyUtils::IsHttpsFirstModeEnabled(isPrivateWin)) {
+      rv = mDocumentViewer->PermitUnload(
+          nsIDocumentViewer::PermitUnloadAction::eDontPromptAndUnload,
+          &okToUnload);
+    } else {
+      rv = mDocumentViewer->PermitUnload(&okToUnload);
+    }
+
+    if (NS_SUCCEEDED(rv) && !okToUnload) {
+      // The user chose not to unload the page, interrupt the
+      // load.
+      MaybeResetInitTiming(toBeReset);
+      return NS_OK;
+    }
+  }
+
+  if (mTiming && isNotDownload) {
+    mTiming->NotifyUnloadAccepted(mCurrentURI);
+  }
+
+  // In e10s, in the parent process, we refuse to load anything other than
+  // "safe" resources that we ship or trust enough to give "special" URLs.
+  // Similar check will be performed by the ParentProcessDocumentChannel if in
+  // use.
+  if (XRE_IsE10sParentProcess() &&
+      !DocumentChannel::CanUseDocumentChannel(aLoadState->URI()) &&
+      !CanLoadInParentProcess(aLoadState->URI())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Whenever a top-level browsing context is navigated, the user agent MUST
+  // lock the orientation of the document to the document's default
+  // orientation. We don't explicitly check for a top-level browsing context
+  // here because orientation is only set on top-level browsing contexts.
+  if (mBrowsingContext->GetOrientationLock() != hal::ScreenOrientation::None) {
+    MOZ_ASSERT(mBrowsingContext->IsTop());
+    MOZ_ALWAYS_SUCCEEDS(
+        mBrowsingContext->SetOrientationLock(hal::ScreenOrientation::None));
+    if (mBrowsingContext->IsActive()) {
+      ScreenOrientation::UpdateActiveOrientationLock(
+          hal::ScreenOrientation::None);
+    }
+  }
+
+  // Check for saving the presentation here, before calling Stop().
+  // This is necessary so that we can catch any pending requests.
+  // Since the new request has not been created yet, we pass null for the
+  // new request parameter.
+  // Also pass nullptr for the document, since it doesn't affect the return
+  // value for our purposes here.
+  bool savePresentation =
+      CanSavePresentation(aLoadState->LoadType(), nullptr, nullptr,
+                          /* aReportBFCacheComboTelemetry */ true);
+
+  // nsDocShell::CanSavePresentation is for non-SHIP version only. Do a
+  // separate check for SHIP so that we know if there are ongoing requests
+  // before calling Stop() below.
+  if (mozilla::SessionHistoryInParent()) {
+    Document* document = GetDocument();
+    uint32_t flags = 0;
+    if (document && !document->CanSavePresentation(nullptr, flags, true)) {
+      // This forces some flags into the WindowGlobalParent's mBFCacheStatus,
+      // which we'll then use in CanonicalBrowsingContext::AllowedInBFCache,
+      // and in particular we'll store BFCacheStatus::REQUEST if needed.
+      // Also, we want to report all the flags to the parent process here (and
+      // not just BFCacheStatus::NOT_ALLOWED), so that it can update the
+      // telemetry data correctly.
+      document->DisallowBFCaching(flags);
+    }
+  }
+
+  // Don't stop current network activity for javascript: URL's since
+  // they might not result in any data, and thus nothing should be
+  // stopped in those cases. In the case where they do result in
+  // data, the javascript: URL channel takes care of stopping
+  // current network activity.
+  if (!isJavaScript && isNotDownload) {
+    // Stop any current network activity.
+    // Also stop content if this is a zombie doc. otherwise
+    // the onload will be delayed by other loads initiated in the
+    // background by the first document that
+    // didn't fully load before the next load was initiated.
+    // If not a zombie, don't stop content until data
+    // starts arriving from the new URI...
+
+    if ((mDocumentViewer && mDocumentViewer->GetPreviousViewer()) ||
+        LOAD_TYPE_HAS_FLAGS(aLoadState->LoadType(), LOAD_FLAGS_STOP_CONTENT)) {
+      rv = Stop(nsIWebNavigation::STOP_ALL);
+    } else {
+      rv = Stop(nsIWebNavigation::STOP_NETWORK);
+    }
+
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+
+  mLoadType = aLoadState->LoadType();
+
+  // aLoadState->SHEntry() should be assigned to mLSHE, only after Stop() has
+  // been called. But when loading an error page, do not clear the
+  // mLSHE for the real page.
+  if (mLoadType != LOAD_ERROR_PAGE) {
+    SetHistoryEntryAndUpdateBC(Some<nsISHEntry*>(aLoadState->SHEntry()),
+                               Nothing());
+    if (aLoadState->LoadIsFromSessionHistory() &&
+        !mozilla::SessionHistoryInParent()) {
+      // We're making history navigation or a reload. Make sure our history ID
+      // points to the same ID as SHEntry's docshell ID.
+      nsID historyID = {};
+      aLoadState->SHEntry()->GetDocshellID(historyID);
+
+      Unused << mBrowsingContext->SetHistoryID(historyID);
+    }
+  }
+
+  mSavingOldViewer = savePresentation;
+
+  // If we have a saved content viewer in history, restore and show it now.
+  if (aLoadState->LoadIsFromSessionHistory() &&
+      (mLoadType & LOAD_CMD_HISTORY)) {
+    // https://html.spec.whatwg.org/#history-traversal:
+    // To traverse the history
+    // "If entry has a different Document object than the current entry, then
+    // run the following substeps: Remove any tasks queued by the history
+    // traversal task source..."
+    // Same document object case was handled already above with
+    // HandleSameDocumentNavigation call.
+    RefPtr<ChildSHistory> shistory = GetRootSessionHistory();
+    if (shistory) {
+      shistory->RemovePendingHistoryNavigations();
+    }
+    if (!mozilla::SessionHistoryInParent()) {
+      // It's possible that the previous viewer of mDocumentViewer is the
+      // viewer that will end up in aLoadState->SHEntry() when it gets closed.
+      // If that's the case, we need to go ahead and force it into its shentry
+      // so we can restore it.
+      if (mDocumentViewer) {
+        nsCOMPtr<nsIDocumentViewer> prevViewer =
+            mDocumentViewer->GetPreviousViewer();
+        if (prevViewer) {
+#ifdef DEBUG
+          nsCOMPtr<nsIDocumentViewer> prevPrevViewer =
+              prevViewer->GetPreviousViewer();
+          NS_ASSERTION(!prevPrevViewer, "Should never have viewer chain here");
+#endif
+          nsCOMPtr<nsISHEntry> viewerEntry;
+          prevViewer->GetHistoryEntry(getter_AddRefs(viewerEntry));
+          if (viewerEntry == aLoadState->SHEntry()) {
+            // Make sure this viewer ends up in the right place
+            mDocumentViewer->SetPreviousViewer(nullptr);
+            prevViewer->Destroy();
+          }
+        }
+      }
+      nsCOMPtr<nsISHEntry> oldEntry = mOSHE;
+      bool restoring;
+      rv = RestorePresentation(aLoadState->SHEntry(), &restoring);
+      if (restoring) {
+        Telemetry::Accumulate(Telemetry::BFCACHE_PAGE_RESTORED, true);
+        return rv;
+      }
+      Telemetry::Accumulate(Telemetry::BFCACHE_PAGE_RESTORED, false);
+
+      // We failed to restore the presentation, so clean up.
+      // Both the old and new history entries could potentially be in
+      // an inconsistent state.
+      if (NS_FAILED(rv)) {
+        if (oldEntry) {
+          oldEntry->SyncPresentationState();
+        }
+
+        aLoadState->SHEntry()->SyncPresentationState();
+      }
+    }
+  }
+
+  bool isTopLevelDoc = mBrowsingContext->IsTopContent();
+
+  OriginAttributes attrs = GetOriginAttributes();
+  attrs.SetFirstPartyDomain(isTopLevelDoc, aLoadState->URI());
+
+  PredictorLearn(aLoadState->URI(), nullptr,
+                 nsINetworkPredictor::LEARN_LOAD_TOPLEVEL, attrs);
+  PredictorPredict(aLoadState->URI(), nullptr,
+                   nsINetworkPredictor::PREDICT_LOAD, attrs, nullptr);
+
+  nsCOMPtr<nsIRequest> req;
+  rv = DoURILoad(aLoadState, aCacheKey, getter_AddRefs(req));
+
+  if (NS_SUCCEEDED(rv)) {
+    if (shouldTakeFocus) {
+      mBrowsingContext->Focus(CallerType::System, IgnoreErrors());
+    }
+  }
+
+  if (NS_FAILED(rv)) {
+    nsCOMPtr<nsIChannel> chan(do_QueryInterface(req));
+    UnblockEmbedderLoadEventForFailure();
+    nsCOMPtr<nsIURI> uri = aLoadState->URI();
+    if (DisplayLoadError(rv, uri, nullptr, chan) &&
+        // FIXME: At this point code was using internal load flags, but checking
+        // non-internal load flags?
+        aLoadState->HasLoadFlags(LOAD_FLAGS_ERROR_LOAD_CHANGES_RV)) {
+      return NS_ERROR_LOAD_SHOWED_ERRORPAGE;
+    }
+
+    // We won't report any error if this is an unknown protocol error. The
+    // reason behind this is that it will allow enumeration of external
+    // protocols if we report an error for each unknown protocol.
+    if (NS_ERROR_UNKNOWN_PROTOCOL == rv) {
+      return NS_OK;
+    }
+  }
+
+  return rv;
+}
+
+/* static */
+bool nsDocShell::CanLoadInParentProcess(nsIURI* aURI) {
+  nsCOMPtr<nsIURI> uri = aURI;
+  // In e10s, in the parent process, we refuse to load anything other than
+  // "safe" resources that we ship or trust enough to give "special" URLs.
+  bool canLoadInParent = false;
+  if (NS_SUCCEEDED(NS_URIChainHasFlags(
+          uri, nsIProtocolHandler::URI_IS_UI_RESOURCE, &canLoadInParent)) &&
+      canLoadInParent) {
+    // We allow UI resources.
+    return true;
+  }
+  // For about: and extension-based URIs, which don't get
+  // URI_IS_UI_RESOURCE, first remove layers of view-source:, if present.
+  while (uri && uri->SchemeIs("view-source")) {
+    nsCOMPtr<nsINestedURI> nested = do_QueryInterface(uri);
+    if (nested) {
+      nested->GetInnerURI(getter_AddRefs(uri));
+    } else {
+      break;
+    }
+  }
+  // Allow about: URIs, and allow moz-extension ones if we're running
+  // extension content in the parent process.
+  if (!uri || uri->SchemeIs("about") ||
+      (!StaticPrefs::extensions_webextensions_remote() &&
+       uri->SchemeIs("moz-extension"))) {
+    return true;
+  }
+#ifdef MOZ_THUNDERBIRD
+  if (uri->SchemeIs("imap") || uri->SchemeIs("mailbox") ||
+      uri->SchemeIs("news") || uri->SchemeIs("nntp") ||
+      uri->SchemeIs("snews")) {
+    return true;
+  }
+#endif
+  nsAutoCString scheme;
+  uri->GetScheme(scheme);
+  // Allow ext+foo URIs (extension-registered custom protocols). See
+  // https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/protocol_handlers
+  if (StringBeginsWith(scheme, "ext+"_ns) &&
+      !StaticPrefs::extensions_webextensions_remote()) {
+    return true;
+  }
+  // Final exception for some legacy automated tests:
+  if (xpc::IsInAutomation() &&
+      StaticPrefs::security_allow_unsafe_parent_loads()) {
+    return true;
+  }
+  return false;
+}
+
+nsIPrincipal* nsDocShell::GetInheritedPrincipal(
+    bool aConsiderCurrentDocument, bool aConsiderPartitionedPrincipal) {
+  RefPtr<Document> document;
+  bool inheritedFromCurrent = false;
+
+  if (aConsiderCurrentDocument && mDocumentViewer) {
+    document = mDocumentViewer->GetDocument();
+    inheritedFromCurrent = true;
+  }
+
+  if (!document) {
+    nsCOMPtr<nsIDocShellTreeItem> parentItem;
+    GetInProcessSameTypeParent(getter_AddRefs(parentItem));
+    if (parentItem) {
+      document = parentItem->GetDocument();
+    }
+  }
+
+  if (!document) {
+    if (!aConsiderCurrentDocument) {
+      return nullptr;
+    }
+
+    // Make sure we end up with _something_ as the principal no matter
+    // what.If this fails, we'll just get a null docViewer and bail.
+    EnsureDocumentViewer();
+    if (!mDocumentViewer) {
+      return nullptr;
+    }
+    document = mDocumentViewer->GetDocument();
+  }
+
+  //-- Get the document's principal
+  if (document) {
+    nsIPrincipal* docPrincipal = aConsiderPartitionedPrincipal
+                                     ? document->PartitionedPrincipal()
+                                     : document->NodePrincipal();
+
+    // Don't allow loads in typeContent docShells to inherit the system
+    // principal from existing documents.
+    if (inheritedFromCurrent && mItemType == typeContent &&
+        docPrincipal->IsSystemPrincipal()) {
+      return nullptr;
+    }
+
+    return docPrincipal;
+  }
+
+  return nullptr;
+}
+
+/* static */ nsresult nsDocShell::CreateRealChannelForDocument(
+    nsIChannel** aChannel, nsIURI* aURI, nsILoadInfo* aLoadInfo,
+    nsIInterfaceRequestor* aCallbacks, nsLoadFlags aLoadFlags,
+    const nsAString& aSrcdoc, nsIURI* aBaseURI) {
+  nsCOMPtr<nsIChannel> channel;
+  if (aSrcdoc.IsVoid()) {
+    MOZ_TRY(NS_NewChannelInternal(getter_AddRefs(channel), aURI, aLoadInfo,
+                                  nullptr,  // PerformanceStorage
+                                  nullptr,  // loadGroup
+                                  aCallbacks, aLoadFlags));
+
+    if (aBaseURI) {
+      nsCOMPtr<nsIViewSourceChannel> vsc = do_QueryInterface(channel);
+      if (vsc) {
+        MOZ_ALWAYS_SUCCEEDS(vsc->SetBaseURI(aBaseURI));
+      }
+    }
+  } else if (SchemeIsViewSource(aURI)) {
+    // Instantiate view source handler protocol, if it doesn't exist already.
+    nsCOMPtr<nsIIOService> io(do_GetIOService());
+    MOZ_ASSERT(io);
+    nsCOMPtr<nsIProtocolHandler> handler;
+    nsresult rv =
+        io->GetProtocolHandler("view-source", getter_AddRefs(handler));
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    nsViewSourceHandler* vsh = nsViewSourceHandler::GetInstance();
+    if (!vsh) {
+      return NS_ERROR_FAILURE;
+    }
+
+    MOZ_TRY(vsh->NewSrcdocChannel(aURI, aBaseURI, aSrcdoc, aLoadInfo,
+                                  getter_AddRefs(channel)));
+  } else {
+    MOZ_TRY(NS_NewInputStreamChannelInternal(getter_AddRefs(channel), aURI,
+                                             aSrcdoc, "text/html"_ns, aLoadInfo,
+                                             true));
+    nsCOMPtr<nsIInputStreamChannel> isc = do_QueryInterface(channel);
+    MOZ_ASSERT(isc);
+    isc->SetBaseURI(aBaseURI);
+  }
+
+  if (aLoadFlags != nsIRequest::LOAD_NORMAL) {
+    nsresult rv = channel->SetLoadFlags(aLoadFlags);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  channel.forget(aChannel);
+  return NS_OK;
+}
+
+/* static */ bool nsDocShell::CreateAndConfigureRealChannelForLoadState(
+    BrowsingContext* aBrowsingContext, nsDocShellLoadState* aLoadState,
+    LoadInfo* aLoadInfo, nsIInterfaceRequestor* aCallbacks,
+    nsDocShell* aDocShell, const OriginAttributes& aOriginAttributes,
+    nsLoadFlags aLoadFlags, uint32_t aCacheKey, nsresult& aRv,
+    nsIChannel** aChannel) {
+  MOZ_ASSERT(aLoadInfo);
+
+  nsString srcdoc = VoidString();
+  bool isSrcdoc =
+      aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_IS_SRCDOC);
+  if (isSrcdoc) {
+    srcdoc = aLoadState->SrcdocData();
+  }
+
+  aLoadInfo->SetTriggeringRemoteType(
+      aLoadState->GetEffectiveTriggeringRemoteType());
+
+  if (aLoadState->PrincipalToInherit()) {
+    aLoadInfo->SetPrincipalToInherit(aLoadState->PrincipalToInherit());
+  }
+  aLoadInfo->SetLoadTriggeredFromExternal(
+      aLoadState->HasLoadFlags(LOAD_FLAGS_FROM_EXTERNAL));
+  aLoadInfo->SetForceAllowDataURI(aLoadState->HasInternalLoadFlags(
+      INTERNAL_LOAD_FLAGS_FORCE_ALLOW_DATA_URI));
+  aLoadInfo->SetOriginalFrameSrcLoad(
+      aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_ORIGINAL_FRAME_SRC));
+
+  bool inheritAttrs = false;
+  if (aLoadState->PrincipalToInherit()) {
+    inheritAttrs = nsContentUtils::ChannelShouldInheritPrincipal(
+        aLoadState->PrincipalToInherit(), aLoadState->URI(),
+        true,  // aInheritForAboutBlank
+        isSrcdoc);
+  }
+
+  // Strip the target query parameters before creating the channel.
+  aLoadState->MaybeStripTrackerQueryStrings(aBrowsingContext);
+
+  OriginAttributes attrs;
+
+  // Inherit origin attributes from PrincipalToInherit if inheritAttrs is
+  // true. Otherwise we just use the origin attributes from docshell.
+  if (inheritAttrs) {
+    MOZ_ASSERT(aLoadState->PrincipalToInherit(),
+               "We should have PrincipalToInherit here.");
+    attrs = aLoadState->PrincipalToInherit()->OriginAttributesRef();
+    // If firstPartyIsolation is not enabled, then PrincipalToInherit should
+    // have the same origin attributes with docshell.
+    MOZ_ASSERT_IF(!OriginAttributes::IsFirstPartyEnabled(),
+                  attrs == aOriginAttributes);
+  } else {
+    attrs = aOriginAttributes;
+    attrs.SetFirstPartyDomain(IsTopLevelDoc(aBrowsingContext, aLoadInfo),
+                              aLoadState->URI());
+  }
+
+  aRv = aLoadInfo->SetOriginAttributes(attrs);
+  if (NS_WARN_IF(NS_FAILED(aRv))) {
+    return false;
+  }
+
+  if (aLoadState->GetIsFromProcessingFrameAttributes()) {
+    aLoadInfo->SetIsFromProcessingFrameAttributes();
+  }
+
+  // Propagate the IsFormSubmission flag to the loadInfo.
+  if (aLoadState->IsFormSubmission()) {
+    aLoadInfo->SetIsFormSubmission(true);
+  }
+
+  aLoadInfo->SetUnstrippedURI(aLoadState->GetUnstrippedURI());
+
+  nsCOMPtr<nsIChannel> channel;
+  aRv = CreateRealChannelForDocument(getter_AddRefs(channel), aLoadState->URI(),
+                                     aLoadInfo, aCallbacks, aLoadFlags, srcdoc,
+                                     aLoadState->BaseURI());
+  NS_ENSURE_SUCCESS(aRv, false);
+
+  if (!channel) {
+    return false;
+  }
+
+  // If the HTTPS-Only mode is enabled, every insecure request gets upgraded to
+  // HTTPS by default. This behavior can be disabled through the loadinfo flag
+  // HTTPS_ONLY_EXEMPT.
+  nsHTTPSOnlyUtils::TestSitePermissionAndPotentiallyAddExemption(channel);
+
+  // hack
+  nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(channel));
+  nsCOMPtr<nsIHttpChannelInternal> httpChannelInternal(
+      do_QueryInterface(channel));
+  nsCOMPtr<nsIURI> referrer;
+  nsIReferrerInfo* referrerInfo = aLoadState->GetReferrerInfo();
+  if (referrerInfo) {
+    referrerInfo->GetOriginalReferrer(getter_AddRefs(referrer));
+  }
+  if (httpChannelInternal) {
+    if (aLoadState->HasInternalLoadFlags(
+            INTERNAL_LOAD_FLAGS_FORCE_ALLOW_COOKIES)) {
+      aRv = httpChannelInternal->SetThirdPartyFlags(
+          nsIHttpChannelInternal::THIRD_PARTY_FORCE_ALLOW);
+      MOZ_ASSERT(NS_SUCCEEDED(aRv));
+    }
+    if (aLoadState->FirstParty()) {
+      aRv = httpChannelInternal->SetDocumentURI(aLoadState->URI());
+      MOZ_ASSERT(NS_SUCCEEDED(aRv));
+    } else {
+      aRv = httpChannelInternal->SetDocumentURI(referrer);
+      MOZ_ASSERT(NS_SUCCEEDED(aRv));
+    }
+    aRv = httpChannelInternal->SetRedirectMode(
+        nsIHttpChannelInternal::REDIRECT_MODE_MANUAL);
+    MOZ_ASSERT(NS_SUCCEEDED(aRv));
+  }
+
+  if (httpChannel) {
+    if (aLoadState->HeadersStream()) {
+      aRv = AddHeadersToChannel(aLoadState->HeadersStream(), httpChannel);
+    }
+    // Set the referrer explicitly
+    // Referrer is currenly only set for link clicks here.
+    if (referrerInfo) {
+      aRv = httpChannel->SetReferrerInfo(referrerInfo);
+      MOZ_ASSERT(NS_SUCCEEDED(aRv));
+    }
+
+    // Mark the http channel as UrgentStart for top level document loading in
+    // active tab.
+    if (IsUrgentStart(aBrowsingContext, aLoadInfo, aLoadState->LoadType())) {
+      nsCOMPtr<nsIClassOfService> cos(do_QueryInterface(channel));
+      if (cos) {
+        cos->AddClassFlags(nsIClassOfService::UrgentStart);
+      }
+    }
+  }
+
+  channel->SetOriginalURI(aLoadState->OriginalURI() ? aLoadState->OriginalURI()
+                                                    : aLoadState->URI());
+
+  const nsACString& typeHint = aLoadState->TypeHint();
+  if (!typeHint.IsVoid()) {
+    channel->SetContentType(typeHint);
+  }
+
+  const nsAString& fileName = aLoadState->FileName();
+  if (!fileName.IsVoid()) {
+    aRv = channel->SetContentDisposition(nsIChannel::DISPOSITION_ATTACHMENT);
+    NS_ENSURE_SUCCESS(aRv, false);
+    if (!fileName.IsEmpty()) {
+      aRv = channel->SetContentDispositionFilename(fileName);
+      NS_ENSURE_SUCCESS(aRv, false);
+    }
+  }
+
+  if (nsCOMPtr<nsIWritablePropertyBag2> props = do_QueryInterface(channel)) {
+    nsCOMPtr<nsIURI> referrer;
+    nsIReferrerInfo* referrerInfo = aLoadState->GetReferrerInfo();
+    if (referrerInfo) {
+      referrerInfo->GetOriginalReferrer(getter_AddRefs(referrer));
+    }
+    // save true referrer for those who need it (e.g. xpinstall whitelisting)
+    // Currently only http and ftp channels support this.
+    props->SetPropertyAsInterface(u"docshell.internalReferrer"_ns, referrer);
+
+    if (aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_FIRST_LOAD)) {
+      props->SetPropertyAsBool(u"docshell.newWindowTarget"_ns, true);
+    }
+  }
+
+  nsCOMPtr<nsICacheInfoChannel> cacheChannel(do_QueryInterface(channel));
+  auto loadType = aLoadState->LoadType();
+
+  if (loadType == LOAD_RELOAD_NORMAL &&
+      StaticPrefs::
+          browser_soft_reload_only_force_validate_top_level_document()) {
+    nsCOMPtr<nsICacheInfoChannel> cachingChannel = do_QueryInterface(channel);
+    if (cachingChannel) {
+      cachingChannel->SetForceValidateCacheContent(true);
+    }
+  }
+
+  // figure out if we need to set the post data stream on the channel...
+  if (aLoadState->PostDataStream()) {
+    if (nsCOMPtr<nsIFormPOSTActionChannel> postChannel =
+            do_QueryInterface(channel)) {
+      // XXX it's a bit of a hack to rewind the postdata stream here but
+      // it has to be done in case the post data is being reused multiple
+      // times.
+      nsCOMPtr<nsISeekableStream> postDataSeekable =
+          do_QueryInterface(aLoadState->PostDataStream());
+      if (postDataSeekable) {
+        aRv = postDataSeekable->Seek(nsISeekableStream::NS_SEEK_SET, 0);
+        NS_ENSURE_SUCCESS(aRv, false);
+      }
+
+      // we really need to have a content type associated with this stream!!
+      postChannel->SetUploadStream(aLoadState->PostDataStream(), ""_ns, -1);
+
+      // Ownership of the stream has transferred to the channel, clear our
+      // reference.
+      aLoadState->SetPostDataStream(nullptr);
+    }
+
+    /* If there is a valid postdata *and* it is a History Load,
+     * set up the cache key on the channel, to retrieve the
+     * data *only* from the cache. If it is a normal reload, the
+     * cache is free to go to the server for updated postdata.
+     */
+    if (cacheChannel && aCacheKey != 0) {
+      if (loadType == LOAD_HISTORY || loadType == LOAD_RELOAD_CHARSET_CHANGE) {
+        cacheChannel->SetCacheKey(aCacheKey);
+        uint32_t loadFlags;
+        if (NS_SUCCEEDED(channel->GetLoadFlags(&loadFlags))) {
+          channel->SetLoadFlags(loadFlags |
+                                nsICachingChannel::LOAD_ONLY_FROM_CACHE);
+        }
+      } else if (loadType == LOAD_RELOAD_NORMAL) {
+        cacheChannel->SetCacheKey(aCacheKey);
+      }
+    }
+  } else {
+    /* If there is no postdata, set the cache key on the channel, and
+     * do not set the LOAD_ONLY_FROM_CACHE flag, so that the channel
+     * will be free to get it from net if it is not found in cache.
+     * New cache may use it creatively on CGI pages with GET
+     * method and even on those that say "no-cache"
+     */
+    if (loadType == LOAD_HISTORY || loadType == LOAD_RELOAD_NORMAL ||
+        loadType == LOAD_RELOAD_CHARSET_CHANGE ||
+        loadType == LOAD_RELOAD_CHARSET_CHANGE_BYPASS_CACHE ||
+        loadType == LOAD_RELOAD_CHARSET_CHANGE_BYPASS_PROXY_AND_CACHE) {
+      if (cacheChannel && aCacheKey != 0) {
+        cacheChannel->SetCacheKey(aCacheKey);
+      }
+    }
+  }
+
+  if (nsCOMPtr<nsIScriptChannel> scriptChannel = do_QueryInterface(channel)) {
+    // Allow execution against our context if the principals match
+    scriptChannel->SetExecutionPolicy(nsIScriptChannel::EXECUTE_NORMAL);
+  }
+
+  if (nsCOMPtr<nsITimedChannel> timedChannel = do_QueryInterface(channel)) {
+    timedChannel->SetTimingEnabled(true);
+
+    nsString initiatorType;
+    switch (aLoadInfo->InternalContentPolicyType()) {
+      case nsIContentPolicy::TYPE_INTERNAL_EMBED:
+        initiatorType = u"embed"_ns;
+        break;
+      case nsIContentPolicy::TYPE_INTERNAL_OBJECT:
+        initiatorType = u"object"_ns;
+        break;
+      default: {
+        const auto& embedderElementType =
+            aBrowsingContext->GetEmbedderElementType();
+        if (embedderElementType) {
+          initiatorType = *embedderElementType;
+        }
+        break;
+      }
+    }
+
+    if (!initiatorType.IsEmpty()) {
+      timedChannel->SetInitiatorType(initiatorType);
+    }
+  }
+
+  nsCOMPtr<nsIURI> rpURI;
+  aLoadInfo->GetResultPrincipalURI(getter_AddRefs(rpURI));
+  Maybe<nsCOMPtr<nsIURI>> originalResultPrincipalURI;
+  aLoadState->GetMaybeResultPrincipalURI(originalResultPrincipalURI);
+  if (originalResultPrincipalURI &&
+      (!aLoadState->KeepResultPrincipalURIIfSet() || !rpURI)) {
+    // Unconditionally override, we want the replay to be equal to what has
+    // been captured.
+    aLoadInfo->SetResultPrincipalURI(originalResultPrincipalURI.ref());
+  }
+
+  if (aLoadState->OriginalURI() && aLoadState->LoadReplace()) {
+    // The LOAD_REPLACE flag and its handling here will be removed as part
+    // of bug 1319110.  For now preserve its restoration here to not break
+    // any code expecting it being set specially on redirected channels.
+    // If the flag has originally been set to change result of
+    // NS_GetFinalChannelURI it won't have any effect and also won't cause
+    // any harm.
+    uint32_t loadFlags;
+    aRv = channel->GetLoadFlags(&loadFlags);
+    NS_ENSURE_SUCCESS(aRv, false);
+    channel->SetLoadFlags(loadFlags | nsIChannel::LOAD_REPLACE);
+  }
+
+  nsCOMPtr<nsIContentSecurityPolicy> csp = aLoadState->Csp();
+  if (csp) {
+    // Navigational requests that are same origin need to be upgraded in case
+    // upgrade-insecure-requests is present. Please note that for document
+    // navigations that bit is re-computed in case we encounter a server
+    // side redirect so the navigation is not same-origin anymore.
+    bool upgradeInsecureRequests = false;
+    csp->GetUpgradeInsecureRequests(&upgradeInsecureRequests);
+    if (upgradeInsecureRequests) {
+      // only upgrade if the navigation is same origin
+      nsCOMPtr<nsIPrincipal> resultPrincipal;
+      aRv = nsContentUtils::GetSecurityManager()->GetChannelResultPrincipal(
+          channel, getter_AddRefs(resultPrincipal));
+      NS_ENSURE_SUCCESS(aRv, false);
+      if (nsContentSecurityUtils::IsConsideredSameOriginForUIR(
+              aLoadState->TriggeringPrincipal(), resultPrincipal)) {
+        aLoadInfo->SetUpgradeInsecureRequests(true);
+      }
+    }
+
+    // For document loads we store the CSP that potentially needs to
+    // be inherited by the new document, e.g. in case we are loading
+    // an opaque origin like a data: URI. The actual inheritance
+    // check happens within Document::InitCSP().
+    // Please create an actual copy of the CSP (do not share the same
+    // reference) otherwise a Meta CSP of an opaque origin will
+    // incorrectly be propagated to the embedding document.
+    RefPtr<nsCSPContext> cspToInherit = new nsCSPContext();
+    cspToInherit->InitFromOther(static_cast<nsCSPContext*>(csp.get()));
+    aLoadInfo->SetCSPToInherit(cspToInherit);
+  }
+
+  channel.forget(aChannel);
+  return true;
+}
+
+bool nsDocShell::IsAboutBlankLoadOntoInitialAboutBlank(
+    nsIURI* aURI, bool aInheritPrincipal, nsIPrincipal* aPrincipalToInherit) {
+  return NS_IsAboutBlank(aURI) && aInheritPrincipal &&
+         (aPrincipalToInherit == GetInheritedPrincipal(false)) &&
+         (!mDocumentViewer || !mDocumentViewer->GetDocument() ||
+          mDocumentViewer->GetDocument()->IsInitialDocument());
+}
+
+nsresult nsDocShell::DoURILoad(nsDocShellLoadState* aLoadState,
+                               Maybe<uint32_t> aCacheKey,
+                               nsIRequest** aRequest) {
+  // Double-check that we're still around to load this URI.
+  if (mIsBeingDestroyed) {
+    // Return NS_OK despite not doing anything to avoid throwing exceptions
+    // from nsLocation::SetHref if the unload handler of the existing page
+    // tears us down.
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURILoader> uriLoader = components::URILoader::Service();
+  if (NS_WARN_IF(!uriLoader)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // Persist and sync layout history state before we load a new uri, as this
+  // might be our last chance to do so, in the content process.
+  PersistLayoutHistoryState();
+  SynchronizeLayoutHistoryState();
+
+  nsresult rv;
+  nsContentPolicyType contentPolicyType = DetermineContentType();
+
+  if (IsSubframe()) {
+    MOZ_ASSERT(contentPolicyType == nsIContentPolicy::TYPE_INTERNAL_IFRAME ||
+                   contentPolicyType == nsIContentPolicy::TYPE_INTERNAL_FRAME,
+               "DoURILoad thinks this is a frame and InternalLoad does not");
+
+    if (StaticPrefs::dom_block_external_protocol_in_iframes()) {
+      // Only allow URLs able to return data in iframes.
+      if (nsContentUtils::IsExternalProtocol(aLoadState->URI())) {
+        // The context to check user-interaction with for the purposes of
+        // popup-blocking.
+        //
+        // We generally want to check the context that initiated the navigation.
+        WindowContext* sourceWindowContext = [&] {
+          const MaybeDiscardedBrowsingContext& sourceBC =
+              aLoadState->SourceBrowsingContext();
+          if (!sourceBC.IsNullOrDiscarded()) {
+            if (WindowContext* wc = sourceBC.get()->GetCurrentWindowContext()) {
+              return wc;
+            }
+          }
+          return mBrowsingContext->GetParentWindowContext();
+        }();
+
+        MOZ_ASSERT(sourceWindowContext);
+        // FIXME: We can't check user-interaction against an OOP window. This is
+        // the next best thing we can really do. The load state keeps whether
+        // the navigation had a user interaction in process
+        // (aLoadState->HasValidUserGestureActivation()), but we can't really
+        // consume it, which we want to prevent popup-spamming from the same
+        // click event.
+        WindowContext* context =
+            sourceWindowContext->IsInProcess()
+                ? sourceWindowContext
+                : mBrowsingContext->GetCurrentWindowContext();
+        const bool popupBlocked = [&] {
+          const bool active = mBrowsingContext->IsActive();
+
+          // For same-origin-with-top windows, we grant a single free popup
+          // without user activation, see bug 1680721.
+          //
+          // We consume the flag now even if there's no user activation.
+          const bool hasFreePass = [&] {
+            if (!active ||
+                !(context->IsInProcess() && context->SameOriginWithTop())) {
+              return false;
+            }
+            nsGlobalWindowInner* win =
+                context->TopWindowContext()->GetInnerWindow();
+            return win && win->TryOpenExternalProtocolIframe();
+          }();
+
+          if (context->IsInProcess() &&
+              context->ConsumeTransientUserGestureActivation()) {
+            // If the user has interacted with the page, consume it.
+            return false;
+          }
+
+          // TODO(emilio): Can we remove this check? It seems like what prompted
+          // this code (bug 1514547) should be covered by transient user
+          // activation, see bug 1514547.
+          if (active &&
+              PopupBlocker::ConsumeTimerTokenForExternalProtocolIframe()) {
+            return false;
+          }
+
+          if (sourceWindowContext->CanShowPopup()) {
+            return false;
+          }
+
+          if (hasFreePass) {
+            return false;
+          }
+
+          return true;
+        }();
+
+        // No error must be returned when iframes are blocked.
+        if (popupBlocked) {
+          nsAutoString message;
+          nsresult rv = nsContentUtils::GetLocalizedString(
+              nsContentUtils::eDOM_PROPERTIES,
+              "ExternalProtocolFrameBlockedNoUserActivation", message);
+          if (NS_SUCCEEDED(rv)) {
+            nsContentUtils::ReportToConsoleByWindowID(
+                message, nsIScriptError::warningFlag, "DOM"_ns,
+                context->InnerWindowId());
+          }
+          return NS_OK;
+        }
+      }
+    }
+
+    // Only allow view-source scheme in top-level docshells. view-source is
+    // the only scheme to which this applies at the moment due to potential
+    // timing attacks to read data from cross-origin iframes. If this widens
+    // we should add a protocol flag for whether the scheme is allowed in
+    // frames and use something like nsNetUtil::NS_URIChainHasFlags.
+    nsCOMPtr<nsIURI> tempURI = aLoadState->URI();
+    nsCOMPtr<nsINestedURI> nestedURI = do_QueryInterface(tempURI);
+    while (nestedURI) {
+      // view-source should always be an nsINestedURI, loop and check the
+      // scheme on this and all inner URIs that are also nested URIs.
+      if (SchemeIsViewSource(tempURI)) {
+        return NS_ERROR_UNKNOWN_PROTOCOL;
+      }
+      nestedURI->GetInnerURI(getter_AddRefs(tempURI));
+      nestedURI = do_QueryInterface(tempURI);
+    }
+  } else {
+    MOZ_ASSERT(contentPolicyType == nsIContentPolicy::TYPE_DOCUMENT,
+               "DoURILoad thinks this is a document and InternalLoad does not");
+  }
+
+  // We want to inherit aLoadState->PrincipalToInherit() when:
+  // 1. ChannelShouldInheritPrincipal returns true.
+  // 2. aLoadState->URI() is not data: URI, or data: URI is not
+  //    configured as unique opaque origin.
+  bool inheritPrincipal = false;
+
+  if (aLoadState->PrincipalToInherit()) {
+    bool isSrcdoc =
+        aLoadState->HasInternalLoadFlags(INTERNAL_LOAD_FLAGS_IS_SRCDOC);
+    bool inheritAttrs = nsContentUtils::ChannelShouldInheritPrincipal(
+        aLoadState->PrincipalToInherit(), aLoadState->URI(),
+        true,  // aInheritForAboutBlank
+        isSrcdoc);
+
+    inheritPrincipal = inheritAttrs && !SchemeIsData(aLoadState->URI());
+  }
+
+  // See https://bugzilla.mozilla.org/show_bug.cgi?id=1736570
+  const bool isAboutBlankLoadOntoInitialAboutBlank =
+      IsAboutBlankLoadOntoInitialAboutBlank(aLoadState->URI(), inheritPrincipal,
+                                            aLoadState->PrincipalToInherit());
+
+  // FIXME We still have a ton of codepaths that don't pass through
+  //       DocumentLoadListener, so probably need to create session history info
+  //       in more places.
+  if (aLoadState->GetLoadingSessionHistoryInfo()) {
+    SetLoadingSessionHistoryInfo(*aLoadState->GetLoadingSessionHistoryInfo());
+  } else if (isAboutBlankLoadOntoInitialAboutBlank &&
+             mozilla::SessionHistoryInParent()) {
+    // Materialize LoadingSessionHistoryInfo here, because DocumentChannel
+    // loads have it, and later history behavior depends on it existing.
+    UniquePtr<SessionHistoryInfo> entry = MakeUnique<SessionHistoryInfo>(
+        aLoadState->URI(), aLoadState->TriggeringPrincipal(),
+        aLoadState->PrincipalToInherit(),
+        aLoadState->PartitionedPrincipalToInherit(), aLoadState->Csp(),
+        mContentTypeHint);
+    mozilla::dom::LoadingSessionHistoryInfo info(*entry);
+    SetLoadingSessionHistoryInfo(info, true);
+  }
+
+  // open a channel for the url
+
+  // If we have a pending channel, use the channel we've already created here.
+  // We don't need to set up load flags for our channel, as it has already been
+  // created.
+
+  if (nsCOMPtr<nsIChannel> channel =
+          aLoadState->GetPendingRedirectedChannel()) {
+    // If we have a request outparameter, shove our channel into it.
+    if (aRequest) {
+      nsCOMPtr<nsIRequest> outRequest = channel;
+      outRequest.forget(aRequest);
+    }
+
+    return OpenRedirectedChannel(aLoadState);
+  }
+
+  // There are two cases we care about:
+  // * Top-level load: In this case, loadingNode is null, but loadingWindow
+  //   is our mScriptGlobal. We pass null for loadingPrincipal in this case.
+  // * Subframe load: loadingWindow is null, but loadingNode is the frame
+  //   element for the load. loadingPrincipal is the NodePrincipal of the
+  //   frame element.
+  nsCOMPtr<nsINode> loadingNode;
+  nsCOMPtr<nsPIDOMWindowOuter> loadingWindow;
+  nsCOMPtr<nsIPrincipal> loadingPrincipal;
+  nsCOMPtr<nsISupports> topLevelLoadingContext;
+
+  if (contentPolicyType == nsIContentPolicy::TYPE_DOCUMENT) {
+    loadingNode = nullptr;
+    loadingPrincipal = nullptr;
+    loadingWindow = mScriptGlobal;
+    if (XRE_IsContentProcess()) {
+      // In e10s the child process doesn't have access to the element that
+      // contains the browsing context (because that element is in the chrome
+      // process).
+      nsCOMPtr<nsIBrowserChild> browserChild = GetBrowserChild();
+      topLevelLoadingContext = ToSupports(browserChild);
+    } else {
+      // This is for loading non-e10s tabs and toplevel windows of various
+      // sorts.
+      // For the toplevel window cases, requestingElement will be null.
+      nsCOMPtr<Element> requestingElement =
+          loadingWindow->GetFrameElementInternal();
+      topLevelLoadingContext = requestingElement;
+    }
+  } else {
+    loadingWindow = nullptr;
+    loadingNode = mScriptGlobal->GetFrameElementInternal();
+    if (loadingNode) {
+      // If we have a loading node, then use that as our loadingPrincipal.
+      loadingPrincipal = loadingNode->NodePrincipal();
+#ifdef DEBUG
+      // Get the docshell type for requestingElement.
+      RefPtr<Document> requestingDoc = loadingNode->OwnerDoc();
+      nsCOMPtr<nsIDocShell> elementDocShell = requestingDoc->GetDocShell();
+      // requestingElement docshell type = current docshell type.
+      MOZ_ASSERT(
+          mItemType == elementDocShell->ItemType(),
+          "subframes should have the same docshell type as their parent");
+#endif
+    } else {
+      if (mIsBeingDestroyed) {
+        // If this isn't a top-level load and mScriptGlobal's frame element is
+        // null, then the element got removed from the DOM while we were trying
+        // to load this resource. This docshell is scheduled for destruction
+        // already, so bail out here.
+        return NS_OK;
+      }
+      // If we are not being destroyed and we do not have access to the loading
+      // node, then we are a remote subframe. Set the loading principal
+      // to be a null principal and then set it correctly in the parent.
+      loadingPrincipal = NullPrincipal::Create(GetOriginAttributes(), nullptr);
+    }
+  }
+
+  if (!aLoadState->TriggeringPrincipal()) {
+    MOZ_ASSERT(false, "DoURILoad needs a valid triggeringPrincipal");
+    return NS_ERROR_FAILURE;
+  }
+
+  uint32_t sandboxFlags = mBrowsingContext->GetSandboxFlags();
+  nsSecurityFlags securityFlags =
+      nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL;
+
+  if (mLoadType == LOAD_ERROR_PAGE) {
+    securityFlags |= nsILoadInfo::SEC_LOAD_ERROR_PAGE;
+  }
+
+  if (inheritPrincipal) {
+    securityFlags |= nsILoadInfo::SEC_FORCE_INHERIT_PRINCIPAL;
+  }
+
+  // Must never have a parent for TYPE_DOCUMENT loads
+  MOZ_ASSERT_IF(contentPolicyType == nsIContentPolicy::TYPE_DOCUMENT,
+                !mBrowsingContext->GetParent());
+  // Subdocuments must have a parent
+  MOZ_ASSERT_IF(contentPolicyType == nsIContentPolicy::TYPE_SUBDOCUMENT,
+                mBrowsingContext->GetParent());
+  mBrowsingContext->SetTriggeringAndInheritPrincipals(
+      aLoadState->TriggeringPrincipal(), aLoadState->PrincipalToInherit(),
+      aLoadState->GetLoadIdentifier());
+  RefPtr<LoadInfo> loadInfo =
+      (contentPolicyType == nsIContentPolicy::TYPE_DOCUMENT)
+          ? new LoadInfo(loadingWindow, aLoadState->URI(),
+                         aLoadState->TriggeringPrincipal(),
+                         topLevelLoadingContext, securityFlags, sandboxFlags)
+          : new LoadInfo(loadingPrincipal, aLoadState->TriggeringPrincipal(),
+                         loadingNode, securityFlags, contentPolicyType,
+                         Maybe<mozilla::dom::ClientInfo>(),
+                         Maybe<mozilla::dom::ServiceWorkerDescriptor>(),
+                         sandboxFlags);
+  RefPtr<WindowContext> context = mBrowsingContext->GetCurrentWindowContext();
+
+  if (isAboutBlankLoadOntoInitialAboutBlank) {
+    // Match the DocumentChannel case where the default for third-partiness
+    // differs from the default in LoadInfo construction here.
+    // toolkit/components/antitracking/test/browser/browser_aboutblank.js
+    // fails without this.
+    BrowsingContext* top = mBrowsingContext->Top();
+    if (top == mBrowsingContext) {
+      // If we're at the top, this must be a window.open()ed
+      // window, and we can't be third-party relative to ourselves.
+      loadInfo->SetIsThirdPartyContextToTopWindow(false);
+    } else {
+      if (Document* topDoc = top->GetDocument()) {
+        bool thirdParty = false;
+        mozilla::Unused << topDoc->GetPrincipal()->IsThirdPartyPrincipal(
+            aLoadState->PrincipalToInherit(), &thirdParty);
+        loadInfo->SetIsThirdPartyContextToTopWindow(thirdParty);
+      } else {
+        // If top is in a different process, we have to be third-party relative
+        // to it.
+        loadInfo->SetIsThirdPartyContextToTopWindow(true);
+      }
+    }
+  }
+
+  if (mLoadType != LOAD_ERROR_PAGE && context && context->IsInProcess()) {
+    if (context->HasValidTransientUserGestureActivation()) {
+      aLoadState->SetHasValidUserGestureActivation(true);
+    }
+    if (!aLoadState->TriggeringWindowId()) {
+      aLoadState->SetTriggeringWindowId(context->Id());
+    }
+    if (!aLoadState->TriggeringStorageAccess()) {
+      Document* contextDoc = context->GetExtantDoc();
+      if (contextDoc) {
+        aLoadState->SetTriggeringStorageAccess(
+            contextDoc->UsingStorageAccess());
+      }
+    }
+  }
+
+  // in case this docshell load was triggered by a valid transient user gesture,
+  // or also the load originates from external, then we pass that information on
+  // to the loadinfo, which allows e.g. setting Sec-Fetch-User request headers.
+  if (aLoadState->HasValidUserGestureActivation() ||
+      aLoadState->HasLoadFlags(LOAD_FLAGS_FROM_EXTERNAL)) {
+    loadInfo->SetHasValidUserGestureActivation(true);
+  }
+
+  loadInfo->SetTriggeringWindowId(aLoadState->TriggeringWindowId());
+  loadInfo->SetTriggeringStorageAccess(aLoadState->TriggeringStorageAccess());
+  loadInfo->SetTriggeringSandboxFlags(aLoadState->TriggeringSandboxFlags());
+  loadInfo->SetIsMetaRefresh(aLoadState->IsMetaRefresh());
+
+  uint32_t cacheKey = 0;
+  if (aCacheKey) {
+    cacheKey = *aCacheKey;
+  } else if (mozilla::SessionHistoryInParent()) {
+    if (mLoadingEntry) {
+      cacheKey = mLoadingEntry->mInfo.GetCacheKey();
+    } else if (mActiveEntry) {  // for reload cases
+      cacheKey = mActiveEntry->GetCacheKey();
+    }
+  } else {
+    if (mLSHE) {
+      cacheKey = mLSHE->GetCacheKey();
+    } else if (mOSHE) {  // for reload cases
+      cacheKey = mOSHE->GetCacheKey();
+    }
+  }
+
+  bool uriModified;
+  if (mLSHE || mLoadingEntry) {
+    if (mLoadingEntry) {
+      uriModified = mLoadingEntry->mInfo.GetURIWasModified();
+    } else {
+      uriModified = mLSHE->GetURIWasModified();
+    }
+  } else {
+    uriModified = false;
+  }
+
+  bool isEmbeddingBlockedError = false;
+  if (mFailedChannel) {
+    nsresult status;
+    mFailedChannel->GetStatus(&status);
+    isEmbeddingBlockedError = status == NS_ERROR_XFO_VIOLATION ||
+                              status == NS_ERROR_CSP_FRAME_ANCESTOR_VIOLATION;
+  }
+
+  nsLoadFlags loadFlags = aLoadState->CalculateChannelLoadFlags(
+      mBrowsingContext, Some(uriModified), Some(isEmbeddingBlockedError));
+
+  nsCOMPtr<nsIChannel> channel;
+  if (DocumentChannel::CanUseDocumentChannel(aLoadState->URI()) &&
+      !isAboutBlankLoadOntoInitialAboutBlank) {
+    channel = DocumentChannel::CreateForDocument(
+        aLoadState, loadInfo, loadFlags, this, cacheKey, uriModified,
+        isEmbeddingBlockedError);
+    MOZ_ASSERT(channel);
+
+    // Disable keyword fixup when using DocumentChannel, since
+    // DocumentLoadListener will handle this for us (in the parent process).
+    mAllowKeywordFixup = false;
+  } else if (!CreateAndConfigureRealChannelForLoadState(
+                 mBrowsingContext, aLoadState, loadInfo, this, this,
+                 GetOriginAttributes(), loadFlags, cacheKey, rv,
+                 getter_AddRefs(channel))) {
+    return rv;
+  }
+
+  // Make sure to give the caller a channel if we managed to create one
+  // This is important for correct error page/session history interaction
+  if (aRequest) {
+    NS_ADDREF(*aRequest = channel);
+  }
+
+  const nsACString& typeHint = aLoadState->TypeHint();
+  if (!typeHint.IsVoid()) {
+    mContentTypeHint = typeHint;
+  } else {
+    mContentTypeHint.Truncate();
+  }
+
+  // Load attributes depend on load type...
+  if (mLoadType == LOAD_RELOAD_CHARSET_CHANGE) {
+    // Use SetAllowStaleCacheContent (not LOAD_FROM_CACHE flag) since we
+    // only want to force cache load for this channel, not the whole
+    // loadGroup.
+    nsCOMPtr<nsICacheInfoChannel> cachingChannel = do_QueryInterface(channel);
+    if (cachingChannel) {
+      cachingChannel->SetAllowStaleCacheContent(true);
+    }
+  }
+
+  uint32_t openFlags =
+      nsDocShell::ComputeURILoaderFlags(mBrowsingContext, mLoadType);
+  return OpenInitializedChannel(channel, uriLoader, openFlags);
+}
+
+static nsresult AppendSegmentToString(nsIInputStream* aIn, void* aClosure,
+                                      const char* aFromRawSegment,
+                                      uint32_t aToOffset, uint32_t aCount,
+                                      uint32_t* aWriteCount) {
+  // aFromSegment now contains aCount bytes of data.
+
+  nsAutoCString* buf = static_cast<nsAutoCString*>(aClosure);
+  buf->Append(aFromRawSegment, aCount);
+
+  // Indicate that we have consumed all of aFromSegment
+  *aWriteCount = aCount;
+  return NS_OK;
+}
+
+/* static */ nsresult nsDocShell::AddHeadersToChannel(
+    nsIInputStream* aHeadersData, nsIChannel* aGenericChannel) {
+  nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aGenericChannel);
+  NS_ENSURE_STATE(httpChannel);
+
+  uint32_t numRead;
+  nsAutoCString headersString;
+  nsresult rv = aHeadersData->ReadSegments(
+      AppendSegmentToString, &headersString, UINT32_MAX, &numRead);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // used during the manipulation of the String from the InputStream
+  nsAutoCString headerName;
+  nsAutoCString headerValue;
+  int32_t crlf;
+  int32_t colon;
+
+  //
+  // Iterate over the headersString: for each "\r\n" delimited chunk,
+  // add the value as a header to the nsIHttpChannel
+  //
+
+  static const char kWhitespace[] = "\b\t\r\n ";
+  while (true) {
+    crlf = headersString.Find("\r\n");
+    if (crlf == kNotFound) {
+      return NS_OK;
+    }
+
+    const nsACString& oneHeader = StringHead(headersString, crlf);
+
+    colon = oneHeader.FindChar(':');
+    if (colon == kNotFound) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    headerName = StringHead(oneHeader, colon);
+    headerValue = Substring(oneHeader, colon + 1);
+
+    headerName.Trim(kWhitespace);
+    headerValue.Trim(kWhitespace);
+
+    headersString.Cut(0, crlf + 2);
+
+    //
+    // FINALLY: we can set the header!
+    //
+
+    rv = httpChannel->SetRequestHeader(headerName, headerValue, true);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  MOZ_ASSERT_UNREACHABLE("oops");
+  return NS_ERROR_UNEXPECTED;
+}
+
+/* static */ uint32_t nsDocShell::ComputeURILoaderFlags(
+    BrowsingContext* aBrowsingContext, uint32_t aLoadType) {
+  MOZ_ASSERT(aBrowsingContext);
+
+  uint32_t openFlags = 0;
+  if (aLoadType == LOAD_LINK) {
+    openFlags |= nsIURILoader::IS_CONTENT_PREFERRED;
+  }
+  if (!aBrowsingContext->GetAllowContentRetargeting()) {
+    openFlags |= nsIURILoader::DONT_RETARGET;
+  }
+
+  return openFlags;
+}
+
+nsresult nsDocShell::OpenInitializedChannel(nsIChannel* aChannel,
+                                            nsIURILoader* aURILoader,
+                                            uint32_t aOpenFlags) {
+  nsresult rv = NS_OK;
+
+  // If anything fails here, make sure to clear our initial ClientSource.
+  auto cleanupInitialClient =
+      MakeScopeExit([&] { mInitialClientSource.reset(); });
+
+  nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
+  NS_ENSURE_TRUE(win, NS_ERROR_FAILURE);
+
+  MaybeCreateInitialClientSource();
+
+  // Let the client channel helper know if we are using DocumentChannel,
+  // since redirects get handled in the parent process in that case.
+  RefPtr<net::DocumentChannel> docChannel = do_QueryObject(aChannel);
+  if (docChannel && XRE_IsContentProcess()) {
+    // Tell the content process nsDocumentOpenInfo to not try to do
+    // any sort of targeting.
+    aOpenFlags |= nsIURILoader::DONT_RETARGET;
+  }
+
+  // Since we are loading a document we need to make sure the proper reserved
+  // and initial client data is stored on the nsILoadInfo.  The
+  // ClientChannelHelper does this and ensures that it is propagated properly
+  // on redirects.  We pass no reserved client here so that the helper will
+  // create the reserved ClientSource if necessary.
+  Maybe<ClientInfo> noReservedClient;
+  if (docChannel) {
+    // When using DocumentChannel, all redirect handling is done in the parent,
+    // so we just need the child variant to watch for the internal redirect
+    // to the final channel.
+    rv = AddClientChannelHelperInChild(aChannel,
+                                       GetMainThreadSerialEventTarget());
+    docChannel->SetInitialClientInfo(GetInitialClientInfo());
+  } else {
+    rv = AddClientChannelHelper(aChannel, std::move(noReservedClient),
+                                GetInitialClientInfo(),
+                                GetMainThreadSerialEventTarget());
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aURILoader->OpenURI(aChannel, aOpenFlags, this);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // We're about to load a new page and it may take time before necko
+  // gives back any data, so main thread might have a chance to process a
+  // collector slice
+  nsJSContext::MaybeRunNextCollectorSlice(this, JS::GCReason::DOCSHELL);
+
+  // Success.  Keep the initial ClientSource if it exists.
+  cleanupInitialClient.release();
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::OpenRedirectedChannel(nsDocShellLoadState* aLoadState) {
+  nsCOMPtr<nsIChannel> channel = aLoadState->GetPendingRedirectedChannel();
+  MOZ_ASSERT(channel);
+
+  // If anything fails here, make sure to clear our initial ClientSource.
+  auto cleanupInitialClient =
+      MakeScopeExit([&] { mInitialClientSource.reset(); });
+
+  nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
+  NS_ENSURE_TRUE(win, NS_ERROR_FAILURE);
+
+  MaybeCreateInitialClientSource();
+
+  nsCOMPtr<nsILoadInfo> loadInfo = channel->LoadInfo();
+
+  LoadInfo* li = static_cast<LoadInfo*>(loadInfo.get());
+  if (loadInfo->GetExternalContentPolicyType() ==
+      ExtContentPolicy::TYPE_DOCUMENT) {
+    li->UpdateBrowsingContextID(mBrowsingContext->Id());
+  } else if (loadInfo->GetExternalContentPolicyType() ==
+             ExtContentPolicy::TYPE_SUBDOCUMENT) {
+    li->UpdateFrameBrowsingContextID(mBrowsingContext->Id());
+  }
+
+  // If we did a process switch, then we should have an existing allocated
+  // ClientInfo, so we just need to allocate a corresponding ClientSource.
+  CreateReservedSourceIfNeeded(channel, GetMainThreadSerialEventTarget());
+
+  RefPtr<nsDocumentOpenInfo> loader =
+      new nsDocumentOpenInfo(this, nsIURILoader::DONT_RETARGET, nullptr);
+  channel->SetLoadGroup(mLoadGroup);
+
+  MOZ_ALWAYS_SUCCEEDS(loader->Prepare());
+
+  nsresult rv = NS_OK;
+  if (XRE_IsParentProcess()) {
+    // If we're in the parent, the we don't have an nsIChildChannel, just
+    // the original channel, which is already open in this process.
+
+    // DocumentLoadListener expects to get an nsIParentChannel, so
+    // we create a wrapper around the channel and nsIStreamListener
+    // that forwards functionality as needed, and then we register
+    // it under the provided identifier.
+    RefPtr<ParentChannelWrapper> wrapper =
+        new ParentChannelWrapper(channel, loader);
+    wrapper->Register(aLoadState->GetPendingRedirectChannelRegistrarId());
+
+    mLoadGroup->AddRequest(channel, nullptr);
+  } else if (nsCOMPtr<nsIChildChannel> childChannel =
+                 do_QueryInterface(channel)) {
+    // Our channel was redirected from another process, so doesn't need to
+    // be opened again. However, it does need its listener hooked up
+    // correctly.
+    rv = childChannel->CompleteRedirectSetup(loader);
+  } else {
+    // It's possible for the redirected channel to not implement
+    // nsIChildChannel and be entirely local (like srcdoc). In that case we
+    // can just open the local instance and it will work.
+    rv = channel->AsyncOpen(loader);
+  }
+  if (rv == NS_ERROR_NO_CONTENT) {
+    return NS_OK;
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Success.  Keep the initial ClientSource if it exists.
+  cleanupInitialClient.release();
+  return NS_OK;
+}
+
+// https://html.spec.whatwg.org/#scrolling-to-a-fragment
+nsresult nsDocShell::ScrollToAnchor(bool aCurHasRef, bool aNewHasRef,
+                                    nsACString& aNewHash, uint32_t aLoadType) {
+  if (!mCurrentURI) {
+    return NS_OK;
+  }
+
+  RefPtr<PresShell> presShell = GetPresShell();
+  if (!presShell) {
+    // If we failed to get the shell, or if there is no shell,
+    // nothing left to do here.
+    return NS_OK;
+  }
+
+  nsIScrollableFrame* rootScroll = presShell->GetRootScrollFrameAsScrollable();
+  if (rootScroll) {
+    rootScroll->ClearDidHistoryRestore();
+  }
+
+  // If we have no new anchor, we do not want to scroll, unless there is a
+  // current anchor and we are doing a history load.  So return if we have no
+  // new anchor, and there is no current anchor or the load is not a history
+  // load.
+  if ((!aCurHasRef || aLoadType != LOAD_HISTORY) && !aNewHasRef) {
+    return NS_OK;
+  }
+
+  // Both the new and current URIs refer to the same page. We can now
+  // browse to the hash stored in the new URI.
+
+  // If it's a load from history, we don't have any anchor jumping to do.
+  // Scrollbar position will be restored by the caller based on positions stored
+  // in session history.
+  bool scroll = aLoadType != LOAD_HISTORY && aLoadType != LOAD_RELOAD_NORMAL;
+
+  if (aNewHash.IsEmpty()) {
+    // 2. If fragment is the empty string, then return the special value top of
+    // the document.
+    //
+    // Tell the shell it's at an anchor without scrolling.
+    presShell->GoToAnchor(u""_ns, false);
+
+    if (scroll) {
+      // Scroll to the top of the page. Ignore the return value; failure to
+      // scroll here (e.g. if there is no root scrollframe) is not grounds for
+      // canceling the load!
+      SetCurScrollPosEx(0, 0);
+    }
+
+    return NS_OK;
+  }
+
+  // 3. Let potentialIndicatedElement be the result of finding a potential
+  // indicated element given document and fragment.
+  NS_ConvertUTF8toUTF16 uStr(aNewHash);
+  auto rv = presShell->GoToAnchor(uStr, scroll, ScrollFlags::ScrollSmoothAuto);
+
+  // 4. If potentialIndicatedElement is not null, then return
+  // potentialIndicatedElement.
+  if (NS_SUCCEEDED(rv)) {
+    return NS_OK;
+  }
+
+  // 5. Let fragmentBytes be the result of percent-decoding fragment.
+  nsAutoCString fragmentBytes;
+  const bool unescaped = NS_UnescapeURL(aNewHash.Data(), aNewHash.Length(),
+                                        /* aFlags = */ 0, fragmentBytes);
+
+  if (!unescaped) {
+    // Another attempt is only necessary if characters were unescaped.
+    return NS_OK;
+  }
+
+  if (fragmentBytes.IsEmpty()) {
+    // When aNewHash contains "%00", the unescaped string may be empty, and
+    // GoToAnchor asserts if we ask it to scroll to an empty ref.
+    presShell->GoToAnchor(u""_ns, false);
+    return NS_OK;
+  }
+
+  // 6. Let decodedFragment be the result of running UTF-8 decode without BOM on
+  // fragmentBytes.
+  nsAutoString decodedFragment;
+  rv = UTF_8_ENCODING->DecodeWithoutBOMHandling(fragmentBytes, decodedFragment);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // 7. Set potentialIndicatedElement to the result of finding a potential
+  // indicated element given document and decodedFragment.
+  //
+  // Ignore the return value of GoToAnchor, since it will return an error if
+  // there is no such anchor in the document, which is actually a success
+  // condition for us (we want to update the session history with the new URI no
+  // matter whether we actually scrolled somewhere).
+  presShell->GoToAnchor(decodedFragment, scroll, ScrollFlags::ScrollSmoothAuto);
+
+  return NS_OK;
+}
+
+bool nsDocShell::OnNewURI(nsIURI* aURI, nsIChannel* aChannel,
+                          nsIPrincipal* aTriggeringPrincipal,
+                          nsIPrincipal* aPrincipalToInherit,
+                          nsIPrincipal* aPartitionedPrincipalToInherit,
+                          nsIContentSecurityPolicy* aCsp,
+                          bool aAddToGlobalHistory, bool aCloneSHChildren) {
+  MOZ_ASSERT(aURI, "uri is null");
+  MOZ_ASSERT(!aChannel || !aTriggeringPrincipal, "Shouldn't have both set");
+
+  MOZ_ASSERT(!aPrincipalToInherit ||
+             (aPrincipalToInherit && aTriggeringPrincipal));
+
+#if defined(DEBUG)
+  if (MOZ_LOG_TEST(gDocShellLog, LogLevel::Debug)) {
+    nsAutoCString chanName;
+    if (aChannel) {
+      aChannel->GetName(chanName);
+    } else {
+      chanName.AssignLiteral("<no channel>");
+    }
+
+    MOZ_LOG(gDocShellLog, LogLevel::Debug,
+            ("nsDocShell[%p]::OnNewURI(\"%s\", [%s], 0x%x)\n", this,
+             aURI->GetSpecOrDefault().get(), chanName.get(), mLoadType));
+  }
+#endif
+
+  bool equalUri = false;
+
+  // Get the post data and the HTTP response code from the channel.
+  uint32_t responseStatus = 0;
+  nsCOMPtr<nsIInputStream> inputStream;
+  if (aChannel) {
+    nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(aChannel));
+
+    // Check if the HTTPChannel is hiding under a multiPartChannel
+    if (!httpChannel) {
+      GetHttpChannel(aChannel, getter_AddRefs(httpChannel));
+    }
+
+    if (httpChannel) {
+      nsCOMPtr<nsIUploadChannel> uploadChannel(do_QueryInterface(httpChannel));
+      if (uploadChannel) {
+        uploadChannel->GetUploadStream(getter_AddRefs(inputStream));
+      }
+
+      // If the response status indicates an error, unlink this session
+      // history entry from any entries sharing its document.
+      nsresult rv = httpChannel->GetResponseStatus(&responseStatus);
+      if (mLSHE && NS_SUCCEEDED(rv) && responseStatus >= 400) {
+        mLSHE->AbandonBFCacheEntry();
+        // FIXME Do the same for mLoadingEntry
+      }
+    }
+  }
+
+  // Determine if this type of load should update history.
+  bool updateGHistory = ShouldUpdateGlobalHistory(mLoadType);
+
+  // We don't update session history on reload unless we're loading
+  // an iframe in shift-reload case.
+  bool updateSHistory = mBrowsingContext->ShouldUpdateSessionHistory(mLoadType);
+
+  // Create SH Entry (mLSHE) only if there is a SessionHistory object in the
+  // root browsing context.
+  // FIXME If session history in the parent is enabled then we only do this if
+  //       the session history object is in process, otherwise we can't really
+  //       use the mLSHE anyway. Once session history is only stored in the
+  //       parent then this code will probably be removed anyway.
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+  if (!rootSH) {
+    updateSHistory = false;
+    updateGHistory = false;  // XXX Why global history too?
+  }
+
+  // Check if the url to be loaded is the same as the one already loaded.
+  if (mCurrentURI) {
+    aURI->Equals(mCurrentURI, &equalUri);
+  }
+
+#ifdef DEBUG
+  bool shAvailable = (rootSH != nullptr);
+
+  // XXX This log message is almost useless because |updateSHistory|
+  //     and |updateGHistory| are not correct at this point.
+
+  MOZ_LOG(gDocShellLog, LogLevel::Debug,
+          ("  shAvailable=%i updateSHistory=%i updateGHistory=%i"
+           " equalURI=%i\n",
+           shAvailable, updateSHistory, updateGHistory, equalUri));
+#endif
+
+  /* If the url to be loaded is the same as the one already there,
+   * and the original loadType is LOAD_NORMAL, LOAD_LINK, or
+   * LOAD_STOP_CONTENT, set loadType to LOAD_NORMAL_REPLACE so that
+   * AddToSessionHistory() won't mess with the current SHEntry and
+   * if this page has any frame children, it also will be handled
+   * properly. see bug 83684
+   *
+   * NB: If mOSHE is null but we have a current URI, then it probably
+   * means that we must be at the transient about:blank content viewer;
+   * we should let the normal load continue, since there's nothing to
+   * replace. Sometimes this happens after a session restore (eg process
+   * switch) and mCurrentURI is not about:blank; we assume we can let the load
+   * continue (Bug 1301399).
+   *
+   * XXX Hopefully changing the loadType at this time will not hurt
+   *  anywhere. The other way to take care of sequentially repeating
+   *  frameset pages is to add new methods to nsIDocShellTreeItem.
+   * Hopefully I don't have to do that.
+   */
+  if (equalUri &&
+      (mozilla::SessionHistoryInParent() ? !!mActiveEntry : !!mOSHE) &&
+      (mLoadType == LOAD_NORMAL || mLoadType == LOAD_LINK ||
+       mLoadType == LOAD_STOP_CONTENT) &&
+      !inputStream) {
+    mLoadType = LOAD_NORMAL_REPLACE;
+  }
+
+  // If this is a refresh to the currently loaded url, we don't
+  // have to update session or global history.
+  if (mLoadType == LOAD_REFRESH && !inputStream && equalUri) {
+    SetHistoryEntryAndUpdateBC(Some<nsISHEntry*>(mOSHE), Nothing());
+  }
+
+  /* If the user pressed shift-reload, cache will create a new cache key
+   * for the page. Save the new cacheKey in Session History.
+   * see bug 90098
+   */
+  if (aChannel && IsForceReloadType(mLoadType)) {
+    MOZ_ASSERT(!updateSHistory || IsSubframe(),
+               "We shouldn't be updating session history for forced"
+               " reloads unless we're in a newly created iframe!");
+
+    nsCOMPtr<nsICacheInfoChannel> cacheChannel(do_QueryInterface(aChannel));
+    uint32_t cacheKey = 0;
+    // Get the Cache Key and store it in SH.
+    if (cacheChannel) {
+      cacheChannel->GetCacheKey(&cacheKey);
+    }
+    // If we already have a loading history entry, store the new cache key
+    // in it.  Otherwise, since we're doing a reload and won't be updating
+    // our history entry, store the cache key in our current history entry.
+    SetCacheKeyOnHistoryEntry(mLSHE ? mLSHE : mOSHE, cacheKey);
+
+    if (!mozilla::SessionHistoryInParent()) {
+      // Since we're force-reloading, clear all the sub frame history.
+      ClearFrameHistory(mLSHE);
+      ClearFrameHistory(mOSHE);
+    }
+  }
+
+  if (!mozilla::SessionHistoryInParent()) {
+    // Clear subframe history on refresh.
+    // XXX: history.go(0) won't go this path as mLoadType is LOAD_HISTORY in
+    // this case. One should re-validate after bug 1331865 fixed.
+    if (mLoadType == LOAD_REFRESH) {
+      ClearFrameHistory(mLSHE);
+      ClearFrameHistory(mOSHE);
+    }
+
+    if (updateSHistory) {
+      // Update session history if necessary...
+      if (!mLSHE && (mItemType == typeContent) && mURIResultedInDocument) {
+        /* This is  a fresh page getting loaded for the first time
+         *.Create a Entry for it and add it to SH, if this is the
+         * rootDocShell
+         */
+        (void)AddToSessionHistory(aURI, aChannel, aTriggeringPrincipal,
+                                  aPrincipalToInherit,
+                                  aPartitionedPrincipalToInherit, aCsp,
+                                  aCloneSHChildren, getter_AddRefs(mLSHE));
+      }
+    } else if (GetSessionHistory() && mLSHE && mURIResultedInDocument) {
+      // Even if we don't add anything to SHistory, ensure the current index
+      // points to the same SHEntry as our mLSHE.
+
+      GetSessionHistory()->LegacySHistory()->EnsureCorrectEntryAtCurrIndex(
+          mLSHE);
+    }
+  }
+
+  // If this is a POST request, we do not want to include this in global
+  // history.
+  if (ShouldAddURIVisit(aChannel) && updateGHistory && aAddToGlobalHistory &&
+      !net::ChannelIsPost(aChannel)) {
+    nsCOMPtr<nsIURI> previousURI;
+    uint32_t previousFlags = 0;
+
+    if (mLoadType & LOAD_CMD_RELOAD) {
+      // On a reload request, we don't set redirecting flags.
+      previousURI = aURI;
+    } else {
+      ExtractLastVisit(aChannel, getter_AddRefs(previousURI), &previousFlags);
+    }
+
+    AddURIVisit(aURI, previousURI, previousFlags, responseStatus);
+  }
+
+  // If this was a history load or a refresh, or it was a history load but
+  // later changed to LOAD_NORMAL_REPLACE due to redirection, update the index
+  // in session history.
+  if (!mozilla::SessionHistoryInParent() && rootSH &&
+      ((mLoadType & (LOAD_CMD_HISTORY | LOAD_CMD_RELOAD)) ||
+       mLoadType == LOAD_NORMAL_REPLACE || mLoadType == LOAD_REFRESH_REPLACE)) {
+    mPreviousEntryIndex = rootSH->Index();
+    if (!mozilla::SessionHistoryInParent()) {
+      rootSH->LegacySHistory()->UpdateIndex();
+    }
+    mLoadedEntryIndex = rootSH->Index();
+    MOZ_LOG(gPageCacheLog, LogLevel::Verbose,
+            ("Previous index: %d, Loaded index: %d", mPreviousEntryIndex,
+             mLoadedEntryIndex));
+  }
+
+  // aCloneSHChildren exactly means "we are not loading a new document".
+  uint32_t locationFlags =
+      aCloneSHChildren ? uint32_t(LOCATION_CHANGE_SAME_DOCUMENT) : 0;
+
+  bool onLocationChangeNeeded =
+      SetCurrentURI(aURI, aChannel, false,
+                    /* aIsInitialAboutBlank */ false, locationFlags);
+  // Make sure to store the referrer from the channel, if any
+  nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(aChannel));
+  if (httpChannel) {
+    mReferrerInfo = httpChannel->GetReferrerInfo();
+  }
+  return onLocationChangeNeeded;
+}
+
+Maybe<Wireframe> nsDocShell::GetWireframe() {
+  const bool collectWireFrame =
+      mozilla::SessionHistoryInParent() &&
+      StaticPrefs::browser_history_collectWireframes() &&
+      mBrowsingContext->IsTopContent() && mActiveEntry;
+
+  if (!collectWireFrame) {
+    return Nothing();
+  }
+
+  RefPtr<Document> doc = mDocumentViewer->GetDocument();
+  Nullable<Wireframe> wireframe;
+  doc->GetWireframeWithoutFlushing(false, wireframe);
+  if (wireframe.IsNull()) {
+    return Nothing();
+  }
+  return Some(wireframe.Value());
+}
+
+bool nsDocShell::CollectWireframe() {
+  Maybe<Wireframe> wireframe = GetWireframe();
+  if (wireframe.isNothing()) {
+    return false;
+  }
+
+  if (XRE_IsParentProcess()) {
+    SessionHistoryEntry* entry =
+        mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+    if (entry) {
+      entry->SetWireframe(wireframe);
+    }
+  } else {
+    mozilla::Unused
+        << ContentChild::GetSingleton()->SendSessionHistoryEntryWireframe(
+               mBrowsingContext, wireframe.ref());
+  }
+
+  return true;
+}
+
+//*****************************************************************************
+// nsDocShell: Session History
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::AddState(JS::Handle<JS::Value> aData, const nsAString& aTitle,
+                     const nsAString& aURL, bool aReplace, JSContext* aCx) {
+  MOZ_LOG(gSHLog, LogLevel::Debug,
+          ("nsDocShell[%p]: AddState(..., %s, %s, %d)", this,
+           NS_ConvertUTF16toUTF8(aTitle).get(),
+           NS_ConvertUTF16toUTF8(aURL).get(), aReplace));
+  // Implements History.pushState and History.replaceState
+
+  // Here's what we do, roughly in the order specified by HTML5.  The specific
+  // steps we are executing are at
+  // <https://html.spec.whatwg.org/multipage/history.html#dom-history-pushstate>
+  // and
+  // <https://html.spec.whatwg.org/multipage/history.html#url-and-history-update-steps>.
+  // This function basically implements #dom-history-pushstate and
+  // UpdateURLAndHistory implements #url-and-history-update-steps.
+  //
+  // A. Serialize aData using structured clone.  This is #dom-history-pushstate
+  //    step 5.
+  // B. If the third argument is present, #dom-history-pushstate step 7.
+  //     7.1. Resolve the url, relative to our document.
+  //     7.2. If (a) fails, raise a SECURITY_ERR
+  //     7.4. Compare the resulting absolute URL to the document's address.  If
+  //          any part of the URLs difer other than the <path>, <query>, and
+  //          <fragment> components, raise a SECURITY_ERR and abort.
+  // C. If !aReplace, #url-and-history-update-steps steps 2.1-2.3:
+  //     Remove from the session history all entries after the current entry,
+  //     as we would after a regular navigation, and save the current
+  //     entry's scroll position (bug 590573).
+  // D. #url-and-history-update-steps step 2.4 or step 3.  As apropriate,
+  //    either add a state object entry to the session history after the
+  //    current entry with the following properties, or modify the current
+  //    session history entry to set
+  //      a. cloned data as the state object,
+  //      b. if the third argument was present, the absolute URL found in
+  //         step 2
+  //    Also clear the new history entry's POST data (see bug 580069).
+  // E. If aReplace is false (i.e. we're doing a pushState instead of a
+  //    replaceState), notify bfcache that we've navigated to a new page.
+  // F. If the third argument is present, set the document's current address
+  //    to the absolute URL found in step B.  This is
+  //    #url-and-history-update-steps step 4.
+  //
+  // It's important that this function not run arbitrary scripts after step A
+  // and before completing step E.  For example, if a script called
+  // history.back() before we completed step E, bfcache might destroy an
+  // active content viewer.  Since EvictOutOfRangeDocumentViewers at the end of
+  // step E might run script, we can't just put a script blocker around the
+  // critical section.
+  //
+  // Note that we completely ignore the aTitle parameter.
+
+  nsresult rv;
+
+  // Don't clobber the load type of an existing network load.
+  AutoRestore<uint32_t> loadTypeResetter(mLoadType);
+
+  // pushState effectively becomes replaceState when we've started a network
+  // load but haven't adopted its document yet.  This mirrors what we do with
+  // changes to the hash at this stage of the game.
+  if (JustStartedNetworkLoad()) {
+    aReplace = true;
+  }
+
+  RefPtr<Document> document = GetDocument();
+  NS_ENSURE_TRUE(document, NS_ERROR_FAILURE);
+
+  // Step A: Serialize aData using structured clone.
+  // https://html.spec.whatwg.org/multipage/history.html#dom-history-pushstate
+  // step 5.
+  nsCOMPtr<nsIStructuredCloneContainer> scContainer;
+
+  // scContainer->Init might cause arbitrary JS to run, and this code might
+  // navigate the page we're on, potentially to a different origin! (bug
+  // 634834)  To protect against this, we abort if our principal changes due
+  // to the InitFromJSVal() call.
+  {
+    RefPtr<Document> origDocument = GetDocument();
+    if (!origDocument) {
+      return NS_ERROR_DOM_SECURITY_ERR;
+    }
+    nsCOMPtr<nsIPrincipal> origPrincipal = origDocument->NodePrincipal();
+
+    scContainer = new nsStructuredCloneContainer();
+    rv = scContainer->InitFromJSVal(aData, aCx);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    RefPtr<Document> newDocument = GetDocument();
+    if (!newDocument) {
+      return NS_ERROR_DOM_SECURITY_ERR;
+    }
+    nsCOMPtr<nsIPrincipal> newPrincipal = newDocument->NodePrincipal();
+
+    bool principalsEqual = false;
+    origPrincipal->Equals(newPrincipal, &principalsEqual);
+    NS_ENSURE_TRUE(principalsEqual, NS_ERROR_DOM_SECURITY_ERR);
+  }
+
+  // Check that the state object isn't too long.
+  int32_t maxStateObjSize = StaticPrefs::browser_history_maxStateObjectSize();
+  if (maxStateObjSize < 0) {
+    maxStateObjSize = 0;
+  }
+
+  uint64_t scSize;
+  rv = scContainer->GetSerializedNBytes(&scSize);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  NS_ENSURE_TRUE(scSize <= (uint32_t)maxStateObjSize, NS_ERROR_ILLEGAL_VALUE);
+
+  // Step B: Resolve aURL.
+  // https://html.spec.whatwg.org/multipage/history.html#dom-history-pushstate
+  // step 7.
+  bool equalURIs = true;
+  nsCOMPtr<nsIURI> currentURI;
+  if (mCurrentURI) {
+    currentURI = nsIOService::CreateExposableURI(mCurrentURI);
+  } else {
+    currentURI = mCurrentURI;
+  }
+  nsCOMPtr<nsIURI> newURI;
+  if (aURL.Length() == 0) {
+    newURI = currentURI;
+  } else {
+    // 7.1: Resolve aURL relative to mURI
+
+    nsIURI* docBaseURI = document->GetDocBaseURI();
+    if (!docBaseURI) {
+      return NS_ERROR_FAILURE;
+    }
+
+    nsAutoCString spec;
+    docBaseURI->GetSpec(spec);
+
+    rv = NS_NewURI(getter_AddRefs(newURI), aURL,
+                   document->GetDocumentCharacterSet(), docBaseURI);
+
+    // 7.2: If 2a fails, raise a SECURITY_ERR
+    if (NS_FAILED(rv)) {
+      return NS_ERROR_DOM_SECURITY_ERR;
+    }
+
+    // 7.4 and 7.5: Same-origin check.
+    if (!nsContentUtils::URIIsLocalFile(newURI)) {
+      // In addition to checking that the security manager says that
+      // the new URI has the same origin as our current URI, we also
+      // check that the two URIs have the same userpass. (The
+      // security manager says that |http://foo.com| and
+      // |http://me@foo.com| have the same origin.)  currentURI
+      // won't contain the password part of the userpass, so this
+      // means that it's never valid to specify a password in a
+      // pushState or replaceState URI.
+
+      nsCOMPtr<nsIScriptSecurityManager> secMan =
+          do_GetService(NS_SCRIPTSECURITYMANAGER_CONTRACTID);
+      NS_ENSURE_TRUE(secMan, NS_ERROR_FAILURE);
+
+      // It's very important that we check that newURI is of the same
+      // origin as currentURI, not docBaseURI, because a page can
+      // set docBaseURI arbitrarily to any domain.
+      nsAutoCString currentUserPass, newUserPass;
+      NS_ENSURE_SUCCESS(currentURI->GetUserPass(currentUserPass),
+                        NS_ERROR_FAILURE);
+      NS_ENSURE_SUCCESS(newURI->GetUserPass(newUserPass), NS_ERROR_FAILURE);
+      bool isPrivateWin =
+          document->NodePrincipal()->OriginAttributesRef().mPrivateBrowsingId >
+          0;
+      if (NS_FAILED(secMan->CheckSameOriginURI(currentURI, newURI, true,
+                                               isPrivateWin)) ||
+          !currentUserPass.Equals(newUserPass)) {
+        return NS_ERROR_DOM_SECURITY_ERR;
+      }
+    } else {
+      // It's a file:// URI
+      nsCOMPtr<nsIPrincipal> principal = document->GetPrincipal();
+
+      if (!principal || NS_FAILED(principal->CheckMayLoadWithReporting(
+                            newURI, false, document->InnerWindowID()))) {
+        return NS_ERROR_DOM_SECURITY_ERR;
+      }
+    }
+
+    if (currentURI) {
+      currentURI->Equals(newURI, &equalURIs);
+    } else {
+      equalURIs = false;
+    }
+
+  }  // end of same-origin check
+
+  // Step 8: call "URL and history update steps"
+  rv = UpdateURLAndHistory(document, newURI, scContainer, aTitle, aReplace,
+                           currentURI, equalURIs);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+nsresult nsDocShell::UpdateURLAndHistory(Document* aDocument, nsIURI* aNewURI,
+                                         nsIStructuredCloneContainer* aData,
+                                         const nsAString& aTitle, bool aReplace,
+                                         nsIURI* aCurrentURI, bool aEqualURIs) {
+  // Implements
+  // https://html.spec.whatwg.org/multipage/history.html#url-and-history-update-steps
+
+  // If we have a pending title change, handle it before creating a new entry.
+  aDocument->DoNotifyPossibleTitleChange();
+
+  // Step 2, if aReplace is false: Create a new entry in the session
+  // history. This will erase all SHEntries after the new entry and make this
+  // entry the current one.  This operation may modify mOSHE, which we need
+  // later, so we keep a reference here.
+  NS_ENSURE_TRUE(mOSHE || mActiveEntry || aReplace, NS_ERROR_FAILURE);
+  nsCOMPtr<nsISHEntry> oldOSHE = mOSHE;
+
+  // If this push/replaceState changed the document's current URI and the new
+  // URI differs from the old URI in more than the hash, or if the old
+  // SHEntry's URI was modified in this way by a push/replaceState call
+  // set URIWasModified to true for the current SHEntry (bug 669671).
+  bool sameExceptHashes = true;
+  aNewURI->EqualsExceptRef(aCurrentURI, &sameExceptHashes);
+  bool uriWasModified;
+  if (sameExceptHashes) {
+    if (mozilla::SessionHistoryInParent()) {
+      uriWasModified = mActiveEntry && mActiveEntry->GetURIWasModified();
+    } else {
+      uriWasModified = oldOSHE && oldOSHE->GetURIWasModified();
+    }
+  } else {
+    uriWasModified = true;
+  }
+
+  mLoadType = LOAD_PUSHSTATE;
+
+  nsCOMPtr<nsISHEntry> newSHEntry;
+  if (!aReplace) {
+    // Step 2.
+
+    // Step 2.2, "Remove any tasks queued by the history traversal task
+    // source that are associated with any Document objects in the
+    // top-level browsing context's document family."  This is very hard in
+    // SessionHistoryInParent since we can't synchronously access the
+    // pending navigations that are already sent to the parent. We can
+    // abort any AsyncGo navigations that are waiting to be sent.  If we
+    // send a message to the parent, it would be processed after any
+    // navigations previously sent.  So long as we consider the "history
+    // traversal task source" to be the list in this process we match the
+    // spec.  If we move the entire list to the parent, we can handle the
+    // aborting of loads there, but we don't have a way to synchronously
+    // remove entries as we do here for non-SHIP.
+    RefPtr<ChildSHistory> shistory = GetRootSessionHistory();
+    if (shistory) {
+      shistory->RemovePendingHistoryNavigations();
+    }
+
+    nsPoint scrollPos = GetCurScrollPos();
+
+    bool scrollRestorationIsManual;
+    if (mozilla::SessionHistoryInParent()) {
+      // FIXME Need to save the current scroll position on mActiveEntry.
+      scrollRestorationIsManual = mActiveEntry->GetScrollRestorationIsManual();
+    } else {
+      // Save the current scroll position (bug 590573).  Step 2.3.
+      mOSHE->SetScrollPosition(scrollPos.x, scrollPos.y);
+
+      scrollRestorationIsManual = mOSHE->GetScrollRestorationIsManual();
+    }
+
+    nsCOMPtr<nsIContentSecurityPolicy> csp = aDocument->GetCsp();
+
+    if (mozilla::SessionHistoryInParent()) {
+      MOZ_LOG(gSHLog, LogLevel::Debug,
+              ("nsDocShell %p UpdateActiveEntry (not replacing)", this));
+      nsString title(mActiveEntry->GetTitle());
+      UpdateActiveEntry(false,
+                        /* aPreviousScrollPos = */ Some(scrollPos), aNewURI,
+                        /* aOriginalURI = */ nullptr,
+                        /* aReferrerInfo = */ nullptr,
+                        /* aTriggeringPrincipal = */ aDocument->NodePrincipal(),
+                        csp, title, scrollRestorationIsManual, aData,
+                        uriWasModified);
+    } else {
+      // Since we're not changing which page we have loaded, pass
+      // true for aCloneChildren.
+      nsresult rv = AddToSessionHistory(
+          aNewURI, nullptr,
+          aDocument->NodePrincipal(),  // triggeringPrincipal
+          nullptr, nullptr, csp, true, getter_AddRefs(newSHEntry));
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      NS_ENSURE_TRUE(newSHEntry, NS_ERROR_FAILURE);
+
+      // Session history entries created by pushState inherit scroll restoration
+      // mode from the current entry.
+      newSHEntry->SetScrollRestorationIsManual(scrollRestorationIsManual);
+
+      nsString title;
+      mOSHE->GetTitle(title);
+
+      // Set the new SHEntry's title (bug 655273).
+      newSHEntry->SetTitle(title);
+
+      // Link the new SHEntry to the old SHEntry's BFCache entry, since the
+      // two entries correspond to the same document.
+      NS_ENSURE_SUCCESS(newSHEntry->AdoptBFCacheEntry(oldOSHE),
+                        NS_ERROR_FAILURE);
+
+      // AddToSessionHistory may not modify mOSHE.  In case it doesn't,
+      // we'll just set mOSHE here.
+      mOSHE = newSHEntry;
+    }
+  } else if (mozilla::SessionHistoryInParent()) {
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("nsDocShell %p UpdateActiveEntry (replacing) mActiveEntry %p",
+             this, mActiveEntry.get()));
+    // Setting the resultPrincipalURI to nullptr is fine here: it will cause
+    // NS_GetFinalChannelURI to use the originalURI as the URI, which is aNewURI
+    // in our case.  We could also set it to aNewURI, with the same result.
+    // We don't use aTitle here, see bug 544535.
+    nsString title;
+    nsCOMPtr<nsIReferrerInfo> referrerInfo;
+    if (mActiveEntry) {
+      title = mActiveEntry->GetTitle();
+      referrerInfo = mActiveEntry->GetReferrerInfo();
+    } else {
+      referrerInfo = nullptr;
+    }
+    UpdateActiveEntry(
+        true, /* aPreviousScrollPos = */ Nothing(), aNewURI, aNewURI,
+        /* aReferrerInfo = */ referrerInfo, aDocument->NodePrincipal(),
+        aDocument->GetCsp(), title,
+        mActiveEntry && mActiveEntry->GetScrollRestorationIsManual(), aData,
+        uriWasModified);
+  } else {
+    // Step 3.
+    newSHEntry = mOSHE;
+
+    MOZ_LOG(gSHLog, LogLevel::Debug, ("nsDocShell %p step 3", this));
+    // Since we're not changing which page we have loaded, pass
+    // true for aCloneChildren.
+    if (!newSHEntry) {
+      nsresult rv = AddToSessionHistory(
+          aNewURI, nullptr,
+          aDocument->NodePrincipal(),  // triggeringPrincipal
+          nullptr, nullptr, aDocument->GetCsp(), true,
+          getter_AddRefs(newSHEntry));
+      NS_ENSURE_SUCCESS(rv, rv);
+      mOSHE = newSHEntry;
+    }
+
+    newSHEntry->SetURI(aNewURI);
+    newSHEntry->SetOriginalURI(aNewURI);
+    // We replaced the URI of the entry, clear the unstripped URI as it
+    // shouldn't be used for reloads anymore.
+    newSHEntry->SetUnstrippedURI(nullptr);
+    // Setting the resultPrincipalURI to nullptr is fine here: it will cause
+    // NS_GetFinalChannelURI to use the originalURI as the URI, which is aNewURI
+    // in our case.  We could also set it to aNewURI, with the same result.
+    newSHEntry->SetResultPrincipalURI(nullptr);
+    newSHEntry->SetLoadReplace(false);
+  }
+
+  if (!mozilla::SessionHistoryInParent()) {
+    // Step 2.4 and 3: Modify new/original session history entry and clear its
+    // POST data, if there is any.
+    newSHEntry->SetStateData(aData);
+    newSHEntry->SetPostData(nullptr);
+
+    newSHEntry->SetURIWasModified(uriWasModified);
+
+    // Step E as described at the top of AddState: If aReplace is false,
+    // indicating that we're doing a pushState rather than a replaceState,
+    // notify bfcache that we've added a page to the history so it can evict
+    // content viewers if appropriate. Otherwise call ReplaceEntry so that we
+    // notify nsIHistoryListeners that an entry was replaced.  We may not have a
+    // root session history if this call is coming from a document.open() in a
+    // docshell subtree that disables session history.
+    RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
+    if (rootSH) {
+      rootSH->LegacySHistory()->EvictDocumentViewersOrReplaceEntry(newSHEntry,
+                                                                   aReplace);
+    }
+  }
+
+  // Step 4: If the document's URI changed, update document's URI and update
+  // global history.
+  //
+  // We need to call FireOnLocationChange so that the browser's address bar
+  // gets updated and the back button is enabled, but we only need to
+  // explicitly call FireOnLocationChange if we're not calling SetCurrentURI,
+  // since SetCurrentURI will call FireOnLocationChange for us.
+  //
+  // Both SetCurrentURI(...) and FireDummyOnLocationChange() pass
+  // nullptr for aRequest param to FireOnLocationChange(...). Such an update
+  // notification is allowed only when we know docshell is not loading a new
+  // document and it requires LOCATION_CHANGE_SAME_DOCUMENT flag. Otherwise,
+  // FireOnLocationChange(...) breaks security UI.
+  //
+  // If the docshell is shutting down, don't update the document URI, as we
+  // can't load into a docshell that is being destroyed.
+  if (!aEqualURIs && !mIsBeingDestroyed) {
+    aDocument->SetDocumentURI(aNewURI);
+    SetCurrentURI(aNewURI, nullptr, /* aFireLocationChange */ true,
+                  /* aIsInitialAboutBlank */ false,
+                  GetSameDocumentNavigationFlags(aNewURI));
+
+    AddURIVisit(aNewURI, aCurrentURI, 0);
+
+    // AddURIVisit doesn't set the title for the new URI in global history,
+    // so do that here.
+    UpdateGlobalHistoryTitle(aNewURI);
+
+    // Inform the favicon service that our old favicon applies to this new
+    // URI.
+    CopyFavicon(aCurrentURI, aNewURI, UsePrivateBrowsing());
+  } else {
+    FireDummyOnLocationChange();
+  }
+  aDocument->SetStateObject(aData);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetCurrentScrollRestorationIsManual(bool* aIsManual) {
+  if (mozilla::SessionHistoryInParent()) {
+    *aIsManual = mActiveEntry && mActiveEntry->GetScrollRestorationIsManual();
+    return NS_OK;
+  }
+
+  *aIsManual = false;
+  if (mOSHE) {
+    return mOSHE->GetScrollRestorationIsManual(aIsManual);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetCurrentScrollRestorationIsManual(bool aIsManual) {
+  SetScrollRestorationIsManualOnHistoryEntry(mOSHE, aIsManual);
+
+  return NS_OK;
+}
+
+void nsDocShell::SetScrollRestorationIsManualOnHistoryEntry(
+    nsISHEntry* aSHEntry, bool aIsManual) {
+  if (aSHEntry) {
+    aSHEntry->SetScrollRestorationIsManual(aIsManual);
+  }
+
+  if (mActiveEntry && mBrowsingContext) {
+    mActiveEntry->SetScrollRestorationIsManual(aIsManual);
+    if (XRE_IsParentProcess()) {
+      SessionHistoryEntry* entry =
+          mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+      if (entry) {
+        entry->SetScrollRestorationIsManual(aIsManual);
+      }
+    } else {
+      mozilla::Unused << ContentChild::GetSingleton()
+                             ->SendSessionHistoryEntryScrollRestorationIsManual(
+                                 mBrowsingContext, aIsManual);
+    }
+  }
+}
+
+void nsDocShell::SetCacheKeyOnHistoryEntry(nsISHEntry* aSHEntry,
+                                           uint32_t aCacheKey) {
+  if (aSHEntry) {
+    aSHEntry->SetCacheKey(aCacheKey);
+  }
+
+  if (mActiveEntry && mBrowsingContext) {
+    mActiveEntry->SetCacheKey(aCacheKey);
+    if (XRE_IsParentProcess()) {
+      SessionHistoryEntry* entry =
+          mBrowsingContext->Canonical()->GetActiveSessionHistoryEntry();
+      if (entry) {
+        entry->SetCacheKey(aCacheKey);
+      }
+    } else {
+      mozilla::Unused
+          << ContentChild::GetSingleton()->SendSessionHistoryEntryCacheKey(
+                 mBrowsingContext, aCacheKey);
+    }
+  }
+}
+
+/* static */
+bool nsDocShell::ShouldAddToSessionHistory(nsIURI* aURI, nsIChannel* aChannel) {
+  // I believe none of the about: urls should go in the history. But then
+  // that could just be me... If the intent is only deny about:blank then we
+  // should just do a spec compare, rather than two gets of the scheme and
+  // then the path.  -Gagan
+  nsresult rv;
+  nsAutoCString buf;
+
+  rv = aURI->GetScheme(buf);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  if (buf.EqualsLiteral("about")) {
+    rv = aURI->GetPathQueryRef(buf);
+    if (NS_FAILED(rv)) {
+      return false;
+    }
+
+    if (buf.EqualsLiteral("blank")) {
+      return false;
+    }
+    // We only want to add about:newtab if it's not privileged, and
+    // if it is not configured to show the blank page.
+    if (buf.EqualsLiteral("newtab")) {
+      if (!StaticPrefs::browser_newtabpage_enabled()) {
+        return false;
+      }
+
+      NS_ENSURE_TRUE(aChannel, false);
+      nsCOMPtr<nsIPrincipal> resultPrincipal;
+      rv = nsContentUtils::GetSecurityManager()->GetChannelResultPrincipal(
+          aChannel, getter_AddRefs(resultPrincipal));
+      NS_ENSURE_SUCCESS(rv, false);
+      return !resultPrincipal->IsSystemPrincipal();
+    }
+  }
+
+  return true;
+}
+
+nsresult nsDocShell::AddToSessionHistory(
+    nsIURI* aURI, nsIChannel* aChannel, nsIPrincipal* aTriggeringPrincipal,
+    nsIPrincipal* aPrincipalToInherit,
+    nsIPrincipal* aPartitionedPrincipalToInherit,
+    nsIContentSecurityPolicy* aCsp, bool aCloneChildren,
+    nsISHEntry** aNewEntry) {
+  MOZ_ASSERT(aURI, "uri is null");
+  MOZ_ASSERT(!aChannel || !aTriggeringPrincipal, "Shouldn't have both set");
+  MOZ_DIAGNOSTIC_ASSERT(!mozilla::SessionHistoryInParent());
+
+#if defined(DEBUG)
+  if (MOZ_LOG_TEST(gDocShellLog, LogLevel::Debug)) {
+    nsAutoCString chanName;
+    if (aChannel) {
+      aChannel->GetName(chanName);
+    } else {
+      chanName.AssignLiteral("<no channel>");
+    }
+
+    MOZ_LOG(gDocShellLog, LogLevel::Debug,
+            ("nsDocShell[%p]::AddToSessionHistory(\"%s\", [%s])\n", this,
+             aURI->GetSpecOrDefault().get(), chanName.get()));
+  }
+#endif
+
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsISHEntry> entry;
+
+  /*
+   * If this is a LOAD_FLAGS_REPLACE_HISTORY in a subframe, we use
+   * the existing SH entry in the page and replace the url and
+   * other vitalities.
+   */
+  if (LOAD_TYPE_HAS_FLAGS(mLoadType, LOAD_FLAGS_REPLACE_HISTORY) &&
+      !mBrowsingContext->IsTop()) {
+    // This is a subframe
+    entry = mOSHE;
+    if (entry) {
+      entry->ClearEntry();
+    }
+  }
+
+  // Create a new entry if necessary.
+  if (!entry) {
+    entry = new nsSHEntry();
+  }
+
+  // Get the post data & referrer
+  nsCOMPtr<nsIInputStream> inputStream;
+  nsCOMPtr<nsIURI> originalURI;
+  nsCOMPtr<nsIURI> resultPrincipalURI;
+  nsCOMPtr<nsIURI> unstrippedURI;
+  bool loadReplace = false;
+  nsCOMPtr<nsIReferrerInfo> referrerInfo;
+  uint32_t cacheKey = 0;
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal = aTriggeringPrincipal;
+  nsCOMPtr<nsIPrincipal> principalToInherit = aPrincipalToInherit;
+  nsCOMPtr<nsIPrincipal> partitionedPrincipalToInherit =
+      aPartitionedPrincipalToInherit;
+  nsCOMPtr<nsIContentSecurityPolicy> csp = aCsp;
+  bool expired = false;  // by default the page is not expired
+  bool discardLayoutState = false;
+  nsCOMPtr<nsICacheInfoChannel> cacheChannel;
+  bool userActivation = false;
+
+  if (aChannel) {
+    cacheChannel = do_QueryInterface(aChannel);
+
+    /* If there is a caching channel, get the Cache Key and store it
+     * in SH.
+     */
+    if (cacheChannel) {
+      cacheChannel->GetCacheKey(&cacheKey);
+    }
+    nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(aChannel));
+
+    // Check if the httpChannel is hiding under a multipartChannel
+    if (!httpChannel) {
+      GetHttpChannel(aChannel, getter_AddRefs(httpChannel));
+    }
+    if (httpChannel) {
+      nsCOMPtr<nsIUploadChannel> uploadChannel(do_QueryInterface(httpChannel));
+      if (uploadChannel) {
+        uploadChannel->GetUploadStream(getter_AddRefs(inputStream));
+      }
+      httpChannel->GetOriginalURI(getter_AddRefs(originalURI));
+      uint32_t loadFlags;
+      aChannel->GetLoadFlags(&loadFlags);
+      loadReplace = loadFlags & nsIChannel::LOAD_REPLACE;
+      rv = httpChannel->GetReferrerInfo(getter_AddRefs(referrerInfo));
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+      discardLayoutState = ShouldDiscardLayoutState(httpChannel);
+    }
+
+    nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
+    if (!triggeringPrincipal) {
+      triggeringPrincipal = loadInfo->TriggeringPrincipal();
+    }
+    if (!csp) {
+      csp = loadInfo->GetCspToInherit();
+    }
+
+    loadInfo->GetResultPrincipalURI(getter_AddRefs(resultPrincipalURI));
+
+    loadInfo->GetUnstrippedURI(getter_AddRefs(unstrippedURI));
+
+    userActivation = loadInfo->GetHasValidUserGestureActivation();
+
+    // For now keep storing just the principal in the SHEntry.
+    if (!principalToInherit) {
+      if (loadInfo->GetLoadingSandboxed()) {
+        if (loadInfo->GetLoadingPrincipal()) {
+          principalToInherit = NullPrincipal::CreateWithInheritedAttributes(
+              loadInfo->GetLoadingPrincipal());
+        } else {
+          // get the OriginAttributes
+          OriginAttributes attrs;
+          loadInfo->GetOriginAttributes(&attrs);
+          principalToInherit = NullPrincipal::Create(attrs);
+        }
+      } else {
+        principalToInherit = loadInfo->PrincipalToInherit();
+      }
+    }
+
+    if (!partitionedPrincipalToInherit) {
+      // XXXehsan is it correct to fall back to the principal to inherit in all
+      // cases?  For example, what about the cases where we are using the load
+      // info's principal to inherit?  Do we need to add a similar concept to
+      // load info for partitioned principal?
+      partitionedPrincipalToInherit = principalToInherit;
+    }
+  }
+
+  nsAutoString srcdoc;
+  bool srcdocEntry = false;
+  nsCOMPtr<nsIURI> baseURI;
+
+  nsCOMPtr<nsIInputStreamChannel> inStrmChan = do_QueryInterface(aChannel);
+  if (inStrmChan) {
+    bool isSrcdocChannel;
+    inStrmChan->GetIsSrcdocChannel(&isSrcdocChannel);
+    if (isSrcdocChannel) {
+      inStrmChan->GetSrcdocData(srcdoc);
+      srcdocEntry = true;
+      inStrmChan->GetBaseURI(getter_AddRefs(baseURI));
+    } else {
+      srcdoc.SetIsVoid(true);
+    }
+  }
+  /* If cache got a 'no-store', ask SH not to store
+   * HistoryLayoutState. By default, SH will set this
+   * flag to true and save HistoryLayoutState.
+   */
+  bool saveLayoutState = !discardLayoutState;
+
+  if (cacheChannel) {
+    // Check if the page has expired from cache
+    uint32_t expTime = 0;
+    cacheChannel->GetCacheTokenExpirationTime(&expTime);
+    uint32_t now = PRTimeToSeconds(PR_Now());
+    if (expTime <= now) {
+      expired = true;
+    }
+  }
+
+  // Title is set in nsDocShell::SetTitle()
+  entry->Create(aURI,                 // uri
+                u""_ns,               // Title
+                inputStream,          // Post data stream
+                cacheKey,             // CacheKey
+                mContentTypeHint,     // Content-type
+                triggeringPrincipal,  // Channel or provided principal
+                principalToInherit, partitionedPrincipalToInherit, csp,
+                HistoryID(), GetCreatedDynamically(), originalURI,
+                resultPrincipalURI, unstrippedURI, loadReplace, referrerInfo,
+                srcdoc, srcdocEntry, baseURI, saveLayoutState, expired,
+                userActivation);
+
+  if (mBrowsingContext->IsTop() && GetSessionHistory()) {
+    bool shouldPersist = ShouldAddToSessionHistory(aURI, aChannel);
+    Maybe<int32_t> previousEntryIndex;
+    Maybe<int32_t> loadedEntryIndex;
+    rv = GetSessionHistory()->LegacySHistory()->AddToRootSessionHistory(
+        aCloneChildren, mOSHE, mBrowsingContext, entry, mLoadType,
+        shouldPersist, &previousEntryIndex, &loadedEntryIndex);
+
+    MOZ_ASSERT(NS_SUCCEEDED(rv), "Could not add entry to root session history");
+    if (previousEntryIndex.isSome()) {
+      mPreviousEntryIndex = previousEntryIndex.value();
+    }
+    if (loadedEntryIndex.isSome()) {
+      mLoadedEntryIndex = loadedEntryIndex.value();
+    }
+
+    // aCloneChildren implies that we are retaining the same document, thus we
+    // need to signal to the top WC that the new SHEntry may receive a fresh
+    // user interaction flag.
+    if (aCloneChildren) {
+      WindowContext* topWc = mBrowsingContext->GetTopWindowContext();
+      if (topWc && !topWc->IsDiscarded()) {
+        MOZ_ALWAYS_SUCCEEDS(topWc->SetSHEntryHasUserInteraction(false));
+      }
+    }
+  } else {
+    // This is a subframe, make sure that this new SHEntry will be
+    // marked with user interaction.
+    WindowContext* topWc = mBrowsingContext->GetTopWindowContext();
+    if (topWc && !topWc->IsDiscarded()) {
+      MOZ_ALWAYS_SUCCEEDS(topWc->SetSHEntryHasUserInteraction(false));
+    }
+    if (!mOSHE || !LOAD_TYPE_HAS_FLAGS(mLoadType, LOAD_FLAGS_REPLACE_HISTORY)) {
+      rv = AddChildSHEntryToParent(entry, mBrowsingContext->ChildOffset(),
+                                   aCloneChildren);
+    }
+  }
+
+  // Return the new SH entry...
+  if (aNewEntry) {
+    *aNewEntry = nullptr;
+    if (NS_SUCCEEDED(rv)) {
+      entry.forget(aNewEntry);
+    }
+  }
+
+  return rv;
+}
+
+void nsDocShell::UpdateActiveEntry(
+    bool aReplace, const Maybe<nsPoint>& aPreviousScrollPos, nsIURI* aURI,
+    nsIURI* aOriginalURI, nsIReferrerInfo* aReferrerInfo,
+    nsIPrincipal* aTriggeringPrincipal, nsIContentSecurityPolicy* aCsp,
+    const nsAString& aTitle, bool aScrollRestorationIsManual,
+    nsIStructuredCloneContainer* aData, bool aURIWasModified) {
+  MOZ_ASSERT(mozilla::SessionHistoryInParent());
+  MOZ_ASSERT(aURI, "uri is null");
+  MOZ_ASSERT(mLoadType == LOAD_PUSHSTATE,
+             "This code only deals with pushState");
+  MOZ_ASSERT_IF(aPreviousScrollPos.isSome(), !aReplace);
+
+  MOZ_LOG(gSHLog, LogLevel::Debug,
+          ("Creating an active entry on nsDocShell %p to %s", this,
+           aURI->GetSpecOrDefault().get()));
+
+  // Even if we're replacing an existing entry we create new a
+  // SessionHistoryInfo. In the parent process we'll keep the existing
+  // SessionHistoryEntry, but just replace its SessionHistoryInfo, that way the
+  // entry keeps identity but its data is replaced.
+  bool replace = aReplace && mActiveEntry;
+
+  if (!replace) {
+    CollectWireframe();
+  }
+
+  if (mActiveEntry) {
+    // Link this entry to the previous active entry.
+    mActiveEntry = MakeUnique<SessionHistoryInfo>(*mActiveEntry, aURI);
+  } else {
+    mActiveEntry = MakeUnique<SessionHistoryInfo>(
+        aURI, aTriggeringPrincipal, nullptr, nullptr, aCsp, mContentTypeHint);
+  }
+  mActiveEntry->SetOriginalURI(aOriginalURI);
+  mActiveEntry->SetUnstrippedURI(nullptr);
+  mActiveEntry->SetReferrerInfo(aReferrerInfo);
+  mActiveEntry->SetTitle(aTitle);
+  mActiveEntry->SetStateData(static_cast<nsStructuredCloneContainer*>(aData));
+  mActiveEntry->SetURIWasModified(aURIWasModified);
+  mActiveEntry->SetScrollRestorationIsManual(aScrollRestorationIsManual);
+
+  if (replace) {
+    mBrowsingContext->ReplaceActiveSessionHistoryEntry(mActiveEntry.get());
+  } else {
+    mBrowsingContext->IncrementHistoryEntryCountForBrowsingContext();
+    // FIXME We should probably just compute mChildOffset in the parent
+    //       instead of passing it over IPC here.
+    mBrowsingContext->SetActiveSessionHistoryEntry(
+        aPreviousScrollPos, mActiveEntry.get(), mLoadType,
+        /* aCacheKey = */ 0);
+    // FIXME Do we need to update mPreviousEntryIndex and mLoadedEntryIndex?
+  }
+}
+
+nsresult nsDocShell::LoadHistoryEntry(nsISHEntry* aEntry, uint32_t aLoadType,
+                                      bool aUserActivation) {
+  NS_ENSURE_TRUE(aEntry, NS_ERROR_FAILURE);
+
+  nsresult rv;
+  RefPtr<nsDocShellLoadState> loadState;
+  rv = aEntry->CreateLoadInfo(getter_AddRefs(loadState));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Calling CreateAboutBlankDocumentViewer can set mOSHE to null, and if
+  // that's the only thing holding a ref to aEntry that will cause aEntry to
+  // die while we're loading it.  So hold a strong ref to aEntry here, just
+  // in case.
+  nsCOMPtr<nsISHEntry> kungFuDeathGrip(aEntry);
+
+  loadState->SetHasValidUserGestureActivation(
+      loadState->HasValidUserGestureActivation() || aUserActivation);
+
+  return LoadHistoryEntry(loadState, aLoadType, aEntry == mOSHE);
+}
+
+nsresult nsDocShell::LoadHistoryEntry(const LoadingSessionHistoryInfo& aEntry,
+                                      uint32_t aLoadType,
+                                      bool aUserActivation) {
+  RefPtr<nsDocShellLoadState> loadState = aEntry.CreateLoadInfo();
+  loadState->SetHasValidUserGestureActivation(
+      loadState->HasValidUserGestureActivation() || aUserActivation);
+
+  return LoadHistoryEntry(loadState, aLoadType, aEntry.mLoadingCurrentEntry);
+}
+
+nsresult nsDocShell::LoadHistoryEntry(nsDocShellLoadState* aLoadState,
+                                      uint32_t aLoadType,
+                                      bool aLoadingCurrentEntry) {
+  if (!IsNavigationAllowed()) {
+    return NS_OK;
+  }
+
+  // We are setting load type afterwards so we don't have to
+  // send it in an IPC message
+  aLoadState->SetLoadType(aLoadType);
+
+  nsresult rv;
+  if (SchemeIsJavascript(aLoadState->URI())) {
+    // We're loading a URL that will execute script from inside asyncOpen.
+    // Replace the current document with about:blank now to prevent
+    // anything from the current document from leaking into any JavaScript
+    // code in the URL.
+    // Don't cache the presentation if we're going to just reload the
+    // current entry. Caching would lead to trying to save the different
+    // content viewers in the same nsISHEntry object.
+    rv = CreateAboutBlankDocumentViewer(
+        aLoadState->PrincipalToInherit(),
+        aLoadState->PartitionedPrincipalToInherit(), nullptr, nullptr,
+        /* aIsInitialDocument */ false, Nothing(), !aLoadingCurrentEntry);
+
+    if (NS_FAILED(rv)) {
+      // The creation of the intermittent about:blank content
+      // viewer failed for some reason (potentially because the
+      // user prevented it). Interrupt the history load.
+      return NS_OK;
+    }
+
+    if (!aLoadState->TriggeringPrincipal()) {
+      // Ensure that we have a triggeringPrincipal.  Otherwise javascript:
+      // URIs will pick it up from the about:blank page we just loaded,
+      // and we don't really want even that in this case.
+      nsCOMPtr<nsIPrincipal> principal =
+          NullPrincipal::Create(GetOriginAttributes());
+      aLoadState->SetTriggeringPrincipal(principal);
+    }
+  }
+
+  /* If there is a valid postdata *and* the user pressed
+   * reload or shift-reload, take user's permission before we
+   * repost the data to the server.
+   */
+  if ((aLoadType & LOAD_CMD_RELOAD) && aLoadState->PostDataStream()) {
+    bool repost;
+    rv = ConfirmRepost(&repost);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    // If the user pressed cancel in the dialog, return.  We're done here.
+    if (!repost) {
+      return NS_BINDING_ABORTED;
+    }
+  }
+
+  // If there is no valid triggeringPrincipal, we deny the load
+  MOZ_ASSERT(aLoadState->TriggeringPrincipal(),
+             "need a valid triggeringPrincipal to load from history");
+  if (!aLoadState->TriggeringPrincipal()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return InternalLoad(aLoadState);  // No nsIRequest
+}
+
+NS_IMETHODIMP
+nsDocShell::PersistLayoutHistoryState() {
+  nsresult rv = NS_OK;
+
+  if (mozilla::SessionHistoryInParent() ? !!mActiveEntry : !!mOSHE) {
+    bool scrollRestorationIsManual;
+    if (mozilla::SessionHistoryInParent()) {
+      scrollRestorationIsManual = mActiveEntry->GetScrollRestorationIsManual();
+    } else {
+      scrollRestorationIsManual = mOSHE->GetScrollRestorationIsManual();
+    }
+    nsCOMPtr<nsILayoutHistoryState> layoutState;
+    if (RefPtr<PresShell> presShell = GetPresShell()) {
+      rv = presShell->CaptureHistoryState(getter_AddRefs(layoutState));
+    } else if (scrollRestorationIsManual) {
+      // Even if we don't have layout anymore, we may want to reset the
+      // current scroll state in layout history.
+      GetLayoutHistoryState(getter_AddRefs(layoutState));
+    }
+
+    if (scrollRestorationIsManual && layoutState) {
+      layoutState->ResetScrollState();
+    }
+  }
+
+  return rv;
+}
+
+void nsDocShell::SwapHistoryEntries(nsISHEntry* aOldEntry,
+                                    nsISHEntry* aNewEntry) {
+  if (aOldEntry == mOSHE) {
+    mOSHE = aNewEntry;
+  }
+
+  if (aOldEntry == mLSHE) {
+    mLSHE = aNewEntry;
+  }
+}
+
+void nsDocShell::SetHistoryEntryAndUpdateBC(const Maybe<nsISHEntry*>& aLSHE,
+                                            const Maybe<nsISHEntry*>& aOSHE) {
+  // We want to hold on to the reference in mLSHE before we update it.
+  // Otherwise, SetHistoryEntry could release the last reference to
+  // the entry while aOSHE is pointing to it.
+  nsCOMPtr<nsISHEntry> deathGripOldLSHE;
+  if (aLSHE.isSome()) {
+    deathGripOldLSHE = SetHistoryEntry(&mLSHE, aLSHE.value());
+    MOZ_ASSERT(mLSHE.get() == aLSHE.value());
+  }
+  nsCOMPtr<nsISHEntry> deathGripOldOSHE;
+  if (aOSHE.isSome()) {
+    deathGripOldOSHE = SetHistoryEntry(&mOSHE, aOSHE.value());
+    MOZ_ASSERT(mOSHE.get() == aOSHE.value());
+  }
+}
+
+already_AddRefed<nsISHEntry> nsDocShell::SetHistoryEntry(
+    nsCOMPtr<nsISHEntry>* aPtr, nsISHEntry* aEntry) {
+  // We need to sync up the docshell and session history trees for
+  // subframe navigation.  If the load was in a subframe, we forward up to
+  // the root docshell, which will then recursively sync up all docshells
+  // to their corresponding entries in the new session history tree.
+  // If we don't do this, then we can cache a content viewer on the wrong
+  // cloned entry, and subsequently restore it at the wrong time.
+  RefPtr<BrowsingContext> topBC = mBrowsingContext->Top();
+  if (topBC->IsDiscarded()) {
+    topBC = nullptr;
+  }
+  RefPtr<BrowsingContext> currBC =
+      mBrowsingContext->IsDiscarded() ? nullptr : mBrowsingContext;
+  if (topBC && *aPtr) {
+    (*aPtr)->SyncTreesForSubframeNavigation(aEntry, topBC, currBC);
+  }
+  nsCOMPtr<nsISHEntry> entry(aEntry);
+  entry.swap(*aPtr);
+  return entry.forget();
+}
+
+already_AddRefed<ChildSHistory> nsDocShell::GetRootSessionHistory() {
+  RefPtr<ChildSHistory> childSHistory =
+      mBrowsingContext->Top()->GetChildSessionHistory();
+  return childSHistory.forget();
+}
+
+nsresult nsDocShell::GetHttpChannel(nsIChannel* aChannel,
+                                    nsIHttpChannel** aReturn) {
+  NS_ENSURE_ARG_POINTER(aReturn);
+  if (!aChannel) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIMultiPartChannel> multiPartChannel(do_QueryInterface(aChannel));
+  if (multiPartChannel) {
+    nsCOMPtr<nsIChannel> baseChannel;
+    multiPartChannel->GetBaseChannel(getter_AddRefs(baseChannel));
+    nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(baseChannel));
+    *aReturn = httpChannel;
+    NS_IF_ADDREF(*aReturn);
+  }
+  return NS_OK;
+}
+
+bool nsDocShell::ShouldDiscardLayoutState(nsIHttpChannel* aChannel) {
+  // By default layout State will be saved.
+  if (!aChannel) {
+    return false;
+  }
+
+  // figure out if SH should be saving layout state
+  bool noStore = false;
+  Unused << aChannel->IsNoStoreResponse(&noStore);
+  return noStore;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetEditor(nsIEditor** aEditor) {
+  NS_ENSURE_ARG_POINTER(aEditor);
+  RefPtr<HTMLEditor> htmlEditor = GetHTMLEditorInternal();
+  htmlEditor.forget(aEditor);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetEditor(nsIEditor* aEditor) {
+  HTMLEditor* htmlEditor = aEditor ? aEditor->GetAsHTMLEditor() : nullptr;
+  // If TextEditor comes, throw an error.
+  if (aEditor && !htmlEditor) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  return SetHTMLEditorInternal(htmlEditor);
+}
+
+HTMLEditor* nsDocShell::GetHTMLEditorInternal() {
+  return mEditorData ? mEditorData->GetHTMLEditor() : nullptr;
+}
+
+nsresult nsDocShell::SetHTMLEditorInternal(HTMLEditor* aHTMLEditor) {
+  if (!aHTMLEditor && !mEditorData) {
+    return NS_OK;
+  }
+
+  nsresult rv = EnsureEditorData();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  return mEditorData->SetHTMLEditor(aHTMLEditor);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetEditable(bool* aEditable) {
+  NS_ENSURE_ARG_POINTER(aEditable);
+  *aEditable = mEditorData && mEditorData->GetEditable();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetHasEditingSession(bool* aHasEditingSession) {
+  NS_ENSURE_ARG_POINTER(aHasEditingSession);
+
+  if (mEditorData) {
+    *aHasEditingSession = !!mEditorData->GetEditingSession();
+  } else {
+    *aHasEditingSession = false;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::MakeEditable(bool aInWaitForUriLoad) {
+  nsresult rv = EnsureEditorData();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  return mEditorData->MakeEditable(aInWaitForUriLoad);
+}
+
+/* static */ bool nsDocShell::ShouldAddURIVisit(nsIChannel* aChannel) {
+  bool needToAddURIVisit = true;
+  nsCOMPtr<nsIPropertyBag2> props(do_QueryInterface(aChannel));
+  if (props) {
+    mozilla::Unused << props->GetPropertyAsBool(
+        u"docshell.needToAddURIVisit"_ns, &needToAddURIVisit);
+  }
+
+  return needToAddURIVisit;
+}
+
+/* static */ void nsDocShell::ExtractLastVisit(
+    nsIChannel* aChannel, nsIURI** aURI, uint32_t* aChannelRedirectFlags) {
+  nsCOMPtr<nsIPropertyBag2> props(do_QueryInterface(aChannel));
+  if (!props) {
+    return;
+  }
+
+  nsresult rv;
+  nsCOMPtr<nsIURI> uri(do_GetProperty(props, u"docshell.previousURI"_ns, &rv));
+  if (NS_SUCCEEDED(rv)) {
+    uri.forget(aURI);
+
+    rv = props->GetPropertyAsUint32(u"docshell.previousFlags"_ns,
+                                    aChannelRedirectFlags);
+
+    NS_WARNING_ASSERTION(
+        NS_SUCCEEDED(rv),
+        "Could not fetch previous flags, URI will be treated like referrer");
+
+  } else {
+    // There is no last visit for this channel, so this must be the first
+    // link.  Link the visit to the referrer of this request, if any.
+    // Treat referrer as null if there is an error getting it.
+    NS_GetReferrerFromChannel(aChannel, aURI);
+  }
+}
+
+void nsDocShell::SaveLastVisit(nsIChannel* aChannel, nsIURI* aURI,
+                               uint32_t aChannelRedirectFlags) {
+  nsCOMPtr<nsIWritablePropertyBag2> props(do_QueryInterface(aChannel));
+  if (!props || !aURI) {
+    return;
+  }
+
+  props->SetPropertyAsInterface(u"docshell.previousURI"_ns, aURI);
+  props->SetPropertyAsUint32(u"docshell.previousFlags"_ns,
+                             aChannelRedirectFlags);
+}
+
+/* static */ void nsDocShell::InternalAddURIVisit(
+    nsIURI* aURI, nsIURI* aPreviousURI, uint32_t aChannelRedirectFlags,
+    uint32_t aResponseStatus, BrowsingContext* aBrowsingContext,
+    nsIWidget* aWidget, uint32_t aLoadType, bool aWasUpgraded) {
+  MOZ_ASSERT(aURI, "Visited URI is null!");
+  MOZ_ASSERT(aLoadType != LOAD_ERROR_PAGE && aLoadType != LOAD_BYPASS_HISTORY,
+             "Do not add error or bypass pages to global history");
+
+  bool usePrivateBrowsing = false;
+  aBrowsingContext->GetUsePrivateBrowsing(&usePrivateBrowsing);
+
+  // Only content-type docshells save URI visits.  Also don't do
+  // anything here if we're not supposed to use global history.
+  if (!aBrowsingContext->IsContent() ||
+      !aBrowsingContext->GetUseGlobalHistory() || usePrivateBrowsing) {
+    return;
+  }
+
+  nsCOMPtr<IHistory> history = components::History::Service();
+
+  if (history) {
+    uint32_t visitURIFlags = 0;
+
+    if (aBrowsingContext->IsTop()) {
+      visitURIFlags |= IHistory::TOP_LEVEL;
+    }
+
+    if (aChannelRedirectFlags & nsIChannelEventSink::REDIRECT_TEMPORARY) {
+      visitURIFlags |= IHistory::REDIRECT_TEMPORARY;
+    } else if (aChannelRedirectFlags &
+               nsIChannelEventSink::REDIRECT_PERMANENT) {
+      visitURIFlags |= IHistory::REDIRECT_PERMANENT;
+    } else {
+      MOZ_ASSERT(!aChannelRedirectFlags,
+                 "One of REDIRECT_TEMPORARY or REDIRECT_PERMANENT must be set "
+                 "if any flags in aChannelRedirectFlags is set.");
+    }
+
+    if (aResponseStatus >= 300 && aResponseStatus < 400) {
+      visitURIFlags |= IHistory::REDIRECT_SOURCE;
+      if (aResponseStatus == 301 || aResponseStatus == 308) {
+        visitURIFlags |= IHistory::REDIRECT_SOURCE_PERMANENT;
+      }
+    }
+    // Errors 400-501 and 505 are considered unrecoverable, in the sense a
+    // simple retry attempt by the user is unlikely to solve them.
+    // 408 is special cased, since may actually indicate a temporary
+    // connection problem.
+    else if (aResponseStatus != 408 &&
+             ((aResponseStatus >= 400 && aResponseStatus <= 501) ||
+              aResponseStatus == 505)) {
+      visitURIFlags |= IHistory::UNRECOVERABLE_ERROR;
+    }
+
+    if (aWasUpgraded) {
+      visitURIFlags |=
+          IHistory::REDIRECT_SOURCE | IHistory::REDIRECT_SOURCE_UPGRADED;
+    }
+
+    mozilla::Unused << history->VisitURI(aWidget, aURI, aPreviousURI,
+                                         visitURIFlags,
+                                         aBrowsingContext->BrowserId());
+  }
+}
+
+void nsDocShell::AddURIVisit(nsIURI* aURI, nsIURI* aPreviousURI,
+                             uint32_t aChannelRedirectFlags,
+                             uint32_t aResponseStatus) {
+  nsPIDOMWindowOuter* outer = GetWindow();
+  nsCOMPtr<nsIWidget> widget = widget::WidgetUtils::DOMWindowToWidget(outer);
+
+  InternalAddURIVisit(aURI, aPreviousURI, aChannelRedirectFlags,
+                      aResponseStatus, mBrowsingContext, widget, mLoadType,
+                      false);
+}
+
+//*****************************************************************************
+// nsDocShell: Helper Routines
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::SetLoadType(uint32_t aLoadType) {
+  mLoadType = aLoadType;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetLoadType(uint32_t* aLoadType) {
+  *aLoadType = mLoadType;
+  return NS_OK;
+}
+
+nsresult nsDocShell::ConfirmRepost(bool* aRepost) {
+  if (StaticPrefs::dom_confirm_repost_testing_always_accept()) {
+    *aRepost = true;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIPromptCollection> prompter =
+      do_GetService("@mozilla.org/embedcomp/prompt-collection;1");
+  if (!prompter) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return prompter->ConfirmRepost(mBrowsingContext, aRepost);
+}
+
+nsresult nsDocShell::GetPromptAndStringBundle(nsIPrompt** aPrompt,
+                                              nsIStringBundle** aStringBundle) {
+  NS_ENSURE_SUCCESS(GetInterface(NS_GET_IID(nsIPrompt), (void**)aPrompt),
+                    NS_ERROR_FAILURE);
+
+  nsCOMPtr<nsIStringBundleService> stringBundleService =
+      mozilla::components::StringBundle::Service();
+  NS_ENSURE_TRUE(stringBundleService, NS_ERROR_FAILURE);
+
+  NS_ENSURE_SUCCESS(
+      stringBundleService->CreateBundle(kAppstringsBundleURL, aStringBundle),
+      NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+nsIScrollableFrame* nsDocShell::GetRootScrollFrame() {
+  PresShell* presShell = GetPresShell();
+  NS_ENSURE_TRUE(presShell, nullptr);
+
+  return presShell->GetRootScrollFrameAsScrollable();
+}
+
+nsresult nsDocShell::EnsureScriptEnvironment() {
+  if (mScriptGlobal) {
+    return NS_OK;
+  }
+
+  if (mIsBeingDestroyed) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+#ifdef DEBUG
+  NS_ASSERTION(!mInEnsureScriptEnv,
+               "Infinite loop! Calling EnsureScriptEnvironment() from "
+               "within EnsureScriptEnvironment()!");
+
+  // Yeah, this isn't re-entrant safe, but that's ok since if we
+  // re-enter this method, we'll infinitely loop...
+  AutoRestore<bool> boolSetter(mInEnsureScriptEnv);
+  mInEnsureScriptEnv = true;
+#endif
+
+  nsCOMPtr<nsIWebBrowserChrome> browserChrome(do_GetInterface(mTreeOwner));
+  NS_ENSURE_TRUE(browserChrome, NS_ERROR_NOT_AVAILABLE);
+
+  uint32_t chromeFlags;
+  browserChrome->GetChromeFlags(&chromeFlags);
+
+  // If our window is modal and we're not opened as chrome, make
+  // this window a modal content window.
+  mScriptGlobal = nsGlobalWindowOuter::Create(this, mItemType == typeChrome);
+  MOZ_ASSERT(mScriptGlobal);
+
+  // Ensure the script object is set up to run script.
+  return mScriptGlobal->EnsureScriptEnvironment();
+}
+
+nsresult nsDocShell::EnsureEditorData() {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+
+  bool openDocHasDetachedEditor = mOSHE && mOSHE->HasDetachedEditor();
+  if (!mEditorData && !mIsBeingDestroyed && !openDocHasDetachedEditor) {
+    // We shouldn't recreate the editor data if it already exists, or
+    // we're shutting down, or we already have a detached editor data
+    // stored in the session history. We should only have one editordata
+    // per docshell.
+    mEditorData = MakeUnique<nsDocShellEditorData>(this);
+  }
+
+  return mEditorData ? NS_OK : NS_ERROR_NOT_AVAILABLE;
+}
+
+nsresult nsDocShell::EnsureFind() {
+  if (!mFind) {
+    mFind = new nsWebBrowserFind();
+  }
+
+  // we promise that the nsIWebBrowserFind that we return has been set
+  // up to point to the focused, or content window, so we have to
+  // set that up each time.
+
+  nsIScriptGlobalObject* scriptGO = GetScriptGlobalObject();
+  NS_ENSURE_TRUE(scriptGO, NS_ERROR_UNEXPECTED);
+
+  // default to our window
+  nsCOMPtr<nsPIDOMWindowOuter> ourWindow = do_QueryInterface(scriptGO);
+  nsCOMPtr<nsPIDOMWindowOuter> windowToSearch;
+  nsFocusManager::GetFocusedDescendant(ourWindow,
+                                       nsFocusManager::eIncludeAllDescendants,
+                                       getter_AddRefs(windowToSearch));
+
+  nsCOMPtr<nsIWebBrowserFindInFrames> findInFrames = do_QueryInterface(mFind);
+  if (!findInFrames) {
+    return NS_ERROR_NO_INTERFACE;
+  }
+
+  nsresult rv = findInFrames->SetRootSearchFrame(ourWindow);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  rv = findInFrames->SetCurrentSearchFrame(windowToSearch);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::IsBeingDestroyed(bool* aDoomed) {
+  NS_ENSURE_ARG(aDoomed);
+  *aDoomed = mIsBeingDestroyed;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetIsExecutingOnLoadHandler(bool* aResult) {
+  NS_ENSURE_ARG(aResult);
+  *aResult = mIsExecutingOnLoadHandler;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetLayoutHistoryState(nsILayoutHistoryState** aLayoutHistoryState) {
+  nsCOMPtr<nsILayoutHistoryState> state;
+  if (mozilla::SessionHistoryInParent()) {
+    if (mActiveEntry) {
+      state = mActiveEntry->GetLayoutHistoryState();
+    }
+  } else {
+    if (mOSHE) {
+      state = mOSHE->GetLayoutHistoryState();
+    }
+  }
+  state.forget(aLayoutHistoryState);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetLayoutHistoryState(nsILayoutHistoryState* aLayoutHistoryState) {
+  if (mOSHE) {
+    mOSHE->SetLayoutHistoryState(aLayoutHistoryState);
+  }
+  if (mActiveEntry) {
+    mActiveEntry->SetLayoutHistoryState(aLayoutHistoryState);
+  }
+  return NS_OK;
+}
+
+nsDocShell::InterfaceRequestorProxy::InterfaceRequestorProxy(
+    nsIInterfaceRequestor* aRequestor) {
+  if (aRequestor) {
+    mWeakPtr = do_GetWeakReference(aRequestor);
+  }
+}
+
+nsDocShell::InterfaceRequestorProxy::~InterfaceRequestorProxy() {
+  mWeakPtr = nullptr;
+}
+
+NS_IMPL_ISUPPORTS(nsDocShell::InterfaceRequestorProxy, nsIInterfaceRequestor)
+
+NS_IMETHODIMP
+nsDocShell::InterfaceRequestorProxy::GetInterface(const nsIID& aIID,
+                                                  void** aSink) {
+  NS_ENSURE_ARG_POINTER(aSink);
+  nsCOMPtr<nsIInterfaceRequestor> ifReq = do_QueryReferent(mWeakPtr);
+  if (ifReq) {
+    return ifReq->GetInterface(aIID, aSink);
+  }
+  *aSink = nullptr;
+  return NS_NOINTERFACE;
+}
+
+//*****************************************************************************
+// nsDocShell::nsIAuthPromptProvider
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::GetAuthPrompt(uint32_t aPromptReason, const nsIID& aIID,
+                          void** aResult) {
+  // a priority prompt request will override a false mAllowAuth setting
+  bool priorityPrompt = (aPromptReason == PROMPT_PROXY);
+
+  if (!mAllowAuth && !priorityPrompt) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // we're either allowing auth, or it's a proxy request
+  nsresult rv;
+  nsCOMPtr<nsIPromptFactory> wwatch =
+      do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = EnsureScriptEnvironment();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Get the an auth prompter for our window so that the parenting
+  // of the dialogs works as it should when using tabs.
+
+  return wwatch->GetPrompt(mScriptGlobal, aIID,
+                           reinterpret_cast<void**>(aResult));
+}
+
+//*****************************************************************************
+// nsDocShell::nsILoadContext
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShell::GetAssociatedWindow(mozIDOMWindowProxy** aWindow) {
+  CallGetInterface(this, aWindow);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetTopWindow(mozIDOMWindowProxy** aWindow) {
+  return mBrowsingContext->GetTopWindow(aWindow);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetTopFrameElement(Element** aElement) {
+  return mBrowsingContext->GetTopFrameElement(aElement);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetUseTrackingProtection(bool* aUseTrackingProtection) {
+  return mBrowsingContext->GetUseTrackingProtection(aUseTrackingProtection);
+}
+
+NS_IMETHODIMP
+nsDocShell::SetUseTrackingProtection(bool aUseTrackingProtection) {
+  return mBrowsingContext->SetUseTrackingProtection(aUseTrackingProtection);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetIsContent(bool* aIsContent) {
+  *aIsContent = (mItemType == typeContent);
+  return NS_OK;
+}
+
+bool nsDocShell::IsOKToLoadURI(nsIURI* aURI) {
+  MOZ_ASSERT(aURI, "Must have a URI!");
+
+  if (!mFiredUnloadEvent) {
+    return true;
+  }
+
+  if (!mLoadingURI) {
+    return false;
+  }
+
+  bool isPrivateWin = false;
+  Document* doc = GetDocument();
+  if (doc) {
+    isPrivateWin =
+        doc->NodePrincipal()->OriginAttributesRef().mPrivateBrowsingId > 0;
+  }
+
+  nsCOMPtr<nsIScriptSecurityManager> secMan =
+      do_GetService(NS_SCRIPTSECURITYMANAGER_CONTRACTID);
+  return secMan && NS_SUCCEEDED(secMan->CheckSameOriginURI(
+                       aURI, mLoadingURI, false, isPrivateWin));
+}
+
+//
+// Routines for selection and clipboard
+//
+nsresult nsDocShell::GetControllerForCommand(const char* aCommand,
+                                             nsIController** aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+  *aResult = nullptr;
+
+  NS_ENSURE_TRUE(mScriptGlobal, NS_ERROR_FAILURE);
+
+  nsCOMPtr<nsPIWindowRoot> root = mScriptGlobal->GetTopWindowRoot();
+  NS_ENSURE_TRUE(root, NS_ERROR_FAILURE);
+
+  return root->GetControllerForCommand(aCommand, false /* for any window */,
+                                       aResult);
+}
+
+NS_IMETHODIMP
+nsDocShell::IsCommandEnabled(const char* aCommand, bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+  *aResult = false;
+
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIController> controller;
+  rv = GetControllerForCommand(aCommand, getter_AddRefs(controller));
+  if (controller) {
+    rv = controller->IsCommandEnabled(aCommand, aResult);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocShell::DoCommand(const char* aCommand) {
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIController> controller;
+  rv = GetControllerForCommand(aCommand, getter_AddRefs(controller));
+  if (controller) {
+    rv = controller->DoCommand(aCommand);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocShell::DoCommandWithParams(const char* aCommand,
+                                nsICommandParams* aParams) {
+  nsCOMPtr<nsIController> controller;
+  nsresult rv = GetControllerForCommand(aCommand, getter_AddRefs(controller));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsICommandController> commandController =
+      do_QueryInterface(controller, &rv);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return commandController->DoCommandWithParams(aCommand, aParams);
+}
+
+nsresult nsDocShell::EnsureCommandHandler() {
+  if (!mCommandManager) {
+    if (nsCOMPtr<nsPIDOMWindowOuter> domWindow = GetWindow()) {
+      mCommandManager = new nsCommandManager(domWindow);
+    }
+  }
+  return mCommandManager ? NS_OK : NS_ERROR_FAILURE;
+}
+
+// link handling
+
+class OnLinkClickEvent : public Runnable {
+ public:
+  OnLinkClickEvent(nsDocShell* aHandler, nsIContent* aContent,
+                   nsDocShellLoadState* aLoadState, bool aNoOpenerImplied,
+                   bool aIsTrusted, nsIPrincipal* aTriggeringPrincipal);
+
+  NS_IMETHOD Run() override {
+    AutoPopupStatePusher popupStatePusher(mPopupState);
+
+    // We need to set up an AutoJSAPI here for the following reason: When we
+    // do OnLinkClickSync we'll eventually end up in
+    // nsGlobalWindow::OpenInternal which only does popup blocking if
+    // !LegacyIsCallerChromeOrNativeCode(). So we need to fake things so that
+    // we don't look like native code as far as LegacyIsCallerNativeCode() is
+    // concerned.
+    AutoJSAPI jsapi;
+    if (mIsTrusted || jsapi.Init(mContent->OwnerDoc()->GetScopeObject())) {
+      mHandler->OnLinkClickSync(mContent, mLoadState, mNoOpenerImplied,
+                                mTriggeringPrincipal);
+    }
+    return NS_OK;
+  }
+
+ private:
+  RefPtr<nsDocShell> mHandler;
+  nsCOMPtr<nsIContent> mContent;
+  RefPtr<nsDocShellLoadState> mLoadState;
+  nsCOMPtr<nsIPrincipal> mTriggeringPrincipal;
+  PopupBlocker::PopupControlState mPopupState;
+  bool mNoOpenerImplied;
+  bool mIsTrusted;
+};
+
+OnLinkClickEvent::OnLinkClickEvent(nsDocShell* aHandler, nsIContent* aContent,
+                                   nsDocShellLoadState* aLoadState,
+                                   bool aNoOpenerImplied, bool aIsTrusted,
+                                   nsIPrincipal* aTriggeringPrincipal)
+    : mozilla::Runnable("OnLinkClickEvent"),
+      mHandler(aHandler),
+      mContent(aContent),
+      mLoadState(aLoadState),
+      mTriggeringPrincipal(aTriggeringPrincipal),
+      mPopupState(PopupBlocker::GetPopupControlState()),
+      mNoOpenerImplied(aNoOpenerImplied),
+      mIsTrusted(aIsTrusted) {}
+
+nsresult nsDocShell::OnLinkClick(
+    nsIContent* aContent, nsIURI* aURI, const nsAString& aTargetSpec,
+    const nsAString& aFileName, nsIInputStream* aPostDataStream,
+    nsIInputStream* aHeadersDataStream, bool aIsUserTriggered, bool aIsTrusted,
+    nsIPrincipal* aTriggeringPrincipal, nsIContentSecurityPolicy* aCsp) {
+#ifndef ANDROID
+  MOZ_ASSERT(aTriggeringPrincipal, "Need a valid triggeringPrincipal");
+#endif
+  NS_ASSERTION(NS_IsMainThread(), "wrong thread");
+
+  if (!IsNavigationAllowed() || !IsOKToLoadURI(aURI)) {
+    return NS_OK;
+  }
+
+  // On history navigation through Back/Forward buttons, don't execute
+  // automatic JavaScript redirection such as |anchorElement.click()| or
+  // |formElement.submit()|.
+  //
+  // XXX |formElement.submit()| bypasses this checkpoint because it calls
+  //     nsDocShell::OnLinkClickSync(...) instead.
+  if (ShouldBlockLoadingForBackButton()) {
+    return NS_OK;
+  }
+
+  if (aContent->IsEditable()) {
+    return NS_OK;
+  }
+
+  Document* ownerDoc = aContent->OwnerDoc();
+  if (nsContentUtils::IsExternalProtocol(aURI)) {
+    ownerDoc->EnsureNotEnteringAndExitFullscreen();
+  }
+
+  bool noOpenerImplied = false;
+  nsAutoString target(aTargetSpec);
+  if (aFileName.IsVoid() &&
+      ShouldOpenInBlankTarget(aTargetSpec, aURI, aContent, aIsUserTriggered)) {
+    target = u"_blank";
+    if (!aTargetSpec.Equals(target)) {
+      noOpenerImplied = true;
+    }
+  }
+
+  RefPtr<nsDocShellLoadState> loadState = new nsDocShellLoadState(aURI);
+  loadState->SetTarget(target);
+  loadState->SetFileName(aFileName);
+  loadState->SetPostDataStream(aPostDataStream);
+  loadState->SetHeadersStream(aHeadersDataStream);
+  loadState->SetFirstParty(true);
+  loadState->SetTriggeringPrincipal(
+      aTriggeringPrincipal ? aTriggeringPrincipal : aContent->NodePrincipal());
+  loadState->SetPrincipalToInherit(aContent->NodePrincipal());
+  loadState->SetCsp(aCsp ? aCsp : aContent->GetCsp());
+  loadState->SetAllowFocusMove(UserActivation::IsHandlingUserInput());
+
+  nsCOMPtr<nsIRunnable> ev =
+      new OnLinkClickEvent(this, aContent, loadState, noOpenerImplied,
+                           aIsTrusted, aTriggeringPrincipal);
+  return Dispatch(ev.forget());
+}
+
+bool nsDocShell::ShouldOpenInBlankTarget(const nsAString& aOriginalTarget,
+                                         nsIURI* aLinkURI, nsIContent* aContent,
+                                         bool aIsUserTriggered) {
+  if (net::SchemeIsJavascript(aLinkURI)) {
+    return false;
+  }
+
+  // External links from within app tabs should always open in new tabs
+  // instead of replacing the app tab's page (Bug 575561)
+  // nsIURI.host can throw for non-nsStandardURL nsIURIs. If we fail to
+  // get either host, just return false to use the original target.
+  nsAutoCString linkHost;
+  if (NS_FAILED(aLinkURI->GetHost(linkHost))) {
+    return false;
+  }
+
+  // The targetTopLevelLinkClicksToBlank property on BrowsingContext allows
+  // privileged code to change the default targeting behaviour. In particular,
+  // if a user-initiated link click for the (or targetting the) top-level frame
+  // is detected, we default the target to "_blank" to give it a new
+  // top-level BrowsingContext.
+  if (mBrowsingContext->TargetTopLevelLinkClicksToBlank() && aIsUserTriggered &&
+      ((aOriginalTarget.IsEmpty() && mBrowsingContext->IsTop()) ||
+       aOriginalTarget == u"_top"_ns)) {
+    return true;
+  }
+
+  // Don't modify non-default targets.
+  if (!aOriginalTarget.IsEmpty()) {
+    return false;
+  }
+
+  // Only check targets that are in extension panels or app tabs.
+  // (isAppTab will be false for app tab subframes).
+  nsString mmGroup = mBrowsingContext->Top()->GetMessageManagerGroup();
+  if (!mmGroup.EqualsLiteral("webext-browsers") &&
+      !mBrowsingContext->IsAppTab()) {
+    return false;
+  }
+
+  nsCOMPtr<nsIURI> docURI = aContent->OwnerDoc()->GetDocumentURIObject();
+  if (!docURI) {
+    return false;
+  }
+
+  nsAutoCString docHost;
+  if (NS_FAILED(docURI->GetHost(docHost))) {
+    return false;
+  }
+
+  if (linkHost.Equals(docHost)) {
+    return false;
+  }
+
+  // Special case: ignore "www" prefix if it is part of host string
+  return linkHost.Length() < docHost.Length()
+             ? !docHost.Equals("www."_ns + linkHost)
+             : !linkHost.Equals("www."_ns + docHost);
+}
+
+static bool ElementCanHaveNoopener(nsIContent* aContent) {
+  // Make sure we are dealing with either an <A>, <AREA>, or <FORM> element in
+  // the HTML, XHTML, or SVG namespace.
+  return aContent->IsAnyOfHTMLElements(nsGkAtoms::a, nsGkAtoms::area,
+                                       nsGkAtoms::form) ||
+         aContent->IsSVGElement(nsGkAtoms::a);
+}
+
+nsresult nsDocShell::OnLinkClickSync(nsIContent* aContent,
+                                     nsDocShellLoadState* aLoadState,
+                                     bool aNoOpenerImplied,
+                                     nsIPrincipal* aTriggeringPrincipal) {
+  if (!IsNavigationAllowed() || !IsOKToLoadURI(aLoadState->URI())) {
+    return NS_OK;
+  }
+
+  // XXX When the linking node was HTMLFormElement, it is synchronous event.
+  //     That is, the caller of this method is not |OnLinkClickEvent::Run()|
+  //     but |HTMLFormElement::SubmitSubmission(...)|.
+  if (aContent->IsHTMLElement(nsGkAtoms::form) &&
+      ShouldBlockLoadingForBackButton()) {
+    return NS_OK;
+  }
+
+  if (aContent->IsEditable()) {
+    return NS_OK;
+  }
+
+  // if the triggeringPrincipal is not passed explicitly, then we
+  // fall back to using doc->NodePrincipal() as the triggeringPrincipal.
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal =
+      aTriggeringPrincipal ? aTriggeringPrincipal : aContent->NodePrincipal();
+
+  {
+    // defer to an external protocol handler if necessary...
+    nsCOMPtr<nsIExternalProtocolService> extProtService =
+        do_GetService(NS_EXTERNALPROTOCOLSERVICE_CONTRACTID);
+    if (extProtService) {
+      nsAutoCString scheme;
+      aLoadState->URI()->GetScheme(scheme);
+      if (!scheme.IsEmpty()) {
+        // if the URL scheme does not correspond to an exposed protocol, then
+        // we need to hand this link click over to the external protocol
+        // handler.
+        bool isExposed;
+        nsresult rv =
+            extProtService->IsExposedProtocol(scheme.get(), &isExposed);
+        if (NS_SUCCEEDED(rv) && !isExposed) {
+          return extProtService->LoadURI(
+              aLoadState->URI(), triggeringPrincipal, nullptr, mBrowsingContext,
+              /* aTriggeredExternally */
+              false,
+              /* aHasValidUserGestureActivation */
+              aContent->OwnerDoc()->HasValidTransientUserGestureActivation());
+        }
+      }
+    }
+  }
+  uint32_t triggeringSandboxFlags = 0;
+  uint64_t triggeringWindowId = 0;
+  bool triggeringStorageAccess = false;
+  if (mBrowsingContext) {
+    triggeringSandboxFlags = aContent->OwnerDoc()->GetSandboxFlags();
+    triggeringWindowId = aContent->OwnerDoc()->InnerWindowID();
+    triggeringStorageAccess = aContent->OwnerDoc()->UsingStorageAccess();
+  }
+
+  uint32_t flags = INTERNAL_LOAD_FLAGS_NONE;
+  bool elementCanHaveNoopener = ElementCanHaveNoopener(aContent);
+  bool triggeringPrincipalIsSystemPrincipal =
+      aLoadState->TriggeringPrincipal()->IsSystemPrincipal();
+  if (elementCanHaveNoopener) {
+    MOZ_ASSERT(aContent->IsHTMLElement() || aContent->IsSVGElement());
+    nsAutoString relString;
+    aContent->AsElement()->GetAttr(nsGkAtoms::rel, relString);
+    nsWhitespaceTokenizerTemplate<nsContentUtils::IsHTMLWhitespace> tok(
+        relString);
+
+    bool targetBlank = aLoadState->Target().LowerCaseEqualsLiteral("_blank");
+    bool explicitOpenerSet = false;
+
+    // The opener behaviour follows a hierarchy, such that if a higher
+    // priority behaviour is specified, it always takes priority. That
+    // priority is currently: norefrerer > noopener > opener > default
+
+    while (tok.hasMoreTokens()) {
+      const nsAString& token = tok.nextToken();
+      if (token.LowerCaseEqualsLiteral("noreferrer")) {
+        flags |= INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER |
+                 INTERNAL_LOAD_FLAGS_NO_OPENER;
+        // noreferrer cannot be overwritten by a 'rel=opener'.
+        explicitOpenerSet = true;
+        break;
+      }
+
+      if (token.LowerCaseEqualsLiteral("noopener")) {
+        flags |= INTERNAL_LOAD_FLAGS_NO_OPENER;
+        explicitOpenerSet = true;
+      }
+
+      if (targetBlank && StaticPrefs::dom_targetBlankNoOpener_enabled() &&
+          token.LowerCaseEqualsLiteral("opener") && !explicitOpenerSet) {
+        explicitOpenerSet = true;
+      }
+    }
+
+    if (targetBlank && StaticPrefs::dom_targetBlankNoOpener_enabled() &&
+        !explicitOpenerSet && !triggeringPrincipalIsSystemPrincipal) {
+      flags |= INTERNAL_LOAD_FLAGS_NO_OPENER;
+    }
+
+    if (aNoOpenerImplied) {
+      flags |= INTERNAL_LOAD_FLAGS_NO_OPENER;
+    }
+  }
+
+  // Get the owner document of the link that was clicked, this will be
+  // the document that the link is in, or the last document that the
+  // link was in. From that document, we'll get the URI to use as the
+  // referrer, since the current URI in this docshell may be a
+  // new document that we're in the process of loading.
+  RefPtr<Document> referrerDoc = aContent->OwnerDoc();
+
+  // Now check that the referrerDoc's inner window is the current inner
+  // window for mScriptGlobal.  If it's not, then we don't want to
+  // follow this link.
+  nsPIDOMWindowInner* referrerInner = referrerDoc->GetInnerWindow();
+  if (!mScriptGlobal || !referrerInner ||
+      mScriptGlobal->GetCurrentInnerWindow() != referrerInner) {
+    // We're no longer the current inner window
+    return NS_OK;
+  }
+
+  // referrer could be null here in some odd cases, but that's ok,
+  // we'll just load the link w/o sending a referrer in those cases.
+
+  // If this is an anchor element, grab its type property to use as a hint
+  nsAutoString typeHint;
+  RefPtr<HTMLAnchorElement> anchor = HTMLAnchorElement::FromNode(aContent);
+  if (anchor) {
+    anchor->GetType(typeHint);
+    NS_ConvertUTF16toUTF8 utf8Hint(typeHint);
+    nsAutoCString type, dummy;
+    NS_ParseRequestContentType(utf8Hint, type, dummy);
+    CopyUTF8toUTF16(type, typeHint);
+  }
+
+  uint32_t loadType = LOAD_LINK;
+  if (aLoadState->IsFormSubmission()) {
+    if (aLoadState->Target().IsEmpty()) {
+      // We set the right load type here for form submissions with an empty
+      // target. Form submission with a non-empty target are handled in
+      // nsDocShell::PerformRetargeting after we've selected the correct target
+      // BC.
+      loadType = GetLoadTypeForFormSubmission(GetBrowsingContext(), aLoadState);
+    }
+  } else {
+    // Link click can be triggered inside an onload handler, and we don't want
+    // to add history entry in this case.
+    bool inOnLoadHandler = false;
+    GetIsExecutingOnLoadHandler(&inOnLoadHandler);
+    if (inOnLoadHandler) {
+      loadType = LOAD_NORMAL_REPLACE;
+    }
+  }
+
+  nsCOMPtr<nsIReferrerInfo> referrerInfo =
+      elementCanHaveNoopener ? new ReferrerInfo(*aContent->AsElement())
+                             : new ReferrerInfo(*referrerDoc);
+  RefPtr<WindowContext> context = mBrowsingContext->GetCurrentWindowContext();
+
+  aLoadState->SetTriggeringSandboxFlags(triggeringSandboxFlags);
+  aLoadState->SetTriggeringWindowId(triggeringWindowId);
+  aLoadState->SetTriggeringStorageAccess(triggeringStorageAccess);
+  aLoadState->SetReferrerInfo(referrerInfo);
+  aLoadState->SetInternalLoadFlags(flags);
+  aLoadState->SetTypeHint(NS_ConvertUTF16toUTF8(typeHint));
+  aLoadState->SetLoadType(loadType);
+  aLoadState->SetSourceBrowsingContext(mBrowsingContext);
+  aLoadState->SetHasValidUserGestureActivation(
+      context && context->HasValidTransientUserGestureActivation());
+
+  nsresult rv = InternalLoad(aLoadState);
+
+  if (NS_SUCCEEDED(rv)) {
+    nsPingListener::DispatchPings(this, aContent, aLoadState->URI(),
+                                  referrerInfo);
+  }
+
+  return rv;
+}
+
+nsresult nsDocShell::OnOverLink(nsIContent* aContent, nsIURI* aURI,
+                                const nsAString& aTargetSpec) {
+  if (aContent->IsEditable()) {
+    return NS_OK;
+  }
+
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIWebBrowserChrome> browserChrome = do_GetInterface(mTreeOwner);
+  if (!browserChrome) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIURI> exposableURI = nsIOService::CreateExposableURI(aURI);
+  nsAutoCString spec;
+  rv = exposableURI->GetDisplaySpec(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  NS_ConvertUTF8toUTF16 uStr(spec);
+
+  PredictorPredict(aURI, mCurrentURI, nsINetworkPredictor::PREDICT_LINK,
+                   aContent->NodePrincipal()->OriginAttributesRef(), nullptr);
+
+  rv = browserChrome->SetLinkStatus(uStr);
+  return rv;
+}
+
+nsresult nsDocShell::OnLeaveLink() {
+  nsCOMPtr<nsIWebBrowserChrome> browserChrome(do_GetInterface(mTreeOwner));
+  nsresult rv = NS_ERROR_FAILURE;
+
+  if (browserChrome) {
+    rv = browserChrome->SetLinkStatus(u""_ns);
+  }
+  return rv;
+}
+
+bool nsDocShell::ShouldBlockLoadingForBackButton() {
+  if (!(mLoadType & LOAD_CMD_HISTORY) ||
+      UserActivation::IsHandlingUserInput() ||
+      !Preferences::GetBool("accessibility.blockjsredirection")) {
+    return false;
+  }
+
+  bool canGoForward = false;
+  GetCanGoForward(&canGoForward);
+  return canGoForward;
+}
+
+//----------------------------------------------------------------------
+// Web Shell Services API
+
+// This functions is only called when a new charset is detected in loading a
+// document.
+nsresult nsDocShell::CharsetChangeReloadDocument(
+    mozilla::NotNull<const mozilla::Encoding*> aEncoding, int32_t aSource) {
+  // XXX hack. keep the aCharset and aSource wait to pick it up
+  nsCOMPtr<nsIDocumentViewer> viewer;
+  NS_ENSURE_SUCCESS(GetDocViewer(getter_AddRefs(viewer)), NS_ERROR_FAILURE);
+  if (viewer) {
+    int32_t source;
+    Unused << viewer->GetReloadEncodingAndSource(&source);
+    if (aSource > source) {
+      viewer->SetReloadEncodingAndSource(aEncoding, aSource);
+      if (eCharsetReloadRequested != mCharsetReloadState) {
+        mCharsetReloadState = eCharsetReloadRequested;
+        switch (mLoadType) {
+          case LOAD_RELOAD_BYPASS_PROXY_AND_CACHE:
+            return Reload(LOAD_FLAGS_CHARSET_CHANGE | LOAD_FLAGS_BYPASS_CACHE |
+                          LOAD_FLAGS_BYPASS_PROXY);
+          case LOAD_RELOAD_BYPASS_CACHE:
+            return Reload(LOAD_FLAGS_CHARSET_CHANGE | LOAD_FLAGS_BYPASS_CACHE);
+          default:
+            return Reload(LOAD_FLAGS_CHARSET_CHANGE);
+        }
+      }
+    }
+  }
+  // return failure if this request is not accepted due to mCharsetReloadState
+  return NS_ERROR_DOCSHELL_REQUEST_REJECTED;
+}
+
+nsresult nsDocShell::CharsetChangeStopDocumentLoad() {
+  if (eCharsetReloadRequested != mCharsetReloadState) {
+    Stop(nsIWebNavigation::STOP_ALL);
+    return NS_OK;
+  }
+  // return failer if this request is not accepted due to mCharsetReloadState
+  return NS_ERROR_DOCSHELL_REQUEST_REJECTED;
+}
+
+NS_IMETHODIMP nsDocShell::ExitPrintPreview() {
+#if NS_PRINT_PREVIEW
+  nsCOMPtr<nsIWebBrowserPrint> viewer = do_QueryInterface(mDocumentViewer);
+  return viewer->ExitPrintPreview();
+#else
+  return NS_OK;
+#endif
+}
+
+/* [infallible] */
+NS_IMETHODIMP nsDocShell::GetIsTopLevelContentDocShell(
+    bool* aIsTopLevelContentDocShell) {
+  *aIsTopLevelContentDocShell = false;
+
+  if (mItemType == typeContent) {
+    *aIsTopLevelContentDocShell = mBrowsingContext->IsTopContent();
+  }
+
+  return NS_OK;
+}
+
+// Implements nsILoadContext.originAttributes
+NS_IMETHODIMP
+nsDocShell::GetScriptableOriginAttributes(JSContext* aCx,
+                                          JS::MutableHandle<JS::Value> aVal) {
+  return mBrowsingContext->GetScriptableOriginAttributes(aCx, aVal);
+}
+
+// Implements nsIDocShell.GetOriginAttributes()
+NS_IMETHODIMP
+nsDocShell::GetOriginAttributes(JSContext* aCx,
+                                JS::MutableHandle<JS::Value> aVal) {
+  return mBrowsingContext->GetScriptableOriginAttributes(aCx, aVal);
+}
+
+bool nsDocShell::ServiceWorkerAllowedToControlWindow(nsIPrincipal* aPrincipal,
+                                                     nsIURI* aURI) {
+  MOZ_ASSERT(aPrincipal);
+  MOZ_ASSERT(aURI);
+
+  if (UsePrivateBrowsing() || mBrowsingContext->GetSandboxFlags()) {
+    return false;
+  }
+
+  nsCOMPtr<nsIDocShellTreeItem> parent;
+  GetInProcessSameTypeParent(getter_AddRefs(parent));
+  nsPIDOMWindowOuter* parentOuter = parent ? parent->GetWindow() : nullptr;
+  nsPIDOMWindowInner* parentInner =
+      parentOuter ? parentOuter->GetCurrentInnerWindow() : nullptr;
+
+  StorageAccess storage =
+      StorageAllowedForNewWindow(aPrincipal, aURI, parentInner);
+
+  // If the partitioned service worker is enabled, service worker is allowed to
+  // control the window if partition is enabled.
+  if (StaticPrefs::privacy_partition_serviceWorkers() && parentInner) {
+    RefPtr<Document> doc = parentInner->GetExtantDoc();
+
+    if (doc && StoragePartitioningEnabled(storage, doc->CookieJarSettings())) {
+      return true;
+    }
+  }
+
+  return storage == StorageAccess::eAllow;
+}
+
+nsresult nsDocShell::SetOriginAttributes(const OriginAttributes& aAttrs) {
+  MOZ_ASSERT(!mIsBeingDestroyed);
+  return mBrowsingContext->SetOriginAttributes(aAttrs);
+}
+
+NS_IMETHODIMP
+nsDocShell::ResumeRedirectedLoad(uint64_t aIdentifier, int32_t aHistoryIndex) {
+  RefPtr<nsDocShell> self = this;
+  RefPtr<ChildProcessChannelListener> cpcl =
+      ChildProcessChannelListener::GetSingleton();
+
+  // Call into InternalLoad with the pending channel when it is received.
+  cpcl->RegisterCallback(
+      aIdentifier, [self, aHistoryIndex](
+                       nsDocShellLoadState* aLoadState,
+                       nsTArray<Endpoint<extensions::PStreamFilterParent>>&&
+                           aStreamFilterEndpoints,
+                       nsDOMNavigationTiming* aTiming) {
+        MOZ_ASSERT(aLoadState->GetPendingRedirectedChannel());
+        if (NS_WARN_IF(self->mIsBeingDestroyed)) {
+          aLoadState->GetPendingRedirectedChannel()->CancelWithReason(
+              NS_BINDING_ABORTED, "nsDocShell::mIsBeingDestroyed"_ns);
+          return NS_BINDING_ABORTED;
+        }
+
+        self->mLoadType = aLoadState->LoadType();
+        nsCOMPtr<nsIURI> previousURI;
+        uint32_t previousFlags = 0;
+        ExtractLastVisit(aLoadState->GetPendingRedirectedChannel(),
+                         getter_AddRefs(previousURI), &previousFlags);
+        self->SaveLastVisit(aLoadState->GetPendingRedirectedChannel(),
+                            previousURI, previousFlags);
+
+        if (aTiming) {
+          self->mTiming = new nsDOMNavigationTiming(self, aTiming);
+          self->mBlankTiming = false;
+        }
+
+        // If we're performing a history load, locate the correct history entry,
+        // and set the relevant bits on our loadState.
+        if (aHistoryIndex >= 0 && self->GetSessionHistory() &&
+            !mozilla::SessionHistoryInParent()) {
+          nsCOMPtr<nsISHistory> legacySHistory =
+              self->GetSessionHistory()->LegacySHistory();
+
+          nsCOMPtr<nsISHEntry> entry;
+          nsresult rv = legacySHistory->GetEntryAtIndex(aHistoryIndex,
+                                                        getter_AddRefs(entry));
+          if (NS_SUCCEEDED(rv)) {
+            legacySHistory->InternalSetRequestedIndex(aHistoryIndex);
+            aLoadState->SetLoadType(LOAD_HISTORY);
+            aLoadState->SetSHEntry(entry);
+          }
+        }
+
+        self->InternalLoad(aLoadState);
+
+        if (aLoadState->GetOriginalURIString().isSome()) {
+          // Save URI string in case it's needed later when
+          // sending to search engine service in EndPageLoad()
+          self->mOriginalUriString = *aLoadState->GetOriginalURIString();
+        }
+
+        for (auto& endpoint : aStreamFilterEndpoints) {
+          extensions::StreamFilterParent::Attach(
+              aLoadState->GetPendingRedirectedChannel(), std::move(endpoint));
+        }
+
+        // If the channel isn't pending, then it means that InternalLoad
+        // never connected it, and we shouldn't try to continue. This
+        // can happen even if InternalLoad returned NS_OK.
+        bool pending = false;
+        aLoadState->GetPendingRedirectedChannel()->IsPending(&pending);
+        NS_ASSERTION(pending, "We should have connected the pending channel!");
+        if (!pending) {
+          return NS_BINDING_ABORTED;
+        }
+        return NS_OK;
+      });
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetOriginAttributes(JS::Handle<JS::Value> aOriginAttributes,
+                                JSContext* aCx) {
+  OriginAttributes attrs;
+  if (!aOriginAttributes.isObject() || !attrs.Init(aCx, aOriginAttributes)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return SetOriginAttributes(attrs);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetAsyncPanZoomEnabled(bool* aOut) {
+  if (PresShell* presShell = GetPresShell()) {
+    *aOut = presShell->AsyncPanZoomEnabled();
+    return NS_OK;
+  }
+
+  // If we don't have a presShell, fall back to the default platform value of
+  // whether or not APZ is enabled.
+  *aOut = gfxPlatform::AsyncPanZoomEnabled();
+  return NS_OK;
+}
+
+bool nsDocShell::HasUnloadedParent() {
+  for (WindowContext* wc = GetBrowsingContext()->GetParentWindowContext(); wc;
+       wc = wc->GetParentWindowContext()) {
+    if (!wc->IsCurrent() || wc->IsDiscarded() ||
+        wc->GetBrowsingContext()->IsDiscarded()) {
+      // If a parent is OOP and the parent WindowContext is no
+      // longer current, we can assume the parent was unloaded.
+      return true;
+    }
+
+    if (wc->GetBrowsingContext()->IsInProcess() &&
+        (!wc->GetBrowsingContext()->GetDocShell() ||
+         wc->GetBrowsingContext()->GetDocShell()->GetIsInUnload())) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */
+bool nsDocShell::ShouldUpdateGlobalHistory(uint32_t aLoadType) {
+  return !(aLoadType == LOAD_BYPASS_HISTORY || aLoadType == LOAD_ERROR_PAGE ||
+           aLoadType & LOAD_CMD_HISTORY);
+}
+
+void nsDocShell::UpdateGlobalHistoryTitle(nsIURI* aURI) {
+  if (!mBrowsingContext->GetUseGlobalHistory() || UsePrivateBrowsing()) {
+    return;
+  }
+
+  // Global history is interested into sub-frame visits only for link-coloring
+  // purposes, thus title updates are skipped for those.
+  //
+  // Moreover, some iframe documents (such as the ones created via
+  // document.open()) inherit the document uri of the caller, which would cause
+  // us to override a previously set page title with one from the subframe.
+  if (IsSubframe()) {
+    return;
+  }
+
+  if (nsCOMPtr<IHistory> history = components::History::Service()) {
+    history->SetURITitle(aURI, mTitle);
+  }
+}
+
+bool nsDocShell::IsInvisible() { return mInvisible; }
+
+void nsDocShell::SetInvisible(bool aInvisible) { mInvisible = aInvisible; }
+
+/* static */
+void nsDocShell::MaybeNotifyKeywordSearchLoading(const nsString& aProvider,
+                                                 const nsString& aKeyword) {
+  if (aProvider.IsEmpty()) {
+    return;
+  }
+  nsresult rv;
+  nsCOMPtr<nsISupportsString> isupportsString =
+      do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  rv = isupportsString->SetData(aProvider);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  nsCOMPtr<nsIObserverService> obsSvc = services::GetObserverService();
+  if (obsSvc) {
+    // Note that "keyword-search" refers to a search via the url
+    // bar, not a bookmarks keyword search.
+    obsSvc->NotifyObservers(isupportsString, "keyword-search", aKeyword.get());
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::ShouldPrepareForIntercept(nsIURI* aURI, nsIChannel* aChannel,
+                                      bool* aShouldIntercept) {
+  return mInterceptController->ShouldPrepareForIntercept(aURI, aChannel,
+                                                         aShouldIntercept);
+}
+
+NS_IMETHODIMP
+nsDocShell::ChannelIntercepted(nsIInterceptedChannel* aChannel) {
+  return mInterceptController->ChannelIntercepted(aChannel);
+}
+
+bool nsDocShell::InFrameSwap() {
+  RefPtr<nsDocShell> shell = this;
+  do {
+    if (shell->mInFrameSwap) {
+      return true;
+    }
+    shell = shell->GetInProcessParentDocshell();
+  } while (shell);
+  return false;
+}
+
+UniquePtr<ClientSource> nsDocShell::TakeInitialClientSource() {
+  return std::move(mInitialClientSource);
+}
+
+NS_IMETHODIMP
+nsDocShell::GetEditingSession(nsIEditingSession** aEditSession) {
+  if (!NS_SUCCEEDED(EnsureEditorData())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  *aEditSession = do_AddRef(mEditorData->GetEditingSession()).take();
+  return *aEditSession ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetScriptableBrowserChild(nsIBrowserChild** aBrowserChild) {
+  *aBrowserChild = GetBrowserChild().take();
+  return *aBrowserChild ? NS_OK : NS_ERROR_FAILURE;
+}
+
+already_AddRefed<nsIBrowserChild> nsDocShell::GetBrowserChild() {
+  nsCOMPtr<nsIBrowserChild> tc = do_QueryReferent(mBrowserChild);
+  return tc.forget();
+}
+
+nsCommandManager* nsDocShell::GetCommandManager() {
+  NS_ENSURE_SUCCESS(EnsureCommandHandler(), nullptr);
+  return mCommandManager;
+}
+
+NS_IMETHODIMP_(void)
+nsDocShell::GetOriginAttributes(mozilla::OriginAttributes& aAttrs) {
+  mBrowsingContext->GetOriginAttributes(aAttrs);
+}
+
+HTMLEditor* nsIDocShell::GetHTMLEditor() {
+  nsDocShell* docShell = static_cast<nsDocShell*>(this);
+  return docShell->GetHTMLEditorInternal();
+}
+
+nsresult nsIDocShell::SetHTMLEditor(HTMLEditor* aHTMLEditor) {
+  nsDocShell* docShell = static_cast<nsDocShell*>(this);
+  return docShell->SetHTMLEditorInternal(aHTMLEditor);
+}
+
+#define MATRIX_LENGTH 20
+
+NS_IMETHODIMP
+nsDocShell::SetColorMatrix(const nsTArray<float>& aMatrix) {
+  if (aMatrix.Length() == MATRIX_LENGTH) {
+    mColorMatrix.reset(new gfx::Matrix5x4());
+    static_assert(
+        MATRIX_LENGTH * sizeof(float) == sizeof(mColorMatrix->components),
+        "Size mismatch for our memcpy");
+    memcpy(mColorMatrix->components, aMatrix.Elements(),
+           sizeof(mColorMatrix->components));
+  } else if (aMatrix.Length() == 0) {
+    mColorMatrix.reset();
+  } else {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  PresShell* presShell = GetPresShell();
+  if (!presShell) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsIFrame* frame = presShell->GetRootFrame();
+  if (!frame) {
+    return NS_ERROR_FAILURE;
+  }
+
+  frame->SchedulePaint();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetColorMatrix(nsTArray<float>& aMatrix) {
+  if (mColorMatrix) {
+    aMatrix.SetLength(MATRIX_LENGTH);
+    static_assert(
+        MATRIX_LENGTH * sizeof(float) == sizeof(mColorMatrix->components),
+        "Size mismatch for our memcpy");
+    memcpy(aMatrix.Elements(), mColorMatrix->components,
+           MATRIX_LENGTH * sizeof(float));
+  }
+
+  return NS_OK;
+}
+
+#undef MATRIX_LENGTH
+
+NS_IMETHODIMP
+nsDocShell::GetIsForceReloading(bool* aForceReload) {
+  *aForceReload = IsForceReloading();
+  return NS_OK;
+}
+
+bool nsDocShell::IsForceReloading() { return IsForceReloadType(mLoadType); }
+
+NS_IMETHODIMP
+nsDocShell::GetBrowsingContextXPCOM(BrowsingContext** aBrowsingContext) {
+  *aBrowsingContext = do_AddRef(mBrowsingContext).take();
+  return NS_OK;
+}
+
+BrowsingContext* nsDocShell::GetBrowsingContext() { return mBrowsingContext; }
+
+bool nsDocShell::GetIsAttemptingToNavigate() {
+  // XXXbz the document.open spec says to abort even if there's just a
+  // queued navigation task, sort of.  It's not clear whether browsers
+  // actually do that, and we didn't use to do it, so for now let's
+  // not do that.
+  // https://github.com/whatwg/html/issues/3447 tracks the spec side of this.
+  if (mDocumentRequest) {
+    // There's definitely a navigation in progress.
+    return true;
+  }
+
+  // javascript: channels have slightly weird behavior: they're LOAD_BACKGROUND
+  // until the script runs, which means they're not sending loadgroup
+  // notifications and hence not getting set as mDocumentRequest.  Look through
+  // our loadgroup for document-level javascript: loads.
+  if (!mLoadGroup) {
+    return false;
+  }
+
+  nsCOMPtr<nsISimpleEnumerator> requests;
+  mLoadGroup->GetRequests(getter_AddRefs(requests));
+  bool hasMore = false;
+  while (NS_SUCCEEDED(requests->HasMoreElements(&hasMore)) && hasMore) {
+    nsCOMPtr<nsISupports> elem;
+    requests->GetNext(getter_AddRefs(elem));
+    nsCOMPtr<nsIScriptChannel> scriptChannel(do_QueryInterface(elem));
+    if (!scriptChannel) {
+      continue;
+    }
+
+    if (scriptChannel->GetIsDocumentLoad()) {
+      // This is a javascript: load that might lead to a new document,
+      // hence a navigation.
+      return true;
+    }
+  }
+
+  return mCheckingSessionHistory;
+}
+
+void nsDocShell::SetLoadingSessionHistoryInfo(
+    const mozilla::dom::LoadingSessionHistoryInfo& aLoadingInfo,
+    bool aNeedToReportActiveAfterLoadingBecomesActive) {
+  // FIXME Would like to assert this, but can't yet.
+  // MOZ_ASSERT(!mLoadingEntry);
+  MOZ_LOG(gSHLog, LogLevel::Debug,
+          ("Setting the loading entry on nsDocShell %p to %s", this,
+           aLoadingInfo.mInfo.GetURI()->GetSpecOrDefault().get()));
+  mLoadingEntry = MakeUnique<LoadingSessionHistoryInfo>(aLoadingInfo);
+  mNeedToReportActiveAfterLoadingBecomesActive =
+      aNeedToReportActiveAfterLoadingBecomesActive;
+}
+
+void nsDocShell::MoveLoadingToActiveEntry(bool aPersist, bool aExpired,
+                                          uint32_t aCacheKey,
+                                          nsIURI* aPreviousURI) {
+  MOZ_ASSERT(mozilla::SessionHistoryInParent());
+
+  MOZ_LOG(gSHLog, LogLevel::Debug,
+          ("nsDocShell %p MoveLoadingToActiveEntry", this));
+
+  UniquePtr<SessionHistoryInfo> previousActiveEntry(mActiveEntry.release());
+  mozilla::UniquePtr<mozilla::dom::LoadingSessionHistoryInfo> loadingEntry;
+  mActiveEntryIsLoadingFromSessionHistory =
+      mLoadingEntry && mLoadingEntry->mLoadIsFromSessionHistory;
+  if (mLoadingEntry) {
+    MOZ_LOG(gSHLog, LogLevel::Debug,
+            ("Moving the loading entry to the active entry on nsDocShell %p "
+             "to %s",
+             this, mLoadingEntry->mInfo.GetURI()->GetSpecOrDefault().get()));
+    mActiveEntry = MakeUnique<SessionHistoryInfo>(mLoadingEntry->mInfo);
+    mLoadingEntry.swap(loadingEntry);
+    if (!mActiveEntryIsLoadingFromSessionHistory) {
+      if (mNeedToReportActiveAfterLoadingBecomesActive) {
+        // Needed to pass various history length WPTs.
+        mBrowsingContext->SetActiveSessionHistoryEntry(
+            mozilla::Nothing(), mActiveEntry.get(), mLoadType,
+            /* aUpdatedCacheKey = */ 0, false);
+      }
+      mBrowsingContext->IncrementHistoryEntryCountForBrowsingContext();
+    }
+  }
+  mNeedToReportActiveAfterLoadingBecomesActive = false;
+
+  if (mActiveEntry) {
+    if (aCacheKey != 0) {
+      mActiveEntry->SetCacheKey(aCacheKey);
+    }
+    MOZ_ASSERT(loadingEntry);
+    uint32_t loadType =
+        mLoadType == LOAD_ERROR_PAGE ? mFailedLoadType : mLoadType;
+
+    if (loadingEntry->mLoadId != UINT64_MAX) {
+      // We're passing in mCurrentURI, which could be null. SessionHistoryCommit
+      // does require a non-null uri if this is for a refresh load of the same
+      // URI, but in that case mCurrentURI won't be null here.
+      mBrowsingContext->SessionHistoryCommit(
+          *loadingEntry, loadType, aPreviousURI, previousActiveEntry.get(),
+          aPersist, false, aExpired, aCacheKey);
+    }
+  }
+}
+
+static bool IsFaviconLoad(nsIRequest* aRequest) {
+  nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);
+  if (!channel) {
+    return false;
+  }
+
+  nsCOMPtr<nsILoadInfo> li = channel->LoadInfo();
+  return li && li->InternalContentPolicyType() ==
+                   nsIContentPolicy::TYPE_INTERNAL_IMAGE_FAVICON;
+}
+
+void nsDocShell::RecordSingleChannelId(bool aStartRequest,
+                                       nsIRequest* aRequest) {
+  // Ignore favicon loads, they don't need to block caching.
+  if (IsFaviconLoad(aRequest)) {
+    return;
+  }
+
+  MOZ_ASSERT_IF(!aStartRequest, mRequestForBlockingFromBFCacheCount > 0);
+
+  mRequestForBlockingFromBFCacheCount += aStartRequest ? 1 : -1;
+
+  if (mBrowsingContext->GetCurrentWindowContext()) {
+    // We have three states: no request, one request with an id and
+    // eiher one request without an id or multiple requests. Nothing() is no
+    // request, Some(non-zero) is one request with an id and Some(0) is one
+    // request without an id or multiple requests.
+    Maybe<uint64_t> singleChannelId;
+    if (mRequestForBlockingFromBFCacheCount > 1) {
+      singleChannelId = Some(0);
+    } else if (mRequestForBlockingFromBFCacheCount == 1) {
+      nsCOMPtr<nsIIdentChannel> identChannel;
+      if (aStartRequest) {
+        identChannel = do_QueryInterface(aRequest);
+      } else {
+        // aChannel is the channel that's being removed, but we need to check if
+        // the remaining channel in the loadgroup has an id.
+        nsCOMPtr<nsISimpleEnumerator> requests;
+        mLoadGroup->GetRequests(getter_AddRefs(requests));
+        for (const auto& request : SimpleEnumerator<nsIRequest>(requests)) {
+          if (!IsFaviconLoad(request) &&
+              !!(identChannel = do_QueryInterface(request))) {
+            break;
+          }
+        }
+      }
+
+      if (identChannel) {
+        singleChannelId = Some(identChannel->ChannelId());
+      } else {
+        singleChannelId = Some(0);
+      }
+    } else {
+      MOZ_ASSERT(mRequestForBlockingFromBFCacheCount == 0);
+      singleChannelId = Nothing();
+    }
+
+    if (MOZ_UNLIKELY(MOZ_LOG_TEST(gSHIPBFCacheLog, LogLevel::Verbose))) {
+      nsAutoCString uri("[no uri]");
+      if (mCurrentURI) {
+        uri = mCurrentURI->GetSpecOrDefault();
+      }
+      if (singleChannelId.isNothing()) {
+        MOZ_LOG(gSHIPBFCacheLog, LogLevel::Verbose,
+                ("Loadgroup for %s doesn't have any requests relevant for "
+                 "blocking BFCache",
+                 uri.get()));
+      } else if (singleChannelId.value() == 0) {
+        MOZ_LOG(gSHIPBFCacheLog, LogLevel::Verbose,
+                ("Loadgroup for %s has multiple requests relevant for blocking "
+                 "BFCache",
+                 uri.get()));
+      } else {
+        MOZ_LOG(gSHIPBFCacheLog, LogLevel::Verbose,
+                ("Loadgroup for %s has one request with id %" PRIu64
+                 " relevant for blocking BFCache",
+                 uri.get(), singleChannelId.value()));
+      }
+    }
+
+    if (mSingleChannelId != singleChannelId) {
+      mSingleChannelId = singleChannelId;
+      WindowGlobalChild* wgc =
+          mBrowsingContext->GetCurrentWindowContext()->GetWindowGlobalChild();
+      if (wgc) {
+        wgc->SendSetSingleChannelId(singleChannelId);
+      }
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsDocShell::OnStartRequest(nsIRequest* aRequest) {
+  if (MOZ_UNLIKELY(MOZ_LOG_TEST(gSHIPBFCacheLog, LogLevel::Verbose))) {
+    nsAutoCString uri("[no uri]");
+    if (mCurrentURI) {
+      uri = mCurrentURI->GetSpecOrDefault();
+    }
+    nsAutoCString name;
+    aRequest->GetName(name);
+    MOZ_LOG(gSHIPBFCacheLog, LogLevel::Verbose,
+            ("Adding request %s to loadgroup for %s", name.get(), uri.get()));
+  }
+  RecordSingleChannelId(true, aRequest);
+  return nsDocLoader::OnStartRequest(aRequest);
+}
+
+NS_IMETHODIMP
+nsDocShell::OnStopRequest(nsIRequest* aRequest, nsresult aStatusCode) {
+  if (MOZ_UNLIKELY(MOZ_LOG_TEST(gSHIPBFCacheLog, LogLevel::Verbose))) {
+    nsAutoCString uri("[no uri]");
+    if (mCurrentURI) {
+      uri = mCurrentURI->GetSpecOrDefault();
+    }
+    nsAutoCString name;
+    aRequest->GetName(name);
+    MOZ_LOG(
+        gSHIPBFCacheLog, LogLevel::Verbose,
+        ("Removing request %s from loadgroup for %s", name.get(), uri.get()));
+  }
+  RecordSingleChannelId(false, aRequest);
+  return nsDocLoader::OnStopRequest(aRequest, aStatusCode);
+}
+
+void nsDocShell::MaybeDisconnectChildListenersOnPageHide() {
+  MOZ_RELEASE_ASSERT(XRE_IsContentProcess());
+
+  if (mChannelToDisconnectOnPageHide != 0 && mLoadGroup) {
+    nsCOMPtr<nsISimpleEnumerator> requests;
+    mLoadGroup->GetRequests(getter_AddRefs(requests));
+    for (const auto& request : SimpleEnumerator<nsIRequest>(requests)) {
+      RefPtr<DocumentChannel> channel = do_QueryObject(request);
+      if (channel && channel->ChannelId() == mChannelToDisconnectOnPageHide) {
+        static_cast<DocumentChannelChild*>(channel.get())
+            ->DisconnectChildListeners(NS_BINDING_ABORTED, NS_BINDING_ABORTED);
+      }
+    }
+    mChannelToDisconnectOnPageHide = 0;
+  }
+}
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
new file mode 100644
index 0000000000..9f2d9a17dc
--- /dev/null
+++ b/docshell/base/nsDocShell.h
@@ -0,0 +1,1366 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDocShell_h__
+#define nsDocShell_h__
+
+#include "Units.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/NotNull.h"
+#include "mozilla/ScrollbarPreferences.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WeakPtr.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "nsCOMPtr.h"
+#include "nsCharsetSource.h"
+#include "nsDocLoader.h"
+#include "nsIAuthPromptProvider.h"
+#include "nsIBaseWindow.h"
+#include "nsIDocShell.h"
+#include "nsIDocShellTreeItem.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsILoadContext.h"
+#include "nsINetworkInterceptController.h"
+#include "nsIRefreshURI.h"
+#include "nsIWebNavigation.h"
+#include "nsIWebPageDescriptor.h"
+#include "nsIWebProgressListener.h"
+#include "nsPoint.h"  // mCurrent/mDefaultScrollbarPreferences
+#include "nsRect.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "prtime.h"
+
+// Interfaces Needed
+
+namespace mozilla {
+class Encoding;
+class HTMLEditor;
+class ObservedDocShell;
+enum class TaskCategory;
+namespace dom {
+class ClientInfo;
+class ClientSource;
+class EventTarget;
+class SessionHistoryInfo;
+struct LoadingSessionHistoryInfo;
+struct Wireframe;
+}  // namespace dom
+namespace net {
+class LoadInfo;
+class DocumentLoadListener;
+}  // namespace net
+}  // namespace mozilla
+
+class nsIController;
+class nsIDocShellTreeOwner;
+class nsIDocumentViewer;
+class nsIHttpChannel;
+class nsIMutableArray;
+class nsIPrompt;
+class nsIScrollableFrame;
+class nsIStringBundle;
+class nsIURIFixup;
+class nsIURIFixupInfo;
+class nsIURILoader;
+class nsIWebBrowserFind;
+class nsIWidget;
+class nsIReferrerInfo;
+
+class nsCommandManager;
+class nsDocShellEditorData;
+class nsDOMNavigationTiming;
+class nsDSURIContentListener;
+class nsGlobalWindowOuter;
+
+class FramingChecker;
+class OnLinkClickEvent;
+
+/* internally used ViewMode types */
+enum ViewMode { viewNormal = 0x0, viewSource = 0x1 };
+
+enum eCharsetReloadState {
+  eCharsetReloadInit,
+  eCharsetReloadRequested,
+  eCharsetReloadStopOrigional
+};
+
+class nsDocShell final : public nsDocLoader,
+                         public nsIDocShell,
+                         public nsIWebNavigation,
+                         public nsIBaseWindow,
+                         public nsIRefreshURI,
+                         public nsIWebProgressListener,
+                         public nsIWebPageDescriptor,
+                         public nsIAuthPromptProvider,
+                         public nsILoadContext,
+                         public nsINetworkInterceptController,
+                         public mozilla::SupportsWeakPtr {
+ public:
+  enum InternalLoad : uint32_t {
+    INTERNAL_LOAD_FLAGS_NONE = 0x0,
+    INTERNAL_LOAD_FLAGS_INHERIT_PRINCIPAL = 0x1,
+    INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER = 0x2,
+    INTERNAL_LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP = 0x4,
+
+    // This flag marks the first load in this object
+    // @see nsIWebNavigation::LOAD_FLAGS_FIRST_LOAD
+    INTERNAL_LOAD_FLAGS_FIRST_LOAD = 0x8,
+
+    // The set of flags that should not be set before calling into
+    // nsDocShell::LoadURI and other nsDocShell loading functions.
+    INTERNAL_LOAD_FLAGS_LOADURI_SETUP_FLAGS = 0xf,
+
+    INTERNAL_LOAD_FLAGS_BYPASS_CLASSIFIER = 0x10,
+    INTERNAL_LOAD_FLAGS_FORCE_ALLOW_COOKIES = 0x20,
+
+    // Whether the load should be treated as srcdoc load, rather than a URI one.
+    INTERNAL_LOAD_FLAGS_IS_SRCDOC = 0x40,
+
+    // Whether this is the load of a frame's original src attribute
+    INTERNAL_LOAD_FLAGS_ORIGINAL_FRAME_SRC = 0x80,
+
+    INTERNAL_LOAD_FLAGS_NO_OPENER = 0x100,
+
+    // Whether a top-level data URI navigation is allowed for that load
+    INTERNAL_LOAD_FLAGS_FORCE_ALLOW_DATA_URI = 0x200,
+
+    // Whether the load should go through LoadURIDelegate.
+    INTERNAL_LOAD_FLAGS_BYPASS_LOAD_URI_DELEGATE = 0x2000,
+  };
+
+  // Event type dispatched by RestorePresentation
+  class RestorePresentationEvent : public mozilla::Runnable {
+   public:
+    NS_DECL_NSIRUNNABLE
+    explicit RestorePresentationEvent(nsDocShell* aDs)
+        : mozilla::Runnable("nsDocShell::RestorePresentationEvent"),
+          mDocShell(aDs) {}
+    void Revoke() { mDocShell = nullptr; }
+
+   private:
+    RefPtr<nsDocShell> mDocShell;
+  };
+
+  class InterfaceRequestorProxy : public nsIInterfaceRequestor {
+   public:
+    explicit InterfaceRequestorProxy(nsIInterfaceRequestor* aRequestor);
+    NS_DECL_THREADSAFE_ISUPPORTS
+    NS_DECL_NSIINTERFACEREQUESTOR
+
+   private:
+    virtual ~InterfaceRequestorProxy();
+    InterfaceRequestorProxy() = default;
+    nsWeakPtr mWeakPtr;
+  };
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(nsDocShell, nsDocLoader)
+  NS_DECL_NSIDOCSHELL
+  NS_DECL_NSIDOCSHELLTREEITEM
+  NS_DECL_NSIWEBNAVIGATION
+  NS_DECL_NSIBASEWINDOW
+  NS_DECL_NSIINTERFACEREQUESTOR
+  NS_DECL_NSIWEBPROGRESSLISTENER
+  NS_DECL_NSIREFRESHURI
+  NS_DECL_NSIWEBPAGEDESCRIPTOR
+  NS_DECL_NSIAUTHPROMPTPROVIDER
+  NS_DECL_NSINETWORKINTERCEPTCONTROLLER
+
+  // Create a new nsDocShell object.
+  static already_AddRefed<nsDocShell> Create(
+      mozilla::dom::BrowsingContext* aBrowsingContext,
+      uint64_t aContentWindowID = 0);
+
+  bool Initialize();
+
+  NS_IMETHOD Stop() override {
+    // Need this here because otherwise nsIWebNavigation::Stop
+    // overrides the docloader's Stop()
+    return nsDocLoader::Stop();
+  }
+
+  mozilla::ScrollbarPreference ScrollbarPreference() const {
+    return mScrollbarPref;
+  }
+  void SetScrollbarPreference(mozilla::ScrollbarPreference);
+
+  /*
+   * The size, in CSS pixels, of the margins for the <body> of an HTML document
+   * in this docshell; used to implement the marginwidth attribute on HTML
+   * <frame>/<iframe> elements.  A value smaller than zero indicates that the
+   * attribute was not set.
+   */
+  const mozilla::CSSIntSize& GetFrameMargins() const { return mFrameMargins; }
+
+  bool UpdateFrameMargins(const mozilla::CSSIntSize& aMargins) {
+    if (mFrameMargins == aMargins) {
+      return false;
+    }
+    mFrameMargins = aMargins;
+    return true;
+  }
+
+  /**
+   * Process a click on a link.
+   *
+   * @param aContent the content object used for triggering the link.
+   * @param aURI a URI object that defines the destination for the link
+   * @param aTargetSpec indicates where the link is targeted (may be an empty
+   *        string)
+   * @param aFileName non-null when the link should be downloaded as the given
+   * file
+   * @param aPostDataStream the POST data to send
+   * @param aHeadersDataStream ??? (only used for plugins)
+   * @param aIsTrusted false if the triggerer is an untrusted DOM event.
+   * @param aTriggeringPrincipal, if not passed explicitly we fall back to
+   *        the document's principal.
+   * @param aCsp, the CSP to be used for the load, that is the CSP of the
+   *        entity responsible for causing the load to occur. Most likely
+   *        this is the CSP of the document that started the load. In case
+   *        aCsp was not passed explicitly we fall back to using
+   *        aContent's document's CSP if that document holds any.
+   */
+  nsresult OnLinkClick(nsIContent* aContent, nsIURI* aURI,
+                       const nsAString& aTargetSpec, const nsAString& aFileName,
+                       nsIInputStream* aPostDataStream,
+                       nsIInputStream* aHeadersDataStream,
+                       bool aIsUserTriggered, bool aIsTrusted,
+                       nsIPrincipal* aTriggeringPrincipal,
+                       nsIContentSecurityPolicy* aCsp);
+  /**
+   * Process a click on a link.
+   *
+   * Works the same as OnLinkClick() except it happens immediately rather than
+   * through an event.
+   *
+   * @param aContent the content object used for triggering the link.
+   * @param aDocShellLoadState the extended load info for this load.
+   * @param aNoOpenerImplied if the link implies "noopener"
+   * @param aTriggeringPrincipal, if not passed explicitly we fall back to
+   *        the document's principal.
+   */
+  nsresult OnLinkClickSync(nsIContent* aContent,
+                           nsDocShellLoadState* aLoadState,
+                           bool aNoOpenerImplied,
+                           nsIPrincipal* aTriggeringPrincipal);
+
+  /**
+   * Process a mouse-over a link.
+   *
+   * @param aContent the linked content.
+   * @param aURI an URI object that defines the destination for the link
+   * @param aTargetSpec indicates where the link is targeted (it may be an empty
+   *        string)
+   */
+  nsresult OnOverLink(nsIContent* aContent, nsIURI* aURI,
+                      const nsAString& aTargetSpec);
+  /**
+   * Process the mouse leaving a link.
+   */
+  nsresult OnLeaveLink();
+
+  // Don't use NS_DECL_NSILOADCONTEXT because some of nsILoadContext's methods
+  // are shared with nsIDocShell and can't be declared twice.
+  NS_IMETHOD GetAssociatedWindow(mozIDOMWindowProxy**) override;
+  NS_IMETHOD GetTopWindow(mozIDOMWindowProxy**) override;
+  NS_IMETHOD GetTopFrameElement(mozilla::dom::Element**) override;
+  NS_IMETHOD GetIsContent(bool*) override;
+  NS_IMETHOD GetUsePrivateBrowsing(bool*) override;
+  NS_IMETHOD SetUsePrivateBrowsing(bool) override;
+  NS_IMETHOD SetPrivateBrowsing(bool) override;
+  NS_IMETHOD GetUseRemoteTabs(bool*) override;
+  NS_IMETHOD SetRemoteTabs(bool) override;
+  NS_IMETHOD GetUseRemoteSubframes(bool*) override;
+  NS_IMETHOD SetRemoteSubframes(bool) override;
+  NS_IMETHOD GetScriptableOriginAttributes(
+      JSContext*, JS::MutableHandle<JS::Value>) override;
+  NS_IMETHOD_(void)
+  GetOriginAttributes(mozilla::OriginAttributes& aAttrs) override;
+
+  // Restores a cached presentation from history (mLSHE).
+  // This method swaps out the content viewer and simulates loads for
+  // subframes. It then simulates the completion of the toplevel load.
+  nsresult RestoreFromHistory();
+
+  /**
+   * Parses the passed in header string and sets up a refreshURI if a "refresh"
+   * header is found. If docshell is busy loading a page currently, the request
+   * will be queued and executed when the current page finishes loading.
+   *
+   * @param aDocument    document to which the refresh header applies.
+   * @param aHeader      The meta refresh header string.
+   */
+  void SetupRefreshURIFromHeader(mozilla::dom::Document* aDocument,
+                                 const nsAString& aHeader);
+
+  // Perform a URI load from a refresh timer. This is just like the
+  // ForceRefreshURI method on nsIRefreshURI, but makes sure to take
+  // the timer involved out of mRefreshURIList if it's there.
+  // aTimer must not be null.
+  nsresult ForceRefreshURIFromTimer(nsIURI* aURI, nsIPrincipal* aPrincipal,
+                                    uint32_t aDelay, nsITimer* aTimer);
+
+  // We need dummy OnLocationChange in some cases to update the UI without
+  // updating security info.
+  void FireDummyOnLocationChange() {
+    FireOnLocationChange(this, nullptr, mCurrentURI,
+                         LOCATION_CHANGE_SAME_DOCUMENT);
+  }
+
+  nsresult HistoryEntryRemoved(int32_t aIndex);
+
+  // Notify Scroll observers when an async panning/zooming transform
+  // has started being applied
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  void NotifyAsyncPanZoomStarted();
+
+  // Notify Scroll observers when an async panning/zooming transform
+  // is no longer applied
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  void NotifyAsyncPanZoomStopped();
+
+  void SetInFrameSwap(bool aInSwap) { mInFrameSwap = aInSwap; }
+  bool InFrameSwap();
+
+  bool GetForcedAutodetection() { return mForcedAutodetection; }
+
+  void ResetForcedAutodetection() { mForcedAutodetection = false; }
+
+  mozilla::HTMLEditor* GetHTMLEditorInternal();
+  nsresult SetHTMLEditorInternal(mozilla::HTMLEditor* aHTMLEditor);
+
+  // Handle page navigation due to charset changes
+  nsresult CharsetChangeReloadDocument(
+      mozilla::NotNull<const mozilla::Encoding*> aEncoding, int32_t aSource);
+  nsresult CharsetChangeStopDocumentLoad();
+
+  nsDOMNavigationTiming* GetNavigationTiming() const;
+
+  nsresult SetOriginAttributes(const mozilla::OriginAttributes& aAttrs);
+
+  const mozilla::OriginAttributes& GetOriginAttributes() {
+    return mBrowsingContext->OriginAttributesRef();
+  }
+
+  // Determine whether this docshell corresponds to the given history entry,
+  // via having a pointer to it in mOSHE or mLSHE.
+  bool HasHistoryEntry(nsISHEntry* aEntry) const {
+    return aEntry && (aEntry == mOSHE || aEntry == mLSHE);
+  }
+
+  // Update any pointers (mOSHE or mLSHE) to aOldEntry to point to aNewEntry
+  void SwapHistoryEntries(nsISHEntry* aOldEntry, nsISHEntry* aNewEntry);
+
+  bool GetCreatedDynamically() const {
+    return mBrowsingContext && mBrowsingContext->CreatedDynamically();
+  }
+
+  mozilla::gfx::Matrix5x4* GetColorMatrix() { return mColorMatrix.get(); }
+
+  static bool SandboxFlagsImplyCookies(const uint32_t& aSandboxFlags);
+
+  // Tell the favicon service that aNewURI has the same favicon as aOldURI.
+  static void CopyFavicon(nsIURI* aOldURI, nsIURI* aNewURI,
+                          bool aInPrivateBrowsing);
+
+  static nsDocShell* Cast(nsIDocShell* aDocShell) {
+    return static_cast<nsDocShell*>(aDocShell);
+  }
+
+  static bool CanLoadInParentProcess(nsIURI* aURI);
+
+  // Returns true if the current load is a force reload (started by holding
+  // shift while triggering reload)
+  bool IsForceReloading();
+
+  mozilla::dom::WindowProxyHolder GetWindowProxy() {
+    EnsureScriptEnvironment();
+    return mozilla::dom::WindowProxyHolder(mBrowsingContext);
+  }
+
+  /**
+   * Loads the given URI. See comments on nsDocShellLoadState members for more
+   * information on information used.
+   * `aCacheKey` gets passed to DoURILoad call.
+   */
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  nsresult InternalLoad(
+      nsDocShellLoadState* aLoadState,
+      mozilla::Maybe<uint32_t> aCacheKey = mozilla::Nothing());
+
+  void MaybeRestoreWindowName();
+
+  void StoreWindowNameToSHEntries();
+
+  void SetWillChangeProcess() { mWillChangeProcess = true; }
+  bool WillChangeProcess() { return mWillChangeProcess; }
+
+  // Create a content viewer within this nsDocShell for the given
+  // `WindowGlobalChild` actor.
+  nsresult CreateDocumentViewerForActor(
+      mozilla::dom::WindowGlobalChild* aWindowActor);
+
+  // Creates a real network channel (not a DocumentChannel) using the specified
+  // parameters.
+  // Used by nsDocShell when not using DocumentChannel, by DocumentLoadListener
+  // (parent-process DocumentChannel), and by DocumentChannelChild/ContentChild
+  // to transfer the resulting channel into the final process.
+  static nsresult CreateRealChannelForDocument(
+      nsIChannel** aChannel, nsIURI* aURI, nsILoadInfo* aLoadInfo,
+      nsIInterfaceRequestor* aCallbacks, nsLoadFlags aLoadFlags,
+      const nsAString& aSrcdoc, nsIURI* aBaseURI);
+
+  // Creates a real (not DocumentChannel) channel, and configures it using the
+  // supplied nsDocShellLoadState.
+  // Configuration options here are ones that should be applied to only the
+  // real channel, especially ones that need to QI to channel subclasses.
+  static bool CreateAndConfigureRealChannelForLoadState(
+      mozilla::dom::BrowsingContext* aBrowsingContext,
+      nsDocShellLoadState* aLoadState, mozilla::net::LoadInfo* aLoadInfo,
+      nsIInterfaceRequestor* aCallbacks, nsDocShell* aDocShell,
+      const mozilla::OriginAttributes& aOriginAttributes,
+      nsLoadFlags aLoadFlags, uint32_t aCacheKey, nsresult& rv,
+      nsIChannel** aChannel);
+
+  // This is used to deal with errors resulting from a failed page load.
+  // Errors are handled as follows:
+  //   1. Check to see if it's a file not found error or bad content
+  //      encoding error.
+  //   2. Send the URI to a keyword server (if enabled)
+  //   3. If the error was DNS failure, then add www and .com to the URI
+  //      (if appropriate).
+  //   4. If the www .com additions don't work, try those with an HTTPS scheme
+  //      (if appropriate).
+  static already_AddRefed<nsIURI> AttemptURIFixup(
+      nsIChannel* aChannel, nsresult aStatus,
+      const mozilla::Maybe<nsCString>& aOriginalURIString, uint32_t aLoadType,
+      bool aIsTopFrame, bool aAllowKeywordFixup, bool aUsePrivateBrowsing,
+      bool aNotifyKeywordSearchLoading = false,
+      nsIInputStream** aNewPostData = nullptr,
+      bool* outWasSchemelessInput = nullptr);
+
+  static already_AddRefed<nsIURI> MaybeFixBadCertDomainErrorURI(
+      nsIChannel* aChannel, nsIURI* aUrl);
+
+  // Takes aStatus and filters out results that should not display
+  // an error page.
+  // If this returns a failed result, then we should display an error
+  // page with that result.
+  // aSkippedUnknownProtocolNavigation will be set to true if we chose
+  // to skip displaying an error page for an NS_ERROR_UNKNOWN_PROTOCOL
+  // navigation.
+  static nsresult FilterStatusForErrorPage(
+      nsresult aStatus, nsIChannel* aChannel, uint32_t aLoadType,
+      bool aIsTopFrame, bool aUseErrorPages, bool aIsInitialDocument,
+      bool* aSkippedUnknownProtocolNavigation = nullptr);
+
+  // Notify consumers of a search being loaded through the observer service:
+  static void MaybeNotifyKeywordSearchLoading(const nsString& aProvider,
+                                              const nsString& aKeyword);
+
+  nsDocShell* GetInProcessChildAt(int32_t aIndex);
+
+  static bool ShouldAddURIVisit(nsIChannel* aChannel);
+
+  /**
+   * Helper function that finds the last URI and its transition flags for a
+   * channel.
+   *
+   * This method first checks the channel's property bag to see if previous
+   * info has been saved. If not, it gives back the referrer of the channel.
+   *
+   * @param aChannel
+   *        The channel we are transitioning to
+   * @param aURI
+   *        Output parameter with the previous URI, not addref'd
+   * @param aChannelRedirectFlags
+   *        If a redirect, output parameter with the previous redirect flags
+   *        from nsIChannelEventSink
+   */
+  static void ExtractLastVisit(nsIChannel* aChannel, nsIURI** aURI,
+                               uint32_t* aChannelRedirectFlags);
+
+  bool HasDocumentViewer() const { return !!mDocumentViewer; }
+
+  static uint32_t ComputeURILoaderFlags(
+      mozilla::dom::BrowsingContext* aBrowsingContext, uint32_t aLoadType);
+
+  void SetLoadingSessionHistoryInfo(
+      const mozilla::dom::LoadingSessionHistoryInfo& aLoadingInfo,
+      bool aNeedToReportActiveAfterLoadingBecomesActive = false);
+  const mozilla::dom::LoadingSessionHistoryInfo*
+  GetLoadingSessionHistoryInfo() {
+    return mLoadingEntry.get();
+  }
+
+  already_AddRefed<nsIInputStream> GetPostDataFromCurrentEntry() const;
+  mozilla::Maybe<uint32_t> GetCacheKeyFromCurrentEntry() const;
+
+  // Loading and/or active entries are only set when session history
+  // in the parent is on.
+  bool FillLoadStateFromCurrentEntry(nsDocShellLoadState& aLoadState);
+
+  static bool ShouldAddToSessionHistory(nsIURI* aURI, nsIChannel* aChannel);
+
+  bool IsOSHE(nsISHEntry* aEntry) const { return mOSHE == aEntry; }
+
+  mozilla::dom::ChildSHistory* GetSessionHistory() {
+    return mBrowsingContext->GetChildSessionHistory();
+  }
+
+  // This returns true only when using session history in parent.
+  bool IsLoadingFromSessionHistory();
+
+  NS_IMETHODIMP OnStartRequest(nsIRequest* aRequest) override;
+  NS_IMETHODIMP OnStopRequest(nsIRequest* aRequest,
+                              nsresult aStatusCode) override;
+
+ private:  // member functions
+  friend class nsAppShellService;
+  friend class nsDSURIContentListener;
+  friend class FramingChecker;
+  friend class OnLinkClickEvent;
+  friend class nsIDocShell;
+  friend class mozilla::dom::BrowsingContext;
+  friend class mozilla::net::DocumentLoadListener;
+  friend class nsGlobalWindowOuter;
+
+  nsDocShell(mozilla::dom::BrowsingContext* aBrowsingContext,
+             uint64_t aContentWindowID);
+
+  static inline uint32_t PRTimeToSeconds(PRTime aTimeUsec) {
+    return uint32_t(aTimeUsec / PR_USEC_PER_SEC);
+  }
+
+  virtual ~nsDocShell();
+
+  //
+  // nsDocLoader
+  //
+
+  virtual void DestroyChildren() override;
+
+  // Overridden from nsDocLoader, this provides more information than the
+  // normal OnStateChange with flags STATE_REDIRECTING
+  virtual void OnRedirectStateChange(nsIChannel* aOldChannel,
+                                     nsIChannel* aNewChannel,
+                                     uint32_t aRedirectFlags,
+                                     uint32_t aStateFlags) override;
+
+  // Override the parent setter from nsDocLoader
+  virtual nsresult SetDocLoaderParent(nsDocLoader* aLoader) override;
+
+  //
+  // Content Viewer Management
+  //
+
+  nsresult EnsureDocumentViewer();
+
+  // aPrincipal can be passed in if the caller wants. If null is
+  // passed in, the about:blank principal will end up being used.
+  // aCSP, if any, will be used for the new about:blank load.
+  nsresult CreateAboutBlankDocumentViewer(
+      nsIPrincipal* aPrincipal, nsIPrincipal* aPartitionedPrincipal,
+      nsIContentSecurityPolicy* aCSP, nsIURI* aBaseURI, bool aIsInitialDocument,
+      const mozilla::Maybe<nsILoadInfo::CrossOriginEmbedderPolicy>& aCOEP =
+          mozilla::Nothing(),
+      bool aTryToSaveOldPresentation = true, bool aCheckPermitUnload = true,
+      mozilla::dom::WindowGlobalChild* aActor = nullptr);
+
+  nsresult CreateDocumentViewer(const nsACString& aContentType,
+                                nsIRequest* aRequest,
+                                nsIStreamListener** aContentHandler);
+
+  nsresult NewDocumentViewerObj(const nsACString& aContentType,
+                                nsIRequest* aRequest, nsILoadGroup* aLoadGroup,
+                                nsIStreamListener** aContentHandler,
+                                nsIDocumentViewer** aViewer);
+
+  already_AddRefed<nsILoadURIDelegate> GetLoadURIDelegate();
+
+  nsresult SetupNewViewer(
+      nsIDocumentViewer* aNewViewer,
+      mozilla::dom::WindowGlobalChild* aWindowActor = nullptr);
+
+  //
+  // Session History
+  //
+
+  // Either aChannel or aOwner must be null. If aChannel is
+  // present, the owner should be gotten from it.
+  // If aCloneChildren is true, then our current session history's
+  // children will be cloned onto the new entry. This should be
+  // used when we aren't actually changing the document while adding
+  // the new session history entry.
+  // aCsp is the CSP to be used for the load. That is *not* the CSP
+  // that will be applied to subresource loads within that document
+  // but the CSP for the document load itself. E.g. if that CSP
+  // includes upgrade-insecure-requests, then the new top-level load
+  // will be upgraded to HTTPS.
+  nsresult AddToSessionHistory(nsIURI* aURI, nsIChannel* aChannel,
+                               nsIPrincipal* aTriggeringPrincipal,
+                               nsIPrincipal* aPrincipalToInherit,
+                               nsIPrincipal* aPartitionedPrincipalToInherit,
+                               nsIContentSecurityPolicy* aCsp,
+                               bool aCloneChildren, nsISHEntry** aNewEntry);
+
+  void UpdateActiveEntry(
+      bool aReplace, const mozilla::Maybe<nsPoint>& aPreviousScrollPos,
+      nsIURI* aURI, nsIURI* aOriginalURI, nsIReferrerInfo* aReferrerInfo,
+      nsIPrincipal* aTriggeringPrincipal, nsIContentSecurityPolicy* aCsp,
+      const nsAString& aTitle, bool aScrollRestorationIsManual,
+      nsIStructuredCloneContainer* aData, bool aURIWasModified);
+
+  nsresult AddChildSHEntry(nsISHEntry* aCloneRef, nsISHEntry* aNewEntry,
+                           int32_t aChildOffset, uint32_t aLoadType,
+                           bool aCloneChildren);
+
+  nsresult AddChildSHEntryToParent(nsISHEntry* aNewEntry, int32_t aChildOffset,
+                                   bool aCloneChildren);
+
+  // Call this method to swap in a new history entry to m[OL]SHE, rather than
+  // setting it directly. This completes the navigation in all docshells
+  // in the case of a subframe navigation.
+  // Returns old mOSHE/mLSHE.
+  already_AddRefed<nsISHEntry> SetHistoryEntry(nsCOMPtr<nsISHEntry>* aPtr,
+                                               nsISHEntry* aEntry);
+
+  // This method calls SetHistoryEntry and updates mOSHE and mLSHE in BC to be
+  // the same as in docshell
+  void SetHistoryEntryAndUpdateBC(const mozilla::Maybe<nsISHEntry*>& aLSHE,
+                                  const mozilla::Maybe<nsISHEntry*>& aOSHE);
+
+  // If aNotifiedBeforeUnloadListeners is true, "beforeunload" event listeners
+  // were notified by the caller and given the chance to abort the navigation,
+  // and should not be notified again.
+  static nsresult ReloadDocument(
+      nsDocShell* aDocShell, mozilla::dom::Document* aDocument,
+      uint32_t aLoadType, mozilla::dom::BrowsingContext* aBrowsingContext,
+      nsIURI* aCurrentURI, nsIReferrerInfo* aReferrerInfo,
+      bool aNotifiedBeforeUnloadListeners = false);
+
+ public:
+  bool IsAboutBlankLoadOntoInitialAboutBlank(nsIURI* aURI,
+                                             bool aInheritPrincipal,
+                                             nsIPrincipal* aPrincipalToInherit);
+
+ private:
+  //
+  // URI Load
+  //
+
+  // Actually open a channel and perform a URI load. Callers need to pass a
+  // non-null aLoadState->TriggeringPrincipal() which initiated the URI load.
+  // Please note that the TriggeringPrincipal will be used for performing
+  // security checks. If aLoadState->URI() is provided by the web, then please
+  // do not pass a SystemPrincipal as the triggeringPrincipal. If
+  // aLoadState()->PrincipalToInherit is null, then no inheritance of any sort
+  // will happen and the load will get a principal based on the URI being
+  // loaded. If the Srcdoc flag is set (INTERNAL_LOAD_FLAGS_IS_SRCDOC), the load
+  // will be considered as a srcdoc load, and the contents of Srcdoc will be
+  // loaded instead of the URI. aLoadState->OriginalURI() will be set as the
+  // originalURI on the channel that does the load. If OriginalURI is null, URI
+  // will be set as the originalURI. If LoadReplace is true, LOAD_REPLACE flag
+  // will be set on the nsIChannel.
+  // If `aCacheKey` is supplied, use it for the session history entry.
+  nsresult DoURILoad(nsDocShellLoadState* aLoadState,
+                     mozilla::Maybe<uint32_t> aCacheKey, nsIRequest** aRequest);
+
+  static nsresult AddHeadersToChannel(nsIInputStream* aHeadersData,
+                                      nsIChannel* aChannel);
+
+  nsresult OpenInitializedChannel(nsIChannel* aChannel,
+                                  nsIURILoader* aURILoader,
+                                  uint32_t aOpenFlags);
+  nsresult OpenRedirectedChannel(nsDocShellLoadState* aLoadState);
+
+  void UpdateMixedContentChannelForNewLoad(nsIChannel* aChannel);
+
+  MOZ_CAN_RUN_SCRIPT
+  nsresult ScrollToAnchor(bool aCurHasRef, bool aNewHasRef,
+                          nsACString& aNewHash, uint32_t aLoadType);
+
+  // This returns the load type for a form submission (see
+  // https://html.spec.whatwg.org/#form-submission-algorithm). The load type
+  // should be set as soon as the target BC has been determined.
+  uint32_t GetLoadTypeForFormSubmission(
+      mozilla::dom::BrowsingContext* aTargetBC,
+      nsDocShellLoadState* aLoadState);
+
+ private:
+  // Returns true if it is the caller's responsibility to ensure
+  // FireOnLocationChange is called.
+  // In all other cases false is returned.
+  // Either aChannel or aTriggeringPrincipal must be null. If aChannel is
+  // present, the owner should be gotten from it.
+  // If OnNewURI calls AddToSessionHistory, it will pass its
+  // aCloneSHChildren argument as aCloneChildren.
+  // aCsp is the CSP to be used for the load. That is *not* the CSP
+  // that will be applied to subresource loads within that document
+  // but the CSP for the document load itself. E.g. if that CSP
+  // includes upgrade-insecure-requests, then the new top-level load
+  // will be upgraded to HTTPS.
+  bool OnNewURI(nsIURI* aURI, nsIChannel* aChannel,
+                nsIPrincipal* aTriggeringPrincipal,
+                nsIPrincipal* aPrincipalToInherit,
+                nsIPrincipal* aPartitionedPrincipalToInherit,
+                nsIContentSecurityPolicy* aCsp, bool aAddToGlobalHistory,
+                bool aCloneSHChildren);
+
+ public:
+  // If wireframe collection is enabled, will attempt to gather the
+  // wireframe for the document.
+  mozilla::Maybe<mozilla::dom::Wireframe> GetWireframe();
+
+  // If wireframe collection is enabled, will attempt to gather the
+  // wireframe for the document and stash it inside of the active history
+  // entry. Returns true if wireframes were collected.
+  bool CollectWireframe();
+
+  // Helper method that is called when a new document (including any
+  // sub-documents - ie. frames) has been completely loaded.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  nsresult EndPageLoad(nsIWebProgress* aProgress, nsIChannel* aChannel,
+                       nsresult aResult);
+
+  // Builds an error page URI (e.g. about:neterror?etc) for the given aURI
+  // and displays it via the LoadErrorPage() overload below.
+  nsresult LoadErrorPage(nsIURI* aURI, const char16_t* aURL,
+                         const char* aErrorPage, const char* aErrorType,
+                         const char16_t* aDescription, const char* aCSSClass,
+                         nsIChannel* aFailedChannel);
+
+  // This method directly loads aErrorURI as an error page. aFailedURI and
+  // aFailedChannel come from DisplayLoadError() or the LoadErrorPage() overload
+  // above.
+  nsresult LoadErrorPage(nsIURI* aErrorURI, nsIURI* aFailedURI,
+                         nsIChannel* aFailedChannel);
+
+  bool DisplayLoadError(nsresult aError, nsIURI* aURI, const char16_t* aURL,
+                        nsIChannel* aFailedChannel) {
+    bool didDisplayLoadError = false;
+    DisplayLoadError(aError, aURI, aURL, aFailedChannel, &didDisplayLoadError);
+    return didDisplayLoadError;
+  }
+
+  //
+  // Uncategorized
+  //
+
+  // Get the principal that we'll set on the channel if we're inheriting. If
+  // aConsiderCurrentDocument is true, we try to use the current document if
+  // at all possible. If that fails, we fall back on the parent document.
+  // If that fails too, we force creation of a content viewer and use the
+  // resulting principal. If aConsiderCurrentDocument is false, we just look
+  // at the parent.
+  // If aConsiderPartitionedPrincipal is true, we consider the partitioned
+  // principal instead of the node principal.
+  nsIPrincipal* GetInheritedPrincipal(
+      bool aConsiderCurrentDocument,
+      bool aConsiderPartitionedPrincipal = false);
+
+  /**
+   * Helper function that caches a URI and a transition for saving later.
+   *
+   * @param aChannel
+   *        Channel that will have these properties saved
+   * @param aURI
+   *        The URI to save for later
+   * @param aChannelRedirectFlags
+   *        The nsIChannelEventSink redirect flags to save for later
+   */
+  static void SaveLastVisit(nsIChannel* aChannel, nsIURI* aURI,
+                            uint32_t aChannelRedirectFlags);
+
+  /**
+   * Helper function for adding a URI visit using IHistory.
+   *
+   * The IHistory API maintains chains of visits, tracking both HTTP referrers
+   * and redirects for a user session. VisitURI requires the current URI and
+   * the previous URI in the chain.
+   *
+   * Visits can be saved either during a redirect or when the request has
+   * reached its final destination. The previous URI in the visit may be
+   * from another redirect.
+   *
+   * @pre aURI is not null.
+   *
+   * @param aURI
+   *        The URI that was just visited
+   * @param aPreviousURI
+   *        The previous URI of this visit
+   * @param aChannelRedirectFlags
+   *        For redirects, the redirect flags from nsIChannelEventSink
+   *        (0 otherwise)
+   * @param aResponseStatus
+   *        For HTTP channels, the response code (0 otherwise).
+   */
+  void AddURIVisit(nsIURI* aURI, nsIURI* aPreviousURI,
+                   uint32_t aChannelRedirectFlags,
+                   uint32_t aResponseStatus = 0);
+
+  /**
+   * Internal helper funtion
+   */
+  static void InternalAddURIVisit(
+      nsIURI* aURI, nsIURI* aPreviousURI, uint32_t aChannelRedirectFlags,
+      uint32_t aResponseStatus, mozilla::dom::BrowsingContext* aBrowsingContext,
+      nsIWidget* aWidget, uint32_t aLoadType, bool aWasUpgraded);
+
+  static already_AddRefed<nsIURIFixupInfo> KeywordToURI(
+      const nsACString& aKeyword, bool aIsPrivateContext);
+
+  // Sets the current document's current state object to the given SHEntry's
+  // state object. The current state object is eventually given to the page
+  // in the PopState event.
+  void SetDocCurrentStateObj(nsISHEntry* aShEntry,
+                             mozilla::dom::SessionHistoryInfo* aInfo);
+
+  // Returns true if would have called FireOnLocationChange,
+  // but did not because aFireOnLocationChange was false on entry.
+  // In this case it is the caller's responsibility to ensure
+  // FireOnLocationChange is called.
+  // In all other cases false is returned.
+  bool SetCurrentURI(nsIURI* aURI, nsIRequest* aRequest,
+                     bool aFireOnLocationChange, bool aIsInitialAboutBlank,
+                     uint32_t aLocationFlags);
+
+  // The following methods deal with saving and restoring content viewers
+  // in session history.
+
+  // mDocumentViewer points to the current content viewer associated with
+  // this docshell. When loading a new document, the content viewer is
+  // either destroyed or stored into a session history entry. To make sure
+  // that destruction happens in a controlled fashion, a given content viewer
+  // is always owned in exactly one of these ways:
+  //   1) The content viewer is active and owned by a docshell's
+  //      mDocumentViewer.
+  //   2) The content viewer is still being displayed while we begin loading
+  //      a new document. The content viewer is owned by the _new_
+  //      content viewer's mPreviousViewer, and has a pointer to the
+  //      nsISHEntry where it will eventually be stored. The content viewer
+  //      has been close()d by the docshell, which detaches the document from
+  //      the window object.
+  //   3) The content viewer is cached in session history. The nsISHEntry
+  //      has the only owning reference to the content viewer. The viewer
+  //      has released its nsISHEntry pointer to prevent circular ownership.
+  //
+  // When restoring a content viewer from session history, open() is called
+  // to reattach the document to the window object. The content viewer is
+  // then placed into mDocumentViewer and removed from the history entry.
+  // (mDocumentViewer is put into session history as described above, if
+  // applicable).
+
+  // Determines whether we can safely cache the current mDocumentViewer in
+  // session history. This checks a number of factors such as cache policy,
+  // pending requests, and unload handlers.
+  // |aLoadType| should be the load type that will replace the current
+  // presentation. |aNewRequest| should be the request for the document to
+  // be loaded in place of the current document, or null if such a request
+  // has not been created yet. |aNewDocument| should be the document that will
+  // replace the current document.
+  bool CanSavePresentation(uint32_t aLoadType, nsIRequest* aNewRequest,
+                           mozilla::dom::Document* aNewDocument,
+                           bool aReportBFCacheComboTelemetry);
+
+  static void ReportBFCacheComboTelemetry(uint32_t aCombo);
+
+  // Captures the state of the supporting elements of the presentation
+  // (the "window" object, docshell tree, meta-refresh loads, and security
+  // state) and stores them on |mOSHE|.
+  nsresult CaptureState();
+
+  // Begin the toplevel restore process for |aSHEntry|.
+  // This simulates a channel open, and defers the real work until
+  // RestoreFromHistory is called from a PLEvent.
+  nsresult RestorePresentation(nsISHEntry* aSHEntry, bool* aRestoring);
+
+  // Call BeginRestore(nullptr, false) for each child of this shell.
+  nsresult BeginRestoreChildren();
+
+  // Method to get our current position and size without flushing
+  void DoGetPositionAndSize(int32_t* aX, int32_t* aY, int32_t* aWidth,
+                            int32_t* aHeight);
+
+  // Call this when a URI load is handed to us (via OnLinkClick or
+  // InternalLoad). This makes sure that we're not inside unload, or that if
+  // we are it's still OK to load this URI.
+  bool IsOKToLoadURI(nsIURI* aURI);
+
+  // helpers for executing commands
+  nsresult GetControllerForCommand(const char* aCommand,
+                                   nsIController** aResult);
+
+  // Possibly create a ClientSource object to represent an initial about:blank
+  // window that has not been allocated yet.  Normally we try not to create
+  // this about:blank window until something calls GetDocument().  We still need
+  // the ClientSource to exist for this conceptual window, though.
+  //
+  // The ClientSource is created with the given principal if specified.  If
+  // the principal is not provided we will attempt to inherit it when we
+  // are sure it will match what the real about:blank window principal
+  // would have been.  There are some corner cases where we cannot easily
+  // determine the correct principal and will not create the ClientSource.
+  // In these cases the initial about:blank will appear to not exist until
+  // its real document and window are created.
+  void MaybeCreateInitialClientSource(nsIPrincipal* aPrincipal = nullptr);
+
+  // Determine if a service worker is allowed to control a window in this
+  // docshell with the given URL.  If there are any reasons it should not,
+  // this will return false.  If true is returned then the window *may* be
+  // controlled.  The caller must still consult either the parent controller
+  // or the ServiceWorkerManager to determine if a service worker should
+  // actually control the window.
+  bool ServiceWorkerAllowedToControlWindow(nsIPrincipal* aPrincipal,
+                                           nsIURI* aURI);
+
+  // Return the ClientInfo for the initial about:blank window, if it exists
+  // or we have speculatively created a ClientSource in
+  // MaybeCreateInitialClientSource().  This can return a ClientInfo object
+  // even if GetExtantDoc() returns nullptr.
+  mozilla::Maybe<mozilla::dom::ClientInfo> GetInitialClientInfo() const;
+
+  /**
+   * Initializes mTiming if it isn't yet.
+   * After calling this, mTiming is non-null. This method returns true if the
+   * initialization of the Timing can be reset (basically this is true if a new
+   * Timing object is created).
+   * In case the loading is aborted, MaybeResetInitTiming() can be called
+   * passing the return value of MaybeInitTiming(): if it's possible to reset
+   * the Timing, this method will do it.
+   */
+  [[nodiscard]] bool MaybeInitTiming();
+  void MaybeResetInitTiming(bool aReset);
+
+  // Convenience method for getting our parent docshell. Can return null
+  already_AddRefed<nsDocShell> GetInProcessParentDocshell();
+
+  // Internal implementation of nsIDocShell::FirePageHideNotification.
+  // If aSkipCheckingDynEntries is true, it will not try to remove dynamic
+  // subframe entries. This is to avoid redundant RemoveDynEntries calls in all
+  // children docshells.
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void FirePageHideNotificationInternal(
+      bool aIsUnload, bool aSkipCheckingDynEntries);
+
+  void ThawFreezeNonRecursive(bool aThaw);
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void FirePageHideShowNonRecursive(bool aShow);
+
+  nsresult Dispatch(already_AddRefed<nsIRunnable>&& aRunnable);
+
+  void ReattachEditorToWindow(nsISHEntry* aSHEntry);
+  void ClearFrameHistory(nsISHEntry* aEntry);
+  // Determine if this type of load should update history.
+  static bool ShouldUpdateGlobalHistory(uint32_t aLoadType);
+  void UpdateGlobalHistoryTitle(nsIURI* aURI);
+  bool IsSubframe() { return mBrowsingContext->IsSubframe(); }
+  bool CanSetOriginAttributes();
+  bool ShouldBlockLoadingForBackButton();
+  static bool ShouldDiscardLayoutState(nsIHttpChannel* aChannel);
+  bool HasUnloadedParent();
+  bool JustStartedNetworkLoad();
+  bool NavigationBlockedByPrinting(bool aDisplayErrorDialog = true);
+  bool IsNavigationAllowed(bool aDisplayPrintErrorDialog = true,
+                           bool aCheckIfUnloadFired = true);
+  nsIScrollableFrame* GetRootScrollFrame();
+  nsIChannel* GetCurrentDocChannel();
+  nsresult EnsureScriptEnvironment();
+  nsresult EnsureEditorData();
+  nsresult EnsureTransferableHookData();
+  nsresult EnsureFind();
+  nsresult EnsureCommandHandler();
+  nsresult RefreshURIFromQueue();
+  void RefreshURIToQueue();
+  nsresult Embed(nsIDocumentViewer* aDocumentViewer,
+                 mozilla::dom::WindowGlobalChild* aWindowActor,
+                 bool aIsTransientAboutBlank, bool aPersist,
+                 nsIRequest* aRequest, nsIURI* aPreviousURI);
+  nsPresContext* GetEldestPresContext();
+  nsresult CheckLoadingPermissions();
+  nsresult LoadHistoryEntry(nsISHEntry* aEntry, uint32_t aLoadType,
+                            bool aUserActivation);
+  nsresult LoadHistoryEntry(
+      const mozilla::dom::LoadingSessionHistoryInfo& aEntry, uint32_t aLoadType,
+      bool aUserActivation);
+  nsresult LoadHistoryEntry(nsDocShellLoadState* aLoadState, uint32_t aLoadType,
+                            bool aLoadingCurrentEntry);
+  nsresult GetHttpChannel(nsIChannel* aChannel, nsIHttpChannel** aReturn);
+  nsresult ConfirmRepost(bool* aRepost);
+  nsresult GetPromptAndStringBundle(nsIPrompt** aPrompt,
+                                    nsIStringBundle** aStringBundle);
+  nsresult SetCurScrollPosEx(int32_t aCurHorizontalPos,
+                             int32_t aCurVerticalPos);
+  nsPoint GetCurScrollPos();
+
+  already_AddRefed<mozilla::dom::ChildSHistory> GetRootSessionHistory();
+
+  bool CSSErrorReportingEnabled() const { return mCSSErrorReportingEnabled; }
+
+  // Handles retrieval of subframe session history for nsDocShell::LoadURI. If a
+  // load is requested in a subframe of the current DocShell, the subframe
+  // loadType may need to reflect the loadType of the parent document, or in
+  // some cases (like reloads), the history load may need to be cancelled. See
+  // function comments for in-depth logic descriptions.
+  // Returns true if the method itself deals with the load.
+  bool MaybeHandleSubframeHistory(nsDocShellLoadState* aLoadState,
+                                  bool aContinueHandlingSubframeHistory);
+
+  // If we are passed a named target during InternalLoad, this method handles
+  // moving the load to the browsing context the target name resolves to.
+  nsresult PerformRetargeting(nsDocShellLoadState* aLoadState);
+
+  // Returns one of nsIContentPolicy::TYPE_DOCUMENT,
+  // nsIContentPolicy::TYPE_INTERNAL_IFRAME, or
+  // nsIContentPolicy::TYPE_INTERNAL_FRAME depending on who is responsible for
+  // this docshell.
+  nsContentPolicyType DetermineContentType();
+
+  // If this is an iframe, and the embedder is OOP, then notifes the
+  // embedder that loading has finished and we shouldn't be blocking
+  // load of the embedder. Only called when we fail to load, as we wait
+  // for the load event of our Document before notifying success.
+  //
+  // If aFireFrameErrorEvent is true, then fires an error event at the
+  // embedder element, for both in-process and OOP embedders.
+  void UnblockEmbedderLoadEventForFailure(bool aFireFrameErrorEvent = false);
+
+  struct SameDocumentNavigationState {
+    nsAutoCString mCurrentHash;
+    nsAutoCString mNewHash;
+    bool mCurrentURIHasRef = false;
+    bool mNewURIHasRef = false;
+    bool mSameExceptHashes = false;
+    bool mSecureUpgradeURI = false;
+    bool mHistoryNavBetweenSameDoc = false;
+  };
+
+  // Check to see if we're loading a prior history entry or doing a fragment
+  // navigation in the same document.
+  // NOTE: In case we are doing a fragment navigation, and HTTPS-Only/ -First
+  // mode is enabled and upgraded the underlying document, we update the URI of
+  // aLoadState from HTTP to HTTPS (if neccessary).
+  bool IsSameDocumentNavigation(nsDocShellLoadState* aLoadState,
+                                SameDocumentNavigationState& aState);
+
+  // ... If so, handle the scrolling or other action required instead of
+  // continuing with new document navigation.
+  MOZ_CAN_RUN_SCRIPT
+  nsresult HandleSameDocumentNavigation(nsDocShellLoadState* aLoadState,
+                                        SameDocumentNavigationState& aState,
+                                        bool& aSameDocument);
+
+  uint32_t GetSameDocumentNavigationFlags(nsIURI* aNewURI);
+
+  // Called when the Private Browsing state of a nsDocShell changes.
+  void NotifyPrivateBrowsingChanged();
+
+  // Internal helpers for BrowsingContext to pass update values to nsIDocShell's
+  // LoadGroup.
+  void SetLoadGroupDefaultLoadFlags(nsLoadFlags aLoadFlags);
+
+  void SetTitleOnHistoryEntry(bool aUpdateEntryInSessionHistory);
+
+  void SetScrollRestorationIsManualOnHistoryEntry(nsISHEntry* aSHEntry,
+                                                  bool aIsManual);
+
+  void SetCacheKeyOnHistoryEntry(nsISHEntry* aSHEntry, uint32_t aCacheKey);
+
+  // If the LoadState's URI is a javascript: URI, checks that the triggering
+  // principal subsumes the principal of the current document, and returns
+  // NS_ERROR_DOM_BAD_CROSS_ORIGIN_URI if it does not.
+  nsresult CheckDisallowedJavascriptLoad(nsDocShellLoadState* aLoadState);
+
+  nsresult LoadURI(nsDocShellLoadState* aLoadState, bool aSetNavigating,
+                   bool aContinueHandlingSubframeHistory);
+
+  // Sets the active entry to the current loading entry. aPersist is used in the
+  // case a new session history entry is added to the session history.
+  // aExpired is true if the relevant nsIChannel has its cache token expired.
+  // aCacheKey is the channel's cache key.
+  // aPreviousURI should be the URI that was previously loaded into the
+  // nsDocshell
+  void MoveLoadingToActiveEntry(bool aPersist, bool aExpired,
+                                uint32_t aCacheKey, nsIURI* aPreviousURI);
+
+  void ActivenessMaybeChanged();
+
+  /**
+   * Returns true if `noopener` will be force-enabled by any attempt to create
+   * a popup window, even if rel="opener" is requested.
+   */
+  bool NoopenerForceEnabled();
+
+  bool ShouldOpenInBlankTarget(const nsAString& aOriginalTarget,
+                               nsIURI* aLinkURI, nsIContent* aContent,
+                               bool aIsUserTriggered);
+
+  void RecordSingleChannelId(bool aStartRequest, nsIRequest* aRequest);
+
+  void SetChannelToDisconnectOnPageHide(uint64_t aChannelId) {
+    MOZ_ASSERT(mChannelToDisconnectOnPageHide == 0);
+    mChannelToDisconnectOnPageHide = aChannelId;
+  }
+  void MaybeDisconnectChildListenersOnPageHide();
+
+  /**
+   * Helper for addState and document.open that does just the
+   * history-manipulation guts.
+   *
+   * Arguments the spec defines:
+   *
+   * @param aDocument the document we're manipulating.  This will get the new
+   * URI.
+   * @param aNewURI the new URI.
+   * @param aData The serialized state data.  May be null.
+   * @param aTitle The new title.  May be empty.
+   * @param aReplace whether this should replace the exising SHEntry.
+   *
+   * Arguments we need internally because deriving them from the
+   * others is a bit complicated:
+   *
+   * @param aCurrentURI the current URI we're working with.  Might be null.
+   * @param aEqualURIs whether the two URIs involved are equal.
+   */
+  nsresult UpdateURLAndHistory(mozilla::dom::Document* aDocument,
+                               nsIURI* aNewURI,
+                               nsIStructuredCloneContainer* aData,
+                               const nsAString& aTitle, bool aReplace,
+                               nsIURI* aCurrentURI, bool aEqualURIs);
+
+ private:
+  void SetCurrentURIInternal(nsIURI* aURI);
+
+  // data members
+  nsString mTitle;
+  nsCString mOriginalUriString;
+  nsTObserverArray<nsWeakPtr> mPrivacyObservers;
+  nsTObserverArray<nsWeakPtr> mReflowObservers;
+  nsTObserverArray<nsWeakPtr> mScrollObservers;
+  mozilla::UniquePtr<mozilla::dom::ClientSource> mInitialClientSource;
+  nsCOMPtr<nsINetworkInterceptController> mInterceptController;
+  RefPtr<nsDOMNavigationTiming> mTiming;
+  RefPtr<nsDSURIContentListener> mContentListener;
+  RefPtr<nsGlobalWindowOuter> mScriptGlobal;
+  nsCOMPtr<nsIPrincipal> mParentCharsetPrincipal;
+  // The following 3 lists contain either nsITimer or nsRefreshTimer objects.
+  // URIs to refresh are collected to mRefreshURIList.
+  nsCOMPtr<nsIMutableArray> mRefreshURIList;
+  // mSavedRefreshURIList is used to move the entries from mRefreshURIList to
+  // mOSHE.
+  nsCOMPtr<nsIMutableArray> mSavedRefreshURIList;
+  // BFCache-in-parent implementation caches the entries in
+  // mBFCachedRefreshURIList.
+  nsCOMPtr<nsIMutableArray> mBFCachedRefreshURIList;
+  uint64_t mContentWindowID;
+  nsCOMPtr<nsIDocumentViewer> mDocumentViewer;
+  nsCOMPtr<nsIWidget> mParentWidget;
+  RefPtr<mozilla::dom::ChildSHistory> mSessionHistory;
+  nsCOMPtr<nsIWebBrowserFind> mFind;
+  RefPtr<nsCommandManager> mCommandManager;
+  RefPtr<mozilla::dom::BrowsingContext> mBrowsingContext;
+
+  // Weak reference to our BrowserChild actor.
+  nsWeakPtr mBrowserChild;
+
+  // Dimensions of the docshell
+  nsIntRect mBounds;
+
+  /**
+   * Content-Type Hint of the most-recently initiated load. Used for
+   * session history entries.
+   */
+  nsCString mContentTypeHint;
+
+  // mCurrentURI should be marked immutable on set if possible.
+  // Change mCurrentURI only through SetCurrentURIInternal method.
+  nsCOMPtr<nsIURI> mCurrentURI;
+  nsCOMPtr<nsIReferrerInfo> mReferrerInfo;
+
+#ifdef DEBUG
+  // We're counting the number of |nsDocShells| to help find leaks
+  static unsigned long gNumberOfDocShells;
+
+  nsCOMPtr<nsIURI> mLastOpenedURI;
+#endif
+
+  // Reference to the SHEntry for this docshell until the page is destroyed.
+  // Somebody give me better name
+  // Only used when SHIP is disabled.
+  nsCOMPtr<nsISHEntry> mOSHE;
+
+  // Reference to the SHEntry for this docshell until the page is loaded
+  // Somebody give me better name.
+  // If mLSHE is non-null, non-pushState subframe loads don't create separate
+  // root history entries. That is, frames loaded during the parent page
+  // load don't generate history entries the way frame navigation after the
+  // parent has loaded does. (This isn't the only purpose of mLSHE.)
+  // Only used when SHIP is disabled.
+  nsCOMPtr<nsISHEntry> mLSHE;
+
+  // These are only set when fission.sessionHistoryInParent is set.
+  mozilla::UniquePtr<mozilla::dom::SessionHistoryInfo> mActiveEntry;
+  bool mActiveEntryIsLoadingFromSessionHistory = false;
+  // mLoadingEntry is set when we're about to start loading. Whenever
+  // setting mLoadingEntry, be sure to also set
+  // mNeedToReportActiveAfterLoadingBecomesActive.
+  mozilla::UniquePtr<mozilla::dom::LoadingSessionHistoryInfo> mLoadingEntry;
+
+  // Holds a weak pointer to a RestorePresentationEvent object if any that
+  // holds a weak pointer back to us. We use this pointer to possibly revoke
+  // the event whenever necessary.
+  nsRevocableEventPtr<RestorePresentationEvent> mRestorePresentationEvent;
+
+  // Editor data, if this document is designMode or contentEditable.
+  mozilla::UniquePtr<nsDocShellEditorData> mEditorData;
+
+  // The URI we're currently loading. This is only relevant during the
+  // firing of a pagehide/unload. The caller of FirePageHideNotification()
+  // is responsible for setting it and unsetting it. It may be null if the
+  // pagehide/unload is happening for some reason other than just loading a
+  // new URI.
+  nsCOMPtr<nsIURI> mLoadingURI;
+
+  // Set in LoadErrorPage from the method argument and used later
+  // in CreateDocumentViewer. We have to delay an shistory entry creation
+  // for which these objects are needed.
+  nsCOMPtr<nsIURI> mFailedURI;
+  nsCOMPtr<nsIChannel> mFailedChannel;
+
+  mozilla::UniquePtr<mozilla::gfx::Matrix5x4> mColorMatrix;
+
+  const mozilla::Encoding* mParentCharset;
+
+  // WEAK REFERENCES BELOW HERE.
+  // Note these are intentionally not addrefd. Doing so will create a cycle.
+  // For that reasons don't use nsCOMPtr.
+
+  nsIDocShellTreeOwner* mTreeOwner;  // Weak Reference
+
+  RefPtr<mozilla::dom::EventTarget> mChromeEventHandler;
+
+  mozilla::ScrollbarPreference mScrollbarPref;  // persistent across doc loads
+
+  eCharsetReloadState mCharsetReloadState;
+
+  int32_t mParentCharsetSource;
+  mozilla::CSSIntSize mFrameMargins;
+
+  // This can either be a content docshell or a chrome docshell.
+  const int32_t mItemType;
+
+  // Index into the nsISHEntry array, indicating the previous and current
+  // entry at the time that this DocShell begins to load. Consequently
+  // root docshell's indices can differ from child docshells'.
+  int32_t mPreviousEntryIndex;
+  int32_t mLoadedEntryIndex;
+
+  BusyFlags mBusyFlags;
+  AppType mAppType;
+  uint32_t mLoadType;
+  uint32_t mFailedLoadType;
+
+  // Whether or not handling of the <meta name="viewport"> tag is overridden.
+  // Possible values are defined as constants in nsIDocShell.idl.
+  MetaViewportOverride mMetaViewportOverride;
+
+  // See WindowGlobalParent::mSingleChannelId.
+  mozilla::Maybe<uint64_t> mSingleChannelId;
+  uint32_t mRequestForBlockingFromBFCacheCount = 0;
+
+  uint64_t mChannelToDisconnectOnPageHide;
+
+  uint32_t mPendingReloadCount = 0;
+
+  // The following two fields cannot be declared as bit fields
+  // because of uses with AutoRestore.
+  bool mCreatingDocument;  // (should be) debugging only
+#ifdef DEBUG
+  bool mInEnsureScriptEnv;
+  uint64_t mDocShellID = 0;
+#endif
+
+  bool mInitialized : 1;
+  bool mAllowSubframes : 1;
+  bool mAllowMetaRedirects : 1;
+  bool mAllowImages : 1;
+  bool mAllowMedia : 1;
+  bool mAllowDNSPrefetch : 1;
+  bool mAllowWindowControl : 1;
+  bool mCSSErrorReportingEnabled : 1;
+  bool mAllowAuth : 1;
+  bool mAllowKeywordFixup : 1;
+  bool mDisableMetaRefreshWhenInactive : 1;
+  bool mIsAppTab : 1;
+  bool mWindowDraggingAllowed : 1;
+  bool mInFrameSwap : 1;
+
+  // This boolean is set to true right before we fire pagehide and generally
+  // unset when we embed a new content viewer. While it's true no navigation
+  // is allowed in this docshell.
+  bool mFiredUnloadEvent : 1;
+
+  // this flag is for bug #21358. a docshell may load many urls
+  // which don't result in new documents being created (i.e. a new
+  // content viewer) we want to make sure we don't call a on load
+  // event more than once for a given content viewer.
+  bool mEODForCurrentDocument : 1;
+  bool mURIResultedInDocument : 1;
+
+  bool mIsBeingDestroyed : 1;
+
+  bool mIsExecutingOnLoadHandler : 1;
+
+  // Indicates to CreateDocumentViewer() that it is safe to cache the old
+  // presentation of the page, and to SetupNewViewer() that the old viewer
+  // should be passed a SHEntry to save itself into.
+  // Only used with SHIP disabled.
+  bool mSavingOldViewer : 1;
+
+  bool mInvisible : 1;
+  bool mHasLoadedNonBlankURI : 1;
+
+  // This flag means that mTiming has been initialized but nulled out.
+  // We will check the innerWin's timing before creating a new one
+  // in MaybeInitTiming()
+  bool mBlankTiming : 1;
+
+  // This flag indicates when the title is valid for the current URI.
+  bool mTitleValidForCurrentURI : 1;
+
+  // If mWillChangeProcess is set to true, then when the docshell is destroyed,
+  // we prepare the browsing context to change process.
+  bool mWillChangeProcess : 1;
+
+  // This flag indicates whether or not the DocShell is currently executing an
+  // nsIWebNavigation navigation method.
+  bool mIsNavigating : 1;
+
+  // Whether we have a pending encoding autodetection request from the
+  // menu for all encodings.
+  bool mForcedAutodetection : 1;
+
+  /*
+   * Set to true if we're checking session history (in the parent process) for
+   * a possible history load. Used only with iframes.
+   */
+  bool mCheckingSessionHistory : 1;
+
+  // Whether mBrowsingContext->SetActiveSessionHistoryEntry() needs to be called
+  // when the loading entry becomes the active entry. This is used for the
+  // initial about:blank-replacing about:blank in order to make the history
+  // length WPTs pass.
+  bool mNeedToReportActiveAfterLoadingBecomesActive : 1;
+};
+
+inline nsISupports* ToSupports(nsDocShell* aDocShell) {
+  return static_cast<nsIDocumentLoader*>(aDocShell);
+}
+
+#endif /* nsDocShell_h__ */
diff --git a/docshell/base/nsDocShellEditorData.cpp b/docshell/base/nsDocShellEditorData.cpp
new file mode 100644
index 0000000000..6fe132a977
--- /dev/null
+++ b/docshell/base/nsDocShellEditorData.cpp
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDocShellEditorData.h"
+
+#include "mozilla/dom/Document.h"
+#include "mozilla/HTMLEditor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsComponentManagerUtils.h"
+#include "nsPIDOMWindow.h"
+#include "nsEditingSession.h"
+#include "nsIDocShell.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+nsDocShellEditorData::nsDocShellEditorData(nsIDocShell* aOwningDocShell)
+    : mDocShell(aOwningDocShell),
+      mDetachedEditingState(Document::EditingState::eOff),
+      mMakeEditable(false),
+      mIsDetached(false),
+      mDetachedMakeEditable(false) {
+  NS_ASSERTION(mDocShell, "Where is my docShell?");
+}
+
+nsDocShellEditorData::~nsDocShellEditorData() { TearDownEditor(); }
+
+void nsDocShellEditorData::TearDownEditor() {
+  if (mHTMLEditor) {
+    RefPtr<HTMLEditor> htmlEditor = std::move(mHTMLEditor);
+    htmlEditor->PreDestroy();
+  }
+  mEditingSession = nullptr;
+  mIsDetached = false;
+}
+
+nsresult nsDocShellEditorData::MakeEditable(bool aInWaitForUriLoad) {
+  if (mMakeEditable) {
+    return NS_OK;
+  }
+
+  // if we are already editable, and are getting turned off,
+  // nuke the editor.
+  if (mHTMLEditor) {
+    NS_WARNING("Destroying existing editor on frame");
+
+    RefPtr<HTMLEditor> htmlEditor = std::move(mHTMLEditor);
+    htmlEditor->PreDestroy();
+  }
+
+  if (aInWaitForUriLoad) {
+    mMakeEditable = true;
+  }
+  return NS_OK;
+}
+
+bool nsDocShellEditorData::GetEditable() {
+  return mMakeEditable || (mHTMLEditor != nullptr);
+}
+
+nsEditingSession* nsDocShellEditorData::GetEditingSession() {
+  EnsureEditingSession();
+
+  return mEditingSession.get();
+}
+
+nsresult nsDocShellEditorData::SetHTMLEditor(HTMLEditor* aHTMLEditor) {
+  // destroy any editor that we have. Checks for equality are
+  // necessary to ensure that assigment into the nsCOMPtr does
+  // not temporarily reduce the refCount of the editor to zero
+  if (mHTMLEditor == aHTMLEditor) {
+    return NS_OK;
+  }
+
+  if (mHTMLEditor) {
+    RefPtr<HTMLEditor> htmlEditor = std::move(mHTMLEditor);
+    htmlEditor->PreDestroy();
+    MOZ_ASSERT(!mHTMLEditor,
+               "Nested call of nsDocShellEditorData::SetHTMLEditor() detected");
+  }
+
+  mHTMLEditor = aHTMLEditor;  // owning addref
+  if (!mHTMLEditor) {
+    mMakeEditable = false;
+  }
+
+  return NS_OK;
+}
+
+// This creates the editing session on the content docShell that owns 'this'.
+void nsDocShellEditorData::EnsureEditingSession() {
+  NS_ASSERTION(mDocShell, "Should have docShell here");
+  NS_ASSERTION(!mIsDetached, "This will stomp editing session!");
+
+  if (!mEditingSession) {
+    mEditingSession = new nsEditingSession();
+  }
+}
+
+nsresult nsDocShellEditorData::DetachFromWindow() {
+  NS_ASSERTION(mEditingSession,
+               "Can't detach when we don't have a session to detach!");
+
+  nsCOMPtr<nsPIDOMWindowOuter> domWindow =
+      mDocShell ? mDocShell->GetWindow() : nullptr;
+  nsresult rv = mEditingSession->DetachFromWindow(domWindow);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mIsDetached = true;
+  mDetachedMakeEditable = mMakeEditable;
+  mMakeEditable = false;
+
+  nsCOMPtr<dom::Document> doc = domWindow->GetDoc();
+  mDetachedEditingState = doc->GetEditingState();
+
+  mDocShell = nullptr;
+
+  return NS_OK;
+}
+
+nsresult nsDocShellEditorData::ReattachToWindow(nsIDocShell* aDocShell) {
+  mDocShell = aDocShell;
+
+  nsCOMPtr<nsPIDOMWindowOuter> domWindow =
+      mDocShell ? mDocShell->GetWindow() : nullptr;
+  nsresult rv = mEditingSession->ReattachToWindow(domWindow);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mIsDetached = false;
+  mMakeEditable = mDetachedMakeEditable;
+
+  RefPtr<dom::Document> doc = domWindow->GetDoc();
+  doc->SetEditingState(mDetachedEditingState);
+
+  return NS_OK;
+}
diff --git a/docshell/base/nsDocShellEditorData.h b/docshell/base/nsDocShellEditorData.h
new file mode 100644
index 0000000000..27f840675b
--- /dev/null
+++ b/docshell/base/nsDocShellEditorData.h
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef nsDocShellEditorData_h__
+#define nsDocShellEditorData_h__
+
+#ifndef nsCOMPtr_h___
+#  include "nsCOMPtr.h"
+#endif
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/Document.h"
+
+class nsIDocShell;
+class nsEditingSession;
+
+namespace mozilla {
+class HTMLEditor;
+}
+
+class nsDocShellEditorData {
+ public:
+  explicit nsDocShellEditorData(nsIDocShell* aOwningDocShell);
+  ~nsDocShellEditorData();
+
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY nsresult MakeEditable(bool aWaitForUriLoad);
+  bool GetEditable();
+  nsEditingSession* GetEditingSession();
+  mozilla::HTMLEditor* GetHTMLEditor() const { return mHTMLEditor; }
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY nsresult
+  SetHTMLEditor(mozilla::HTMLEditor* aHTMLEditor);
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void TearDownEditor();
+  nsresult DetachFromWindow();
+  nsresult ReattachToWindow(nsIDocShell* aDocShell);
+  bool WaitingForLoad() const { return mMakeEditable; }
+
+ protected:
+  void EnsureEditingSession();
+
+  // The doc shell that owns us. Weak ref, since it always outlives us.
+  nsIDocShell* mDocShell;
+
+  // Only present for the content root docShell. Session is owned here.
+  RefPtr<nsEditingSession> mEditingSession;
+
+  // If this frame is editable, store HTML editor here. It's owned here.
+  RefPtr<mozilla::HTMLEditor> mHTMLEditor;
+
+  // Backup for the corresponding HTMLDocument's  editing state while
+  // the editor is detached.
+  mozilla::dom::Document::EditingState mDetachedEditingState;
+
+  // Indicates whether to make an editor after a url load.
+  bool mMakeEditable;
+
+  // Denotes if the editor is detached from its window. The editor is detached
+  // while it's stored in the session history bfcache.
+  bool mIsDetached;
+
+  // Backup for mMakeEditable while the editor is detached.
+  bool mDetachedMakeEditable;
+};
+
+#endif  // nsDocShellEditorData_h__
diff --git a/docshell/base/nsDocShellEnumerator.cpp b/docshell/base/nsDocShellEnumerator.cpp
new file mode 100644
index 0000000000..5ad0ad35e6
--- /dev/null
+++ b/docshell/base/nsDocShellEnumerator.cpp
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDocShellEnumerator.h"
+
+#include "nsDocShell.h"
+
+using namespace mozilla;
+
+nsDocShellEnumerator::nsDocShellEnumerator(
+    nsDocShellEnumerator::EnumerationDirection aDirection,
+    int32_t aDocShellType, nsDocShell& aRootItem)
+    : mRootItem(&aRootItem),
+      mDocShellType(aDocShellType),
+      mDirection(aDirection) {}
+
+nsresult nsDocShellEnumerator::BuildDocShellArray(
+    nsTArray<RefPtr<nsIDocShell>>& aItemArray) {
+  MOZ_ASSERT(mRootItem);
+
+  aItemArray.Clear();
+
+  if (mDirection == EnumerationDirection::Forwards) {
+    return BuildArrayRecursiveForwards(mRootItem, aItemArray);
+  }
+  MOZ_ASSERT(mDirection == EnumerationDirection::Backwards);
+  return BuildArrayRecursiveBackwards(mRootItem, aItemArray);
+}
+
+nsresult nsDocShellEnumerator::BuildArrayRecursiveForwards(
+    nsDocShell* aItem, nsTArray<RefPtr<nsIDocShell>>& aItemArray) {
+  nsresult rv;
+
+  // add this item to the array
+  if (mDocShellType == nsIDocShellTreeItem::typeAll ||
+      aItem->ItemType() == mDocShellType) {
+    if (!aItemArray.AppendElement(aItem, fallible)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+
+  int32_t numChildren = aItem->ChildCount();
+
+  for (int32_t i = 0; i < numChildren; ++i) {
+    RefPtr<nsDocShell> curChild = aItem->GetInProcessChildAt(i);
+    MOZ_ASSERT(curChild);
+
+    rv = BuildArrayRecursiveForwards(curChild, aItemArray);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShellEnumerator::BuildArrayRecursiveBackwards(
+    nsDocShell* aItem, nsTArray<RefPtr<nsIDocShell>>& aItemArray) {
+  nsresult rv;
+
+  uint32_t numChildren = aItem->ChildCount();
+
+  for (int32_t i = numChildren - 1; i >= 0; --i) {
+    RefPtr<nsDocShell> curChild = aItem->GetInProcessChildAt(i);
+    MOZ_ASSERT(curChild);
+
+    rv = BuildArrayRecursiveBackwards(curChild, aItemArray);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+
+  // add this item to the array
+  if (mDocShellType == nsIDocShellTreeItem::typeAll ||
+      aItem->ItemType() == mDocShellType) {
+    if (!aItemArray.AppendElement(aItem, fallible)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+
+  return NS_OK;
+}
diff --git a/docshell/base/nsDocShellEnumerator.h b/docshell/base/nsDocShellEnumerator.h
new file mode 100644
index 0000000000..668ddee7e9
--- /dev/null
+++ b/docshell/base/nsDocShellEnumerator.h
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDocShellEnumerator_h___
+#define nsDocShellEnumerator_h___
+
+#include "nsTArray.h"
+
+class nsDocShell;
+class nsIDocShell;
+
+class MOZ_STACK_CLASS nsDocShellEnumerator {
+ public:
+  enum class EnumerationDirection : uint8_t { Forwards, Backwards };
+
+  nsDocShellEnumerator(EnumerationDirection aDirection, int32_t aDocShellType,
+                       nsDocShell& aRootItem);
+
+ public:
+  nsresult BuildDocShellArray(nsTArray<RefPtr<nsIDocShell>>& aItemArray);
+
+ private:
+  nsresult BuildArrayRecursiveForwards(
+      nsDocShell* aItem, nsTArray<RefPtr<nsIDocShell>>& aItemArray);
+  nsresult BuildArrayRecursiveBackwards(
+      nsDocShell* aItem, nsTArray<RefPtr<nsIDocShell>>& aItemArray);
+
+ private:
+  const RefPtr<nsDocShell> mRootItem;
+
+  const int32_t mDocShellType;  // only want shells of this type
+
+  const EnumerationDirection mDirection;
+};
+
+#endif  // nsDocShellEnumerator_h___
diff --git a/docshell/base/nsDocShellLoadState.cpp b/docshell/base/nsDocShellLoadState.cpp
new file mode 100644
index 0000000000..587617e73d
--- /dev/null
+++ b/docshell/base/nsDocShellLoadState.cpp
@@ -0,0 +1,1325 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDocShellLoadState.h"
+#include "nsIDocShell.h"
+#include "nsDocShell.h"
+#include "nsIProtocolHandler.h"
+#include "nsISHEntry.h"
+#include "nsIURIFixup.h"
+#include "nsIWebNavigation.h"
+#include "nsIChannel.h"
+#include "nsIURLQueryStringStripper.h"
+#include "nsIXULRuntime.h"
+#include "nsNetUtil.h"
+#include "nsQueryObject.h"
+#include "ReferrerInfo.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Components.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/LoadURIOptionsBinding.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/StaticPrefs_fission.h"
+#include "mozilla/Telemetry.h"
+
+#include "mozilla/OriginAttributes.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/StaticPtr.h"
+
+#include "mozilla/dom/PContent.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// Global reference to the URI fixup service.
+static mozilla::StaticRefPtr<nsIURIFixup> sURIFixup;
+
+nsDocShellLoadState::nsDocShellLoadState(nsIURI* aURI)
+    : nsDocShellLoadState(aURI, nsContentUtils::GenerateLoadIdentifier()) {}
+
+nsDocShellLoadState::nsDocShellLoadState(
+    const DocShellLoadStateInit& aLoadState, mozilla::ipc::IProtocol* aActor,
+    bool* aReadSuccess)
+    : mNotifiedBeforeUnloadListeners(false),
+      mLoadIdentifier(aLoadState.LoadIdentifier()) {
+  // If we return early, we failed to read in the data.
+  *aReadSuccess = false;
+  if (!aLoadState.URI()) {
+    MOZ_ASSERT_UNREACHABLE("Cannot create a LoadState with a null URI!");
+    return;
+  }
+
+  mResultPrincipalURI = aLoadState.ResultPrincipalURI();
+  mResultPrincipalURIIsSome = aLoadState.ResultPrincipalURIIsSome();
+  mKeepResultPrincipalURIIfSet = aLoadState.KeepResultPrincipalURIIfSet();
+  mLoadReplace = aLoadState.LoadReplace();
+  mInheritPrincipal = aLoadState.InheritPrincipal();
+  mPrincipalIsExplicit = aLoadState.PrincipalIsExplicit();
+  mForceAllowDataURI = aLoadState.ForceAllowDataURI();
+  mIsExemptFromHTTPSFirstMode = aLoadState.IsExemptFromHTTPSFirstMode();
+  mOriginalFrameSrc = aLoadState.OriginalFrameSrc();
+  mIsFormSubmission = aLoadState.IsFormSubmission();
+  mLoadType = aLoadState.LoadType();
+  mTarget = aLoadState.Target();
+  mTargetBrowsingContext = aLoadState.TargetBrowsingContext();
+  mLoadFlags = aLoadState.LoadFlags();
+  mInternalLoadFlags = aLoadState.InternalLoadFlags();
+  mFirstParty = aLoadState.FirstParty();
+  mHasValidUserGestureActivation = aLoadState.HasValidUserGestureActivation();
+  mAllowFocusMove = aLoadState.AllowFocusMove();
+  mTypeHint = aLoadState.TypeHint();
+  mFileName = aLoadState.FileName();
+  mIsFromProcessingFrameAttributes =
+      aLoadState.IsFromProcessingFrameAttributes();
+  mReferrerInfo = aLoadState.ReferrerInfo();
+  mURI = aLoadState.URI();
+  mOriginalURI = aLoadState.OriginalURI();
+  mSourceBrowsingContext = aLoadState.SourceBrowsingContext();
+  mBaseURI = aLoadState.BaseURI();
+  mTriggeringPrincipal = aLoadState.TriggeringPrincipal();
+  mPrincipalToInherit = aLoadState.PrincipalToInherit();
+  mPartitionedPrincipalToInherit = aLoadState.PartitionedPrincipalToInherit();
+  mTriggeringSandboxFlags = aLoadState.TriggeringSandboxFlags();
+  mTriggeringWindowId = aLoadState.TriggeringWindowId();
+  mTriggeringStorageAccess = aLoadState.TriggeringStorageAccess();
+  mTriggeringRemoteType = aLoadState.TriggeringRemoteType();
+  mWasSchemelessInput = aLoadState.WasSchemelessInput();
+  mCsp = aLoadState.Csp();
+  mOriginalURIString = aLoadState.OriginalURIString();
+  mCancelContentJSEpoch = aLoadState.CancelContentJSEpoch();
+  mPostDataStream = aLoadState.PostDataStream();
+  mHeadersStream = aLoadState.HeadersStream();
+  mSrcdocData = aLoadState.SrcdocData();
+  mChannelInitialized = aLoadState.ChannelInitialized();
+  mIsMetaRefresh = aLoadState.IsMetaRefresh();
+  if (aLoadState.loadingSessionHistoryInfo().isSome()) {
+    mLoadingSessionHistoryInfo = MakeUnique<LoadingSessionHistoryInfo>(
+        aLoadState.loadingSessionHistoryInfo().ref());
+  }
+  mUnstrippedURI = aLoadState.UnstrippedURI();
+  mRemoteTypeOverride = aLoadState.RemoteTypeOverride();
+
+  // We know this was created remotely, as we just received it over IPC.
+  mWasCreatedRemotely = true;
+
+  // If we're in the parent process, potentially validate against a LoadState
+  // which we sent to the source content process.
+  if (XRE_IsParentProcess()) {
+    mozilla::ipc::IToplevelProtocol* top = aActor->ToplevelProtocol();
+    if (!top ||
+        top->GetProtocolId() != mozilla::ipc::ProtocolId::PContentMsgStart ||
+        top->GetSide() != mozilla::ipc::ParentSide) {
+      aActor->FatalError("nsDocShellLoadState must be received over PContent");
+      return;
+    }
+    ContentParent* cp = static_cast<ContentParent*>(top);
+
+    // If this load was sent down to the content process as a navigation
+    // request, ensure it still matches the one we sent down.
+    if (RefPtr<nsDocShellLoadState> originalState =
+            cp->TakePendingLoadStateForId(mLoadIdentifier)) {
+      if (const char* mismatch = ValidateWithOriginalState(originalState)) {
+        aActor->FatalError(
+            nsPrintfCString(
+                "nsDocShellLoadState %s changed while in content process",
+                mismatch)
+                .get());
+        return;
+      }
+    } else if (mTriggeringRemoteType != cp->GetRemoteType()) {
+      // If we don't have a previous load to compare to, the content process
+      // must be the triggering process.
+      aActor->FatalError(
+          "nsDocShellLoadState with invalid triggering remote type");
+      return;
+    }
+  }
+
+  // We successfully read in the data - return a success value.
+  *aReadSuccess = true;
+}
+
+nsDocShellLoadState::nsDocShellLoadState(const nsDocShellLoadState& aOther)
+    : mReferrerInfo(aOther.mReferrerInfo),
+      mURI(aOther.mURI),
+      mOriginalURI(aOther.mOriginalURI),
+      mResultPrincipalURI(aOther.mResultPrincipalURI),
+      mResultPrincipalURIIsSome(aOther.mResultPrincipalURIIsSome),
+      mTriggeringPrincipal(aOther.mTriggeringPrincipal),
+      mTriggeringSandboxFlags(aOther.mTriggeringSandboxFlags),
+      mTriggeringWindowId(aOther.mTriggeringWindowId),
+      mTriggeringStorageAccess(aOther.mTriggeringStorageAccess),
+      mCsp(aOther.mCsp),
+      mKeepResultPrincipalURIIfSet(aOther.mKeepResultPrincipalURIIfSet),
+      mLoadReplace(aOther.mLoadReplace),
+      mInheritPrincipal(aOther.mInheritPrincipal),
+      mPrincipalIsExplicit(aOther.mPrincipalIsExplicit),
+      mNotifiedBeforeUnloadListeners(aOther.mNotifiedBeforeUnloadListeners),
+      mPrincipalToInherit(aOther.mPrincipalToInherit),
+      mPartitionedPrincipalToInherit(aOther.mPartitionedPrincipalToInherit),
+      mForceAllowDataURI(aOther.mForceAllowDataURI),
+      mIsExemptFromHTTPSFirstMode(aOther.mIsExemptFromHTTPSFirstMode),
+      mOriginalFrameSrc(aOther.mOriginalFrameSrc),
+      mIsFormSubmission(aOther.mIsFormSubmission),
+      mLoadType(aOther.mLoadType),
+      mSHEntry(aOther.mSHEntry),
+      mTarget(aOther.mTarget),
+      mTargetBrowsingContext(aOther.mTargetBrowsingContext),
+      mPostDataStream(aOther.mPostDataStream),
+      mHeadersStream(aOther.mHeadersStream),
+      mSrcdocData(aOther.mSrcdocData),
+      mSourceBrowsingContext(aOther.mSourceBrowsingContext),
+      mBaseURI(aOther.mBaseURI),
+      mLoadFlags(aOther.mLoadFlags),
+      mInternalLoadFlags(aOther.mInternalLoadFlags),
+      mFirstParty(aOther.mFirstParty),
+      mHasValidUserGestureActivation(aOther.mHasValidUserGestureActivation),
+      mAllowFocusMove(aOther.mAllowFocusMove),
+      mTypeHint(aOther.mTypeHint),
+      mFileName(aOther.mFileName),
+      mIsFromProcessingFrameAttributes(aOther.mIsFromProcessingFrameAttributes),
+      mPendingRedirectedChannel(aOther.mPendingRedirectedChannel),
+      mOriginalURIString(aOther.mOriginalURIString),
+      mCancelContentJSEpoch(aOther.mCancelContentJSEpoch),
+      mLoadIdentifier(aOther.mLoadIdentifier),
+      mChannelInitialized(aOther.mChannelInitialized),
+      mIsMetaRefresh(aOther.mIsMetaRefresh),
+      mWasCreatedRemotely(aOther.mWasCreatedRemotely),
+      mUnstrippedURI(aOther.mUnstrippedURI),
+      mRemoteTypeOverride(aOther.mRemoteTypeOverride),
+      mTriggeringRemoteType(aOther.mTriggeringRemoteType),
+      mWasSchemelessInput(aOther.mWasSchemelessInput) {
+  MOZ_DIAGNOSTIC_ASSERT(
+      XRE_IsParentProcess(),
+      "Cloning a nsDocShellLoadState with the same load identifier is only "
+      "allowed in the parent process, as it could break triggering remote type "
+      "tracking in content.");
+  if (aOther.mLoadingSessionHistoryInfo) {
+    mLoadingSessionHistoryInfo = MakeUnique<LoadingSessionHistoryInfo>(
+        *aOther.mLoadingSessionHistoryInfo);
+  }
+}
+
+nsDocShellLoadState::nsDocShellLoadState(nsIURI* aURI, uint64_t aLoadIdentifier)
+    : mURI(aURI),
+      mResultPrincipalURIIsSome(false),
+      mTriggeringSandboxFlags(0),
+      mTriggeringWindowId(0),
+      mTriggeringStorageAccess(false),
+      mKeepResultPrincipalURIIfSet(false),
+      mLoadReplace(false),
+      mInheritPrincipal(false),
+      mPrincipalIsExplicit(false),
+      mNotifiedBeforeUnloadListeners(false),
+      mForceAllowDataURI(false),
+      mIsExemptFromHTTPSFirstMode(false),
+      mOriginalFrameSrc(false),
+      mIsFormSubmission(false),
+      mLoadType(LOAD_NORMAL),
+      mSrcdocData(VoidString()),
+      mLoadFlags(0),
+      mInternalLoadFlags(0),
+      mFirstParty(false),
+      mHasValidUserGestureActivation(false),
+      mAllowFocusMove(false),
+      mTypeHint(VoidCString()),
+      mFileName(VoidString()),
+      mIsFromProcessingFrameAttributes(false),
+      mLoadIdentifier(aLoadIdentifier),
+      mChannelInitialized(false),
+      mIsMetaRefresh(false),
+      mWasCreatedRemotely(false),
+      mTriggeringRemoteType(XRE_IsContentProcess()
+                                ? ContentChild::GetSingleton()->GetRemoteType()
+                                : NOT_REMOTE_TYPE),
+      mWasSchemelessInput(false) {
+  MOZ_ASSERT(aURI, "Cannot create a LoadState with a null URI!");
+}
+
+nsDocShellLoadState::~nsDocShellLoadState() {
+  if (mWasCreatedRemotely && XRE_IsContentProcess()) {
+    ContentChild::GetSingleton()->SendCleanupPendingLoadState(mLoadIdentifier);
+  }
+}
+
+nsresult nsDocShellLoadState::CreateFromPendingChannel(
+    nsIChannel* aPendingChannel, uint64_t aLoadIdentifier,
+    uint64_t aRegistrarId, nsDocShellLoadState** aResult) {
+  // Create the nsDocShellLoadState object with default state pulled from the
+  // passed-in channel.
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = aPendingChannel->GetURI(getter_AddRefs(uri));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  RefPtr<nsDocShellLoadState> loadState =
+      new nsDocShellLoadState(uri, aLoadIdentifier);
+  loadState->mPendingRedirectedChannel = aPendingChannel;
+  loadState->mChannelRegistrarId = aRegistrarId;
+
+  // Pull relevant state from the channel, and store it on the
+  // nsDocShellLoadState.
+  nsCOMPtr<nsIURI> originalUri;
+  rv = aPendingChannel->GetOriginalURI(getter_AddRefs(originalUri));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  loadState->SetOriginalURI(originalUri);
+
+  nsCOMPtr<nsILoadInfo> loadInfo = aPendingChannel->LoadInfo();
+  loadState->SetTriggeringPrincipal(loadInfo->TriggeringPrincipal());
+
+  // Return the newly created loadState.
+  loadState.forget(aResult);
+  return NS_OK;
+}
+
+static uint32_t WebNavigationFlagsToFixupFlags(nsIURI* aURI,
+                                               const nsACString& aURIString,
+                                               uint32_t aNavigationFlags) {
+  if (aURI) {
+    aNavigationFlags &= ~nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+  }
+  uint32_t fixupFlags = nsIURIFixup::FIXUP_FLAG_NONE;
+  if (aNavigationFlags & nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP) {
+    fixupFlags |= nsIURIFixup::FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP;
+  }
+  if (aNavigationFlags & nsIWebNavigation::LOAD_FLAGS_FIXUP_SCHEME_TYPOS) {
+    fixupFlags |= nsIURIFixup::FIXUP_FLAG_FIX_SCHEME_TYPOS;
+  }
+  return fixupFlags;
+};
+
+nsresult nsDocShellLoadState::CreateFromLoadURIOptions(
+    BrowsingContext* aBrowsingContext, const nsAString& aURI,
+    const LoadURIOptions& aLoadURIOptions, nsDocShellLoadState** aResult) {
+  uint32_t loadFlags = aLoadURIOptions.mLoadFlags;
+
+  NS_ASSERTION(
+      (loadFlags & nsDocShell::INTERNAL_LOAD_FLAGS_LOADURI_SETUP_FLAGS) == 0,
+      "Unexpected flags");
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = NS_OK;
+
+  NS_ConvertUTF16toUTF8 uriString(aURI);
+  // Cleanup the empty spaces that might be on each end.
+  uriString.Trim(" ");
+  // Eliminate embedded newlines, which single-line text fields now allow:
+  uriString.StripCRLF();
+  NS_ENSURE_TRUE(!uriString.IsEmpty(), NS_ERROR_FAILURE);
+
+  // Just create a URI and see what happens...
+  rv = NS_NewURI(getter_AddRefs(uri), uriString);
+  bool fixup = true;
+  if (NS_SUCCEEDED(rv) && uri &&
+      (uri->SchemeIs("about") || uri->SchemeIs("chrome"))) {
+    // Avoid third party fixup as a performance optimization.
+    loadFlags &= ~nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+    fixup = false;
+  } else if (!sURIFixup && !XRE_IsContentProcess()) {
+    nsCOMPtr<nsIURIFixup> uriFixup = components::URIFixup::Service();
+    if (uriFixup) {
+      sURIFixup = uriFixup;
+      ClearOnShutdown(&sURIFixup);
+    } else {
+      fixup = false;
+    }
+  }
+
+  nsAutoString searchProvider, keyword;
+  RefPtr<nsIInputStream> fixupStream;
+  if (fixup) {
+    uint32_t fixupFlags =
+        WebNavigationFlagsToFixupFlags(uri, uriString, loadFlags);
+
+    // If we don't allow keyword lookups for this URL string, make sure to
+    // update loadFlags to indicate this as well.
+    if (!(fixupFlags & nsIURIFixup::FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP)) {
+      loadFlags &= ~nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+    }
+    // Ensure URIFixup will use the right search engine in Private Browsing.
+    if (aBrowsingContext->UsePrivateBrowsing()) {
+      fixupFlags |= nsIURIFixup::FIXUP_FLAG_PRIVATE_CONTEXT;
+    }
+
+    if (!XRE_IsContentProcess()) {
+      nsCOMPtr<nsIURIFixupInfo> fixupInfo;
+      sURIFixup->GetFixupURIInfo(uriString, fixupFlags,
+                                 getter_AddRefs(fixupInfo));
+      if (fixupInfo) {
+        // We could fix the uri, clear NS_ERROR_MALFORMED_URI.
+        rv = NS_OK;
+        fixupInfo->GetPreferredURI(getter_AddRefs(uri));
+        fixupInfo->SetConsumer(aBrowsingContext);
+        fixupInfo->GetKeywordProviderName(searchProvider);
+        fixupInfo->GetKeywordAsSent(keyword);
+        // GetFixupURIInfo only returns a post data stream if it succeeded
+        // and changed the URI, in which case we should override the
+        // passed-in post data by passing this as an override arg to
+        // our internal method.
+        fixupInfo->GetPostData(getter_AddRefs(fixupStream));
+
+        if (fixupInfo &&
+            loadFlags & nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP) {
+          nsCOMPtr<nsIObserverService> serv = services::GetObserverService();
+          if (serv) {
+            serv->NotifyObservers(fixupInfo, "keyword-uri-fixup",
+                                  PromiseFlatString(aURI).get());
+          }
+        }
+        nsDocShell::MaybeNotifyKeywordSearchLoading(searchProvider, keyword);
+      }
+    }
+  }
+
+  if (rv == NS_ERROR_MALFORMED_URI) {
+    MOZ_ASSERT(!uri);
+    return rv;
+  }
+
+  if (NS_FAILED(rv) || !uri) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<nsDocShellLoadState> loadState;
+  rv = CreateFromLoadURIOptions(
+      aBrowsingContext, uri, aLoadURIOptions, loadFlags,
+      fixupStream ? fixupStream : aLoadURIOptions.mPostData,
+      getter_AddRefs(loadState));
+  NS_ENSURE_SUCCESS(rv, rv);
+  loadState->SetOriginalURIString(uriString);
+  loadState.forget(aResult);
+  return NS_OK;
+}
+
+nsresult nsDocShellLoadState::CreateFromLoadURIOptions(
+    BrowsingContext* aBrowsingContext, nsIURI* aURI,
+    const LoadURIOptions& aLoadURIOptions, nsDocShellLoadState** aResult) {
+  return CreateFromLoadURIOptions(aBrowsingContext, aURI, aLoadURIOptions,
+                                  aLoadURIOptions.mLoadFlags,
+                                  aLoadURIOptions.mPostData, aResult);
+}
+
+nsresult nsDocShellLoadState::CreateFromLoadURIOptions(
+    BrowsingContext* aBrowsingContext, nsIURI* aURI,
+    const LoadURIOptions& aLoadURIOptions, uint32_t aLoadFlagsOverride,
+    nsIInputStream* aPostDataOverride, nsDocShellLoadState** aResult) {
+  nsresult rv = NS_OK;
+  uint32_t loadFlags = aLoadFlagsOverride;
+  RefPtr<nsIInputStream> postData = aPostDataOverride;
+  uint64_t available;
+  if (postData) {
+    rv = postData->Available(&available);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (available == 0) {
+      return NS_ERROR_INVALID_ARG;
+    }
+  }
+
+  if (aLoadURIOptions.mHeaders) {
+    rv = aLoadURIOptions.mHeaders->Available(&available);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (available == 0) {
+      return NS_ERROR_INVALID_ARG;
+    }
+  }
+
+  bool forceAllowDataURI =
+      loadFlags & nsIWebNavigation::LOAD_FLAGS_FORCE_ALLOW_DATA_URI;
+
+  // Don't pass certain flags that aren't needed and end up confusing
+  // ConvertLoadTypeToDocShellInfoLoadType.  We do need to ensure that they are
+  // passed to LoadURI though, since it uses them.
+  uint32_t extraFlags = (loadFlags & EXTRA_LOAD_FLAGS);
+  loadFlags &= ~EXTRA_LOAD_FLAGS;
+
+  RefPtr<nsDocShellLoadState> loadState = new nsDocShellLoadState(aURI);
+  loadState->SetReferrerInfo(aLoadURIOptions.mReferrerInfo);
+
+  loadState->SetLoadType(MAKE_LOAD_TYPE(LOAD_NORMAL, loadFlags));
+
+  loadState->SetLoadFlags(extraFlags);
+  loadState->SetFirstParty(true);
+  loadState->SetHasValidUserGestureActivation(
+      aLoadURIOptions.mHasValidUserGestureActivation);
+  loadState->SetTriggeringSandboxFlags(aLoadURIOptions.mTriggeringSandboxFlags);
+  loadState->SetTriggeringWindowId(aLoadURIOptions.mTriggeringWindowId);
+  loadState->SetTriggeringStorageAccess(
+      aLoadURIOptions.mTriggeringStorageAccess);
+  loadState->SetPostDataStream(postData);
+  loadState->SetHeadersStream(aLoadURIOptions.mHeaders);
+  loadState->SetBaseURI(aLoadURIOptions.mBaseURI);
+  loadState->SetTriggeringPrincipal(aLoadURIOptions.mTriggeringPrincipal);
+  loadState->SetCsp(aLoadURIOptions.mCsp);
+  loadState->SetForceAllowDataURI(forceAllowDataURI);
+  if (aLoadURIOptions.mCancelContentJSEpoch) {
+    loadState->SetCancelContentJSEpoch(aLoadURIOptions.mCancelContentJSEpoch);
+  }
+
+  if (aLoadURIOptions.mTriggeringRemoteType.WasPassed()) {
+    if (XRE_IsParentProcess()) {
+      loadState->SetTriggeringRemoteType(
+          aLoadURIOptions.mTriggeringRemoteType.Value());
+    } else if (ContentChild::GetSingleton()->GetRemoteType() !=
+               aLoadURIOptions.mTriggeringRemoteType.Value()) {
+      NS_WARNING("Invalid TriggeringRemoteType from LoadURIOptions in content");
+      return NS_ERROR_INVALID_ARG;
+    }
+  }
+
+  if (aLoadURIOptions.mRemoteTypeOverride.WasPassed()) {
+    loadState->SetRemoteTypeOverride(
+        aLoadURIOptions.mRemoteTypeOverride.Value());
+  }
+
+  loadState->SetWasSchemelessInput(aLoadURIOptions.mWasSchemelessInput);
+
+  loadState.forget(aResult);
+  return NS_OK;
+}
+
+nsIReferrerInfo* nsDocShellLoadState::GetReferrerInfo() const {
+  return mReferrerInfo;
+}
+
+void nsDocShellLoadState::SetReferrerInfo(nsIReferrerInfo* aReferrerInfo) {
+  mReferrerInfo = aReferrerInfo;
+}
+
+nsIURI* nsDocShellLoadState::URI() const { return mURI; }
+
+void nsDocShellLoadState::SetURI(nsIURI* aURI) { mURI = aURI; }
+
+nsIURI* nsDocShellLoadState::OriginalURI() const { return mOriginalURI; }
+
+void nsDocShellLoadState::SetOriginalURI(nsIURI* aOriginalURI) {
+  mOriginalURI = aOriginalURI;
+}
+
+nsIURI* nsDocShellLoadState::ResultPrincipalURI() const {
+  return mResultPrincipalURI;
+}
+
+void nsDocShellLoadState::SetResultPrincipalURI(nsIURI* aResultPrincipalURI) {
+  mResultPrincipalURI = aResultPrincipalURI;
+}
+
+bool nsDocShellLoadState::ResultPrincipalURIIsSome() const {
+  return mResultPrincipalURIIsSome;
+}
+
+void nsDocShellLoadState::SetResultPrincipalURIIsSome(bool aIsSome) {
+  mResultPrincipalURIIsSome = aIsSome;
+}
+
+bool nsDocShellLoadState::KeepResultPrincipalURIIfSet() const {
+  return mKeepResultPrincipalURIIfSet;
+}
+
+void nsDocShellLoadState::SetKeepResultPrincipalURIIfSet(bool aKeep) {
+  mKeepResultPrincipalURIIfSet = aKeep;
+}
+
+bool nsDocShellLoadState::LoadReplace() const { return mLoadReplace; }
+
+void nsDocShellLoadState::SetLoadReplace(bool aLoadReplace) {
+  mLoadReplace = aLoadReplace;
+}
+
+nsIPrincipal* nsDocShellLoadState::TriggeringPrincipal() const {
+  return mTriggeringPrincipal;
+}
+
+void nsDocShellLoadState::SetTriggeringPrincipal(
+    nsIPrincipal* aTriggeringPrincipal) {
+  mTriggeringPrincipal = aTriggeringPrincipal;
+}
+
+nsIPrincipal* nsDocShellLoadState::PrincipalToInherit() const {
+  return mPrincipalToInherit;
+}
+
+void nsDocShellLoadState::SetPrincipalToInherit(
+    nsIPrincipal* aPrincipalToInherit) {
+  mPrincipalToInherit = aPrincipalToInherit;
+}
+
+nsIPrincipal* nsDocShellLoadState::PartitionedPrincipalToInherit() const {
+  return mPartitionedPrincipalToInherit;
+}
+
+void nsDocShellLoadState::SetPartitionedPrincipalToInherit(
+    nsIPrincipal* aPartitionedPrincipalToInherit) {
+  mPartitionedPrincipalToInherit = aPartitionedPrincipalToInherit;
+}
+
+void nsDocShellLoadState::SetCsp(nsIContentSecurityPolicy* aCsp) {
+  mCsp = aCsp;
+}
+
+nsIContentSecurityPolicy* nsDocShellLoadState::Csp() const { return mCsp; }
+
+void nsDocShellLoadState::SetTriggeringSandboxFlags(uint32_t flags) {
+  mTriggeringSandboxFlags = flags;
+}
+
+uint32_t nsDocShellLoadState::TriggeringSandboxFlags() const {
+  return mTriggeringSandboxFlags;
+}
+
+void nsDocShellLoadState::SetTriggeringWindowId(uint64_t aTriggeringWindowId) {
+  mTriggeringWindowId = aTriggeringWindowId;
+}
+
+uint64_t nsDocShellLoadState::TriggeringWindowId() const {
+  return mTriggeringWindowId;
+}
+
+void nsDocShellLoadState::SetTriggeringStorageAccess(
+    bool aTriggeringStorageAccess) {
+  mTriggeringStorageAccess = aTriggeringStorageAccess;
+}
+
+bool nsDocShellLoadState::TriggeringStorageAccess() const {
+  return mTriggeringStorageAccess;
+}
+
+bool nsDocShellLoadState::InheritPrincipal() const { return mInheritPrincipal; }
+
+void nsDocShellLoadState::SetInheritPrincipal(bool aInheritPrincipal) {
+  mInheritPrincipal = aInheritPrincipal;
+}
+
+bool nsDocShellLoadState::PrincipalIsExplicit() const {
+  return mPrincipalIsExplicit;
+}
+
+void nsDocShellLoadState::SetPrincipalIsExplicit(bool aPrincipalIsExplicit) {
+  mPrincipalIsExplicit = aPrincipalIsExplicit;
+}
+
+bool nsDocShellLoadState::NotifiedBeforeUnloadListeners() const {
+  return mNotifiedBeforeUnloadListeners;
+}
+
+void nsDocShellLoadState::SetNotifiedBeforeUnloadListeners(
+    bool aNotifiedBeforeUnloadListeners) {
+  mNotifiedBeforeUnloadListeners = aNotifiedBeforeUnloadListeners;
+}
+
+bool nsDocShellLoadState::ForceAllowDataURI() const {
+  return mForceAllowDataURI;
+}
+
+void nsDocShellLoadState::SetForceAllowDataURI(bool aForceAllowDataURI) {
+  mForceAllowDataURI = aForceAllowDataURI;
+}
+
+bool nsDocShellLoadState::IsExemptFromHTTPSFirstMode() const {
+  return mIsExemptFromHTTPSFirstMode;
+}
+
+void nsDocShellLoadState::SetIsExemptFromHTTPSFirstMode(
+    bool aIsExemptFromHTTPSFirstMode) {
+  mIsExemptFromHTTPSFirstMode = aIsExemptFromHTTPSFirstMode;
+}
+
+bool nsDocShellLoadState::OriginalFrameSrc() const { return mOriginalFrameSrc; }
+
+void nsDocShellLoadState::SetOriginalFrameSrc(bool aOriginalFrameSrc) {
+  mOriginalFrameSrc = aOriginalFrameSrc;
+}
+
+bool nsDocShellLoadState::IsFormSubmission() const { return mIsFormSubmission; }
+
+void nsDocShellLoadState::SetIsFormSubmission(bool aIsFormSubmission) {
+  mIsFormSubmission = aIsFormSubmission;
+}
+
+uint32_t nsDocShellLoadState::LoadType() const { return mLoadType; }
+
+void nsDocShellLoadState::SetLoadType(uint32_t aLoadType) {
+  mLoadType = aLoadType;
+}
+
+nsISHEntry* nsDocShellLoadState::SHEntry() const { return mSHEntry; }
+
+void nsDocShellLoadState::SetSHEntry(nsISHEntry* aSHEntry) {
+  mSHEntry = aSHEntry;
+  nsCOMPtr<SessionHistoryEntry> she = do_QueryInterface(aSHEntry);
+  if (she) {
+    mLoadingSessionHistoryInfo = MakeUnique<LoadingSessionHistoryInfo>(she);
+  } else {
+    mLoadingSessionHistoryInfo = nullptr;
+  }
+}
+
+void nsDocShellLoadState::SetLoadingSessionHistoryInfo(
+    const mozilla::dom::LoadingSessionHistoryInfo& aLoadingInfo) {
+  SetLoadingSessionHistoryInfo(
+      MakeUnique<mozilla::dom::LoadingSessionHistoryInfo>(aLoadingInfo));
+}
+
+void nsDocShellLoadState::SetLoadingSessionHistoryInfo(
+    mozilla::UniquePtr<mozilla::dom::LoadingSessionHistoryInfo> aLoadingInfo) {
+  mLoadingSessionHistoryInfo = std::move(aLoadingInfo);
+}
+
+const mozilla::dom::LoadingSessionHistoryInfo*
+nsDocShellLoadState::GetLoadingSessionHistoryInfo() const {
+  return mLoadingSessionHistoryInfo.get();
+}
+
+void nsDocShellLoadState::SetLoadIsFromSessionHistory(
+    int32_t aOffset, bool aLoadingCurrentEntry) {
+  if (mLoadingSessionHistoryInfo) {
+    mLoadingSessionHistoryInfo->mLoadIsFromSessionHistory = true;
+    mLoadingSessionHistoryInfo->mOffset = aOffset;
+    mLoadingSessionHistoryInfo->mLoadingCurrentEntry = aLoadingCurrentEntry;
+  }
+}
+
+void nsDocShellLoadState::ClearLoadIsFromSessionHistory() {
+  if (mLoadingSessionHistoryInfo) {
+    mLoadingSessionHistoryInfo->mLoadIsFromSessionHistory = false;
+  }
+  mSHEntry = nullptr;
+}
+
+bool nsDocShellLoadState::LoadIsFromSessionHistory() const {
+  return mLoadingSessionHistoryInfo
+             ? mLoadingSessionHistoryInfo->mLoadIsFromSessionHistory
+             : !!mSHEntry;
+}
+
+void nsDocShellLoadState::MaybeStripTrackerQueryStrings(
+    BrowsingContext* aContext) {
+  MOZ_ASSERT(aContext);
+
+  // Return early if the triggering principal doesn't exist. This could happen
+  // when loading a URL by using a browsing context in the Browser Toolbox.
+  if (!TriggeringPrincipal()) {
+    return;
+  }
+
+  // We don't need to strip for sub frames because the query string has been
+  // stripped in the top-level content. Also, we don't apply stripping if it
+  // is triggered by addons.
+  //
+  // Note that we don't need to do the stripping if the channel has been
+  // initialized. This means that this has been loaded speculatively in the
+  // parent process before and the stripping was happening by then.
+  if (GetChannelInitialized() || !aContext->IsTopContent() ||
+      BasePrincipal::Cast(TriggeringPrincipal())->AddonPolicy()) {
+    return;
+  }
+
+  // We don't strip the URI if it's the same-site navigation. Note that we will
+  // consider the system principal triggered load as third-party in case the
+  // user copies and pastes a URL which has tracking query parameters or an
+  // loading from external applications, such as clicking a link in an email
+  // client.
+  bool isThirdPartyURI = false;
+  if (!TriggeringPrincipal()->IsSystemPrincipal() &&
+      (NS_FAILED(
+           TriggeringPrincipal()->IsThirdPartyURI(URI(), &isThirdPartyURI)) ||
+       !isThirdPartyURI)) {
+    return;
+  }
+
+  Telemetry::AccumulateCategorical(
+      Telemetry::LABELS_QUERY_STRIPPING_COUNT::Navigation);
+
+  nsCOMPtr<nsIURI> strippedURI;
+
+  nsresult rv;
+  nsCOMPtr<nsIURLQueryStringStripper> queryStripper =
+      components::URLQueryStringStripper::Service(&rv);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  uint32_t numStripped;
+
+  queryStripper->Strip(URI(), aContext->UsePrivateBrowsing(),
+                       getter_AddRefs(strippedURI), &numStripped);
+  if (numStripped) {
+    if (!mUnstrippedURI) {
+      mUnstrippedURI = URI();
+    }
+    SetURI(strippedURI);
+
+    Telemetry::AccumulateCategorical(
+        Telemetry::LABELS_QUERY_STRIPPING_COUNT::StripForNavigation);
+    Telemetry::Accumulate(Telemetry::QUERY_STRIPPING_PARAM_COUNT, numStripped);
+  }
+
+#ifdef DEBUG
+  // Make sure that unstripped URI is the same as URI() but only the query
+  // string could be different.
+  if (mUnstrippedURI) {
+    nsCOMPtr<nsIURI> uri;
+    Unused << queryStripper->Strip(mUnstrippedURI,
+                                   aContext->UsePrivateBrowsing(),
+                                   getter_AddRefs(uri), &numStripped);
+    bool equals = false;
+    Unused << URI()->Equals(uri, &equals);
+    MOZ_ASSERT(equals);
+  }
+#endif
+}
+
+const nsString& nsDocShellLoadState::Target() const { return mTarget; }
+
+void nsDocShellLoadState::SetTarget(const nsAString& aTarget) {
+  mTarget = aTarget;
+}
+
+nsIInputStream* nsDocShellLoadState::PostDataStream() const {
+  return mPostDataStream;
+}
+
+void nsDocShellLoadState::SetPostDataStream(nsIInputStream* aStream) {
+  mPostDataStream = aStream;
+}
+
+nsIInputStream* nsDocShellLoadState::HeadersStream() const {
+  return mHeadersStream;
+}
+
+void nsDocShellLoadState::SetHeadersStream(nsIInputStream* aHeadersStream) {
+  mHeadersStream = aHeadersStream;
+}
+
+const nsString& nsDocShellLoadState::SrcdocData() const { return mSrcdocData; }
+
+void nsDocShellLoadState::SetSrcdocData(const nsAString& aSrcdocData) {
+  mSrcdocData = aSrcdocData;
+}
+
+void nsDocShellLoadState::SetSourceBrowsingContext(
+    BrowsingContext* aSourceBrowsingContext) {
+  mSourceBrowsingContext = aSourceBrowsingContext;
+}
+
+void nsDocShellLoadState::SetTargetBrowsingContext(
+    BrowsingContext* aTargetBrowsingContext) {
+  mTargetBrowsingContext = aTargetBrowsingContext;
+}
+
+nsIURI* nsDocShellLoadState::BaseURI() const { return mBaseURI; }
+
+void nsDocShellLoadState::SetBaseURI(nsIURI* aBaseURI) { mBaseURI = aBaseURI; }
+
+void nsDocShellLoadState::GetMaybeResultPrincipalURI(
+    mozilla::Maybe<nsCOMPtr<nsIURI>>& aRPURI) const {
+  bool isSome = ResultPrincipalURIIsSome();
+  aRPURI.reset();
+
+  if (!isSome) {
+    return;
+  }
+
+  nsCOMPtr<nsIURI> uri = ResultPrincipalURI();
+  aRPURI.emplace(std::move(uri));
+}
+
+void nsDocShellLoadState::SetMaybeResultPrincipalURI(
+    mozilla::Maybe<nsCOMPtr<nsIURI>> const& aRPURI) {
+  SetResultPrincipalURI(aRPURI.refOr(nullptr));
+  SetResultPrincipalURIIsSome(aRPURI.isSome());
+}
+
+uint32_t nsDocShellLoadState::LoadFlags() const { return mLoadFlags; }
+
+void nsDocShellLoadState::SetLoadFlags(uint32_t aLoadFlags) {
+  mLoadFlags = aLoadFlags;
+}
+
+void nsDocShellLoadState::SetLoadFlag(uint32_t aFlag) { mLoadFlags |= aFlag; }
+
+void nsDocShellLoadState::UnsetLoadFlag(uint32_t aFlag) {
+  mLoadFlags &= ~aFlag;
+}
+
+bool nsDocShellLoadState::HasLoadFlags(uint32_t aFlags) {
+  return (mLoadFlags & aFlags) == aFlags;
+}
+
+uint32_t nsDocShellLoadState::InternalLoadFlags() const {
+  return mInternalLoadFlags;
+}
+
+void nsDocShellLoadState::SetInternalLoadFlags(uint32_t aLoadFlags) {
+  mInternalLoadFlags = aLoadFlags;
+}
+
+void nsDocShellLoadState::SetInternalLoadFlag(uint32_t aFlag) {
+  mInternalLoadFlags |= aFlag;
+}
+
+void nsDocShellLoadState::UnsetInternalLoadFlag(uint32_t aFlag) {
+  mInternalLoadFlags &= ~aFlag;
+}
+
+bool nsDocShellLoadState::HasInternalLoadFlags(uint32_t aFlags) {
+  return (mInternalLoadFlags & aFlags) == aFlags;
+}
+
+bool nsDocShellLoadState::FirstParty() const { return mFirstParty; }
+
+void nsDocShellLoadState::SetFirstParty(bool aFirstParty) {
+  mFirstParty = aFirstParty;
+}
+
+bool nsDocShellLoadState::HasValidUserGestureActivation() const {
+  return mHasValidUserGestureActivation;
+}
+
+void nsDocShellLoadState::SetHasValidUserGestureActivation(
+    bool aHasValidUserGestureActivation) {
+  mHasValidUserGestureActivation = aHasValidUserGestureActivation;
+}
+
+const nsCString& nsDocShellLoadState::TypeHint() const { return mTypeHint; }
+
+void nsDocShellLoadState::SetTypeHint(const nsCString& aTypeHint) {
+  mTypeHint = aTypeHint;
+}
+
+const nsString& nsDocShellLoadState::FileName() const { return mFileName; }
+
+void nsDocShellLoadState::SetFileName(const nsAString& aFileName) {
+  MOZ_DIAGNOSTIC_ASSERT(aFileName.FindChar(char16_t(0)) == kNotFound,
+                        "The filename should never contain null characters");
+  mFileName = aFileName;
+}
+
+const nsCString& nsDocShellLoadState::GetEffectiveTriggeringRemoteType() const {
+  // Consider non-errorpage loads from session history as being triggred by the
+  // parent process, as we'll validate them against the history entry.
+  //
+  // NOTE: Keep this check in-sync with the session-history validation check in
+  // `DocumentLoadListener::Open`!
+  if (LoadIsFromSessionHistory() && LoadType() != LOAD_ERROR_PAGE) {
+    return NOT_REMOTE_TYPE;
+  }
+  return mTriggeringRemoteType;
+}
+
+void nsDocShellLoadState::SetTriggeringRemoteType(
+    const nsACString& aTriggeringRemoteType) {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess(), "only settable in parent");
+  mTriggeringRemoteType = aTriggeringRemoteType;
+}
+
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+void nsDocShellLoadState::AssertProcessCouldTriggerLoadIfSystem() {
+  // Early check to see if we're trying to start a file URI load with a system
+  // principal within a web content process.
+  // If this assertion fails, the load will fail later during
+  // nsContentSecurityManager checks, however this assertion should happen
+  // closer to whichever caller is triggering the system-principal load.
+  if (mozilla::SessionHistoryInParent() &&
+      TriggeringPrincipal()->IsSystemPrincipal() &&
+      mozilla::dom::IsWebRemoteType(GetEffectiveTriggeringRemoteType())) {
+    bool localFile = false;
+    if (NS_SUCCEEDED(NS_URIChainHasFlags(
+            URI(), nsIProtocolHandler::URI_IS_LOCAL_FILE, &localFile)) &&
+        localFile) {
+      NS_WARNING(nsPrintfCString("Unexpected system load of file URI (%s) from "
+                                 "web content process",
+                                 URI()->GetSpecOrDefault().get())
+                     .get());
+      MOZ_CRASH("Unexpected system load of file URI from web content process");
+    }
+  }
+}
+#endif
+
+nsresult nsDocShellLoadState::SetupInheritingPrincipal(
+    BrowsingContext::Type aType,
+    const mozilla::OriginAttributes& aOriginAttributes) {
+  // We need a principalToInherit.
+  //
+  // If principalIsExplicit is not set there are 4 possibilities:
+  // (1) If the system principal or an expanded principal was passed
+  //     in and we're a typeContent docshell, inherit the principal
+  //     from the current document instead.
+  // (2) In all other cases when the principal passed in is not null,
+  //     use that principal.
+  // (3) If the caller has allowed inheriting from the current document,
+  //     or if we're being called from system code (eg chrome JS or pure
+  //     C++) then inheritPrincipal should be true and InternalLoad will get
+  //     a principal from the current document. If none of these things are
+  //     true, then
+  // (4) we don't pass a principal into the channel, and a principal will be
+  //     created later from the channel's internal data.
+  //
+  // If principalIsExplicit *is* set, there are 4 possibilities
+  // (1) If the system principal or an expanded principal was passed in
+  //     and we're a typeContent docshell, return an error.
+  // (2) In all other cases when the principal passed in is not null,
+  //     use that principal.
+  // (3) If the caller has allowed inheriting from the current document,
+  //     then inheritPrincipal should be true and InternalLoad will get
+  //     a principal from the current document. If none of these things are
+  //     true, then
+  // (4) we dont' pass a principal into the channel, and a principal will be
+  //     created later from the channel's internal data.
+  mPrincipalToInherit = mTriggeringPrincipal;
+  if (mPrincipalToInherit && aType != BrowsingContext::Type::Chrome) {
+    if (mPrincipalToInherit->IsSystemPrincipal()) {
+      if (mPrincipalIsExplicit) {
+        return NS_ERROR_DOM_SECURITY_ERR;
+      }
+      mPrincipalToInherit = nullptr;
+      mInheritPrincipal = true;
+    } else if (nsContentUtils::IsExpandedPrincipal(mPrincipalToInherit)) {
+      if (mPrincipalIsExplicit) {
+        return NS_ERROR_DOM_SECURITY_ERR;
+      }
+      // Don't inherit from the current page.  Just do the safe thing
+      // and pretend that we were loaded by a nullprincipal.
+      //
+      // We didn't inherit OriginAttributes here as ExpandedPrincipal doesn't
+      // have origin attributes.
+      mPrincipalToInherit = NullPrincipal::Create(aOriginAttributes);
+      mInheritPrincipal = false;
+    }
+  }
+
+  if (!mPrincipalToInherit && !mInheritPrincipal && !mPrincipalIsExplicit) {
+    // See if there's system or chrome JS code running
+    mInheritPrincipal = nsContentUtils::LegacyIsCallerChromeOrNativeCode();
+  }
+
+  if (mLoadFlags & nsIWebNavigation::LOAD_FLAGS_DISALLOW_INHERIT_PRINCIPAL) {
+    mInheritPrincipal = false;
+    // Create a new null principal URI based on our precursor principal.
+    nsCOMPtr<nsIURI> nullPrincipalURI =
+        NullPrincipal::CreateURI(mPrincipalToInherit);
+    // If mFirstParty is true and the pref 'privacy.firstparty.isolate' is
+    // enabled, we will set firstPartyDomain on the origin attributes.
+    OriginAttributes attrs(aOriginAttributes);
+    if (mFirstParty) {
+      attrs.SetFirstPartyDomain(true, nullPrincipalURI);
+    }
+    mPrincipalToInherit = NullPrincipal::Create(attrs, nullPrincipalURI);
+  }
+
+  return NS_OK;
+}
+
+nsresult nsDocShellLoadState::SetupTriggeringPrincipal(
+    const mozilla::OriginAttributes& aOriginAttributes) {
+  // If the triggeringPrincipal is not set, we first try to create a principal
+  // from the referrer, since the referrer URI reflects the web origin that
+  // triggered the load. If there is no referrer URI, we fall back to using the
+  // SystemPrincipal. It's safe to assume that no provided triggeringPrincipal
+  // and no referrer simulate a load that was triggered by the system. It's
+  // important to note that this block of code needs to appear *after* the block
+  // where we munge the principalToInherit, because otherwise we would never
+  // enter code blocks checking if the principalToInherit is null and we will
+  // end up with a wrong inheritPrincipal flag.
+  if (!mTriggeringPrincipal) {
+    if (mReferrerInfo) {
+      nsCOMPtr<nsIURI> referrer = mReferrerInfo->GetOriginalReferrer();
+      mTriggeringPrincipal =
+          BasePrincipal::CreateContentPrincipal(referrer, aOriginAttributes);
+
+      if (!mTriggeringPrincipal) {
+        return NS_ERROR_FAILURE;
+      }
+    } else {
+      mTriggeringPrincipal = nsContentUtils::GetSystemPrincipal();
+    }
+  }
+  return NS_OK;
+}
+
+void nsDocShellLoadState::CalculateLoadURIFlags() {
+  if (mInheritPrincipal) {
+    MOZ_ASSERT(
+        !mPrincipalToInherit || !mPrincipalToInherit->IsSystemPrincipal(),
+        "Should not inherit SystemPrincipal");
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_INHERIT_PRINCIPAL;
+  }
+
+  if (mReferrerInfo && !mReferrerInfo->GetSendReferrer()) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_DONT_SEND_REFERRER;
+  }
+  if (mLoadFlags & nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP) {
+    mInternalLoadFlags |=
+        nsDocShell::INTERNAL_LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+  }
+
+  if (mLoadFlags & nsIWebNavigation::LOAD_FLAGS_FIRST_LOAD) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_FIRST_LOAD;
+  }
+
+  if (mLoadFlags & nsIWebNavigation::LOAD_FLAGS_BYPASS_CLASSIFIER) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_BYPASS_CLASSIFIER;
+  }
+
+  if (mLoadFlags & nsIWebNavigation::LOAD_FLAGS_FORCE_ALLOW_COOKIES) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_FORCE_ALLOW_COOKIES;
+  }
+
+  if (mLoadFlags & nsIWebNavigation::LOAD_FLAGS_BYPASS_LOAD_URI_DELEGATE) {
+    mInternalLoadFlags |=
+        nsDocShell::INTERNAL_LOAD_FLAGS_BYPASS_LOAD_URI_DELEGATE;
+  }
+
+  if (!mSrcdocData.IsVoid()) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_IS_SRCDOC;
+  }
+
+  if (mForceAllowDataURI) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_FORCE_ALLOW_DATA_URI;
+  }
+
+  if (mOriginalFrameSrc) {
+    mInternalLoadFlags |= nsDocShell::INTERNAL_LOAD_FLAGS_ORIGINAL_FRAME_SRC;
+  }
+}
+
+nsLoadFlags nsDocShellLoadState::CalculateChannelLoadFlags(
+    BrowsingContext* aBrowsingContext, Maybe<bool> aUriModified,
+    Maybe<bool> aIsEmbeddingBlockedError) {
+  MOZ_ASSERT(aBrowsingContext);
+
+  nsLoadFlags loadFlags = aBrowsingContext->GetDefaultLoadFlags();
+
+  if (FirstParty()) {
+    // tag first party URL loads
+    loadFlags |= nsIChannel::LOAD_INITIAL_DOCUMENT_URI;
+  }
+
+  const uint32_t loadType = LoadType();
+
+  // These values aren't available for loads initiated in the Parent process.
+  MOZ_ASSERT_IF(loadType == LOAD_HISTORY, aUriModified.isSome());
+  MOZ_ASSERT_IF(loadType == LOAD_ERROR_PAGE, aIsEmbeddingBlockedError.isSome());
+
+  if (loadType == LOAD_ERROR_PAGE) {
+    // Error pages are LOAD_BACKGROUND, unless it's an
+    // XFO / frame-ancestors error for which we want an error page to load
+    // but additionally want the onload() event to fire.
+    if (!*aIsEmbeddingBlockedError) {
+      loadFlags |= nsIChannel::LOAD_BACKGROUND;
+    }
+  }
+
+  // Mark the channel as being a document URI and allow content sniffing...
+  loadFlags |=
+      nsIChannel::LOAD_DOCUMENT_URI | nsIChannel::LOAD_CALL_CONTENT_SNIFFERS;
+
+  if (nsDocShell::SandboxFlagsImplyCookies(
+          aBrowsingContext->GetSandboxFlags())) {
+    loadFlags |= nsIRequest::LOAD_DOCUMENT_NEEDS_COOKIE;
+  }
+
+  // Load attributes depend on load type...
+  switch (loadType) {
+    case LOAD_HISTORY: {
+      // Only send VALIDATE_NEVER if mLSHE's URI was never changed via
+      // push/replaceState (bug 669671).
+      if (!*aUriModified) {
+        loadFlags |= nsIRequest::VALIDATE_NEVER;
+      }
+      break;
+    }
+
+    case LOAD_RELOAD_CHARSET_CHANGE_BYPASS_PROXY_AND_CACHE:
+    case LOAD_RELOAD_CHARSET_CHANGE_BYPASS_CACHE:
+      loadFlags |=
+          nsIRequest::LOAD_BYPASS_CACHE | nsIRequest::LOAD_FRESH_CONNECTION;
+      [[fallthrough]];
+
+    case LOAD_REFRESH:
+      loadFlags |= nsIRequest::VALIDATE_ALWAYS;
+      break;
+
+    case LOAD_NORMAL_BYPASS_CACHE:
+    case LOAD_NORMAL_BYPASS_PROXY:
+    case LOAD_NORMAL_BYPASS_PROXY_AND_CACHE:
+    case LOAD_RELOAD_BYPASS_CACHE:
+    case LOAD_RELOAD_BYPASS_PROXY:
+    case LOAD_RELOAD_BYPASS_PROXY_AND_CACHE:
+    case LOAD_REPLACE_BYPASS_CACHE:
+      loadFlags |=
+          nsIRequest::LOAD_BYPASS_CACHE | nsIRequest::LOAD_FRESH_CONNECTION;
+      break;
+
+    case LOAD_RELOAD_NORMAL:
+      if (!StaticPrefs::
+              browser_soft_reload_only_force_validate_top_level_document()) {
+        loadFlags |= nsIRequest::VALIDATE_ALWAYS;
+        break;
+      }
+      [[fallthrough]];
+    case LOAD_NORMAL:
+    case LOAD_LINK:
+      // Set cache checking flags
+      switch (StaticPrefs::browser_cache_check_doc_frequency()) {
+        case 0:
+          loadFlags |= nsIRequest::VALIDATE_ONCE_PER_SESSION;
+          break;
+        case 1:
+          loadFlags |= nsIRequest::VALIDATE_ALWAYS;
+          break;
+        case 2:
+          loadFlags |= nsIRequest::VALIDATE_NEVER;
+          break;
+      }
+      break;
+  }
+
+  if (HasInternalLoadFlags(nsDocShell::INTERNAL_LOAD_FLAGS_BYPASS_CLASSIFIER)) {
+    loadFlags |= nsIChannel::LOAD_BYPASS_URL_CLASSIFIER;
+  }
+
+  // If the user pressed shift-reload, then do not allow ServiceWorker
+  // interception to occur. See step 12.1 of the SW HandleFetch algorithm.
+  if (IsForceReloadType(loadType)) {
+    loadFlags |= nsIChannel::LOAD_BYPASS_SERVICE_WORKER;
+  }
+
+  return loadFlags;
+}
+
+const char* nsDocShellLoadState::ValidateWithOriginalState(
+    nsDocShellLoadState* aOriginalState) {
+  MOZ_ASSERT(mLoadIdentifier == aOriginalState->mLoadIdentifier);
+
+  // Check that `aOriginalState` is sufficiently similar to this state that
+  // they're performing the same load.
+  auto uriEq = [](nsIURI* a, nsIURI* b) -> bool {
+    bool eq = false;
+    return a == b || (a && b && NS_SUCCEEDED(a->Equals(b, &eq)) && eq);
+  };
+  if (!uriEq(mURI, aOriginalState->mURI)) {
+    return "URI";
+  }
+  if (!uriEq(mUnstrippedURI, aOriginalState->mUnstrippedURI)) {
+    return "UnstrippedURI";
+  }
+  if (!uriEq(mOriginalURI, aOriginalState->mOriginalURI)) {
+    return "OriginalURI";
+  }
+  if (!uriEq(mBaseURI, aOriginalState->mBaseURI)) {
+    return "BaseURI";
+  }
+
+  if (!mTriggeringPrincipal->Equals(aOriginalState->mTriggeringPrincipal)) {
+    return "TriggeringPrincipal";
+  }
+  if (mTriggeringSandboxFlags != aOriginalState->mTriggeringSandboxFlags) {
+    return "TriggeringSandboxFlags";
+  }
+  if (mTriggeringRemoteType != aOriginalState->mTriggeringRemoteType) {
+    return "TriggeringRemoteType";
+  }
+
+  if (mOriginalURIString != aOriginalState->mOriginalURIString) {
+    return "OriginalURIString";
+  }
+
+  if (mRemoteTypeOverride != aOriginalState->mRemoteTypeOverride) {
+    return "RemoteTypeOverride";
+  }
+
+  if (mSourceBrowsingContext.ContextId() !=
+      aOriginalState->mSourceBrowsingContext.ContextId()) {
+    return "SourceBrowsingContext";
+  }
+
+  // FIXME: Consider calculating less information in the target process so that
+  // we can validate more properties more easily.
+  // FIXME: Identify what other flags will not change when sent through a
+  // content process.
+
+  return nullptr;
+}
+
+DocShellLoadStateInit nsDocShellLoadState::Serialize(
+    mozilla::ipc::IProtocol* aActor) {
+  MOZ_ASSERT(aActor);
+  DocShellLoadStateInit loadState;
+  loadState.ResultPrincipalURI() = mResultPrincipalURI;
+  loadState.ResultPrincipalURIIsSome() = mResultPrincipalURIIsSome;
+  loadState.KeepResultPrincipalURIIfSet() = mKeepResultPrincipalURIIfSet;
+  loadState.LoadReplace() = mLoadReplace;
+  loadState.InheritPrincipal() = mInheritPrincipal;
+  loadState.PrincipalIsExplicit() = mPrincipalIsExplicit;
+  loadState.ForceAllowDataURI() = mForceAllowDataURI;
+  loadState.IsExemptFromHTTPSFirstMode() = mIsExemptFromHTTPSFirstMode;
+  loadState.OriginalFrameSrc() = mOriginalFrameSrc;
+  loadState.IsFormSubmission() = mIsFormSubmission;
+  loadState.LoadType() = mLoadType;
+  loadState.Target() = mTarget;
+  loadState.TargetBrowsingContext() = mTargetBrowsingContext;
+  loadState.LoadFlags() = mLoadFlags;
+  loadState.InternalLoadFlags() = mInternalLoadFlags;
+  loadState.FirstParty() = mFirstParty;
+  loadState.HasValidUserGestureActivation() = mHasValidUserGestureActivation;
+  loadState.AllowFocusMove() = mAllowFocusMove;
+  loadState.TypeHint() = mTypeHint;
+  loadState.FileName() = mFileName;
+  loadState.IsFromProcessingFrameAttributes() =
+      mIsFromProcessingFrameAttributes;
+  loadState.URI() = mURI;
+  loadState.OriginalURI() = mOriginalURI;
+  loadState.SourceBrowsingContext() = mSourceBrowsingContext;
+  loadState.BaseURI() = mBaseURI;
+  loadState.TriggeringPrincipal() = mTriggeringPrincipal;
+  loadState.PrincipalToInherit() = mPrincipalToInherit;
+  loadState.PartitionedPrincipalToInherit() = mPartitionedPrincipalToInherit;
+  loadState.TriggeringSandboxFlags() = mTriggeringSandboxFlags;
+  loadState.TriggeringWindowId() = mTriggeringWindowId;
+  loadState.TriggeringStorageAccess() = mTriggeringStorageAccess;
+  loadState.TriggeringRemoteType() = mTriggeringRemoteType;
+  loadState.WasSchemelessInput() = mWasSchemelessInput;
+  loadState.Csp() = mCsp;
+  loadState.OriginalURIString() = mOriginalURIString;
+  loadState.CancelContentJSEpoch() = mCancelContentJSEpoch;
+  loadState.ReferrerInfo() = mReferrerInfo;
+  loadState.PostDataStream() = mPostDataStream;
+  loadState.HeadersStream() = mHeadersStream;
+  loadState.SrcdocData() = mSrcdocData;
+  loadState.ResultPrincipalURI() = mResultPrincipalURI;
+  loadState.LoadIdentifier() = mLoadIdentifier;
+  loadState.ChannelInitialized() = mChannelInitialized;
+  loadState.IsMetaRefresh() = mIsMetaRefresh;
+  if (mLoadingSessionHistoryInfo) {
+    loadState.loadingSessionHistoryInfo().emplace(*mLoadingSessionHistoryInfo);
+  }
+  loadState.UnstrippedURI() = mUnstrippedURI;
+  loadState.RemoteTypeOverride() = mRemoteTypeOverride;
+
+  if (XRE_IsParentProcess()) {
+    mozilla::ipc::IToplevelProtocol* top = aActor->ToplevelProtocol();
+    MOZ_RELEASE_ASSERT(top &&
+                           top->GetProtocolId() ==
+                               mozilla::ipc::ProtocolId::PContentMsgStart &&
+                           top->GetSide() == mozilla::ipc::ParentSide,
+                       "nsDocShellLoadState must be sent over PContent");
+    ContentParent* cp = static_cast<ContentParent*>(top);
+    cp->StorePendingLoadState(this);
+  }
+
+  return loadState;
+}
+
+nsIURI* nsDocShellLoadState::GetUnstrippedURI() const { return mUnstrippedURI; }
+
+void nsDocShellLoadState::SetUnstrippedURI(nsIURI* aUnstrippedURI) {
+  mUnstrippedURI = aUnstrippedURI;
+}
diff --git a/docshell/base/nsDocShellLoadState.h b/docshell/base/nsDocShellLoadState.h
new file mode 100644
index 0000000000..a34ca1b54b
--- /dev/null
+++ b/docshell/base/nsDocShellLoadState.h
@@ -0,0 +1,609 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDocShellLoadState_h__
+#define nsDocShellLoadState_h__
+
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/SessionHistoryEntry.h"
+
+// Helper Classes
+#include "mozilla/Maybe.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsDocShellLoadTypes.h"
+#include "nsTArrayForwardDeclare.h"
+
+class nsIContentSecurityPolicy;
+class nsIInputStream;
+class nsISHEntry;
+class nsIURI;
+class nsIDocShell;
+class nsIChannel;
+class nsIReferrerInfo;
+namespace mozilla {
+class OriginAttributes;
+template <typename, class>
+class UniquePtr;
+namespace dom {
+class DocShellLoadStateInit;
+}  // namespace dom
+}  // namespace mozilla
+
+/**
+ * nsDocShellLoadState contains setup information used in a nsIDocShell::loadURI
+ * call.
+ */
+class nsDocShellLoadState final {
+  using BrowsingContext = mozilla::dom::BrowsingContext;
+  template <typename T>
+  using MaybeDiscarded = mozilla::dom::MaybeDiscarded<T>;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(nsDocShellLoadState);
+
+  explicit nsDocShellLoadState(nsIURI* aURI);
+  explicit nsDocShellLoadState(
+      const mozilla::dom::DocShellLoadStateInit& aLoadState,
+      mozilla::ipc::IProtocol* aActor, bool* aReadSuccess);
+  explicit nsDocShellLoadState(const nsDocShellLoadState& aOther);
+  nsDocShellLoadState(nsIURI* aURI, uint64_t aLoadIdentifier);
+
+  static nsresult CreateFromPendingChannel(nsIChannel* aPendingChannel,
+                                           uint64_t aLoadIdentifier,
+                                           uint64_t aRegistarId,
+                                           nsDocShellLoadState** aResult);
+
+  static nsresult CreateFromLoadURIOptions(
+      BrowsingContext* aBrowsingContext, const nsAString& aURI,
+      const mozilla::dom::LoadURIOptions& aLoadURIOptions,
+      nsDocShellLoadState** aResult);
+  static nsresult CreateFromLoadURIOptions(
+      BrowsingContext* aBrowsingContext, nsIURI* aURI,
+      const mozilla::dom::LoadURIOptions& aLoadURIOptions,
+      nsDocShellLoadState** aResult);
+
+  // Getters and Setters
+
+  nsIReferrerInfo* GetReferrerInfo() const;
+
+  void SetReferrerInfo(nsIReferrerInfo* aReferrerInfo);
+
+  nsIURI* URI() const;
+
+  void SetURI(nsIURI* aURI);
+
+  nsIURI* OriginalURI() const;
+
+  void SetOriginalURI(nsIURI* aOriginalURI);
+
+  nsIURI* ResultPrincipalURI() const;
+
+  void SetResultPrincipalURI(nsIURI* aResultPrincipalURI);
+
+  bool ResultPrincipalURIIsSome() const;
+
+  void SetResultPrincipalURIIsSome(bool aIsSome);
+
+  bool KeepResultPrincipalURIIfSet() const;
+
+  void SetKeepResultPrincipalURIIfSet(bool aKeep);
+
+  nsIPrincipal* PrincipalToInherit() const;
+
+  void SetPrincipalToInherit(nsIPrincipal* aPrincipalToInherit);
+
+  nsIPrincipal* PartitionedPrincipalToInherit() const;
+
+  void SetPartitionedPrincipalToInherit(
+      nsIPrincipal* aPartitionedPrincipalToInherit);
+
+  bool LoadReplace() const;
+
+  void SetLoadReplace(bool aLoadReplace);
+
+  nsIPrincipal* TriggeringPrincipal() const;
+
+  void SetTriggeringPrincipal(nsIPrincipal* aTriggeringPrincipal);
+
+  uint32_t TriggeringSandboxFlags() const;
+
+  void SetTriggeringSandboxFlags(uint32_t aTriggeringSandboxFlags);
+
+  uint64_t TriggeringWindowId() const;
+
+  void SetTriggeringWindowId(uint64_t aTriggeringWindowId);
+
+  bool TriggeringStorageAccess() const;
+
+  void SetTriggeringStorageAccess(bool aTriggeringStorageAccess);
+
+  nsIContentSecurityPolicy* Csp() const;
+
+  void SetCsp(nsIContentSecurityPolicy* aCsp);
+
+  bool InheritPrincipal() const;
+
+  void SetInheritPrincipal(bool aInheritPrincipal);
+
+  bool PrincipalIsExplicit() const;
+
+  void SetPrincipalIsExplicit(bool aPrincipalIsExplicit);
+
+  // If true, "beforeunload" event listeners were notified by the creater of the
+  // LoadState and given the chance to abort the navigation, and should not be
+  // notified again.
+  bool NotifiedBeforeUnloadListeners() const;
+
+  void SetNotifiedBeforeUnloadListeners(bool aNotifiedBeforeUnloadListeners);
+
+  bool ForceAllowDataURI() const;
+
+  void SetForceAllowDataURI(bool aForceAllowDataURI);
+
+  bool IsExemptFromHTTPSFirstMode() const;
+
+  void SetIsExemptFromHTTPSFirstMode(bool aIsExemptFromHTTPSFirstMode);
+
+  bool OriginalFrameSrc() const;
+
+  void SetOriginalFrameSrc(bool aOriginalFrameSrc);
+
+  bool IsFormSubmission() const;
+
+  void SetIsFormSubmission(bool aIsFormSubmission);
+
+  uint32_t LoadType() const;
+
+  void SetLoadType(uint32_t aLoadType);
+
+  nsISHEntry* SHEntry() const;
+
+  void SetSHEntry(nsISHEntry* aSHEntry);
+
+  const mozilla::dom::LoadingSessionHistoryInfo* GetLoadingSessionHistoryInfo()
+      const;
+
+  // Copies aLoadingInfo and stores the copy in this nsDocShellLoadState.
+  void SetLoadingSessionHistoryInfo(
+      const mozilla::dom::LoadingSessionHistoryInfo& aLoadingInfo);
+
+  // Stores aLoadingInfo in this nsDocShellLoadState.
+  void SetLoadingSessionHistoryInfo(
+      mozilla::UniquePtr<mozilla::dom::LoadingSessionHistoryInfo> aLoadingInfo);
+
+  bool LoadIsFromSessionHistory() const;
+
+  const nsString& Target() const;
+
+  void SetTarget(const nsAString& aTarget);
+
+  nsIInputStream* PostDataStream() const;
+
+  void SetPostDataStream(nsIInputStream* aStream);
+
+  nsIInputStream* HeadersStream() const;
+
+  void SetHeadersStream(nsIInputStream* aHeadersStream);
+
+  bool IsSrcdocLoad() const;
+
+  const nsString& SrcdocData() const;
+
+  void SetSrcdocData(const nsAString& aSrcdocData);
+
+  const MaybeDiscarded<BrowsingContext>& SourceBrowsingContext() const {
+    return mSourceBrowsingContext;
+  }
+
+  void SetSourceBrowsingContext(BrowsingContext*);
+
+  void SetAllowFocusMove(bool aAllow) { mAllowFocusMove = aAllow; }
+
+  bool AllowFocusMove() const { return mAllowFocusMove; }
+
+  const MaybeDiscarded<BrowsingContext>& TargetBrowsingContext() const {
+    return mTargetBrowsingContext;
+  }
+
+  void SetTargetBrowsingContext(BrowsingContext* aTargetBrowsingContext);
+
+  nsIURI* BaseURI() const;
+
+  void SetBaseURI(nsIURI* aBaseURI);
+
+  // Helper function allowing convenient work with mozilla::Maybe in C++, hiding
+  // resultPrincipalURI and resultPrincipalURIIsSome attributes from the
+  // consumer.
+  void GetMaybeResultPrincipalURI(
+      mozilla::Maybe<nsCOMPtr<nsIURI>>& aRPURI) const;
+
+  void SetMaybeResultPrincipalURI(
+      mozilla::Maybe<nsCOMPtr<nsIURI>> const& aRPURI);
+
+  uint32_t LoadFlags() const;
+
+  void SetLoadFlags(uint32_t aFlags);
+
+  void SetLoadFlag(uint32_t aFlag);
+
+  void UnsetLoadFlag(uint32_t aFlag);
+
+  bool HasLoadFlags(uint32_t aFlag);
+
+  uint32_t InternalLoadFlags() const;
+
+  void SetInternalLoadFlags(uint32_t aFlags);
+
+  void SetInternalLoadFlag(uint32_t aFlag);
+
+  void UnsetInternalLoadFlag(uint32_t aFlag);
+
+  bool HasInternalLoadFlags(uint32_t aFlag);
+
+  bool FirstParty() const;
+
+  void SetFirstParty(bool aFirstParty);
+
+  bool HasValidUserGestureActivation() const;
+
+  void SetHasValidUserGestureActivation(bool HasValidUserGestureActivation);
+
+  const nsCString& TypeHint() const;
+
+  void SetTypeHint(const nsCString& aTypeHint);
+
+  const nsString& FileName() const;
+
+  void SetFileName(const nsAString& aFileName);
+
+  nsIURI* GetUnstrippedURI() const;
+
+  void SetUnstrippedURI(nsIURI* aUnstrippedURI);
+
+  // Give the type of DocShell we're loading into (chrome/content/etc) and
+  // origin attributes for the URI we're loading, figure out if we should
+  // inherit our principal from the document the load was requested from, or
+  // else if the principal should be set up later in the process (after loads).
+  // See comments in function for more info on principal selection algorithm
+  nsresult SetupInheritingPrincipal(
+      mozilla::dom::BrowsingContext::Type aType,
+      const mozilla::OriginAttributes& aOriginAttributes);
+
+  // If no triggering principal exists at the moment, create one using referrer
+  // information and origin attributes.
+  nsresult SetupTriggeringPrincipal(
+      const mozilla::OriginAttributes& aOriginAttributes);
+
+  void SetIsFromProcessingFrameAttributes() {
+    mIsFromProcessingFrameAttributes = true;
+  }
+  bool GetIsFromProcessingFrameAttributes() const {
+    return mIsFromProcessingFrameAttributes;
+  }
+
+  nsIChannel* GetPendingRedirectedChannel() {
+    return mPendingRedirectedChannel;
+  }
+
+  uint64_t GetPendingRedirectChannelRegistrarId() const {
+    return mChannelRegistrarId;
+  }
+
+  void SetOriginalURIString(const nsCString& aOriginalURI) {
+    mOriginalURIString.emplace(aOriginalURI);
+  }
+  const mozilla::Maybe<nsCString>& GetOriginalURIString() const {
+    return mOriginalURIString;
+  }
+
+  void SetCancelContentJSEpoch(int32_t aCancelEpoch) {
+    mCancelContentJSEpoch.emplace(aCancelEpoch);
+  }
+  const mozilla::Maybe<int32_t>& GetCancelContentJSEpoch() const {
+    return mCancelContentJSEpoch;
+  }
+
+  uint64_t GetLoadIdentifier() const { return mLoadIdentifier; }
+
+  void SetChannelInitialized(bool aInitilized) {
+    mChannelInitialized = aInitilized;
+  }
+
+  bool GetChannelInitialized() const { return mChannelInitialized; }
+
+  void SetIsMetaRefresh(bool aMetaRefresh) { mIsMetaRefresh = aMetaRefresh; }
+
+  bool IsMetaRefresh() const { return mIsMetaRefresh; }
+
+  const mozilla::Maybe<nsCString>& GetRemoteTypeOverride() const {
+    return mRemoteTypeOverride;
+  }
+
+  void SetRemoteTypeOverride(const nsCString& aRemoteTypeOverride) {
+    mRemoteTypeOverride = mozilla::Some(aRemoteTypeOverride);
+  }
+
+  void SetWasSchemelessInput(bool aWasSchemelessInput) {
+    mWasSchemelessInput = aWasSchemelessInput;
+  }
+
+  bool GetWasSchemelessInput() { return mWasSchemelessInput; }
+
+  // Determine the remote type of the process which should be considered
+  // responsible for this load for the purposes of security checks.
+  //
+  // This will generally be the process which created the nsDocShellLoadState
+  // originally, however non-errorpage history loads are always considered to be
+  // triggered by the parent process, as we can validate them against the
+  // history entry.
+  const nsCString& GetEffectiveTriggeringRemoteType() const;
+
+  void SetTriggeringRemoteType(const nsACString& aTriggeringRemoteType);
+
+  // Diagnostic assert if this is a system-principal triggered load, and it is
+  // trivial to determine that the effective triggering remote type would not be
+  // allowed to perform this load.
+  //
+  // This is called early during the load to crash as close to the cause as
+  // possible. See bug 1838686 for details.
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  void AssertProcessCouldTriggerLoadIfSystem();
+#else
+  void AssertProcessCouldTriggerLoadIfSystem() {}
+#endif
+
+  // When loading a document through nsDocShell::LoadURI(), a special set of
+  // flags needs to be set based on other values in nsDocShellLoadState. This
+  // function calculates those flags, before the LoadState is passed to
+  // nsDocShell::InternalLoad.
+  void CalculateLoadURIFlags();
+
+  // Compute the load flags to be used by creating channel.  aUriModified and
+  // aIsEmbeddingBlockedError are expected to be Nothing when called from parent
+  // process.
+  nsLoadFlags CalculateChannelLoadFlags(
+      mozilla::dom::BrowsingContext* aBrowsingContext,
+      mozilla::Maybe<bool> aUriModified,
+      mozilla::Maybe<bool> aIsEmbeddingBlockedError);
+
+  mozilla::dom::DocShellLoadStateInit Serialize(
+      mozilla::ipc::IProtocol* aActor);
+
+  void SetLoadIsFromSessionHistory(int32_t aOffset, bool aLoadingCurrentEntry);
+  void ClearLoadIsFromSessionHistory();
+
+  void MaybeStripTrackerQueryStrings(mozilla::dom::BrowsingContext* aContext);
+
+ protected:
+  // Destructor can't be defaulted or inlined, as header doesn't have all type
+  // includes it needs to do so.
+  ~nsDocShellLoadState();
+
+  // Given the original `nsDocShellLoadState` which was sent to a content
+  // process, validate that they corespond to the same load.
+  // Returns a static (telemetry-safe) string naming what did not match, or
+  // nullptr if it succeeds.
+  const char* ValidateWithOriginalState(nsDocShellLoadState* aOriginalState);
+
+  static nsresult CreateFromLoadURIOptions(
+      BrowsingContext* aBrowsingContext, nsIURI* aURI,
+      const mozilla::dom::LoadURIOptions& aLoadURIOptions,
+      uint32_t aLoadFlagsOverride, nsIInputStream* aPostDataOverride,
+      nsDocShellLoadState** aResult);
+
+  // This is the referrer for the load.
+  nsCOMPtr<nsIReferrerInfo> mReferrerInfo;
+
+  // The URI we are navigating to. Will not be null once set.
+  nsCOMPtr<nsIURI> mURI;
+
+  // The URI to set as the originalURI on the channel that does the load. If
+  // null, aURI will be set as the originalURI.
+  nsCOMPtr<nsIURI> mOriginalURI;
+
+  // The URI to be set to loadInfo.resultPrincipalURI
+  // - When Nothing, there will be no change
+  // - When Some, the principal URI will overwrite even
+  //   with a null value.
+  //
+  // Valid only if mResultPrincipalURIIsSome is true (has the same meaning as
+  // isSome() on mozilla::Maybe.)
+  nsCOMPtr<nsIURI> mResultPrincipalURI;
+  bool mResultPrincipalURIIsSome;
+
+  // The principal of the load, that is, the entity responsible for causing the
+  // load to occur. In most cases the referrer and the triggeringPrincipal's URI
+  // will be identical.
+  //
+  // Please note that this is the principal that is used for security checks. If
+  // the argument aURI is provided by the web, then please do not pass a
+  // SystemPrincipal as the triggeringPrincipal.
+  nsCOMPtr<nsIPrincipal> mTriggeringPrincipal;
+
+  // The SandboxFlags of the load, that are, the SandboxFlags of the entity
+  // responsible for causing the load to occur. Most likely this are the
+  // SandboxFlags of the document that started the load.
+  uint32_t mTriggeringSandboxFlags;
+
+  // The window ID and current "has storage access" value of the entity
+  // triggering the load. This allows the identification of self-initiated
+  // same-origin navigations that should propogate unpartitioned storage access.
+  uint64_t mTriggeringWindowId;
+  bool mTriggeringStorageAccess;
+
+  // The CSP of the load, that is, the CSP of the entity responsible for causing
+  // the load to occur. Most likely this is the CSP of the document that started
+  // the load. In case the entity starting the load did not use a CSP, then mCsp
+  // can be null. Please note that this is also the CSP that will be applied to
+  // the load in case the load encounters a server side redirect.
+  nsCOMPtr<nsIContentSecurityPolicy> mCsp;
+
+  // If a refresh is caused by http-equiv="refresh" we want to set
+  // aResultPrincipalURI, but we do not want to overwrite the channel's
+  // ResultPrincipalURI, if it has already been set on the channel by a protocol
+  // handler.
+  bool mKeepResultPrincipalURIIfSet;
+
+  // If set LOAD_REPLACE flag will be set on the channel. If aOriginalURI is
+  // null, this argument is ignored.
+  bool mLoadReplace;
+
+  // If this attribute is true and no triggeringPrincipal is specified,
+  // copy the principal from the referring document.
+  bool mInheritPrincipal;
+
+  // If this attribute is true only ever use the principal specified
+  // by the triggeringPrincipal and inheritPrincipal attributes.
+  // If there are security reasons for why this is unsafe, such
+  // as trying to use a systemprincipal as the triggeringPrincipal
+  // for a content docshell the load fails.
+  bool mPrincipalIsExplicit;
+
+  bool mNotifiedBeforeUnloadListeners;
+
+  // Principal we're inheriting. If null, this means the principal should be
+  // inherited from the current document. If set to NullPrincipal, the channel
+  // will fill in principal information later in the load. See internal comments
+  // of SetupInheritingPrincipal for more info.
+  //
+  // When passed to InternalLoad, If this argument is null then
+  // principalToInherit is computed differently. See nsDocShell::InternalLoad
+  // for more comments.
+
+  nsCOMPtr<nsIPrincipal> mPrincipalToInherit;
+
+  nsCOMPtr<nsIPrincipal> mPartitionedPrincipalToInherit;
+
+  // If this attribute is true, then a top-level navigation
+  // to a data URI will be allowed.
+  bool mForceAllowDataURI;
+
+  // If this attribute is true, then the top-level navigaion
+  // will be exempt from HTTPS-Only-Mode upgrades.
+  bool mIsExemptFromHTTPSFirstMode;
+
+  // If this attribute is true, this load corresponds to a frame
+  // element loading its original src (or srcdoc) attribute.
+  bool mOriginalFrameSrc;
+
+  // If this attribute is true, then the load was initiated by a
+  // form submission.
+  bool mIsFormSubmission;
+
+  // Contains a load type as specified by the nsDocShellLoadTypes::load*
+  // constants
+  uint32_t mLoadType;
+
+  // Active Session History entry (if loading from SH)
+  nsCOMPtr<nsISHEntry> mSHEntry;
+
+  // Loading session history info for the load
+  mozilla::UniquePtr<mozilla::dom::LoadingSessionHistoryInfo>
+      mLoadingSessionHistoryInfo;
+
+  // Target for load, like _content, _blank etc.
+  nsString mTarget;
+
+  // When set, this is the Target Browsing Context for the navigation
+  // after retargeting.
+  MaybeDiscarded<BrowsingContext> mTargetBrowsingContext;
+
+  // Post data stream (if POSTing)
+  nsCOMPtr<nsIInputStream> mPostDataStream;
+
+  // Additional Headers
+  nsCOMPtr<nsIInputStream> mHeadersStream;
+
+  // When set, the load will be interpreted as a srcdoc load, where contents of
+  // this string will be loaded instead of the URI. Setting srcdocData sets
+  // isSrcdocLoad to true
+  nsString mSrcdocData;
+
+  // When set, this is the Source Browsing Context for the navigation.
+  MaybeDiscarded<BrowsingContext> mSourceBrowsingContext;
+
+  // Used for srcdoc loads to give view-source knowledge of the load's base URI
+  // as this information isn't embedded in the load's URI.
+  nsCOMPtr<nsIURI> mBaseURI;
+
+  // Set of Load Flags, taken from nsDocShellLoadTypes.h and nsIWebNavigation
+  uint32_t mLoadFlags;
+
+  // Set of internal load flags
+  uint32_t mInternalLoadFlags;
+
+  // Is this a First Party Load?
+  bool mFirstParty;
+
+  // Is this load triggered by a user gesture?
+  bool mHasValidUserGestureActivation;
+
+  // Whether this load can steal the focus from the source browsing context.
+  bool mAllowFocusMove;
+
+  // A hint as to the content-type of the resulting data. If no hint, IsVoid()
+  // should return true.
+  nsCString mTypeHint;
+
+  // Non-void when the link should be downloaded as the given filename.
+  // mFileName being non-void but empty means that no filename hint was
+  // specified, but link should still trigger a download. If not a download,
+  // mFileName.IsVoid() should return true.
+  nsString mFileName;
+
+  // This will be true if this load is triggered by attribute changes.
+  // See nsILoadInfo.isFromProcessingFrameAttributes
+  bool mIsFromProcessingFrameAttributes;
+
+  // If set, a pending cross-process redirected channel should be used to
+  // perform the load. The channel will be stored in this value.
+  nsCOMPtr<nsIChannel> mPendingRedirectedChannel;
+
+  // An optional string representation of mURI, before any
+  // fixups were applied, so that we can send it to a search
+  // engine service if needed.
+  mozilla::Maybe<nsCString> mOriginalURIString;
+
+  // An optional value to pass to nsIDocShell::setCancelJSEpoch
+  // when initiating the load.
+  mozilla::Maybe<int32_t> mCancelContentJSEpoch;
+
+  // If mPendingRedirectChannel is set, then this is the identifier
+  // that the parent-process equivalent channel has been registered
+  // with using RedirectChannelRegistrar.
+  uint64_t mChannelRegistrarId;
+
+  // An identifier to make it possible to examine if two loads are
+  // equal, and which browsing context they belong to (see
+  // BrowsingContext::{Get, Set}CurrentLoadIdentifier)
+  const uint64_t mLoadIdentifier;
+
+  // Optional value to indicate that a channel has been
+  // pre-initialized in the parent process.
+  bool mChannelInitialized;
+
+  // True if the load was triggered by a meta refresh.
+  bool mIsMetaRefresh;
+
+  // True if the nsDocShellLoadState was received over IPC.
+  bool mWasCreatedRemotely = false;
+
+  // The original URI before query stripping happened. If it's present, it shows
+  // the query stripping happened. Otherwise, it will be a nullptr.
+  nsCOMPtr<nsIURI> mUnstrippedURI;
+
+  // If set, the remote type which the load should be completed within.
+  mozilla::Maybe<nsCString> mRemoteTypeOverride;
+
+  // Remote type of the process which originally requested the load.
+  nsCString mTriggeringRemoteType;
+
+  // if the to-be-loaded address had it protocol added through a fixup
+  bool mWasSchemelessInput = false;
+};
+
+#endif /* nsDocShellLoadState_h__ */
diff --git a/docshell/base/nsDocShellLoadTypes.h b/docshell/base/nsDocShellLoadTypes.h
new file mode 100644
index 0000000000..1de19e81eb
--- /dev/null
+++ b/docshell/base/nsDocShellLoadTypes.h
@@ -0,0 +1,205 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDocShellLoadTypes_h_
+#define nsDocShellLoadTypes_h_
+
+#ifdef MOZILLA_INTERNAL_API
+
+#  include "nsDOMNavigationTiming.h"
+#  include "nsIDocShell.h"
+#  include "nsIWebNavigation.h"
+
+/**
+ * Load flag for error pages. This uses one of the reserved flag
+ * values from nsIWebNavigation.
+ */
+#  define LOAD_FLAGS_ERROR_PAGE 0x0001U
+
+#  define MAKE_LOAD_TYPE(type, flags) ((type) | ((flags) << 16))
+#  define LOAD_TYPE_HAS_FLAGS(type, flags) ((type) & ((flags) << 16))
+
+/**
+ * These are flags that confuse ConvertLoadTypeToDocShellLoadInfo and should
+ * not be passed to MAKE_LOAD_TYPE.  In particular this includes all flags
+ * above 0xffff (e.g. LOAD_FLAGS_BYPASS_CLASSIFIER), since MAKE_LOAD_TYPE would
+ * just shift them out anyway.
+ */
+#  define EXTRA_LOAD_FLAGS                        \
+    (nsIWebNavigation::LOAD_FLAGS_FROM_EXTERNAL | \
+     nsIWebNavigation::LOAD_FLAGS_FIRST_LOAD |    \
+     nsIWebNavigation::LOAD_FLAGS_ALLOW_POPUPS | 0xffff0000)
+
+/* load types are legal combinations of load commands and flags
+ *
+ * NOTE:
+ *  Remember to update the IsValidLoadType function below if you change this
+ *  enum to ensure bad flag combinations will be rejected.
+ */
+enum LoadType : uint32_t {
+  LOAD_NORMAL = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                               nsIWebNavigation::LOAD_FLAGS_NONE),
+  LOAD_NORMAL_REPLACE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                     nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY),
+  LOAD_HISTORY = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_HISTORY,
+                                nsIWebNavigation::LOAD_FLAGS_NONE),
+  LOAD_NORMAL_BYPASS_CACHE = MAKE_LOAD_TYPE(
+      nsIDocShell::LOAD_CMD_NORMAL, nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE),
+  LOAD_NORMAL_BYPASS_PROXY = MAKE_LOAD_TYPE(
+      nsIDocShell::LOAD_CMD_NORMAL, nsIWebNavigation::LOAD_FLAGS_BYPASS_PROXY),
+  LOAD_NORMAL_BYPASS_PROXY_AND_CACHE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                     nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE |
+                         nsIWebNavigation::LOAD_FLAGS_BYPASS_PROXY),
+  LOAD_RELOAD_NORMAL = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_RELOAD,
+                                      nsIWebNavigation::LOAD_FLAGS_NONE),
+  LOAD_RELOAD_BYPASS_CACHE = MAKE_LOAD_TYPE(
+      nsIDocShell::LOAD_CMD_RELOAD, nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE),
+  LOAD_RELOAD_BYPASS_PROXY = MAKE_LOAD_TYPE(
+      nsIDocShell::LOAD_CMD_RELOAD, nsIWebNavigation::LOAD_FLAGS_BYPASS_PROXY),
+  LOAD_RELOAD_BYPASS_PROXY_AND_CACHE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_RELOAD,
+                     nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE |
+                         nsIWebNavigation::LOAD_FLAGS_BYPASS_PROXY),
+  LOAD_LINK = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                             nsIWebNavigation::LOAD_FLAGS_IS_LINK),
+  LOAD_REFRESH = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                                nsIWebNavigation::LOAD_FLAGS_IS_REFRESH),
+  LOAD_REFRESH_REPLACE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                     nsIWebNavigation::LOAD_FLAGS_IS_REFRESH |
+                         nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY),
+  LOAD_RELOAD_CHARSET_CHANGE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_RELOAD,
+                     nsIWebNavigation::LOAD_FLAGS_CHARSET_CHANGE),
+  LOAD_RELOAD_CHARSET_CHANGE_BYPASS_PROXY_AND_CACHE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_RELOAD,
+                     nsIWebNavigation::LOAD_FLAGS_CHARSET_CHANGE |
+                         nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE |
+                         nsIWebNavigation::LOAD_FLAGS_BYPASS_PROXY),
+  LOAD_RELOAD_CHARSET_CHANGE_BYPASS_CACHE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_RELOAD,
+                     nsIWebNavigation::LOAD_FLAGS_CHARSET_CHANGE |
+                         nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE),
+  LOAD_BYPASS_HISTORY =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                     nsIWebNavigation::LOAD_FLAGS_BYPASS_HISTORY),
+  LOAD_STOP_CONTENT = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                                     nsIWebNavigation::LOAD_FLAGS_STOP_CONTENT),
+  LOAD_STOP_CONTENT_AND_REPLACE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                     nsIWebNavigation::LOAD_FLAGS_STOP_CONTENT |
+                         nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY),
+  LOAD_PUSHSTATE = MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_PUSHSTATE,
+                                  nsIWebNavigation::LOAD_FLAGS_NONE),
+  LOAD_REPLACE_BYPASS_CACHE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL,
+                     nsIWebNavigation::LOAD_FLAGS_REPLACE_HISTORY |
+                         nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE),
+  /**
+   * Load type for an error page. These loads are never triggered by users of
+   * Docshell. Instead, Docshell triggers the load itself when a
+   * consumer-triggered load failed.
+   */
+  LOAD_ERROR_PAGE =
+      MAKE_LOAD_TYPE(nsIDocShell::LOAD_CMD_NORMAL, LOAD_FLAGS_ERROR_PAGE)
+
+  // NOTE: Adding a new value? Remember to update IsValidLoadType!
+};
+
+static inline bool IsForceReloadType(uint32_t aLoadType) {
+  switch (aLoadType) {
+    case LOAD_RELOAD_BYPASS_CACHE:
+    case LOAD_RELOAD_BYPASS_PROXY:
+    case LOAD_RELOAD_BYPASS_PROXY_AND_CACHE:
+      return true;
+  }
+  return false;
+}
+
+static inline bool IsValidLoadType(uint32_t aLoadType) {
+  switch (aLoadType) {
+    case LOAD_NORMAL:
+    case LOAD_NORMAL_REPLACE:
+    case LOAD_NORMAL_BYPASS_CACHE:
+    case LOAD_NORMAL_BYPASS_PROXY:
+    case LOAD_NORMAL_BYPASS_PROXY_AND_CACHE:
+    case LOAD_HISTORY:
+    case LOAD_RELOAD_NORMAL:
+    case LOAD_RELOAD_BYPASS_CACHE:
+    case LOAD_RELOAD_BYPASS_PROXY:
+    case LOAD_RELOAD_BYPASS_PROXY_AND_CACHE:
+    case LOAD_LINK:
+    case LOAD_REFRESH:
+    case LOAD_REFRESH_REPLACE:
+    case LOAD_RELOAD_CHARSET_CHANGE:
+    case LOAD_RELOAD_CHARSET_CHANGE_BYPASS_PROXY_AND_CACHE:
+    case LOAD_RELOAD_CHARSET_CHANGE_BYPASS_CACHE:
+    case LOAD_BYPASS_HISTORY:
+    case LOAD_STOP_CONTENT:
+    case LOAD_STOP_CONTENT_AND_REPLACE:
+    case LOAD_PUSHSTATE:
+    case LOAD_REPLACE_BYPASS_CACHE:
+    case LOAD_ERROR_PAGE:
+      return true;
+  }
+  return false;
+}
+
+inline nsDOMNavigationTiming::Type ConvertLoadTypeToNavigationType(
+    uint32_t aLoadType) {
+  // Not initialized, assume it's normal load.
+  if (aLoadType == 0) {
+    aLoadType = LOAD_NORMAL;
+  }
+
+  auto result = nsDOMNavigationTiming::TYPE_RESERVED;
+  switch (aLoadType) {
+    case LOAD_NORMAL:
+    case LOAD_NORMAL_BYPASS_CACHE:
+    case LOAD_NORMAL_BYPASS_PROXY:
+    case LOAD_NORMAL_BYPASS_PROXY_AND_CACHE:
+    case LOAD_NORMAL_REPLACE:
+    case LOAD_LINK:
+    case LOAD_STOP_CONTENT:
+    // FIXME: It isn't clear that LOAD_REFRESH_REPLACE should have a different
+    // navigation type than LOAD_REFRESH. Those loads historically used the
+    // LOAD_NORMAL_REPLACE type, and therefore wound up with TYPE_NAVIGATE by
+    // default.
+    case LOAD_REFRESH_REPLACE:
+    case LOAD_REPLACE_BYPASS_CACHE:
+      result = nsDOMNavigationTiming::TYPE_NAVIGATE;
+      break;
+    case LOAD_HISTORY:
+      result = nsDOMNavigationTiming::TYPE_BACK_FORWARD;
+      break;
+    case LOAD_RELOAD_NORMAL:
+    case LOAD_RELOAD_CHARSET_CHANGE:
+    case LOAD_RELOAD_CHARSET_CHANGE_BYPASS_PROXY_AND_CACHE:
+    case LOAD_RELOAD_CHARSET_CHANGE_BYPASS_CACHE:
+    case LOAD_RELOAD_BYPASS_CACHE:
+    case LOAD_RELOAD_BYPASS_PROXY:
+    case LOAD_RELOAD_BYPASS_PROXY_AND_CACHE:
+      result = nsDOMNavigationTiming::TYPE_RELOAD;
+      break;
+    case LOAD_STOP_CONTENT_AND_REPLACE:
+    case LOAD_REFRESH:
+    case LOAD_BYPASS_HISTORY:
+    case LOAD_ERROR_PAGE:
+    case LOAD_PUSHSTATE:
+      result = nsDOMNavigationTiming::TYPE_RESERVED;
+      break;
+    default:
+      result = nsDOMNavigationTiming::TYPE_RESERVED;
+      break;
+  }
+
+  return result;
+}
+
+#endif  // MOZILLA_INTERNAL_API
+#endif
diff --git a/docshell/base/nsDocShellTelemetryUtils.cpp b/docshell/base/nsDocShellTelemetryUtils.cpp
new file mode 100644
index 0000000000..bd4ed865bd
--- /dev/null
+++ b/docshell/base/nsDocShellTelemetryUtils.cpp
@@ -0,0 +1,202 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDocShellTelemetryUtils.h"
+
+namespace {
+
+using ErrorLabel = mozilla::Telemetry::LABELS_PAGE_LOAD_ERROR;
+
+struct LoadErrorTelemetryResult {
+  nsresult mValue;
+  ErrorLabel mLabel;
+};
+
+static const LoadErrorTelemetryResult sResult[] = {
+    {
+        NS_ERROR_UNKNOWN_PROTOCOL,
+        ErrorLabel::UNKNOWN_PROTOCOL,
+    },
+    {
+        NS_ERROR_FILE_NOT_FOUND,
+        ErrorLabel::FILE_NOT_FOUND,
+    },
+    {
+        NS_ERROR_FILE_ACCESS_DENIED,
+        ErrorLabel::FILE_ACCESS_DENIED,
+    },
+    {
+        NS_ERROR_UNKNOWN_HOST,
+        ErrorLabel::UNKNOWN_HOST,
+    },
+    {
+        NS_ERROR_CONNECTION_REFUSED,
+        ErrorLabel::CONNECTION_REFUSED,
+    },
+    {
+        NS_ERROR_PROXY_BAD_GATEWAY,
+        ErrorLabel::PROXY_BAD_GATEWAY,
+    },
+    {
+        NS_ERROR_NET_INTERRUPT,
+        ErrorLabel::NET_INTERRUPT,
+    },
+    {
+        NS_ERROR_NET_TIMEOUT,
+        ErrorLabel::NET_TIMEOUT,
+    },
+    {
+        NS_ERROR_PROXY_GATEWAY_TIMEOUT,
+        ErrorLabel::P_GATEWAY_TIMEOUT,
+    },
+    {
+        NS_ERROR_CSP_FRAME_ANCESTOR_VIOLATION,
+        ErrorLabel::CSP_FRAME_ANCEST,
+    },
+    {
+        NS_ERROR_CSP_FORM_ACTION_VIOLATION,
+        ErrorLabel::CSP_FORM_ACTION,
+    },
+    {
+        NS_ERROR_XFO_VIOLATION,
+        ErrorLabel::XFO_VIOLATION,
+    },
+    {
+        NS_ERROR_PHISHING_URI,
+        ErrorLabel::PHISHING_URI,
+    },
+    {
+        NS_ERROR_MALWARE_URI,
+        ErrorLabel::MALWARE_URI,
+    },
+    {
+        NS_ERROR_UNWANTED_URI,
+        ErrorLabel::UNWANTED_URI,
+    },
+    {
+        NS_ERROR_HARMFUL_URI,
+        ErrorLabel::HARMFUL_URI,
+    },
+    {
+        NS_ERROR_CONTENT_CRASHED,
+        ErrorLabel::CONTENT_CRASHED,
+    },
+    {
+        NS_ERROR_FRAME_CRASHED,
+        ErrorLabel::FRAME_CRASHED,
+    },
+    {
+        NS_ERROR_BUILDID_MISMATCH,
+        ErrorLabel::BUILDID_MISMATCH,
+    },
+    {
+        NS_ERROR_NET_RESET,
+        ErrorLabel::NET_RESET,
+    },
+    {
+        NS_ERROR_MALFORMED_URI,
+        ErrorLabel::MALFORMED_URI,
+    },
+    {
+        NS_ERROR_REDIRECT_LOOP,
+        ErrorLabel::REDIRECT_LOOP,
+    },
+    {
+        NS_ERROR_UNKNOWN_SOCKET_TYPE,
+        ErrorLabel::UNKNOWN_SOCKET,
+    },
+    {
+        NS_ERROR_DOCUMENT_NOT_CACHED,
+        ErrorLabel::DOCUMENT_N_CACHED,
+    },
+    {
+        NS_ERROR_OFFLINE,
+        ErrorLabel::OFFLINE,
+    },
+    {
+        NS_ERROR_DOCUMENT_IS_PRINTMODE,
+        ErrorLabel::DOC_PRINTMODE,
+    },
+    {
+        NS_ERROR_PORT_ACCESS_NOT_ALLOWED,
+        ErrorLabel::PORT_ACCESS,
+    },
+    {
+        NS_ERROR_UNKNOWN_PROXY_HOST,
+        ErrorLabel::UNKNOWN_PROXY_HOST,
+    },
+    {
+        NS_ERROR_PROXY_CONNECTION_REFUSED,
+        ErrorLabel::PROXY_CONNECTION,
+    },
+    {
+        NS_ERROR_PROXY_FORBIDDEN,
+        ErrorLabel::PROXY_FORBIDDEN,
+    },
+    {
+        NS_ERROR_PROXY_NOT_IMPLEMENTED,
+        ErrorLabel::P_NOT_IMPLEMENTED,
+    },
+    {
+        NS_ERROR_PROXY_AUTHENTICATION_FAILED,
+        ErrorLabel::PROXY_AUTH,
+    },
+    {
+        NS_ERROR_PROXY_TOO_MANY_REQUESTS,
+        ErrorLabel::PROXY_TOO_MANY,
+    },
+    {
+        NS_ERROR_INVALID_CONTENT_ENCODING,
+        ErrorLabel::CONTENT_ENCODING,
+    },
+    {
+        NS_ERROR_UNSAFE_CONTENT_TYPE,
+        ErrorLabel::UNSAFE_CONTENT,
+    },
+    {
+        NS_ERROR_CORRUPTED_CONTENT,
+        ErrorLabel::CORRUPTED_CONTENT,
+    },
+    {
+        NS_ERROR_INTERCEPTION_FAILED,
+        ErrorLabel::INTERCEPTION_FAIL,
+    },
+    {
+        NS_ERROR_NET_INADEQUATE_SECURITY,
+        ErrorLabel::INADEQUATE_SEC,
+    },
+    {
+        NS_ERROR_BLOCKED_BY_POLICY,
+        ErrorLabel::BLOCKED_BY_POLICY,
+    },
+    {
+        NS_ERROR_NET_HTTP2_SENT_GOAWAY,
+        ErrorLabel::HTTP2_SENT_GOAWAY,
+    },
+    {
+        NS_ERROR_NET_HTTP3_PROTOCOL_ERROR,
+        ErrorLabel::HTTP3_PROTOCOL,
+    },
+    {
+        NS_BINDING_FAILED,
+        ErrorLabel::BINDING_FAILED,
+    },
+};
+}  // anonymous namespace
+
+namespace mozilla {
+namespace dom {
+mozilla::Telemetry::LABELS_PAGE_LOAD_ERROR LoadErrorToTelemetryLabel(
+    nsresult aRv) {
+  MOZ_ASSERT(aRv != NS_OK);
+
+  for (const auto& p : sResult) {
+    if (p.mValue == aRv) {
+      return p.mLabel;
+    }
+  }
+  return ErrorLabel::otherError;
+}
+}  // namespace dom
+}  // namespace mozilla
diff --git a/docshell/base/nsDocShellTelemetryUtils.h b/docshell/base/nsDocShellTelemetryUtils.h
new file mode 100644
index 0000000000..4e0097caec
--- /dev/null
+++ b/docshell/base/nsDocShellTelemetryUtils.h
@@ -0,0 +1,22 @@
+//* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDocShellTelemetryUtils_h__
+#define nsDocShellTelemetryUtils_h__
+
+#include "mozilla/Telemetry.h"
+
+namespace mozilla {
+namespace dom {
+/**
+ * Convert page load errors to telemetry labels
+ * Only select nsresults are converted, otherwise this function
+ * will return "errorOther", view the list of errors at
+ * docshell/base/nsDocShellTelemetryUtils.cpp.
+ */
+Telemetry::LABELS_PAGE_LOAD_ERROR LoadErrorToTelemetryLabel(nsresult aRv);
+}  // namespace dom
+}  // namespace mozilla
+#endif  // nsDocShellTelemetryUtils_h__
diff --git a/docshell/base/nsDocShellTreeOwner.cpp b/docshell/base/nsDocShellTreeOwner.cpp
new file mode 100644
index 0000000000..9f1ab23a6c
--- /dev/null
+++ b/docshell/base/nsDocShellTreeOwner.cpp
@@ -0,0 +1,1337 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Local Includes
+#include "nsDocShellTreeOwner.h"
+#include "nsWebBrowser.h"
+
+// Helper Classes
+#include "nsContentUtils.h"
+#include "nsSize.h"
+#include "mozilla/ReflowInput.h"
+#include "mozilla/ScopeExit.h"
+#include "nsComponentManagerUtils.h"
+#include "nsString.h"
+#include "nsAtom.h"
+#include "nsReadableUtils.h"
+#include "nsUnicharUtils.h"
+#include "mozilla/LookAndFeel.h"
+
+// Interfaces needed to be included
+#include "nsPresContext.h"
+#include "nsITooltipListener.h"
+#include "nsINode.h"
+#include "Link.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/MouseEvent.h"
+#include "mozilla/dom/SVGTitleElement.h"
+#include "nsIFormControl.h"
+#include "nsIWebNavigation.h"
+#include "nsPIDOMWindow.h"
+#include "nsPIWindowRoot.h"
+#include "nsIWindowWatcher.h"
+#include "nsPIWindowWatcher.h"
+#include "nsIPrompt.h"
+#include "nsIRemoteTab.h"
+#include "nsIBrowserChild.h"
+#include "nsRect.h"
+#include "nsIWebBrowserChromeFocus.h"
+#include "nsIContent.h"
+#include "nsServiceManagerUtils.h"
+#include "nsViewManager.h"
+#include "nsView.h"
+#include "nsXULTooltipListener.h"
+#include "nsIConstraintValidation.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/EventListenerManager.h"
+#include "mozilla/Try.h"
+#include "mozilla/dom/DragEvent.h"
+#include "mozilla/dom/Event.h"     // for Event
+#include "mozilla/dom/File.h"      // for input type=file
+#include "mozilla/dom/FileList.h"  // for input type=file
+#include "mozilla/dom/LoadURIOptionsBinding.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/TextEvents.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// A helper routine that navigates the tricky path from a |nsWebBrowser| to
+// a |EventTarget| via the window root and chrome event handler.
+static nsresult GetDOMEventTarget(nsWebBrowser* aInBrowser,
+                                  EventTarget** aTarget) {
+  if (!aInBrowser) {
+    return NS_ERROR_INVALID_POINTER;
+  }
+
+  nsCOMPtr<mozIDOMWindowProxy> domWindow;
+  aInBrowser->GetContentDOMWindow(getter_AddRefs(domWindow));
+  if (!domWindow) {
+    return NS_ERROR_FAILURE;
+  }
+
+  auto* outerWindow = nsPIDOMWindowOuter::From(domWindow);
+  nsPIDOMWindowOuter* rootWindow = outerWindow->GetPrivateRoot();
+  NS_ENSURE_TRUE(rootWindow, NS_ERROR_FAILURE);
+  nsCOMPtr<EventTarget> target = rootWindow->GetChromeEventHandler();
+  NS_ENSURE_TRUE(target, NS_ERROR_FAILURE);
+  target.forget(aTarget);
+
+  return NS_OK;
+}
+
+nsDocShellTreeOwner::nsDocShellTreeOwner()
+    : mWebBrowser(nullptr),
+      mTreeOwner(nullptr),
+      mPrimaryContentShell(nullptr),
+      mWebBrowserChrome(nullptr),
+      mOwnerWin(nullptr),
+      mOwnerRequestor(nullptr) {}
+
+nsDocShellTreeOwner::~nsDocShellTreeOwner() { RemoveChromeListeners(); }
+
+NS_IMPL_ADDREF(nsDocShellTreeOwner)
+NS_IMPL_RELEASE(nsDocShellTreeOwner)
+
+NS_INTERFACE_MAP_BEGIN(nsDocShellTreeOwner)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDocShellTreeOwner)
+  NS_INTERFACE_MAP_ENTRY(nsIDocShellTreeOwner)
+  NS_INTERFACE_MAP_ENTRY(nsIBaseWindow)
+  NS_INTERFACE_MAP_ENTRY(nsIInterfaceRequestor)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMEventListener)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+NS_INTERFACE_MAP_END
+
+// The class that listens to the chrome events and tells the embedding chrome to
+// show tooltips, as appropriate. Handles registering itself with the DOM with
+// AddChromeListeners() and removing itself with RemoveChromeListeners().
+class ChromeTooltipListener final : public nsIDOMEventListener {
+ protected:
+  virtual ~ChromeTooltipListener();
+
+ public:
+  NS_DECL_ISUPPORTS
+
+  ChromeTooltipListener(nsWebBrowser* aInBrowser,
+                        nsIWebBrowserChrome* aInChrome);
+
+  NS_DECL_NSIDOMEVENTLISTENER
+  NS_IMETHOD MouseMove(mozilla::dom::Event* aMouseEvent);
+
+  // Add/remove the relevant listeners, based on what interfaces the embedding
+  // chrome implements.
+  NS_IMETHOD AddChromeListeners();
+  NS_IMETHOD RemoveChromeListeners();
+
+  NS_IMETHOD HideTooltip();
+
+  bool WebProgressShowedTooltip(nsIWebProgress* aWebProgress);
+
+ private:
+  // pixel tolerance for mousemove event
+  static constexpr CSSIntCoord kTooltipMouseMoveTolerance = 7;
+
+  NS_IMETHOD AddTooltipListener();
+  NS_IMETHOD RemoveTooltipListener();
+
+  NS_IMETHOD ShowTooltip(int32_t aInXCoords, int32_t aInYCoords,
+                         const nsAString& aInTipText,
+                         const nsAString& aDirText);
+  nsITooltipTextProvider* GetTooltipTextProvider();
+
+  nsWebBrowser* mWebBrowser;
+  nsCOMPtr<mozilla::dom::EventTarget> mEventTarget;
+  nsCOMPtr<nsITooltipTextProvider> mTooltipTextProvider;
+
+  // This must be a strong ref in order to make sure we can hide the tooltip if
+  // the window goes away while we're displaying one. If we don't hold a strong
+  // ref, the chrome might have been disposed of before we get a chance to tell
+  // it, and no one would ever tell us of that fact.
+  nsCOMPtr<nsIWebBrowserChrome> mWebBrowserChrome;
+
+  bool mTooltipListenerInstalled;
+
+  nsCOMPtr<nsITimer> mTooltipTimer;
+  static void sTooltipCallback(nsITimer* aTimer, void* aListener);
+
+  // Mouse coordinates for last mousemove event we saw
+  CSSIntPoint mMouseClientPoint;
+
+  // Mouse coordinates for tooltip event
+  LayoutDeviceIntPoint mMouseScreenPoint;
+
+  bool mShowingTooltip;
+
+  bool mTooltipShownOnce;
+
+  // The string of text that we last displayed.
+  nsString mLastShownTooltipText;
+
+  nsWeakPtr mLastDocshell;
+
+  // The node hovered over that fired the timer. This may turn into the node
+  // that triggered the tooltip, but only if the timer ever gets around to
+  // firing. This is a strong reference, because the tooltip content can be
+  // destroyed while we're waiting for the tooltip to pop up, and we need to
+  // detect that. It's set only when the tooltip timer is created and launched.
+  // The timer must either fire or be cancelled (or possibly released?), and we
+  // release this reference in each of those cases. So we don't leak.
+  nsCOMPtr<nsINode> mPossibleTooltipNode;
+};
+
+//*****************************************************************************
+// nsDocShellTreeOwner::nsIInterfaceRequestor
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetInterface(const nsIID& aIID, void** aSink) {
+  NS_ENSURE_ARG_POINTER(aSink);
+
+  if (NS_SUCCEEDED(QueryInterface(aIID, aSink))) {
+    return NS_OK;
+  }
+
+  if (aIID.Equals(NS_GET_IID(nsIWebBrowserChromeFocus))) {
+    if (mWebBrowserChromeWeak != nullptr) {
+      return mWebBrowserChromeWeak->QueryReferent(aIID, aSink);
+    }
+    return mOwnerWin->QueryInterface(aIID, aSink);
+  }
+
+  if (aIID.Equals(NS_GET_IID(nsIPrompt))) {
+    nsCOMPtr<nsIPrompt> prompt;
+    EnsurePrompter();
+    prompt = mPrompter;
+    if (prompt) {
+      prompt.forget(aSink);
+      return NS_OK;
+    }
+    return NS_NOINTERFACE;
+  }
+
+  if (aIID.Equals(NS_GET_IID(nsIAuthPrompt))) {
+    nsCOMPtr<nsIAuthPrompt> prompt;
+    EnsureAuthPrompter();
+    prompt = mAuthPrompter;
+    if (prompt) {
+      prompt.forget(aSink);
+      return NS_OK;
+    }
+    return NS_NOINTERFACE;
+  }
+
+  nsCOMPtr<nsIInterfaceRequestor> req = GetOwnerRequestor();
+  if (req) {
+    return req->GetInterface(aIID, aSink);
+  }
+
+  return NS_NOINTERFACE;
+}
+
+//*****************************************************************************
+// nsDocShellTreeOwner::nsIDocShellTreeOwner
+//*****************************************************************************
+
+void nsDocShellTreeOwner::EnsurePrompter() {
+  if (mPrompter) {
+    return;
+  }
+
+  nsCOMPtr<nsIWindowWatcher> wwatch(do_GetService(NS_WINDOWWATCHER_CONTRACTID));
+  if (wwatch && mWebBrowser) {
+    nsCOMPtr<mozIDOMWindowProxy> domWindow;
+    mWebBrowser->GetContentDOMWindow(getter_AddRefs(domWindow));
+    if (domWindow) {
+      wwatch->GetNewPrompter(domWindow, getter_AddRefs(mPrompter));
+    }
+  }
+}
+
+void nsDocShellTreeOwner::EnsureAuthPrompter() {
+  if (mAuthPrompter) {
+    return;
+  }
+
+  nsCOMPtr<nsIWindowWatcher> wwatch(do_GetService(NS_WINDOWWATCHER_CONTRACTID));
+  if (wwatch && mWebBrowser) {
+    nsCOMPtr<mozIDOMWindowProxy> domWindow;
+    mWebBrowser->GetContentDOMWindow(getter_AddRefs(domWindow));
+    if (domWindow) {
+      wwatch->GetNewAuthPrompter(domWindow, getter_AddRefs(mAuthPrompter));
+    }
+  }
+}
+
+void nsDocShellTreeOwner::AddToWatcher() {
+  if (mWebBrowser) {
+    nsCOMPtr<mozIDOMWindowProxy> domWindow;
+    mWebBrowser->GetContentDOMWindow(getter_AddRefs(domWindow));
+    if (domWindow) {
+      nsCOMPtr<nsPIWindowWatcher> wwatch(
+          do_GetService(NS_WINDOWWATCHER_CONTRACTID));
+      if (wwatch) {
+        nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+        if (webBrowserChrome) {
+          wwatch->AddWindow(domWindow, webBrowserChrome);
+        }
+      }
+    }
+  }
+}
+
+void nsDocShellTreeOwner::RemoveFromWatcher() {
+  if (mWebBrowser) {
+    nsCOMPtr<mozIDOMWindowProxy> domWindow;
+    mWebBrowser->GetContentDOMWindow(getter_AddRefs(domWindow));
+    if (domWindow) {
+      nsCOMPtr<nsPIWindowWatcher> wwatch(
+          do_GetService(NS_WINDOWWATCHER_CONTRACTID));
+      if (wwatch) {
+        wwatch->RemoveWindow(domWindow);
+      }
+    }
+  }
+}
+
+void nsDocShellTreeOwner::EnsureContentTreeOwner() {
+  if (mContentTreeOwner) {
+    return;
+  }
+
+  mContentTreeOwner = new nsDocShellTreeOwner();
+  nsCOMPtr<nsIWebBrowserChrome> browserChrome = GetWebBrowserChrome();
+  if (browserChrome) {
+    mContentTreeOwner->SetWebBrowserChrome(browserChrome);
+  }
+
+  if (mWebBrowser) {
+    mContentTreeOwner->WebBrowser(mWebBrowser);
+  }
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::ContentShellAdded(nsIDocShellTreeItem* aContentShell,
+                                       bool aPrimary) {
+  if (mTreeOwner) return mTreeOwner->ContentShellAdded(aContentShell, aPrimary);
+
+  EnsureContentTreeOwner();
+  aContentShell->SetTreeOwner(mContentTreeOwner);
+
+  if (aPrimary) {
+    mPrimaryContentShell = aContentShell;
+    mPrimaryRemoteTab = nullptr;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::ContentShellRemoved(nsIDocShellTreeItem* aContentShell) {
+  if (mTreeOwner) {
+    return mTreeOwner->ContentShellRemoved(aContentShell);
+  }
+
+  if (mPrimaryContentShell == aContentShell) {
+    mPrimaryContentShell = nullptr;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPrimaryContentShell(nsIDocShellTreeItem** aShell) {
+  NS_ENSURE_ARG_POINTER(aShell);
+
+  if (mTreeOwner) {
+    return mTreeOwner->GetPrimaryContentShell(aShell);
+  }
+
+  nsCOMPtr<nsIDocShellTreeItem> shell;
+  if (!mPrimaryRemoteTab) {
+    shell =
+        mPrimaryContentShell ? mPrimaryContentShell : mWebBrowser->mDocShell;
+  }
+  shell.forget(aShell);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::RemoteTabAdded(nsIRemoteTab* aTab, bool aPrimary) {
+  if (mTreeOwner) {
+    return mTreeOwner->RemoteTabAdded(aTab, aPrimary);
+  }
+
+  if (aPrimary) {
+    mPrimaryRemoteTab = aTab;
+    mPrimaryContentShell = nullptr;
+  } else if (mPrimaryRemoteTab == aTab) {
+    mPrimaryRemoteTab = nullptr;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::RemoteTabRemoved(nsIRemoteTab* aTab) {
+  if (mTreeOwner) {
+    return mTreeOwner->RemoteTabRemoved(aTab);
+  }
+
+  if (aTab == mPrimaryRemoteTab) {
+    mPrimaryRemoteTab = nullptr;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPrimaryRemoteTab(nsIRemoteTab** aTab) {
+  if (mTreeOwner) {
+    return mTreeOwner->GetPrimaryRemoteTab(aTab);
+  }
+
+  nsCOMPtr<nsIRemoteTab> tab = mPrimaryRemoteTab;
+  tab.forget(aTab);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPrimaryContentBrowsingContext(
+    mozilla::dom::BrowsingContext** aBc) {
+  if (mTreeOwner) {
+    return mTreeOwner->GetPrimaryContentBrowsingContext(aBc);
+  }
+  if (mPrimaryRemoteTab) {
+    return mPrimaryRemoteTab->GetBrowsingContext(aBc);
+  }
+  if (mPrimaryContentShell) {
+    return mPrimaryContentShell->GetBrowsingContextXPCOM(aBc);
+  }
+  if (mWebBrowser->mDocShell) {
+    return mWebBrowser->mDocShell->GetBrowsingContextXPCOM(aBc);
+  }
+  *aBc = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPrimaryContentSize(int32_t* aWidth, int32_t* aHeight) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetPrimaryContentSize(int32_t aWidth, int32_t aHeight) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetRootShellSize(int32_t* aWidth, int32_t* aHeight) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetRootShellSize(int32_t aWidth, int32_t aHeight) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SizeShellTo(nsIDocShellTreeItem* aShellItem, int32_t aCX,
+                                 int32_t aCY) {
+  nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+
+  NS_ENSURE_STATE(mTreeOwner || webBrowserChrome);
+
+  if (nsCOMPtr<nsIDocShellTreeOwner> treeOwner = mTreeOwner) {
+    return treeOwner->SizeShellTo(aShellItem, aCX, aCY);
+  }
+
+  if (aShellItem == mWebBrowser->mDocShell) {
+    nsCOMPtr<nsIBrowserChild> browserChild =
+        do_QueryInterface(webBrowserChrome);
+    if (browserChild) {
+      // The XUL window to resize is in the parent process, but there we
+      // won't be able to get the size of aShellItem. We can ask the parent
+      // process to change our size instead.
+      nsCOMPtr<nsIBaseWindow> shellAsWin(do_QueryInterface(aShellItem));
+      NS_ENSURE_TRUE(shellAsWin, NS_ERROR_FAILURE);
+
+      LayoutDeviceIntSize shellSize;
+      shellAsWin->GetSize(&shellSize.width, &shellSize.height);
+      LayoutDeviceIntSize deltaSize = LayoutDeviceIntSize(aCX, aCY) - shellSize;
+
+      LayoutDeviceIntSize currentSize;
+      GetSize(&currentSize.width, &currentSize.height);
+
+      LayoutDeviceIntSize newSize = currentSize + deltaSize;
+      return SetSize(newSize.width, newSize.height, true);
+    }
+    // XXX: this is weird, but we used to call a method here
+    // (webBrowserChrome->SizeBrowserTo()) whose implementations all failed
+    // like this, so...
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("This is unimplemented, API should be cleaned up");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetPersistence(bool aPersistPosition, bool aPersistSize,
+                                    bool aPersistSizeMode) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPersistence(bool* aPersistPosition, bool* aPersistSize,
+                                    bool* aPersistSizeMode) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetTabCount(uint32_t* aResult) {
+  if (mTreeOwner) {
+    return mTreeOwner->GetTabCount(aResult);
+  }
+
+  *aResult = 0;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetHasPrimaryContent(bool* aResult) {
+  *aResult = mPrimaryRemoteTab || mPrimaryContentShell;
+  return NS_OK;
+}
+
+//*****************************************************************************
+// nsDocShellTreeOwner::nsIBaseWindow
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::InitWindow(nativeWindow aParentNativeWindow,
+                                nsIWidget* aParentWidget, int32_t aX,
+                                int32_t aY, int32_t aCX, int32_t aCY) {
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::Destroy() {
+  nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+  if (webBrowserChrome) {
+    // XXX: this is weird, but we used to call a method here
+    // (webBrowserChrome->DestroyBrowserWindow()) whose implementations all
+    // failed like this, so...
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+  return NS_ERROR_NULL_POINTER;
+}
+
+double nsDocShellTreeOwner::GetWidgetCSSToDeviceScale() {
+  return mWebBrowser ? mWebBrowser->GetWidgetCSSToDeviceScale() : 1.0;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetDevicePixelsPerDesktopPixel(double* aScale) {
+  if (mWebBrowser) {
+    return mWebBrowser->GetDevicePixelsPerDesktopPixel(aScale);
+  }
+
+  *aScale = 1.0;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetPositionDesktopPix(int32_t aX, int32_t aY) {
+  if (mWebBrowser) {
+    nsresult rv = mWebBrowser->SetPositionDesktopPix(aX, aY);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  double scale = 1.0;
+  GetDevicePixelsPerDesktopPixel(&scale);
+  return SetPosition(NSToIntRound(aX * scale), NSToIntRound(aY * scale));
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetPosition(int32_t aX, int32_t aY) {
+  return SetDimensions(
+      {DimensionKind::Outer, Some(aX), Some(aY), Nothing(), Nothing()});
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPosition(int32_t* aX, int32_t* aY) {
+  return GetDimensions(DimensionKind::Outer, aX, aY, nullptr, nullptr);
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetSize(int32_t aCX, int32_t aCY, bool aRepaint) {
+  return SetDimensions(
+      {DimensionKind::Outer, Nothing(), Nothing(), Some(aCX), Some(aCY)});
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetSize(int32_t* aCX, int32_t* aCY) {
+  return GetDimensions(DimensionKind::Outer, nullptr, nullptr, aCX, aCY);
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetPositionAndSize(int32_t aX, int32_t aY, int32_t aCX,
+                                        int32_t aCY, uint32_t aFlags) {
+  return SetDimensions(
+      {DimensionKind::Outer, Some(aX), Some(aY), Some(aCX), Some(aCY)});
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetPositionAndSize(int32_t* aX, int32_t* aY, int32_t* aCX,
+                                        int32_t* aCY) {
+  return GetDimensions(DimensionKind::Outer, aX, aY, aCX, aCY);
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetDimensions(DimensionRequest&& aRequest) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->SetDimensions(std::move(aRequest));
+  }
+
+  nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+  NS_ENSURE_STATE(webBrowserChrome);
+  return webBrowserChrome->SetDimensions(std::move(aRequest));
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetDimensions(DimensionKind aDimensionKind, int32_t* aX,
+                                   int32_t* aY, int32_t* aCX, int32_t* aCY) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->GetDimensions(aDimensionKind, aX, aY, aCX, aCY);
+  }
+
+  nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+  NS_ENSURE_STATE(webBrowserChrome);
+  return webBrowserChrome->GetDimensions(aDimensionKind, aX, aY, aCX, aCY);
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::Repaint(bool aForce) { return NS_ERROR_NULL_POINTER; }
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetParentWidget(nsIWidget** aParentWidget) {
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetParentWidget(nsIWidget* aParentWidget) {
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetParentNativeWindow(nativeWindow* aParentNativeWindow) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->GetParentNativeWindow(aParentNativeWindow);
+  }
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetParentNativeWindow(nativeWindow aParentNativeWindow) {
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetNativeHandle(nsAString& aNativeHandle) {
+  // the nativeHandle should be accessed from nsIAppWindow
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetVisibility(bool* aVisibility) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->GetVisibility(aVisibility);
+  }
+
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetVisibility(bool aVisibility) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->SetVisibility(aVisibility);
+  }
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetEnabled(bool* aEnabled) {
+  NS_ENSURE_ARG_POINTER(aEnabled);
+  *aEnabled = true;
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetEnabled(bool aEnabled) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetMainWidget(nsIWidget** aMainWidget) {
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::GetTitle(nsAString& aTitle) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->GetTitle(aTitle);
+  }
+  return NS_ERROR_NULL_POINTER;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetTitle(const nsAString& aTitle) {
+  nsCOMPtr<nsIBaseWindow> ownerWin = GetOwnerWin();
+  if (ownerWin) {
+    return ownerWin->SetTitle(aTitle);
+  }
+  return NS_ERROR_NULL_POINTER;
+}
+
+//*****************************************************************************
+// nsDocShellTreeOwner::nsIWebProgressListener
+//*****************************************************************************
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::OnProgressChange(nsIWebProgress* aProgress,
+                                      nsIRequest* aRequest,
+                                      int32_t aCurSelfProgress,
+                                      int32_t aMaxSelfProgress,
+                                      int32_t aCurTotalProgress,
+                                      int32_t aMaxTotalProgress) {
+  // In the absence of DOM document creation event, this method is the
+  // most convenient place to install the mouse listener on the
+  // DOM document.
+  return AddChromeListeners();
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::OnStateChange(nsIWebProgress* aProgress,
+                                   nsIRequest* aRequest,
+                                   uint32_t aProgressStateFlags,
+                                   nsresult aStatus) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::OnLocationChange(nsIWebProgress* aWebProgress,
+                                      nsIRequest* aRequest, nsIURI* aURI,
+                                      uint32_t aFlags) {
+  if (mChromeTooltipListener && aWebProgress &&
+      !(aFlags & nsIWebProgressListener::LOCATION_CHANGE_SAME_DOCUMENT) &&
+      mChromeTooltipListener->WebProgressShowedTooltip(aWebProgress)) {
+    mChromeTooltipListener->HideTooltip();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::OnStatusChange(nsIWebProgress* aWebProgress,
+                                    nsIRequest* aRequest, nsresult aStatus,
+                                    const char16_t* aMessage) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::OnSecurityChange(nsIWebProgress* aWebProgress,
+                                      nsIRequest* aRequest, uint32_t aState) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                            nsIRequest* aRequest,
+                                            uint32_t aEvent) {
+  return NS_OK;
+}
+
+//*****************************************************************************
+// nsDocShellTreeOwner: Accessors
+//*****************************************************************************
+
+void nsDocShellTreeOwner::WebBrowser(nsWebBrowser* aWebBrowser) {
+  if (!aWebBrowser) {
+    RemoveChromeListeners();
+  }
+  if (aWebBrowser != mWebBrowser) {
+    mPrompter = nullptr;
+    mAuthPrompter = nullptr;
+  }
+
+  mWebBrowser = aWebBrowser;
+
+  if (mContentTreeOwner) {
+    mContentTreeOwner->WebBrowser(aWebBrowser);
+    if (!aWebBrowser) {
+      mContentTreeOwner = nullptr;
+    }
+  }
+}
+
+nsWebBrowser* nsDocShellTreeOwner::WebBrowser() { return mWebBrowser; }
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetTreeOwner(nsIDocShellTreeOwner* aTreeOwner) {
+  if (aTreeOwner) {
+    nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome(do_GetInterface(aTreeOwner));
+    NS_ENSURE_TRUE(webBrowserChrome, NS_ERROR_INVALID_ARG);
+    NS_ENSURE_SUCCESS(SetWebBrowserChrome(webBrowserChrome),
+                      NS_ERROR_INVALID_ARG);
+    mTreeOwner = aTreeOwner;
+  } else {
+    mTreeOwner = nullptr;
+    nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+    if (!webBrowserChrome) {
+      NS_ENSURE_SUCCESS(SetWebBrowserChrome(nullptr), NS_ERROR_FAILURE);
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::SetWebBrowserChrome(
+    nsIWebBrowserChrome* aWebBrowserChrome) {
+  if (!aWebBrowserChrome) {
+    mWebBrowserChrome = nullptr;
+    mOwnerWin = nullptr;
+    mOwnerRequestor = nullptr;
+    mWebBrowserChromeWeak = nullptr;
+  } else {
+    nsCOMPtr<nsISupportsWeakReference> supportsweak =
+        do_QueryInterface(aWebBrowserChrome);
+    if (supportsweak) {
+      supportsweak->GetWeakReference(getter_AddRefs(mWebBrowserChromeWeak));
+    } else {
+      nsCOMPtr<nsIBaseWindow> ownerWin(do_QueryInterface(aWebBrowserChrome));
+      nsCOMPtr<nsIInterfaceRequestor> requestor(
+          do_QueryInterface(aWebBrowserChrome));
+
+      // it's ok for ownerWin or requestor to be null.
+      mWebBrowserChrome = aWebBrowserChrome;
+      mOwnerWin = ownerWin;
+      mOwnerRequestor = requestor;
+    }
+  }
+
+  if (mContentTreeOwner) {
+    mContentTreeOwner->SetWebBrowserChrome(aWebBrowserChrome);
+  }
+
+  return NS_OK;
+}
+
+// Hook up things to the chrome like context menus and tooltips, if the chrome
+// has implemented the right interfaces.
+NS_IMETHODIMP
+nsDocShellTreeOwner::AddChromeListeners() {
+  nsresult rv = NS_OK;
+
+  nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome = GetWebBrowserChrome();
+  if (!webBrowserChrome) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // install tooltips
+  if (!mChromeTooltipListener) {
+    nsCOMPtr<nsITooltipListener> tooltipListener(
+        do_QueryInterface(webBrowserChrome));
+    if (tooltipListener) {
+      mChromeTooltipListener =
+          new ChromeTooltipListener(mWebBrowser, webBrowserChrome);
+      rv = mChromeTooltipListener->AddChromeListeners();
+    }
+  }
+
+  nsCOMPtr<EventTarget> target;
+  GetDOMEventTarget(mWebBrowser, getter_AddRefs(target));
+
+  // register dragover and drop event listeners with the listener manager
+  MOZ_ASSERT(target, "how does this happen? (see bug 1659758)");
+  if (target) {
+    if (EventListenerManager* elmP = target->GetOrCreateListenerManager()) {
+      elmP->AddEventListenerByType(this, u"dragover"_ns,
+                                   TrustedEventsAtSystemGroupBubble());
+      elmP->AddEventListenerByType(this, u"drop"_ns,
+                                   TrustedEventsAtSystemGroupBubble());
+    }
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::RemoveChromeListeners() {
+  if (mChromeTooltipListener) {
+    mChromeTooltipListener->RemoveChromeListeners();
+    mChromeTooltipListener = nullptr;
+  }
+
+  nsCOMPtr<EventTarget> piTarget;
+  GetDOMEventTarget(mWebBrowser, getter_AddRefs(piTarget));
+  if (!piTarget) {
+    return NS_OK;
+  }
+
+  EventListenerManager* elmP = piTarget->GetOrCreateListenerManager();
+  if (elmP) {
+    elmP->RemoveEventListenerByType(this, u"dragover"_ns,
+                                    TrustedEventsAtSystemGroupBubble());
+    elmP->RemoveEventListenerByType(this, u"drop"_ns,
+                                    TrustedEventsAtSystemGroupBubble());
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShellTreeOwner::HandleEvent(Event* aEvent) {
+  DragEvent* dragEvent = aEvent ? aEvent->AsDragEvent() : nullptr;
+  if (NS_WARN_IF(!dragEvent)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (dragEvent->DefaultPrevented()) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIDroppedLinkHandler> handler =
+      do_GetService("@mozilla.org/content/dropped-link-handler;1");
+  if (!handler) {
+    return NS_OK;
+  }
+
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+  if (eventType.EqualsLiteral("dragover")) {
+    bool canDropLink = false;
+    handler->CanDropLink(dragEvent, false, &canDropLink);
+    if (canDropLink) {
+      aEvent->PreventDefault();
+    }
+  } else if (eventType.EqualsLiteral("drop")) {
+    nsCOMPtr<nsIWebNavigation> webnav =
+        static_cast<nsIWebNavigation*>(mWebBrowser);
+
+    // The page might have cancelled the dragover event itself, so check to
+    // make sure that the link can be dropped first.
+    bool canDropLink = false;
+    handler->CanDropLink(dragEvent, false, &canDropLink);
+    if (!canDropLink) {
+      return NS_OK;
+    }
+
+    nsTArray<RefPtr<nsIDroppedLinkItem>> links;
+    if (webnav && NS_SUCCEEDED(handler->DropLinks(dragEvent, true, links))) {
+      if (links.Length() >= 1) {
+        nsCOMPtr<nsIPrincipal> triggeringPrincipal;
+        handler->GetTriggeringPrincipal(dragEvent,
+                                        getter_AddRefs(triggeringPrincipal));
+        if (triggeringPrincipal) {
+          nsCOMPtr<nsIWebBrowserChrome> webBrowserChrome =
+              GetWebBrowserChrome();
+          if (webBrowserChrome) {
+            nsCOMPtr<nsIBrowserChild> browserChild =
+                do_QueryInterface(webBrowserChrome);
+            if (browserChild) {
+              nsresult rv = browserChild->RemoteDropLinks(links);
+              return rv;
+            }
+          }
+          nsAutoString url;
+          if (NS_SUCCEEDED(links[0]->GetUrl(url))) {
+            if (!url.IsEmpty()) {
+#ifndef ANDROID
+              MOZ_ASSERT(triggeringPrincipal,
+                         "nsDocShellTreeOwner::HandleEvent: Need a valid "
+                         "triggeringPrincipal");
+#endif
+              LoadURIOptions loadURIOptions;
+              loadURIOptions.mTriggeringPrincipal = triggeringPrincipal;
+              nsCOMPtr<nsIContentSecurityPolicy> csp;
+              handler->GetCsp(dragEvent, getter_AddRefs(csp));
+              loadURIOptions.mCsp = csp;
+              webnav->FixupAndLoadURIString(url, loadURIOptions);
+            }
+          }
+        }
+      }
+    } else {
+      aEvent->StopPropagation();
+      aEvent->PreventDefault();
+    }
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<nsIWebBrowserChrome>
+nsDocShellTreeOwner::GetWebBrowserChrome() {
+  nsCOMPtr<nsIWebBrowserChrome> chrome;
+  if (mWebBrowserChromeWeak) {
+    chrome = do_QueryReferent(mWebBrowserChromeWeak);
+  } else if (mWebBrowserChrome) {
+    chrome = mWebBrowserChrome;
+  }
+  return chrome.forget();
+}
+
+already_AddRefed<nsIBaseWindow> nsDocShellTreeOwner::GetOwnerWin() {
+  nsCOMPtr<nsIBaseWindow> win;
+  if (mWebBrowserChromeWeak) {
+    win = do_QueryReferent(mWebBrowserChromeWeak);
+  } else if (mOwnerWin) {
+    win = mOwnerWin;
+  }
+  return win.forget();
+}
+
+already_AddRefed<nsIInterfaceRequestor>
+nsDocShellTreeOwner::GetOwnerRequestor() {
+  nsCOMPtr<nsIInterfaceRequestor> req;
+  if (mWebBrowserChromeWeak) {
+    req = do_QueryReferent(mWebBrowserChromeWeak);
+  } else if (mOwnerRequestor) {
+    req = mOwnerRequestor;
+  }
+  return req.forget();
+}
+
+NS_IMPL_ISUPPORTS(ChromeTooltipListener, nsIDOMEventListener)
+
+ChromeTooltipListener::ChromeTooltipListener(nsWebBrowser* aInBrowser,
+                                             nsIWebBrowserChrome* aInChrome)
+    : mWebBrowser(aInBrowser),
+      mWebBrowserChrome(aInChrome),
+      mTooltipListenerInstalled(false),
+      mShowingTooltip(false),
+      mTooltipShownOnce(false) {}
+
+ChromeTooltipListener::~ChromeTooltipListener() {}
+
+nsITooltipTextProvider* ChromeTooltipListener::GetTooltipTextProvider() {
+  if (!mTooltipTextProvider) {
+    mTooltipTextProvider = do_GetService(NS_TOOLTIPTEXTPROVIDER_CONTRACTID);
+  }
+
+  if (!mTooltipTextProvider) {
+    mTooltipTextProvider =
+        do_GetService(NS_DEFAULTTOOLTIPTEXTPROVIDER_CONTRACTID);
+  }
+
+  return mTooltipTextProvider;
+}
+
+// Hook up things to the chrome like context menus and tooltips, if the chrome
+// has implemented the right interfaces.
+NS_IMETHODIMP
+ChromeTooltipListener::AddChromeListeners() {
+  if (!mEventTarget) {
+    GetDOMEventTarget(mWebBrowser, getter_AddRefs(mEventTarget));
+  }
+
+  // Register the appropriate events for tooltips, but only if
+  // the embedding chrome cares.
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsITooltipListener> tooltipListener(
+      do_QueryInterface(mWebBrowserChrome));
+  if (tooltipListener && !mTooltipListenerInstalled) {
+    rv = AddTooltipListener();
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+
+  return rv;
+}
+
+// Subscribe to the events that will allow us to track tooltips. We need "mouse"
+// for mouseExit, "mouse motion" for mouseMove, and "key" for keyDown. As we
+// add the listeners, keep track of how many succeed so we can clean up
+// correctly in Release().
+NS_IMETHODIMP
+ChromeTooltipListener::AddTooltipListener() {
+  if (mEventTarget) {
+    MOZ_TRY(mEventTarget->AddSystemEventListener(u"keydown"_ns, this, false,
+                                                 false));
+    MOZ_TRY(mEventTarget->AddSystemEventListener(u"mousedown"_ns, this, false,
+                                                 false));
+    MOZ_TRY(mEventTarget->AddSystemEventListener(u"mouseout"_ns, this, false,
+                                                 false));
+    MOZ_TRY(mEventTarget->AddSystemEventListener(u"mousemove"_ns, this, false,
+                                                 false));
+
+    mTooltipListenerInstalled = true;
+  }
+
+  return NS_OK;
+}
+
+// Unsubscribe from the various things we've hooked up to the window root.
+NS_IMETHODIMP
+ChromeTooltipListener::RemoveChromeListeners() {
+  HideTooltip();
+
+  if (mTooltipListenerInstalled) {
+    RemoveTooltipListener();
+  }
+
+  mEventTarget = nullptr;
+
+  // it really doesn't matter if these fail...
+  return NS_OK;
+}
+
+// Unsubscribe from all the various tooltip events that we were listening to.
+NS_IMETHODIMP
+ChromeTooltipListener::RemoveTooltipListener() {
+  if (mEventTarget) {
+    mEventTarget->RemoveSystemEventListener(u"keydown"_ns, this, false);
+    mEventTarget->RemoveSystemEventListener(u"mousedown"_ns, this, false);
+    mEventTarget->RemoveSystemEventListener(u"mouseout"_ns, this, false);
+    mEventTarget->RemoveSystemEventListener(u"mousemove"_ns, this, false);
+    mTooltipListenerInstalled = false;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ChromeTooltipListener::HandleEvent(Event* aEvent) {
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+
+  if (eventType.EqualsLiteral("mousedown")) {
+    return HideTooltip();
+  } else if (eventType.EqualsLiteral("keydown")) {
+    WidgetKeyboardEvent* keyEvent = aEvent->WidgetEventPtr()->AsKeyboardEvent();
+    if (nsXULTooltipListener::KeyEventHidesTooltip(*keyEvent)) {
+      return HideTooltip();
+    }
+    return NS_OK;
+  } else if (eventType.EqualsLiteral("mouseout")) {
+    // Reset flag so that tooltip will display on the next MouseMove
+    mTooltipShownOnce = false;
+    return HideTooltip();
+  } else if (eventType.EqualsLiteral("mousemove")) {
+    return MouseMove(aEvent);
+  }
+
+  NS_ERROR("Unexpected event type");
+  return NS_OK;
+}
+
+// If we're a tooltip, fire off a timer to see if a tooltip should be shown. If
+// the timer fires, we cache the node in |mPossibleTooltipNode|.
+nsresult ChromeTooltipListener::MouseMove(Event* aMouseEvent) {
+  if (!nsXULTooltipListener::ShowTooltips()) {
+    return NS_OK;
+  }
+
+  MouseEvent* mouseEvent = aMouseEvent->AsMouseEvent();
+  if (!mouseEvent) {
+    return NS_OK;
+  }
+
+  // stash the coordinates of the event so that we can still get back to it from
+  // within the timer callback. On win32, we'll get a MouseMove event even when
+  // a popup goes away -- even when the mouse doesn't change position! To get
+  // around this, we make sure the mouse has really moved before proceeding.
+  CSSIntPoint newMouseClientPoint = mouseEvent->ClientPoint();
+  if (mMouseClientPoint == newMouseClientPoint) {
+    return NS_OK;
+  }
+
+  // Filter out minor mouse movements.
+  if (mShowingTooltip &&
+      (abs(mMouseClientPoint.x - newMouseClientPoint.x) <=
+       kTooltipMouseMoveTolerance) &&
+      (abs(mMouseClientPoint.y - newMouseClientPoint.y) <=
+       kTooltipMouseMoveTolerance)) {
+    return NS_OK;
+  }
+
+  mMouseClientPoint = newMouseClientPoint;
+  mMouseScreenPoint = mouseEvent->ScreenPointLayoutDevicePix();
+
+  if (mTooltipTimer) {
+    mTooltipTimer->Cancel();
+    mTooltipTimer = nullptr;
+  }
+
+  if (!mShowingTooltip) {
+    if (nsCOMPtr<EventTarget> eventTarget = aMouseEvent->GetComposedTarget()) {
+      mPossibleTooltipNode = nsINode::FromEventTarget(eventTarget);
+    }
+
+    if (mPossibleTooltipNode) {
+      nsresult rv = NS_NewTimerWithFuncCallback(
+          getter_AddRefs(mTooltipTimer), sTooltipCallback, this,
+          LookAndFeel::GetInt(LookAndFeel::IntID::TooltipDelay, 500),
+          nsITimer::TYPE_ONE_SHOT, "ChromeTooltipListener::MouseMove",
+          GetMainThreadSerialEventTarget());
+      if (NS_FAILED(rv)) {
+        mPossibleTooltipNode = nullptr;
+        NS_WARNING("Could not create a timer for tooltip tracking");
+      }
+    }
+  } else {
+    mTooltipShownOnce = true;
+    return HideTooltip();
+  }
+
+  return NS_OK;
+}
+
+// Tell the registered chrome that they should show the tooltip.
+NS_IMETHODIMP
+ChromeTooltipListener::ShowTooltip(int32_t aInXCoords, int32_t aInYCoords,
+                                   const nsAString& aInTipText,
+                                   const nsAString& aTipDir) {
+  nsresult rv = NS_OK;
+
+  // do the work to call the client
+  nsCOMPtr<nsITooltipListener> tooltipListener(
+      do_QueryInterface(mWebBrowserChrome));
+  if (tooltipListener) {
+    rv = tooltipListener->OnShowTooltip(aInXCoords, aInYCoords, aInTipText,
+                                        aTipDir);
+    if (NS_SUCCEEDED(rv)) {
+      mShowingTooltip = true;
+    }
+  }
+
+  return rv;
+}
+
+// Tell the registered chrome that they should rollup the tooltip
+// NOTE: This routine is safe to call even if the popup is already closed.
+NS_IMETHODIMP
+ChromeTooltipListener::HideTooltip() {
+  nsresult rv = NS_OK;
+
+  // shut down the relevant timers
+  if (mTooltipTimer) {
+    mTooltipTimer->Cancel();
+    mTooltipTimer = nullptr;
+    // release tooltip target
+    mPossibleTooltipNode = nullptr;
+    mLastDocshell = nullptr;
+  }
+
+  // if we're showing the tip, tell the chrome to hide it
+  if (mShowingTooltip) {
+    nsCOMPtr<nsITooltipListener> tooltipListener(
+        do_QueryInterface(mWebBrowserChrome));
+    if (tooltipListener) {
+      rv = tooltipListener->OnHideTooltip();
+      if (NS_SUCCEEDED(rv)) {
+        mShowingTooltip = false;
+      }
+    }
+  }
+
+  return rv;
+}
+
+bool ChromeTooltipListener::WebProgressShowedTooltip(
+    nsIWebProgress* aWebProgress) {
+  nsCOMPtr<nsIDocShell> docshell = do_QueryInterface(aWebProgress);
+  nsCOMPtr<nsIDocShell> lastUsed = do_QueryReferent(mLastDocshell);
+  while (lastUsed) {
+    if (lastUsed == docshell) {
+      return true;
+    }
+    // We can't use the docshell hierarchy here, because when the parent
+    // docshell is navigated, the child docshell is disconnected (ie its
+    // references to the parent are nulled out) despite it still being
+    // alive here. So we use the document hierarchy instead:
+    Document* document = lastUsed->GetDocument();
+    if (document) {
+      document = document->GetInProcessParentDocument();
+    }
+    if (!document) {
+      break;
+    }
+    lastUsed = document->GetDocShell();
+  }
+  return false;
+}
+
+// A timer callback, fired when the mouse has hovered inside of a frame for the
+// appropriate amount of time. Getting to this point means that we should show
+// the tooltip, but only after we determine there is an appropriate TITLE
+// element.
+//
+// This relies on certain things being cached into the |aChromeTooltipListener|
+// object passed to us by the timer:
+//   -- the x/y coordinates of the mouse      (mMouseClientY, mMouseClientX)
+//   -- the dom node the user hovered over    (mPossibleTooltipNode)
+void ChromeTooltipListener::sTooltipCallback(nsITimer* aTimer,
+                                             void* aChromeTooltipListener) {
+  auto* self = static_cast<ChromeTooltipListener*>(aChromeTooltipListener);
+  if (!self || !self->mPossibleTooltipNode) {
+    return;
+  }
+  // release tooltip target once done, no matter what we do here.
+  auto cleanup = MakeScopeExit([&] { self->mPossibleTooltipNode = nullptr; });
+  if (!self->mPossibleTooltipNode->IsInComposedDoc()) {
+    return;
+  }
+  // Check that the document or its ancestors haven't been replaced.
+  {
+    Document* doc = self->mPossibleTooltipNode->OwnerDoc();
+    while (doc) {
+      if (!doc->IsCurrentActiveDocument()) {
+        return;
+      }
+      doc = doc->GetInProcessParentDocument();
+    }
+  }
+
+  nsCOMPtr<nsIDocShell> docShell =
+      do_GetInterface(static_cast<nsIWebBrowser*>(self->mWebBrowser));
+  if (!docShell || !docShell->GetBrowsingContext()->IsActive()) {
+    return;
+  }
+
+  // if there is text associated with the node, show the tip and fire
+  // off a timer to auto-hide it.
+  nsITooltipTextProvider* tooltipProvider = self->GetTooltipTextProvider();
+  if (!tooltipProvider) {
+    return;
+  }
+  nsString tooltipText;
+  nsString directionText;
+  bool textFound = false;
+  tooltipProvider->GetNodeText(self->mPossibleTooltipNode,
+                               getter_Copies(tooltipText),
+                               getter_Copies(directionText), &textFound);
+
+  if (textFound && (!self->mTooltipShownOnce ||
+                    tooltipText != self->mLastShownTooltipText)) {
+    // ShowTooltip expects screen-relative position.
+    self->ShowTooltip(self->mMouseScreenPoint.x, self->mMouseScreenPoint.y,
+                      tooltipText, directionText);
+    self->mLastShownTooltipText = std::move(tooltipText);
+    self->mLastDocshell = do_GetWeakReference(
+        self->mPossibleTooltipNode->OwnerDoc()->GetDocShell());
+  }
+}
diff --git a/docshell/base/nsDocShellTreeOwner.h b/docshell/base/nsDocShellTreeOwner.h
new file mode 100644
index 0000000000..0627357606
--- /dev/null
+++ b/docshell/base/nsDocShellTreeOwner.h
@@ -0,0 +1,111 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDocShellTreeOwner_h__
+#define nsDocShellTreeOwner_h__
+
+// Helper Classes
+#include "nsCOMPtr.h"
+#include "nsString.h"
+
+// Interfaces Needed
+#include "nsIBaseWindow.h"
+#include "nsIDocShellTreeOwner.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIWebBrowserChrome.h"
+#include "nsIDOMEventListener.h"
+#include "nsIWebProgressListener.h"
+#include "nsWeakReference.h"
+#include "nsITimer.h"
+#include "nsIPrompt.h"
+#include "nsIAuthPrompt.h"
+#include "nsITooltipTextProvider.h"
+#include "nsCTooltipTextProvider.h"
+
+namespace mozilla {
+namespace dom {
+class Event;
+class EventTarget;
+}  // namespace dom
+}  // namespace mozilla
+
+class nsIDocShellTreeItem;
+class nsWebBrowser;
+class ChromeTooltipListener;
+
+class nsDocShellTreeOwner final : public nsIDocShellTreeOwner,
+                                  public nsIBaseWindow,
+                                  public nsIInterfaceRequestor,
+                                  public nsIWebProgressListener,
+                                  public nsIDOMEventListener,
+                                  public nsSupportsWeakReference {
+  friend class nsWebBrowser;
+
+ public:
+  NS_DECL_ISUPPORTS
+
+  NS_DECL_NSIBASEWINDOW
+  NS_DECL_NSIDOCSHELLTREEOWNER
+  NS_DECL_NSIDOMEVENTLISTENER
+  NS_DECL_NSIINTERFACEREQUESTOR
+  NS_DECL_NSIWEBPROGRESSLISTENER
+
+ protected:
+  nsDocShellTreeOwner();
+  virtual ~nsDocShellTreeOwner();
+
+  void WebBrowser(nsWebBrowser* aWebBrowser);
+
+  nsWebBrowser* WebBrowser();
+  NS_IMETHOD SetTreeOwner(nsIDocShellTreeOwner* aTreeOwner);
+  NS_IMETHOD SetWebBrowserChrome(nsIWebBrowserChrome* aWebBrowserChrome);
+
+  NS_IMETHOD AddChromeListeners();
+  NS_IMETHOD RemoveChromeListeners();
+
+  void EnsurePrompter();
+  void EnsureAuthPrompter();
+
+  void AddToWatcher();
+  void RemoveFromWatcher();
+
+  void EnsureContentTreeOwner();
+
+  // These helper functions return the correct instances of the requested
+  // interfaces.  If the object passed to SetWebBrowserChrome() implements
+  // nsISupportsWeakReference, then these functions call QueryReferent on
+  // that object.  Otherwise, they return an addrefed pointer.  If the
+  // WebBrowserChrome object doesn't exist, they return nullptr.
+  already_AddRefed<nsIWebBrowserChrome> GetWebBrowserChrome();
+  already_AddRefed<nsIBaseWindow> GetOwnerWin();
+  already_AddRefed<nsIInterfaceRequestor> GetOwnerRequestor();
+
+ protected:
+  // Weak References
+  nsWebBrowser* mWebBrowser;
+  nsIDocShellTreeOwner* mTreeOwner;
+  nsIDocShellTreeItem* mPrimaryContentShell;
+
+  nsIWebBrowserChrome* mWebBrowserChrome;
+  nsIBaseWindow* mOwnerWin;
+  nsIInterfaceRequestor* mOwnerRequestor;
+
+  nsWeakPtr mWebBrowserChromeWeak;  // nsIWebBrowserChrome
+
+  // the objects that listen for chrome events like context menus and tooltips.
+  // They are separate objects to avoid circular references between |this|
+  // and the DOM.
+  RefPtr<ChromeTooltipListener> mChromeTooltipListener;
+
+  RefPtr<nsDocShellTreeOwner> mContentTreeOwner;
+
+  nsCOMPtr<nsIPrompt> mPrompter;
+  nsCOMPtr<nsIAuthPrompt> mAuthPrompter;
+  nsCOMPtr<nsIRemoteTab> mPrimaryRemoteTab;
+};
+
+#endif /* nsDocShellTreeOwner_h__ */
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
new file mode 100644
index 0000000000..21f09a517e
--- /dev/null
+++ b/docshell/base/nsIDocShell.idl
@@ -0,0 +1,766 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "domstubs.idl"
+#include "nsIDocShellTreeItem.idl"
+#include "nsIRequest.idl"
+
+%{ C++
+#include "js/TypeDecls.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/NotNull.h"
+#include "mozilla/UniquePtr.h"
+#include "nsCOMPtr.h"
+#include "nsIURI.h"
+class nsCommandManager;
+class nsPresContext;
+class nsDocShellLoadState;
+namespace mozilla {
+class Encoding;
+class HTMLEditor;
+class PresShell;
+namespace dom {
+class BrowsingContext;
+class ClientSource;
+} // namespace dom
+}
+%}
+
+/**
+ * The nsIDocShell interface.
+ */
+
+[ptr] native nsPresContext(nsPresContext);
+[ptr] native nsCommandManager(nsCommandManager);
+[ptr] native PresShell(mozilla::PresShell);
+[ref] native MaybeURI(mozilla::Maybe<nsCOMPtr<nsIURI>>);
+[ref] native Encoding(const mozilla::Encoding*);
+      native UniqueClientSource(mozilla::UniquePtr<mozilla::dom::ClientSource>);
+
+interface nsIURI;
+interface nsIChannel;
+interface nsIContentSecurityPolicy;
+interface nsIDocumentViewer;
+interface nsIEditor;
+interface nsIEditingSession;
+interface nsIInputStream;
+interface nsIRequest;
+interface nsISHEntry;
+interface nsILayoutHistoryState;
+interface nsISecureBrowserUI;
+interface nsIScriptGlobalObject;
+interface nsIStructuredCloneContainer;
+interface nsIDOMStorage;
+interface nsIPrincipal;
+interface nsIPrivacyTransitionObserver;
+interface nsIReflowObserver;
+interface nsIScrollObserver;
+interface nsIRemoteTab;
+interface nsIBrowserChild;
+interface nsICommandParams;
+interface nsILoadURIDelegate;
+native BrowserChildRef(already_AddRefed<nsIBrowserChild>);
+native nsDocShellLoadStatePtr(nsDocShellLoadState*);
+
+webidl BrowsingContext;
+webidl ContentFrameMessageManager;
+webidl EventTarget;
+webidl Document;
+
+/**
+ * nsIDocShell is an interface corresponding to the native nsDocShell object,
+ * which is a legacy in-process object roughly corresponding to a 'browsing
+ * context', as created for a browser tab or an iframe, for example.
+ *
+ * nsIDocShell has a 1:1 relationship with its paired dom::BrowsingContext and
+ * nsGlobalWindowOuter. It may be replaced during navigation.
+ *
+ * See also the comment documenting dom::BrowsingContext and the documentation
+ * at:
+ *
+ * https://html.spec.whatwg.org/multipage/document-sequences.html#browsing-context
+ * https://firefox-source-docs.mozilla.org/dom/navigation/embedding.html
+ * https://firefox-source-docs.mozilla.org/dom/navigation/nav_replace.html
+ */
+[scriptable, builtinclass, uuid(049234fe-da10-478b-bc5d-bc6f9a1ba63d)]
+interface nsIDocShell : nsIDocShellTreeItem
+{
+  void setCancelContentJSEpoch(in long aEpoch);
+
+  /**
+   * Loads a given URI.  This will give priority to loading the requested URI
+   * in the object implementing this interface.  If it can't be loaded here
+   * however, the URL dispatcher will go through its normal process of content
+   * loading.
+   *
+   * @param aLoadState This is the extended load info for this load.
+   * @param aSetNavigating If we should set isNavigating to true while initiating
+   *                       the load.
+   */
+  [noscript]void loadURI(in nsDocShellLoadStatePtr aLoadState, in boolean aSetNavigating);
+
+  /**
+   * Do either a history.pushState() or history.replaceState() operation,
+   * depending on the value of aReplace.
+   */
+  [implicit_jscontext]
+  void addState(in jsval aData, in AString aTitle,
+                in AString aURL, in boolean aReplace);
+
+  /**
+   * Reset state to a new content model within the current document and the document
+   * viewer.  Called by the document before initiating an out of band document.write().
+   */
+  void prepareForNewContentModel();
+
+  /**
+   * Helper for the session store to change the URI associated with the
+   * document.
+   */
+  void setCurrentURIForSessionStore(in nsIURI aURI);
+
+  /**
+   * Notify the associated content viewer and all child docshells that they are
+   * about to be hidden.  If |isUnload| is true, then the document is being
+   * unloaded and all dynamic subframe history entries are removed as well.
+   *
+   * @param isUnload
+   *        True to fire the unload event in addition to the pagehide event,
+   *        and remove all dynamic subframe history entries.
+   */
+  [noscript] void firePageHideNotification(in boolean isUnload);
+
+  /**
+   * Presentation context for the currently loaded document.  This may be null.
+   */
+  [notxpcom,nostdcall] readonly attribute nsPresContext presContext;
+
+  /**
+   * Presentation shell for the currently loaded document.  This may be null.
+   */
+  [notxpcom,nostdcall] readonly attribute PresShell presShell;
+
+  /**
+   * Presentation shell for the oldest document, if this docshell is
+   * currently transitioning between documents.
+   */
+  [notxpcom,nostdcall] readonly attribute PresShell eldestPresShell;
+
+  /**
+   * Document Viewer that is currently loaded for this DocShell.  This may
+   * change as the underlying content changes.
+   */
+  [infallible] readonly attribute nsIDocumentViewer docViewer;
+
+  /**
+   * Get the id of the outer window that is or will be in this docshell.
+   */
+  [infallible] readonly attribute unsigned long long outerWindowID;
+
+  /**
+   * This attribute allows chrome to tie in to handle DOM events that may
+   * be of interest to chrome.
+   */
+  attribute EventTarget chromeEventHandler;
+
+  /**
+   * This allows chrome to set a custom User agent on a specific docshell
+   */
+  attribute AString customUserAgent;
+
+  /**
+   * Whether CSS error reporting is enabled.
+   */
+  attribute boolean cssErrorReportingEnabled;
+
+  /**
+   * Attribute stating if refresh based redirects can be allowed
+   */
+  attribute boolean allowMetaRedirects;
+
+  /**
+   * Attribute stating if it should allow subframes (framesets/iframes) or not
+   */
+  attribute boolean allowSubframes;
+
+  /**
+   * Attribute stating whether or not images should be loaded.
+   */
+  attribute boolean allowImages;
+
+  /**
+   * Attribute stating whether or not media (audio/video) should be loaded.
+   */
+  [infallible] attribute boolean allowMedia;
+
+  /**
+   * Attribute that determines whether DNS prefetch is allowed for this subtree
+   * of the docshell tree.  Defaults to true.  Setting this will make it take
+   * effect starting with the next document loaded in the docshell.
+   */
+  attribute boolean allowDNSPrefetch;
+
+  /**
+   * Attribute that determines whether window control (move/resize) is allowed.
+   */
+  attribute boolean allowWindowControl;
+
+  /**
+   * True if the docshell allows its content to be handled by a content listener
+   * other than the docshell itself, including the external helper app service,
+   * and false otherwise.  Defaults to true.
+   */
+  [infallible] attribute boolean allowContentRetargeting;
+
+  /**
+   * True if new child docshells should allow content retargeting.
+   * Setting allowContentRetargeting also overwrites this value.
+   */
+  [infallible] attribute boolean allowContentRetargetingOnChildren;
+
+  /**
+   * Get an array of this docShell and its children.
+   *
+   * @param aItemType  - Only include docShells of this type, or if typeAll,
+   *                     include all child shells.
+   *                     Uses types from nsIDocShellTreeItem.
+   * @param aDirection - Whether to enumerate forwards or backwards.
+   */
+
+  cenum DocShellEnumeratorDirection : 8 {
+    ENUMERATE_FORWARDS  = 0,
+    ENUMERATE_BACKWARDS = 1
+  };
+
+  Array<nsIDocShell> getAllDocShellsInSubtree(in long aItemType,
+                                              in nsIDocShell_DocShellEnumeratorDirection aDirection);
+
+  /**
+   * The type of application that created this window.
+   *
+   * DO NOT DELETE, see bug 176166. For firefox, this value will always be
+   * UNKNOWN. However, it is used heavily in Thunderbird/comm-central and we
+   * don't really have a great replacement at the moment, so we'll just leave it
+   * here.
+   */
+  cenum AppType : 8 {
+    APP_TYPE_UNKNOWN = 0,
+    APP_TYPE_MAIL    = 1,
+    APP_TYPE_EDITOR  = 2
+  };
+
+  [infallible] attribute nsIDocShell_AppType appType;
+
+  /**
+   * certain docshells (like the message pane)
+   * should not throw up auth dialogs
+   * because it can act as a password trojan
+   */
+  attribute boolean allowAuth;
+
+  /**
+   * Set/Get the document scale factor.  When setting this attribute, a
+   * NS_ERROR_NOT_IMPLEMENTED error may be returned by implementations
+   * not supporting zoom.  Implementations not supporting zoom should return
+   * 1.0 all the time for the Get operation.  1.0 by the way is the default
+   * of zoom.  This means 100% of normal scaling or in other words normal size
+   * no zoom.
+   */
+  attribute float zoom;
+
+  /*
+   * Tells the docshell to offer focus to its tree owner.
+   * This is currently only necessary for embedding chrome.
+   * If forDocumentNavigation is true, then document navigation should be
+   * performed, where only the root of documents are selected. Otherwise, the
+   * next element in the parent should be returned. Returns true if focus was
+   * successfully taken by the tree owner.
+   */
+  bool tabToTreeOwner(in boolean forward, in boolean forDocumentNavigation);
+
+  /**
+   * Current busy state for DocShell
+   */
+  cenum BusyFlags : 8 {
+    BUSY_FLAGS_NONE             = 0,
+    BUSY_FLAGS_BUSY             = 1,
+    BUSY_FLAGS_BEFORE_PAGE_LOAD = 2,
+    BUSY_FLAGS_PAGE_LOADING     = 4,
+  };
+
+  [infallible] readonly attribute nsIDocShell_BusyFlags busyFlags;
+
+  /**
+   * Load commands for the document
+   */
+  cenum LoadCommand : 8 {
+    LOAD_CMD_NORMAL  = 0x1,   // Normal load
+    LOAD_CMD_RELOAD  = 0x2,   // Reload
+    LOAD_CMD_HISTORY = 0x4,   // Load from history
+    LOAD_CMD_PUSHSTATE = 0x8, // History.pushState()
+  };
+
+  /*
+   * Attribute to access the loadtype for the document. LoadType Enum is
+   * defined in nsDocShellLoadTypes.h
+   */
+  [infallible] attribute unsigned long loadType;
+
+  /*
+   * Default load flags (as defined in nsIRequest) that will be set on all
+   * requests made by this docShell and propagated to all child docShells and
+   * to nsILoadGroup::defaultLoadFlags for the docShell's loadGroup.
+   * Default is no flags.  Once set, only future requests initiated by the
+   * docShell are affected, so in general, these flags should be set before
+   * the docShell loads any content.
+   */
+  attribute nsLoadFlags defaultLoadFlags;
+
+  /*
+   * returns true if the docshell is being destroyed, false otherwise
+   */
+  boolean isBeingDestroyed();
+
+  /*
+   * Returns true if the docshell is currently executing the onLoad Handler
+   */
+  readonly attribute boolean isExecutingOnLoadHandler;
+
+  attribute nsILayoutHistoryState layoutHistoryState;
+
+  /**
+   * Object used to delegate URI loading to an upper context.
+   * Currently only set for GeckoView to allow handling of load requests
+   * at the application level.
+   */
+  readonly attribute nsILoadURIDelegate loadURIDelegate;
+
+  /**
+   * Cancel the XPCOM timers for each meta-refresh URI in this docshell,
+   * and this docshell's children, recursively. The meta-refresh timers can be
+   * restarted using resumeRefreshURIs().  If the timers are already suspended,
+   * this has no effect.
+   */
+  void suspendRefreshURIs();
+
+  /**
+   * Restart the XPCOM timers for each meta-refresh URI in this docshell,
+   * and this docshell's children, recursively.  If the timers are already
+   * running, this has no effect.
+   */
+  void resumeRefreshURIs();
+
+  /**
+   * Begin firing WebProgressListener notifications for restoring a page
+   * presentation. |viewer| is the content viewer whose document we are
+   * starting to load.  If null, it defaults to the docshell's current content
+   * viewer, creating one if necessary.  |top| should be true for the toplevel
+   * docshell that is being restored; it will be set to false when this method
+   * is called for child docshells.  This method will post an event to
+   * complete the simulated load after returning to the event loop.
+   */
+  void beginRestore(in nsIDocumentViewer viewer, in boolean top);
+
+  /**
+   * Finish firing WebProgressListener notifications and DOM events for
+   * restoring a page presentation.  This should only be called via
+   * beginRestore().
+   */
+  void finishRestore();
+
+  void clearCachedUserAgent();
+
+  void clearCachedPlatform();
+
+  /* Track whether we're currently restoring a document presentation. */
+  readonly attribute boolean restoringDocument;
+
+  /* attribute to access whether error pages are enabled */
+  attribute boolean useErrorPages;
+
+  /**
+   * Display a load error in a frame while keeping that frame's currentURI
+   * pointing correctly to the page where the error ocurred, rather than to
+   * the error document page. You must provide either the aURI or aURL parameter.
+   *
+   * @param  aError         The error code to be displayed
+   * @param  aURI           nsIURI of the page where the error happened
+   * @param  aURL           wstring of the page where the error happened
+   * @param  aFailedChannel The channel related to this error
+   *
+   * Returns whether or not we displayed an error page (note: will always
+   * return false if in-content error pages are disabled!)
+   */
+  boolean displayLoadError(in nsresult aError,
+                           in nsIURI aURI,
+                           in wstring aURL,
+                           [optional] in nsIChannel aFailedChannel);
+
+  /**
+   * The channel that failed to load and resulted in an error page.
+   * May be null. Relevant only to error pages.
+   */
+  readonly attribute nsIChannel failedChannel;
+
+  /**
+   * Keeps track of the previous nsISHEntry index and the current
+   * nsISHEntry index at the time that the doc shell begins to load.
+   * Used for ContentViewer eviction.
+   */
+  readonly attribute long previousEntryIndex;
+  readonly attribute long loadedEntryIndex;
+
+  /**
+   * Notification that entries have been removed from the beginning of a
+   * nsSHistory which has this as its rootDocShell.
+   *
+   * @param numEntries - The number of entries removed
+   */
+  void historyPurged(in long numEntries);
+
+  /**
+   * Gets the channel for the currently loaded document, if any.
+   * For a new document load, this will be the channel of the previous document
+   * until after OnLocationChange fires.
+   */
+  readonly attribute nsIChannel currentDocumentChannel;
+
+  /**
+   * Find out whether the docshell is currently in the middle of a page
+   * transition. This is set just before the pagehide/unload events fire.
+   */
+  [infallible] readonly attribute boolean isInUnload;
+
+  /**
+   * Disconnects this docshell's editor from its window, and stores the
+   * editor data in the open document's session history entry.  This
+   * should be called only during page transitions.
+   */
+  [noscript, notxpcom] void DetachEditorFromWindow();
+
+  /**
+   * Propagated to the print preview document viewer.  Must only be called on
+   * a document viewer that has been initialized for print preview.
+   */
+  void exitPrintPreview();
+
+  /**
+   * The ID of the docshell in the session history.
+   */
+  readonly attribute nsIDRef historyID;
+
+  /**
+   * Helper method for accessing this value from C++
+   */
+  [noscript, notxpcom] nsIDRef HistoryID();
+
+  /**
+   * Create a new about:blank document and content viewer.
+   * @param aPrincipal the principal to use for the new document.
+   * @param aPartitionedPrincipal the partitioned principal to use for the new
+   *        document.
+   * @param aCsp the CSP to use for the new document.
+   */
+  void createAboutBlankDocumentViewer(in nsIPrincipal aPrincipal,
+                                     in nsIPrincipal aPartitionedPrincipal,
+                                     [optional] in nsIContentSecurityPolicy aCSP);
+
+  /**
+   * Upon getting, returns the canonical encoding label of the document
+   * currently loaded into this docshell.
+   */
+  readonly attribute ACString charset;
+
+  void forceEncodingDetection();
+
+  /**
+   * In a child docshell, this is the charset of the parent docshell
+   */
+  [noscript, notxpcom, nostdcall] void setParentCharset(
+    in Encoding parentCharset,
+    in int32_t parentCharsetSource,
+    in nsIPrincipal parentCharsetPrincipal);
+  [noscript, notxpcom, nostdcall] void getParentCharset(
+    out Encoding parentCharset,
+    out int32_t parentCharsetSource,
+    out nsIPrincipal parentCharsetPrincipal);
+
+  /**
+   * Return a DOMHighResTimeStamp representing the number of
+   * milliseconds from an arbitrary point in time.  The reference
+   * point is shared by all DocShells and is also used by timestamps
+   * on markers.
+   */
+  DOMHighResTimeStamp now();
+
+  /**
+   * Add an observer to the list of parties to be notified when this docshell's
+   * private browsing status is changed. |obs| must support weak references.
+   */
+  void addWeakPrivacyTransitionObserver(in nsIPrivacyTransitionObserver obs);
+
+  /**
+   * Add an observer to the list of parties to be notified when reflows are
+   * occurring. |obs| must support weak references.
+   */
+  void addWeakReflowObserver(in nsIReflowObserver obs);
+
+  /**
+   * Remove an observer from the list of parties to be notified about reflows.
+   */
+  void removeWeakReflowObserver(in nsIReflowObserver obs);
+
+  /**
+   * Notify all attached observers that a reflow has just occurred.
+   *
+   * @param interruptible if true, the reflow was interruptible.
+   * @param start         timestamp when reflow started, in milliseconds since
+   *                      navigationStart (accurate to 1/1000 of a ms)
+   * @param end           timestamp when reflow ended, in milliseconds since
+   *                      navigationStart (accurate to 1/1000 of a ms)
+   */
+  [noscript] void notifyReflowObservers(in bool interruptible,
+                                        in DOMHighResTimeStamp start,
+                                        in DOMHighResTimeStamp end);
+
+  /**
+   * Add an observer to the list of parties to be notified when scroll position
+   * of some elements is changed.
+   */
+  [noscript] void addWeakScrollObserver(in nsIScrollObserver obs);
+
+  /**
+   * Add an observer to the list of parties to be notified when scroll position
+   * of some elements is changed.
+   */
+  [noscript] void removeWeakScrollObserver(in nsIScrollObserver obs);
+
+  /**
+   * Notify all attached observers that the scroll position of some element
+   * has changed.
+   */
+  [noscript] void notifyScrollObservers();
+
+  /**
+   * Returns true if this docshell is the top level content docshell.
+   */
+  [infallible] readonly attribute boolean isTopLevelContentDocShell;
+
+  /**
+   * True iff asynchronous panning and zooming is enabled for this
+   * docshell.
+   */
+  readonly attribute bool asyncPanZoomEnabled;
+
+  /**
+   * Indicates whether the UI may enable the character encoding menu. The UI
+   * must disable the menu when this property is false.
+   */
+  [infallible] readonly attribute boolean mayEnableCharacterEncodingMenu;
+
+           attribute  nsIEditor editor;
+  readonly attribute  boolean   editable;             /* this docShell is editable */
+  readonly attribute  boolean   hasEditingSession;    /* this docShell has an editing session */
+
+  /**
+   * Make this docShell editable, setting a flag that causes
+   * an editor to get created, either immediately, or after
+   * a url has been loaded.
+   *      @param  inWaitForUriLoad    true to wait for a URI before
+   *                                  creating the editor.
+   */
+  void makeEditable(in boolean inWaitForUriLoad);
+
+  /**
+   * Returns false for mLSHE, true for mOSHE
+   */
+  boolean getCurrentSHEntry(out nsISHEntry aEntry);
+
+  /**
+    * Cherry picked parts of nsIController.
+    * They are here, because we want to call these functions
+    * from JS.
+    */
+  boolean isCommandEnabled(in string command);
+  [can_run_script]
+  void doCommand(in string command);
+  [can_run_script]
+  void doCommandWithParams(in string command, in nsICommandParams aParams);
+
+  /**
+   * Invisible DocShell are dummy construct to simulate DOM windows
+   * without any actual visual representation. They have to be marked
+   * at construction time, to avoid any painting activity.
+   */
+  [noscript, notxpcom] bool IsInvisible();
+  [noscript, notxpcom] void SetInvisible(in bool aIsInvisibleDocshell);
+
+/**
+ * Get the script global for the document in this docshell.
+*/
+  [noscript,notxpcom,nostdcall] nsIScriptGlobalObject GetScriptGlobalObject();
+
+  [noscript,notxpcom,nostdcall] Document getExtantDocument();
+
+  /**
+   * This attribute determines whether a document which is not about:blank has
+   * already be loaded by this docShell.
+   */
+  [infallible] readonly attribute boolean hasLoadedNonBlankURI;
+
+  /**
+   * Allow usage of -moz-window-dragging:drag for content docshells.
+   * True for top level chrome docshells. Throws if set to false with
+   * top level chrome docshell.
+   */
+  attribute boolean windowDraggingAllowed;
+
+  /**
+   * Sets/gets the current scroll restoration mode.
+   * @see https://html.spec.whatwg.org/#dom-history-scroll-restoration
+   */
+  attribute boolean currentScrollRestorationIsManual;
+
+  /**
+   * Setter and getter for the origin attributes living on this docshell.
+   */
+  [implicit_jscontext]
+  jsval getOriginAttributes();
+
+  [implicit_jscontext]
+  void setOriginAttributes(in jsval aAttrs);
+
+  /**
+   * The editing session for this docshell.
+   */
+  readonly attribute nsIEditingSession editingSession;
+
+  /**
+   * The browser child for this docshell.
+   */
+  [binaryname(ScriptableBrowserChild)] readonly attribute nsIBrowserChild browserChild;
+  [noscript,notxpcom,nostdcall] BrowserChildRef GetBrowserChild();
+
+  [noscript,nostdcall,notxpcom] nsCommandManager GetCommandManager();
+
+  cenum MetaViewportOverride: 8 {
+    /**
+     * Override platform/pref default behaviour and force-disable support for
+     * <meta name="viewport">.
+     */
+    META_VIEWPORT_OVERRIDE_DISABLED = 0,
+    /**
+     * Override platform/pref default behaviour and force-enable support for
+     * <meta name="viewport">.
+     */
+    META_VIEWPORT_OVERRIDE_ENABLED = 1,
+    /**
+     * Don't override the platform/pref default behaviour for support for
+     * <meta name="viewport">.
+     */
+    META_VIEWPORT_OVERRIDE_NONE = 2,
+  };
+
+  /**
+   * This allows chrome to override the default choice of whether the
+   * <meta name="viewport"> tag is respected in a specific docshell.
+   * Possible values are listed above.
+   */
+  [infallible, setter_can_run_script] attribute nsIDocShell_MetaViewportOverride metaViewportOverride;
+
+  /**
+   * Attribute that determines whether tracking protection is enabled.
+   */
+  attribute boolean useTrackingProtection;
+
+ /**
+  * Fire a dummy location change event asynchronously.
+  */
+  [noscript] void dispatchLocationChangeEvent();
+
+
+  /**
+   * Start delayed autoplay media which are in the current document.
+   */
+  [noscript] void startDelayedAutoplayMediaComponents();
+
+  /**
+   * Take ownership of the ClientSource representing an initial about:blank
+   * document that was never needed.  As an optimization we avoid creating
+   * this document if no code calls GetDocument(), but we still need a
+   * ClientSource object to represent the about:blank window.  This may return
+   * nullptr; for example if the docshell has created a real window and document
+   * already.
+   */
+  [noscript, nostdcall, notxpcom]
+  UniqueClientSource TakeInitialClientSource();
+
+  void setColorMatrix(in Array<float> aMatrix);
+
+  /**
+   * Returns true if the current load is a forced reload,
+   * e.g. started by holding shift whilst triggering reload.
+   */
+  readonly attribute bool isForceReloading;
+
+  Array<float> getColorMatrix();
+
+%{C++
+  /**
+   * These methods call nsDocShell::GetHTMLEditorInternal() and
+   * nsDocShell::SetHTMLEditorInternal() with static_cast.
+   */
+  mozilla::HTMLEditor* GetHTMLEditor();
+  nsresult SetHTMLEditor(mozilla::HTMLEditor* aHTMLEditor);
+%}
+
+  /**
+   * The message manager for this docshell.  This does not throw, but
+   * can return null if the docshell has no message manager.
+   */
+  [infallible] readonly attribute ContentFrameMessageManager messageManager;
+
+   /**
+   * This returns a Promise which resolves to a boolean. True when the
+   * document has Tracking Content that has been blocked from loading, false
+   * otherwise.
+   */
+  Promise getHasTrackingContentBlocked();
+
+  /**
+   * Return whether this docshell is "attempting to navigate" in the
+   * sense that's relevant to document.open.
+   */
+  [notxpcom, nostdcall] readonly attribute boolean isAttemptingToNavigate;
+
+  /*
+   * Whether or not this docshell is executing a nsIWebNavigation navigation
+   * method.
+   *
+   * This will be true when the following methods are executing:
+   *   nsIWebNavigation.binaryLoadURI
+   *   nsIWebNavigation.goBack
+   *   nsIWebNavigation.goForward
+   *   nsIWebNavigation.gotoIndex
+   *   nsIWebNavigation.loadURI
+   */
+  [infallible] readonly attribute boolean isNavigating;
+
+  /**
+   * @see nsISHEntry synchronizeLayoutHistoryState().
+   */
+  void synchronizeLayoutHistoryState();
+
+  /**
+   * This attempts to save any applicable layout history state (like
+   * scroll position) in the nsISHEntry. This is normally done
+   * automatically when transitioning from page to page in the
+   * same process. We expose this function to support transitioning
+   * from page to page across processes as a workaround for bug 1630234
+   * until session history state is moved into the parent process.
+   */
+  void persistLayoutHistoryState();
+};
diff --git a/docshell/base/nsIDocShellTreeItem.idl b/docshell/base/nsIDocShellTreeItem.idl
new file mode 100644
index 0000000000..a80373832f
--- /dev/null
+++ b/docshell/base/nsIDocShellTreeItem.idl
@@ -0,0 +1,171 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface mozIDOMWindowProxy;
+interface nsIDocShellTreeOwner;
+interface nsPIDOMWindowOuter;
+
+webidl Document;
+webidl BrowsingContext;
+
+/**
+ * The nsIDocShellTreeItem supplies the methods that are required of any item
+ * that wishes to be able to live within the docshell tree either as a middle
+ * node or a leaf.
+ */
+
+[scriptable, builtinclass, uuid(9b7c586f-9214-480c-a2c4-49b526fff1a6)]
+interface nsIDocShellTreeItem : nsISupports
+{
+  /*
+  name of the DocShellTreeItem
+  */
+  attribute AString name;
+
+  /**
+   * Compares the provided name against the item's name and
+   * returns the appropriate result.
+   *
+   * @return <CODE>PR_TRUE</CODE> if names match;
+   *         <CODE>PR_FALSE</CODE> otherwise.
+   */
+  boolean nameEquals(in AString name);
+
+  /*
+  Definitions for the item types.
+  */
+  const long typeChrome=0;            // typeChrome must equal 0
+  const long typeContent=1;           // typeContent must equal 1
+  const long typeContentWrapper=2;    // typeContentWrapper must equal 2
+  const long typeChromeWrapper=3;     // typeChromeWrapper must equal 3
+
+  const long typeAll=0x7FFFFFFF;
+
+  /*
+  The type this item is.
+  */
+  readonly attribute long itemType;
+  [noscript,notxpcom,nostdcall] long ItemType();
+
+  /*
+  Parent DocShell.
+
+  @deprecated: Use `BrowsingContext::GetParent()` instead.
+  (NOTE: `BrowsingContext::GetParent()` will not cross isolation boundaries)
+  */
+  [binaryname(InProcessParent)]
+  readonly attribute nsIDocShellTreeItem parent;
+
+  /*
+  This getter returns the same thing parent does however if the parent
+  is of a different itemType, or if the parent is an <iframe mozbrowser>.
+  It will instead return nullptr.  This call is a convience function for
+  Ithose wishing to not cross the boundaries at which item types change.
+
+  @deprecated: Use `BrowsingContext::GetParent()` instead.
+  */
+  [binaryname(InProcessSameTypeParent)]
+  readonly attribute nsIDocShellTreeItem sameTypeParent;
+
+  /*
+  Returns the root DocShellTreeItem.  This is a convience equivalent to
+  getting the parent and its parent until there isn't a parent.
+
+  @deprecated: Use `BrowsingContext::Top()` instead.
+  (NOTE: `BrowsingContext::Top()` will not cross isolation boundaries)
+  */
+  [binaryname(InProcessRootTreeItem)]
+  readonly attribute nsIDocShellTreeItem rootTreeItem;
+
+  /*
+  Returns the root DocShellTreeItem of the same type.  This is a convience
+  equivalent to getting the parent of the same type and its parent until
+  there isn't a parent.
+
+  @deprecated: Use `BrowsingContext::Top()` instead.
+  */
+  [binaryname(InProcessSameTypeRootTreeItem)]
+  readonly attribute nsIDocShellTreeItem sameTypeRootTreeItem;
+
+  /*
+  The owner of the DocShell Tree.  This interface will be called upon when
+  the docshell has things it needs to tell to the owner of the docshell.
+  Note that docShell tree ownership does not cross tree types.  Meaning
+  setting ownership on a chrome tree does not set ownership on the content
+  sub-trees.  A given tree's boundaries are identified by the type changes.
+  Trees of different types may be connected, but should not be traversed
+  for things such as ownership.
+
+  Note implementers of this interface should NOT effect the lifetime of the
+  parent DocShell by holding this reference as it creates a cycle.  Owners
+  when releasing this interface should set the treeOwner to nullptr.
+  Implementers of this interface are guaranteed that when treeOwner is
+  set that the poitner is valid without having to addref.
+
+  Further note however when others try to get the interface it should be
+  addref'd before handing it to them.
+  */
+  readonly attribute nsIDocShellTreeOwner treeOwner;
+  [noscript] void setTreeOwner(in nsIDocShellTreeOwner treeOwner);
+
+  /*
+  The current number of DocShells which are immediate children of the
+  this object.
+
+
+  @deprecated: Prefer using `BrowsingContext::Children()`, as this count will
+  not include out-of-process iframes.
+  */
+  [binaryname(InProcessChildCount), infallible]
+  readonly attribute long childCount;
+
+  /*
+  Add a new child DocShellTreeItem.  Adds to the end of the list.
+  Note that this does NOT take a reference to the child.  The child stays
+  alive only as long as it's referenced from outside the docshell tree.
+
+  @throws NS_ERROR_ILLEGAL_VALUE if child corresponds to the same
+          object as this treenode or an ancestor of this treenode
+  @throws NS_ERROR_UNEXPECTED if this node is a leaf in the tree.
+  */
+  [noscript] void addChild(in nsIDocShellTreeItem child);
+
+  /*
+  Removes a child DocShellTreeItem.
+
+  @throws NS_ERROR_UNEXPECTED if this node is a leaf in the tree.
+  */
+  [noscript] void removeChild(in nsIDocShellTreeItem child);
+
+  /**
+   * Return the child at the index requested.  This is 0-based.
+   *
+   * @deprecated: Prefer using `BrowsingContext::Children()`, as this will not
+   * include out-of-process iframes.
+   *
+   * @throws NS_ERROR_UNEXPECTED if the index is out of range
+   */
+  [binaryname(GetInProcessChildAt)]
+  nsIDocShellTreeItem getChildAt(in long index);
+
+  /**
+   * BrowsingContext associated with the DocShell.
+   */
+  [binaryname(BrowsingContextXPCOM)]
+  readonly attribute BrowsingContext browsingContext;
+
+  [noscript,notxpcom,nostdcall] BrowsingContext getBrowsingContext();
+
+  /**
+   * Returns the DOM outer window for the content viewer.
+   */
+  readonly attribute mozIDOMWindowProxy domWindow;
+
+  [noscript,nostdcall,notxpcom] Document getDocument();
+  [noscript,nostdcall,notxpcom] nsPIDOMWindowOuter getWindow();
+};
diff --git a/docshell/base/nsIDocShellTreeOwner.idl b/docshell/base/nsIDocShellTreeOwner.idl
new file mode 100644
index 0000000000..db6faa59c9
--- /dev/null
+++ b/docshell/base/nsIDocShellTreeOwner.idl
@@ -0,0 +1,113 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * The nsIDocShellTreeOwner
+ */
+
+interface nsIDocShellTreeItem;
+interface nsIRemoteTab;
+webidl BrowsingContext;
+
+[scriptable, uuid(0e3dc4b1-4cea-4a37-af71-79f0afd07574)]
+interface nsIDocShellTreeOwner : nsISupports
+{
+  /**
+   * Called when a content shell is added to the docshell tree.  This is
+   * _only_ called for "root" content shells (that is, ones whose parent is a
+   * chrome shell).
+   *
+   * @param aContentShell the shell being added.
+   * @param aPrimary whether the shell is primary.
+   */
+  void contentShellAdded(in nsIDocShellTreeItem aContentShell,
+                         in boolean aPrimary);
+
+  /**
+   * Called when a content shell is removed from the docshell tree.  This is
+   * _only_ called for "root" content shells (that is, ones whose parent is a
+   * chrome shell).  Note that if aContentShell was never added,
+   * contentShellRemoved should just do nothing.
+   *
+   * @param aContentShell the shell being removed.
+   */
+  void contentShellRemoved(in nsIDocShellTreeItem aContentShell);
+
+  /*
+  Returns the Primary Content Shell
+  */
+  readonly attribute nsIDocShellTreeItem primaryContentShell;
+
+  void remoteTabAdded(in nsIRemoteTab aTab, in boolean aPrimary);
+  void remoteTabRemoved(in nsIRemoteTab aTab);
+
+  /*
+  In multiprocess case we may not have primaryContentShell but
+  primaryRemoteTab.
+   */
+  readonly attribute nsIRemoteTab primaryRemoteTab;
+
+  /*
+  Get the BrowsingContext associated with either the primary content shell or
+  primary remote tab, depending on which is available.
+  */
+  readonly attribute BrowsingContext primaryContentBrowsingContext;
+
+  /*
+  Tells the tree owner to size its window or parent window in such a way
+  that the shell passed along will be the size specified.
+  */
+  [can_run_script]
+  void sizeShellTo(in nsIDocShellTreeItem shell, in long cx, in long cy);
+
+  /*
+  Gets the size of the primary content area in device pixels. This should work
+  for both in-process and out-of-process content areas.
+  */
+  void getPrimaryContentSize(out long width, out long height);
+  /*
+  Sets the size of the primary content area in device pixels. This should work
+  for both in-process and out-of-process content areas.
+  */
+  void setPrimaryContentSize(in long width, in long height);
+
+  /*
+  Gets the size of the root docshell in device pixels.
+  */
+  void getRootShellSize(out long width, out long height);
+  /*
+  Sets the size of the root docshell in device pixels.
+  */
+  void setRootShellSize(in long width, in long height);
+
+  /*
+  Sets the persistence of different attributes of the window.
+  */
+  void setPersistence(in boolean aPersistPosition,
+                          in boolean aPersistSize,
+                          in boolean aPersistSizeMode);
+
+  /*
+  Gets the current persistence states of the window.
+  */
+  void getPersistence(out boolean aPersistPosition,
+                          out boolean aPersistSize,
+                          out boolean aPersistSizeMode);
+
+  /*
+  Gets the number of tabs currently open in our window, assuming
+  this tree owner has such a concept.
+  */
+  readonly attribute unsigned long tabCount;
+
+  /*
+  Returns true if there is a primary content shell or a primary
+  remote tab.
+  */
+  readonly attribute bool hasPrimaryContent;
+};
diff --git a/docshell/base/nsIDocumentLoaderFactory.idl b/docshell/base/nsIDocumentLoaderFactory.idl
new file mode 100644
index 0000000000..e3df2b2241
--- /dev/null
+++ b/docshell/base/nsIDocumentLoaderFactory.idl
@@ -0,0 +1,39 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIChannel;
+interface nsIDocumentViewer;
+interface nsIStreamListener;
+interface nsIDocShell;
+interface nsILoadGroup;
+interface nsIPrincipal;
+
+webidl Document;
+
+/**
+ * To get a component that implements nsIDocumentLoaderFactory
+ * for a given mimetype, use nsICategoryManager to find an entry
+ * with the mimetype as its name in the category "Gecko-Content-Viewers".
+ * The value of the entry is the contractid of the component.
+ * The component is a service, so use GetService, not CreateInstance to get it.
+ */
+
+[scriptable, uuid(e795239e-9d3c-47c4-b063-9e600fb3b287)]
+interface nsIDocumentLoaderFactory : nsISupports {
+    nsIDocumentViewer createInstance(in string aCommand,
+                              in nsIChannel aChannel,
+                              in nsILoadGroup aLoadGroup,
+                              in ACString aContentType,
+                              in nsIDocShell aContainer,
+                              in nsISupports aExtraInfo,
+                              out nsIStreamListener aDocListenerResult);
+
+    nsIDocumentViewer createInstanceForDocument(in nsISupports aContainer,
+                                         in Document aDocument,
+                                         in string aCommand);
+};
diff --git a/docshell/base/nsIDocumentViewer.idl b/docshell/base/nsIDocumentViewer.idl
new file mode 100644
index 0000000000..afbbdfc464
--- /dev/null
+++ b/docshell/base/nsIDocumentViewer.idl
@@ -0,0 +1,318 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIDocShell;
+interface nsISHEntry;
+interface nsIPrintSettings;
+webidl Document;
+webidl Node;
+
+%{ C++
+#include "mozilla/Maybe.h"
+#include "nsTArray.h"
+#include "nsRect.h"
+#include "Units.h"
+
+class nsIWidget;
+class nsPresContext;
+class nsView;
+class nsDOMNavigationTiming;
+namespace mozilla {
+class Encoding;
+class PresShell;
+namespace dom {
+class WindowGlobalChild;
+} // namespace dom
+namespace layout {
+class RemotePrintJobChild;
+} // namespace layout
+} // namespace mozilla
+%}
+
+[ptr] native nsIWidgetPtr(nsIWidget);
+[ref] native nsIntRectRef(nsIntRect);
+[ptr] native nsPresContextPtr(nsPresContext);
+[ptr] native nsViewPtr(nsView);
+[ptr] native nsDOMNavigationTimingPtr(nsDOMNavigationTiming);
+[ptr] native Encoding(const mozilla::Encoding);
+[ptr] native PresShellPtr(mozilla::PresShell);
+[ptr] native RemotePrintJobChildPtr(mozilla::layout::RemotePrintJobChild);
+[ptr] native WindowGlobalChildPtr(mozilla::dom::WindowGlobalChild);
+
+[scriptable, builtinclass, uuid(48118355-e9a5-4452-ab18-59cc426fb817)]
+interface nsIDocumentViewer : nsISupports
+{
+  [noscript] void init(in nsIWidgetPtr aParentWidget,
+                       [const] in nsIntRectRef aBounds,
+                       in WindowGlobalChildPtr aWindowActor);
+
+  attribute nsIDocShell container;
+
+  [noscript,notxpcom,nostdcall] void loadStart(in Document aDoc);
+  [can_run_script] void loadComplete(in nsresult aStatus);
+  [notxpcom,nostdcall] readonly attribute boolean loadCompleted;
+
+  [notxpcom,nostdcall] readonly attribute boolean isStopped;
+
+   /**
+   * aAction is passed to PermitUnload to indicate what action to take
+   * if a beforeunload handler wants to prompt the user.
+   *
+   * ePrompt: Prompt and return the user's choice (default).
+   * eDontPromptAndDontUnload: Don't prompt and return false (unload not permitted)
+   *                           if the document (or its children) asks us to prompt.
+   * eDontPromptAndUnload: Don't prompt and return true (unload permitted) no matter what.
+   *
+   * NOTE: Keep this in sync with PermitUnloadAction in WindowGlobalActors.webidl.
+   */
+  cenum PermitUnloadAction : 8 {
+    ePrompt = 0,
+    eDontPromptAndDontUnload = 1,
+    eDontPromptAndUnload = 2
+  };
+
+  /**
+   * The result of dispatching a "beforeunload" event. If `eAllowNavigation`,
+   * no "beforeunload" listener requested to prevent the navigation, or its
+   * request was ignored. If `eRequestBlockNavigation`, a listener did request
+   * to block the navigation, and the user should be prompted.
+   */
+  cenum PermitUnloadResult : 8 {
+    eAllowNavigation = 0,
+    eRequestBlockNavigation = 1,
+  };
+
+  /**
+   * Overload PermitUnload method for C++ consumers with no aPermitUnloadFlags
+   * argument.
+   */
+  %{C++
+    nsresult PermitUnload(bool* canUnload) {
+      return PermitUnload(ePrompt, canUnload);
+    }
+  %}
+
+  /**
+   * Checks if the document wants to prevent unloading by firing beforeunload on
+   * the document.
+   * The result is returned.
+   */
+  boolean permitUnload([optional] in nsIDocumentViewer_PermitUnloadAction aAction);
+
+  /**
+   * Exposes whether we're blocked in a call to permitUnload.
+   */
+  readonly attribute boolean inPermitUnload;
+
+  /**
+   * Dispatches the "beforeunload" event and returns the result, as documented
+   * in the `PermitUnloadResult` enum.
+   */
+  [noscript,nostdcall,notxpcom] nsIDocumentViewer_PermitUnloadResult dispatchBeforeUnload();
+
+  /**
+   * Exposes whether we're in the process of firing the beforeunload event.
+   * In this case, the corresponding docshell will not allow navigation.
+   */
+  readonly attribute boolean beforeUnloadFiring;
+
+  [can_run_script] void pageHide(in boolean isUnload);
+
+  /**
+   * All users of a content viewer are responsible for calling both
+   * close() and destroy(), in that order.
+   *
+   * close() should be called when the load of a new page for the next
+   * content viewer begins, and destroy() should be called when the next
+   * content viewer replaces this one.
+   *
+   * |historyEntry| sets the session history entry for the content viewer.  If
+   * this is null, then Destroy() will be called on the document by close().
+   * If it is non-null, the document will not be destroyed, and the following
+   * actions will happen when destroy() is called (*):
+   *  - Sanitize() will be called on the viewer's document
+   *  - The content viewer will set the contentViewer property on the
+   *    history entry, and release its reference (ownership reversal).
+   *  - hide() will be called, and no further destruction will happen.
+   *
+   *  (*) unless the document is currently being printed, in which case
+   *      it will never be saved in session history.
+   *
+   */
+  void close(in nsISHEntry historyEntry);
+  void destroy();
+
+  void stop();
+
+  /**
+   * Returns the same thing as getDocument(), but for use from script
+   * only.  C++ consumers should use getDocument().
+   */
+  readonly attribute Document DOMDocument;
+
+  /**
+   * Returns DOMDocument without addrefing.
+   */
+  [noscript,notxpcom,nostdcall] Document getDocument();
+
+  /**
+   * Allows setting the document.
+   */
+  [noscript,nostdcall] void setDocument(in Document aDocument);
+
+  [noscript] void getBounds(in nsIntRectRef aBounds);
+  [noscript] void setBounds([const] in nsIntRectRef aBounds);
+  /**
+   * The 'aFlags' argument to setBoundsWithFlags is a set of these bits.
+   */
+  const unsigned long eDelayResize = 1;
+  [noscript] void setBoundsWithFlags([const] in nsIntRectRef aBounds,
+                                     in unsigned long aFlags);
+
+  /**
+   * The previous content viewer, which has been |close|d but not
+   * |destroy|ed.
+   */
+  [notxpcom,nostdcall] attribute nsIDocumentViewer previousViewer;
+
+  void move(in long aX, in long aY);
+
+  void show();
+  void hide();
+
+  attribute boolean sticky;
+
+  /**
+   * Attach the content viewer to its DOM window and docshell.
+   * @param aState A state object that might be useful in attaching the DOM
+   *               window.
+   * @param aSHEntry The history entry that the content viewer was stored in.
+   *                 The entry must have the docshells for all of the child
+   *                 documents stored in its child shell list.
+   */
+  void open(in nsISupports aState, in nsISHEntry aSHEntry);
+
+  /**
+   * Clears the current history entry.  This is used if we need to clear out
+   * the saved presentation state.
+   */
+  void clearHistoryEntry();
+
+  /**
+   * Change the layout to view the document with page layout (like print preview), but
+   * dynamic and editable (like Galley layout).
+   */
+  void setPageModeForTesting(in boolean aPageMode,
+                             in nsIPrintSettings aPrintSettings);
+
+  /**
+   * Sets the print settings for print / print-previewing a subdocument.
+   */
+  [can_run_script] void setPrintSettingsForSubdocument(in nsIPrintSettings aPrintSettings,
+                                                       in RemotePrintJobChildPtr aRemotePrintJob);
+
+  /**
+   * Get the history entry that this viewer will save itself into when
+   * destroyed.  Can return null
+   */
+  readonly attribute nsISHEntry historyEntry;
+
+  /**
+   * Indicates when we're in a state where content shouldn't be allowed to
+   * trigger a tab-modal prompt (as opposed to a window-modal prompt) because
+   * we're part way through some operation (eg beforeunload) that shouldn't be
+   * rentrant if the user closes the tab while the prompt is showing.
+   * See bug 613800.
+   */
+  readonly attribute boolean isTabModalPromptAllowed;
+
+  /**
+   * Returns whether this content viewer is in a hidden state.
+   *
+   * @note Only Gecko internal code should set the attribute!
+   */
+  attribute boolean isHidden;
+
+  // presShell can be null.
+  [notxpcom,nostdcall] readonly attribute PresShellPtr presShell;
+  // presContext can be null.
+  [notxpcom,nostdcall] readonly attribute nsPresContextPtr presContext;
+  // aDocument must not be null.
+  [noscript] void setDocumentInternal(in Document aDocument,
+                                      in boolean aForceReuseInnerWindow);
+  /**
+   * Find the view to use as the container view for MakeWindow. Returns
+   * null if this will be the root of a view manager hierarchy. In that
+   * case, if mParentWidget is null then this document should not even
+   * be displayed.
+   */
+  [noscript,notxpcom,nostdcall] nsViewPtr findContainerView();
+  /**
+   * Set collector for navigation timing data (load, unload events).
+   */
+  [noscript,notxpcom,nostdcall] void setNavigationTiming(in nsDOMNavigationTimingPtr aTiming);
+
+  /**
+   * The actual full zoom in effect, as modified by the device context.
+   * For a requested full zoom, the device context may choose a slightly
+   * different effectiveFullZoom to accomodate integer rounding of app units
+   * per dev pixel. This property returns the actual zoom amount in use,
+   * though it may not be good user experience to report that a requested zoom
+   * of 90% is actually 89.1%, for example. This value is provided primarily to
+   * support media queries of dppx values, because those queries are matched
+   * against the actual native device pixel ratio and the actual full zoom.
+   *
+   * You should only need this for testing.
+   */
+  readonly attribute float deviceFullZoomForTest;
+
+  /**
+   * Disable entire author style level (including HTML presentation hints),
+   * for this viewer but not any child viewers.
+   */
+  attribute boolean authorStyleDisabled;
+
+  /**
+   * Returns the preferred width and height of the content, constrained to the
+   * given maximum values. If either maxWidth or maxHeight is less than or
+   * equal to zero, that dimension is not constrained.
+   *
+   * If a pref width is provided, it is max'd with the min-content size.
+   *
+   * All input and output values are in CSS pixels.
+   */
+  void getContentSize(in long maxWidth,
+                      in long maxHeight,
+                      in long prefWidth,
+                      out long width,
+                      out long height);
+
+%{C++
+  mozilla::Maybe<mozilla::CSSIntSize> GetContentSize(int32_t aMaxWidth = 0, int32_t aMaxHeight = 0, int32_t aPrefWidth = 0) {
+    int32_t w = 0;
+    int32_t h = 0;
+    if (NS_SUCCEEDED(GetContentSize(aMaxWidth, aMaxHeight, aPrefWidth, &w, &h))) {
+      return mozilla::Some(mozilla::CSSIntSize(w, h));
+    }
+    return mozilla::Nothing();
+  }
+%}
+
+  [noscript, notxpcom] Encoding getReloadEncodingAndSource(out int32_t aSource);
+  [noscript, notxpcom] void setReloadEncodingAndSource(in Encoding aEncoding, in int32_t aSource);
+  [noscript, notxpcom] void forgetReloadEncoding();
+};
+
+%{C++
+namespace mozilla {
+namespace dom {
+
+using XPCOMPermitUnloadAction = nsIDocumentViewer::PermitUnloadAction;
+using PermitUnloadResult = nsIDocumentViewer::PermitUnloadResult;
+
+} // namespace dom
+} // namespace mozilla
+%}
diff --git a/docshell/base/nsIDocumentViewerEdit.idl b/docshell/base/nsIDocumentViewerEdit.idl
new file mode 100644
index 0000000000..10ec203df7
--- /dev/null
+++ b/docshell/base/nsIDocumentViewerEdit.idl
@@ -0,0 +1,36 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+webidl Node;
+
+[scriptable, uuid(e39a0c2a-5b31-4d57-a971-66ba07fab614)]
+interface nsIDocumentViewerEdit : nsISupports
+{
+  void clearSelection();
+  void selectAll();
+
+  void copySelection();
+  readonly attribute boolean copyable;
+
+  void copyLinkLocation();
+  readonly attribute boolean inLink;
+
+  const long COPY_IMAGE_TEXT = 0x0001;
+  const long COPY_IMAGE_HTML = 0x0002;
+  const long COPY_IMAGE_DATA = 0x0004;
+  const long COPY_IMAGE_ALL = -1;
+  void copyImage(in long aCopyFlags);
+  readonly attribute boolean inImage;
+
+  AString getContents(in string aMimeType, in boolean aSelectionOnly);
+  readonly attribute boolean canGetContents;
+
+  // Set the node that will be the subject of the editing commands above.
+  // Usually this will be the node that was context-clicked.
+  void setCommandNode(in Node aNode);
+};
diff --git a/docshell/base/nsILoadContext.idl b/docshell/base/nsILoadContext.idl
new file mode 100644
index 0000000000..af71b96b34
--- /dev/null
+++ b/docshell/base/nsILoadContext.idl
@@ -0,0 +1,148 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: ft=cpp tw=78 sw=2 et ts=2 sts=2 cin
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface mozIDOMWindowProxy;
+
+webidl Element;
+
+[ref] native OriginAttributes(mozilla::OriginAttributes);
+
+%{C++
+#ifdef MOZILLA_INTERNAL_API
+namespace mozilla {
+class OriginAttributes;
+}
+#endif
+%}
+
+/**
+ * An nsILoadContext represents the context of a load.  This interface
+ * can be queried for various information about where the load is
+ * happening.
+ */
+[builtinclass, scriptable, uuid(2813a7a3-d084-4d00-acd0-f76620315c02)]
+interface nsILoadContext : nsISupports
+{
+  /**
+   * associatedWindow is the window with which the load is associated, if any.
+   * Note that the load may be triggered by a document which is different from
+   * the document in associatedWindow, and in fact the source of the load need
+   * not be same-origin with the document in associatedWindow.  This attribute
+   * may be null if there is no associated window.
+   */
+  readonly attribute mozIDOMWindowProxy associatedWindow;
+
+  /**
+   * topWindow is the top window which is of same type as associatedWindow.
+   * This is equivalent to associatedWindow.top, but is provided here as a
+   * convenience.  All the same caveats as associatedWindow of apply, of
+   * course.  This attribute may be null if there is no associated window.
+   */
+  readonly attribute mozIDOMWindowProxy topWindow;
+
+  /**
+   * topFrameElement is the <iframe>, <frame>, or <browser> element which
+   * contains the topWindow with which the load is associated.
+   *
+   * Note that we may have a topFrameElement even when we don't have an
+   * associatedWindow, if the topFrameElement's content lives out of process.
+   * topFrameElement is available in single-process and multiprocess contexts.
+   * Note that topFrameElement may be in chrome even when the nsILoadContext is
+   * associated with content.
+   */
+  readonly attribute Element topFrameElement;
+
+  /**
+   * True if the load context is content (as opposed to chrome).  This is
+   * determined based on the type of window the load is performed in, NOT based
+   * on any URIs that might be around.
+   */
+  readonly attribute boolean isContent;
+
+  /*
+   * Attribute that determines if private browsing should be used. May not be
+   * changed after a document has been loaded in this context.
+   */
+  attribute boolean usePrivateBrowsing;
+
+  /**
+   * Attribute that determines if remote (out-of-process) tabs should be used.
+   */
+  readonly attribute boolean useRemoteTabs;
+
+  /**
+   * Determines if out-of-process iframes should be used.
+   */
+  readonly attribute boolean useRemoteSubframes;
+
+  /*
+   * Attribute that determines if tracking protection should be used. May not be
+   * changed after a document has been loaded in this context.
+   */
+  attribute boolean useTrackingProtection;
+
+%{C++
+  /**
+   * De-XPCOMed getter to make call-sites cleaner.
+   */
+  bool UsePrivateBrowsing()
+  {
+    bool usingPB = false;
+    GetUsePrivateBrowsing(&usingPB);
+    return usingPB;
+  }
+
+  bool UseRemoteTabs()
+  {
+    bool usingRT = false;
+    GetUseRemoteTabs(&usingRT);
+    return usingRT;
+  }
+
+  bool UseRemoteSubframes()
+  {
+    bool usingRSF = false;
+    GetUseRemoteSubframes(&usingRSF);
+    return usingRSF;
+  }
+
+  bool UseTrackingProtection()
+  {
+    bool usingTP = false;
+    GetUseTrackingProtection(&usingTP);
+    return usingTP;
+  }
+%}
+
+  /**
+   * Set the private browsing state of the load context, meant to be used internally.
+   */
+  [noscript] void SetPrivateBrowsing(in boolean aInPrivateBrowsing);
+
+  /**
+   * Set the remote tabs state of the load context, meant to be used internally.
+   */
+  [noscript] void SetRemoteTabs(in boolean aUseRemoteTabs);
+
+  /**
+   * Set the remote subframes bit of this load context. Exclusively meant to be used internally.
+   */
+  [noscript] void SetRemoteSubframes(in boolean aUseRemoteSubframes);
+
+  /**
+   * A dictionary of the non-default origin attributes associated with this
+   * nsILoadContext.
+   */
+  [binaryname(ScriptableOriginAttributes), implicit_jscontext]
+  readonly attribute jsval originAttributes;
+
+  /**
+   * The C++ getter for origin attributes.
+   */
+  [noscript, notxpcom] void GetOriginAttributes(out OriginAttributes aAttrs);
+};
diff --git a/docshell/base/nsILoadURIDelegate.idl b/docshell/base/nsILoadURIDelegate.idl
new file mode 100644
index 0000000000..eb5d4cbaf5
--- /dev/null
+++ b/docshell/base/nsILoadURIDelegate.idl
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ */
+
+#include "nsISupports.idl"
+
+interface nsIURI;
+interface nsIPrincipal;
+
+/**
+ * The nsILoadURIDelegate interface.
+ * Used for delegating URI loads to GeckoView's application, e.g., Custom Tabs
+ * or Progressive Web Apps.
+ */
+[scriptable, uuid(78e42d37-a34c-4d96-b901-25385669aba4)]
+interface nsILoadURIDelegate : nsISupports
+{
+  /**
+   * Delegates page load error handling. This may be called for either top-level
+   * loads or subframes.
+   *
+   * @param aURI The URI that failed to load.
+   * @param aError The error code.
+   * @param aErrorModule The error module code.
+
+   * Returns an error page URL to load, or null to show the default error page.
+   * No error page is shown at all if an error is thrown.
+   */
+  nsIURI
+  handleLoadError(in nsIURI aURI, in nsresult aError, in short aErrorModule);
+};
diff --git a/docshell/base/nsIPrivacyTransitionObserver.idl b/docshell/base/nsIPrivacyTransitionObserver.idl
new file mode 100644
index 0000000000..c85d468d33
--- /dev/null
+++ b/docshell/base/nsIPrivacyTransitionObserver.idl
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+[scriptable, function, uuid(b4b1449d-0ef0-47f5-b62e-adc57fd49702)]
+interface nsIPrivacyTransitionObserver : nsISupports
+{
+  void privateModeChanged(in bool enabled);
+};
diff --git a/docshell/base/nsIReflowObserver.idl b/docshell/base/nsIReflowObserver.idl
new file mode 100644
index 0000000000..fb602e2603
--- /dev/null
+++ b/docshell/base/nsIReflowObserver.idl
@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "domstubs.idl"
+
+[scriptable, uuid(832e692c-c4a6-11e2-8fd1-dce678957a39)]
+interface nsIReflowObserver : nsISupports
+{
+  /**
+   * Called when an uninterruptible reflow has occurred.
+   *
+   * @param start timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   * @param end   timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   */
+  void reflow(in DOMHighResTimeStamp start,
+              in DOMHighResTimeStamp end);
+
+  /**
+   * Called when an interruptible reflow has occurred.
+   *
+   * @param start timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   * @param end   timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   */
+  void reflowInterruptible(in DOMHighResTimeStamp start,
+                           in DOMHighResTimeStamp end);
+};
diff --git a/docshell/base/nsIRefreshURI.idl b/docshell/base/nsIRefreshURI.idl
new file mode 100644
index 0000000000..a4a578a344
--- /dev/null
+++ b/docshell/base/nsIRefreshURI.idl
@@ -0,0 +1,52 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIChannel;
+interface nsIPrincipal;
+interface nsIURI;
+
+[scriptable, uuid(a5e61a3c-51bd-45be-ac0c-e87b71860656)]
+interface nsIRefreshURI : nsISupports {
+    /**
+      * Load a uri after waiting for aMillis milliseconds (as a result of a
+      * meta refresh). If the docshell is busy loading a page currently, the
+      * refresh request will be queued and executed when the current load
+      * finishes.
+      *
+      * @param aUri The uri to refresh.
+      * @param aPrincipal The triggeringPrincipal for the refresh load
+      *   May be null, in which case the principal of current document will be
+      *   applied.
+      * @param aMillis The number of milliseconds to wait.
+      */
+    void refreshURI(in nsIURI aURI, in nsIPrincipal aPrincipal,
+                    in unsigned long aMillis);
+
+    /**
+      * Loads a URI immediately as if it were a meta refresh.
+      *
+      * @param aURI The URI to refresh.
+      * @param aPrincipal The triggeringPrincipal for the refresh load
+      *   May be null, in which case the principal of current document will be
+      *   applied.
+      * @param aMillis The number of milliseconds by which this refresh would
+      *                be delayed if it were not being forced.
+      */
+    void forceRefreshURI(in nsIURI aURI, in nsIPrincipal aPrincipal,
+                         in unsigned long aMillis);
+
+    /**
+      * Cancels all timer loads.
+      */
+    void cancelRefreshURITimers();
+
+   /**
+     * True when there are pending refreshes, false otherwise.
+     */
+   readonly attribute boolean refreshPending;
+};
diff --git a/docshell/base/nsIScrollObserver.h b/docshell/base/nsIScrollObserver.h
new file mode 100644
index 0000000000..9ff89002f0
--- /dev/null
+++ b/docshell/base/nsIScrollObserver.h
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsIScrollObserver_h___
+#define nsIScrollObserver_h___
+
+#include "nsISupports.h"
+#include "Units.h"
+
+// Must be kept in sync with xpcom/rust/xpcom/src/interfaces/nonidl.rs
+#define NS_ISCROLLOBSERVER_IID                       \
+  {                                                  \
+    0xaa5026eb, 0x2f88, 0x4026, {                    \
+      0xa4, 0x6b, 0xf4, 0x59, 0x6b, 0x4e, 0xdf, 0x00 \
+    }                                                \
+  }
+
+class nsIScrollObserver : public nsISupports {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ISCROLLOBSERVER_IID)
+
+  /**
+   * Called when the scroll position of some element has changed.
+   */
+  virtual void ScrollPositionChanged() = 0;
+
+  /**
+   * Called when an async panning/zooming transform has started being applied
+   * and passed the scroll offset
+   */
+  MOZ_CAN_RUN_SCRIPT virtual void AsyncPanZoomStarted(){};
+
+  /**
+   * Called when an async panning/zooming transform is no longer applied
+   * and passed the scroll offset
+   */
+  MOZ_CAN_RUN_SCRIPT virtual void AsyncPanZoomStopped(){};
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsIScrollObserver, NS_ISCROLLOBSERVER_IID)
+
+#endif /* nsIScrollObserver_h___ */
diff --git a/docshell/base/nsITooltipListener.idl b/docshell/base/nsITooltipListener.idl
new file mode 100644
index 0000000000..0498aca57d
--- /dev/null
+++ b/docshell/base/nsITooltipListener.idl
@@ -0,0 +1,44 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * An optional interface for embedding clients wishing to receive
+ * notifications for when a tooltip should be displayed or removed.
+ * The embedder implements this interface on the web browser chrome
+ * object associated with the window that notifications are required
+ * for.
+ *
+ * @see nsITooltipTextProvider
+ */
+[scriptable, uuid(44b78386-1dd2-11b2-9ad2-e4eee2ca1916)]
+interface nsITooltipListener : nsISupports
+{
+    /**
+     * Called when a tooltip should be displayed.
+     *
+     * @param aXCoords The tooltip left edge X coordinate.
+     * @param aYCoords The tooltip top edge Y coordinate.
+     * @param aTipText The text to display in the tooltip, typically obtained
+     *        from the TITLE attribute of the node (or containing parent)
+     *        over which the pointer has been positioned.
+     * @param aTipDir  The direction (ltr or rtl) in which to display the text
+     *
+     * @note
+     * Coordinates are specified in device pixels, relative to the top-left
+     * corner of the browser area.
+     *
+     * @return <code>NS_OK</code> if the tooltip was displayed.
+     */
+    void onShowTooltip(in long aXCoords, in long aYCoords, in AString aTipText,
+                       in AString aTipDir);
+
+    /**
+     * Called when the tooltip should be hidden, either because the pointer
+     * has moved or the tooltip has timed out.
+     */
+    void onHideTooltip();
+};
diff --git a/docshell/base/nsITooltipTextProvider.idl b/docshell/base/nsITooltipTextProvider.idl
new file mode 100644
index 0000000000..3afaddbe2a
--- /dev/null
+++ b/docshell/base/nsITooltipTextProvider.idl
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+webidl Node;
+
+/**
+ * An interface implemented by a tooltip text provider service. This
+ * service is called to discover what tooltip text is associated
+ * with the node that the pointer is positioned over.
+ *
+ * Embedders may implement and register their own tooltip text provider
+ * service if they wish to provide different tooltip text.
+ *
+ * The default service returns the text stored in the TITLE
+ * attribute of the node or a containing parent.
+ *
+ * @note
+ * The tooltip text provider service is registered with the contract
+ * defined in NS_TOOLTIPTEXTPROVIDER_CONTRACTID.
+ *
+ * @see nsITooltipListener
+ * @see nsIComponentManager
+ * @see Node
+ */
+[scriptable, uuid(b128a1e6-44f3-4331-8fbe-5af360ff21ee)]
+interface nsITooltipTextProvider : nsISupports
+{
+    /**
+     * Called to obtain the tooltip text for a node.
+     *
+     * @arg aNode      The node to obtain the text from.
+     * @arg aText      The tooltip text.
+     * @arg aDirection The text direction (ltr or rtl) to use
+     *
+     * @return <CODE>PR_TRUE</CODE> if tooltip text is associated
+     *         with the node and was returned in the aText argument;
+     *         <CODE>PR_FALSE</CODE> otherwise.
+     */
+    boolean getNodeText(in Node aNode, out wstring aText, out wstring aDirection);
+};
diff --git a/docshell/base/nsIURIFixup.idl b/docshell/base/nsIURIFixup.idl
new file mode 100644
index 0000000000..2261c0cb40
--- /dev/null
+++ b/docshell/base/nsIURIFixup.idl
@@ -0,0 +1,204 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIURI;
+interface nsIInputStream;
+interface nsIDNSListener;
+webidl BrowsingContext;
+
+/**
+ * Interface indicating what we found/corrected when fixing up a URI
+ */
+[scriptable, uuid(4819f183-b532-4932-ac09-b309cd853be7)]
+interface nsIURIFixupInfo : nsISupports
+{
+  /**
+   * Consumer that asked for fixed up URI.
+   */
+  attribute BrowsingContext consumer;
+
+  /**
+   * Our best guess as to what URI the consumer will want. Might
+   * be null if we couldn't salvage anything (for instance, because
+   * the input was invalid as a URI and FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP
+   * was not passed)
+   */
+  attribute nsIURI preferredURI;
+
+  /**
+   * The fixed-up original input, *never* using a keyword search.
+   * (might be null if the original input was not recoverable as
+   * a URL, e.g. "foo bar"!)
+   */
+  attribute nsIURI fixedURI;
+
+  /**
+   * The name of the keyword search provider used to provide a keyword search;
+   * empty string if no keyword search was done.
+   */
+  attribute AString keywordProviderName;
+
+  /**
+   * The keyword as used for the search (post trimming etc.)
+   * empty string if no keyword search was done.
+   */
+  attribute AString keywordAsSent;
+
+  /**
+   * Whether there was no protocol at all and we had to add one in the first place.
+   */
+  attribute boolean wasSchemelessInput;
+
+  /**
+   * Whether we changed the protocol instead of using one from the input as-is.
+   */
+  attribute boolean fixupChangedProtocol;
+
+  /**
+   * Whether we created an alternative URI. We might have added a prefix and/or
+   * suffix, the contents of which are controlled by the
+   * browser.fixup.alternate.prefix and .suffix prefs, with the defaults being
+   * "www." and ".com", respectively.
+   */
+  attribute boolean fixupCreatedAlternateURI;
+
+  /**
+   * The original input
+   */
+  attribute AUTF8String originalInput;
+
+  /**
+   * The POST data to submit with the returned URI (see nsISearchSubmission).
+   */
+  attribute nsIInputStream postData;
+};
+
+
+/**
+ * Interface implemented by objects capable of fixing up strings into URIs
+ */
+[scriptable, uuid(1da7e9d4-620b-4949-849a-1cd6077b1b2d)]
+interface nsIURIFixup : nsISupports
+{
+    /** No fixup flags. */
+    const unsigned long FIXUP_FLAG_NONE = 0;
+
+    /**
+     * Allow the fixup to use a keyword lookup service to complete the URI.
+     * The fixup object implementer should honour this flag and only perform
+     * any lengthy keyword (or search) operation if it is set.
+     */
+    const unsigned long FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP = 1;
+
+    /**
+     * Tell the fixup to make an alternate URI from the input URI, for example
+     * to turn foo into www.foo.com.
+     */
+    const unsigned long FIXUP_FLAGS_MAKE_ALTERNATE_URI = 2;
+
+    /*
+     * Set when the fixup happens in a private context, the used search engine
+     * may differ in this case. Not all consumers care about this, because they
+     * may not want the url to be transformed in a search.
+     */
+    const unsigned long FIXUP_FLAG_PRIVATE_CONTEXT = 4;
+
+    /*
+     * Fix common scheme typos.
+     */
+    const unsigned long FIXUP_FLAG_FIX_SCHEME_TYPOS = 8;
+
+    /**
+     * Tries to converts the specified string into a URI, first attempting
+     * to correct any errors in the syntax or other vagaries.
+     * It returns information about what it corrected
+     * (e.g. whether we could rescue the URI or "just" generated a keyword
+     * search URI instead).
+     *
+     * @param aURIText    Candidate URI.
+     * @param aFixupFlags Flags that govern ways the URI may be fixed up.
+     *                    Defaults to FIXUP_FLAG_NONE.
+     */
+    nsIURIFixupInfo getFixupURIInfo(in AUTF8String aURIText,
+                                    [optional] in unsigned long aFixupFlags);
+
+    /**
+     * Convert load flags from nsIWebNavigation to URI fixup flags for use in
+     * getFixupURIInfo.
+     *
+     * @param aURIText       Candidate URI; used for determining whether to
+     *                       allow keyword lookups.
+     * @param aDocShellFlags Load flags from nsIDocShell to convert.
+     */
+    unsigned long webNavigationFlagsToFixupFlags(
+        in AUTF8String aURIText, in unsigned long aDocShellFlags);
+
+    /**
+     * Converts the specified keyword string into a URI.  Note that it's the
+     * caller's responsibility to check whether keywords are enabled and
+     * whether aKeyword is a sensible keyword.
+     *
+     * @param aKeyword  The keyword string to convert into a URI
+     * @param aIsPrivateContext Whether this is invoked from a private context.
+     */
+    nsIURIFixupInfo keywordToURI(in AUTF8String aKeyword,
+                                 [optional] in boolean aIsPrivateContext);
+
+    /**
+     * Given a uri-like string with a protocol, attempt to fix and convert it
+     * into an instance of nsIURIFixupInfo.
+     *
+     * Differently from getFixupURIInfo, this assumes the input string is an
+     * http/https uri, and can add a prefix and/or suffix to its hostname.
+     *
+     * The scheme will be changed to the scheme defined in
+     * "browser.fixup.alternate.protocol", which is by default, https.
+     *
+     * If the prefix and suffix of the host are missing, it will add them to
+     * the host using the preferences "browser.fixup.alternate.prefix" and
+     * "browser.fixup.alternate.suffix" as references.
+     *
+     * If a hostname suffix is present, but the URI doesn't contain a prefix,
+     * it will add the prefix via "browser.fixup.alternate.prefix"
+     *
+     * @param aUriString The URI to fixup and convert.
+     * @returns nsIURIFixupInfo
+     *                   A nsIURIFixupInfo object with the property fixedURI
+     *                   which contains the modified URI.
+     * @throws NS_ERROR_FAILURE
+     *                   If aUriString is undefined, or the scheme is not
+     *                   http/https.
+     */
+    nsIURIFixupInfo forceHttpFixup(in AUTF8String aUriString);
+
+    /**
+     * With the host associated with the URI, use nsIDNSService to determine
+     * if an IP address can be found for this host. This method will ignore checking
+     * hosts that are IP addresses. If the host does not contain any periods, depending
+     * on the browser.urlbar.dnsResolveFullyQualifiedNames preference value, a period
+     * may be appended in order to make it a fully qualified domain name.
+     *
+     * @param aURI The URI to parse and pass into the DNS lookup.
+     * @param aListener The listener when the result from the lookup is available.
+     * @param aOriginAttributes The originAttributes to pass the DNS lookup.
+     * @throws NS_ERROR_FAILURE if aURI does not have a displayHost or asciiHost.
+     */
+    void checkHost(in nsIURI aURI,
+                    in nsIDNSListener aListener,
+                    [optional] in jsval aOriginAttributes);
+
+    /**
+     * Returns true if the specified domain is known and false otherwise.
+     * A known domain is relevant when we have a single word and can't be
+     * sure whether to treat the word as a host name or should instead be
+     * treated as a search term.
+     *
+     * @param aDomain A domain name to query.
+     */
+    bool isDomainKnown(in AUTF8String aDomain);
+};
diff --git a/docshell/base/nsIWebNavigation.idl b/docshell/base/nsIWebNavigation.idl
new file mode 100644
index 0000000000..1800e7312e
--- /dev/null
+++ b/docshell/base/nsIWebNavigation.idl
@@ -0,0 +1,415 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIInputStream;
+interface nsISHistory;
+interface nsIURI;
+interface nsIPrincipal;
+interface nsIChildSHistory;
+webidl Document;
+
+%{ C++
+#include "mozilla/dom/ChildSHistory.h"
+namespace mozilla {
+namespace dom {
+struct LoadURIOptions;
+} // namespace dom
+} // namespace mozilla
+%}
+
+[ref] native LoadURIOptionsRef(const mozilla::dom::LoadURIOptions);
+
+/**
+ * The nsIWebNavigation interface defines an interface for navigating the web.
+ * It provides methods and attributes to direct an object to navigate to a new
+ * location, stop or restart an in process load, or determine where the object
+ * has previously gone.
+ *
+ * Even though this is builtinclass, most of the interface is also implemented
+ * in RemoteWebNavigation, so if this interface changes, the implementation
+ * there may also need to change.
+ */
+[scriptable, builtinclass, uuid(3ade79d4-8cb9-4952-b18d-4f9b63ca0d31)]
+interface nsIWebNavigation : nsISupports
+{
+  /**
+   * Indicates if the object can go back.  If true this indicates that
+   * there is back session history available for navigation.
+   */
+  readonly attribute boolean canGoBack;
+
+  /**
+   * Indicates if the object can go forward.  If true this indicates that
+   * there is forward session history available for navigation
+   */
+  readonly attribute boolean canGoForward;
+
+  /**
+   * Tells the object to navigate to the previous session history item.  When a
+   * page is loaded from session history, all content is loaded from the cache
+   * (if available) and page state (such as form values and scroll position) is
+   * restored.
+   *
+   * @param {boolean} aRequireUserInteraction
+   *        Tells goBack to skip history items that did not record any user
+   *        interaction on their corresponding document while they were active.
+   *        This means in case of multiple entries mapping to the same document,
+   *        each entry has to have been flagged with user interaction separately.
+   *        If no items have user interaction, the function will fall back
+   *        to the first session history entry.
+   *
+   * @param {boolean} aUserActivation
+   *        Tells goBack that the call was triggered by a user action (e.g.:
+   *        The user clicked the back button).
+   *
+   * @throw NS_ERROR_UNEXPECTED
+   *        Indicates that the call was unexpected at this time, which implies
+   *        that canGoBack is false.
+   */
+  void goBack([optional] in boolean aRequireUserInteraction, [optional] in boolean aUserActivation);
+
+  /**
+   * Tells the object to navigate to the next session history item.  When a
+   * page is loaded from session history, all content is loaded from the cache
+   * (if available) and page state (such as form values and scroll position) is
+   * restored.
+   *
+   * @param {boolean} aRequireUserInteraction
+   *        Tells goForward to skip history items that did not record any user
+   *        interaction on their corresponding document while they were active.
+   *        This means in case of multiple entries mapping to the same document,
+   *        each entry has to have been flagged with user interaction separately.
+   *        If no items have user interaction, the function will fall back
+   *        to the latest session history entry.
+   *
+   * @param {boolean} aUserActivation
+   *        Tells goForward that the call was triggered by a user action (e.g.:
+   *        The user clicked the forward button).
+   *
+   * @throw NS_ERROR_UNEXPECTED
+   *        Indicates that the call was unexpected at this time, which implies
+   *        that canGoForward is false.
+   */
+  void goForward([optional] in boolean aRequireUserInteraction, [optional] in boolean aUserActivation);
+
+  /**
+   * Tells the object to navigate to the session history item at a given index.
+   *
+   * @param {boolean} aUserActivation
+   *        Tells goForward that the call was triggered by a user action (e.g.:
+   *        The user clicked the forward button).
+   *
+   * @throw NS_ERROR_UNEXPECTED
+   *        Indicates that the call was unexpected at this time, which implies
+   *        that session history entry at the given index does not exist.
+   */
+  void gotoIndex(in long index, [optional] in boolean aUserActivation);
+
+  /****************************************************************************
+   * The following flags may be bitwise combined to form the load flags
+   * parameter passed to either the loadURI or reload method.  Some of these
+   * flags are only applicable to loadURI.
+   */
+
+  /**
+   * This flags defines the range of bits that may be specified.  Flags
+   * outside this range may be used, but may not be passed to Reload().
+   */
+  const unsigned long LOAD_FLAGS_MASK            = 0xffff;
+
+  /**
+   * This is the default value for the load flags parameter.
+   */
+  const unsigned long LOAD_FLAGS_NONE            = 0x0000;
+
+  /**
+   * Flags 0x1, 0x2, 0x4, 0x8 are reserved for internal use by
+   * nsIWebNavigation implementations for now.
+   */
+
+  /**
+   * This flag specifies that the load should have the semantics of an HTML
+   * Meta-refresh tag (i.e., that the cache should be bypassed).  This flag
+   * is only applicable to loadURI.
+   * XXX the meaning of this flag is poorly defined.
+   * XXX no one uses this, so we should probably deprecate and remove it.
+   */
+  const unsigned long LOAD_FLAGS_IS_REFRESH      = 0x0010;
+
+  /**
+   * This flag specifies that the load should have the semantics of a link
+   * click.  This flag is only applicable to loadURI.
+   * XXX the meaning of this flag is poorly defined.
+   */
+  const unsigned long LOAD_FLAGS_IS_LINK         = 0x0020;
+
+  /**
+   * This flag specifies that history should not be updated.  This flag is only
+   * applicable to loadURI.
+   */
+  const unsigned long LOAD_FLAGS_BYPASS_HISTORY  = 0x0040;
+
+  /**
+   * This flag specifies that any existing history entry should be replaced.
+   * This flag is only applicable to loadURI.
+   */
+  const unsigned long LOAD_FLAGS_REPLACE_HISTORY = 0x0080;
+
+  /**
+   * This flag specifies that the local web cache should be bypassed, but an
+   * intermediate proxy cache could still be used to satisfy the load.
+   */
+  const unsigned long LOAD_FLAGS_BYPASS_CACHE    = 0x0100;
+
+  /**
+   * This flag specifies that any intermediate proxy caches should be bypassed
+   * (i.e., that the content should be loaded from the origin server).
+   */
+  const unsigned long LOAD_FLAGS_BYPASS_PROXY    = 0x0200;
+
+  /**
+   * This flag specifies that a reload was triggered as a result of detecting
+   * an incorrect character encoding while parsing a previously loaded
+   * document.
+   */
+  const unsigned long LOAD_FLAGS_CHARSET_CHANGE  = 0x0400;
+
+  /**
+   * If this flag is set, Stop() will be called before the load starts
+   * and will stop both content and network activity (the default is to
+   * only stop network activity).  Effectively, this passes the
+   * STOP_CONTENT flag to Stop(), in addition to the STOP_NETWORK flag.
+   */
+  const unsigned long LOAD_FLAGS_STOP_CONTENT    = 0x0800;
+
+  /**
+   * A hint this load was prompted by an external program: take care!
+   */
+  const unsigned long LOAD_FLAGS_FROM_EXTERNAL   = 0x1000;
+
+  /**
+   * This flag specifies that this is the first load in this object.
+   * Set with care, since setting incorrectly can cause us to assume that
+   * nothing was actually loaded in this object if the load ends up being
+   * handled by an external application.  This flag must not be passed to
+   * Reload.
+   */
+  const unsigned long LOAD_FLAGS_FIRST_LOAD = 0x4000;
+
+  /**
+   * This flag specifies that the load should not be subject to popup
+   * blocking checks.  This flag must not be passed to Reload.
+   */
+  const unsigned long LOAD_FLAGS_ALLOW_POPUPS = 0x8000;
+
+  /**
+   * This flag specifies that the URI classifier should not be checked for
+   * this load.  This flag must not be passed to Reload.
+   */
+  const unsigned long LOAD_FLAGS_BYPASS_CLASSIFIER = 0x10000;
+
+  /**
+   * Force relevant cookies to be sent with this load even if normally they
+   * wouldn't be.
+   */
+  const unsigned long LOAD_FLAGS_FORCE_ALLOW_COOKIES = 0x20000;
+
+  /**
+   * Prevent the owner principal from being inherited for this load.
+   */
+  const unsigned long LOAD_FLAGS_DISALLOW_INHERIT_PRINCIPAL = 0x40000;
+
+  /**
+   * Overwrite the returned error code with a specific result code
+   * when an error page is displayed.
+   */
+  const unsigned long LOAD_FLAGS_ERROR_LOAD_CHANGES_RV = 0x80000;
+
+  /**
+   * This flag specifies that the URI may be submitted to a third-party
+   * server for correction. This should only be applied to non-sensitive
+   * URIs entered by users.  This flag must not be passed to Reload.
+   */
+  const unsigned long LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP = 0x100000;
+
+  /**
+   * This flag specifies that common scheme typos should be corrected.
+   */
+  const unsigned long LOAD_FLAGS_FIXUP_SCHEME_TYPOS = 0x200000;
+
+  /**
+   * Allows a top-level data: navigation to occur. E.g. view-image
+   * is an explicit user action which should be allowed.
+   */
+  const unsigned long LOAD_FLAGS_FORCE_ALLOW_DATA_URI = 0x400000;
+
+  /**
+   * This load is the result of an HTTP redirect.
+   */
+  const unsigned long LOAD_FLAGS_IS_REDIRECT = 0x800000;
+
+  /**
+   * These flags force TRR modes 1 or 3 for the load.
+   */
+  const unsigned long LOAD_FLAGS_DISABLE_TRR = 0x1000000;
+  const unsigned long LOAD_FLAGS_FORCE_TRR = 0x2000000;
+
+  /**
+   * This load should bypass the LoadURIDelegate.loadUri.
+   */
+  const unsigned long LOAD_FLAGS_BYPASS_LOAD_URI_DELEGATE = 0x4000000;
+
+  /**
+   * This load has a user activation. (e.g: reload button was clicked)
+   */
+  const unsigned long LOAD_FLAGS_USER_ACTIVATION = 0x8000000;
+
+  /**
+   * Loads a given URI.  This will give priority to loading the requested URI
+   * in the object implementing this interface.  If it can't be loaded here
+   * however, the URI dispatcher will go through its normal process of content
+   * loading.
+   *
+   * @param aURI
+   *        The URI to load.
+   * @param aLoadURIOptions
+   *        A JSObject defined in LoadURIOptions.webidl holding info like e.g.
+   *        the triggeringPrincipal, the referrer info.
+   */
+  [implicit_jscontext, binaryname(LoadURIFromScript)]
+  void loadURI(in nsIURI aURI,
+               in jsval  aLoadURIOptions);
+
+  /**
+   * Parse / fix up a URI out of the string and load it.
+   * This will give priority to loading the requested URI
+   * in the object implementing this interface.  If it can't be loaded here
+   * however, the URI dispatcher will go through its normal process of content
+   * loading.
+   *
+   * @param aURIString
+   *        The URI string to load.  For HTTP and FTP URLs and possibly others,
+   *        characters above U+007F will be converted to UTF-8 and then URL-
+   *        escaped per the rules of RFC 2396.
+   *        This method may use nsIURIFixup to try to fix up typos etc. in the
+   *        input string based on the load flag arguments in aLoadURIOptions.
+   *        It can even convert the input to a search results page using the
+   *        default search service.
+   *        If you have an nsIURI anyway, prefer calling `loadURI`, above.
+   * @param aLoadURIOptions
+   *        A JSObject defined in LoadURIOptions.webidl holding info like e.g.
+   *        the triggeringPrincipal, the referrer info.
+   */
+  [implicit_jscontext, binaryname(FixupAndLoadURIStringFromScript)]
+  void fixupAndLoadURIString(in AString aURIString,
+                             in jsval   aLoadURIOptions);
+
+  /**
+   * A C++ friendly version of loadURI
+   */
+  [nostdcall, binaryname(LoadURI)]
+  void binaryLoadURI(in nsIURI            aURI,
+                     in LoadURIOptionsRef aLoadURIOptions);
+
+  /**
+   * A C++ friendly version of fixupAndLoadURIString
+   */
+  [nostdcall, binaryname(FixupAndLoadURIString)]
+  void binaryFixupAndLoadURIString(in AString           aURIString,
+                                   in LoadURIOptionsRef aLoadURIOptions);
+
+  /**
+   * Tells the Object to reload the current page.  There may be cases where the
+   * user will be asked to confirm the reload (for example, when it is
+   * determined that the request is non-idempotent).
+   *
+   * @param aReloadFlags
+   *        Flags modifying load behaviour.  This parameter is a bitwise
+   *        combination of the Load Flags defined above.  (Undefined bits are
+   *        reserved for future use.)  Generally you will pass LOAD_FLAGS_NONE
+   *        for this parameter.
+   *
+   * @throw NS_BINDING_ABORTED
+   *        Indicating that the user canceled the reload.
+   */
+  void reload(in unsigned long aReloadFlags);
+
+  /****************************************************************************
+   * The following flags may be passed as the stop flags parameter to the stop
+   * method defined on this interface.
+   */
+
+  /**
+   * This flag specifies that all network activity should be stopped.  This
+   * includes both active network loads and pending META-refreshes.
+   */
+  const unsigned long STOP_NETWORK = 0x01;
+
+  /**
+   * This flag specifies that all content activity should be stopped.  This
+   * includes animated images, plugins and pending Javascript timeouts.
+   */
+  const unsigned long STOP_CONTENT = 0x02;
+
+  /**
+   * This flag specifies that all activity should be stopped.
+   */
+  const unsigned long STOP_ALL     = 0x03;
+
+  /**
+   * Stops a load of a URI.
+   *
+   * @param aStopFlags
+   *        This parameter is one of the stop flags defined above.
+   */
+  void stop(in unsigned long aStopFlags);
+
+  /**
+   * Retrieves the current DOM document for the frame, or lazily creates a
+   * blank document if there is none.  This attribute never returns null except
+   * for unexpected error situations.
+   */
+  readonly attribute Document document;
+
+  /**
+   * The currently loaded URI or null.
+   */
+  readonly attribute nsIURI currentURI;
+
+  /**
+   * The session history object used by this web navigation instance. This
+   * object will be a mozilla::dom::ChildSHistory object, but is returned as
+   * nsISupports so it can be called from JS code.
+   */
+  [binaryname(SessionHistoryXPCOM)]
+  readonly attribute nsISupports sessionHistory;
+
+  %{ C++
+  /**
+   * Get the session history object used by this nsIWebNavigation instance.
+   * Use this method instead of the XPCOM method when getting the
+   * SessionHistory from C++ code.
+   */
+  already_AddRefed<mozilla::dom::ChildSHistory>
+  GetSessionHistory()
+  {
+    nsCOMPtr<nsISupports> history;
+    GetSessionHistoryXPCOM(getter_AddRefs(history));
+    return history.forget()
+      .downcast<mozilla::dom::ChildSHistory>();
+  }
+  %}
+
+  /**
+   * Resume a load which has been redirected from another process.
+   *
+   * A negative |aHistoryIndex| value corresponds to a non-history load being
+   * resumed.
+   */
+  void resumeRedirectedLoad(in unsigned long long aLoadIdentifier,
+                            in long aHistoryIndex);
+};
diff --git a/docshell/base/nsIWebNavigationInfo.idl b/docshell/base/nsIWebNavigationInfo.idl
new file mode 100644
index 0000000000..0c3d07a8ed
--- /dev/null
+++ b/docshell/base/nsIWebNavigationInfo.idl
@@ -0,0 +1,55 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * The nsIWebNavigationInfo interface exposes a way to get information
+ * on the capabilities of Gecko webnavigation objects.
+ */
+[scriptable, uuid(62a93afb-93a1-465c-84c8-0432264229de)]
+interface nsIWebNavigationInfo : nsISupports
+{
+  /**
+   * Returned by isTypeSupported to indicate lack of support for a type.
+   * @note this is guaranteed not to change, so that boolean tests can be done
+   * on the return value if isTypeSupported to detect whether a type is
+   * supported at all.
+   */
+  const unsigned long UNSUPPORTED = 0;
+
+  /**
+   * Returned by isTypeSupported to indicate that a type is supported as an
+   * image.
+   */
+  const unsigned long IMAGE = 1;
+
+  /**
+   * Returned by isTypeSupported to indicate that a type is a special NPAPI
+   * plugin that render as a transparent region (we do not support NPAPI
+   * plugins).
+   */
+  const unsigned long FALLBACK = 2;
+
+  /**
+   * @note Other return types may be added here in the future as they become
+   * relevant.
+   */
+
+  /**
+   * Returned by isTypeSupported to indicate that a type is supported via some
+   * other means.
+   */
+  const unsigned long OTHER = 1 << 15;
+
+  /**
+   * Query whether aType is supported.
+   * @param aType the MIME type in question.
+   * @return an enum value indicating whether and how aType is supported.
+   * @note This method may rescan plugins to ensure that they're properly
+   *       registered for the types they support.
+   */
+  unsigned long isTypeSupported(in ACString aType);
+};
diff --git a/docshell/base/nsIWebPageDescriptor.idl b/docshell/base/nsIWebPageDescriptor.idl
new file mode 100644
index 0000000000..866cb54e6b
--- /dev/null
+++ b/docshell/base/nsIWebPageDescriptor.idl
@@ -0,0 +1,30 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "nsISupports.idl"
+interface nsIDocShell;
+
+/**
+ * The nsIWebPageDescriptor interface allows content being displayed in one
+ * window to be loaded into another window without refetching it from the
+ * network.
+ */
+
+[scriptable, uuid(6f30b676-3710-4c2c-80b1-0395fb26516e)]
+interface nsIWebPageDescriptor : nsISupports
+{
+ /**
+  * Tells the object to load the page that otherDocShell is currently loading,
+  * or has loaded already, as view source, with the url being `aURL`.
+  *
+  * @throws NS_ERROR_FAILURE - NS_ERROR_INVALID_POINTER
+  */
+  void loadPageAsViewSource(in nsIDocShell otherDocShell, in AString aURL);
+
+
+ /**
+  * Retrieves the page descriptor for the curent document.
+  * @note, currentDescriptor is currently always an nsISHEntry object or null.
+  */
+  readonly attribute nsISupports currentDescriptor;
+};
diff --git a/docshell/base/nsPingListener.cpp b/docshell/base/nsPingListener.cpp
new file mode 100644
index 0000000000..094074a0b9
--- /dev/null
+++ b/docshell/base/nsPingListener.cpp
@@ -0,0 +1,345 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsPingListener.h"
+
+#include "mozilla/Encoding.h"
+#include "mozilla/Preferences.h"
+
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/dom/Document.h"
+
+#include "nsIHttpChannel.h"
+#include "nsIHttpChannelInternal.h"
+#include "nsIInputStream.h"
+#include "nsIProtocolHandler.h"
+#include "nsIUploadChannel2.h"
+
+#include "nsComponentManagerUtils.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "nsWhitespaceTokenizer.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+NS_IMPL_ISUPPORTS(nsPingListener, nsIStreamListener, nsIRequestObserver)
+
+//*****************************************************************************
+// <a ping> support
+//*****************************************************************************
+
+#define PREF_PINGS_ENABLED "browser.send_pings"
+#define PREF_PINGS_MAX_PER_LINK "browser.send_pings.max_per_link"
+#define PREF_PINGS_REQUIRE_SAME_HOST "browser.send_pings.require_same_host"
+
+// Check prefs to see if pings are enabled and if so what restrictions might
+// be applied.
+//
+// @param maxPerLink
+//   This parameter returns the number of pings that are allowed per link click
+//
+// @param requireSameHost
+//   This parameter returns true if pings are restricted to the same host as
+//   the document in which the click occurs.  If the same host restriction is
+//   imposed, then we still allow for pings to cross over to different
+//   protocols and ports for flexibility and because it is not possible to send
+//   a ping via FTP.
+//
+// @returns
+//   true if pings are enabled and false otherwise.
+//
+static bool PingsEnabled(int32_t* aMaxPerLink, bool* aRequireSameHost) {
+  bool allow = Preferences::GetBool(PREF_PINGS_ENABLED, false);
+
+  *aMaxPerLink = 1;
+  *aRequireSameHost = true;
+
+  if (allow) {
+    Preferences::GetInt(PREF_PINGS_MAX_PER_LINK, aMaxPerLink);
+    Preferences::GetBool(PREF_PINGS_REQUIRE_SAME_HOST, aRequireSameHost);
+  }
+
+  return allow;
+}
+
+// We wait this many milliseconds before killing the ping channel...
+#define PING_TIMEOUT 10000
+
+static void OnPingTimeout(nsITimer* aTimer, void* aClosure) {
+  nsILoadGroup* loadGroup = static_cast<nsILoadGroup*>(aClosure);
+  if (loadGroup) {
+    loadGroup->Cancel(NS_ERROR_ABORT);
+  }
+}
+
+struct MOZ_STACK_CLASS SendPingInfo {
+  int32_t numPings;
+  int32_t maxPings;
+  bool requireSameHost;
+  nsIURI* target;
+  nsIReferrerInfo* referrerInfo;
+  nsIDocShell* docShell;
+};
+
+static void SendPing(void* aClosure, nsIContent* aContent, nsIURI* aURI,
+                     nsIIOService* aIOService) {
+  SendPingInfo* info = static_cast<SendPingInfo*>(aClosure);
+  if (info->maxPings > -1 && info->numPings >= info->maxPings) {
+    return;
+  }
+
+  Document* doc = aContent->OwnerDoc();
+
+  nsCOMPtr<nsIChannel> chan;
+  NS_NewChannel(getter_AddRefs(chan), aURI, doc,
+                info->requireSameHost
+                    ? nsILoadInfo::SEC_REQUIRE_SAME_ORIGIN_DATA_IS_BLOCKED
+                    : nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+                nsIContentPolicy::TYPE_PING,
+                nullptr,                  // PerformanceStorage
+                nullptr,                  // aLoadGroup
+                nullptr,                  // aCallbacks
+                nsIRequest::LOAD_NORMAL,  // aLoadFlags,
+                aIOService);
+
+  if (!chan) {
+    return;
+  }
+
+  // Don't bother caching the result of this URI load, but do not exempt
+  // it from Safe Browsing.
+  chan->SetLoadFlags(nsIRequest::INHIBIT_CACHING);
+
+  nsCOMPtr<nsIHttpChannel> httpChan = do_QueryInterface(chan);
+  if (!httpChan) {
+    return;
+  }
+
+  // This is needed in order for 3rd-party cookie blocking to work.
+  nsCOMPtr<nsIHttpChannelInternal> httpInternal = do_QueryInterface(httpChan);
+  nsresult rv;
+  if (httpInternal) {
+    rv = httpInternal->SetDocumentURI(doc->GetDocumentURI());
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+  }
+
+  rv = httpChan->SetRequestMethod("POST"_ns);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  // Remove extraneous request headers (to reduce request size)
+  rv = httpChan->SetRequestHeader("accept"_ns, ""_ns, false);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  rv = httpChan->SetRequestHeader("accept-language"_ns, ""_ns, false);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  rv = httpChan->SetRequestHeader("accept-encoding"_ns, ""_ns, false);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  // Always send a Ping-To header.
+  nsAutoCString pingTo;
+  if (NS_SUCCEEDED(info->target->GetSpec(pingTo))) {
+    rv = httpChan->SetRequestHeader("Ping-To"_ns, pingTo, false);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+  }
+
+  nsCOMPtr<nsIScriptSecurityManager> sm =
+      do_GetService(NS_SCRIPTSECURITYMANAGER_CONTRACTID);
+
+  if (sm && info->referrerInfo) {
+    nsCOMPtr<nsIURI> referrer = info->referrerInfo->GetOriginalReferrer();
+    bool referrerIsSecure = false;
+    uint32_t flags = nsIProtocolHandler::URI_IS_POTENTIALLY_TRUSTWORTHY;
+    if (referrer) {
+      rv = NS_URIChainHasFlags(referrer, flags, &referrerIsSecure);
+    }
+
+    // Default to sending less data if NS_URIChainHasFlags() fails.
+    referrerIsSecure = NS_FAILED(rv) || referrerIsSecure;
+
+    bool isPrivateWin = false;
+    if (doc) {
+      isPrivateWin =
+          doc->NodePrincipal()->OriginAttributesRef().mPrivateBrowsingId > 0;
+    }
+
+    bool sameOrigin = NS_SUCCEEDED(
+        sm->CheckSameOriginURI(referrer, aURI, false, isPrivateWin));
+
+    // If both the address of the document containing the hyperlink being
+    // audited and "ping URL" have the same origin or the document containing
+    // the hyperlink being audited was not retrieved over an encrypted
+    // connection, send a Ping-From header.
+    if (sameOrigin || !referrerIsSecure) {
+      nsAutoCString pingFrom;
+      if (NS_SUCCEEDED(referrer->GetSpec(pingFrom))) {
+        rv = httpChan->SetRequestHeader("Ping-From"_ns, pingFrom, false);
+        MOZ_ASSERT(NS_SUCCEEDED(rv));
+      }
+    }
+
+    // If the document containing the hyperlink being audited was not retrieved
+    // over an encrypted connection and its address does not have the same
+    // origin as "ping URL", send a referrer.
+    if (!sameOrigin && !referrerIsSecure && info->referrerInfo) {
+      rv = httpChan->SetReferrerInfo(info->referrerInfo);
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+    }
+  }
+
+  nsCOMPtr<nsIUploadChannel2> uploadChan = do_QueryInterface(httpChan);
+  if (!uploadChan) {
+    return;
+  }
+
+  constexpr auto uploadData = "PING"_ns;
+
+  nsCOMPtr<nsIInputStream> uploadStream;
+  rv = NS_NewCStringInputStream(getter_AddRefs(uploadStream), uploadData);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  uploadChan->ExplicitSetUploadStream(uploadStream, "text/ping"_ns,
+                                      uploadData.Length(), "POST"_ns, false);
+
+  // The channel needs to have a loadgroup associated with it, so that we can
+  // cancel the channel and any redirected channels it may create.
+  nsCOMPtr<nsILoadGroup> loadGroup = do_CreateInstance(NS_LOADGROUP_CONTRACTID);
+  if (!loadGroup) {
+    return;
+  }
+  nsCOMPtr<nsIInterfaceRequestor> callbacks = do_QueryInterface(info->docShell);
+  loadGroup->SetNotificationCallbacks(callbacks);
+  chan->SetLoadGroup(loadGroup);
+
+  RefPtr<nsPingListener> pingListener = new nsPingListener();
+  chan->AsyncOpen(pingListener);
+
+  // Even if AsyncOpen failed, we still count this as a successful ping.  It's
+  // possible that AsyncOpen may have failed after triggering some background
+  // process that may have written something to the network.
+  info->numPings++;
+
+  // Prevent ping requests from stalling and never being garbage collected...
+  if (NS_FAILED(pingListener->StartTimeout(doc->GetDocGroup()))) {
+    // If we failed to setup the timer, then we should just cancel the channel
+    // because we won't be able to ensure that it goes away in a timely manner.
+    chan->Cancel(NS_ERROR_ABORT);
+    return;
+  }
+  // if the channel openend successfully, then make the pingListener hold
+  // a strong reference to the loadgroup which is released in ::OnStopRequest
+  pingListener->SetLoadGroup(loadGroup);
+}
+
+typedef void (*ForEachPingCallback)(void* closure, nsIContent* content,
+                                    nsIURI* uri, nsIIOService* ios);
+
+static void ForEachPing(nsIContent* aContent, ForEachPingCallback aCallback,
+                        void* aClosure) {
+  // NOTE: Using nsIDOMHTMLAnchorElement::GetPing isn't really worth it here
+  //       since we'd still need to parse the resulting string.  Instead, we
+  //       just parse the raw attribute.  It might be nice if the content node
+  //       implemented an interface that exposed an enumeration of nsIURIs.
+
+  // Make sure we are dealing with either an <A> or <AREA> element in the HTML
+  // or XHTML namespace.
+  if (!aContent->IsAnyOfHTMLElements(nsGkAtoms::a, nsGkAtoms::area)) {
+    return;
+  }
+
+  nsAutoString value;
+  aContent->AsElement()->GetAttr(nsGkAtoms::ping, value);
+  if (value.IsEmpty()) {
+    return;
+  }
+
+  nsCOMPtr<nsIIOService> ios = do_GetIOService();
+  if (!ios) {
+    return;
+  }
+
+  Document* doc = aContent->OwnerDoc();
+  nsAutoCString charset;
+  doc->GetDocumentCharacterSet()->Name(charset);
+
+  nsWhitespaceTokenizer tokenizer(value);
+
+  while (tokenizer.hasMoreTokens()) {
+    nsCOMPtr<nsIURI> uri;
+    NS_NewURI(getter_AddRefs(uri), tokenizer.nextToken(), charset.get(),
+              aContent->GetBaseURI());
+    // if we can't generate a valid URI, then there is nothing to do
+    if (!uri) {
+      continue;
+    }
+    // Explicitly not allow loading data: URIs
+    if (!net::SchemeIsData(uri)) {
+      aCallback(aClosure, aContent, uri, ios);
+    }
+  }
+}
+
+// Spec: http://whatwg.org/specs/web-apps/current-work/#ping
+/*static*/ void nsPingListener::DispatchPings(nsIDocShell* aDocShell,
+                                              nsIContent* aContent,
+                                              nsIURI* aTarget,
+                                              nsIReferrerInfo* aReferrerInfo) {
+  SendPingInfo info;
+
+  if (!PingsEnabled(&info.maxPings, &info.requireSameHost)) {
+    return;
+  }
+  if (info.maxPings == 0) {
+    return;
+  }
+
+  info.numPings = 0;
+  info.target = aTarget;
+  info.referrerInfo = aReferrerInfo;
+  info.docShell = aDocShell;
+
+  ForEachPing(aContent, SendPing, &info);
+}
+
+nsPingListener::~nsPingListener() {
+  if (mTimer) {
+    mTimer->Cancel();
+    mTimer = nullptr;
+  }
+}
+
+nsresult nsPingListener::StartTimeout(DocGroup* aDocGroup) {
+  NS_ENSURE_ARG(aDocGroup);
+
+  return NS_NewTimerWithFuncCallback(
+      getter_AddRefs(mTimer), OnPingTimeout, mLoadGroup, PING_TIMEOUT,
+      nsITimer::TYPE_ONE_SHOT, "nsPingListener::StartTimeout",
+      GetMainThreadSerialEventTarget());
+}
+
+NS_IMETHODIMP
+nsPingListener::OnStartRequest(nsIRequest* aRequest) { return NS_OK; }
+
+NS_IMETHODIMP
+nsPingListener::OnDataAvailable(nsIRequest* aRequest, nsIInputStream* aStream,
+                                uint64_t aOffset, uint32_t aCount) {
+  uint32_t result;
+  return aStream->ReadSegments(NS_DiscardSegment, nullptr, aCount, &result);
+}
+
+NS_IMETHODIMP
+nsPingListener::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
+  mLoadGroup = nullptr;
+
+  if (mTimer) {
+    mTimer->Cancel();
+    mTimer = nullptr;
+  }
+
+  return NS_OK;
+}
diff --git a/docshell/base/nsPingListener.h b/docshell/base/nsPingListener.h
new file mode 100644
index 0000000000..7cf6ff98b5
--- /dev/null
+++ b/docshell/base/nsPingListener.h
@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsPingListener_h__
+#define nsPingListener_h__
+
+#include "nsIStreamListener.h"
+#include "nsIReferrerInfo.h"
+#include "nsCOMPtr.h"
+
+namespace mozilla {
+namespace dom {
+class DocGroup;
+}
+}  // namespace mozilla
+
+class nsIContent;
+class nsIDocShell;
+class nsILoadGroup;
+class nsITimer;
+class nsIURI;
+
+class nsPingListener final : public nsIStreamListener {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSISTREAMLISTENER
+
+  nsPingListener() {}
+
+  void SetLoadGroup(nsILoadGroup* aLoadGroup) { mLoadGroup = aLoadGroup; }
+
+  nsresult StartTimeout(mozilla::dom::DocGroup* aDocGroup);
+
+  static void DispatchPings(nsIDocShell* aDocShell, nsIContent* aContent,
+                            nsIURI* aTarget, nsIReferrerInfo* aReferrerInfo);
+
+ private:
+  ~nsPingListener();
+
+  nsCOMPtr<nsILoadGroup> mLoadGroup;
+  nsCOMPtr<nsITimer> mTimer;
+};
+
+#endif /* nsPingListener_h__ */
diff --git a/docshell/base/nsRefreshTimer.cpp b/docshell/base/nsRefreshTimer.cpp
new file mode 100644
index 0000000000..867e3ba1cb
--- /dev/null
+++ b/docshell/base/nsRefreshTimer.cpp
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsRefreshTimer.h"
+
+#include "nsIURI.h"
+#include "nsIPrincipal.h"
+
+#include "nsDocShell.h"
+
+NS_IMPL_ADDREF(nsRefreshTimer)
+NS_IMPL_RELEASE(nsRefreshTimer)
+
+NS_INTERFACE_MAP_BEGIN(nsRefreshTimer)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsITimerCallback)
+  NS_INTERFACE_MAP_ENTRY(nsITimerCallback)
+  NS_INTERFACE_MAP_ENTRY(nsINamed)
+NS_INTERFACE_MAP_END
+
+nsRefreshTimer::nsRefreshTimer(nsDocShell* aDocShell, nsIURI* aURI,
+                               nsIPrincipal* aPrincipal, int32_t aDelay)
+    : mDocShell(aDocShell),
+      mURI(aURI),
+      mPrincipal(aPrincipal),
+      mDelay(aDelay) {}
+
+nsRefreshTimer::~nsRefreshTimer() {}
+
+NS_IMETHODIMP
+nsRefreshTimer::Notify(nsITimer* aTimer) {
+  NS_ASSERTION(mDocShell, "DocShell is somehow null");
+
+  if (mDocShell && aTimer) {
+    // Get the delay count to determine load type
+    uint32_t delay = 0;
+    aTimer->GetDelay(&delay);
+    mDocShell->ForceRefreshURIFromTimer(mURI, mPrincipal, delay, aTimer);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsRefreshTimer::GetName(nsACString& aName) {
+  aName.AssignLiteral("nsRefreshTimer");
+  return NS_OK;
+}
diff --git a/docshell/base/nsRefreshTimer.h b/docshell/base/nsRefreshTimer.h
new file mode 100644
index 0000000000..423f8807eb
--- /dev/null
+++ b/docshell/base/nsRefreshTimer.h
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsRefreshTimer_h__
+#define nsRefreshTimer_h__
+
+#include "nsINamed.h"
+#include "nsITimer.h"
+
+#include "nsCOMPtr.h"
+
+class nsDocShell;
+class nsIURI;
+class nsIPrincipal;
+
+class nsRefreshTimer : public nsITimerCallback, public nsINamed {
+ public:
+  nsRefreshTimer(nsDocShell* aDocShell, nsIURI* aURI, nsIPrincipal* aPrincipal,
+                 int32_t aDelay);
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSITIMERCALLBACK
+  NS_DECL_NSINAMED
+
+  int32_t GetDelay() { return mDelay; }
+
+  RefPtr<nsDocShell> mDocShell;
+  nsCOMPtr<nsIURI> mURI;
+  nsCOMPtr<nsIPrincipal> mPrincipal;
+  int32_t mDelay;
+
+ private:
+  virtual ~nsRefreshTimer();
+};
+
+#endif /* nsRefreshTimer_h__ */
diff --git a/docshell/base/nsWebNavigationInfo.cpp b/docshell/base/nsWebNavigationInfo.cpp
new file mode 100644
index 0000000000..cb989a33f1
--- /dev/null
+++ b/docshell/base/nsWebNavigationInfo.cpp
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsWebNavigationInfo.h"
+
+#include "nsServiceManagerUtils.h"
+#include "nsIDocumentLoaderFactory.h"
+#include "nsContentUtils.h"
+#include "imgLoader.h"
+
+NS_IMPL_ISUPPORTS(nsWebNavigationInfo, nsIWebNavigationInfo)
+
+NS_IMETHODIMP
+nsWebNavigationInfo::IsTypeSupported(const nsACString& aType,
+                                     uint32_t* aIsTypeSupported) {
+  MOZ_ASSERT(aIsTypeSupported, "null out param?");
+
+  *aIsTypeSupported = IsTypeSupported(aType);
+  return NS_OK;
+}
+
+uint32_t nsWebNavigationInfo::IsTypeSupported(const nsACString& aType) {
+  // We want to claim that the type for PDF documents is unsupported,
+  // so that the internal PDF viewer's stream converted will get used.
+  if (aType.LowerCaseEqualsLiteral("application/pdf") &&
+      nsContentUtils::IsPDFJSEnabled()) {
+    return nsIWebNavigationInfo::UNSUPPORTED;
+  }
+
+  const nsCString& flatType = PromiseFlatCString(aType);
+  return IsTypeSupportedInternal(flatType);
+}
+
+uint32_t nsWebNavigationInfo::IsTypeSupportedInternal(const nsCString& aType) {
+  nsContentUtils::DocumentViewerType vtype = nsContentUtils::TYPE_UNSUPPORTED;
+
+  nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory =
+      nsContentUtils::FindInternalDocumentViewer(aType, &vtype);
+
+  switch (vtype) {
+    case nsContentUtils::TYPE_UNSUPPORTED:
+      return nsIWebNavigationInfo::UNSUPPORTED;
+
+    case nsContentUtils::TYPE_FALLBACK:
+      return nsIWebNavigationInfo::FALLBACK;
+
+    case nsContentUtils::TYPE_UNKNOWN:
+      return nsIWebNavigationInfo::OTHER;
+
+    case nsContentUtils::TYPE_CONTENT:
+      // XXXbz we only need this because images register for the same
+      // contractid as documents, so we can't tell them apart based on
+      // contractid.
+      if (imgLoader::SupportImageWithMimeType(aType)) {
+        return nsIWebNavigationInfo::IMAGE;
+      }
+      return nsIWebNavigationInfo::OTHER;
+  }
+
+  return nsIWebNavigationInfo::UNSUPPORTED;
+}
diff --git a/docshell/base/nsWebNavigationInfo.h b/docshell/base/nsWebNavigationInfo.h
new file mode 100644
index 0000000000..97b07c825e
--- /dev/null
+++ b/docshell/base/nsWebNavigationInfo.h
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsWebNavigationInfo_h__
+#define nsWebNavigationInfo_h__
+
+#include "nsIWebNavigationInfo.h"
+#include "nsCOMPtr.h"
+#include "nsICategoryManager.h"
+#include "nsStringFwd.h"
+#include "mozilla/Attributes.h"
+
+class nsWebNavigationInfo final : public nsIWebNavigationInfo {
+ public:
+  nsWebNavigationInfo() {}
+
+  NS_DECL_ISUPPORTS
+
+  NS_DECL_NSIWEBNAVIGATIONINFO
+
+  static uint32_t IsTypeSupported(const nsACString& aType);
+
+ private:
+  ~nsWebNavigationInfo() {}
+
+  // Check whether aType is supported, and returns an nsIWebNavigationInfo
+  // constant.
+  static uint32_t IsTypeSupportedInternal(const nsCString& aType);
+};
+
+#endif  // nsWebNavigationInfo_h__