Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

28 files changed, 5460 insertions, 0 deletions

diff --git a/toolkit/components/sessionstore/BrowserSessionStore.cpp b/toolkit/components/sessionstore/BrowserSessionStore.cpp
new file mode 100644
index 0000000000..f4da9646b2
--- /dev/null
+++ b/toolkit/components/sessionstore/BrowserSessionStore.cpp
@@ -0,0 +1,292 @@
+/* -*- 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/BrowserSessionStore.h"
+#include <algorithm>
+#include <cstdint>
+#include <functional>
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/IntegerRange.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPtr.h"
+
+#include "mozilla/dom/BrowserSessionStoreBinding.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/SessionStoreFormData.h"
+#include "mozilla/dom/SessionStoreScrollData.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+
+#include "nsTHashMap.h"
+#include "nsHashtablesFwd.h"
+
+#include "js/RootingAPI.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+static StaticAutoPtr<nsTHashMap<nsUint64HashKey, BrowserSessionStore*>>
+    sSessionStore;
+
+NS_IMPL_CYCLE_COLLECTION(BrowserSessionStore, mBrowsingContext, mFormData,
+                         mScrollData)
+
+/* static */
+already_AddRefed<BrowserSessionStore> BrowserSessionStore::GetOrCreate(
+    CanonicalBrowsingContext* aBrowsingContext) {
+  if (!aBrowsingContext->IsTop()) {
+    return nullptr;
+  }
+
+  if (!sSessionStore) {
+    sSessionStore = new nsTHashMap<nsUint64HashKey, BrowserSessionStore*>();
+    ClearOnShutdown(&sSessionStore);
+  }
+
+  return do_AddRef(sSessionStore->LookupOrInsertWith(
+      aBrowsingContext->Id(),
+      [&] { return new BrowserSessionStore(aBrowsingContext); }));
+}
+
+BrowserSessionStore::BrowserSessionStore(
+    CanonicalBrowsingContext* aBrowsingContext)
+    : mBrowsingContext(aBrowsingContext) {}
+
+SessionStoreFormData* BrowserSessionStore::GetFormdata() { return mFormData; }
+
+SessionStoreScrollData* BrowserSessionStore::GetScroll() { return mScrollData; }
+
+static bool ShouldUpdateSessionStore(CanonicalBrowsingContext* aBrowsingContext,
+                                     uint32_t aEpoch) {
+  if (!aBrowsingContext) {
+    return false;
+  }
+
+  if (aBrowsingContext->Top()->GetSessionStoreEpoch() != aEpoch) {
+    return false;
+  }
+
+  if (aBrowsingContext->IsReplaced()) {
+    return false;
+  }
+
+  if (aBrowsingContext->IsDynamic()) {
+    return false;
+  }
+
+  return true;
+}
+
+// With GetOrCreate we can create either of the weak fields:
+//   WeakPtr<SessionStoreFormData> mFormdata;
+//   WeakPtr<SessionStoreScrollData> mScroll;
+// in CanonicalBrowsingContext. If one already exists, then we return that.
+template <typename T, WeakPtr<T>& (CanonicalBrowsingContext::*GetWeakRef)()>
+static already_AddRefed<T> GetOrCreateEntry(
+    CanonicalBrowsingContext* aBrowsingContext) {
+  typename T::LocationType& location = (aBrowsingContext->*GetWeakRef)();
+  RefPtr<T> entry = location.get();
+  if (!entry) {
+    entry = MakeRefPtr<T>();
+    location = entry;
+  }
+
+  return entry.forget();
+}
+
+// With InsertEntry we can insert an entry in the session store data tree in
+// either of the weak fields:
+//   WeakPtr<SessionStoreFormData> mFormdata;
+//   WeakPtr<SessionStoreScrollData> mScroll;
+// in CanonicalBrowsingContext. If an entry is inserted where there is no parent
+// entry, a spine of entries will be created until one is found, or we reach the
+// top browsing context.
+template <typename T>
+void InsertEntry(BrowsingContext* aBrowsingContext, T* aParent, T* aUpdate) {
+  int32_t offset = aBrowsingContext->ChildOffset();
+  if (offset < 0) {
+    return;
+  }
+
+  aParent->ClearCachedChildren();
+
+  auto& children = aParent->Children();
+
+  children.EnsureLengthAtLeast(offset + 1);
+  if (children[offset] && !aBrowsingContext->Children().IsEmpty()) {
+    children[offset]->ClearCachedChildren();
+    aUpdate->ClearCachedChildren();
+  }
+
+  children[offset] = aUpdate;
+}
+
+// With RemoveEntry we can remove an entry in the session store data tree in
+// either of the weak fields:
+//   WeakPtr<SessionStoreFormData> mFormdata;
+//   WeakPtr<SessionStoreScrollData> mScroll;
+// in CanonicalBrowsingContext. If an entry is removed, where its parent doesn't
+// contain data, we'll remove the parent and repeat until we either find an
+// entry with data or reach the top browsing context.
+template <typename T>
+void RemoveEntry(BrowsingContext* aBrowsingContext, T* aParent) {
+  int32_t offset = aBrowsingContext->ChildOffset();
+  if (offset < 0) {
+    return;
+  }
+
+  if (!aParent) {
+    return;
+  }
+
+  aParent->ClearCachedChildren();
+
+  auto& children = aParent->Children();
+  size_t length = children.Length();
+  if (children.Length() <= static_cast<size_t>(offset)) {
+    // The children array doesn't extend to offset.
+    return;
+  }
+
+  if (static_cast<size_t>(offset) < length - 1) {
+    // offset is before the last item in the children array.
+    children[offset] = nullptr;
+    return;
+  }
+
+  // offset is the last item, find the first non-null item before it
+  // and remove anything after that item.
+  while (offset > 0 && !children[offset - 1]) {
+    --offset;
+  }
+
+  children.TruncateLength(offset);
+}
+
+// With UpdateSessionStoreField we can update an entry in the session store
+// data tree in either of the weak fields:
+//   WeakPtr<SessionStoreFormData> mFormdata;
+//   WeakPtr<SessionStoreScrollData> mScroll;
+// in CanonicalBrowsingContext. UpdateSessionStoreField uses the above
+// functions, `GetOrCreateEntry`, `InsertEntry` and `RemoveEntry` to operate on
+// the weak fields. We return the top-level entry attached to the top browsing
+// context through `aEntry`. If the entire browsing context tree contains no
+// session store data this will be set to nullptr.
+template <typename T, WeakPtr<T>& (CanonicalBrowsingContext::*GetWeakRef)()>
+void UpdateSessionStoreField(CanonicalBrowsingContext* aBrowsingContext,
+                             const typename T::CollectedType& aUpdate,
+                             T** aEntry) {
+  RefPtr<T> currentEntry;
+
+  if (T::HasData(aUpdate)) {
+    currentEntry = GetOrCreateEntry<T, GetWeakRef>(aBrowsingContext);
+    currentEntry->Update(aUpdate);
+
+    CanonicalBrowsingContext* currentBrowsingContext = aBrowsingContext;
+    while (CanonicalBrowsingContext* parent =
+               currentBrowsingContext->GetParent()) {
+      WeakPtr<T>& parentEntry = (parent->*GetWeakRef)();
+      if (parentEntry) {
+        InsertEntry(aBrowsingContext, parentEntry.get(), currentEntry.get());
+        break;
+      }
+
+      RefPtr<T> entry = GetOrCreateEntry<T, GetWeakRef>(parent);
+      InsertEntry(currentBrowsingContext, entry.get(), currentEntry.get());
+
+      currentEntry = entry;
+      currentBrowsingContext = parent;
+    }
+
+    currentEntry = (aBrowsingContext->Top()->*GetWeakRef)().get();
+  } else if ((currentEntry = (aBrowsingContext->*GetWeakRef)())) {
+    currentEntry->Update(aUpdate);
+
+    CanonicalBrowsingContext* currentBrowsingContext = aBrowsingContext;
+    while (CanonicalBrowsingContext* parent =
+               currentBrowsingContext->GetParent()) {
+      if (!currentEntry || !currentEntry->IsEmpty()) {
+        break;
+      }
+
+      T* parentEntry = (parent->*GetWeakRef)().get();
+      RemoveEntry(currentBrowsingContext, parentEntry);
+
+      currentEntry = parentEntry;
+      currentBrowsingContext = parent;
+    }
+
+    if (currentEntry && currentEntry->IsEmpty()) {
+      currentEntry = nullptr;
+    } else {
+      currentEntry = (aBrowsingContext->Top()->*GetWeakRef)().get();
+    }
+  } else {
+    currentEntry = (aBrowsingContext->Top()->*GetWeakRef)().get();
+  }
+
+  *aEntry = currentEntry.forget().take();
+}
+
+void BrowserSessionStore::UpdateSessionStore(
+    CanonicalBrowsingContext* aBrowsingContext,
+    const Maybe<sessionstore::FormData>& aFormData,
+    const Maybe<nsPoint>& aScrollPosition, uint32_t aEpoch) {
+  if (!aFormData && !aScrollPosition) {
+    return;
+  }
+
+  if (!ShouldUpdateSessionStore(aBrowsingContext, aEpoch)) {
+    return;
+  }
+
+  if (aFormData) {
+    UpdateSessionStoreField<
+        SessionStoreFormData,
+        &CanonicalBrowsingContext::GetSessionStoreFormDataRef>(
+        aBrowsingContext, *aFormData, getter_AddRefs(mFormData));
+  }
+
+  if (aScrollPosition) {
+    UpdateSessionStoreField<
+        SessionStoreScrollData,
+        &CanonicalBrowsingContext::GetSessionStoreScrollDataRef>(
+        aBrowsingContext, *aScrollPosition, getter_AddRefs(mScrollData));
+  }
+}
+
+void BrowserSessionStore::RemoveSessionStore(
+    CanonicalBrowsingContext* aBrowsingContext) {
+  if (!aBrowsingContext) {
+    return;
+  }
+
+  CanonicalBrowsingContext* parentContext = aBrowsingContext->GetParent();
+
+  if (parentContext) {
+    RemoveEntry(aBrowsingContext,
+                parentContext->GetSessionStoreFormDataRef().get());
+
+    RemoveEntry(aBrowsingContext,
+                parentContext->GetSessionStoreScrollDataRef().get());
+
+    return;
+  }
+
+  if (aBrowsingContext->IsTop()) {
+    mFormData = nullptr;
+    mScrollData = nullptr;
+  }
+}
+
+BrowserSessionStore::~BrowserSessionStore() {
+  if (sSessionStore) {
+    sSessionStore->Remove(mBrowsingContext->Id());
+  }
+}
diff --git a/toolkit/components/sessionstore/BrowserSessionStore.h b/toolkit/components/sessionstore/BrowserSessionStore.h
new file mode 100644
index 0000000000..011e7673ec
--- /dev/null
+++ b/toolkit/components/sessionstore/BrowserSessionStore.h
@@ -0,0 +1,57 @@
+/* -*- 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_SessionStore_h
+#define mozilla_dom_SessionStore_h
+
+#include "nsWrapperCache.h"
+
+#include "mozilla/Maybe.h"
+
+struct nsPoint;
+
+namespace mozilla::dom {
+
+class CanonicalBrowsingContext;
+class GlobalObject;
+class SessionStoreFormData;
+class SessionStoreScrollData;
+class WindowGlobalParent;
+
+namespace sessionstore {
+class FormData;
+}
+
+class BrowserSessionStore final {
+ public:
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(BrowserSessionStore)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(BrowserSessionStore)
+
+  static already_AddRefed<BrowserSessionStore> GetOrCreate(
+      CanonicalBrowsingContext* aBrowsingContext);
+
+  SessionStoreFormData* GetFormdata();
+  SessionStoreScrollData* GetScroll();
+
+  void UpdateSessionStore(CanonicalBrowsingContext* aBrowsingContext,
+                          const Maybe<sessionstore::FormData>& aFormData,
+                          const Maybe<nsPoint>& aScrollPosition,
+                          uint32_t aEpoch);
+
+  void RemoveSessionStore(CanonicalBrowsingContext* aBrowsingContext);
+
+ private:
+  explicit BrowserSessionStore(CanonicalBrowsingContext* aBrowsingContext);
+  virtual ~BrowserSessionStore();
+
+  RefPtr<CanonicalBrowsingContext> mBrowsingContext;
+  RefPtr<SessionStoreFormData> mFormData;
+  RefPtr<SessionStoreScrollData> mScrollData;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStore_h
diff --git a/toolkit/components/sessionstore/PSessionStore.ipdl b/toolkit/components/sessionstore/PSessionStore.ipdl
new file mode 100644
index 0000000000..4b7bb48849
--- /dev/null
+++ b/toolkit/components/sessionstore/PSessionStore.ipdl
@@ -0,0 +1,63 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 8 -*- */
+/* vim: set sw=2 ts=8 et tw=80 ft=cpp : */
+/* 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/GfxMessageUtils.h";
+
+include protocol PBrowser;
+include protocol PInProcess;
+include SessionStoreTypes;
+
+using mozilla::dom::MaybeDiscardedBrowsingContext from "mozilla/dom/BrowsingContext.h";
+using mozilla::dom::MaybeSessionStoreZoom from "mozilla/dom/SessionStoreScrollData.h";
+
+namespace mozilla {
+namespace dom {
+
+/**
+ * The PSessionStore actor handles collection of session store data from content
+ * type documents. It can be used both in a content process and in the parent
+ * process. In particular it solves the problem of handling incremental updates
+ * to the session store, since we're collecting from potentially several content
+ * processes.
+ */
+async protocol PSessionStore
+{
+  manager PBrowser or PInProcess;
+
+parent:
+  /**
+   * Sends data to be stored and instructions to the session store to
+   * potentially collect data in the parent. This is data that is not
+   * collected incrementally.
+   */
+  async SessionStoreUpdate(
+    nsCString? aDocShellCaps, bool? aPrivateMode, MaybeSessionStoreZoom aZoom,
+    bool aNeedCollectSHistory, uint32_t aEpoch);
+
+  /**
+   * Sends data to be stored to the session store. The collected data
+   * is all the collected changed data from all the in-process documents
+   * in the process in which the SessionStoreChild actor lives.
+   */
+  async IncrementalSessionStoreUpdate(
+    MaybeDiscardedBrowsingContext aBrowsingContext, FormData? aFormData,
+    nsPoint? aScrollPosition, uint32_t aEpoch);
+
+  /**
+   * Drop all the collected data associated with the provided browsing
+   * context.
+   */
+  async ResetSessionStore(
+    MaybeDiscardedBrowsingContext aBrowsingContext, uint32_t aEpoch);
+
+child:
+  async FlushTabState() returns(bool aHadContext);
+
+  async __delete__();
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/toolkit/components/sessionstore/RestoreTabContentObserver.cpp b/toolkit/components/sessionstore/RestoreTabContentObserver.cpp
new file mode 100644
index 0000000000..b0dda66ff0
--- /dev/null
+++ b/toolkit/components/sessionstore/RestoreTabContentObserver.cpp
@@ -0,0 +1,112 @@
+/* -*- Mode: C++; 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 "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/Services.h"
+#include "nsIObserverService.h"
+#include "nsIURI.h"
+#include "nsNetUtil.h"
+#include "nsPIDOMWindow.h"
+#include "nsReadableUtils.h"
+#include "nsThreadUtils.h"
+#include "RestoreTabContentObserver.h"
+
+using namespace mozilla::dom;
+
+NS_IMPL_ISUPPORTS(RestoreTabContentObserver, nsIObserver)
+
+const char* const kAboutReaderTopic = "AboutReader:Ready";
+const char* const kContentDocumentLoaded = "content-document-loaded";
+const char* const kChromeDocumentLoaded = "chrome-document-loaded";
+
+/* static */
+void RestoreTabContentObserver::Initialize() {
+  MOZ_ASSERT(!gRestoreTabContentObserver);
+  MOZ_ASSERT(NS_IsMainThread());
+
+  RefPtr<RestoreTabContentObserver> observer = new RestoreTabContentObserver();
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (NS_WARN_IF(!obs)) {
+    return;
+  }
+
+  obs->AddObserver(observer, kAboutReaderTopic, false);
+  obs->AddObserver(observer, kContentDocumentLoaded, false);
+  obs->AddObserver(observer, kChromeDocumentLoaded, false);
+
+  gRestoreTabContentObserver = observer;
+}
+
+/* static */
+void RestoreTabContentObserver::Shutdown() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!gRestoreTabContentObserver) {
+    return;
+  }
+
+  RefPtr<RestoreTabContentObserver> observer = gRestoreTabContentObserver;
+  gRestoreTabContentObserver = nullptr;
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (!obs) {
+    return;
+  }
+
+  obs->RemoveObserver(observer, kAboutReaderTopic);
+  obs->RemoveObserver(observer, kContentDocumentLoaded);
+  obs->RemoveObserver(observer, kChromeDocumentLoaded);
+}
+
+NS_IMETHODIMP
+RestoreTabContentObserver::Observe(nsISupports* aSubject, const char* aTopic,
+                                   const char16_t* aData) {
+  nsCOMPtr<nsPIDOMWindowInner> inner;
+  if (!strcmp(aTopic, kAboutReaderTopic)) {
+    inner = do_QueryInterface(aSubject);
+  } else if (!strcmp(aTopic, kContentDocumentLoaded) ||
+             !strcmp(aTopic, kChromeDocumentLoaded)) {
+    nsCOMPtr<Document> doc = do_QueryInterface(aSubject);
+    inner = doc ? doc->GetInnerWindow() : nullptr;
+  }
+  if (!inner) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> uri = inner->GetDocumentURI();
+  if (!uri) {
+    return NS_OK;
+  }
+
+  // We'll handle loading about:reader with "AboutReader:Ready"
+  // rather than "content-document-loaded".
+  if (uri->SchemeIs("about") &&
+      StringBeginsWith(uri->GetSpecOrDefault(), "about:reader"_ns) &&
+      strcmp(aTopic, kAboutReaderTopic) != 0) {
+    return NS_OK;
+  }
+
+  RefPtr<BrowsingContext> bc = inner->GetBrowsingContext();
+  if (!bc || !bc->Top()->GetHasRestoreData()) {
+    return NS_OK;
+  }
+  if (XRE_IsParentProcess()) {
+    if (WindowGlobalParent* wgp = bc->Canonical()->GetCurrentWindowGlobal()) {
+      bc->Canonical()->Top()->RequestRestoreTabContent(wgp);
+    }
+  } else if (WindowContext* windowContext = bc->GetCurrentWindowContext()) {
+    if (WindowGlobalChild* wgc = windowContext->GetWindowGlobalChild()) {
+      wgc->SendRequestRestoreTabContent();
+    }
+  }
+  return NS_OK;
+}
+
+mozilla::StaticRefPtr<RestoreTabContentObserver>
+    RestoreTabContentObserver::gRestoreTabContentObserver;
diff --git a/toolkit/components/sessionstore/RestoreTabContentObserver.h b/toolkit/components/sessionstore/RestoreTabContentObserver.h
new file mode 100644
index 0000000000..edab379a55
--- /dev/null
+++ b/toolkit/components/sessionstore/RestoreTabContentObserver.h
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; 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/. */
+
+#ifndef mozilla_dom_RestoreTabContentObserver_h
+#define mozilla_dom_RestoreTabContentObserver_h
+
+#include "mozilla/StaticPtr.h"
+#include "nsIObserver.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla {
+namespace dom {
+
+// An observer for restoring session store data at a correct time.
+class RestoreTabContentObserver final : public nsIObserver {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  static void Initialize();
+  static void Shutdown();
+
+ private:
+  RestoreTabContentObserver() = default;
+
+  virtual ~RestoreTabContentObserver() = default;
+  static mozilla::StaticRefPtr<RestoreTabContentObserver>
+      gRestoreTabContentObserver;
+};
+}  // namespace dom
+}  // namespace mozilla
+#endif  // mozilla_dom_RestoreTabContentObserver_h
diff --git a/toolkit/components/sessionstore/SessionStoreChangeListener.cpp b/toolkit/components/sessionstore/SessionStoreChangeListener.cpp
new file mode 100644
index 0000000000..1418774a37
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreChangeListener.cpp
@@ -0,0 +1,393 @@
+/* -*- 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/SessionStoreChangeListener.h"
+
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/EventTarget.h"
+#include "mozilla/dom/SessionStoreChild.h"
+#include "mozilla/dom/SessionStoreUtils.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_browser.h"
+
+#include "nsBaseHashtable.h"
+#include "nsDocShell.h"
+#include "nsGenericHTMLElement.h"
+#include "nsIXULRuntime.h"
+#include "nsPIDOMWindow.h"
+#include "nsTHashMap.h"
+#include "nsTHashtable.h"
+#include "nsLayoutUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+namespace {
+constexpr auto kInput = u"input"_ns;
+constexpr auto kScroll = u"mozvisualscroll"_ns;
+constexpr auto kResize = u"mozvisualresize"_ns;
+
+static constexpr char kNoAutoUpdates[] =
+    "browser.sessionstore.debug.no_auto_updates";
+static constexpr char kInterval[] = "browser.sessionstore.interval";
+static const char* kObservedPrefs[] = {kNoAutoUpdates, kInterval, nullptr};
+}  // namespace
+
+inline void ImplCycleCollectionUnlink(
+    SessionStoreChangeListener::SessionStoreChangeTable& aField) {
+  aField.Clear();
+}
+
+inline void ImplCycleCollectionTraverse(
+    nsCycleCollectionTraversalCallback& aCallback,
+    const SessionStoreChangeListener::SessionStoreChangeTable& aField,
+    const char* aName, uint32_t aFlags = 0) {
+  for (auto iter = aField.ConstIter(); !iter.Done(); iter.Next()) {
+    CycleCollectionNoteChild(aCallback, iter.Key(), aName, aFlags);
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION(SessionStoreChangeListener, mBrowsingContext,
+                         mCurrentEventTarget, mSessionStoreChild,
+                         mSessionStoreChanges)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SessionStoreChangeListener)
+  NS_INTERFACE_MAP_ENTRY(nsINamed)
+  NS_INTERFACE_MAP_ENTRY(nsIObserver)
+  NS_INTERFACE_MAP_ENTRY(nsITimerCallback)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMEventListener)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIObserver)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(SessionStoreChangeListener)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(SessionStoreChangeListener)
+
+NS_IMETHODIMP
+SessionStoreChangeListener::GetName(nsACString& aName) {
+  aName.AssignLiteral("SessionStoreChangeListener");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreChangeListener::Notify(nsITimer* aTimer) {
+  FlushSessionStore();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreChangeListener::Observe(nsISupports* aSubject, const char* aTopic,
+                                    const char16_t* aData) {
+  FlushSessionStore();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreChangeListener::HandleEvent(dom::Event* aEvent) {
+  EventTarget* target = aEvent->GetTarget();
+  if (!target) {
+    return NS_OK;
+  }
+
+  nsIGlobalObject* global = target->GetOwnerGlobal();
+  if (!global) {
+    return NS_OK;
+  }
+
+  nsPIDOMWindowInner* inner = global->AsInnerWindow();
+  if (!inner) {
+    return NS_OK;
+  }
+
+  WindowContext* windowContext = inner->GetWindowContext();
+  if (!windowContext) {
+    return NS_OK;
+  }
+
+  BrowsingContext* browsingContext = windowContext->GetBrowsingContext();
+  if (!browsingContext) {
+    return NS_OK;
+  }
+
+  if (browsingContext->IsDynamic()) {
+    return NS_OK;
+  }
+
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+
+  if (eventType == kInput) {
+    RecordChange(windowContext, Change::Input);
+  } else if (eventType == kScroll) {
+    RecordChange(windowContext, Change::Scroll);
+  } else if (eventType == kResize && browsingContext->IsTop()) {
+    RecordChange(windowContext, Change::Resize);
+  }
+  return NS_OK;
+}
+
+/* static */ already_AddRefed<SessionStoreChangeListener>
+SessionStoreChangeListener::Create(BrowsingContext* aBrowsingContext) {
+  MOZ_RELEASE_ASSERT(
+      StaticPrefs::browser_sessionstore_platform_collection_AtStartup());
+  if (!aBrowsingContext) {
+    return nullptr;
+  }
+
+  RefPtr<SessionStoreChangeListener> listener =
+      new SessionStoreChangeListener(aBrowsingContext);
+  listener->Init();
+
+  return listener.forget();
+}
+
+void SessionStoreChangeListener::Stop() {
+  RemoveEventListeners();
+  Preferences::RemoveObservers(this, kObservedPrefs);
+}
+
+void SessionStoreChangeListener::UpdateEventTargets() {
+  RemoveEventListeners();
+  AddEventListeners();
+}
+
+static void CollectFormData(Document* aDocument,
+                            Maybe<sessionstore::FormData>& aFormData) {
+  aFormData.emplace();
+  auto& formData = aFormData.ref();
+  uint32_t size = SessionStoreUtils::CollectFormData(aDocument, formData);
+
+  Element* body = aDocument->GetBody();
+  if (aDocument->HasFlag(NODE_IS_EDITABLE) && body) {
+    IgnoredErrorResult result;
+    body->GetInnerHTML(formData.innerHTML(), result);
+    size += formData.innerHTML().Length();
+    if (!result.Failed()) {
+      formData.hasData() = true;
+    }
+  }
+
+  if (!formData.hasData()) {
+    return;
+  }
+
+  nsIURI* documentURI = aDocument->GetDocumentURI();
+  if (!documentURI) {
+    return;
+  }
+
+  documentURI->GetSpecIgnoringRef(formData.uri());
+
+  if (size > StaticPrefs::browser_sessionstore_dom_form_max_limit()) {
+    aFormData = Nothing();
+  }
+}
+
+static void GetZoom(BrowsingContext* aBrowsingContext,
+                    Maybe<SessionStoreZoom>& aZoom) {
+  nsIDocShell* docShell = aBrowsingContext->GetDocShell();
+  if (!docShell) {
+    return;
+  }
+
+  PresShell* presShell = docShell->GetPresShell();
+  if (!presShell) {
+    return;
+  }
+
+  LayoutDeviceIntSize displaySize;
+
+  if (!nsLayoutUtils::GetContentViewerSize(presShell->GetPresContext(),
+                                           displaySize)) {
+    return;
+  }
+
+  aZoom.emplace(presShell->GetResolution(), displaySize.width,
+                displaySize.height);
+}
+
+void SessionStoreChangeListener::FlushSessionStore() {
+  if (mTimer) {
+    mTimer->Cancel();
+    mTimer = nullptr;
+  }
+
+  bool collectSessionHistory = false;
+  bool collectWireFrame = false;
+  bool didResize = false;
+
+  for (auto& iter : mSessionStoreChanges) {
+    WindowContext* windowContext = iter.GetKey();
+    if (!windowContext) {
+      continue;
+    }
+
+    BrowsingContext* browsingContext = windowContext->GetBrowsingContext();
+
+    // This is a bit unfortunate, but is needed when a window context with a
+    // recorded change has become non-current before its data has been
+    // collected. This can happen either due to navigation or destruction, and
+    // in the previous case we don't want to collect, but in the latter we do.
+    // This could be cleaned up if we change. See bug 1770773.
+    if (!windowContext->IsCurrent() && !browsingContext->IsDiscarded()) {
+      continue;
+    }
+
+    RefPtr<Document> document = windowContext->GetDocument();
+    if (!document) {
+      continue;
+    }
+
+    EnumSet<Change> changes = iter.GetData();
+    Maybe<sessionstore::FormData> maybeFormData;
+    if (changes.contains(Change::Input)) {
+      CollectFormData(document, maybeFormData);
+    }
+
+    Maybe<nsPoint> maybeScroll;
+    PresShell* presShell = document->GetPresShell();
+
+    if (presShell && changes.contains(Change::Scroll)) {
+      maybeScroll = Some(presShell->GetVisualViewportOffset());
+    }
+
+    collectWireFrame = collectWireFrame || changes.contains(Change::WireFrame);
+
+    collectSessionHistory =
+        collectSessionHistory || changes.contains(Change::SessionHistory);
+
+    if (presShell && changes.contains(Change::Resize)) {
+      didResize = true;
+    }
+
+    mSessionStoreChild->IncrementalSessionStoreUpdate(
+        browsingContext, maybeFormData, maybeScroll, mEpoch);
+  }
+
+  if (collectWireFrame) {
+    collectSessionHistory = CollectWireframe() || collectSessionHistory;
+  }
+
+  mSessionStoreChanges.Clear();
+
+  Maybe<SessionStoreZoom> zoom;
+  if (didResize) {
+    GetZoom(mBrowsingContext->Top(), zoom);
+  }
+
+  mSessionStoreChild->UpdateSessionStore(collectSessionHistory, zoom);
+}
+
+/* static */
+SessionStoreChangeListener* SessionStoreChangeListener::CollectSessionStoreData(
+    WindowContext* aWindowContext, const EnumSet<Change>& aChanges) {
+  SessionStoreChild* sessionStoreChild =
+      SessionStoreChild::From(aWindowContext->GetWindowGlobalChild());
+  if (!sessionStoreChild) {
+    return nullptr;
+  }
+
+  SessionStoreChangeListener* sessionStoreChangeListener =
+      sessionStoreChild->GetSessionStoreChangeListener();
+
+  if (!sessionStoreChangeListener) {
+    return nullptr;
+  }
+
+  sessionStoreChangeListener->RecordChange(aWindowContext, aChanges);
+
+  return sessionStoreChangeListener;
+}
+
+void SessionStoreChangeListener::SetActor(
+    SessionStoreChild* aSessionStoreChild) {
+  mSessionStoreChild = aSessionStoreChild;
+}
+
+bool SessionStoreChangeListener::CollectWireframe() {
+  if (auto* docShell = nsDocShell::Cast(mBrowsingContext->GetDocShell())) {
+    return docShell->CollectWireframe();
+  }
+
+  return false;
+}
+
+void SessionStoreChangeListener::RecordChange(WindowContext* aWindowContext,
+                                              EnumSet<Change> aChange) {
+  EnsureTimer();
+
+  Unused << mSessionStoreChanges.WithEntryHandle(
+      aWindowContext, [&](auto entryHandle) -> EnumSet<Change>& {
+        if (entryHandle) {
+          *entryHandle += aChange;
+          return *entryHandle;
+        }
+
+        return entryHandle.Insert(aChange);
+      });
+}
+
+SessionStoreChangeListener::SessionStoreChangeListener(
+    BrowsingContext* aBrowsingContext)
+    : mBrowsingContext(aBrowsingContext),
+      mEpoch(aBrowsingContext->GetSessionStoreEpoch()) {}
+
+void SessionStoreChangeListener::Init() {
+  AddEventListeners();
+
+  Preferences::AddStrongObservers(this, kObservedPrefs);
+}
+
+EventTarget* SessionStoreChangeListener::GetEventTarget() {
+  if (mBrowsingContext->GetDOMWindow()) {
+    return mBrowsingContext->GetDOMWindow()->GetChromeEventHandler();
+  }
+
+  return nullptr;
+}
+
+void SessionStoreChangeListener::AddEventListeners() {
+  if (EventTarget* target = GetEventTarget()) {
+    target->AddSystemEventListener(kInput, this, false);
+    target->AddSystemEventListener(kScroll, this, false);
+    if (StaticPrefs::browser_sessionstore_collect_zoom_AtStartup()) {
+      target->AddSystemEventListener(kResize, this, false);
+    }
+    mCurrentEventTarget = target;
+  }
+}
+
+void SessionStoreChangeListener::RemoveEventListeners() {
+  if (mCurrentEventTarget) {
+    mCurrentEventTarget->RemoveSystemEventListener(kInput, this, false);
+    mCurrentEventTarget->RemoveSystemEventListener(kScroll, this, false);
+    if (StaticPrefs::browser_sessionstore_collect_zoom_AtStartup()) {
+      mCurrentEventTarget->RemoveSystemEventListener(kResize, this, false);
+    }
+  }
+
+  mCurrentEventTarget = nullptr;
+}
+
+void SessionStoreChangeListener::EnsureTimer() {
+  if (mTimer) {
+    return;
+  }
+
+  if (!StaticPrefs::browser_sessionstore_debug_no_auto_updates()) {
+    auto result = NS_NewTimerWithCallback(
+        this, StaticPrefs::browser_sessionstore_interval(),
+        nsITimer::TYPE_ONE_SHOT);
+    if (result.isErr()) {
+      return;
+    }
+
+    mTimer = result.unwrap();
+  }
+}
diff --git a/toolkit/components/sessionstore/SessionStoreChangeListener.h b/toolkit/components/sessionstore/SessionStoreChangeListener.h
new file mode 100644
index 0000000000..803a2137bd
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreChangeListener.h
@@ -0,0 +1,103 @@
+/* -*- 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_SessionStoreChangeListener_h
+#define mozilla_dom_SessionStoreChangeListener_h
+
+#include "ErrorList.h"
+
+#include "PLDHashTable.h"
+#include "mozilla/EnumSet.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsHashKeys.h"
+#include "nsIDOMEventListener.h"
+#include "nsIObserver.h"
+#include "nsISupports.h"
+#include "nsITimer.h"
+#include "nsINamed.h"
+#include "nsHashtablesFwd.h"
+
+#include "mozilla/EnumSet.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Result.h"
+
+#include "mozilla/dom/WindowGlobalChild.h"
+
+namespace mozilla::dom {
+
+class BrowsingContext;
+class Element;
+class EventTarget;
+class SessionStoreChild;
+class WindowContext;
+
+class SessionStoreChangeListener final : public nsINamed,
+                                         public nsIObserver,
+                                         public nsITimerCallback,
+                                         public nsIDOMEventListener {
+ public:
+  NS_DECL_NSINAMED
+  NS_DECL_NSIOBSERVER
+  NS_DECL_NSITIMERCALLBACK
+  NS_DECL_NSIDOMEVENTLISTENER
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(SessionStoreChangeListener,
+                                           nsIObserver)
+
+  static already_AddRefed<SessionStoreChangeListener> Create(
+      BrowsingContext* aBrowsingContext);
+
+  void Stop();
+
+  void UpdateEventTargets();
+
+  void FlushSessionStore();
+
+  enum class Change { Input, Scroll, SessionHistory, WireFrame, Resize };
+
+  static SessionStoreChangeListener* CollectSessionStoreData(
+      WindowContext* aWindowContext, const EnumSet<Change>& aChanges);
+
+  void SetActor(SessionStoreChild* aSessionStoreChild);
+
+  void SetEpoch(uint32_t aEpoch) { mEpoch = aEpoch; }
+
+  uint32_t GetEpoch() const { return mEpoch; }
+
+  bool CollectWireframe();
+
+ private:
+  void RecordChange(WindowContext* aWindowContext, EnumSet<Change> aChanges);
+
+ public:
+  using SessionStoreChangeTable =
+      nsTHashMap<RefPtr<WindowContext>, EnumSet<Change>>;
+
+ private:
+  explicit SessionStoreChangeListener(BrowsingContext* aBrowsingContext);
+  ~SessionStoreChangeListener() = default;
+
+  void Init();
+
+  EventTarget* GetEventTarget();
+
+  void AddEventListeners();
+  void RemoveEventListeners();
+
+  void EnsureTimer();
+
+  RefPtr<BrowsingContext> mBrowsingContext;
+  RefPtr<EventTarget> mCurrentEventTarget;
+
+  uint32_t mEpoch;
+  nsCOMPtr<nsITimer> mTimer;
+  RefPtr<SessionStoreChild> mSessionStoreChild;
+  SessionStoreChangeTable mSessionStoreChanges;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStoreChangeListener_h
diff --git a/toolkit/components/sessionstore/SessionStoreChild.cpp b/toolkit/components/sessionstore/SessionStoreChild.cpp
new file mode 100644
index 0000000000..0b6d0dd17e
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreChild.cpp
@@ -0,0 +1,261 @@
+/* -*- 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/SessionStoreChild.h"
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/InProcessChild.h"
+#include "mozilla/dom/InProcessParent.h"
+#include "mozilla/dom/BrowserSessionStore.h"
+#include "mozilla/dom/SessionStoreChangeListener.h"
+#include "mozilla/dom/SessionStoreParent.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "nsCOMPtr.h"
+#include "nsFrameLoader.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+class nsIDocShell;
+
+static already_AddRefed<TabListener> CreateTabListener(nsIDocShell* aDocShell) {
+  RefPtr<TabListener> tabListener =
+      mozilla::MakeRefPtr<TabListener>(aDocShell, nullptr);
+  nsresult rv = tabListener->Init();
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  return tabListener.forget();
+}
+
+already_AddRefed<SessionStoreChild> SessionStoreChild::GetOrCreate(
+    BrowsingContext* aBrowsingContext, Element* aOwnerElement) {
+  RefPtr<TabListener> tabListener =
+      CreateTabListener(aBrowsingContext->GetDocShell());
+  if (!tabListener) {
+    return nullptr;
+  }
+
+  RefPtr<SessionStoreChangeListener> sessionStoreChangeListener =
+      SessionStoreChangeListener::Create(aBrowsingContext);
+  if (!sessionStoreChangeListener) {
+    return nullptr;
+  }
+
+  RefPtr<SessionStoreChild> sessionStoreChild =
+      new SessionStoreChild(tabListener, sessionStoreChangeListener);
+
+  sessionStoreChangeListener->SetActor(sessionStoreChild);
+
+  if (XRE_IsParentProcess()) {
+    MOZ_DIAGNOSTIC_ASSERT(aOwnerElement);
+    InProcessChild* inProcessChild = InProcessChild::Singleton();
+    InProcessParent* inProcessParent = InProcessParent::Singleton();
+    if (!inProcessChild || !inProcessParent) {
+      return nullptr;
+    }
+
+    RefPtr<BrowserSessionStore> sessionStore =
+        BrowserSessionStore::GetOrCreate(aBrowsingContext->Canonical()->Top());
+    if (!sessionStore) {
+      return nullptr;
+    }
+
+    CanonicalBrowsingContext* browsingContext = aBrowsingContext->Canonical();
+    RefPtr<SessionStoreParent> sessionStoreParent =
+        new SessionStoreParent(browsingContext, sessionStore);
+    ManagedEndpoint<PSessionStoreParent> endpoint =
+        inProcessChild->OpenPSessionStoreEndpoint(sessionStoreChild);
+    inProcessParent->BindPSessionStoreEndpoint(std::move(endpoint),
+                                               sessionStoreParent);
+  } else {
+    MOZ_DIAGNOSTIC_ASSERT(!aOwnerElement);
+    RefPtr<BrowserChild> browserChild =
+        BrowserChild::GetFrom(aBrowsingContext->GetDOMWindow());
+
+    MOZ_DIAGNOSTIC_ASSERT(browserChild);
+    MOZ_DIAGNOSTIC_ASSERT(aBrowsingContext->IsInProcess());
+    sessionStoreChild = static_cast<SessionStoreChild*>(
+        browserChild->SendPSessionStoreConstructor(sessionStoreChild));
+  }
+
+  return sessionStoreChild.forget();
+}
+
+/* static */
+SessionStoreChild* SessionStoreChild::From(WindowGlobalChild* aWindowChild) {
+  if (!aWindowChild) {
+    return nullptr;
+  }
+
+  // If `aWindowChild` is inprocess
+  if (RefPtr<BrowserChild> browserChild = aWindowChild->GetBrowserChild()) {
+    return browserChild->GetSessionStoreChild();
+  }
+
+  if (XRE_IsContentProcess()) {
+    return nullptr;
+  }
+
+  WindowGlobalParent* windowParent = aWindowChild->WindowContext()->Canonical();
+  if (!windowParent) {
+    return nullptr;
+  }
+
+  RefPtr<nsFrameLoader> frameLoader = windowParent->GetRootFrameLoader();
+  if (!frameLoader) {
+    return nullptr;
+  }
+
+  return frameLoader->GetSessionStoreChild();
+}
+
+SessionStoreChild::SessionStoreChild(
+    TabListener* aSessionStoreListener,
+    SessionStoreChangeListener* aSessionStoreChangeListener)
+    : mSessionStoreListener(aSessionStoreListener),
+      mSessionStoreChangeListener(aSessionStoreChangeListener) {}
+
+void SessionStoreChild::SetEpoch(uint32_t aEpoch) {
+  if (mSessionStoreListener) {
+    mSessionStoreListener->SetEpoch(aEpoch);
+  }
+
+  if (mSessionStoreChangeListener) {
+    mSessionStoreChangeListener->SetEpoch(aEpoch);
+  }
+}
+
+void SessionStoreChild::SetOwnerContent(Element* aElement) {
+  if (mSessionStoreChangeListener) {
+    mSessionStoreChangeListener->FlushSessionStore();
+  }
+
+  if (!aElement) {
+    return;
+  }
+
+  if (mSessionStoreListener) {
+    mSessionStoreListener->SetOwnerContent(aElement);
+  }
+}
+
+void SessionStoreChild::Stop() {
+  if (mSessionStoreListener) {
+    mSessionStoreListener->RemoveListeners();
+    mSessionStoreListener = nullptr;
+  }
+
+  if (mSessionStoreChangeListener) {
+    mSessionStoreChangeListener->Stop();
+  }
+}
+
+void SessionStoreChild::UpdateEventTargets() {
+  if (mSessionStoreChangeListener) {
+    mSessionStoreChangeListener->UpdateEventTargets();
+  }
+}
+
+void SessionStoreChild::UpdateSessionStore(bool aSessionHistoryUpdate,
+                                           const MaybeSessionStoreZoom& aZoom) {
+  if (!mSessionStoreListener) {
+    // This is the case when we're shutting down, and expect a final update.
+    SessionStoreUpdate(Nothing(), Nothing(), Nothing(), aSessionHistoryUpdate,
+                       0);
+    return;
+  }
+
+  RefPtr<ContentSessionStore> store = mSessionStoreListener->GetSessionStore();
+
+  Maybe<nsCString> docShellCaps;
+  if (store->IsDocCapChanged()) {
+    docShellCaps.emplace(store->GetDocShellCaps());
+  }
+
+  Maybe<bool> privatedMode;
+  if (store->IsPrivateChanged()) {
+    privatedMode.emplace(store->GetPrivateModeEnabled());
+  }
+
+  SessionStoreUpdate(
+      docShellCaps, privatedMode, aZoom,
+      store->GetAndClearSHistoryChanged() || aSessionHistoryUpdate,
+      mSessionStoreListener->GetEpoch());
+}
+
+void SessionStoreChild::FlushSessionStore() {
+  if (mSessionStoreChangeListener) {
+    mSessionStoreChangeListener->FlushSessionStore();
+  }
+}
+
+void SessionStoreChild::UpdateSHistoryChanges() {
+  if (mSessionStoreListener) {
+    mSessionStoreListener->UpdateSHistoryChanges();
+  }
+}
+
+mozilla::ipc::IPCResult SessionStoreChild::RecvFlushTabState(
+    FlushTabStateResolver&& aResolver) {
+  if (mSessionStoreChangeListener) {
+    mSessionStoreChangeListener->FlushSessionStore();
+  }
+  aResolver(true);
+
+  return IPC_OK();
+}
+
+void SessionStoreChild::SessionStoreUpdate(
+    const Maybe<nsCString>& aDocShellCaps, const Maybe<bool>& aPrivatedMode,
+    const MaybeSessionStoreZoom& aZoom, const bool aNeedCollectSHistory,
+    const uint32_t& aEpoch) {
+  if (XRE_IsContentProcess()) {
+    Unused << SendSessionStoreUpdate(aDocShellCaps, aPrivatedMode, aZoom,
+                                     aNeedCollectSHistory, aEpoch);
+  } else if (SessionStoreParent* sessionStoreParent =
+                 static_cast<SessionStoreParent*>(
+                     InProcessChild::ParentActorFor(this))) {
+    sessionStoreParent->SessionStoreUpdate(aDocShellCaps, aPrivatedMode, aZoom,
+                                           aNeedCollectSHistory, aEpoch);
+  }
+}
+
+void SessionStoreChild::IncrementalSessionStoreUpdate(
+    const MaybeDiscarded<BrowsingContext>& aBrowsingContext,
+    const Maybe<FormData>& aFormData, const Maybe<nsPoint>& aScrollPosition,
+    uint32_t aEpoch) {
+  if (XRE_IsContentProcess()) {
+    Unused << SendIncrementalSessionStoreUpdate(aBrowsingContext, aFormData,
+                                                aScrollPosition, aEpoch);
+  } else if (SessionStoreParent* sessionStoreParent =
+                 static_cast<SessionStoreParent*>(
+                     InProcessChild::ParentActorFor(this))) {
+    sessionStoreParent->IncrementalSessionStoreUpdate(
+        aBrowsingContext, aFormData, aScrollPosition, aEpoch);
+  }
+}
+
+void SessionStoreChild::ResetSessionStore(
+    const MaybeDiscarded<BrowsingContext>& aBrowsingContext, uint32_t aEpoch) {
+  if (XRE_IsContentProcess()) {
+    Unused << SendResetSessionStore(aBrowsingContext, aEpoch);
+  } else if (SessionStoreParent* sessionStoreParent =
+                 static_cast<SessionStoreParent*>(
+                     InProcessChild::ParentActorFor(this))) {
+    sessionStoreParent->ResetSessionStore(aBrowsingContext, aEpoch);
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION(SessionStoreChild, mSessionStoreListener,
+                         mSessionStoreChangeListener)
diff --git a/toolkit/components/sessionstore/SessionStoreChild.h b/toolkit/components/sessionstore/SessionStoreChild.h
new file mode 100644
index 0000000000..606aa0f441
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreChild.h
@@ -0,0 +1,73 @@
+/* -*- 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_SessionStoreChild_h
+#define mozilla_dom_SessionStoreChild_h
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/dom/PSessionStoreChild.h"
+#include "mozilla/dom/SessionStoreScrollData.h"
+#include "mozilla/dom/SessionStoreChangeListener.h"
+#include "mozilla/dom/SessionStoreListener.h"
+#include "mozilla/RefPtr.h"
+
+#include "nsCycleCollectionParticipant.h"
+
+namespace mozilla::dom {
+class BrowsingContext;
+class SessionStoreChangeListener;
+class TabListener;
+
+class SessionStoreChild final : public PSessionStoreChild {
+ public:
+  static already_AddRefed<SessionStoreChild> GetOrCreate(
+      BrowsingContext* aBrowsingContext, Element* aOwnerElement = nullptr);
+
+  static SessionStoreChild* From(WindowGlobalChild* aWindowChild);
+
+  void SetEpoch(uint32_t aEpoch);
+  void SetOwnerContent(Element* aElement);
+  void Stop();
+  void UpdateEventTargets();
+  void UpdateSessionStore(bool aSessionHistoryUpdate = false,
+                          const MaybeSessionStoreZoom& aZoom = Nothing());
+  void FlushSessionStore();
+  void UpdateSHistoryChanges();
+
+  void SessionStoreUpdate(const Maybe<nsCString>& aDocShellCaps,
+                          const Maybe<bool>& aPrivatedMode,
+                          const MaybeSessionStoreZoom& aZoom,
+                          const bool aNeedCollectSHistory,
+                          const uint32_t& aEpoch);
+
+  void IncrementalSessionStoreUpdate(
+      const MaybeDiscarded<BrowsingContext>& aBrowsingContext,
+      const Maybe<FormData>& aFormData, const Maybe<nsPoint>& aScrollPosition,
+      uint32_t aEpoch);
+
+  void ResetSessionStore(
+      const MaybeDiscarded<BrowsingContext>& aBrowsingContext, uint32_t aEpoch);
+
+  SessionStoreChangeListener* GetSessionStoreChangeListener() const {
+    return mSessionStoreChangeListener;
+  }
+
+  mozilla::ipc::IPCResult RecvFlushTabState(FlushTabStateResolver&& aResolver);
+
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(SessionStoreChild)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(SessionStoreChild)
+
+ private:
+  SessionStoreChild(TabListener* aSessionStoreListener,
+                    SessionStoreChangeListener* aSessionStoreChangeListener);
+  ~SessionStoreChild() = default;
+
+  RefPtr<TabListener> mSessionStoreListener;
+  RefPtr<SessionStoreChangeListener> mSessionStoreChangeListener;
+};
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStoreChild_h
diff --git a/toolkit/components/sessionstore/SessionStoreData.h b/toolkit/components/sessionstore/SessionStoreData.h
new file mode 100644
index 0000000000..0df1ea5bf5
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreData.h
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; 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/. */
+
+#ifndef mozilla_dom_SessionStoreData_h
+#define mozilla_dom_SessionStoreData_h
+
+#include "nsString.h"
+#include "nsTArray.h"
+#include "mozilla/dom/SessionStoreUtilsBinding.h"
+#include "mozilla/Variant.h"
+
+typedef mozilla::Variant<nsString, bool,
+                         mozilla::dom::CollectedNonMultipleSelectValue,
+                         CopyableTArray<nsString>>
+    InputDataValue;
+
+/*
+ * Need two arrays based on this struct.
+ * One is for elements with id one is for XPath.
+ *
+ * id:      id or XPath
+ * type:    type of this input element
+ *        bool:   value is boolean
+ *        string: value is nsString
+ *        file:   value is "arrayVal"
+ *        singleSelect:   value is "singleSelect"
+ *        multipleSelect: value is "arrayVal"
+ *
+ * There are four value types:
+ * strVal:        nsString
+ * boolVal:       boolean
+ * singleSelect:  single select value
+ * arrayVal:      nsString array
+ */
+struct CollectedInputDataValue {
+  nsString id;
+  nsString type;
+  InputDataValue value{false};
+
+  CollectedInputDataValue() = default;
+};
+
+/*
+ * Each index of the following array is corresponging to each frame.
+ * descendants: number of child frames of this frame
+ * innerHTML:   innerHTML of this frame
+ * url:         url of this frame
+ * numId:       number of containing elements with id for this frame
+ * numXPath:    number of containing elements with XPath for this frame
+ */
+struct InputFormData {
+  int32_t descendants;
+  nsString innerHTML;
+  nsCString url;
+  int32_t numId;
+  int32_t numXPath;
+};
+
+#endif /* mozilla_dom_SessionStoreData_h */
diff --git a/toolkit/components/sessionstore/SessionStoreFormData.cpp b/toolkit/components/sessionstore/SessionStoreFormData.cpp
new file mode 100644
index 0000000000..c792b3f2f0
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreFormData.cpp
@@ -0,0 +1,172 @@
+/* -*- 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/SessionStoreFormData.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/BrowserSessionStoreBinding.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/sessionstore/SessionStoreTypes.h"
+
+#include "nsContentUtils.h"
+#include "js/JSON.h"
+
+using namespace mozilla::dom;
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(SessionStoreFormData)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(SessionStoreFormData)
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_WEAK_PTR(SessionStoreFormData, mChildren)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SessionStoreFormData)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+nsISupports* SessionStoreFormData::GetParentObject() const {
+  return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
+}
+
+JSObject* SessionStoreFormData::WrapObject(JSContext* aCx,
+                                           JS::Handle<JSObject*> aGivenProto) {
+  return SessionStoreFormData_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void SessionStoreFormData::GetUrl(nsACString& aUrl) const {
+  if (mUrl.IsEmpty()) {
+    aUrl.SetIsVoid(true);
+  } else {
+    aUrl = mUrl;
+  }
+}
+
+void SessionStoreFormData::GetId(
+    JSContext* aCx,
+    Nullable<Record<nsString, OwningStringOrBooleanOrObject>>& aId) {
+  if (mId.IsEmpty() ||
+      NS_FAILED(SessionStoreUtils::ConstructFormDataValues(
+          aCx, mId, aId.SetValue().Entries(), mParseSessionData))) {
+    aId.SetNull();
+  }
+
+  // SessionStoreFormData.id is now stored in a slot, so we can free our
+  // internal state.
+  mId.Clear();
+}
+
+void SessionStoreFormData::GetXpath(
+    JSContext* aCx,
+    Nullable<Record<nsString, OwningStringOrBooleanOrObject>>& aXpath) {
+  if (mXpath.IsEmpty() ||
+      NS_FAILED(SessionStoreUtils::ConstructFormDataValues(
+          aCx, mXpath, aXpath.SetValue().Entries(), mParseSessionData))) {
+    aXpath.SetNull();
+  }
+
+  // SessionStoreFormData.xpath is now stored in a slot, so we can free our
+  // internal state.
+  mXpath.Clear();
+}
+
+void SessionStoreFormData::GetInnerHTML(nsAString& aInnerHTML) {
+  if (mInnerHTML.IsEmpty()) {
+    SetDOMStringToNull(aInnerHTML);
+  } else {
+    aInnerHTML = mInnerHTML;
+  }
+
+  // SessionStoreFormData.innerHTML is now stored in a slot, so we can free our
+  // internal state.
+  mInnerHTML.SetIsVoid(true);
+}
+
+SessionStoreFormData::ChildrenArray& SessionStoreFormData::Children() {
+  return mChildren;
+}
+
+void SessionStoreFormData::GetChildren(
+    Nullable<ChildrenArray>& aChildren) const {
+  if (!mChildren.IsEmpty()) {
+    aChildren.SetValue() = mChildren.Clone();
+  } else {
+    aChildren.SetNull();
+  }
+}
+
+void SessionStoreFormData::ToJSON(JSContext* aCx,
+                                  JS::MutableHandle<JSObject*> aRetval) {
+  JS::Rooted<JSObject*> self(aCx);
+  {
+    JS::Rooted<JS::Value> value(aCx);
+    if (!GetOrCreateDOMReflector(aCx, this, &value)) {
+      return;
+    }
+
+    self.set(value.toObjectOrNull());
+  }
+
+  JS::Rooted<JSObject*> result(aCx, JS_NewPlainObject(aCx));
+
+  if (!IsEmpty()) {
+    for (const auto& name :
+         {u"url"_ns, u"id"_ns, u"xpath"_ns, u"innerHTML"_ns}) {
+      if (!SessionStoreUtils::CopyProperty(aCx, result, self, name)) {
+        return;
+      }
+    }
+
+    SessionStoreUtils::CopyChildren(aCx, result, mChildren);
+  }
+
+  aRetval.set(result);
+}
+
+void SessionStoreFormData::Update(const CollectedType& aFormData) {
+  SessionStoreFormData_Binding::ClearCachedUrlValue(this);
+  SessionStoreFormData_Binding::ClearCachedIdValue(this);
+  SessionStoreFormData_Binding::ClearCachedXpathValue(this);
+  SessionStoreFormData_Binding::ClearCachedInnerHTMLValue(this);
+
+  if (!aFormData.hasData()) {
+    mParseSessionData = false;
+    mHasData = false;
+    mUrl = ""_ns;
+    mId.Clear();
+    mXpath.Clear();
+    mInnerHTML = u""_ns;
+
+    return;
+  }
+
+  mHasData = true;
+
+  mUrl = aFormData.uri();
+  // We want to avoid saving data for about:sessionrestore as a string.
+  // Since it's stored in the form as stringified JSON, stringifying
+  // further causes an explosion of escape characters. cf. bug 467409
+  mParseSessionData =
+      mUrl == "about:sessionrestore"_ns || mUrl == "about:welcomeback"_ns;
+
+  mInnerHTML = aFormData.innerHTML();
+
+  mId.Assign(aFormData.id());
+  mXpath.Assign(aFormData.xpath());
+}
+
+void SessionStoreFormData::ClearCachedChildren() {
+  SessionStoreFormData_Binding::ClearCachedChildrenValue(this);
+}
+
+/* static */ bool SessionStoreFormData::HasData(
+    const CollectedType& aFormData) {
+  return aFormData.hasData();
+}
+
+bool SessionStoreFormData::IsEmpty() const {
+  return !mHasData && mChildren.IsEmpty();
+}
diff --git a/toolkit/components/sessionstore/SessionStoreFormData.h b/toolkit/components/sessionstore/SessionStoreFormData.h
new file mode 100644
index 0000000000..0466d98441
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreFormData.h
@@ -0,0 +1,83 @@
+/* -*- 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_SessionStoreFormData_h
+#define mozilla_dom_SessionStoreFormData_h
+
+#include "mozilla/WeakPtr.h"
+#include "mozilla/dom/UnionTypes.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+
+#include "nsTArrayForwardDeclare.h"
+#include "nsWrapperCache.h"
+
+class nsIGlobalObject;
+
+namespace mozilla::dom {
+
+namespace sessionstore {
+class FormData;
+}
+
+class BrowsingContext;
+class OwningByteStringOrObjectOrNull;
+class OwningStringOrObjectOrNull;
+class WindowGlobalParent;
+
+class SessionStoreFormData final : public nsISupports,
+                                   public nsWrapperCache,
+                                   public SupportsWeakPtr {
+ public:
+  using CollectedType = sessionstore::FormData;
+  using LocationType = WeakPtr<SessionStoreFormData>;
+  using ChildrenArray = nsTArray<RefPtr<SessionStoreFormData>>;
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(SessionStoreFormData)
+  nsISupports* GetParentObject() const;
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  void GetUrl(nsACString& aUrl) const;
+
+  void GetId(JSContext* aCx,
+             Nullable<Record<nsString, OwningStringOrBooleanOrObject>>& aId);
+
+  void GetXpath(
+      JSContext* aCx,
+      Nullable<Record<nsString, OwningStringOrBooleanOrObject>>& aXpath);
+
+  void GetInnerHTML(nsAString& aInnerHTML);
+
+  ChildrenArray& Children();
+
+  void GetChildren(Nullable<ChildrenArray>& aChildren) const;
+
+  void ToJSON(JSContext* aCx, JS::MutableHandle<JSObject*> aRetval);
+
+  void Update(const CollectedType& aFormData);
+
+  void ClearCachedChildren();
+
+  static bool HasData(const CollectedType& aFormData);
+
+  bool IsEmpty() const;
+
+ private:
+  ~SessionStoreFormData() = default;
+
+  bool mParseSessionData = false;
+  bool mHasData = false;
+  nsCString mUrl;
+  nsTArray<sessionstore::FormEntry> mId;
+  nsTArray<sessionstore::FormEntry> mXpath;
+  nsString mInnerHTML;
+  ChildrenArray mChildren;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStoreFormData_h
diff --git a/toolkit/components/sessionstore/SessionStoreFunctions.idl b/toolkit/components/sessionstore/SessionStoreFunctions.idl
new file mode 100644
index 0000000000..3c17015437
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreFunctions.idl
@@ -0,0 +1,23 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 8 -*- */
+/* 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 BrowsingContext;
+webidl Element;
+
+[scriptable, uuid(1A060FBA-A19D-11E9-B7EB-580D0EDD8E6F)]
+interface nsISessionStoreFunctions : nsISupports {
+  // update sessionStore from the tabListener implemented by C++
+  // aData is a UpdateSessionStoreData dictionary (From SessionStoreUtils.webidl)
+  void UpdateSessionStore(
+    in Element aBrowser, in BrowsingContext aBrowsingContext,
+    in jsval aPermanentKey, in uint32_t aEpoch, in boolean aCollectSHistory,
+    in jsval aData);
+
+  void UpdateSessionStoreForStorage(
+    in Element aBrowser, in BrowsingContext aBrowsingContext,
+    in jsval aPermanentKey, in uint32_t aEpoch, in jsval aData);
+};
diff --git a/toolkit/components/sessionstore/SessionStoreFunctions.sys.mjs b/toolkit/components/sessionstore/SessionStoreFunctions.sys.mjs
new file mode 100644
index 0000000000..f42c371264
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreFunctions.sys.mjs
@@ -0,0 +1,87 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 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/. */
+import { SessionStore } from "resource:///modules/sessionstore/SessionStore.sys.mjs";
+
+export function UpdateSessionStore(
+  aBrowser,
+  aBrowsingContext,
+  aPermanentKey,
+  aEpoch,
+  aCollectSHistory,
+  aData
+) {
+  return SessionStoreFuncInternal.updateSessionStore(
+    aBrowser,
+    aBrowsingContext,
+    aPermanentKey,
+    aEpoch,
+    aCollectSHistory,
+    aData
+  );
+}
+
+export function UpdateSessionStoreForStorage(
+  aBrowser,
+  aBrowsingContext,
+  aPermanentKey,
+  aEpoch,
+  aData
+) {
+  return SessionStoreFuncInternal.updateSessionStoreForStorage(
+    aBrowser,
+    aBrowsingContext,
+    aPermanentKey,
+    aEpoch,
+    aData
+  );
+}
+
+var SessionStoreFuncInternal = {
+  updateSessionStore: function SSF_updateSessionStore(
+    aBrowser,
+    aBrowsingContext,
+    aPermanentKey,
+    aEpoch,
+    aCollectSHistory,
+    aData
+  ) {
+    let { formdata, scroll } = aData;
+
+    if (formdata) {
+      aData.formdata = formdata.toJSON();
+    }
+
+    if (scroll) {
+      aData.scroll = scroll.toJSON();
+    }
+
+    SessionStore.updateSessionStoreFromTablistener(
+      aBrowser,
+      aBrowsingContext,
+      aPermanentKey,
+      {
+        data: aData,
+        epoch: aEpoch,
+        sHistoryNeeded: aCollectSHistory,
+      }
+    );
+  },
+
+  updateSessionStoreForStorage: function SSF_updateSessionStoreForStorage(
+    aBrowser,
+    aBrowsingContext,
+    aPermanentKey,
+    aEpoch,
+    aData
+  ) {
+    SessionStore.updateSessionStoreFromTablistener(
+      aBrowser,
+      aBrowsingContext,
+      aPermanentKey,
+      { data: { storage: aData }, epoch: aEpoch },
+      true
+    );
+  },
+};
diff --git a/toolkit/components/sessionstore/SessionStoreListener.cpp b/toolkit/components/sessionstore/SessionStoreListener.cpp
new file mode 100644
index 0000000000..19612af786
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreListener.cpp
@@ -0,0 +1,494 @@
+/* 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/PresShell.h"
+#include "mozilla/dom/BrowserSessionStoreBinding.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/SessionStoreListener.h"
+#include "mozilla/dom/SessionStoreUtils.h"
+#include "mozilla/dom/SessionStoreUtilsBinding.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "nsGenericHTMLElement.h"
+#include "nsDocShell.h"
+#include "nsIAppWindow.h"
+#include "nsIDocShell.h"
+#include "nsIDocShellTreeOwner.h"
+#include "nsImportModule.h"
+#include "nsIPrefBranch.h"
+#include "nsIPrefService.h"
+#include "nsITimer.h"
+#include "nsIWebProgress.h"
+#include "nsIXPConnect.h"
+#include "nsIXULRuntime.h"
+#include "nsPresContext.h"
+#include "nsPrintfCString.h"
+#include "SessionStoreFunctions.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// This pref controls whether or not we send updates to the parent on a timeout
+// or not, and should only be used for tests or debugging.
+static const char kTimeOutDisable[] =
+    "browser.sessionstore.debug.no_auto_updates";
+// Timeout for waiting an idle period to send data.
+static const char kPrefInterval[] = "browser.sessionstore.interval";
+
+NS_IMPL_CYCLE_COLLECTION(ContentSessionStore, mDocShell)
+
+ContentSessionStore::ContentSessionStore(nsIDocShell* aDocShell)
+    : mDocShell(aDocShell),
+      mPrivateChanged(false),
+      mIsPrivate(false),
+      mDocCapChanged(false),
+      mSHistoryChanged(false) {
+  MOZ_ASSERT(mDocShell);
+  // Check that value at startup as it might have
+  // been set before the frame script was loaded.
+  if (NS_SUCCEEDED(nsDocShell::Cast(mDocShell)->GetUsePrivateBrowsing(
+          &mPrivateChanged)) &&
+      mPrivateChanged) {
+    mIsPrivate = true;
+  }
+}
+
+nsCString ContentSessionStore::CollectDocShellCapabilities() {
+  bool allow;
+  nsCString aRetVal;
+
+#define TRY_ALLOWPROP(y)                        \
+  PR_BEGIN_MACRO                                \
+  nsresult rv = mDocShell->GetAllow##y(&allow); \
+  if (NS_SUCCEEDED(rv) && !allow) {             \
+    if (!aRetVal.IsEmpty()) {                   \
+      aRetVal.Append(',');                      \
+    }                                           \
+    aRetVal.Append(#y);                         \
+  }                                             \
+  PR_END_MACRO
+
+  TRY_ALLOWPROP(Plugins);
+  // Bug 1328013 : Don't collect "AllowJavascript" property
+  // TRY_ALLOWPROP(Javascript);
+  TRY_ALLOWPROP(MetaRedirects);
+  TRY_ALLOWPROP(Subframes);
+  TRY_ALLOWPROP(Images);
+  TRY_ALLOWPROP(Media);
+  TRY_ALLOWPROP(DNSPrefetch);
+  TRY_ALLOWPROP(WindowControl);
+  TRY_ALLOWPROP(Auth);
+  TRY_ALLOWPROP(ContentRetargeting);
+  TRY_ALLOWPROP(ContentRetargetingOnChildren);
+#undef TRY_ALLOWPROP
+  return aRetVal;
+}
+
+void ContentSessionStore::OnPrivateModeChanged(bool aEnabled) {
+  mPrivateChanged = true;
+  mIsPrivate = aEnabled;
+}
+
+nsCString ContentSessionStore::GetDocShellCaps() {
+  mDocCapChanged = false;
+  return mDocCaps;
+}
+
+bool ContentSessionStore::GetPrivateModeEnabled() {
+  mPrivateChanged = false;
+  return mIsPrivate;
+}
+
+void ContentSessionStore::SetSHistoryChanged() {
+  mSHistoryChanged = mozilla::SessionHistoryInParent();
+}
+
+void ContentSessionStore::OnDocumentStart() {
+  nsCString caps = CollectDocShellCapabilities();
+  if (!mDocCaps.Equals(caps)) {
+    mDocCaps = caps;
+    mDocCapChanged = true;
+  }
+
+  if (mozilla::SessionHistoryInParent()) {
+    mSHistoryChanged = true;
+  }
+}
+
+void ContentSessionStore::OnDocumentEnd() {
+  if (mozilla::SessionHistoryInParent()) {
+    mSHistoryChanged = true;
+  }
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(TabListener)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMEventListener)
+  NS_INTERFACE_MAP_ENTRY(nsIObserver)
+  NS_INTERFACE_MAP_ENTRY(nsIPrivacyTransitionObserver)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMEventListener)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION_WEAK(TabListener, mDocShell, mSessionStore,
+                              mOwnerContent)
+NS_IMPL_CYCLE_COLLECTING_ADDREF(TabListener)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(TabListener)
+
+TabListener::TabListener(nsIDocShell* aDocShell, Element* aElement)
+    : mDocShell(aDocShell),
+      mSessionStore(new ContentSessionStore(aDocShell)),
+      mOwnerContent(aElement),
+      mProgressListenerRegistered(false),
+      mEventListenerRegistered(false),
+      mPrefObserverRegistered(false),
+      mUpdatedTimer(nullptr),
+      mTimeoutDisabled(false),
+      mUpdateInterval(15000),
+      mEpoch(0) {
+  MOZ_ASSERT(mDocShell);
+}
+
+EventTarget* TabListener::GetEventTarget() {
+  if (mOwnerContent) {
+    return mOwnerContent;
+  }
+
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(mDocShell);
+  if (window) {
+    return window->GetChromeEventHandler();
+  }
+
+  return nullptr;
+}
+
+nsresult TabListener::Init() {
+  TabListener::UpdateSessionStore();
+  nsresult rv = mDocShell->AddWeakPrivacyTransitionObserver(this);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIWebProgress> webProgress = do_QueryInterface(mDocShell);
+  rv = webProgress->AddProgressListener(this,
+                                        nsIWebProgress::NOTIFY_STATE_DOCUMENT);
+  NS_ENSURE_SUCCESS(rv, rv);
+  mProgressListenerRegistered = true;
+
+  nsCOMPtr<nsIPrefBranch> prefBranch = do_GetService(NS_PREFSERVICE_CONTRACTID);
+  NS_WARNING_ASSERTION(prefBranch, "no prefservice");
+  if (prefBranch) {
+    prefBranch->AddObserver(kTimeOutDisable, this, true);
+    prefBranch->AddObserver(kPrefInterval, this, true);
+    mPrefObserverRegistered = true;
+  }
+
+  AddEventListeners();
+  return NS_OK;
+}
+
+void TabListener::AddEventListeners() {
+  if (nsCOMPtr<EventTarget> eventTarget = GetEventTarget()) {
+    if (mozilla::SessionHistoryInParent()) {
+      eventTarget->AddSystemEventListener(u"DOMTitleChanged"_ns, this, false);
+    }
+    mEventListenerRegistered = true;
+  }
+}
+
+void TabListener::RemoveEventListeners() {
+  if (nsCOMPtr<EventTarget> eventTarget = GetEventTarget()) {
+    if (mEventListenerRegistered) {
+      if (mozilla::SessionHistoryInParent()) {
+        eventTarget->RemoveSystemEventListener(u"DOMTitleChanged"_ns, this,
+                                               false);
+      }
+      mEventListenerRegistered = false;
+    }
+  }
+}
+
+void TabListener::SetOwnerContent(Element* aElement) {
+  MOZ_DIAGNOSTIC_ASSERT(aElement);
+  RemoveEventListeners();
+  mOwnerContent = aElement;
+  AddEventListeners();
+}
+
+/* static */
+void TabListener::TimerCallback(nsITimer* aTimer, void* aClosure) {
+  auto listener = static_cast<TabListener*>(aClosure);
+  listener->UpdateSessionStore();
+  listener->StopTimerForUpdate();
+}
+
+void TabListener::StopTimerForUpdate() {
+  if (mUpdatedTimer) {
+    mUpdatedTimer->Cancel();
+    mUpdatedTimer = nullptr;
+  }
+}
+
+void TabListener::AddTimerForUpdate() {
+  if (mUpdatedTimer) {
+    return;
+  }
+
+  if (mTimeoutDisabled) {
+    UpdateSessionStore();
+    return;
+  }
+
+  NS_NewTimerWithFuncCallback(getter_AddRefs(mUpdatedTimer), TimerCallback,
+                              this, mUpdateInterval, nsITimer::TYPE_ONE_SHOT,
+                              "TabListener::TimerCallback");
+}
+
+NS_IMETHODIMP TabListener::PrivateModeChanged(bool aEnabled) {
+  mSessionStore->OnPrivateModeChanged(aEnabled);
+  AddTimerForUpdate();
+  return NS_OK;
+}
+
+NS_IMETHODIMP TabListener::OnStateChange(nsIWebProgress* aWebProgress,
+                                         nsIRequest* aRequest,
+                                         uint32_t aStateFlags,
+                                         nsresult aStatus) {
+  if (!mSessionStore) {
+    return NS_OK;
+  }
+
+  // Ignore state changes for subframes because we're only interested in the
+  // top-document starting or stopping its load.
+  bool isTopLevel = false;
+  nsresult rv = aWebProgress->GetIsTopLevel(&isTopLevel);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (!isTopLevel) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIWebProgress> webProgress = do_QueryInterface(mDocShell);
+  if (webProgress != aWebProgress) {
+    return NS_OK;
+  }
+
+  // onStateChange will be fired when loading the initial about:blank URI for
+  // a browser, which we don't actually care about. This is particularly for
+  // the case of unrestored background tabs, where the content has not yet
+  // been restored: we don't want to accidentally send any updates to the
+  // parent when the about:blank placeholder page has loaded.
+  if (!mDocShell->GetHasLoadedNonBlankURI()) {
+    return NS_OK;
+  }
+
+  if (aStateFlags & (nsIWebProgressListener::STATE_START)) {
+    mSessionStore->OnDocumentStart();
+  } else if (aStateFlags & (nsIWebProgressListener::STATE_STOP)) {
+    mSessionStore->OnDocumentEnd();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TabListener::HandleEvent(Event* aEvent) {
+  EventTarget* target = aEvent->GetTarget();
+  if (!target) {
+    return NS_OK;
+  }
+
+  nsPIDOMWindowOuter* outer = target->GetOwnerGlobalForBindingsInternal();
+  if (!outer || !outer->GetDocShell()) {
+    return NS_OK;
+  }
+
+  RefPtr<BrowsingContext> context = outer->GetBrowsingContext();
+  if (!context || context->CreatedDynamically()) {
+    return NS_OK;
+  }
+
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+  if (eventType.EqualsLiteral("DOMTitleChanged")) {
+    mSessionStore->SetSHistoryChanged();
+    AddTimerForUpdate();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP TabListener::OnProgressChange(nsIWebProgress* aWebProgress,
+                                            nsIRequest* aRequest,
+                                            int32_t aCurSelfProgress,
+                                            int32_t aMaxSelfProgress,
+                                            int32_t aCurTotalProgress,
+                                            int32_t aMaxTotalProgress) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP TabListener::OnLocationChange(nsIWebProgress* aWebProgress,
+                                            nsIRequest* aRequest,
+                                            nsIURI* aLocation,
+                                            uint32_t aFlags) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP TabListener::OnStatusChange(nsIWebProgress* aWebProgress,
+                                          nsIRequest* aRequest,
+                                          nsresult aStatus,
+                                          const char16_t* aMessage) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+NS_IMETHODIMP TabListener::OnSecurityChange(nsIWebProgress* aWebProgress,
+                                            nsIRequest* aRequest,
+                                            uint32_t aState) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+NS_IMETHODIMP TabListener::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                                  nsIRequest* aRequest,
+                                                  uint32_t aEvent) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult TabListener::Observe(nsISupports* aSubject, const char* aTopic,
+                              const char16_t* aData) {
+  if (!strcmp(aTopic, NS_PREFBRANCH_PREFCHANGE_TOPIC_ID)) {
+    nsCOMPtr<nsIPrefBranch> prefBranch = do_QueryInterface(aSubject);
+
+    bool timeoutDisabled;
+    if (NS_SUCCEEDED(
+            prefBranch->GetBoolPref(kTimeOutDisable, &timeoutDisabled))) {
+      if (mTimeoutDisabled != timeoutDisabled) {
+        mTimeoutDisabled = timeoutDisabled;
+        if (mUpdatedTimer) {
+          StopTimerForUpdate();
+          AddTimerForUpdate();
+        }
+      }
+    }
+
+    int32_t interval = 0;
+    if (NS_SUCCEEDED(prefBranch->GetIntPref(kPrefInterval, &interval))) {
+      if (mUpdateInterval != interval) {
+        mUpdateInterval = interval;
+        if (mUpdatedTimer) {
+          StopTimerForUpdate();
+          AddTimerForUpdate();
+        }
+      }
+    }
+    return NS_OK;
+  }
+
+  NS_ERROR("Unexpected topic");
+  return NS_ERROR_UNEXPECTED;
+}
+
+void TabListener::ForceFlushFromParent() {
+  if (!XRE_IsParentProcess()) {
+    return;
+  }
+  if (!mSessionStore) {
+    return;
+  }
+
+  UpdateSessionStore(true);
+}
+
+void TabListener::UpdateSessionStore(bool aIsFlush) {
+  if (!aIsFlush) {
+    if (!mSessionStore || !mSessionStore->UpdateNeeded()) {
+      return;
+    }
+  }
+
+  if (!XRE_IsParentProcess()) {
+    BrowserChild* browserChild = BrowserChild::GetFrom(mDocShell);
+    if (browserChild) {
+      StopTimerForUpdate();
+      browserChild->UpdateSessionStore();
+    }
+    return;
+  }
+
+  BrowsingContext* context = mDocShell->GetBrowsingContext();
+  if (!context) {
+    return;
+  }
+
+  uint32_t chromeFlags = 0;
+  nsCOMPtr<nsIDocShellTreeOwner> treeOwner;
+  mDocShell->GetTreeOwner(getter_AddRefs(treeOwner));
+  if (!treeOwner) {
+    return;
+  }
+  nsCOMPtr<nsIAppWindow> window(do_GetInterface(treeOwner));
+  if (!window) {
+    return;
+  }
+  if (window && NS_FAILED(window->GetChromeFlags(&chromeFlags))) {
+    return;
+  }
+
+  UpdateSessionStoreData data;
+  if (mSessionStore->IsDocCapChanged()) {
+    data.mDisallow.Construct() = mSessionStore->GetDocShellCaps();
+  }
+  if (mSessionStore->IsPrivateChanged()) {
+    data.mIsPrivate.Construct() = mSessionStore->GetPrivateModeEnabled();
+  }
+
+  nsCOMPtr<nsISessionStoreFunctions> funcs = do_ImportESModule(
+      "resource://gre/modules/SessionStoreFunctions.sys.mjs", fallible);
+  nsCOMPtr<nsIXPConnectWrappedJS> wrapped = do_QueryInterface(funcs);
+  if (!wrapped) {
+    return;
+  }
+
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(wrapped->GetJSObjectGlobal())) {
+    return;
+  }
+
+  JS::Rooted<JS::Value> update(jsapi.cx());
+  if (!ToJSValue(jsapi.cx(), data, &update)) {
+    return;
+  }
+
+  JS::Rooted<JS::Value> key(jsapi.cx(),
+                            context->Canonical()->Top()->PermanentKey());
+
+  nsresult rv = funcs->UpdateSessionStore(
+      mOwnerContent, context, key, mEpoch,
+      mSessionStore->GetAndClearSHistoryChanged(), update);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  StopTimerForUpdate();
+}
+
+void TabListener::RemoveListeners() {
+  if (mProgressListenerRegistered) {
+    nsCOMPtr<nsIWebProgress> webProgress = do_QueryInterface(mDocShell);
+    if (webProgress) {
+      webProgress->RemoveProgressListener(this);
+      mProgressListenerRegistered = false;
+    }
+  }
+
+  RemoveEventListeners();
+
+  if (mPrefObserverRegistered) {
+    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+    if (!obs) {
+      return;
+    }
+    if (mPrefObserverRegistered) {
+      obs->RemoveObserver(this, kTimeOutDisable);
+      obs->RemoveObserver(this, kPrefInterval);
+      mPrefObserverRegistered = false;
+    }
+  }
+}
+
+TabListener::~TabListener() { RemoveListeners(); }
diff --git a/toolkit/components/sessionstore/SessionStoreListener.h b/toolkit/components/sessionstore/SessionStoreListener.h
new file mode 100644
index 0000000000..2cd35a00f5
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreListener.h
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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_SessionStoreListener_h
+#define mozilla_dom_SessionStoreListener_h
+
+#include "SessionStoreData.h"
+#include "nsIDOMEventListener.h"
+#include "nsIObserver.h"
+#include "nsIPrivacyTransitionObserver.h"
+#include "nsIWebProgressListener.h"
+#include "nsWeakReference.h"
+
+class nsITimer;
+
+namespace mozilla::dom {
+
+class ContentSessionStore {
+ public:
+  explicit ContentSessionStore(nsIDocShell* aDocShell);
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(ContentSessionStore)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(ContentSessionStore)
+
+  void OnPrivateModeChanged(bool aEnabled);
+  bool IsDocCapChanged() { return mDocCapChanged; }
+  nsCString GetDocShellCaps();
+  bool IsPrivateChanged() { return mPrivateChanged; }
+  bool GetPrivateModeEnabled();
+
+  void SetSHistoryChanged();
+  // request "collect sessionHistory" which is happened in the parent process
+  bool GetAndClearSHistoryChanged() {
+    bool ret = mSHistoryChanged;
+    mSHistoryChanged = false;
+    return ret;
+  }
+
+  void OnDocumentStart();
+  void OnDocumentEnd();
+  bool UpdateNeeded() {
+    return mPrivateChanged || mDocCapChanged || mSHistoryChanged;
+  }
+
+ private:
+  virtual ~ContentSessionStore() = default;
+  nsCString CollectDocShellCapabilities();
+
+  nsCOMPtr<nsIDocShell> mDocShell;
+  bool mPrivateChanged;
+  bool mIsPrivate;
+  bool mDocCapChanged;
+  nsCString mDocCaps;
+  // mSHistoryChanged means there are history changes which are found
+  // in the child process. The flag is set when
+  //    1. webProgress changes to STATE_START
+  //    2. webProgress changes to STATE_STOP
+  //    3. receiving "DOMTitleChanged" event
+  bool mSHistoryChanged;
+};
+
+class TabListener : public nsIDOMEventListener,
+                    public nsIObserver,
+                    public nsIPrivacyTransitionObserver,
+                    public nsIWebProgressListener,
+                    public nsSupportsWeakReference {
+ public:
+  explicit TabListener(nsIDocShell* aDocShell, Element* aElement);
+  EventTarget* GetEventTarget();
+  nsresult Init();
+  ContentSessionStore* GetSessionStore() { return mSessionStore; }
+  // the function is called only when TabListener is in parent process
+  void ForceFlushFromParent();
+  void RemoveListeners();
+  void SetEpoch(uint32_t aEpoch) { mEpoch = aEpoch; }
+  uint32_t GetEpoch() { return mEpoch; }
+  void UpdateSHistoryChanges() { AddTimerForUpdate(); }
+  void SetOwnerContent(Element* aElement);
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(TabListener, nsIDOMEventListener)
+
+  NS_DECL_NSIDOMEVENTLISTENER
+  NS_DECL_NSIOBSERVER
+  NS_DECL_NSIPRIVACYTRANSITIONOBSERVER
+  NS_DECL_NSIWEBPROGRESSLISTENER
+
+ private:
+  static void TimerCallback(nsITimer* aTimer, void* aClosure);
+  void AddTimerForUpdate();
+  void StopTimerForUpdate();
+  void AddEventListeners();
+  void RemoveEventListeners();
+  void UpdateSessionStore(bool aIsFlush = false);
+  virtual ~TabListener();
+
+  nsCOMPtr<nsIDocShell> mDocShell;
+  RefPtr<ContentSessionStore> mSessionStore;
+  RefPtr<mozilla::dom::Element> mOwnerContent;
+  bool mProgressListenerRegistered;
+  bool mEventListenerRegistered;
+  bool mPrefObserverRegistered;
+  // Timer used to update data
+  nsCOMPtr<nsITimer> mUpdatedTimer;
+  bool mTimeoutDisabled;
+  int32_t mUpdateInterval;
+  uint32_t mEpoch;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStoreListener_h
diff --git a/toolkit/components/sessionstore/SessionStoreMessageUtils.h b/toolkit/components/sessionstore/SessionStoreMessageUtils.h
new file mode 100644
index 0000000000..8475955f87
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreMessageUtils.h
@@ -0,0 +1,134 @@
+/* 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_SessionStoreMessageUtils_h
+#define mozilla_dom_SessionStoreMessageUtils_h
+
+#include "ipc/IPCMessageUtils.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "SessionStoreData.h"
+#include "SessionStoreUtils.h"
+#include "SessionStoreRestoreData.h"
+
+namespace IPC {
+
+template <>
+struct ParamTraits<mozilla::dom::CollectedNonMultipleSelectValue> {
+  typedef mozilla::dom::CollectedNonMultipleSelectValue paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mSelectedIndex);
+    WriteParam(aWriter, aParam.mValue);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->mSelectedIndex) &&
+           ReadParam(aReader, &aResult->mValue);
+  }
+};
+
+template <>
+struct ParamTraits<CollectedInputDataValue> {
+  typedef CollectedInputDataValue paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.id);
+    WriteParam(aWriter, aParam.type);
+    WriteParam(aWriter, aParam.value);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->id) &&
+           ReadParam(aReader, &aResult->type) &&
+           ReadParam(aReader, &aResult->value);
+  }
+};
+
+template <>
+struct ParamTraits<InputFormData> {
+  typedef InputFormData paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.descendants);
+    WriteParam(aWriter, aParam.innerHTML);
+    WriteParam(aWriter, aParam.url);
+    WriteParam(aWriter, aParam.numId);
+    WriteParam(aWriter, aParam.numXPath);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->descendants) &&
+           ReadParam(aReader, &aResult->innerHTML) &&
+           ReadParam(aReader, &aResult->url) &&
+           ReadParam(aReader, &aResult->numId) &&
+           ReadParam(aReader, &aResult->numXPath);
+  }
+};
+
+}  // namespace IPC
+
+namespace mozilla {
+namespace ipc {
+
+template <>
+struct IPDLParamTraits<mozilla::dom::SessionStoreRestoreData*> {
+  // Note that we intentionally don't de/serialize mChildren here. The receiver
+  // won't be doing anything with the children lists, and it avoids sending form
+  // data for subframes to the content processes of their embedders.
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    mozilla::dom::SessionStoreRestoreData* aParam) {
+    bool isNull = !aParam;
+    WriteIPDLParam(aWriter, aActor, isNull);
+    if (isNull) {
+      return;
+    }
+    WriteIPDLParam(aWriter, aActor, aParam->mURI);
+    WriteIPDLParam(aWriter, aActor, aParam->mInnerHTML);
+    WriteIPDLParam(aWriter, aActor, aParam->mScroll);
+    WriteIPDLParam(aWriter, aActor, aParam->mEntries);
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   RefPtr<mozilla::dom::SessionStoreRestoreData>* aResult) {
+    *aResult = nullptr;
+    bool isNull;
+    if (!ReadIPDLParam(aReader, aActor, &isNull)) {
+      return false;
+    }
+    if (isNull) {
+      return true;
+    }
+    auto data = MakeRefPtr<mozilla::dom::SessionStoreRestoreData>();
+    if (!ReadIPDLParam(aReader, aActor, &data->mURI) ||
+        !ReadIPDLParam(aReader, aActor, &data->mInnerHTML) ||
+        !ReadIPDLParam(aReader, aActor, &data->mScroll) ||
+        !ReadIPDLParam(aReader, aActor, &data->mEntries)) {
+      return false;
+    }
+    *aResult = std::move(data);
+    return true;
+  }
+};
+
+template <>
+struct IPDLParamTraits<mozilla::dom::SessionStoreRestoreData::Entry> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    mozilla::dom::SessionStoreRestoreData::Entry aParam) {
+    WriteIPDLParam(aWriter, aActor, aParam.mData);
+    WriteIPDLParam(aWriter, aActor, aParam.mIsXPath);
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   mozilla::dom::SessionStoreRestoreData::Entry* aResult) {
+    return ReadIPDLParam(aReader, aActor, &aResult->mData) &&
+           ReadIPDLParam(aReader, aActor, &aResult->mIsXPath);
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_dom_SessionStoreMessageUtils_h
diff --git a/toolkit/components/sessionstore/SessionStoreParent.cpp b/toolkit/components/sessionstore/SessionStoreParent.cpp
new file mode 100644
index 0000000000..58be84d4d9
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreParent.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 "mozilla/dom/SessionStoreParent.h"
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/dom/BrowserParent.h"
+#include "mozilla/dom/BrowserSessionStore.h"
+#include "mozilla/dom/BrowserSessionStoreBinding.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/InProcessChild.h"
+#include "mozilla/dom/InProcessParent.h"
+#include "mozilla/dom/SessionStoreChild.h"
+#include "mozilla/dom/SessionStoreUtilsBinding.h"
+#include "SessionStoreFunctions.h"
+#include "nsISupports.h"
+#include "nsIXULRuntime.h"
+#include "nsImportModule.h"
+#include "nsIXPConnect.h"
+
+#ifdef ANDROID
+#  include "mozilla/widget/nsWindow.h"
+#  include "mozilla/jni/GeckoBundleUtils.h"
+#  include "JavaBuiltins.h"
+#endif /* ANDROID */
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+SessionStoreParent::SessionStoreParent(
+    CanonicalBrowsingContext* aBrowsingContext,
+    BrowserSessionStore* aSessionStore)
+    : mBrowsingContext(aBrowsingContext), mSessionStore(aSessionStore) {}
+
+#ifdef ANDROID
+static void DoSessionStoreUpdate(CanonicalBrowsingContext* aBrowsingContext,
+                                 const Maybe<nsCString>& aDocShellCaps,
+                                 const Maybe<bool>& aPrivatedMode,
+                                 SessionStoreFormData* aFormData,
+                                 SessionStoreScrollData* aScroll,
+                                 const MaybeSessionStoreZoom& aZoom,
+                                 bool aNeedCollectSHistory, uint32_t aEpoch) {
+  RefPtr<BrowserSessionStore> sessionStore =
+      BrowserSessionStore::GetOrCreate(aBrowsingContext->Top());
+
+  nsCOMPtr<nsIWidget> widget =
+      aBrowsingContext->GetParentProcessWidgetContaining();
+  if (RefPtr<nsWindow> window = nsWindow::From(widget)) {
+    AutoJSAPI jsapi;
+    if (!jsapi.Init(xpc::PrivilegedJunkScope())) {
+      return;
+    }
+    jni::Object::LocalRef formDataBundle(jni::GetGeckoThreadEnv());
+    jni::Object::LocalRef scrollBundle(jni::GetGeckoThreadEnv());
+
+    if (aFormData) {
+      JS::Rooted<JSObject*> object(jsapi.cx());
+      ErrorResult rv;
+      aFormData->ToJSON(jsapi.cx(), &object);
+
+      JS::Rooted<JS::Value> value(jsapi.cx(), JS::ObjectValue(*object));
+
+      if (NS_FAILED(jni::BoxData(jsapi.cx(), value, formDataBundle, true))) {
+        JS_ClearPendingException(jsapi.cx());
+        return;
+      }
+    }
+
+    if (aScroll) {
+      JS::Rooted<JSObject*> object(jsapi.cx());
+      ErrorResult rv;
+      aScroll->ToJSON(jsapi.cx(), &object);
+      JS::Rooted<JS::Value> value(jsapi.cx(), JS::ObjectValue(*object));
+
+      if (NS_FAILED(jni::BoxData(jsapi.cx(), value, scrollBundle, true))) {
+        JS_ClearPendingException(jsapi.cx());
+        return;
+      }
+    }
+
+    GECKOBUNDLE_START(update);
+    GECKOBUNDLE_PUT(update, "formdata", formDataBundle);
+    GECKOBUNDLE_PUT(update, "scroll", scrollBundle);
+    if (aZoom) {
+      GECKOBUNDLE_START(zoomBundle);
+      GECKOBUNDLE_PUT(zoomBundle, "resolution",
+                      java::sdk::Double::New(std::get<0>(*aZoom)));
+      GECKOBUNDLE_START(displaySizeBundle);
+      GECKOBUNDLE_PUT(displaySizeBundle, "width",
+                      java::sdk::Integer::ValueOf(std::get<1>(*aZoom)));
+      GECKOBUNDLE_PUT(displaySizeBundle, "height",
+                      java::sdk::Integer::ValueOf(std::get<2>(*aZoom)));
+      GECKOBUNDLE_FINISH(displaySizeBundle);
+      GECKOBUNDLE_PUT(zoomBundle, "displaySize", displaySizeBundle);
+      GECKOBUNDLE_FINISH(zoomBundle);
+      GECKOBUNDLE_PUT(update, "zoom", zoomBundle);
+    }
+    GECKOBUNDLE_FINISH(update);
+
+    window->OnUpdateSessionStore(update);
+  }
+}
+#else
+static void DoSessionStoreUpdate(CanonicalBrowsingContext* aBrowsingContext,
+                                 const Maybe<nsCString>& aDocShellCaps,
+                                 const Maybe<bool>& aPrivatedMode,
+                                 SessionStoreFormData* aFormData,
+                                 SessionStoreScrollData* aScroll,
+                                 const MaybeSessionStoreZoom& aZoom,
+                                 bool aNeedCollectSHistory, uint32_t aEpoch) {
+  UpdateSessionStoreData data;
+  if (aDocShellCaps.isSome()) {
+    auto& disallow = data.mDisallow.Construct();
+    if (!aDocShellCaps->IsEmpty()) {
+      disallow = aDocShellCaps.value();
+    } else {
+      disallow.SetIsVoid(true);
+    }
+  }
+
+  if (aPrivatedMode.isSome()) {
+    data.mIsPrivate.Construct() = aPrivatedMode.value();
+  }
+
+  RefPtr<BrowserSessionStore> sessionStore =
+      BrowserSessionStore::GetOrCreate(aBrowsingContext->Top());
+
+  if (!aFormData) {
+    SessionStoreFormData* formData = sessionStore->GetFormdata();
+    data.mFormdata.Construct(formData);
+  } else {
+    data.mFormdata.Construct(aFormData);
+  }
+
+  if (!aScroll) {
+    SessionStoreScrollData* scroll = sessionStore->GetScroll();
+    data.mScroll.Construct(scroll);
+  } else {
+    data.mScroll.Construct(aScroll);
+  }
+
+  nsCOMPtr<nsISessionStoreFunctions> funcs = do_ImportESModule(
+      "resource://gre/modules/SessionStoreFunctions.sys.mjs", fallible);
+  nsCOMPtr<nsIXPConnectWrappedJS> wrapped = do_QueryInterface(funcs);
+  if (!wrapped) {
+    return;
+  }
+
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(wrapped->GetJSObjectGlobal())) {
+    return;
+  }
+
+  JS::Rooted<JS::Value> update(jsapi.cx());
+  if (!ToJSValue(jsapi.cx(), data, &update)) {
+    return;
+  }
+
+  JS::Rooted<JS::Value> key(jsapi.cx(),
+                            aBrowsingContext->Top()->PermanentKey());
+
+  Unused << funcs->UpdateSessionStore(nullptr, aBrowsingContext, key, aEpoch,
+                                      aNeedCollectSHistory, update);
+}
+#endif
+
+void SessionStoreParent::FlushAllSessionStoreChildren(
+    const std::function<void()>& aDone) {
+  if (!mBrowsingContext) {
+    aDone();
+    return;
+  }
+
+  nsTArray<RefPtr<SessionStoreParent::FlushTabStatePromise>> flushPromises;
+
+  // We're special casing this for when the SessionStore{Child, Parent} have
+  // been created in the same process. This is only ever true for the parent
+  // process session store actor, and is needed because
+  // nsFrameLoader::RequestTabStateFlush expect flushes to happen faster than we
+  // can manage by using the common path of sending a message the
+  // SessionStoreChild. Ideally we should be able to do just that, but not
+  // without more work.
+  if (InProcessParent::ChildActorFor(this)) {
+    // Here we assume that the session store data collection only collect for in
+    // (parent-)process content type browsing contexts, which we only flush one
+    // session store actor.
+    flushPromises.AppendElement(FlushSessionStore());
+  } else {
+    // While here we flush all participating actors.
+    BrowserParent* browserParent = static_cast<BrowserParent*>(Manager());
+    browserParent->VisitAll([&flushPromises](BrowserParent* aBrowser) {
+      if (PSessionStoreParent* sessionStoreParent =
+              SingleManagedOrNull(aBrowser->ManagedPSessionStoreParent())) {
+        flushPromises.AppendElement(
+            static_cast<SessionStoreParent*>(sessionStoreParent)
+                ->FlushSessionStore());
+      }
+    });
+  }
+
+  RefPtr<SessionStoreParent::FlushTabStatePromise::AllPromiseType>
+      flushPromise = SessionStoreParent::FlushTabStatePromise::All(
+          GetMainThreadSerialEventTarget(), flushPromises);
+
+  mBrowsingContext->UpdateSessionStoreSessionStorage([aDone, flushPromise]() {
+    flushPromise->Then(GetCurrentSerialEventTarget(), __func__,
+                       [aDone]() { aDone(); });
+  });
+}
+
+already_AddRefed<SessionStoreParent::FlushTabStatePromise>
+SessionStoreParent::FlushSessionStore() {
+  if (!mBrowsingContext) {
+    return nullptr;
+  }
+
+  RefPtr<SessionStoreParent::FlushTabStatePromise> promise =
+      SendFlushTabState();
+  return promise.forget();
+}
+
+void SessionStoreParent::FinalFlushAllSessionStoreChildren(
+    const std::function<void()>& aDone) {
+  if (!mBrowsingContext) {
+    aDone();
+    return;
+  }
+
+  SessionStoreChild* sessionStoreChild =
+      static_cast<SessionStoreChild*>(InProcessParent::ChildActorFor(this));
+  if (!sessionStoreChild || mozilla::SessionHistoryInParent()) {
+    return FlushAllSessionStoreChildren(aDone);
+  }
+
+  sessionStoreChild->FlushSessionStore();
+  mBrowsingContext->UpdateSessionStoreSessionStorage(aDone);
+}
+
+mozilla::ipc::IPCResult SessionStoreParent::RecvSessionStoreUpdate(
+    const Maybe<nsCString>& aDocShellCaps, const Maybe<bool>& aPrivatedMode,
+    const MaybeSessionStoreZoom& aZoom, const bool aNeedCollectSHistory,
+    const uint32_t& aEpoch) {
+  if (!mBrowsingContext) {
+    return IPC_OK();
+  }
+
+  RefPtr<SessionStoreFormData> formData =
+      mHasNewFormData ? mSessionStore->GetFormdata() : nullptr;
+  RefPtr<SessionStoreScrollData> scroll =
+      mHasNewScrollPosition ? mSessionStore->GetScroll() : nullptr;
+
+  DoSessionStoreUpdate(mBrowsingContext, aDocShellCaps, aPrivatedMode, formData,
+                       scroll, aZoom, aNeedCollectSHistory, aEpoch);
+
+  mHasNewFormData = false;
+  mHasNewScrollPosition = false;
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult SessionStoreParent::RecvIncrementalSessionStoreUpdate(
+    const MaybeDiscarded<BrowsingContext>& aBrowsingContext,
+    const Maybe<FormData>& aFormData, const Maybe<nsPoint>& aScrollPosition,
+    uint32_t aEpoch) {
+  if (!aBrowsingContext.IsNull()) {
+    if (aFormData.isSome()) {
+      mHasNewFormData = true;
+    }
+    if (aScrollPosition.isSome()) {
+      mHasNewScrollPosition = true;
+    }
+
+    mSessionStore->UpdateSessionStore(
+        aBrowsingContext.GetMaybeDiscarded()->Canonical(), aFormData,
+        aScrollPosition, aEpoch);
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult SessionStoreParent::RecvResetSessionStore(
+    const MaybeDiscarded<BrowsingContext>& aBrowsingContext, uint32_t aEpoch) {
+  if (!aBrowsingContext.IsNull()) {
+    mSessionStore->RemoveSessionStore(
+        aBrowsingContext.GetMaybeDiscarded()->Canonical());
+  }
+  return IPC_OK();
+}
+
+void SessionStoreParent::SessionStoreUpdate(
+    const Maybe<nsCString>& aDocShellCaps, const Maybe<bool>& aPrivatedMode,
+    const MaybeSessionStoreZoom& aZoom, const bool aNeedCollectSHistory,
+    const uint32_t& aEpoch) {
+  Unused << RecvSessionStoreUpdate(aDocShellCaps, aPrivatedMode, aZoom,
+                                   aNeedCollectSHistory, aEpoch);
+}
+
+void SessionStoreParent::IncrementalSessionStoreUpdate(
+    const MaybeDiscarded<BrowsingContext>& aBrowsingContext,
+    const Maybe<FormData>& aFormData, const Maybe<nsPoint>& aScrollPosition,
+    uint32_t aEpoch) {
+  Unused << RecvIncrementalSessionStoreUpdate(aBrowsingContext, aFormData,
+                                              aScrollPosition, aEpoch);
+}
+
+void SessionStoreParent::ResetSessionStore(
+    const MaybeDiscarded<BrowsingContext>& aBrowsingContext, uint32_t aEpoch) {
+  Unused << RecvResetSessionStore(aBrowsingContext, aEpoch);
+}
+
+NS_IMPL_CYCLE_COLLECTION(SessionStoreParent, mBrowsingContext, mSessionStore)
diff --git a/toolkit/components/sessionstore/SessionStoreParent.h b/toolkit/components/sessionstore/SessionStoreParent.h
new file mode 100644
index 0000000000..0cf723985e
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreParent.h
@@ -0,0 +1,79 @@
+/* -*- 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_SessionStoreParent_h
+#define mozilla_dom_SessionStoreParent_h
+
+#include "mozilla/dom/BrowserSessionStore.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/PSessionStoreParent.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/dom/SessionStoreScrollData.h"
+
+namespace mozilla::dom {
+class BrowserParent;
+
+class SessionStoreParent final : public PSessionStoreParent {
+ public:
+  SessionStoreParent(CanonicalBrowsingContext* aBrowsingContext,
+                     BrowserSessionStore* aSessionStore);
+
+  void FlushAllSessionStoreChildren(const std::function<void()>& aDone);
+
+  void FinalFlushAllSessionStoreChildren(const std::function<void()>& aDone);
+
+  /**
+   * Sends data to be stored and instructions to the session store to
+   * potentially collect data in the parent.
+   */
+  mozilla::ipc::IPCResult RecvSessionStoreUpdate(
+      const Maybe<nsCString>& aDocShellCaps, const Maybe<bool>& aPrivatedMode,
+      const MaybeSessionStoreZoom& aZoom, const bool aNeedCollectSHistory,
+      const uint32_t& aEpoch);
+
+  mozilla::ipc::IPCResult RecvIncrementalSessionStoreUpdate(
+      const MaybeDiscarded<BrowsingContext>& aBrowsingContext,
+      const Maybe<FormData>& aFormData, const Maybe<nsPoint>& aScrollPosition,
+      uint32_t aEpoch);
+
+  mozilla::ipc::IPCResult RecvResetSessionStore(
+      const MaybeDiscarded<BrowsingContext>& aBrowsingContext, uint32_t aEpoch);
+
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(SessionStoreParent)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(SessionStoreParent)
+
+ protected:
+  friend class SessionStoreChild;
+  void SessionStoreUpdate(const Maybe<nsCString>& aDocShellCaps,
+                          const Maybe<bool>& aPrivatedMode,
+                          const MaybeSessionStoreZoom& aZoom,
+                          const bool aNeedCollectSHistory,
+                          const uint32_t& aEpoch);
+
+  void IncrementalSessionStoreUpdate(
+      const MaybeDiscarded<BrowsingContext>& aBrowsingContext,
+      const Maybe<FormData>& aFormData, const Maybe<nsPoint>& aScrollPosition,
+      uint32_t aEpoch);
+
+  void ResetSessionStore(
+      const MaybeDiscarded<BrowsingContext>& aBrowsingContext, uint32_t aEpoch);
+
+ private:
+  ~SessionStoreParent() = default;
+
+  already_AddRefed<SessionStoreParent::FlushTabStatePromise>
+  FlushSessionStore();
+
+  bool mHasNewFormData = false;
+  bool mHasNewScrollPosition = false;
+
+  RefPtr<CanonicalBrowsingContext> mBrowsingContext;
+  RefPtr<BrowserSessionStore> mSessionStore;
+};
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStoreParent_h
diff --git a/toolkit/components/sessionstore/SessionStoreRestoreData.cpp b/toolkit/components/sessionstore/SessionStoreRestoreData.cpp
new file mode 100644
index 0000000000..c7a92cf8ad
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreRestoreData.cpp
@@ -0,0 +1,186 @@
+/* -*- 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 "mozilla/dom/Document.h"
+#include "mozilla/dom/SessionStoreUtils.h"
+#include "mozilla/dom/sessionstore/SessionStoreTypes.h"
+#include "mozilla/dom/WindowContext.h"
+#include "nsISessionStoreRestoreData.h"
+#include "nsNetUtil.h"
+
+namespace mozilla {
+namespace dom {
+
+bool SessionStoreRestoreData::IsEmpty() {
+  return (!mURI && mScroll.IsEmpty() && mInnerHTML.IsEmpty() &&
+          mEntries.IsEmpty() && mChildren.IsEmpty());
+}
+
+SessionStoreRestoreData* SessionStoreRestoreData::FindDataForChild(
+    BrowsingContext* aContext) {
+  nsTArray<uint32_t> path;
+  if (!aContext->GetOffsetPath(path)) {
+    return nullptr;
+  }
+
+  SessionStoreRestoreData* data = this;
+
+  for (uint32_t offset : Reversed(path)) {
+    if (!data || data->mChildren.Length() <= offset ||
+        !data->mChildren[offset] || data->mChildren[offset]->IsEmpty()) {
+      return nullptr;
+    }
+    data = data->mChildren[offset];
+  }
+
+  return data;
+}
+
+bool SessionStoreRestoreData::CanRestoreInto(nsIURI* aDocumentURI) {
+  if (!mURI) {
+    // This should mean that we don't have form data. It's fine to restore this
+    // data into any document — the worst that will happen is that we restore an
+    // incorrect scroll position.
+    MOZ_ASSERT(mEntries.IsEmpty());
+    MOZ_ASSERT(mInnerHTML.IsEmpty());
+    return true;
+  }
+  bool equalsExceptRef = false;
+  return (aDocumentURI &&
+          NS_SUCCEEDED(mURI->EqualsExceptRef(aDocumentURI, &equalsExceptRef)) &&
+          equalsExceptRef);
+}
+
+bool SessionStoreRestoreData::RestoreInto(RefPtr<BrowsingContext> aContext) {
+  if (!aContext->IsInProcess()) {
+    return false;
+  }
+
+  if (WindowContext* window = aContext->GetCurrentWindowContext()) {
+    if (!mScroll.IsEmpty()) {
+      if (nsGlobalWindowInner* inner = window->GetInnerWindow()) {
+        SessionStoreUtils::RestoreScrollPosition(*inner, mScroll);
+      }
+    }
+    if (mURI) {
+      if (nsCOMPtr<Document> doc = window->GetExtantDoc()) {
+        if (!CanRestoreInto(doc->GetDocumentURI())) {
+          return false;
+        }
+        SessionStoreUtils::RestoreFormData(*doc, mInnerHTML, mEntries);
+      }
+    }
+  }
+
+  return true;
+}
+
+void SessionStoreRestoreData::AddFormEntry(
+    bool aIsXPath, const nsAString& aIdOrXPath,
+    sessionstore::FormEntryValue aValue) {
+  mEntries.AppendElement(
+      Entry{sessionstore::FormEntry{nsString(aIdOrXPath), aValue}, aIsXPath});
+}
+
+NS_IMPL_ISUPPORTS(SessionStoreRestoreData, nsISessionStoreRestoreData,
+                  SessionStoreRestoreData)
+
+NS_IMETHODIMP
+SessionStoreRestoreData::GetUrl(nsACString& aURL) {
+  if (mURI) {
+    nsresult rv = mURI->GetSpec(aURL);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::SetUrl(const nsACString& aURL) {
+  nsresult rv = NS_NewURI(getter_AddRefs(mURI), aURL);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::GetInnerHTML(nsAString& aInnerHTML) {
+  aInnerHTML = mInnerHTML;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::SetInnerHTML(const nsAString& aInnerHTML) {
+  mInnerHTML = aInnerHTML;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::GetScroll(nsACString& aScroll) {
+  aScroll = mScroll;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::SetScroll(const nsACString& aScroll) {
+  mScroll = aScroll;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::AddTextField(bool aIsXPath,
+                                      const nsAString& aIdOrXPath,
+                                      const nsAString& aValue) {
+  AddFormEntry(aIsXPath, aIdOrXPath, sessionstore::TextField{nsString(aValue)});
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::AddCheckbox(bool aIsXPath, const nsAString& aIdOrXPath,
+                                     const bool aValue) {
+  AddFormEntry(aIsXPath, aIdOrXPath, sessionstore::Checkbox{aValue});
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::AddFileList(bool aIsXPath, const nsAString& aIdOrXPath,
+                                     const nsAString& aType,
+                                     const nsTArray<nsString>& aFileList) {
+  AddFormEntry(aIsXPath, aIdOrXPath, sessionstore::FileList{aFileList});
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::AddSingleSelect(bool aIsXPath,
+                                         const nsAString& aIdOrXPath,
+                                         uint32_t aSelectedIndex,
+                                         const nsAString& aValue) {
+  AddFormEntry(aIsXPath, aIdOrXPath,
+               sessionstore::SingleSelect{aSelectedIndex, nsString(aValue)});
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::AddMultipleSelect(bool aIsXPath,
+                                           const nsAString& aIdOrXPath,
+                                           const nsTArray<nsString>& aValues) {
+  AddFormEntry(aIsXPath, aIdOrXPath, sessionstore::MultipleSelect{aValues});
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SessionStoreRestoreData::AddChild(nsISessionStoreRestoreData* aChild,
+                                  uint32_t aIndex) {
+  if (nsCOMPtr<SessionStoreRestoreData> child = do_QueryInterface(aChild)) {
+    if (aIndex > mChildren.Length()) {
+      mChildren.SetLength(aIndex);
+    }
+    mChildren.InsertElementAt(aIndex, child);
+  }
+  return NS_OK;
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/toolkit/components/sessionstore/SessionStoreRestoreData.h b/toolkit/components/sessionstore/SessionStoreRestoreData.h
new file mode 100644
index 0000000000..4952045e9d
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreRestoreData.h
@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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_SessionStoreRestoreData_h
+#define mozilla_dom_SessionStoreRestoreData_h
+
+#include "mozilla/dom/sessionstore/SessionStoreTypes.h"
+#include "mozilla/dom/SessionStoreData.h"
+#include "nsISessionStoreRestoreData.h"
+
+namespace mozilla::dom {
+
+#define NS_SESSIONSTORERESTOREDATA_IID               \
+  {                                                  \
+    0x88800c5b, 0xe142, 0x4ac6, {                    \
+      0x91, 0x52, 0xca, 0xbd, 0x3b, 0x74, 0xb9, 0xf8 \
+    }                                                \
+  }
+
+class SessionStoreRestoreData final : public nsISessionStoreRestoreData {
+ public:
+  SessionStoreRestoreData() = default;
+  bool IsEmpty();
+  SessionStoreRestoreData* FindDataForChild(BrowsingContext* aContext);
+  bool CanRestoreInto(nsIURI* aDocumentURI);
+  MOZ_CAN_RUN_SCRIPT bool RestoreInto(RefPtr<BrowsingContext> aContext);
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSISESSIONSTORERESTOREDATA
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_SESSIONSTORERESTOREDATA_IID)
+
+  struct Entry {
+    sessionstore::FormEntry mData;
+    bool mIsXPath;
+  };
+
+ private:
+  virtual ~SessionStoreRestoreData() = default;
+  void AddFormEntry(bool aIsXPath, const nsAString& aIdOrXPath,
+                    sessionstore::FormEntryValue aValue);
+
+  nsCString mScroll;
+  nsCOMPtr<nsIURI> mURI;
+  nsString mInnerHTML;
+  nsTArray<Entry> mEntries;
+  nsTArray<RefPtr<SessionStoreRestoreData>> mChildren;
+
+  friend struct mozilla::ipc::IPDLParamTraits<SessionStoreRestoreData*>;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(SessionStoreRestoreData,
+                              NS_SESSIONSTORERESTOREDATA_IID)
+
+}  // namespace mozilla::dom
+
+#endif
diff --git a/toolkit/components/sessionstore/SessionStoreScrollData.cpp b/toolkit/components/sessionstore/SessionStoreScrollData.cpp
new file mode 100644
index 0000000000..29d58befaa
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreScrollData.cpp
@@ -0,0 +1,123 @@
+/* -*- 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/SessionStoreScrollData.h"
+#include <utility>
+
+#include "js/PropertyAndElement.h"
+#include "js/TypeDecls.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/BrowserSessionStoreBinding.h"
+#include "mozilla/dom/BrowsingContext.h"
+
+#include "nsPresContext.h"
+
+#include "mozilla/dom/WebIDLGlobalNameHash.h"
+#include "js/PropertyDescriptor.h"
+
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/GeneratedAtomList.h"
+#include "js/StructuredClone.h"
+#include "mozilla/dom/DOMJSClass.h"
+#include "mozilla/dom/StructuredCloneHolder.h"
+#include "nsContentUtils.h"
+#include "js/Array.h"
+#include "js/JSON.h"
+
+using namespace mozilla::dom;
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(SessionStoreScrollData)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(SessionStoreScrollData)
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_WEAK_PTR(SessionStoreScrollData,
+                                               mChildren)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SessionStoreScrollData)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+nsISupports* SessionStoreScrollData::GetParentObject() const {
+  return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
+  ;
+}
+
+JSObject* SessionStoreScrollData::WrapObject(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return SessionStoreScrollData_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void SessionStoreScrollData::GetScroll(nsACString& aScroll) const {
+  int scrollX = nsPresContext::AppUnitsToIntCSSPixels(mScroll.x);
+  int scrollY = nsPresContext::AppUnitsToIntCSSPixels(mScroll.y);
+
+  if ((scrollX != 0) || (scrollY != 0)) {
+    aScroll = nsPrintfCString("%d,%d", scrollX, scrollY);
+  } else {
+    aScroll.SetIsVoid(true);
+  }
+}
+
+SessionStoreScrollData::ChildrenArray& SessionStoreScrollData::Children() {
+  return mChildren;
+}
+
+void SessionStoreScrollData::GetChildren(
+    Nullable<ChildrenArray>& aChildren) const {
+  if (!mChildren.IsEmpty()) {
+    aChildren.SetValue() = mChildren.Clone();
+  } else {
+    aChildren.SetNull();
+  }
+}
+
+void SessionStoreScrollData::ToJSON(JSContext* aCx,
+                                    JS::MutableHandle<JSObject*> aRetval) {
+  JS::Rooted<JSObject*> self(aCx);
+  {
+    JS::Rooted<JS::Value> value(aCx);
+    if (!GetOrCreateDOMReflector(aCx, this, &value)) {
+      return;
+    }
+
+    self.set(value.toObjectOrNull());
+  }
+
+  JS::Rooted<JSObject*> result(aCx, JS_NewPlainObject(aCx));
+
+  if (!IsEmpty()) {
+    if (HasData(mScroll)) {
+      if (!SessionStoreUtils::CopyProperty(aCx, result, self, u"scroll"_ns)) {
+        return;
+      }
+    }
+
+    SessionStoreUtils::CopyChildren(aCx, result, mChildren);
+  }
+
+  aRetval.set(result);
+}
+
+void SessionStoreScrollData::Update(const CollectedType& aUpdate) {
+  SessionStoreScrollData_Binding::ClearCachedScrollValue(this);
+  mScroll = aUpdate;
+}
+
+void SessionStoreScrollData::ClearCachedChildren() {
+  SessionStoreScrollData_Binding::ClearCachedChildrenValue(this);
+}
+
+/* static */
+bool SessionStoreScrollData::HasData(const CollectedType& aPoint) {
+  int scrollX = nsPresContext::AppUnitsToIntCSSPixels(aPoint.x);
+  int scrollY = nsPresContext::AppUnitsToIntCSSPixels(aPoint.y);
+  return scrollX != 0 || scrollY != 0;
+}
+
+bool SessionStoreScrollData::IsEmpty() const {
+  return !HasData(mScroll) && mChildren.IsEmpty();
+}
diff --git a/toolkit/components/sessionstore/SessionStoreScrollData.h b/toolkit/components/sessionstore/SessionStoreScrollData.h
new file mode 100644
index 0000000000..b2f5d4bd32
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreScrollData.h
@@ -0,0 +1,69 @@
+/* -*- 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_SessionStoreScrollData_h
+#define mozilla_dom_SessionStoreScrollData_h
+
+#include "js/TypeDecls.h"
+#include "mozilla/WeakPtr.h"
+#include "nsPoint.h"
+#include "nsTArray.h"
+#include "nsWrapperCache.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/dom/SessionStoreChangeListener.h"
+
+namespace mozilla::dom {
+
+class BrowsingContext;
+class WindowGlobalParent;
+class OwningByteStringOrObjectOrNull;
+struct SessionStoreZoomData;
+
+using SessionStoreZoom = std::tuple<float, uint32_t, uint32_t>;
+using MaybeSessionStoreZoom =
+    mozilla::Maybe<std::tuple<float, uint32_t, uint32_t>>;
+
+class SessionStoreScrollData final : public nsISupports,
+                                     public nsWrapperCache,
+                                     public SupportsWeakPtr {
+ public:
+  using CollectedType = nsPoint;
+  using LocationType = WeakPtr<SessionStoreScrollData>;
+  using ChildrenArray = nsTArray<RefPtr<SessionStoreScrollData>>;
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(SessionStoreScrollData)
+  nsISupports* GetParentObject() const;
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  void GetScroll(nsACString& aScroll) const;
+
+  ChildrenArray& Children();
+
+  void GetChildren(Nullable<ChildrenArray>& aChildren) const;
+
+  void ToJSON(JSContext* aCx, JS::MutableHandle<JSObject*> aRetval);
+
+  void Update(const CollectedType& aUpdate);
+
+  void ClearCachedChildren();
+
+  static bool HasData(const CollectedType& aPoint);
+
+  bool IsEmpty() const;
+
+ private:
+  ~SessionStoreScrollData() = default;
+
+  nsPoint mScroll;
+  MaybeSessionStoreZoom mZoom;
+  nsTArray<RefPtr<SessionStoreScrollData>> mChildren;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_SessionStoreScrollData_h
diff --git a/toolkit/components/sessionstore/SessionStoreTypes.ipdlh b/toolkit/components/sessionstore/SessionStoreTypes.ipdlh
new file mode 100644
index 0000000000..c375fa0b36
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreTypes.ipdlh
@@ -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/. */
+
+using struct CollectedInputDataValue from "mozilla/dom/SessionStoreMessageUtils.h";
+using struct nsPoint from "nsPoint.h";
+
+include DOMTypes;
+
+namespace mozilla {
+namespace dom {
+
+namespace sessionstore {
+struct Checkbox {
+  bool value;
+};
+
+struct TextField {
+  nsString value;
+};
+
+struct FileList {
+  nsString[] valueList;
+};
+
+struct SingleSelect {
+  uint32_t index;
+  nsString value;
+};
+
+struct MultipleSelect {
+  nsString[] valueList;
+};
+
+union FormEntryValue {
+  Checkbox;
+  TextField;
+  FileList;
+  SingleSelect;
+  MultipleSelect;
+};
+
+struct FormEntry {
+  nsString id;
+  FormEntryValue value;
+};
+
+struct FormData {
+  bool hasData;
+  FormEntry[] id;
+  FormEntry[] xpath;
+  nsString innerHTML;
+  nsCString uri;
+};
+
+struct DocShellRestoreState {
+  nullable nsIURI URI;
+  nsCString docShellCaps;
+};
+
+}  // sessionstore
+
+}  // dom
+}  // mozilla
diff --git a/toolkit/components/sessionstore/SessionStoreUtils.cpp b/toolkit/components/sessionstore/SessionStoreUtils.cpp
new file mode 100644
index 0000000000..a1e78e19aa
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreUtils.cpp
@@ -0,0 +1,1738 @@
+/* -*- 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 "js/Array.h"  // JS::GetArrayLength, JS::IsArrayObject
+#include "js/JSON.h"
+#include "js/PropertyAndElement.h"  // JS_GetElement
+#include "js/TypeDecls.h"
+#include "jsapi.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/AutocompleteInfoBinding.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "mozilla/dom/HTMLInputElement.h"
+#include "mozilla/dom/HTMLSelectElement.h"
+#include "mozilla/dom/HTMLTextAreaElement.h"
+#include "mozilla/dom/RootedDictionary.h"
+#include "mozilla/dom/SessionStorageManager.h"
+#include "mozilla/dom/PBackgroundSessionStorageCache.h"
+#include "mozilla/dom/SessionStoreChangeListener.h"
+#include "mozilla/dom/SessionStoreChild.h"
+#include "mozilla/dom/SessionStoreUtils.h"
+#include "mozilla/dom/txIXPathContext.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "mozilla/dom/XPathResult.h"
+#include "mozilla/dom/XPathEvaluator.h"
+#include "mozilla/dom/XPathExpression.h"
+#include "mozilla/dom/PBackgroundSessionStorageCache.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ReverseIterator.h"
+#include "mozilla/UniquePtr.h"
+#include "nsCharSeparatedTokenizer.h"
+#include "nsContentList.h"
+#include "nsContentUtils.h"
+#include "nsFocusManager.h"
+#include "nsGlobalWindowOuter.h"
+#include "nsIContentInlines.h"
+#include "nsIDocShell.h"
+#include "nsIFormControl.h"
+#include "nsIScrollableFrame.h"
+#include "nsISHistory.h"
+#include "nsIXULRuntime.h"
+#include "nsPresContext.h"
+#include "nsPrintfCString.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::dom::sessionstore;
+
+namespace {
+
+class DynamicFrameEventFilter final : public nsIDOMEventListener {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS(DynamicFrameEventFilter)
+
+  explicit DynamicFrameEventFilter(EventListener* aListener)
+      : mListener(aListener) {}
+
+  NS_IMETHODIMP HandleEvent(Event* aEvent) override {
+    if (mListener && TargetInNonDynamicDocShell(aEvent)) {
+      mListener->HandleEvent(*aEvent);
+    }
+
+    return NS_OK;
+  }
+
+ private:
+  ~DynamicFrameEventFilter() = default;
+
+  bool TargetInNonDynamicDocShell(Event* aEvent) {
+    EventTarget* target = aEvent->GetTarget();
+    if (!target) {
+      return false;
+    }
+
+    nsPIDOMWindowOuter* outer = target->GetOwnerGlobalForBindingsInternal();
+    if (!outer || !outer->GetDocShell()) {
+      return false;
+    }
+
+    RefPtr<BrowsingContext> context = outer->GetBrowsingContext();
+    return context && !context->CreatedDynamically();
+  }
+
+  RefPtr<EventListener> mListener;
+};
+
+NS_IMPL_CYCLE_COLLECTION(DynamicFrameEventFilter, mListener)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DynamicFrameEventFilter)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMEventListener)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(DynamicFrameEventFilter)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(DynamicFrameEventFilter)
+
+}  // anonymous namespace
+
+/* static */
+void SessionStoreUtils::ForEachNonDynamicChildFrame(
+    const GlobalObject& aGlobal, WindowProxyHolder& aWindow,
+    SessionStoreUtilsFrameCallback& aCallback, ErrorResult& aRv) {
+  if (!aWindow.get()) {
+    aRv.Throw(NS_ERROR_INVALID_ARG);
+    return;
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = aWindow.get()->GetDocShell();
+  if (!docShell) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  int32_t length;
+  aRv = docShell->GetInProcessChildCount(&length);
+  if (aRv.Failed()) {
+    return;
+  }
+
+  for (int32_t i = 0; i < length; ++i) {
+    nsCOMPtr<nsIDocShellTreeItem> item;
+    docShell->GetInProcessChildAt(i, getter_AddRefs(item));
+    if (!item) {
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+    }
+
+    RefPtr<BrowsingContext> context = item->GetBrowsingContext();
+    if (!context) {
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+    }
+
+    if (!context->CreatedDynamically()) {
+      int32_t childOffset = context->ChildOffset();
+      aCallback.Call(WindowProxyHolder(context.forget()), childOffset);
+    }
+  }
+}
+
+/* static */
+already_AddRefed<nsISupports>
+SessionStoreUtils::AddDynamicFrameFilteredListener(
+    const GlobalObject& aGlobal, EventTarget& aTarget, const nsAString& aType,
+    JS::Handle<JS::Value> aListener, bool aUseCapture, bool aMozSystemGroup,
+    ErrorResult& aRv) {
+  if (NS_WARN_IF(!aListener.isObject())) {
+    aRv.Throw(NS_ERROR_INVALID_ARG);
+    return nullptr;
+  }
+
+  JSContext* cx = aGlobal.Context();
+  JS::Rooted<JSObject*> obj(cx, &aListener.toObject());
+  JS::Rooted<JSObject*> global(cx, JS::CurrentGlobalOrNull(cx));
+  RefPtr<EventListener> listener =
+      new EventListener(cx, obj, global, GetIncumbentGlobal());
+
+  nsCOMPtr<nsIDOMEventListener> filter(new DynamicFrameEventFilter(listener));
+  if (aMozSystemGroup) {
+    aRv = aTarget.AddSystemEventListener(aType, filter, aUseCapture);
+  } else {
+    aRv = aTarget.AddEventListener(aType, filter, aUseCapture);
+  }
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  return filter.forget();
+}
+
+/* static */
+void SessionStoreUtils::RemoveDynamicFrameFilteredListener(
+    const GlobalObject& global, EventTarget& aTarget, const nsAString& aType,
+    nsISupports* aListener, bool aUseCapture, bool aMozSystemGroup,
+    ErrorResult& aRv) {
+  nsCOMPtr<nsIDOMEventListener> listener = do_QueryInterface(aListener);
+  if (!listener) {
+    aRv.Throw(NS_ERROR_NO_INTERFACE);
+    return;
+  }
+
+  if (aMozSystemGroup) {
+    aTarget.RemoveSystemEventListener(aType, listener, aUseCapture);
+  } else {
+    aTarget.RemoveEventListener(aType, listener, aUseCapture);
+  }
+}
+
+/* static */
+void SessionStoreUtils::CollectDocShellCapabilities(const GlobalObject& aGlobal,
+                                                    nsIDocShell* aDocShell,
+                                                    nsCString& aRetVal) {
+  bool allow;
+
+#define TRY_ALLOWPROP(y)          \
+  PR_BEGIN_MACRO                  \
+  aDocShell->GetAllow##y(&allow); \
+  if (!allow) {                   \
+    if (!aRetVal.IsEmpty()) {     \
+      aRetVal.Append(',');        \
+    }                             \
+    aRetVal.Append(#y);           \
+  }                               \
+  PR_END_MACRO
+
+  TRY_ALLOWPROP(Plugins);
+  // Bug 1328013 : Don't collect "AllowJavascript" property
+  // TRY_ALLOWPROP(Javascript);
+  TRY_ALLOWPROP(MetaRedirects);
+  TRY_ALLOWPROP(Subframes);
+  TRY_ALLOWPROP(Images);
+  TRY_ALLOWPROP(Media);
+  TRY_ALLOWPROP(DNSPrefetch);
+  TRY_ALLOWPROP(WindowControl);
+  TRY_ALLOWPROP(Auth);
+  TRY_ALLOWPROP(ContentRetargeting);
+  TRY_ALLOWPROP(ContentRetargetingOnChildren);
+#undef TRY_ALLOWPROP
+}
+
+/* static */
+void SessionStoreUtils::RestoreDocShellCapabilities(
+    nsIDocShell* aDocShell, const nsCString& aDisallowCapabilities) {
+  aDocShell->SetAllowPlugins(true);
+  aDocShell->SetAllowMetaRedirects(true);
+  aDocShell->SetAllowSubframes(true);
+  aDocShell->SetAllowImages(true);
+  aDocShell->SetAllowMedia(true);
+  aDocShell->SetAllowDNSPrefetch(true);
+  aDocShell->SetAllowWindowControl(true);
+  aDocShell->SetAllowContentRetargeting(true);
+  aDocShell->SetAllowContentRetargetingOnChildren(true);
+
+  bool allowJavascript = true;
+  for (const nsACString& token :
+       nsCCharSeparatedTokenizer(aDisallowCapabilities, ',').ToRange()) {
+    if (token.EqualsLiteral("Plugins")) {
+      aDocShell->SetAllowPlugins(false);
+    } else if (token.EqualsLiteral("Javascript")) {
+      allowJavascript = false;
+    } else if (token.EqualsLiteral("MetaRedirects")) {
+      aDocShell->SetAllowMetaRedirects(false);
+    } else if (token.EqualsLiteral("Subframes")) {
+      aDocShell->SetAllowSubframes(false);
+    } else if (token.EqualsLiteral("Images")) {
+      aDocShell->SetAllowImages(false);
+    } else if (token.EqualsLiteral("Media")) {
+      aDocShell->SetAllowMedia(false);
+    } else if (token.EqualsLiteral("DNSPrefetch")) {
+      aDocShell->SetAllowDNSPrefetch(false);
+    } else if (token.EqualsLiteral("WindowControl")) {
+      aDocShell->SetAllowWindowControl(false);
+    } else if (token.EqualsLiteral("ContentRetargeting")) {
+      bool allow;
+      aDocShell->GetAllowContentRetargetingOnChildren(&allow);
+      aDocShell->SetAllowContentRetargeting(
+          false);  // will also set AllowContentRetargetingOnChildren
+      aDocShell->SetAllowContentRetargetingOnChildren(
+          allow);  // restore the allowProp to original
+    } else if (token.EqualsLiteral("ContentRetargetingOnChildren")) {
+      aDocShell->SetAllowContentRetargetingOnChildren(false);
+    }
+  }
+
+  if (!mozilla::SessionHistoryInParent()) {
+    // With SessionHistoryInParent, this is set from the parent process.
+    BrowsingContext* bc = aDocShell->GetBrowsingContext();
+    Unused << bc->SetAllowJavascript(allowJavascript);
+  }
+}
+
+static void CollectCurrentScrollPosition(JSContext* aCx, Document& aDocument,
+                                         Nullable<CollectedData>& aRetVal) {
+  PresShell* presShell = aDocument.GetPresShell();
+  if (!presShell) {
+    return;
+  }
+  nsPoint scrollPos = presShell->GetVisualViewportOffset();
+  int scrollX = nsPresContext::AppUnitsToIntCSSPixels(scrollPos.x);
+  int scrollY = nsPresContext::AppUnitsToIntCSSPixels(scrollPos.y);
+
+  if ((scrollX != 0) || (scrollY != 0)) {
+    aRetVal.SetValue().mScroll.Construct() =
+        nsPrintfCString("%d,%d", scrollX, scrollY);
+  }
+}
+
+/* static */
+void SessionStoreUtils::RestoreScrollPosition(const GlobalObject& aGlobal,
+                                              nsGlobalWindowInner& aWindow,
+                                              const CollectedData& aData) {
+  if (aData.mScroll.WasPassed()) {
+    RestoreScrollPosition(aWindow, aData.mScroll.Value());
+  }
+}
+
+/* static */
+void SessionStoreUtils::RestoreScrollPosition(
+    nsGlobalWindowInner& aWindow, const nsCString& aScrollPosition) {
+  using Change = mozilla::dom::SessionStoreChangeListener::Change;
+  SessionStoreChangeListener::CollectSessionStoreData(
+      aWindow.GetWindowContext(), EnumSet<Change>(Change::Scroll));
+
+  nsCCharSeparatedTokenizer tokenizer(aScrollPosition, ',');
+  nsAutoCString token(tokenizer.nextToken());
+  int pos_X = atoi(token.get());
+  token = tokenizer.nextToken();
+  int pos_Y = atoi(token.get());
+
+  aWindow.ScrollTo(pos_X, pos_Y);
+
+  if (nsCOMPtr<Document> doc = aWindow.GetExtantDoc()) {
+    if (nsPresContext* presContext = doc->GetPresContext()) {
+      if (presContext->IsRootContentDocumentCrossProcess()) {
+        // Use eMainThread so this takes precedence over session history
+        // (ScrollFrameHelper::ScrollToRestoredPosition()).
+        presContext->PresShell()->ScrollToVisual(
+            CSSPoint::ToAppUnits(CSSPoint(pos_X, pos_Y)),
+            layers::FrameMetrics::eMainThread, ScrollMode::Instant);
+      }
+    }
+  }
+}
+
+// Implements the Luhn checksum algorithm as described at
+// http://wikipedia.org/wiki/Luhn_algorithm
+// Number digit lengths vary with network, but should fall within 12-19 range.
+// [2] More details at https://en.wikipedia.org/wiki/Payment_card_number
+static bool IsValidCCNumber(nsAString& aValue) {
+  uint32_t total = 0;
+  uint32_t numLength = 0;
+  uint32_t strLen = aValue.Length();
+  for (uint32_t i = 0; i < strLen; ++i) {
+    uint32_t idx = strLen - i - 1;
+    // ignore whitespace and dashes)
+    char16_t chr = aValue[idx];
+    if (IsSpaceCharacter(chr) || chr == '-') {
+      continue;
+    }
+    // If our number is too long, note that fact
+    ++numLength;
+    if (numLength > 19) {
+      return false;
+    }
+    // Try to parse the character as a base-10 integer.
+    nsresult rv = NS_OK;
+    uint32_t val = Substring(aValue, idx, 1).ToInteger(&rv, 10);
+    if (NS_FAILED(rv)) {
+      return false;
+    }
+    if (i % 2 == 1) {
+      val *= 2;
+      if (val > 9) {
+        val -= 9;
+      }
+    }
+    total += val;
+  }
+
+  return numLength >= 12 && total % 10 == 0;
+}
+
+// Limit the number of XPath expressions for performance reasons. See bug
+// 477564.
+static const uint16_t kMaxTraversedXPaths = 100;
+
+// A helper function to append a element into mId or mXpath of CollectedData
+static Record<nsString, OwningStringOrBooleanOrObject>::EntryType*
+AppendEntryToCollectedData(nsINode* aNode, const nsAString& aId,
+                           uint16_t& aGeneratedCount,
+                           Nullable<CollectedData>& aRetVal) {
+  Record<nsString, OwningStringOrBooleanOrObject>::EntryType* entry;
+  if (!aId.IsEmpty()) {
+    if (!aRetVal.SetValue().mId.WasPassed()) {
+      aRetVal.SetValue().mId.Construct();
+    }
+    auto& recordEntries = aRetVal.SetValue().mId.Value().Entries();
+    entry = recordEntries.AppendElement();
+    entry->mKey = aId;
+  } else {
+    if (!aRetVal.SetValue().mXpath.WasPassed()) {
+      aRetVal.SetValue().mXpath.Construct();
+    }
+    auto& recordEntries = aRetVal.SetValue().mXpath.Value().Entries();
+    entry = recordEntries.AppendElement();
+    nsAutoString xpath;
+    aNode->GenerateXPath(xpath);
+    aGeneratedCount++;
+    entry->mKey = xpath;
+  }
+  return entry;
+}
+
+/* for bool value */
+static void AppendValueToCollectedData(nsINode* aNode, const nsAString& aId,
+                                       const bool& aValue,
+                                       uint16_t& aGeneratedCount,
+                                       JSContext* aCx,
+                                       Nullable<CollectedData>& aRetVal) {
+  Record<nsString, OwningStringOrBooleanOrObject>::EntryType* entry =
+      AppendEntryToCollectedData(aNode, aId, aGeneratedCount, aRetVal);
+  entry->mValue.SetAsBoolean() = aValue;
+}
+
+/* for nsString value */
+static void AppendValueToCollectedData(nsINode* aNode, const nsAString& aId,
+                                       const nsString& aValue,
+                                       uint16_t& aGeneratedCount,
+                                       Nullable<CollectedData>& aRetVal) {
+  Record<nsString, OwningStringOrBooleanOrObject>::EntryType* entry =
+      AppendEntryToCollectedData(aNode, aId, aGeneratedCount, aRetVal);
+  entry->mValue.SetAsString() = aValue;
+}
+
+/* for single select value */
+static void AppendValueToCollectedData(
+    nsINode* aNode, const nsAString& aId,
+    const CollectedNonMultipleSelectValue& aValue, uint16_t& aGeneratedCount,
+    JSContext* aCx, Nullable<CollectedData>& aRetVal) {
+  JS::Rooted<JS::Value> jsval(aCx);
+  if (!ToJSValue(aCx, aValue, &jsval)) {
+    JS_ClearPendingException(aCx);
+    return;
+  }
+  Record<nsString, OwningStringOrBooleanOrObject>::EntryType* entry =
+      AppendEntryToCollectedData(aNode, aId, aGeneratedCount, aRetVal);
+  entry->mValue.SetAsObject() = &jsval.toObject();
+}
+
+/* special handing for input element with string type */
+static void AppendValueToCollectedData(Document& aDocument, nsINode* aNode,
+                                       const nsAString& aId,
+                                       const nsString& aValue,
+                                       uint16_t& aGeneratedCount,
+                                       JSContext* aCx,
+                                       Nullable<CollectedData>& aRetVal) {
+  if (!aId.IsEmpty()) {
+    // We want to avoid saving data for about:sessionrestore as a string.
+    // Since it's stored in the form as stringified JSON, stringifying
+    // further causes an explosion of escape characters. cf. bug 467409
+    if (aId.EqualsLiteral("sessionData")) {
+      nsAutoCString url;
+      Unused << aDocument.GetDocumentURI()->GetSpecIgnoringRef(url);
+      if (url.EqualsLiteral("about:sessionrestore") ||
+          url.EqualsLiteral("about:welcomeback")) {
+        JS::Rooted<JS::Value> jsval(aCx);
+        if (JS_ParseJSON(aCx, aValue.get(), aValue.Length(), &jsval) &&
+            jsval.isObject()) {
+          Record<nsString, OwningStringOrBooleanOrObject>::EntryType* entry =
+              AppendEntryToCollectedData(aNode, aId, aGeneratedCount, aRetVal);
+          entry->mValue.SetAsObject() = &jsval.toObject();
+        } else {
+          JS_ClearPendingException(aCx);
+        }
+        return;
+      }
+    }
+  }
+  AppendValueToCollectedData(aNode, aId, aValue, aGeneratedCount, aRetVal);
+}
+
+/* for nsTArray<nsString>: file and multipleSelect */
+static void AppendValueToCollectedData(nsINode* aNode, const nsAString& aId,
+                                       const nsAString& aValueType,
+                                       nsTArray<nsString>& aValue,
+                                       uint16_t& aGeneratedCount,
+                                       JSContext* aCx,
+                                       Nullable<CollectedData>& aRetVal) {
+  JS::Rooted<JS::Value> jsval(aCx);
+  if (aValueType.EqualsLiteral("file")) {
+    CollectedFileListValue val;
+    val.mType = aValueType;
+    val.mFileList = std::move(aValue);
+    if (!ToJSValue(aCx, val, &jsval)) {
+      JS_ClearPendingException(aCx);
+      return;
+    }
+  } else {
+    if (!ToJSValue(aCx, aValue, &jsval)) {
+      JS_ClearPendingException(aCx);
+      return;
+    }
+  }
+  Record<nsString, OwningStringOrBooleanOrObject>::EntryType* entry =
+      AppendEntryToCollectedData(aNode, aId, aGeneratedCount, aRetVal);
+  entry->mValue.SetAsObject() = &jsval.toObject();
+}
+
+// This isn't size as in binary size, just a heuristic to not store too large
+// fields in session store. See StaticPrefs::browser_sessionstore_dom_form_limit
+static uint32_t SizeOfFormEntry(const FormEntryValue& aValue) {
+  uint32_t size = 0;
+  switch (aValue.type()) {
+    case FormEntryValue::TCheckbox:
+      size = aValue.get_Checkbox().value() ? 4 : 5;
+      break;
+    case FormEntryValue::TTextField:
+      size = aValue.get_TextField().value().Length();
+      break;
+    case FormEntryValue::TFileList: {
+      for (const auto& value : aValue.get_FileList().valueList()) {
+        size += value.Length();
+      }
+      break;
+    }
+    case FormEntryValue::TSingleSelect:
+      size = aValue.get_SingleSelect().value().Length();
+      break;
+    case FormEntryValue::TMultipleSelect: {
+      for (const auto& value : aValue.get_MultipleSelect().valueList()) {
+        size += value.Length();
+      }
+      break;
+    }
+    default:
+      break;
+  }
+  return size;
+}
+
+static uint32_t AppendEntry(nsINode* aNode, const nsString& aId,
+                            const FormEntryValue& aValue,
+                            sessionstore::FormData& aFormData) {
+  uint32_t size = SizeOfFormEntry(aValue);
+  if (size > StaticPrefs::browser_sessionstore_dom_form_limit()) {
+    return 0;
+  }
+
+  if (aId.IsEmpty()) {
+    FormEntry* entry = aFormData.xpath().AppendElement();
+    entry->value() = aValue;
+    aNode->GenerateXPath(entry->id());
+    size += entry->id().Length();
+  } else {
+    aFormData.id().AppendElement(FormEntry{aId, aValue});
+    size += aId.Length();
+  }
+
+  return size;
+}
+
+static uint32_t CollectTextAreaElement(Document* aDocument,
+                                       sessionstore::FormData& aFormData) {
+  uint32_t size = 0;
+  RefPtr<nsContentList> textlist =
+      NS_GetContentList(aDocument, kNameSpaceID_XHTML, u"textarea"_ns);
+  uint32_t length = textlist->Length();
+  for (uint32_t i = 0; i < length; ++i) {
+    MOZ_ASSERT(textlist->Item(i), "null item in node list!");
+
+    HTMLTextAreaElement* textArea =
+        HTMLTextAreaElement::FromNodeOrNull(textlist->Item(i));
+    if (!textArea) {
+      continue;
+    }
+    DOMString autocomplete;
+    textArea->GetAutocomplete(autocomplete);
+    if (autocomplete.AsAString().EqualsLiteral("off")) {
+      continue;
+    }
+    nsAutoString id;
+    textArea->GetId(id);
+    if (id.IsEmpty() && (aFormData.xpath().Length() > kMaxTraversedXPaths)) {
+      continue;
+    }
+    nsString value;
+    textArea->GetValue(value);
+    // In order to reduce XPath generation (which is slow), we only save data
+    // for form fields that have been changed. (cf. bug 537289)
+    if (textArea->AttrValueIs(kNameSpaceID_None, nsGkAtoms::value, value,
+                              eCaseMatters)) {
+      continue;
+    }
+
+    size += AppendEntry(textArea, id, TextField{value}, aFormData);
+  }
+
+  return size;
+}
+
+static uint32_t CollectInputElement(Document* aDocument,
+                                    sessionstore::FormData& aFormData) {
+  uint32_t size = 0;
+  RefPtr<nsContentList> inputlist =
+      NS_GetContentList(aDocument, kNameSpaceID_XHTML, u"input"_ns);
+  uint32_t length = inputlist->Length();
+  for (uint32_t i = 0; i < length; ++i) {
+    MOZ_ASSERT(inputlist->Item(i), "null item in node list!");
+    nsCOMPtr<nsIFormControl> formControl =
+        do_QueryInterface(inputlist->Item(i));
+    if (formControl) {
+      auto controlType = formControl->ControlType();
+      if (controlType == FormControlType::InputPassword ||
+          controlType == FormControlType::InputHidden ||
+          controlType == FormControlType::InputButton ||
+          controlType == FormControlType::InputImage ||
+          controlType == FormControlType::InputSubmit ||
+          controlType == FormControlType::InputReset) {
+        continue;
+      }
+    }
+    RefPtr<HTMLInputElement> input =
+        HTMLInputElement::FromNodeOrNull(inputlist->Item(i));
+    if (!input || !nsContentUtils::IsAutocompleteEnabled(input)) {
+      continue;
+    }
+    nsAutoString id;
+    input->GetId(id);
+    if (id.IsEmpty() && (aFormData.xpath().Length() > kMaxTraversedXPaths)) {
+      continue;
+    }
+    Nullable<AutocompleteInfo> aInfo;
+    input->GetAutocompleteInfo(aInfo);
+    if (!aInfo.IsNull() && !aInfo.Value().mCanAutomaticallyPersist) {
+      continue;
+    }
+
+    FormEntryValue value;
+    if (input->ControlType() == FormControlType::InputCheckbox ||
+        input->ControlType() == FormControlType::InputRadio) {
+      bool checked = input->Checked();
+      if (checked == input->DefaultChecked()) {
+        continue;
+      }
+      size += AppendEntry(input, id, Checkbox{checked}, aFormData);
+    } else if (input->ControlType() == FormControlType::InputFile) {
+      IgnoredErrorResult rv;
+      sessionstore::FileList file;
+      input->MozGetFileNameArray(file.valueList(), rv);
+      if (rv.Failed() || file.valueList().IsEmpty()) {
+        continue;
+      }
+      size += AppendEntry(input, id, file, aFormData);
+    } else {
+      TextField field;
+      input->GetValue(field.value(), CallerType::System);
+      auto& value = field.value();
+      // In order to reduce XPath generation (which is slow), we only save data
+      // for form fields that have been changed. (cf. bug 537289)
+      // Also, don't want to collect credit card number.
+      if (value.IsEmpty() || IsValidCCNumber(value) ||
+          input->HasBeenTypePassword() ||
+          input->AttrValueIs(kNameSpaceID_None, nsGkAtoms::value, value,
+                             eCaseMatters)) {
+        continue;
+      }
+      size += AppendEntry(input, id, field, aFormData);
+    }
+  }
+
+  return size;
+}
+
+static uint32_t CollectSelectElement(Document* aDocument,
+                                     sessionstore::FormData& aFormData) {
+  uint32_t size = 0;
+  RefPtr<nsContentList> selectlist =
+      NS_GetContentList(aDocument, kNameSpaceID_XHTML, u"select"_ns);
+  uint32_t length = selectlist->Length();
+  for (uint32_t i = 0; i < length; ++i) {
+    MOZ_ASSERT(selectlist->Item(i), "null item in node list!");
+    RefPtr<HTMLSelectElement> select =
+        HTMLSelectElement::FromNodeOrNull(selectlist->Item(i));
+    if (!select) {
+      continue;
+    }
+    nsAutoString id;
+    select->GetId(id);
+    if (id.IsEmpty() && (aFormData.xpath().Length() > kMaxTraversedXPaths)) {
+      continue;
+    }
+    AutocompleteInfo aInfo;
+    select->GetAutocompleteInfo(aInfo);
+    if (!aInfo.mCanAutomaticallyPersist) {
+      continue;
+    }
+
+    if (!select->Multiple()) {
+      HTMLOptionsCollection* options = select->GetOptions();
+      if (!options) {
+        continue;
+      }
+
+      uint32_t numOptions = options->Length();
+      int32_t defaultIndex = 0;
+      for (uint32_t idx = 0; idx < numOptions; idx++) {
+        HTMLOptionElement* option = options->ItemAsOption(idx);
+        if (option->DefaultSelected()) {
+          defaultIndex = option->Index();
+        }
+      }
+
+      int32_t selectedIndex = select->SelectedIndex();
+      if (selectedIndex == defaultIndex || selectedIndex < 0) {
+        continue;
+      }
+
+      DOMString selectVal;
+      select->GetValue(selectVal);
+      size += AppendEntry(select, id,
+                          SingleSelect{static_cast<uint32_t>(selectedIndex),
+                                       selectVal.AsAString()},
+                          aFormData);
+    } else {
+      HTMLOptionsCollection* options = select->GetOptions();
+      if (!options) {
+        continue;
+      }
+      bool hasDefaultValue = true;
+      nsTArray<nsString> selectslist;
+      uint32_t numOptions = options->Length();
+      for (uint32_t idx = 0; idx < numOptions; idx++) {
+        HTMLOptionElement* option = options->ItemAsOption(idx);
+        bool selected = option->Selected();
+
+        hasDefaultValue =
+            hasDefaultValue && (selected == option->DefaultSelected());
+
+        if (!selected) {
+          continue;
+        }
+        option->GetValue(*selectslist.AppendElement());
+      }
+      // In order to reduce XPath generation (which is slow), we only save data
+      // for form fields that have been changed. (cf. bug 537289)
+      if (hasDefaultValue) {
+        continue;
+      }
+
+      size += AppendEntry(select, id, MultipleSelect{selectslist}, aFormData);
+    }
+  }
+
+  return size;
+}
+
+/* static */
+uint32_t SessionStoreUtils::CollectFormData(Document* aDocument,
+                                            sessionstore::FormData& aFormData) {
+  MOZ_DIAGNOSTIC_ASSERT(aDocument);
+  uint32_t size = 0;
+  size += CollectTextAreaElement(aDocument, aFormData);
+  size += CollectInputElement(aDocument, aFormData);
+  size += CollectSelectElement(aDocument, aFormData);
+
+  aFormData.hasData() =
+      !aFormData.id().IsEmpty() || !aFormData.xpath().IsEmpty();
+
+  return size;
+}
+
+/* static */
+template <typename... ArgsT>
+void SessionStoreUtils::CollectFromTextAreaElement(Document& aDocument,
+                                                   uint16_t& aGeneratedCount,
+                                                   ArgsT&&... args) {
+  RefPtr<nsContentList> textlist =
+      NS_GetContentList(&aDocument, kNameSpaceID_XHTML, u"textarea"_ns);
+  uint32_t length = textlist->Length(true);
+  for (uint32_t i = 0; i < length; ++i) {
+    MOZ_ASSERT(textlist->Item(i), "null item in node list!");
+
+    HTMLTextAreaElement* textArea =
+        HTMLTextAreaElement::FromNodeOrNull(textlist->Item(i));
+    if (!textArea) {
+      continue;
+    }
+    DOMString autocomplete;
+    textArea->GetAutocomplete(autocomplete);
+    if (autocomplete.AsAString().EqualsLiteral("off")) {
+      continue;
+    }
+    nsAutoString id;
+    textArea->GetId(id);
+    if (id.IsEmpty() && (aGeneratedCount > kMaxTraversedXPaths)) {
+      continue;
+    }
+    nsString value;
+    textArea->GetValue(value);
+    // In order to reduce XPath generation (which is slow), we only save data
+    // for form fields that have been changed. (cf. bug 537289)
+    if (textArea->AttrValueIs(kNameSpaceID_None, nsGkAtoms::value, value,
+                              eCaseMatters)) {
+      continue;
+    }
+    AppendValueToCollectedData(textArea, id, value, aGeneratedCount,
+                               std::forward<ArgsT>(args)...);
+  }
+}
+
+/* static */
+template <typename... ArgsT>
+void SessionStoreUtils::CollectFromInputElement(Document& aDocument,
+                                                uint16_t& aGeneratedCount,
+                                                ArgsT&&... args) {
+  RefPtr<nsContentList> inputlist =
+      NS_GetContentList(&aDocument, kNameSpaceID_XHTML, u"input"_ns);
+  uint32_t length = inputlist->Length(true);
+  for (uint32_t i = 0; i < length; ++i) {
+    MOZ_ASSERT(inputlist->Item(i), "null item in node list!");
+    nsCOMPtr<nsIFormControl> formControl =
+        do_QueryInterface(inputlist->Item(i));
+    if (formControl) {
+      auto controlType = formControl->ControlType();
+      if (controlType == FormControlType::InputPassword ||
+          controlType == FormControlType::InputHidden ||
+          controlType == FormControlType::InputButton ||
+          controlType == FormControlType::InputImage ||
+          controlType == FormControlType::InputSubmit ||
+          controlType == FormControlType::InputReset) {
+        continue;
+      }
+    }
+    RefPtr<HTMLInputElement> input =
+        HTMLInputElement::FromNodeOrNull(inputlist->Item(i));
+    if (!input || !nsContentUtils::IsAutocompleteEnabled(input)) {
+      continue;
+    }
+    nsAutoString id;
+    input->GetId(id);
+    if (id.IsEmpty() && (aGeneratedCount > kMaxTraversedXPaths)) {
+      continue;
+    }
+    Nullable<AutocompleteInfo> aInfo;
+    input->GetAutocompleteInfo(aInfo);
+    if (!aInfo.IsNull() && !aInfo.Value().mCanAutomaticallyPersist) {
+      continue;
+    }
+
+    if (input->ControlType() == FormControlType::InputCheckbox ||
+        input->ControlType() == FormControlType::InputRadio) {
+      bool checked = input->Checked();
+      if (checked == input->DefaultChecked()) {
+        continue;
+      }
+      AppendValueToCollectedData(input, id, checked, aGeneratedCount,
+                                 std::forward<ArgsT>(args)...);
+    } else if (input->ControlType() == FormControlType::InputFile) {
+      IgnoredErrorResult rv;
+      nsTArray<nsString> result;
+      input->MozGetFileNameArray(result, rv);
+      if (rv.Failed() || result.Length() == 0) {
+        continue;
+      }
+      AppendValueToCollectedData(input, id, u"file"_ns, result, aGeneratedCount,
+                                 std::forward<ArgsT>(args)...);
+    } else {
+      nsString value;
+      input->GetValue(value, CallerType::System);
+      // In order to reduce XPath generation (which is slow), we only save data
+      // for form fields that have been changed. (cf. bug 537289)
+      // Also, don't want to collect credit card number.
+      if (value.IsEmpty() || IsValidCCNumber(value) ||
+          input->HasBeenTypePassword() ||
+          input->AttrValueIs(kNameSpaceID_None, nsGkAtoms::value, value,
+                             eCaseMatters)) {
+        continue;
+      }
+      AppendValueToCollectedData(aDocument, input, id, value, aGeneratedCount,
+                                 std::forward<ArgsT>(args)...);
+    }
+  }
+}
+
+/* static */
+template <typename... ArgsT>
+void SessionStoreUtils::CollectFromSelectElement(Document& aDocument,
+                                                 uint16_t& aGeneratedCount,
+                                                 ArgsT&&... args) {
+  RefPtr<nsContentList> selectlist =
+      NS_GetContentList(&aDocument, kNameSpaceID_XHTML, u"select"_ns);
+  uint32_t length = selectlist->Length(true);
+  for (uint32_t i = 0; i < length; ++i) {
+    MOZ_ASSERT(selectlist->Item(i), "null item in node list!");
+    RefPtr<HTMLSelectElement> select =
+        HTMLSelectElement::FromNodeOrNull(selectlist->Item(i));
+    if (!select) {
+      continue;
+    }
+    nsAutoString id;
+    select->GetId(id);
+    if (id.IsEmpty() && (aGeneratedCount > kMaxTraversedXPaths)) {
+      continue;
+    }
+    AutocompleteInfo aInfo;
+    select->GetAutocompleteInfo(aInfo);
+    if (!aInfo.mCanAutomaticallyPersist) {
+      continue;
+    }
+    nsAutoCString value;
+    if (!select->Multiple()) {
+      // <select>s without the multiple attribute are hard to determine the
+      // default value, so assume we don't have the default.
+      DOMString selectVal;
+      select->GetValue(selectVal);
+      CollectedNonMultipleSelectValue val;
+      val.mSelectedIndex = select->SelectedIndex();
+      val.mValue = selectVal.AsAString();
+      AppendValueToCollectedData(select, id, val, aGeneratedCount,
+                                 std::forward<ArgsT>(args)...);
+    } else {
+      // <select>s with the multiple attribute are easier to determine the
+      // default value since each <option> has a defaultSelected property
+      HTMLOptionsCollection* options = select->GetOptions();
+      if (!options) {
+        continue;
+      }
+      bool hasDefaultValue = true;
+      nsTArray<nsString> selectslist;
+      uint32_t numOptions = options->Length();
+      for (uint32_t idx = 0; idx < numOptions; idx++) {
+        HTMLOptionElement* option = options->ItemAsOption(idx);
+        bool selected = option->Selected();
+        if (!selected) {
+          continue;
+        }
+        option->GetValue(*selectslist.AppendElement());
+        hasDefaultValue =
+            hasDefaultValue && (selected == option->DefaultSelected());
+      }
+      // In order to reduce XPath generation (which is slow), we only save data
+      // for form fields that have been changed. (cf. bug 537289)
+      if (hasDefaultValue) {
+        continue;
+      }
+
+      AppendValueToCollectedData(select, id, u"multipleSelect"_ns, selectslist,
+                                 aGeneratedCount, std::forward<ArgsT>(args)...);
+    }
+  }
+}
+
+static void CollectCurrentFormData(JSContext* aCx, Document& aDocument,
+                                   Nullable<CollectedData>& aRetVal) {
+  uint16_t generatedCount = 0;
+  /* textarea element */
+  SessionStoreUtils::CollectFromTextAreaElement(aDocument, generatedCount,
+                                                aRetVal);
+  /* input element */
+  SessionStoreUtils::CollectFromInputElement(aDocument, generatedCount, aCx,
+                                             aRetVal);
+  /* select element */
+  SessionStoreUtils::CollectFromSelectElement(aDocument, generatedCount, aCx,
+                                              aRetVal);
+
+  Element* bodyElement = aDocument.GetBody();
+  if (bodyElement && bodyElement->IsInDesignMode()) {
+    bodyElement->GetInnerHTML(aRetVal.SetValue().mInnerHTML.Construct(),
+                              IgnoreErrors());
+  }
+
+  if (aRetVal.IsNull()) {
+    return;
+  }
+
+  // Store the frame's current URL with its form data so that we can compare
+  // it when restoring data to not inject form data into the wrong document.
+  nsIURI* uri = aDocument.GetDocumentURI();
+  if (uri) {
+    uri->GetSpecIgnoringRef(aRetVal.SetValue().mUrl.Construct());
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetElementAsString(Element* aElement, const nsAString& aValue) {
+  IgnoredErrorResult rv;
+  if (auto* textArea = HTMLTextAreaElement::FromNode(aElement)) {
+    textArea->SetValue(aValue, rv);
+    if (!rv.Failed()) {
+      nsContentUtils::DispatchInputEvent(aElement);
+    }
+    return;
+  }
+  if (auto* input = HTMLInputElement::FromNode(aElement)) {
+    input->SetValue(aValue, CallerType::NonSystem, rv);
+    if (!rv.Failed()) {
+      nsContentUtils::DispatchInputEvent(aElement);
+    }
+    return;
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetElementAsBool(Element* aElement, bool aValue) {
+  HTMLInputElement* input = HTMLInputElement::FromNode(aElement);
+  if (input) {
+    bool checked = input->Checked();
+    if (aValue != checked) {
+      input->SetChecked(aValue);
+      nsContentUtils::DispatchInputEvent(aElement);
+    }
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetElementAsFiles(HTMLInputElement* aElement,
+                              const CollectedFileListValue& aValue) {
+  IgnoredErrorResult rv;
+  aElement->MozSetFileNameArray(aValue.mFileList, rv);
+  if (rv.Failed()) {
+    return;
+  }
+  nsContentUtils::DispatchInputEvent(aElement);
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetElementAsSelect(HTMLSelectElement* aElement,
+                               const CollectedNonMultipleSelectValue& aValue) {
+  HTMLOptionsCollection* options = aElement->GetOptions();
+  if (!options) {
+    return;
+  }
+  int32_t selectIdx = options->SelectedIndex();
+  if (selectIdx >= 0) {
+    nsAutoString selectOptionVal;
+    options->ItemAsOption(selectIdx)->GetValue(selectOptionVal);
+    if (aValue.mValue.Equals(selectOptionVal)) {
+      return;
+    }
+  }
+  uint32_t numOptions = options->Length();
+  for (uint32_t idx = 0; idx < numOptions; idx++) {
+    HTMLOptionElement* option = options->ItemAsOption(idx);
+    nsAutoString optionValue;
+    option->GetValue(optionValue);
+    if (aValue.mValue.Equals(optionValue)) {
+      aElement->SetSelectedIndex(idx);
+      nsContentUtils::DispatchInputEvent(aElement);
+    }
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetElementAsMultiSelect(HTMLSelectElement* aElement,
+                                    const nsTArray<nsString>& aValueArray) {
+  bool fireEvent = false;
+  HTMLOptionsCollection* options = aElement->GetOptions();
+  if (!options) {
+    return;
+  }
+  uint32_t numOptions = options->Length();
+  for (uint32_t idx = 0; idx < numOptions; idx++) {
+    HTMLOptionElement* option = options->ItemAsOption(idx);
+    nsAutoString optionValue;
+    option->GetValue(optionValue);
+    for (uint32_t i = 0, l = aValueArray.Length(); i < l; ++i) {
+      if (optionValue.Equals(aValueArray[i])) {
+        option->SetSelected(true);
+        if (!option->DefaultSelected()) {
+          fireEvent = true;
+        }
+      }
+    }
+  }
+  if (fireEvent) {
+    nsContentUtils::DispatchInputEvent(aElement);
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetElementAsObject(JSContext* aCx, Element* aElement,
+                               JS::Handle<JS::Value> aObject) {
+  RefPtr<HTMLInputElement> input = HTMLInputElement::FromNode(aElement);
+  if (input) {
+    if (input->ControlType() == FormControlType::InputFile) {
+      CollectedFileListValue value;
+      if (value.Init(aCx, aObject)) {
+        SetElementAsFiles(input, value);
+      } else {
+        JS_ClearPendingException(aCx);
+      }
+    }
+    return;
+  }
+  RefPtr<HTMLSelectElement> select = HTMLSelectElement::FromNode(aElement);
+  if (select) {
+    // For Single Select Element
+    if (!select->Multiple()) {
+      CollectedNonMultipleSelectValue value;
+      if (value.Init(aCx, aObject)) {
+        SetElementAsSelect(select, value);
+      } else {
+        JS_ClearPendingException(aCx);
+      }
+      return;
+    }
+
+    // For Multiple Selects Element
+    bool isArray = false;
+    JS::IsArrayObject(aCx, aObject, &isArray);
+    if (!isArray) {
+      return;
+    }
+    JS::Rooted<JSObject*> arrayObj(aCx, &aObject.toObject());
+    uint32_t arrayLength = 0;
+    if (!JS::GetArrayLength(aCx, arrayObj, &arrayLength)) {
+      JS_ClearPendingException(aCx);
+      return;
+    }
+    nsTArray<nsString> array(arrayLength);
+    for (uint32_t arrayIdx = 0; arrayIdx < arrayLength; arrayIdx++) {
+      JS::Rooted<JS::Value> element(aCx);
+      if (!JS_GetElement(aCx, arrayObj, arrayIdx, &element)) {
+        JS_ClearPendingException(aCx);
+        return;
+      }
+      if (!element.isString()) {
+        return;
+      }
+      nsAutoJSString value;
+      if (!value.init(aCx, element)) {
+        JS_ClearPendingException(aCx);
+        return;
+      }
+      array.AppendElement(value);
+    }
+    SetElementAsMultiSelect(select, array);
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetSessionData(JSContext* aCx, Element* aElement,
+                           JS::MutableHandle<JS::Value> aObject) {
+  nsAutoString data;
+  if (nsContentUtils::StringifyJSON(aCx, aObject, data,
+                                    UndefinedIsNullStringLiteral)) {
+    SetElementAsString(aElement, data);
+  } else {
+    JS_ClearPendingException(aCx);
+  }
+}
+
+MOZ_CAN_RUN_SCRIPT
+static void SetInnerHTML(Document& aDocument, const nsString& aInnerHTML) {
+  RefPtr<Element> bodyElement = aDocument.GetBody();
+  if (bodyElement && bodyElement->IsInDesignMode()) {
+    IgnoredErrorResult rv;
+    bodyElement->SetInnerHTML(aInnerHTML, aDocument.NodePrincipal(), rv);
+    if (!rv.Failed()) {
+      nsContentUtils::DispatchInputEvent(bodyElement);
+    }
+  }
+}
+
+class FormDataParseContext : public txIParseContext {
+ public:
+  explicit FormDataParseContext(bool aCaseInsensitive)
+      : mIsCaseInsensitive(aCaseInsensitive) {}
+
+  nsresult resolveNamespacePrefix(nsAtom* aPrefix, int32_t& aID) override {
+    if (aPrefix == nsGkAtoms::xul) {
+      aID = kNameSpaceID_XUL;
+    } else {
+      MOZ_ASSERT(nsDependentAtomString(aPrefix).EqualsLiteral("xhtml"));
+      aID = kNameSpaceID_XHTML;
+    }
+    return NS_OK;
+  }
+
+  nsresult resolveFunctionCall(nsAtom* aName, int32_t aID,
+                               FunctionCall** aFunction) override {
+    return NS_ERROR_XPATH_UNKNOWN_FUNCTION;
+  }
+
+  bool caseInsensitiveNameTests() override { return mIsCaseInsensitive; }
+
+  void SetErrorOffset(uint32_t aOffset) override {}
+
+ private:
+  bool mIsCaseInsensitive;
+};
+
+static Element* FindNodeByXPath(Document& aDocument,
+                                const nsAString& aExpression) {
+  FormDataParseContext parsingContext(aDocument.IsHTMLDocument());
+  IgnoredErrorResult rv;
+  UniquePtr<XPathExpression> expression(
+      aDocument.XPathEvaluator()->CreateExpression(aExpression, &parsingContext,
+                                                   &aDocument, rv));
+  if (rv.Failed()) {
+    return nullptr;
+  }
+  RefPtr<XPathResult> result = expression->Evaluate(
+      aDocument, XPathResult::FIRST_ORDERED_NODE_TYPE, nullptr, rv);
+  if (rv.Failed()) {
+    return nullptr;
+  }
+  return Element::FromNodeOrNull(result->GetSingleNodeValue(rv));
+}
+
+/* static */
+bool SessionStoreUtils::RestoreFormData(const GlobalObject& aGlobal,
+                                        Document& aDocument,
+                                        const CollectedData& aData) {
+  if (!aData.mUrl.WasPassed()) {
+    return true;
+  }
+
+  // Don't restore any data for the given frame if the URL
+  // stored in the form data doesn't match its current URL.
+  nsAutoCString url;
+  Unused << aDocument.GetDocumentURI()->GetSpecIgnoringRef(url);
+  if (!aData.mUrl.Value().Equals(url)) {
+    return false;
+  }
+
+  using Change = SessionStoreChangeListener::Change;
+  SessionStoreChangeListener::CollectSessionStoreData(
+      aDocument.GetWindowContext(), EnumSet<Change>(Change::Input));
+
+  if (aData.mInnerHTML.WasPassed()) {
+    SetInnerHTML(aDocument, aData.mInnerHTML.Value());
+  }
+  if (aData.mId.WasPassed()) {
+    for (auto& entry : aData.mId.Value().Entries()) {
+      RefPtr<Element> node = aDocument.GetElementById(entry.mKey);
+      if (node == nullptr) {
+        continue;
+      }
+      if (entry.mValue.IsString()) {
+        SetElementAsString(node, entry.mValue.GetAsString());
+      } else if (entry.mValue.IsBoolean()) {
+        SetElementAsBool(node, entry.mValue.GetAsBoolean());
+      } else {
+        // For about:{sessionrestore,welcomeback} we saved the field as JSON to
+        // avoid nested instances causing humongous sessionstore.js files.
+        // cf. bug 467409
+        JSContext* cx = aGlobal.Context();
+        if (entry.mKey.EqualsLiteral("sessionData")) {
+          if (url.EqualsLiteral("about:sessionrestore") ||
+              url.EqualsLiteral("about:welcomeback")) {
+            JS::Rooted<JS::Value> object(
+                cx, JS::ObjectValue(*entry.mValue.GetAsObject()));
+            SetSessionData(cx, node, &object);
+            continue;
+          }
+        }
+        JS::Rooted<JS::Value> object(
+            cx, JS::ObjectValue(*entry.mValue.GetAsObject()));
+        SetElementAsObject(cx, node, object);
+      }
+    }
+  }
+
+  if (aData.mXpath.WasPassed()) {
+    for (auto& entry : aData.mXpath.Value().Entries()) {
+      RefPtr<Element> node = FindNodeByXPath(aDocument, entry.mKey);
+      if (node == nullptr) {
+        continue;
+      }
+      if (entry.mValue.IsString()) {
+        SetElementAsString(node, entry.mValue.GetAsString());
+      } else if (entry.mValue.IsBoolean()) {
+        SetElementAsBool(node, entry.mValue.GetAsBoolean());
+      } else {
+        JS::Rooted<JS::Value> object(
+            aGlobal.Context(), JS::ObjectValue(*entry.mValue.GetAsObject()));
+        SetElementAsObject(aGlobal.Context(), node, object);
+      }
+    }
+  }
+
+  return true;
+}
+
+MOZ_CAN_RUN_SCRIPT
+void RestoreFormEntry(Element* aNode, const FormEntryValue& aValue) {
+  using Type = sessionstore::FormEntryValue::Type;
+  switch (aValue.type()) {
+    case Type::TCheckbox:
+      SetElementAsBool(aNode, aValue.get_Checkbox().value());
+      break;
+    case Type::TTextField:
+      SetElementAsString(aNode, aValue.get_TextField().value());
+      break;
+    case Type::TFileList: {
+      if (RefPtr<HTMLInputElement> input = HTMLInputElement::FromNode(aNode);
+          input && input->ControlType() == FormControlType::InputFile) {
+        CollectedFileListValue value;
+        value.mFileList = aValue.get_FileList().valueList().Clone();
+        SetElementAsFiles(input, value);
+      }
+      break;
+    }
+    case Type::TSingleSelect: {
+      if (RefPtr<HTMLSelectElement> select = HTMLSelectElement::FromNode(aNode);
+          select && !select->Multiple()) {
+        CollectedNonMultipleSelectValue value;
+        value.mSelectedIndex = aValue.get_SingleSelect().index();
+        value.mValue = aValue.get_SingleSelect().value();
+        SetElementAsSelect(select, value);
+      }
+      break;
+    }
+    case Type::TMultipleSelect: {
+      if (RefPtr<HTMLSelectElement> select = HTMLSelectElement::FromNode(aNode);
+          select && select->Multiple()) {
+        SetElementAsMultiSelect(select,
+                                aValue.get_MultipleSelect().valueList());
+      }
+      break;
+    }
+    default:
+      MOZ_ASSERT_UNREACHABLE();
+  }
+}
+
+/* static */
+void SessionStoreUtils::RestoreFormData(
+    Document& aDocument, const nsString& aInnerHTML,
+    const nsTArray<SessionStoreRestoreData::Entry>& aEntries) {
+  using Change = SessionStoreChangeListener::Change;
+  SessionStoreChangeListener::CollectSessionStoreData(
+      aDocument.GetWindowContext(), EnumSet<Change>(Change::Input));
+
+  if (!aInnerHTML.IsEmpty()) {
+    SetInnerHTML(aDocument, aInnerHTML);
+  }
+
+  for (const auto& entry : aEntries) {
+    RefPtr<Element> node = entry.mIsXPath
+                               ? FindNodeByXPath(aDocument, entry.mData.id())
+                               : aDocument.GetElementById(entry.mData.id());
+    if (node) {
+      RestoreFormEntry(node, entry.mData.value());
+    }
+  }
+}
+
+typedef void (*CollectorFunc)(JSContext* aCx, Document& aDocument,
+                              Nullable<CollectedData>& aRetVal);
+
+/**
+ * A function that will recursively call |CollectorFunc| to collect data for all
+ * non-dynamic frames in the current frame/docShell tree.
+ */
+static void CollectFrameTreeData(JSContext* aCx,
+                                 BrowsingContext* aBrowsingContext,
+                                 Nullable<CollectedData>& aRetVal,
+                                 CollectorFunc aFunc) {
+  if (aBrowsingContext->CreatedDynamically()) {
+    return;
+  }
+
+  nsPIDOMWindowOuter* window = aBrowsingContext->GetDOMWindow();
+  if (!window || !window->GetDocShell()) {
+    return;
+  }
+
+  Document* document = window->GetExtantDoc();
+  if (!document) {
+    return;
+  }
+
+  /* Collect data from current frame */
+  aFunc(aCx, *document, aRetVal);
+
+  /* Collect data from all child frame */
+  nsTArray<JSObject*> childrenData;
+  SequenceRooter<JSObject*> rooter(aCx, &childrenData);
+  uint32_t trailingNullCounter = 0;
+
+  // This is not going to work for fission. Bug 1572084 for tracking it.
+  for (auto& child : aBrowsingContext->Children()) {
+    NullableRootedDictionary<CollectedData> data(aCx);
+    CollectFrameTreeData(aCx, child, data, aFunc);
+    if (data.IsNull()) {
+      childrenData.AppendElement(nullptr);
+      trailingNullCounter++;
+      continue;
+    }
+    JS::Rooted<JS::Value> jsval(aCx);
+    if (!ToJSValue(aCx, data.SetValue(), &jsval)) {
+      JS_ClearPendingException(aCx);
+      continue;
+    }
+    childrenData.AppendElement(&jsval.toObject());
+    trailingNullCounter = 0;
+  }
+
+  if (trailingNullCounter != childrenData.Length()) {
+    childrenData.TruncateLength(childrenData.Length() - trailingNullCounter);
+    aRetVal.SetValue().mChildren.Construct() = std::move(childrenData);
+  }
+}
+
+/* static */ void SessionStoreUtils::CollectScrollPosition(
+    const GlobalObject& aGlobal, WindowProxyHolder& aWindow,
+    Nullable<CollectedData>& aRetVal) {
+  CollectFrameTreeData(aGlobal.Context(), aWindow.get(), aRetVal,
+                       CollectCurrentScrollPosition);
+}
+
+/* static */ void SessionStoreUtils::CollectFormData(
+    const GlobalObject& aGlobal, WindowProxyHolder& aWindow,
+    Nullable<CollectedData>& aRetVal) {
+  CollectFrameTreeData(aGlobal.Context(), aWindow.get(), aRetVal,
+                       CollectCurrentFormData);
+}
+
+/* static */ void SessionStoreUtils::ComposeInputData(
+    const nsTArray<CollectedInputDataValue>& aData, InputElementData& ret) {
+  nsTArray<int> selectedIndex, valueIdx;
+  nsTArray<nsString> id, selectVal, strVal, type;
+  nsTArray<bool> boolVal;
+
+  for (const CollectedInputDataValue& data : aData) {
+    id.AppendElement(data.id);
+    type.AppendElement(data.type);
+
+    if (data.value.is<mozilla::dom::CollectedNonMultipleSelectValue>()) {
+      valueIdx.AppendElement(selectVal.Length());
+      selectedIndex.AppendElement(
+          data.value.as<mozilla::dom::CollectedNonMultipleSelectValue>()
+              .mSelectedIndex);
+      selectVal.AppendElement(
+          data.value.as<mozilla::dom::CollectedNonMultipleSelectValue>()
+              .mValue);
+    } else if (data.value.is<CopyableTArray<nsString>>()) {
+      // The first valueIdx is "index of the first string value"
+      valueIdx.AppendElement(strVal.Length());
+      strVal.AppendElements(data.value.as<CopyableTArray<nsString>>());
+      // The second valueIdx is "index of the last string value" + 1
+      id.AppendElement(data.id);
+      type.AppendElement(data.type);
+      valueIdx.AppendElement(strVal.Length());
+    } else if (data.value.is<nsString>()) {
+      valueIdx.AppendElement(strVal.Length());
+      strVal.AppendElement(data.value.as<nsString>());
+    } else if (data.type.EqualsLiteral("bool")) {
+      valueIdx.AppendElement(boolVal.Length());
+      boolVal.AppendElement(data.value.as<bool>());
+    }
+  }
+
+  if (selectedIndex.Length() != 0) {
+    ret.mSelectedIndex.Construct(std::move(selectedIndex));
+  }
+  if (valueIdx.Length() != 0) {
+    ret.mValueIdx.Construct(std::move(valueIdx));
+  }
+  if (id.Length() != 0) {
+    ret.mId.Construct(std::move(id));
+  }
+  if (selectVal.Length() != 0) {
+    ret.mSelectVal.Construct(std::move(selectVal));
+  }
+  if (strVal.Length() != 0) {
+    ret.mStrVal.Construct(std::move(strVal));
+  }
+  if (type.Length() != 0) {
+    ret.mType.Construct(std::move(type));
+  }
+  if (boolVal.Length() != 0) {
+    ret.mBoolVal.Construct(std::move(boolVal));
+  }
+}
+
+already_AddRefed<nsISessionStoreRestoreData>
+SessionStoreUtils::ConstructSessionStoreRestoreData(
+    const GlobalObject& aGlobal) {
+  nsCOMPtr<nsISessionStoreRestoreData> data = new SessionStoreRestoreData();
+  return data.forget();
+}
+
+/* static */
+already_AddRefed<Promise> SessionStoreUtils::InitializeRestore(
+    const GlobalObject& aGlobal, CanonicalBrowsingContext& aContext,
+    nsISessionStoreRestoreData* aData, ErrorResult& aError) {
+  if (!mozilla::SessionHistoryInParent()) {
+    MOZ_CRASH("why were we called?");
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(aContext.IsTop());
+
+  MOZ_DIAGNOSTIC_ASSERT(aData);
+  nsCOMPtr<SessionStoreRestoreData> data = do_QueryInterface(aData);
+  aContext.SetRestoreData(data, aError);
+  if (aError.Failed()) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsISHistory> shistory = aContext.GetSessionHistory();
+  MOZ_DIAGNOSTIC_ASSERT(shistory);
+  shistory->ReloadCurrentEntry();
+
+  return aContext.GetRestorePromise();
+}
+
+/* static */
+void SessionStoreUtils::RestoreDocShellState(
+    nsIDocShell* aDocShell, const DocShellRestoreState& aState) {
+  if (aDocShell) {
+    if (aState.URI()) {
+      aDocShell->SetCurrentURIForSessionStore(aState.URI());
+    }
+    RestoreDocShellCapabilities(aDocShell, aState.docShellCaps());
+  }
+}
+
+/* static */
+already_AddRefed<Promise> SessionStoreUtils::RestoreDocShellState(
+    const GlobalObject& aGlobal, CanonicalBrowsingContext& aContext,
+    const nsACString& aURL, const nsCString& aDocShellCaps,
+    ErrorResult& aError) {
+  MOZ_RELEASE_ASSERT(mozilla::SessionHistoryInParent());
+  MOZ_RELEASE_ASSERT(aContext.IsTop());
+
+  WindowGlobalParent* wgp = aContext.GetCurrentWindowGlobal();
+  if (!wgp) {
+    aError.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  MOZ_DIAGNOSTIC_ASSERT(global);
+
+  RefPtr<Promise> promise = Promise::Create(global, aError);
+  if (aError.Failed()) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  if (!aURL.IsEmpty()) {
+    if (NS_FAILED(NS_NewURI(getter_AddRefs(uri), aURL))) {
+      aError.Throw(NS_ERROR_FAILURE);
+      return nullptr;
+    }
+  }
+
+  bool allowJavascript = true;
+  for (const nsACString& token :
+       nsCCharSeparatedTokenizer(aDocShellCaps, ',').ToRange()) {
+    if (token.EqualsLiteral("Javascript")) {
+      allowJavascript = false;
+    }
+  }
+
+  Unused << aContext.SetAllowJavascript(allowJavascript);
+
+  DocShellRestoreState state = {uri, aDocShellCaps};
+
+  // TODO (anny): Investigate removing this roundtrip.
+  wgp->SendRestoreDocShellState(state)->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [promise](void) { promise->MaybeResolveWithUndefined(); },
+      [promise](void) { promise->MaybeRejectWithUndefined(); });
+
+  return promise.forget();
+}
+
+/* static */
+void SessionStoreUtils::RestoreSessionStorageFromParent(
+    const GlobalObject& aGlobal, const CanonicalBrowsingContext& aContext,
+    const Record<nsCString, Record<nsString, nsString>>& aSessionStorage) {
+  nsTArray<SSCacheCopy> cacheInitList;
+  for (const auto& originEntry : aSessionStorage.Entries()) {
+    nsCOMPtr<nsIPrincipal> storagePrincipal =
+        BasePrincipal::CreateContentPrincipal(originEntry.mKey);
+
+    nsCString originKey;
+    nsresult rv = storagePrincipal->GetStorageOriginKey(originKey);
+    if (NS_FAILED(rv)) {
+      continue;
+    }
+
+    SSCacheCopy& cacheInit = *cacheInitList.AppendElement();
+
+    cacheInit.originKey() = originKey;
+    PrincipalToPrincipalInfo(storagePrincipal, &cacheInit.principalInfo());
+
+    for (const auto& entry : originEntry.mValue.Entries()) {
+      SSSetItemInfo& setItemInfo = *cacheInit.data().AppendElement();
+      setItemInfo.key() = entry.mKey;
+      setItemInfo.value() = entry.mValue;
+    }
+  }
+
+  BackgroundSessionStorageManager::LoadData(aContext.Id(), cacheInitList);
+}
+
+/* static */
+nsresult SessionStoreUtils::ConstructFormDataValues(
+    JSContext* aCx, const nsTArray<sessionstore::FormEntry>& aValues,
+    nsTArray<Record<nsString, OwningStringOrBooleanOrObject>::EntryType>&
+        aEntries,
+    bool aParseSessionData) {
+  using EntryType = Record<nsString, OwningStringOrBooleanOrObject>::EntryType;
+
+  if (!aEntries.SetCapacity(aValues.Length(), fallible)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  for (const auto& value : aValues) {
+    EntryType* entry = aEntries.AppendElement();
+
+    using Type = sessionstore::FormEntryValue::Type;
+    switch (value.value().type()) {
+      case Type::TCheckbox:
+        entry->mValue.SetAsBoolean() = value.value().get_Checkbox().value();
+        break;
+      case Type::TTextField: {
+        if (aParseSessionData && value.id() == u"sessionData"_ns) {
+          JS::Rooted<JS::Value> jsval(aCx);
+          const auto& fieldValue = value.value().get_TextField().value();
+          if (!JS_ParseJSON(aCx, fieldValue.get(), fieldValue.Length(),
+                            &jsval) ||
+              !jsval.isObject()) {
+            return NS_ERROR_FAILURE;
+          }
+          entry->mValue.SetAsObject() = &jsval.toObject();
+        } else {
+          entry->mValue.SetAsString() = value.value().get_TextField().value();
+        }
+        break;
+      }
+      case Type::TFileList: {
+        CollectedFileListValue file;
+        file.mFileList = value.value().get_FileList().valueList().Clone();
+
+        JS::Rooted<JS::Value> jsval(aCx);
+        if (!ToJSValue(aCx, file, &jsval) || !jsval.isObject()) {
+          return NS_ERROR_FAILURE;
+        }
+        entry->mValue.SetAsObject() = &jsval.toObject();
+        break;
+      }
+      case Type::TSingleSelect: {
+        CollectedNonMultipleSelectValue select;
+        select.mSelectedIndex = value.value().get_SingleSelect().index();
+        select.mValue = value.value().get_SingleSelect().value();
+
+        JS::Rooted<JS::Value> jsval(aCx);
+        if (!ToJSValue(aCx, select, &jsval) || !jsval.isObject()) {
+          return NS_ERROR_FAILURE;
+        }
+        entry->mValue.SetAsObject() = &jsval.toObject();
+        break;
+      }
+      case Type::TMultipleSelect: {
+        JS::Rooted<JS::Value> jsval(aCx);
+        if (!ToJSValue(aCx, value.value().get_MultipleSelect().valueList(),
+                       &jsval) ||
+            !jsval.isObject()) {
+          return NS_ERROR_FAILURE;
+        }
+        entry->mValue.SetAsObject() = &jsval.toObject();
+        break;
+      }
+      default:
+        break;
+    }
+
+    entry->mKey = value.id();
+  }
+
+  return NS_OK;
+}
+
+static nsresult ConstructSessionStorageValue(
+    const nsTArray<SSSetItemInfo>& aValues,
+    Record<nsString, nsString>& aRecord) {
+  auto& entries = aRecord.Entries();
+  for (const auto& value : aValues) {
+    auto entry = entries.AppendElement();
+    entry->mKey = value.key();
+    entry->mValue = value.value();
+  }
+
+  return NS_OK;
+}
+
+/* static */
+nsresult SessionStoreUtils::ConstructSessionStorageValues(
+    CanonicalBrowsingContext* aBrowsingContext,
+    const nsTArray<SSCacheCopy>& aValues,
+    Record<nsCString, Record<nsString, nsString>>& aRecord) {
+  if (!aRecord.Entries().SetCapacity(aValues.Length(), fallible)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  for (const auto& value : aValues) {
+    auto storagePrincipal = PrincipalInfoToPrincipal(value.principalInfo());
+    if (storagePrincipal.isErr()) {
+      continue;
+    }
+
+    auto entry = aRecord.Entries().AppendElement();
+
+    if (!entry->mValue.Entries().SetCapacity(value.data().Length(), fallible)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    if (NS_FAILED(storagePrincipal.inspect()->GetOrigin(entry->mKey))) {
+      return NS_ERROR_FAILURE;
+    }
+
+    ConstructSessionStorageValue(value.data(), entry->mValue);
+  }
+
+  return NS_OK;
+}
+
+/* static */
+bool SessionStoreUtils::CopyProperty(JSContext* aCx, JS::Handle<JSObject*> aDst,
+                                     JS::Handle<JSObject*> aSrc,
+                                     const nsAString& aName) {
+  JS::Rooted<JS::PropertyKey> name(aCx);
+  const char16_t* data;
+  size_t length = aName.GetData(&data);
+
+  if (!JS_CharsToId(aCx, JS::TwoByteChars(data, length), &name)) {
+    return false;
+  }
+
+  bool found = false;
+  if (!JS_HasPropertyById(aCx, aSrc, name, &found) || !found) {
+    return true;
+  }
+
+  JS::Rooted<JS::Value> value(aCx);
+  if (!JS_GetPropertyById(aCx, aSrc, name, &value)) {
+    return false;
+  }
+
+  if (value.isNullOrUndefined()) {
+    return true;
+  }
+
+  return JS_DefinePropertyById(aCx, aDst, name, value, JSPROP_ENUMERATE);
+}
diff --git a/toolkit/components/sessionstore/SessionStoreUtils.h b/toolkit/components/sessionstore/SessionStoreUtils.h
new file mode 100644
index 0000000000..27922f1b51
--- /dev/null
+++ b/toolkit/components/sessionstore/SessionStoreUtils.h
@@ -0,0 +1,178 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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_SessionStoreUtils_h
+#define mozilla_dom_SessionStoreUtils_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/IntegerRange.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/SessionStoreUtilsBinding.h"
+#include "SessionStoreData.h"
+#include "SessionStoreRestoreData.h"
+
+class nsIDocument;
+class nsGlobalWindowInner;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class CanonicalBrowsingContext;
+class GlobalObject;
+struct SSScrollPositionDict;
+class SSCacheCopy;
+class SSSetItemInfo;
+
+namespace sessionstore {
+class DocShellRestoreState;
+class FormData;
+class FormEntry;
+class StorageEntry;
+}  // namespace sessionstore
+
+class SessionStoreUtils {
+ public:
+  MOZ_CAN_RUN_SCRIPT
+  static void ForEachNonDynamicChildFrame(
+      const GlobalObject& aGlobal, WindowProxyHolder& aWindow,
+      SessionStoreUtilsFrameCallback& aCallback, ErrorResult& aRv);
+
+  static already_AddRefed<nsISupports> AddDynamicFrameFilteredListener(
+      const GlobalObject& aGlobal, EventTarget& aTarget, const nsAString& aType,
+      JS::Handle<JS::Value> aListener, bool aUseCapture, bool aMozSystemGroup,
+      ErrorResult& aRv);
+
+  static void RemoveDynamicFrameFilteredListener(
+      const GlobalObject& aGlobal, EventTarget& aTarget, const nsAString& aType,
+      nsISupports* aListener, bool aUseCapture, bool aMozSystemGroup,
+      ErrorResult& aRv);
+
+  static void CollectDocShellCapabilities(const GlobalObject& aGlobal,
+                                          nsIDocShell* aDocShell,
+                                          nsCString& aRetVal);
+
+  static void RestoreDocShellCapabilities(
+      nsIDocShell* aDocShell, const nsCString& aDisallowCapabilities);
+  static void RestoreDocShellCapabilities(
+      const GlobalObject& aGlobal, nsIDocShell* aDocShell,
+      const nsCString& aDisallowCapabilities) {
+    return RestoreDocShellCapabilities(aDocShell, aDisallowCapabilities);
+  }
+
+  static void CollectScrollPosition(const GlobalObject& aGlobal,
+                                    WindowProxyHolder& aWindow,
+                                    Nullable<CollectedData>& aRetVal);
+
+  static void RestoreScrollPosition(const GlobalObject& aGlobal,
+                                    nsGlobalWindowInner& aWindow,
+                                    const CollectedData& data);
+  static void RestoreScrollPosition(nsGlobalWindowInner& aWindow,
+                                    const nsCString& aScrollPosition);
+
+  static uint32_t CollectFormData(Document* aDocument,
+                                  sessionstore::FormData& aFormData);
+
+  /*
+    @param aDocument: DOMDocument instance to obtain form data for.
+    @param aGeneratedCount: the current number of XPath expressions in the
+                            returned object.
+   */
+  template <typename... ArgsT>
+  static void CollectFromTextAreaElement(Document& aDocument,
+                                         uint16_t& aGeneratedCount,
+                                         ArgsT&&... args);
+  template <typename... ArgsT>
+  static void CollectFromInputElement(Document& aDocument,
+                                      uint16_t& aGeneratedCount,
+                                      ArgsT&&... args);
+  template <typename... ArgsT>
+  static void CollectFromSelectElement(Document& aDocument,
+                                       uint16_t& aGeneratedCount,
+                                       ArgsT&&... args);
+
+  static void CollectFormData(const GlobalObject& aGlobal,
+                              WindowProxyHolder& aWindow,
+                              Nullable<CollectedData>& aRetVal);
+
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  static bool RestoreFormData(const GlobalObject& aGlobal, Document& aDocument,
+                              const CollectedData& aData);
+  MOZ_CAN_RUN_SCRIPT static void RestoreFormData(
+      Document& aDocument, const nsString& aInnerHTML,
+      const nsTArray<SessionStoreRestoreData::Entry>& aEntries);
+
+  static void ComposeInputData(const nsTArray<CollectedInputDataValue>& aData,
+                               InputElementData& ret);
+
+  MOZ_CAN_RUN_SCRIPT static already_AddRefed<nsISessionStoreRestoreData>
+  ConstructSessionStoreRestoreData(const GlobalObject& aGlobal);
+
+  MOZ_CAN_RUN_SCRIPT static already_AddRefed<Promise> InitializeRestore(
+      const GlobalObject& aGlobal, CanonicalBrowsingContext& aContext,
+      nsISessionStoreRestoreData* aData, ErrorResult& aError);
+
+  static void RestoreDocShellState(
+      nsIDocShell* aDocShell, const sessionstore::DocShellRestoreState& aState);
+
+  static already_AddRefed<Promise> RestoreDocShellState(
+      const GlobalObject& aGlobal, CanonicalBrowsingContext& aContext,
+      const nsACString& aURL, const nsCString& aDocShellCaps,
+      ErrorResult& aError);
+
+  static void RestoreSessionStorageFromParent(
+      const GlobalObject& aGlobal, const CanonicalBrowsingContext& aContext,
+      const Record<nsCString, Record<nsString, nsString>>& aSessionStorage);
+
+  static nsresult ConstructFormDataValues(
+      JSContext* aCx, const nsTArray<sessionstore::FormEntry>& aValues,
+      nsTArray<Record<nsString, OwningStringOrBooleanOrObject>::EntryType>&
+          aEntries,
+      bool aParseSessionData = false);
+
+  static nsresult ConstructSessionStorageValues(
+      CanonicalBrowsingContext* aBrowsingContext,
+      const nsTArray<SSCacheCopy>& aValues,
+      Record<nsCString, Record<nsString, nsString>>& aStorage);
+
+  static bool CopyProperty(JSContext* aCx, JS::Handle<JSObject*> aDst,
+                           JS::Handle<JSObject*> aSrc, const nsAString& aName);
+
+  template <typename T>
+  static bool CopyChildren(JSContext* aCx, JS::Handle<JSObject*> aDst,
+                           const nsTArray<RefPtr<T>>& aChildren) {
+    if (!aChildren.IsEmpty()) {
+      JS::Rooted<JSObject*> children(
+          aCx, JS::NewArrayObject(aCx, aChildren.Length()));
+
+      for (const auto index : IntegerRange(aChildren.Length())) {
+        if (!aChildren[index]) {
+          continue;
+        }
+
+        JS::Rooted<JSObject*> object(aCx);
+        aChildren[index]->ToJSON(aCx, &object);
+
+        if (!JS_DefineElement(aCx, children, index, object, JSPROP_ENUMERATE)) {
+          return false;
+        }
+      }
+
+      if (!JS_DefineProperty(aCx, aDst, "children", children,
+                             JSPROP_ENUMERATE)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_SessionStoreUtils_h
diff --git a/toolkit/components/sessionstore/moz.build b/toolkit/components/sessionstore/moz.build
new file mode 100644
index 0000000000..9e8d2eb45e
--- /dev/null
+++ b/toolkit/components/sessionstore/moz.build
@@ -0,0 +1,55 @@
+# -*- 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/.
+
+EXPORTS.mozilla.dom += [
+    "BrowserSessionStore.h",
+    "SessionStoreChangeListener.h",
+    "SessionStoreChild.h",
+    "SessionStoreData.h",
+    "SessionStoreFormData.h",
+    "SessionStoreListener.h",
+    "SessionStoreMessageUtils.h",
+    "SessionStoreParent.h",
+    "SessionStoreRestoreData.h",
+    "SessionStoreScrollData.h",
+    "SessionStoreUtils.h",
+]
+
+UNIFIED_SOURCES += [
+    "BrowserSessionStore.cpp",
+    "RestoreTabContentObserver.cpp",
+    "SessionStoreChangeListener.cpp",
+    "SessionStoreChild.cpp",
+    "SessionStoreFormData.cpp",
+    "SessionStoreListener.cpp",
+    "SessionStoreParent.cpp",
+    "SessionStoreRestoreData.cpp",
+    "SessionStoreScrollData.cpp",
+    "SessionStoreUtils.cpp",
+]
+
+EXTRA_JS_MODULES += [
+    "SessionStoreFunctions.sys.mjs",
+]
+
+XPIDL_MODULE = "sessionstore"
+
+XPIDL_SOURCES += [
+    "nsISessionStoreRestoreData.idl",
+    "SessionStoreFunctions.idl",
+]
+
+IPDL_SOURCES += [
+    "PSessionStore.ipdl",
+    "SessionStoreTypes.ipdlh",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+with Files("**"):
+    BUG_COMPONENT = ("Firefox", "Session Restore")
diff --git a/toolkit/components/sessionstore/nsISessionStoreRestoreData.idl b/toolkit/components/sessionstore/nsISessionStoreRestoreData.idl
new file mode 100644
index 0000000000..8e8dc8b636
--- /dev/null
+++ b/toolkit/components/sessionstore/nsISessionStoreRestoreData.idl
@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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, uuid(cd9f33c5-460d-4bbf-a459-f375ca9566d8)]
+interface nsISessionStoreRestoreData : nsISupports {
+  // Setters for form data.
+  attribute AUTF8String url;
+  attribute AString innerHTML;
+
+  // Setters for scroll data.
+  attribute ACString scroll;
+
+  // Methods for adding individual form fields which are called as the JS code
+  // finds them.
+  void addTextField(in boolean aIsXPath, in AString aIdOrXPath,
+                    in AString aValue);
+  void addCheckbox(in boolean aIsXPath, in AString aIdOrXPath,
+                   in boolean aValue);
+  void addFileList(in boolean aIsXPath, in AString aIdOrXPath, in AString aType,
+                   in Array<AString> aFileList);
+  void addSingleSelect(in boolean aIsXPath, in AString aIdOrXPath,
+                       in unsigned long aSelectedIndex, in AString aValue);
+  void addMultipleSelect(in boolean aIsXPath, in AString aIdOrXPath,
+                         in Array<AString> aValues);
+
+  // Add a child data object to our children list.
+  void addChild(in nsISessionStoreRestoreData aChild, in unsigned long aIndex);
+};