Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

21 files changed, 6717 insertions, 0 deletions

diff --git a/toolkit/components/extensions/webrequest/ChannelWrapper.cpp b/toolkit/components/extensions/webrequest/ChannelWrapper.cpp
new file mode 100644
index 0000000000..2220d56b44
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/ChannelWrapper.cpp
@@ -0,0 +1,1273 @@
+/* -*- 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 "ChannelWrapper.h"
+
+#include "jsapi.h"
+#include "xpcpublic.h"
+
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/SystemPrincipal.h"
+
+#include "NSSErrorsService.h"
+#include "nsITransportSecurityInfo.h"
+
+#include "mozilla/AddonManagerWebAPI.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Components.h"
+#include "mozilla/ErrorNames.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/EventBinding.h"
+#include "mozilla/dom/BrowserHost.h"
+#include "mozIThirdPartyUtil.h"
+#include "nsContentUtils.h"
+#include "nsIContentPolicy.h"
+#include "nsIClassifiedChannel.h"
+#include "nsIHttpChannelInternal.h"
+#include "nsIHttpHeaderVisitor.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsILoadContext.h"
+#include "nsIProxiedChannel.h"
+#include "nsIProxyInfo.h"
+#include "nsITraceableChannel.h"
+#include "nsIWritablePropertyBag.h"
+#include "nsIWritablePropertyBag2.h"
+#include "nsNetUtil.h"
+#include "nsProxyRelease.h"
+#include "nsPrintfCString.h"
+
+using namespace mozilla::dom;
+using namespace JS;
+
+namespace mozilla {
+namespace extensions {
+
+#define CHANNELWRAPPER_PROP_KEY u"ChannelWrapper::CachedInstance"_ns
+
+using CF = nsIClassifiedChannel::ClassificationFlags;
+using MUC = MozUrlClassificationFlags;
+
+struct ClassificationStruct {
+  uint32_t mFlag;
+  MozUrlClassificationFlags mValue;
+};
+static const ClassificationStruct classificationArray[] = {
+    {CF::CLASSIFIED_FINGERPRINTING, MUC::Fingerprinting},
+    {CF::CLASSIFIED_FINGERPRINTING_CONTENT, MUC::Fingerprinting_content},
+    {CF::CLASSIFIED_CRYPTOMINING, MUC::Cryptomining},
+    {CF::CLASSIFIED_CRYPTOMINING_CONTENT, MUC::Cryptomining_content},
+    {CF::CLASSIFIED_EMAILTRACKING, MUC::Emailtracking},
+    {CF::CLASSIFIED_EMAILTRACKING_CONTENT, MUC::Emailtracking_content},
+    {CF::CLASSIFIED_TRACKING, MUC::Tracking},
+    {CF::CLASSIFIED_TRACKING_AD, MUC::Tracking_ad},
+    {CF::CLASSIFIED_TRACKING_ANALYTICS, MUC::Tracking_analytics},
+    {CF::CLASSIFIED_TRACKING_SOCIAL, MUC::Tracking_social},
+    {CF::CLASSIFIED_TRACKING_CONTENT, MUC::Tracking_content},
+    {CF::CLASSIFIED_SOCIALTRACKING, MUC::Socialtracking},
+    {CF::CLASSIFIED_SOCIALTRACKING_FACEBOOK, MUC::Socialtracking_facebook},
+    {CF::CLASSIFIED_SOCIALTRACKING_LINKEDIN, MUC::Socialtracking_linkedin},
+    {CF::CLASSIFIED_SOCIALTRACKING_TWITTER, MUC::Socialtracking_twitter},
+    {CF::CLASSIFIED_ANY_BASIC_TRACKING, MUC::Any_basic_tracking},
+    {CF::CLASSIFIED_ANY_STRICT_TRACKING, MUC::Any_strict_tracking},
+    {CF::CLASSIFIED_ANY_SOCIAL_TRACKING, MUC::Any_social_tracking}};
+
+/*****************************************************************************
+ * Lifetimes
+ *****************************************************************************/
+
+namespace {
+class ChannelListHolder : public LinkedList<ChannelWrapper> {
+ public:
+  ChannelListHolder() : LinkedList<ChannelWrapper>() {}
+
+  ~ChannelListHolder();
+};
+
+}  // anonymous namespace
+
+ChannelListHolder::~ChannelListHolder() {
+  while (ChannelWrapper* wrapper = popFirst()) {
+    wrapper->Die();
+  }
+}
+
+static LinkedList<ChannelWrapper>* GetChannelList() {
+  static UniquePtr<ChannelListHolder> sChannelList;
+  if (!sChannelList && !PastShutdownPhase(ShutdownPhase::XPCOMShutdown)) {
+    sChannelList.reset(new ChannelListHolder());
+    ClearOnShutdown(&sChannelList, ShutdownPhase::XPCOMShutdown);
+  }
+  return sChannelList.get();
+}
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(ChannelWrapper::ChannelWrapperStub)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(ChannelWrapper::ChannelWrapperStub)
+
+NS_IMPL_CYCLE_COLLECTION(ChannelWrapper::ChannelWrapperStub, mChannelWrapper)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ChannelWrapper::ChannelWrapperStub)
+  NS_INTERFACE_MAP_ENTRY_TEAROFF_AMBIGUOUS(ChannelWrapper, EventTarget,
+                                           mChannelWrapper)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+/*****************************************************************************
+ * Initialization
+ *****************************************************************************/
+
+ChannelWrapper::ChannelWrapper(nsISupports* aParent, nsIChannel* aChannel)
+    : ChannelHolder(aChannel), mParent(aParent) {
+  mStub = new ChannelWrapperStub(this);
+
+  if (auto* list = GetChannelList()) {
+    list->insertBack(this);
+  }
+}
+
+ChannelWrapper::~ChannelWrapper() {
+  if (LinkedListElement<ChannelWrapper>::isInList()) {
+    LinkedListElement<ChannelWrapper>::remove();
+  }
+}
+
+void ChannelWrapper::Die() {
+  if (mStub) {
+    mStub->mChannelWrapper = nullptr;
+  }
+}
+
+/* static */
+already_AddRefed<ChannelWrapper> ChannelWrapper::Get(const GlobalObject& global,
+                                                     nsIChannel* channel) {
+  RefPtr<ChannelWrapper> wrapper;
+
+  nsCOMPtr<nsIWritablePropertyBag2> props = do_QueryInterface(channel);
+  if (props) {
+    wrapper = do_GetProperty(props, CHANNELWRAPPER_PROP_KEY);
+    if (wrapper) {
+      // Assume cached attributes may have changed at this point.
+      wrapper->ClearCachedAttributes();
+    }
+  }
+
+  if (!wrapper) {
+    wrapper = new ChannelWrapper(global.GetAsSupports(), channel);
+    if (props) {
+      Unused << props->SetPropertyAsInterface(CHANNELWRAPPER_PROP_KEY,
+                                              wrapper->mStub);
+    }
+  }
+
+  return wrapper.forget();
+}
+
+already_AddRefed<ChannelWrapper> ChannelWrapper::GetRegisteredChannel(
+    const GlobalObject& global, uint64_t aChannelId,
+    const WebExtensionPolicy& aAddon, nsIRemoteTab* aRemoteTab) {
+  ContentParent* contentParent = nullptr;
+  if (BrowserHost* host = BrowserHost::GetFrom(aRemoteTab)) {
+    contentParent = host->GetActor()->Manager();
+  }
+
+  auto& webreq = WebRequestService::GetSingleton();
+
+  nsCOMPtr<nsITraceableChannel> channel =
+      webreq.GetTraceableChannel(aChannelId, aAddon.Id(), contentParent);
+  if (!channel) {
+    return nullptr;
+  }
+  nsCOMPtr<nsIChannel> chan(do_QueryInterface(channel));
+  return ChannelWrapper::Get(global, chan);
+}
+
+void ChannelWrapper::SetChannel(nsIChannel* aChannel) {
+  detail::ChannelHolder::SetChannel(aChannel);
+  ClearCachedAttributes();
+  ChannelWrapper_Binding::ClearCachedFinalURIValue(this);
+  ChannelWrapper_Binding::ClearCachedFinalURLValue(this);
+  mFinalURLInfo.reset();
+  ChannelWrapper_Binding::ClearCachedProxyInfoValue(this);
+}
+
+void ChannelWrapper::ClearCachedAttributes() {
+  ChannelWrapper_Binding::ClearCachedRemoteAddressValue(this);
+  ChannelWrapper_Binding::ClearCachedStatusCodeValue(this);
+  ChannelWrapper_Binding::ClearCachedStatusLineValue(this);
+  ChannelWrapper_Binding::ClearCachedUrlClassificationValue(this);
+  if (!mFiredErrorEvent) {
+    ChannelWrapper_Binding::ClearCachedErrorStringValue(this);
+  }
+
+  ChannelWrapper_Binding::ClearCachedRequestSizeValue(this);
+  ChannelWrapper_Binding::ClearCachedResponseSizeValue(this);
+}
+
+/*****************************************************************************
+ * ...
+ *****************************************************************************/
+
+void ChannelWrapper::Cancel(uint32_t aResult, uint32_t aReason,
+                            ErrorResult& aRv) {
+  nsresult rv = NS_ERROR_UNEXPECTED;
+  if (nsCOMPtr<nsIChannel> chan = MaybeChannel()) {
+    nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo();
+    if (aReason > 0 && loadInfo) {
+      loadInfo->SetRequestBlockingReason(aReason);
+    }
+    rv = chan->Cancel(nsresult(aResult));
+    ErrorCheck();
+  }
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
+void ChannelWrapper::RedirectTo(nsIURI* aURI, ErrorResult& aRv) {
+  nsresult rv = NS_ERROR_UNEXPECTED;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    rv = chan->RedirectTo(aURI);
+  }
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
+void ChannelWrapper::UpgradeToSecure(ErrorResult& aRv) {
+  nsresult rv = NS_ERROR_UNEXPECTED;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    rv = chan->UpgradeToSecure();
+  }
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
+void ChannelWrapper::Suspend(const nsCString& aProfileMarkerText,
+                             ErrorResult& aRv) {
+  if (!mSuspended) {
+    nsresult rv = NS_ERROR_UNEXPECTED;
+    if (nsCOMPtr<nsIChannel> chan = MaybeChannel()) {
+      rv = chan->Suspend();
+    }
+    if (NS_FAILED(rv)) {
+      aRv.Throw(rv);
+    } else {
+      mSuspended = true;
+      MOZ_ASSERT(mSuspendedMarkerText.IsVoid());
+      mSuspendedMarkerText = aProfileMarkerText;
+      PROFILER_MARKER_TEXT("Extension Suspend", NETWORK,
+                           MarkerOptions(MarkerTiming::IntervalStart()),
+                           mSuspendedMarkerText);
+    }
+  }
+}
+
+void ChannelWrapper::Resume(ErrorResult& aRv) {
+  if (mSuspended) {
+    nsresult rv = NS_ERROR_UNEXPECTED;
+    if (nsCOMPtr<nsIChannel> chan = MaybeChannel()) {
+      rv = chan->Resume();
+    }
+    if (NS_FAILED(rv)) {
+      aRv.Throw(rv);
+    } else {
+      mSuspended = false;
+      PROFILER_MARKER_TEXT("Extension Suspend", NETWORK,
+                           MarkerOptions(MarkerTiming::IntervalEnd()),
+                           mSuspendedMarkerText);
+      mSuspendedMarkerText = VoidCString();
+    }
+  }
+}
+
+void ChannelWrapper::GetContentType(nsCString& aContentType) const {
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->GetContentType(aContentType);
+  }
+}
+
+void ChannelWrapper::SetContentType(const nsACString& aContentType) {
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->SetContentType(aContentType);
+  }
+}
+
+/*****************************************************************************
+ * Headers
+ *****************************************************************************/
+
+namespace {
+
+class MOZ_STACK_CLASS HeaderVisitor final : public nsIHttpHeaderVisitor {
+ public:
+  NS_DECL_NSIHTTPHEADERVISITOR
+
+  explicit HeaderVisitor(nsTArray<dom::MozHTTPHeader>& aHeaders)
+      : mHeaders(aHeaders) {}
+
+  HeaderVisitor(nsTArray<dom::MozHTTPHeader>& aHeaders,
+                const nsCString& aContentTypeHdr)
+      : mHeaders(aHeaders), mContentTypeHdr(aContentTypeHdr) {}
+
+  void VisitRequestHeaders(nsIHttpChannel* aChannel, ErrorResult& aRv) {
+    CheckResult(aChannel->VisitRequestHeaders(this), aRv);
+  }
+
+  void VisitResponseHeaders(nsIHttpChannel* aChannel, ErrorResult& aRv) {
+    CheckResult(aChannel->VisitResponseHeaders(this), aRv);
+  }
+
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+
+  // Stub AddRef/Release since this is a stack class.
+  NS_IMETHOD_(MozExternalRefCountType) AddRef(void) override {
+    return ++mRefCnt;
+  }
+
+  NS_IMETHOD_(MozExternalRefCountType) Release(void) override {
+    return --mRefCnt;
+  }
+
+  virtual ~HeaderVisitor() { MOZ_DIAGNOSTIC_ASSERT(mRefCnt == 0); }
+
+ private:
+  bool CheckResult(nsresult aNSRv, ErrorResult& aRv) {
+    if (NS_FAILED(aNSRv)) {
+      aRv.Throw(aNSRv);
+      return false;
+    }
+    return true;
+  }
+
+  nsTArray<dom::MozHTTPHeader>& mHeaders;
+  nsCString mContentTypeHdr = VoidCString();
+
+  nsrefcnt mRefCnt = 0;
+};
+
+NS_IMETHODIMP
+HeaderVisitor::VisitHeader(const nsACString& aHeader,
+                           const nsACString& aValue) {
+  auto dict = mHeaders.AppendElement(fallible);
+  if (!dict) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  dict->mName = aHeader;
+
+  if (!mContentTypeHdr.IsVoid() &&
+      aHeader.LowerCaseEqualsLiteral("content-type")) {
+    dict->mValue = mContentTypeHdr;
+  } else {
+    dict->mValue = aValue;
+  }
+
+  return NS_OK;
+}
+
+NS_IMPL_QUERY_INTERFACE(HeaderVisitor, nsIHttpHeaderVisitor)
+
+}  // anonymous namespace
+
+void ChannelWrapper::GetRequestHeaders(nsTArray<dom::MozHTTPHeader>& aRetVal,
+                                       ErrorResult& aRv) const {
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    HeaderVisitor visitor(aRetVal);
+    visitor.VisitRequestHeaders(chan, aRv);
+  } else {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+  }
+}
+
+void ChannelWrapper::GetRequestHeader(const nsCString& aHeader,
+                                      nsCString& aResult,
+                                      ErrorResult& aRv) const {
+  aResult.SetIsVoid(true);
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->GetRequestHeader(aHeader, aResult);
+  } else {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+  }
+}
+
+void ChannelWrapper::GetResponseHeaders(nsTArray<dom::MozHTTPHeader>& aRetVal,
+                                        ErrorResult& aRv) const {
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    HeaderVisitor visitor(aRetVal, mContentTypeHdr);
+    visitor.VisitResponseHeaders(chan, aRv);
+  } else {
+    aRv.Throw(NS_ERROR_UNEXPECTED);
+  }
+}
+
+void ChannelWrapper::SetRequestHeader(const nsCString& aHeader,
+                                      const nsCString& aValue, bool aMerge,
+                                      ErrorResult& aRv) {
+  nsresult rv = NS_ERROR_UNEXPECTED;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    rv = chan->SetRequestHeader(aHeader, aValue, aMerge);
+  }
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
+void ChannelWrapper::SetResponseHeader(const nsCString& aHeader,
+                                       const nsCString& aValue, bool aMerge,
+                                       ErrorResult& aRv) {
+  nsresult rv = NS_ERROR_UNEXPECTED;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    if (aHeader.LowerCaseEqualsLiteral("content-type")) {
+      rv = chan->SetContentType(aValue);
+      if (NS_SUCCEEDED(rv)) {
+        mContentTypeHdr = aValue;
+      }
+    } else {
+      rv = chan->SetResponseHeader(aHeader, aValue, aMerge);
+    }
+  }
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
+/*****************************************************************************
+ * LoadInfo
+ *****************************************************************************/
+
+already_AddRefed<nsILoadContext> ChannelWrapper::GetLoadContext() const {
+  if (nsCOMPtr<nsIChannel> chan = MaybeChannel()) {
+    nsCOMPtr<nsILoadContext> ctxt;
+    // Fetch() from Workers saves BrowsingContext/LoadContext information in
+    // nsILoadInfo.workerAssociatedBrowsingContext. So we can not use
+    // NS_QueryNotificationCallbacks to get LoadContext of the channel.
+    RefPtr<BrowsingContext> bc;
+    nsCOMPtr<nsILoadInfo> loadInfo = chan->LoadInfo();
+    loadInfo->GetWorkerAssociatedBrowsingContext(getter_AddRefs(bc));
+    if (bc) {
+      ctxt = bc.forget();
+      return ctxt.forget();
+    }
+    NS_QueryNotificationCallbacks(chan, ctxt);
+    return ctxt.forget();
+  }
+  return nullptr;
+}
+
+already_AddRefed<Element> ChannelWrapper::GetBrowserElement() const {
+  if (nsCOMPtr<nsILoadContext> ctxt = GetLoadContext()) {
+    RefPtr<Element> elem;
+    if (NS_SUCCEEDED(ctxt->GetTopFrameElement(getter_AddRefs(elem)))) {
+      return elem.forget();
+    }
+  }
+  return nullptr;
+}
+
+bool ChannelWrapper::IsServiceWorkerScript() const {
+  nsCOMPtr<nsIChannel> chan = MaybeChannel();
+  return IsServiceWorkerScript(chan);
+}
+
+// static
+bool ChannelWrapper::IsServiceWorkerScript(const nsCOMPtr<nsIChannel>& chan) {
+  nsCOMPtr<nsILoadInfo> loadInfo;
+
+  if (chan) {
+    chan->GetLoadInfo(getter_AddRefs(loadInfo));
+  }
+
+  if (loadInfo) {
+    // Not a script.
+    if (loadInfo->GetExternalContentPolicyType() !=
+        ExtContentPolicy::TYPE_SCRIPT) {
+      return false;
+    }
+
+    // Service worker main script load.
+    if (loadInfo->InternalContentPolicyType() ==
+        nsIContentPolicy::TYPE_INTERNAL_SERVICE_WORKER) {
+      return true;
+    }
+
+    // Service worker import scripts load.
+    if (loadInfo->InternalContentPolicyType() ==
+            nsIContentPolicy::TYPE_INTERNAL_WORKER_IMPORT_SCRIPTS ||
+        loadInfo->InternalContentPolicyType() ==
+            nsIContentPolicy::TYPE_INTERNAL_WORKER_STATIC_MODULE) {
+      nsLoadFlags loadFlags = 0;
+      chan->GetLoadFlags(&loadFlags);
+      return loadFlags & nsIChannel::LOAD_BYPASS_SERVICE_WORKER;
+    }
+  }
+
+  return false;
+}
+
+static inline bool IsSystemPrincipal(nsIPrincipal* aPrincipal) {
+  return BasePrincipal::Cast(aPrincipal)->Is<SystemPrincipal>();
+}
+
+bool ChannelWrapper::IsSystemLoad() const {
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    if (nsIPrincipal* prin = loadInfo->GetLoadingPrincipal()) {
+      return IsSystemPrincipal(prin);
+    }
+
+    if (RefPtr<BrowsingContext> bc = loadInfo->GetBrowsingContext();
+        !bc || bc->IsTop()) {
+      return false;
+    }
+
+    if (nsIPrincipal* prin = loadInfo->PrincipalToInherit()) {
+      return IsSystemPrincipal(prin);
+    }
+    if (nsIPrincipal* prin = loadInfo->TriggeringPrincipal()) {
+      return IsSystemPrincipal(prin);
+    }
+  }
+  return false;
+}
+
+bool ChannelWrapper::CanModify() const {
+  if (WebExtensionPolicy::IsRestrictedURI(FinalURLInfo())) {
+    return false;
+  }
+
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    if (nsIPrincipal* prin = loadInfo->GetLoadingPrincipal()) {
+      if (IsSystemPrincipal(prin)) {
+        return false;
+      }
+
+      auto* docURI = DocumentURLInfo();
+      if (docURI && WebExtensionPolicy::IsRestrictedURI(*docURI)) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+already_AddRefed<nsIURI> ChannelWrapper::GetOriginURI() const {
+  nsCOMPtr<nsIURI> uri;
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    if (nsIPrincipal* prin = loadInfo->TriggeringPrincipal()) {
+      if (prin->GetIsContentPrincipal()) {
+        auto* basePrin = BasePrincipal::Cast(prin);
+        Unused << basePrin->GetURI(getter_AddRefs(uri));
+      }
+    }
+  }
+  return uri.forget();
+}
+
+already_AddRefed<nsIURI> ChannelWrapper::GetDocumentURI() const {
+  nsCOMPtr<nsIURI> uri;
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    if (nsIPrincipal* prin = loadInfo->GetLoadingPrincipal()) {
+      if (prin->GetIsContentPrincipal()) {
+        auto* basePrin = BasePrincipal::Cast(prin);
+        Unused << basePrin->GetURI(getter_AddRefs(uri));
+      }
+    }
+  }
+  return uri.forget();
+}
+
+void ChannelWrapper::GetOriginURL(nsCString& aRetVal) const {
+  if (nsCOMPtr<nsIURI> uri = GetOriginURI()) {
+    Unused << uri->GetSpec(aRetVal);
+  }
+}
+
+void ChannelWrapper::GetDocumentURL(nsCString& aRetVal) const {
+  if (nsCOMPtr<nsIURI> uri = GetDocumentURI()) {
+    Unused << uri->GetSpec(aRetVal);
+  }
+}
+
+const URLInfo& ChannelWrapper::FinalURLInfo() const {
+  if (mFinalURLInfo.isNothing()) {
+    ErrorResult rv;
+    nsCOMPtr<nsIURI> uri = FinalURI();
+    MOZ_ASSERT(uri);
+
+    // If this is a view-source scheme, get the nested uri.
+    while (uri && uri->SchemeIs("view-source")) {
+      nsCOMPtr<nsINestedURI> nested = do_QueryInterface(uri);
+      if (!nested) {
+        break;
+      }
+      nested->GetInnerURI(getter_AddRefs(uri));
+    }
+    mFinalURLInfo.emplace(uri.get(), true);
+
+    // If this is a WebSocket request, mangle the URL so that the scheme is
+    // ws: or wss:, as appropriate.
+    auto& url = mFinalURLInfo.ref();
+    if (Type() == MozContentPolicyType::Websocket &&
+        (url.Scheme() == nsGkAtoms::http || url.Scheme() == nsGkAtoms::https)) {
+      nsAutoCString spec(url.CSpec());
+      spec.Replace(0, 4, "ws"_ns);
+
+      Unused << NS_NewURI(getter_AddRefs(uri), spec);
+      MOZ_RELEASE_ASSERT(uri);
+      mFinalURLInfo.reset();
+      mFinalURLInfo.emplace(uri.get(), true);
+    }
+  }
+  return mFinalURLInfo.ref();
+}
+
+const URLInfo* ChannelWrapper::DocumentURLInfo() const {
+  if (mDocumentURLInfo.isNothing()) {
+    nsCOMPtr<nsIURI> uri = GetDocumentURI();
+    if (!uri) {
+      return nullptr;
+    }
+    mDocumentURLInfo.emplace(uri.get(), true);
+  }
+  return &mDocumentURLInfo.ref();
+}
+
+bool ChannelWrapper::Matches(
+    const dom::MozRequestFilter& aFilter, const WebExtensionPolicy* aExtension,
+    const dom::MozRequestMatchOptions& aOptions) const {
+  if (!HaveChannel()) {
+    return false;
+  }
+
+  if (!aFilter.mTypes.IsNull() && !aFilter.mTypes.Value().Contains(Type())) {
+    return false;
+  }
+
+  auto& urlInfo = FinalURLInfo();
+  if (aFilter.mUrls && !aFilter.mUrls->Matches(urlInfo)) {
+    return false;
+  }
+
+  nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo();
+  bool isPrivate =
+      loadInfo && loadInfo->GetOriginAttributes().mPrivateBrowsingId > 0;
+  if (!aFilter.mIncognito.IsNull() && aFilter.mIncognito.Value() != isPrivate) {
+    return false;
+  }
+
+  if (aExtension) {
+    // Verify extension access to private requests
+    if (isPrivate && !aExtension->PrivateBrowsingAllowed()) {
+      return false;
+    }
+
+    bool isProxy =
+        aOptions.mIsProxy && aExtension->HasPermission(nsGkAtoms::proxy);
+    // Proxies are allowed access to all urls, including restricted urls.
+    if (!aExtension->CanAccessURI(urlInfo, false, !isProxy, true)) {
+      return false;
+    }
+
+    // If this isn't the proxy phase of the request, check that the extension
+    // has origin permissions for origin that originated the request.
+    if (!isProxy) {
+      if (IsSystemLoad()) {
+        return false;
+      }
+
+      auto origin = DocumentURLInfo();
+      // Extensions with the file:-permission may observe requests from file:
+      // origins, because such documents can already be modified by content
+      // scripts anyway.
+      if (origin && !aExtension->CanAccessURI(*origin, false, true, true)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+int64_t NormalizeFrameID(nsILoadInfo* aLoadInfo, uint64_t bcID) {
+  RefPtr<BrowsingContext> bc = aLoadInfo->GetWorkerAssociatedBrowsingContext();
+  if (!bc) {
+    bc = aLoadInfo->GetBrowsingContext();
+  }
+
+  if (!bc || bcID == bc->Top()->Id()) {
+    return 0;
+  }
+  return bcID;
+}
+
+uint64_t ChannelWrapper::BrowsingContextId(nsILoadInfo* aLoadInfo) const {
+  auto frameID = aLoadInfo->GetFrameBrowsingContextID();
+  if (!frameID) {
+    frameID = aLoadInfo->GetWorkerAssociatedBrowsingContextID();
+  }
+  if (!frameID) {
+    frameID = aLoadInfo->GetBrowsingContextID();
+  }
+  return frameID;
+}
+
+int64_t ChannelWrapper::FrameId() const {
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    return NormalizeFrameID(loadInfo, BrowsingContextId(loadInfo));
+  }
+  return 0;
+}
+
+int64_t ChannelWrapper::ParentFrameId() const {
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    RefPtr<BrowsingContext> bc = loadInfo->GetWorkerAssociatedBrowsingContext();
+    if (!bc) {
+      bc = loadInfo->GetBrowsingContext();
+    }
+    if (bc) {
+      if (BrowsingContextId(loadInfo) == bc->Top()->Id()) {
+        return -1;
+      }
+
+      uint64_t parentID = -1;
+      if (loadInfo->GetFrameBrowsingContextID()) {
+        parentID = loadInfo->GetBrowsingContextID();
+      } else if (bc->GetParent()) {
+        parentID = bc->GetParent()->Id();
+      }
+      return NormalizeFrameID(loadInfo, parentID);
+    }
+  }
+  return -1;
+}
+
+void ChannelWrapper::GetFrameAncestors(
+    dom::Nullable<nsTArray<dom::MozFrameAncestorInfo>>& aFrameAncestors,
+    ErrorResult& aRv) const {
+  nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo();
+  if (!loadInfo || BrowsingContextId(loadInfo) == 0) {
+    aFrameAncestors.SetNull();
+    return;
+  }
+
+  nsresult rv = GetFrameAncestors(loadInfo, aFrameAncestors.SetValue());
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
+nsresult ChannelWrapper::GetFrameAncestors(
+    nsILoadInfo* aLoadInfo,
+    nsTArray<dom::MozFrameAncestorInfo>& aFrameAncestors) const {
+  const nsTArray<nsCOMPtr<nsIPrincipal>>& ancestorPrincipals =
+      aLoadInfo->AncestorPrincipals();
+  const nsTArray<uint64_t>& ancestorBrowsingContextIDs =
+      aLoadInfo->AncestorBrowsingContextIDs();
+  uint32_t size = ancestorPrincipals.Length();
+  MOZ_DIAGNOSTIC_ASSERT(size == ancestorBrowsingContextIDs.Length());
+  if (size != ancestorBrowsingContextIDs.Length()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  bool subFrame = aLoadInfo->GetExternalContentPolicyType() ==
+                  ExtContentPolicy::TYPE_SUBDOCUMENT;
+  if (!aFrameAncestors.SetCapacity(subFrame ? size : size + 1, fallible)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  // The immediate parent is always the first element in the ancestor arrays,
+  // however SUBDOCUMENTs do not have their immediate parent included, so we
+  // inject it here. This will force wrapper.parentBrowsingContextId ==
+  // wrapper.frameAncestors[0].frameId to always be true.  All ather requests
+  // already match this way.
+  if (subFrame) {
+    auto ancestor = aFrameAncestors.AppendElement();
+    GetDocumentURL(ancestor->mUrl);
+    ancestor->mFrameId = ParentFrameId();
+  }
+
+  for (uint32_t i = 0; i < size; ++i) {
+    auto ancestor = aFrameAncestors.AppendElement();
+    MOZ_TRY(ancestorPrincipals[i]->GetAsciiSpec(ancestor->mUrl));
+    ancestor->mFrameId =
+        NormalizeFrameID(aLoadInfo, ancestorBrowsingContextIDs[i]);
+  }
+  return NS_OK;
+}
+
+/*****************************************************************************
+ * Response filtering
+ *****************************************************************************/
+
+void ChannelWrapper::RegisterTraceableChannel(const WebExtensionPolicy& aAddon,
+                                              nsIRemoteTab* aBrowserParent) {
+  // We can't attach new listeners after the response has started, so don't
+  // bother registering anything.
+  if (mResponseStarted || !CanModify()) {
+    return;
+  }
+
+  mAddonEntries.InsertOrUpdate(aAddon.Id(), aBrowserParent);
+  if (!mChannelEntry) {
+    mChannelEntry = WebRequestService::GetSingleton().RegisterChannel(this);
+    CheckEventListeners();
+  }
+}
+
+already_AddRefed<nsITraceableChannel> ChannelWrapper::GetTraceableChannel(
+    nsAtom* aAddonId, dom::ContentParent* aContentParent) const {
+  nsCOMPtr<nsIRemoteTab> remoteTab;
+  if (mAddonEntries.Get(aAddonId, getter_AddRefs(remoteTab))) {
+    ContentParent* contentParent = nullptr;
+    if (remoteTab) {
+      contentParent =
+          BrowserHost::GetFrom(remoteTab.get())->GetActor()->Manager();
+    }
+
+    if (contentParent == aContentParent) {
+      nsCOMPtr<nsITraceableChannel> chan = QueryChannel();
+      return chan.forget();
+    }
+  }
+  return nullptr;
+}
+
+/*****************************************************************************
+ * ...
+ *****************************************************************************/
+
+MozContentPolicyType GetContentPolicyType(ExtContentPolicyType aType) {
+  // Note: Please keep this function in sync with the external types in
+  // nsIContentPolicy.idl
+  switch (aType) {
+    case ExtContentPolicy::TYPE_DOCUMENT:
+      return MozContentPolicyType::Main_frame;
+    case ExtContentPolicy::TYPE_SUBDOCUMENT:
+      return MozContentPolicyType::Sub_frame;
+    case ExtContentPolicy::TYPE_STYLESHEET:
+      return MozContentPolicyType::Stylesheet;
+    case ExtContentPolicy::TYPE_SCRIPT:
+      return MozContentPolicyType::Script;
+    case ExtContentPolicy::TYPE_IMAGE:
+      return MozContentPolicyType::Image;
+    case ExtContentPolicy::TYPE_OBJECT:
+      return MozContentPolicyType::Object;
+    case ExtContentPolicy::TYPE_OBJECT_SUBREQUEST:
+      return MozContentPolicyType::Object_subrequest;
+    case ExtContentPolicy::TYPE_XMLHTTPREQUEST:
+      return MozContentPolicyType::Xmlhttprequest;
+    // TYPE_FETCH returns xmlhttprequest for cross-browser compatibility.
+    case ExtContentPolicy::TYPE_FETCH:
+      return MozContentPolicyType::Xmlhttprequest;
+    case ExtContentPolicy::TYPE_XSLT:
+      return MozContentPolicyType::Xslt;
+    case ExtContentPolicy::TYPE_PING:
+      return MozContentPolicyType::Ping;
+    case ExtContentPolicy::TYPE_BEACON:
+      return MozContentPolicyType::Beacon;
+    case ExtContentPolicy::TYPE_DTD:
+      return MozContentPolicyType::Xml_dtd;
+    case ExtContentPolicy::TYPE_FONT:
+    case ExtContentPolicy::TYPE_UA_FONT:
+      return MozContentPolicyType::Font;
+    case ExtContentPolicy::TYPE_MEDIA:
+      return MozContentPolicyType::Media;
+    case ExtContentPolicy::TYPE_WEBSOCKET:
+      return MozContentPolicyType::Websocket;
+    case ExtContentPolicy::TYPE_CSP_REPORT:
+      return MozContentPolicyType::Csp_report;
+    case ExtContentPolicy::TYPE_IMAGESET:
+      return MozContentPolicyType::Imageset;
+    case ExtContentPolicy::TYPE_WEB_MANIFEST:
+      return MozContentPolicyType::Web_manifest;
+    case ExtContentPolicy::TYPE_SPECULATIVE:
+      return MozContentPolicyType::Speculative;
+    case ExtContentPolicy::TYPE_PROXIED_WEBRTC_MEDIA:
+    case ExtContentPolicy::TYPE_INVALID:
+    case ExtContentPolicy::TYPE_OTHER:
+    case ExtContentPolicy::TYPE_SAVEAS_DOWNLOAD:
+      break;
+      // Do not add default: so that compilers can catch the missing case.
+  }
+  return MozContentPolicyType::Other;
+}
+
+MozContentPolicyType ChannelWrapper::Type() const {
+  if (nsCOMPtr<nsILoadInfo> loadInfo = GetLoadInfo()) {
+    return GetContentPolicyType(loadInfo->GetExternalContentPolicyType());
+  }
+  return MozContentPolicyType::Other;
+}
+
+void ChannelWrapper::GetMethod(nsCString& aMethod) const {
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->GetRequestMethod(aMethod);
+  }
+}
+
+/*****************************************************************************
+ * ...
+ *****************************************************************************/
+
+uint32_t ChannelWrapper::StatusCode() const {
+  uint32_t result = 0;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->GetResponseStatus(&result);
+  }
+  return result;
+}
+
+void ChannelWrapper::GetStatusLine(nsCString& aRetVal) const {
+  nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel();
+  nsCOMPtr<nsIHttpChannelInternal> internal = do_QueryInterface(chan);
+
+  if (internal) {
+    nsAutoCString statusText;
+    uint32_t major, minor, status;
+    if (NS_FAILED(chan->GetResponseStatus(&status)) ||
+        NS_FAILED(chan->GetResponseStatusText(statusText)) ||
+        NS_FAILED(internal->GetResponseVersion(&major, &minor))) {
+      return;
+    }
+
+    aRetVal = nsPrintfCString("HTTP/%u.%u %u %s", major, minor, status,
+                              statusText.get());
+  }
+}
+
+uint64_t ChannelWrapper::ResponseSize() const {
+  uint64_t result = 0;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->GetTransferSize(&result);
+  }
+  return result;
+}
+
+uint64_t ChannelWrapper::RequestSize() const {
+  uint64_t result = 0;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    Unused << chan->GetRequestSize(&result);
+  }
+  return result;
+}
+
+/*****************************************************************************
+ * ...
+ *****************************************************************************/
+
+already_AddRefed<nsIURI> ChannelWrapper::FinalURI() const {
+  nsCOMPtr<nsIURI> uri;
+  if (nsCOMPtr<nsIChannel> chan = MaybeChannel()) {
+    NS_GetFinalChannelURI(chan, getter_AddRefs(uri));
+  }
+  return uri.forget();
+}
+
+void ChannelWrapper::GetFinalURL(nsString& aRetVal) const {
+  if (HaveChannel()) {
+    aRetVal = FinalURLInfo().Spec();
+  }
+}
+
+/*****************************************************************************
+ * ...
+ *****************************************************************************/
+
+nsresult FillProxyInfo(MozProxyInfo& aDict, nsIProxyInfo* aProxyInfo) {
+  MOZ_TRY(aProxyInfo->GetHost(aDict.mHost));
+  MOZ_TRY(aProxyInfo->GetPort(&aDict.mPort));
+  MOZ_TRY(aProxyInfo->GetType(aDict.mType));
+  MOZ_TRY(aProxyInfo->GetUsername(aDict.mUsername));
+  MOZ_TRY(
+      aProxyInfo->GetProxyAuthorizationHeader(aDict.mProxyAuthorizationHeader));
+  MOZ_TRY(aProxyInfo->GetConnectionIsolationKey(aDict.mConnectionIsolationKey));
+  MOZ_TRY(aProxyInfo->GetFailoverTimeout(&aDict.mFailoverTimeout.Construct()));
+
+  uint32_t flags;
+  MOZ_TRY(aProxyInfo->GetFlags(&flags));
+  aDict.mProxyDNS = flags & nsIProxyInfo::TRANSPARENT_PROXY_RESOLVES_HOST;
+
+  return NS_OK;
+}
+
+void ChannelWrapper::GetProxyInfo(dom::Nullable<MozProxyInfo>& aRetVal,
+                                  ErrorResult& aRv) const {
+  nsCOMPtr<nsIProxyInfo> proxyInfo;
+  if (nsCOMPtr<nsIProxiedChannel> proxied = QueryChannel()) {
+    Unused << proxied->GetProxyInfo(getter_AddRefs(proxyInfo));
+  }
+  if (proxyInfo) {
+    MozProxyInfo result;
+
+    nsresult rv = FillProxyInfo(result, proxyInfo);
+    if (NS_FAILED(rv)) {
+      aRv.Throw(rv);
+    } else {
+      aRetVal.SetValue(std::move(result));
+    }
+  }
+}
+
+void ChannelWrapper::GetRemoteAddress(nsCString& aRetVal) const {
+  aRetVal.SetIsVoid(true);
+  if (nsCOMPtr<nsIHttpChannelInternal> internal = QueryChannel()) {
+    Unused << internal->GetRemoteAddress(aRetVal);
+  }
+}
+
+void FillClassification(
+    Sequence<mozilla::dom::MozUrlClassificationFlags>& classifications,
+    uint32_t classificationFlags, ErrorResult& aRv) {
+  if (classificationFlags == 0) {
+    return;
+  }
+  for (const auto& entry : classificationArray) {
+    if (classificationFlags & entry.mFlag) {
+      if (!classifications.AppendElement(entry.mValue, mozilla::fallible)) {
+        aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+        return;
+      }
+    }
+  }
+}
+
+void ChannelWrapper::GetUrlClassification(
+    dom::Nullable<dom::MozUrlClassification>& aRetVal, ErrorResult& aRv) const {
+  MozUrlClassification classification;
+  if (nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel()) {
+    nsCOMPtr<nsIClassifiedChannel> classified = do_QueryInterface(chan);
+    MOZ_DIAGNOSTIC_ASSERT(
+        classified,
+        "Must be an object inheriting from both nsIHttpChannel and "
+        "nsIClassifiedChannel");
+    uint32_t classificationFlags;
+    classified->GetFirstPartyClassificationFlags(&classificationFlags);
+    FillClassification(classification.mFirstParty, classificationFlags, aRv);
+    if (aRv.Failed()) {
+      return;
+    }
+    classified->GetThirdPartyClassificationFlags(&classificationFlags);
+    FillClassification(classification.mThirdParty, classificationFlags, aRv);
+  }
+  aRetVal.SetValue(std::move(classification));
+}
+
+bool ChannelWrapper::ThirdParty() const {
+  nsCOMPtr<mozIThirdPartyUtil> thirdPartyUtil =
+      components::ThirdPartyUtil::Service();
+  if (NS_WARN_IF(!thirdPartyUtil)) {
+    return true;
+  }
+
+  nsCOMPtr<nsIHttpChannel> chan = MaybeHttpChannel();
+  if (!chan) {
+    return false;
+  }
+
+  bool thirdParty = false;
+  nsresult rv = thirdPartyUtil->IsThirdPartyChannel(chan, nullptr, &thirdParty);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return true;
+  }
+
+  return thirdParty;
+}
+
+/*****************************************************************************
+ * Error handling
+ *****************************************************************************/
+
+void ChannelWrapper::GetErrorString(nsString& aRetVal) const {
+  if (nsCOMPtr<nsIChannel> chan = MaybeChannel()) {
+    nsCOMPtr<nsITransportSecurityInfo> securityInfo;
+    Unused << chan->GetSecurityInfo(getter_AddRefs(securityInfo));
+    if (securityInfo) {
+      int32_t errorCode = 0;
+      securityInfo->GetErrorCode(&errorCode);
+      if (psm::IsNSSErrorCode(errorCode)) {
+        nsCOMPtr<nsINSSErrorsService> nsserr =
+            do_GetService(NS_NSS_ERRORS_SERVICE_CONTRACTID);
+
+        nsresult rv = psm::GetXPCOMFromNSSError(errorCode);
+        if (nsserr && NS_SUCCEEDED(nsserr->GetErrorMessage(rv, aRetVal))) {
+          return;
+        }
+      }
+    }
+
+    nsresult status;
+    if (NS_SUCCEEDED(chan->GetStatus(&status)) && NS_FAILED(status)) {
+      nsAutoCString name;
+      GetErrorName(status, name);
+      AppendUTF8toUTF16(name, aRetVal);
+    } else {
+      aRetVal.SetIsVoid(true);
+    }
+  } else {
+    aRetVal.AssignLiteral("NS_ERROR_UNEXPECTED");
+  }
+}
+
+void ChannelWrapper::ErrorCheck() {
+  if (!mFiredErrorEvent) {
+    nsAutoString error;
+    GetErrorString(error);
+    if (error.Length()) {
+      mChannelEntry = nullptr;
+      mFiredErrorEvent = true;
+      ChannelWrapper_Binding::ClearCachedErrorStringValue(this);
+      FireEvent(u"error"_ns);
+    }
+  }
+}
+
+/*****************************************************************************
+ * nsIWebRequestListener
+ *****************************************************************************/
+
+NS_IMPL_ISUPPORTS(ChannelWrapper::RequestListener, nsIStreamListener,
+                  nsIMultiPartChannelListener, nsIRequestObserver,
+                  nsIThreadRetargetableStreamListener)
+
+ChannelWrapper::RequestListener::~RequestListener() {
+  NS_ReleaseOnMainThread("RequestListener::mChannelWrapper",
+                         mChannelWrapper.forget());
+}
+
+nsresult ChannelWrapper::RequestListener::Init() {
+  if (nsCOMPtr<nsITraceableChannel> chan = mChannelWrapper->QueryChannel()) {
+    return chan->SetNewListener(this, false,
+                                getter_AddRefs(mOrigStreamListener));
+  }
+  return NS_ERROR_UNEXPECTED;
+}
+
+NS_IMETHODIMP
+ChannelWrapper::RequestListener::OnStartRequest(nsIRequest* request) {
+  MOZ_ASSERT(mOrigStreamListener, "Should have mOrigStreamListener");
+
+  mChannelWrapper->mChannelEntry = nullptr;
+  mChannelWrapper->mResponseStarted = true;
+  mChannelWrapper->ErrorCheck();
+  mChannelWrapper->FireEvent(u"start"_ns);
+
+  return mOrigStreamListener->OnStartRequest(request);
+}
+
+NS_IMETHODIMP
+ChannelWrapper::RequestListener::OnStopRequest(nsIRequest* request,
+                                               nsresult aStatus) {
+  MOZ_ASSERT(mOrigStreamListener, "Should have mOrigStreamListener");
+
+  mChannelWrapper->mChannelEntry = nullptr;
+  mChannelWrapper->ErrorCheck();
+  mChannelWrapper->FireEvent(u"stop"_ns);
+
+  return mOrigStreamListener->OnStopRequest(request, aStatus);
+}
+
+NS_IMETHODIMP
+ChannelWrapper::RequestListener::OnDataAvailable(nsIRequest* request,
+                                                 nsIInputStream* inStr,
+                                                 uint64_t sourceOffset,
+                                                 uint32_t count) {
+  MOZ_ASSERT(mOrigStreamListener, "Should have mOrigStreamListener");
+  return mOrigStreamListener->OnDataAvailable(request, inStr, sourceOffset,
+                                              count);
+}
+
+NS_IMETHODIMP
+ChannelWrapper::RequestListener::OnAfterLastPart(nsresult aStatus) {
+  MOZ_ASSERT(mOrigStreamListener, "Should have mOrigStreamListener");
+  if (nsCOMPtr<nsIMultiPartChannelListener> listener =
+          do_QueryInterface(mOrigStreamListener)) {
+    return listener->OnAfterLastPart(aStatus);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ChannelWrapper::RequestListener::CheckListenerChain() {
+  MOZ_ASSERT(NS_IsMainThread(), "Should be on main thread!");
+  nsresult rv;
+  nsCOMPtr<nsIThreadRetargetableStreamListener> retargetableListener =
+      do_QueryInterface(mOrigStreamListener, &rv);
+  if (retargetableListener) {
+    return retargetableListener->CheckListenerChain();
+  }
+  return rv;
+}
+
+/*****************************************************************************
+ * Event dispatching
+ *****************************************************************************/
+
+void ChannelWrapper::FireEvent(const nsAString& aType) {
+  EventInit init;
+  init.mBubbles = false;
+  init.mCancelable = false;
+
+  RefPtr<Event> event = Event::Constructor(this, aType, init);
+  event->SetTrusted(true);
+
+  DispatchEvent(*event);
+}
+
+void ChannelWrapper::CheckEventListeners() {
+  if (!mAddedStreamListener &&
+      (HasListenersFor(nsGkAtoms::onerror) ||
+       HasListenersFor(nsGkAtoms::onstart) ||
+       HasListenersFor(nsGkAtoms::onstop) || mChannelEntry)) {
+    auto listener = MakeRefPtr<RequestListener>(this);
+    if (!NS_WARN_IF(NS_FAILED(listener->Init()))) {
+      mAddedStreamListener = true;
+    }
+  }
+}
+
+void ChannelWrapper::EventListenerAdded(nsAtom* aType) {
+  CheckEventListeners();
+}
+
+void ChannelWrapper::EventListenerRemoved(nsAtom* aType) {
+  CheckEventListeners();
+}
+
+/*****************************************************************************
+ * Glue
+ *****************************************************************************/
+
+JSObject* ChannelWrapper::WrapObject(JSContext* aCx,
+                                     JS::Handle<JSObject*> aGivenProto) {
+  return ChannelWrapper_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(ChannelWrapper)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ChannelWrapper)
+  NS_INTERFACE_MAP_ENTRY_CONCRETE(ChannelWrapper)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(ChannelWrapper,
+                                                DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mParent)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mStub)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_PTR
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ChannelWrapper,
+                                                  DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParent)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mStub)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_ADDREF_INHERITED(ChannelWrapper, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(ChannelWrapper, DOMEventTargetHelper)
+
+}  // namespace extensions
+}  // namespace mozilla
diff --git a/toolkit/components/extensions/webrequest/ChannelWrapper.h b/toolkit/components/extensions/webrequest/ChannelWrapper.h
new file mode 100644
index 0000000000..0a03aea113
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/ChannelWrapper.h
@@ -0,0 +1,358 @@
+/* -*- Mode: C++; tab-width: 2; 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_extensions_ChannelWrapper_h
+#define mozilla_extensions_ChannelWrapper_h
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/ChannelWrapperBinding.h"
+
+#include "mozilla/WebRequestService.h"
+#include "mozilla/extensions/MatchPattern.h"
+#include "mozilla/extensions/WebExtensionPolicy.h"
+
+#include "mozilla/Attributes.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WeakPtr.h"
+
+#include "mozilla/DOMEventTargetHelper.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsIChannel.h"
+#include "nsIHttpChannel.h"
+#include "nsIMultiPartChannel.h"
+#include "nsIStreamListener.h"
+#include "nsIRemoteTab.h"
+#include "nsIThreadRetargetableStreamListener.h"
+#include "nsPointerHashKeys.h"
+#include "nsInterfaceHashtable.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsWrapperCache.h"
+
+#define NS_CHANNELWRAPPER_IID                        \
+  {                                                  \
+    0xc06162d2, 0xb803, 0x43b4, {                    \
+      0xaa, 0x31, 0xcf, 0x69, 0x7f, 0x93, 0x68, 0x1c \
+    }                                                \
+  }
+
+class nsILoadContext;
+class nsITraceableChannel;
+
+namespace mozilla {
+namespace dom {
+class ContentParent;
+class Element;
+}  // namespace dom
+namespace extensions {
+
+namespace detail {
+
+// We need to store our wrapped channel as a weak reference, since channels
+// are not cycle collected, and we're going to be hanging this wrapper
+// instance off the channel in order to ensure the same channel always has
+// the same wrapper.
+//
+// But since performance matters here, and we don't want to have to
+// QueryInterface the channel every time we touch it, we store separate
+// nsIChannel and nsIHttpChannel weak references, and check that the WeakPtr
+// is alive before returning it.
+//
+// This holder class prevents us from accidentally touching the weak pointer
+// members directly from our ChannelWrapper class.
+struct ChannelHolder {
+  explicit ChannelHolder(nsIChannel* aChannel)
+      : mChannel(do_GetWeakReference(aChannel)), mWeakChannel(aChannel) {}
+
+  bool HaveChannel() const { return mChannel && mChannel->IsAlive(); }
+
+  void SetChannel(nsIChannel* aChannel) {
+    mChannel = do_GetWeakReference(aChannel);
+    mWeakChannel = aChannel;
+    mWeakHttpChannel.reset();
+  }
+
+  already_AddRefed<nsIChannel> MaybeChannel() const {
+    if (!HaveChannel()) {
+      mWeakChannel = nullptr;
+    }
+    return do_AddRef(mWeakChannel);
+  }
+
+  already_AddRefed<nsIHttpChannel> MaybeHttpChannel() const {
+    if (mWeakHttpChannel.isNothing()) {
+      nsCOMPtr<nsIHttpChannel> chan = QueryChannel();
+      mWeakHttpChannel.emplace(chan.get());
+    }
+
+    if (!HaveChannel()) {
+      mWeakHttpChannel.ref() = nullptr;
+    }
+    return do_AddRef(mWeakHttpChannel.value());
+  }
+
+  const nsQueryReferent QueryChannel() const {
+    return do_QueryReferent(mChannel);
+  }
+
+ private:
+  nsWeakPtr mChannel;
+
+  mutable nsIChannel* MOZ_NON_OWNING_REF mWeakChannel;
+  mutable Maybe<nsIHttpChannel*> MOZ_NON_OWNING_REF mWeakHttpChannel;
+};
+}  // namespace detail
+
+class WebRequestChannelEntry;
+
+class ChannelWrapper final : public DOMEventTargetHelper,
+                             public SupportsWeakPtr,
+                             public LinkedListElement<ChannelWrapper>,
+                             private detail::ChannelHolder {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(ChannelWrapper, DOMEventTargetHelper)
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_CHANNELWRAPPER_IID)
+
+  void Die();
+
+  static already_AddRefed<extensions::ChannelWrapper> Get(
+      const dom::GlobalObject& global, nsIChannel* channel);
+  static already_AddRefed<extensions::ChannelWrapper> GetRegisteredChannel(
+      const dom::GlobalObject& global, uint64_t aChannelId,
+      const WebExtensionPolicy& aAddon, nsIRemoteTab* aBrowserParent);
+
+  uint64_t Id() const { return mId; }
+
+  already_AddRefed<nsIChannel> GetChannel() const { return MaybeChannel(); }
+
+  void SetChannel(nsIChannel* aChannel);
+
+  void Cancel(uint32_t result, uint32_t reason, ErrorResult& aRv);
+
+  void RedirectTo(nsIURI* uri, ErrorResult& aRv);
+  void UpgradeToSecure(ErrorResult& aRv);
+
+  bool Suspended() const { return mSuspended; }
+  void Suspend(const nsCString& aProfileMarkerText, ErrorResult& aRv);
+  void Resume(ErrorResult& aRv);
+
+  void GetContentType(nsCString& aContentType) const;
+  void SetContentType(const nsACString& aContentType);
+
+  void RegisterTraceableChannel(const WebExtensionPolicy& aAddon,
+                                nsIRemoteTab* aBrowserParent);
+
+  already_AddRefed<nsITraceableChannel> GetTraceableChannel(
+      nsAtom* aAddonId, dom::ContentParent* aContentParent) const;
+
+  void GetMethod(nsCString& aRetVal) const;
+
+  dom::MozContentPolicyType Type() const;
+
+  uint32_t StatusCode() const;
+
+  uint64_t ResponseSize() const;
+
+  uint64_t RequestSize() const;
+
+  void GetStatusLine(nsCString& aRetVal) const;
+
+  void GetErrorString(nsString& aRetVal) const;
+
+  void ErrorCheck();
+
+  IMPL_EVENT_HANDLER(error);
+  IMPL_EVENT_HANDLER(start);
+  IMPL_EVENT_HANDLER(stop);
+
+  already_AddRefed<nsIURI> FinalURI() const;
+
+  void GetFinalURL(nsString& aRetVal) const;
+
+  bool Matches(const dom::MozRequestFilter& aFilter,
+               const WebExtensionPolicy* aExtension,
+               const dom::MozRequestMatchOptions& aOptions) const;
+
+  already_AddRefed<nsILoadInfo> GetLoadInfo() const {
+    nsCOMPtr<nsIChannel> chan = MaybeChannel();
+    if (chan) {
+      return chan->LoadInfo();
+    }
+    return nullptr;
+  }
+
+  int64_t FrameId() const;
+
+  int64_t ParentFrameId() const;
+
+  void GetFrameAncestors(
+      dom::Nullable<nsTArray<dom::MozFrameAncestorInfo>>& aFrameAncestors,
+      ErrorResult& aRv) const;
+
+  bool IsServiceWorkerScript() const;
+
+  static bool IsServiceWorkerScript(const nsCOMPtr<nsIChannel>& aChannel);
+
+  bool IsSystemLoad() const;
+
+  void GetOriginURL(nsCString& aRetVal) const;
+
+  void GetDocumentURL(nsCString& aRetVal) const;
+
+  already_AddRefed<nsIURI> GetOriginURI() const;
+
+  already_AddRefed<nsIURI> GetDocumentURI() const;
+
+  already_AddRefed<nsILoadContext> GetLoadContext() const;
+
+  already_AddRefed<dom::Element> GetBrowserElement() const;
+
+  bool CanModify() const;
+  bool GetCanModify(ErrorResult& aRv) const { return CanModify(); }
+
+  void GetProxyInfo(dom::Nullable<dom::MozProxyInfo>& aRetVal,
+                    ErrorResult& aRv) const;
+
+  void GetRemoteAddress(nsCString& aRetVal) const;
+
+  void GetRequestHeaders(nsTArray<dom::MozHTTPHeader>& aRetVal,
+                         ErrorResult& aRv) const;
+  void GetRequestHeader(const nsCString& aHeader, nsCString& aResult,
+                        ErrorResult& aRv) const;
+
+  void GetResponseHeaders(nsTArray<dom::MozHTTPHeader>& aRetVal,
+                          ErrorResult& aRv) const;
+
+  void SetRequestHeader(const nsCString& header, const nsCString& value,
+                        bool merge, ErrorResult& aRv);
+
+  void SetResponseHeader(const nsCString& header, const nsCString& value,
+                         bool merge, ErrorResult& aRv);
+
+  void GetUrlClassification(dom::Nullable<dom::MozUrlClassification>& aRetVal,
+                            ErrorResult& aRv) const;
+
+  bool ThirdParty() const;
+
+  using EventTarget::EventListenerAdded;
+  using EventTarget::EventListenerRemoved;
+  virtual void EventListenerAdded(nsAtom* aType) override;
+  virtual void EventListenerRemoved(nsAtom* aType) override;
+
+  nsISupports* GetParentObject() const { return mParent; }
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+ protected:
+  ~ChannelWrapper();
+
+ private:
+  ChannelWrapper(nsISupports* aParent, nsIChannel* aChannel);
+
+  void ClearCachedAttributes();
+
+  bool CheckAlive(ErrorResult& aRv) const {
+    if (!HaveChannel()) {
+      aRv.Throw(NS_ERROR_UNEXPECTED);
+      return false;
+    }
+    return true;
+  }
+
+  void FireEvent(const nsAString& aType);
+
+  const URLInfo& FinalURLInfo() const;
+  const URLInfo* DocumentURLInfo() const;
+
+  uint64_t BrowsingContextId(nsILoadInfo* aLoadInfo) const;
+
+  nsresult GetFrameAncestors(
+      nsILoadInfo* aLoadInfo,
+      nsTArray<dom::MozFrameAncestorInfo>& aFrameAncestors) const;
+
+  static uint64_t GetNextId() {
+    static uint64_t sNextId = 1;
+    return ++sNextId;
+  }
+
+  void CheckEventListeners();
+
+  class ChannelWrapperStub final : public nsISupports {
+   public:
+    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+    NS_DECL_CYCLE_COLLECTION_CLASS(ChannelWrapperStub)
+
+    explicit ChannelWrapperStub(ChannelWrapper* aChannelWrapper)
+        : mChannelWrapper(aChannelWrapper) {}
+
+   private:
+    friend class ChannelWrapper;
+
+    RefPtr<ChannelWrapper> mChannelWrapper;
+
+   protected:
+    ~ChannelWrapperStub() = default;
+  };
+
+  RefPtr<ChannelWrapperStub> mStub;
+
+  mutable Maybe<URLInfo> mFinalURLInfo;
+  mutable Maybe<URLInfo> mDocumentURLInfo;
+
+  UniquePtr<WebRequestChannelEntry> mChannelEntry;
+
+  // The overridden Content-Type header value.
+  nsCString mContentTypeHdr = VoidCString();
+
+  const uint64_t mId = GetNextId();
+  nsCOMPtr<nsISupports> mParent;
+
+  bool mAddedStreamListener = false;
+  bool mFiredErrorEvent = false;
+  bool mSuspended = false;
+  bool mResponseStarted = false;
+
+  nsInterfaceHashtable<nsPtrHashKey<const nsAtom>, nsIRemoteTab> mAddonEntries;
+
+  // The text for the "Extension Suspend" marker, set from the Suspend method
+  // when called for the first time and then cleared on the Resume method.
+  nsCString mSuspendedMarkerText = VoidCString();
+
+  class RequestListener final : public nsIStreamListener,
+                                public nsIMultiPartChannelListener,
+                                public nsIThreadRetargetableStreamListener {
+   public:
+    NS_DECL_THREADSAFE_ISUPPORTS
+    NS_DECL_NSIREQUESTOBSERVER
+    NS_DECL_NSISTREAMLISTENER
+    NS_DECL_NSIMULTIPARTCHANNELLISTENER
+    NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER
+
+    explicit RequestListener(ChannelWrapper* aWrapper)
+        : mChannelWrapper(aWrapper) {}
+
+    nsresult Init();
+
+   protected:
+    virtual ~RequestListener();
+
+   private:
+    RefPtr<ChannelWrapper> mChannelWrapper;
+    nsCOMPtr<nsIStreamListener> mOrigStreamListener;
+  };
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(ChannelWrapper, NS_CHANNELWRAPPER_IID)
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // mozilla_extensions_ChannelWrapper_h
diff --git a/toolkit/components/extensions/webrequest/PStreamFilter.ipdl b/toolkit/components/extensions/webrequest/PStreamFilter.ipdl
new file mode 100644
index 0000000000..80e03cc8cf
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/PStreamFilter.ipdl
@@ -0,0 +1,38 @@
+/* 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 protocol PBackground;
+
+namespace mozilla {
+namespace extensions {
+
+async protocol PStreamFilter
+{
+parent:
+  async Write(uint8_t[] data);
+
+  async FlushedData();
+
+  async Suspend();
+  async Resume();
+  async Close();
+  async Disconnect();
+  async Destroy();
+
+child:
+  async Resumed();
+  async Suspended();
+  async Closed();
+  async Error(nsCString error);
+
+  async FlushData();
+
+  async StartRequest();
+  async Data(uint8_t[] data);
+  async StopRequest(nsresult aStatus);
+};
+
+} // namespace extensions
+} // namespace mozilla
+
diff --git a/toolkit/components/extensions/webrequest/SecurityInfo.sys.mjs b/toolkit/components/extensions/webrequest/SecurityInfo.sys.mjs
new file mode 100644
index 0000000000..a886cf4bcd
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/SecurityInfo.sys.mjs
@@ -0,0 +1,346 @@
+/* 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 { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const wpl = Ci.nsIWebProgressListener;
+const lazy = {};
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "NSSErrorsService",
+  "@mozilla.org/nss_errors_service;1",
+  "nsINSSErrorsService"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "pkps",
+  "@mozilla.org/security/publickeypinningservice;1",
+  "nsIPublicKeyPinningService"
+);
+
+// NOTE: SecurityInfo is largely reworked from the devtools NetworkHelper with changes
+// to better support the WebRequest api.  The objects returned are formatted specifically
+// to pass through as part of a response to webRequest listeners.
+
+export const SecurityInfo = {
+  /**
+   * Extracts security information from nsIChannel.securityInfo.
+   *
+   * @param {nsIChannel} channel
+   *        If null channel is assumed to be insecure.
+   * @param {object} options
+   *
+   * @returns {object}
+   *         Returns an object containing following members:
+   *          - state: The security of the connection used to fetch this
+   *                   request. Has one of following string values:
+   *                    - "insecure": the connection was not secure (only http)
+   *                    - "weak": the connection has minor security issues
+   *                    - "broken": secure connection failed (e.g. expired cert)
+   *                    - "secure": the connection was properly secured.
+   *          If state == broken:
+   *            - errorMessage: full error message from
+   *                            nsITransportSecurityInfo.
+   *          If state == secure:
+   *            - protocolVersion: one of TLSv1, TLSv1.1, TLSv1.2, TLSv1.3.
+   *            - cipherSuite: the cipher suite used in this connection.
+   *            - cert: information about certificate used in this connection.
+   *                    See parseCertificateInfo for the contents.
+   *            - hsts: true if host uses Strict Transport Security,
+   *                    false otherwise
+   *            - hpkp: true if host uses Public Key Pinning, false otherwise
+   *          If state == weak: Same as state == secure and
+   *            - weaknessReasons: list of reasons that cause the request to be
+   *                               considered weak. See getReasonsForWeakness.
+   */
+  getSecurityInfo(channel, options = {}) {
+    const info = {
+      state: "insecure",
+    };
+
+    /**
+     * Different scenarios to consider here and how they are handled:
+     * - request is HTTP, the connection is not secure
+     *   => securityInfo is null
+     *      => state === "insecure"
+     *
+     * - request is HTTPS, the connection is secure
+     *   => .securityState has STATE_IS_SECURE flag
+     *      => state === "secure"
+     *
+     * - request is HTTPS, the connection has security issues
+     *   => .securityState has STATE_IS_INSECURE flag
+     *   => .errorCode is an NSS error code.
+     *      => state === "broken"
+     *
+     * - request is HTTPS, the connection was terminated before the security
+     *   could be validated
+     *   => .securityState has STATE_IS_INSECURE flag
+     *   => .errorCode is NOT an NSS error code.
+     *   => .errorMessage is not available.
+     *      => state === "insecure"
+     *
+     * - request is HTTPS but it uses a weak cipher or old protocol, see
+     *   https://hg.mozilla.org/mozilla-central/annotate/def6ed9d1c1a/
+     *   security/manager/ssl/nsNSSCallbacks.cpp#l1233
+     * - request is mixed content (which makes no sense whatsoever)
+     *   => .securityState has STATE_IS_BROKEN flag
+     *   => .errorCode is NOT an NSS error code
+     *   => .errorMessage is not available
+     *      => state === "weak"
+     */
+
+    let securityInfo = channel.securityInfo;
+
+    if (!securityInfo) {
+      return info;
+    }
+
+    if (lazy.NSSErrorsService.isNSSErrorCode(securityInfo.errorCode)) {
+      // The connection failed.
+      info.state = "broken";
+      info.errorMessage = securityInfo.errorMessage;
+      if (options.certificateChain && securityInfo.failedCertChain) {
+        info.certificates = this.getCertificateChain(
+          securityInfo.failedCertChain,
+          options
+        );
+      }
+      return info;
+    }
+
+    const state = securityInfo.securityState;
+
+    let uri = channel.URI;
+    if (uri && !uri.schemeIs("https") && !uri.schemeIs("wss")) {
+      // it is not enough to look at the transport security info -
+      // schemes other than https and wss are subject to
+      // downgrade/etc at the scheme level and should always be
+      // considered insecure.
+      // Leave info.state = "insecure";
+    } else if (state & wpl.STATE_IS_SECURE) {
+      // The connection is secure if the scheme is sufficient
+      info.state = "secure";
+    } else if (state & wpl.STATE_IS_BROKEN) {
+      // The connection is not secure, there was no error but there's some
+      // minor security issues.
+      info.state = "weak";
+      info.weaknessReasons = this.getReasonsForWeakness(state);
+    } else if (state & wpl.STATE_IS_INSECURE) {
+      // This was most likely an https request that was aborted before
+      // validation. Return info as info.state = insecure.
+      return info;
+    } else {
+      // No known STATE_IS_* flags.
+      return info;
+    }
+
+    // Cipher suite.
+    info.cipherSuite = securityInfo.cipherName;
+
+    // Length (in bits) of the secret key
+    info.secretKeyLength = securityInfo.secretKeyLength;
+
+    // Key exchange group name.
+    if (securityInfo.keaGroupName !== "none") {
+      info.keaGroupName = securityInfo.keaGroupName;
+    }
+
+    // Certificate signature scheme.
+    if (securityInfo.signatureSchemeName !== "none") {
+      info.signatureSchemeName = securityInfo.signatureSchemeName;
+    }
+
+    if (
+      securityInfo.overridableErrorCategory ==
+      Ci.nsITransportSecurityInfo.ERROR_TRUST
+    ) {
+      info.overridableErrorCategory = "trust_error";
+      info.isUntrusted = true;
+    } else if (
+      securityInfo.overridableErrorCategory ==
+      Ci.nsITransportSecurityInfo.ERROR_DOMAIN
+    ) {
+      info.overridableErrorCategory = "domain_mismatch";
+      info.isDomainMismatch = true;
+    } else if (
+      securityInfo.overridableErrorCategory ==
+      Ci.nsITransportSecurityInfo.ERROR_TIME
+    ) {
+      info.overridableErrorCategory = "expired_or_not_yet_valid";
+      info.isNotValidAtThisTime = true;
+    }
+    info.isExtendedValidation = securityInfo.isExtendedValidation;
+
+    info.certificateTransparencyStatus = this.getTransparencyStatus(
+      securityInfo.certificateTransparencyStatus
+    );
+
+    // Protocol version.
+    info.protocolVersion = this.formatSecurityProtocol(
+      securityInfo.protocolVersion
+    );
+
+    if (options.certificateChain && securityInfo.succeededCertChain) {
+      info.certificates = this.getCertificateChain(
+        securityInfo.succeededCertChain,
+        options
+      );
+    } else {
+      info.certificates = [
+        this.parseCertificateInfo(securityInfo.serverCert, options),
+      ];
+    }
+
+    // HSTS and static pinning if available.
+    if (uri && uri.host) {
+      info.hsts = channel.loadInfo.hstsStatus;
+      info.hpkp = lazy.pkps.hostHasPins(uri);
+    } else {
+      info.hsts = false;
+      info.hpkp = false;
+    }
+
+    // These values can be unset in rare cases, e.g. when stashed connection
+    // data is deseralized from an older version of Firefox.
+    try {
+      info.usedEch = securityInfo.isAcceptedEch;
+    } catch {
+      info.usedEch = false;
+    }
+    try {
+      info.usedDelegatedCredentials = securityInfo.isDelegatedCredential;
+    } catch {
+      info.usedDelegatedCredentials = false;
+    }
+    info.usedOcsp = securityInfo.madeOCSPRequests;
+    info.usedPrivateDns = securityInfo.usedPrivateDNS;
+
+    return info;
+  },
+
+  getCertificateChain(certChain, options = {}) {
+    let certificates = [];
+    for (let cert of certChain) {
+      certificates.push(this.parseCertificateInfo(cert, options));
+    }
+    return certificates;
+  },
+
+  /**
+   * Takes an nsIX509Cert and returns an object with certificate information.
+   *
+   * @param {nsIX509Cert} cert
+   *        The certificate to extract the information from.
+   * @param {object} options
+   * @returns {object}
+   *         An object with following format:
+   *           {
+   *             subject: subjectName,
+   *             issuer: issuerName,
+   *             validity: { start, end },
+   *             fingerprint: { sha1, sha256 }
+   *           }
+   */
+  parseCertificateInfo(cert, options = {}) {
+    if (!cert) {
+      return {};
+    }
+
+    let certData = {
+      subject: cert.subjectName,
+      issuer: cert.issuerName,
+      validity: {
+        start: cert.validity.notBefore
+          ? Math.trunc(cert.validity.notBefore / 1000)
+          : 0,
+        end: cert.validity.notAfter
+          ? Math.trunc(cert.validity.notAfter / 1000)
+          : 0,
+      },
+      fingerprint: {
+        sha1: cert.sha1Fingerprint,
+        sha256: cert.sha256Fingerprint,
+      },
+      serialNumber: cert.serialNumber,
+      isBuiltInRoot: cert.isBuiltInRoot,
+      subjectPublicKeyInfoDigest: {
+        sha256: cert.sha256SubjectPublicKeyInfoDigest,
+      },
+    };
+    if (options.rawDER) {
+      certData.rawDER = cert.getRawDER();
+    }
+    return certData;
+  },
+
+  // Bug 1355903 Transparency is currently disabled using security.pki.certificate_transparency.mode
+  getTransparencyStatus(status) {
+    switch (status) {
+      case Ci.nsITransportSecurityInfo.CERTIFICATE_TRANSPARENCY_NOT_APPLICABLE:
+        return "not_applicable";
+      case Ci.nsITransportSecurityInfo
+        .CERTIFICATE_TRANSPARENCY_POLICY_COMPLIANT:
+        return "policy_compliant";
+      case Ci.nsITransportSecurityInfo
+        .CERTIFICATE_TRANSPARENCY_POLICY_NOT_ENOUGH_SCTS:
+        return "policy_not_enough_scts";
+      case Ci.nsITransportSecurityInfo
+        .CERTIFICATE_TRANSPARENCY_POLICY_NOT_DIVERSE_SCTS:
+        return "policy_not_diverse_scts";
+    }
+    return "unknown";
+  },
+
+  /**
+   * Takes protocolVersion of TransportSecurityInfo object and returns human readable
+   * description.
+   *
+   * @param {number} version
+   *        One of nsITransportSecurityInfo version constants.
+   * @returns {string}
+   *         One of TLSv1, TLSv1.1, TLSv1.2, TLSv1.3 if version
+   *         is valid, Unknown otherwise.
+   */
+  formatSecurityProtocol(version) {
+    switch (version) {
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1:
+        return "TLSv1";
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1_1:
+        return "TLSv1.1";
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1_2:
+        return "TLSv1.2";
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1_3:
+        return "TLSv1.3";
+    }
+    return "unknown";
+  },
+
+  /**
+   * Takes the securityState bitfield and returns reasons for weak connection
+   * as an array of strings.
+   *
+   * @param {number} state
+   *        nsITransportSecurityInfo.securityState.
+   *
+   * @returns {Array<string>}
+   *         List of weakness reasons. A subset of { cipher } where
+   *         cipher: The cipher suite is consireded to be weak (RC4).
+   */
+  getReasonsForWeakness(state) {
+    // If there's non-fatal security issues the request has STATE_IS_BROKEN
+    // flag set. See https://hg.mozilla.org/mozilla-central/file/44344099d119
+    // /security/manager/ssl/nsNSSCallbacks.cpp#l1233
+    let reasons = [];
+
+    if (state & wpl.STATE_IS_BROKEN) {
+      if (state & wpl.STATE_USES_WEAK_CRYPTO) {
+        reasons.push("cipher");
+      }
+    }
+
+    return reasons;
+  },
+};
diff --git a/toolkit/components/extensions/webrequest/StreamFilter.cpp b/toolkit/components/extensions/webrequest/StreamFilter.cpp
new file mode 100644
index 0000000000..32bfc33a30
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilter.cpp
@@ -0,0 +1,285 @@
+/* -*- 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 "StreamFilter.h"
+
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "xpcpublic.h"
+
+#include "mozilla/AbstractThread.h"
+#include "mozilla/extensions/StreamFilterChild.h"
+#include "mozilla/extensions/StreamFilterEvents.h"
+#include "mozilla/extensions/StreamFilterParent.h"
+#include "mozilla/dom/AutoEntryScript.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/RootedDictionary.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "nsContentUtils.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsLiteralString.h"
+#include "nsThreadUtils.h"
+#include "nsTArray.h"
+
+using namespace JS;
+using namespace mozilla::dom;
+
+namespace mozilla {
+namespace extensions {
+
+/*****************************************************************************
+ * Initialization
+ *****************************************************************************/
+
+StreamFilter::StreamFilter(nsIGlobalObject* aParent, uint64_t aRequestId,
+                           const nsAString& aAddonId)
+    : mParent(aParent), mChannelId(aRequestId), mAddonId(NS_Atomize(aAddonId)) {
+  MOZ_ASSERT(aParent);
+
+  Connect();
+};
+
+StreamFilter::~StreamFilter() { ForgetActor(); }
+
+void StreamFilter::ForgetActor() {
+  if (mActor) {
+    mActor->Cleanup();
+    mActor->SetStreamFilter(nullptr);
+  }
+}
+
+/* static */
+already_AddRefed<StreamFilter> StreamFilter::Create(GlobalObject& aGlobal,
+                                                    uint64_t aRequestId,
+                                                    const nsAString& aAddonId) {
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  MOZ_ASSERT(global);
+
+  RefPtr<StreamFilter> filter = new StreamFilter(global, aRequestId, aAddonId);
+  return filter.forget();
+}
+
+/*****************************************************************************
+ * Actor allocation
+ *****************************************************************************/
+
+void StreamFilter::Connect() {
+  MOZ_ASSERT(!mActor);
+
+  mActor = new StreamFilterChild();
+  mActor->SetStreamFilter(this);
+
+  nsAutoString addonId;
+  mAddonId->ToString(addonId);
+
+  ContentChild* cc = ContentChild::GetSingleton();
+  RefPtr<StreamFilter> self(this);
+  if (cc) {
+    cc->SendInitStreamFilter(mChannelId, addonId)
+        ->Then(
+            GetCurrentSerialEventTarget(), __func__,
+            [self](mozilla::ipc::Endpoint<PStreamFilterChild>&& aEndpoint) {
+              self->FinishConnect(std::move(aEndpoint));
+            },
+            [self](mozilla::ipc::ResponseRejectReason&& aReason) {
+              self->mActor->RecvInitialized(false);
+            });
+  } else {
+    StreamFilterParent::Create(nullptr, mChannelId, addonId)
+        ->Then(
+            GetCurrentSerialEventTarget(), __func__,
+            [self](mozilla::ipc::Endpoint<PStreamFilterChild>&& aEndpoint) {
+              self->FinishConnect(std::move(aEndpoint));
+            },
+            [self](bool aDummy) { self->mActor->RecvInitialized(false); });
+  }
+}
+
+void StreamFilter::FinishConnect(
+    mozilla::ipc::Endpoint<PStreamFilterChild>&& aEndpoint) {
+  if (aEndpoint.IsValid()) {
+    MOZ_RELEASE_ASSERT(aEndpoint.Bind(mActor));
+    mActor->RecvInitialized(true);
+  } else {
+    mActor->RecvInitialized(false);
+  }
+}
+
+bool StreamFilter::CheckAlive() {
+  // Check whether the global that owns this StreamFitler is still scriptable
+  // and, if not, disconnect the actor so that it can be cleaned up.
+  JSObject* wrapper = GetWrapperPreserveColor();
+  if (!wrapper || !xpc::Scriptability::Get(wrapper).Allowed()) {
+    ForgetActor();
+    return false;
+  }
+  return true;
+}
+
+/*****************************************************************************
+ * Binding methods
+ *****************************************************************************/
+
+template <typename T>
+static inline bool ReadTypedArrayData(nsTArray<uint8_t>& aData, const T& aArray,
+                                      ErrorResult& aRv) {
+  aArray.ComputeState();
+  if (!aData.SetLength(aArray.Length(), fallible)) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return false;
+  }
+  memcpy(aData.Elements(), aArray.Data(), aArray.Length());
+  return true;
+}
+
+void StreamFilter::Write(const ArrayBufferOrUint8Array& aData,
+                         ErrorResult& aRv) {
+  if (!mActor) {
+    aRv.Throw(NS_ERROR_NOT_INITIALIZED);
+    return;
+  }
+
+  nsTArray<uint8_t> data;
+
+  bool ok;
+  if (aData.IsArrayBuffer()) {
+    ok = ReadTypedArrayData(data, aData.GetAsArrayBuffer(), aRv);
+  } else if (aData.IsUint8Array()) {
+    ok = ReadTypedArrayData(data, aData.GetAsUint8Array(), aRv);
+  } else {
+    MOZ_ASSERT_UNREACHABLE("Argument should be ArrayBuffer or Uint8Array");
+    return;
+  }
+
+  if (ok) {
+    mActor->Write(std::move(data), aRv);
+  }
+}
+
+StreamFilterStatus StreamFilter::Status() const {
+  if (!mActor) {
+    return StreamFilterStatus::Uninitialized;
+  }
+  return mActor->Status();
+}
+
+void StreamFilter::Suspend(ErrorResult& aRv) {
+  if (mActor) {
+    mActor->Suspend(aRv);
+  } else {
+    aRv.Throw(NS_ERROR_NOT_INITIALIZED);
+  }
+}
+
+void StreamFilter::Resume(ErrorResult& aRv) {
+  if (mActor) {
+    mActor->Resume(aRv);
+  } else {
+    aRv.Throw(NS_ERROR_NOT_INITIALIZED);
+  }
+}
+
+void StreamFilter::Disconnect(ErrorResult& aRv) {
+  if (mActor) {
+    mActor->Disconnect(aRv);
+  } else {
+    aRv.Throw(NS_ERROR_NOT_INITIALIZED);
+  }
+}
+
+void StreamFilter::Close(ErrorResult& aRv) {
+  if (mActor) {
+    mActor->Close(aRv);
+  } else {
+    aRv.Throw(NS_ERROR_NOT_INITIALIZED);
+  }
+}
+
+/*****************************************************************************
+ * Event emitters
+ *****************************************************************************/
+
+void StreamFilter::FireEvent(const nsAString& aType) {
+  EventInit init;
+  init.mBubbles = false;
+  init.mCancelable = false;
+
+  RefPtr<Event> event = Event::Constructor(this, aType, init);
+  event->SetTrusted(true);
+
+  DispatchEvent(*event);
+}
+
+void StreamFilter::FireDataEvent(const nsTArray<uint8_t>& aData) {
+  AutoEntryScript aes(mParent, "StreamFilter data event");
+  JSContext* cx = aes.cx();
+
+  RootedDictionary<StreamFilterDataEventInit> init(cx);
+  init.mBubbles = false;
+  init.mCancelable = false;
+
+  auto buffer = ArrayBuffer::Create(cx, aData.Length(), aData.Elements());
+  if (!buffer) {
+    // TODO: There is no way to recover from this. This chunk of data is lost.
+    FireErrorEvent(u"Out of memory"_ns);
+    return;
+  }
+
+  init.mData.Init(buffer);
+
+  RefPtr<StreamFilterDataEvent> event =
+      StreamFilterDataEvent::Constructor(this, u"data"_ns, init);
+  event->SetTrusted(true);
+
+  DispatchEvent(*event);
+}
+
+void StreamFilter::FireErrorEvent(const nsAString& aError) {
+  MOZ_ASSERT(mError.IsEmpty());
+
+  mError = aError;
+  FireEvent(u"error"_ns);
+}
+
+/*****************************************************************************
+ * Glue
+ *****************************************************************************/
+
+/* static */
+bool StreamFilter::IsAllowedInContext(JSContext* aCx, JSObject* /* unused */) {
+  return nsContentUtils::CallerHasPermission(aCx,
+                                             nsGkAtoms::webRequestBlocking);
+}
+
+JSObject* StreamFilter::WrapObject(JSContext* aCx,
+                                   JS::Handle<JSObject*> aGivenProto) {
+  return StreamFilter_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(StreamFilter)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(StreamFilter)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(StreamFilter,
+                                                DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mParent)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(StreamFilter,
+                                                  DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParent)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(StreamFilter,
+                                               DOMEventTargetHelper)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_ADDREF_INHERITED(StreamFilter, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(StreamFilter, DOMEventTargetHelper)
+
+}  // namespace extensions
+}  // namespace mozilla
diff --git a/toolkit/components/extensions/webrequest/StreamFilter.h b/toolkit/components/extensions/webrequest/StreamFilter.h
new file mode 100644
index 0000000000..e5df536167
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilter.h
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 2; 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_extensions_StreamFilter_h
+#define mozilla_extensions_StreamFilter_h
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/StreamFilterBinding.h"
+
+#include "mozilla/DOMEventTargetHelper.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsAtom.h"
+
+namespace mozilla {
+
+namespace ipc {
+template <class T>
+class Endpoint;
+}
+
+namespace extensions {
+
+class PStreamFilterChild;
+class StreamFilterChild;
+
+class StreamFilter : public DOMEventTargetHelper {
+  friend class StreamFilterChild;
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(StreamFilter,
+                                                         DOMEventTargetHelper)
+
+  static already_AddRefed<StreamFilter> Create(dom::GlobalObject& global,
+                                               uint64_t aRequestId,
+                                               const nsAString& aAddonId);
+
+  explicit StreamFilter(nsIGlobalObject* aParent, uint64_t aRequestId,
+                        const nsAString& aAddonId);
+
+  IMPL_EVENT_HANDLER(start);
+  IMPL_EVENT_HANDLER(stop);
+  IMPL_EVENT_HANDLER(data);
+  IMPL_EVENT_HANDLER(error);
+
+  void Write(const dom::ArrayBufferOrUint8Array& aData, ErrorResult& aRv);
+
+  void GetError(nsAString& aError) { aError = mError; }
+
+  dom::StreamFilterStatus Status() const;
+  void Suspend(ErrorResult& aRv);
+  void Resume(ErrorResult& aRv);
+  void Disconnect(ErrorResult& aRv);
+  void Close(ErrorResult& aRv);
+
+  nsISupports* GetParentObject() const { return mParent; }
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  static bool IsAllowedInContext(JSContext* aCx, JSObject* aObj);
+
+ protected:
+  virtual ~StreamFilter();
+
+  void FireEvent(const nsAString& aType);
+
+  void FireDataEvent(const nsTArray<uint8_t>& aData);
+
+  void FireErrorEvent(const nsAString& aError);
+
+  bool CheckAlive();
+
+ private:
+  void Connect();
+
+  void FinishConnect(mozilla::ipc::Endpoint<PStreamFilterChild>&& aEndpoint);
+
+  void ForgetActor();
+
+  nsCOMPtr<nsIGlobalObject> mParent;
+  RefPtr<StreamFilterChild> mActor;
+
+  nsString mError;
+
+  const uint64_t mChannelId;
+  const RefPtr<nsAtom> mAddonId;
+};
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // mozilla_extensions_StreamFilter_h
diff --git a/toolkit/components/extensions/webrequest/StreamFilterBase.h b/toolkit/components/extensions/webrequest/StreamFilterBase.h
new file mode 100644
index 0000000000..4f413835ef
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterBase.h
@@ -0,0 +1,38 @@
+/* -*- 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_extensions_StreamFilterBase_h
+#define mozilla_extensions_StreamFilterBase_h
+
+#include "mozilla/LinkedList.h"
+#include "nsTArray.h"
+
+namespace mozilla {
+namespace extensions {
+
+class StreamFilterBase {
+ public:
+  typedef nsTArray<uint8_t> Data;
+
+ protected:
+  class BufferedData : public LinkedListElement<BufferedData> {
+   public:
+    explicit BufferedData(Data&& aData) : mData(std::move(aData)) {}
+
+    Data mData;
+  };
+
+  LinkedList<BufferedData> mBufferedData;
+
+  inline void BufferData(Data&& aData) {
+    mBufferedData.insertBack(new BufferedData(std::move(aData)));
+  };
+};
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // mozilla_extensions_StreamFilterBase_h
diff --git a/toolkit/components/extensions/webrequest/StreamFilterChild.cpp b/toolkit/components/extensions/webrequest/StreamFilterChild.cpp
new file mode 100644
index 0000000000..955460f834
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterChild.cpp
@@ -0,0 +1,516 @@
+/* -*- 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 "StreamFilterChild.h"
+#include "StreamFilter.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+namespace extensions {
+
+using mozilla::dom::StreamFilterStatus;
+using mozilla::ipc::IPCResult;
+
+/*****************************************************************************
+ * Initialization and cleanup
+ *****************************************************************************/
+
+void StreamFilterChild::Cleanup() {
+  switch (mState) {
+    case State::Closing:
+    case State::Closed:
+    case State::Error:
+    case State::Disconnecting:
+    case State::Disconnected:
+      break;
+
+    default:
+      ErrorResult rv;
+      Disconnect(rv);
+      break;
+  }
+}
+
+/*****************************************************************************
+ * State change methods
+ *****************************************************************************/
+
+void StreamFilterChild::Suspend(ErrorResult& aRv) {
+  switch (mState) {
+    case State::TransferringData:
+      mState = State::Suspending;
+      mNextState = State::Suspended;
+
+      SendSuspend();
+      break;
+
+    case State::Suspending:
+      switch (mNextState) {
+        case State::Suspended:
+        case State::Resuming:
+          mNextState = State::Suspended;
+          break;
+
+        default:
+          aRv.Throw(NS_ERROR_FAILURE);
+          return;
+      }
+      break;
+
+    case State::Resuming:
+      switch (mNextState) {
+        case State::TransferringData:
+        case State::Suspending:
+          mNextState = State::Suspending;
+          break;
+
+        default:
+          aRv.Throw(NS_ERROR_FAILURE);
+          return;
+      }
+      break;
+
+    case State::Suspended:
+      break;
+
+    default:
+      aRv.Throw(NS_ERROR_FAILURE);
+      break;
+  }
+}
+
+void StreamFilterChild::Resume(ErrorResult& aRv) {
+  switch (mState) {
+    case State::Suspended:
+      mState = State::Resuming;
+      mNextState = State::TransferringData;
+
+      SendResume();
+      break;
+
+    case State::Suspending:
+      switch (mNextState) {
+        case State::Suspended:
+        case State::Resuming:
+          mNextState = State::Resuming;
+          break;
+
+        default:
+          aRv.Throw(NS_ERROR_FAILURE);
+          return;
+      }
+      break;
+
+    case State::Resuming:
+    case State::TransferringData:
+      break;
+
+    default:
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+  }
+
+  FlushBufferedData();
+}
+
+void StreamFilterChild::Disconnect(ErrorResult& aRv) {
+  switch (mState) {
+    case State::Suspended:
+    case State::TransferringData:
+    case State::FinishedTransferringData:
+      mState = State::Disconnecting;
+      mNextState = State::Disconnected;
+
+      WriteBufferedData();
+      SendDisconnect();
+      break;
+
+    case State::Suspending:
+    case State::Resuming:
+      switch (mNextState) {
+        case State::Suspended:
+        case State::Resuming:
+        case State::Disconnecting:
+          mNextState = State::Disconnecting;
+          break;
+
+        default:
+          aRv.Throw(NS_ERROR_FAILURE);
+          return;
+      }
+      break;
+
+    case State::Disconnecting:
+    case State::Disconnected:
+      break;
+
+    default:
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+  }
+}
+
+void StreamFilterChild::Close(ErrorResult& aRv) {
+  switch (mState) {
+    case State::Suspended:
+    case State::TransferringData:
+    case State::FinishedTransferringData:
+      mState = State::Closing;
+      mNextState = State::Closed;
+
+      SendClose();
+      break;
+
+    case State::Suspending:
+    case State::Resuming:
+      mNextState = State::Closing;
+      break;
+
+    case State::Closing:
+      MOZ_DIAGNOSTIC_ASSERT(mNextState == State::Closed);
+      break;
+
+    case State::Closed:
+      break;
+
+    default:
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+  }
+
+  mBufferedData.clear();
+}
+
+/*****************************************************************************
+ * Internal state management
+ *****************************************************************************/
+
+void StreamFilterChild::SetNextState() {
+  mState = mNextState;
+
+  switch (mNextState) {
+    case State::Suspending:
+      mNextState = State::Suspended;
+      SendSuspend();
+      break;
+
+    case State::Resuming:
+      mNextState = State::TransferringData;
+      SendResume();
+      break;
+
+    case State::Closing:
+      mNextState = State::Closed;
+      SendClose();
+      break;
+
+    case State::Disconnecting:
+      mNextState = State::Disconnected;
+      SendDisconnect();
+      break;
+
+    case State::FinishedTransferringData:
+      if (mStreamFilter) {
+        mStreamFilter->FireEvent(u"stop"_ns);
+        // We don't need access to the stream filter after this point, so break
+        // our reference cycle, so that it can be collected if we're the last
+        // reference.
+        mStreamFilter = nullptr;
+      }
+      break;
+
+    case State::TransferringData:
+      FlushBufferedData();
+      break;
+
+    case State::Closed:
+    case State::Disconnected:
+    case State::Error:
+      mStreamFilter = nullptr;
+      break;
+
+    default:
+      break;
+  }
+}
+
+void StreamFilterChild::MaybeStopRequest() {
+  if (!mReceivedOnStop || !mBufferedData.isEmpty()) {
+    return;
+  }
+
+  if (mStreamFilter) {
+    Unused << mStreamFilter->CheckAlive();
+  }
+
+  switch (mState) {
+    case State::Suspending:
+    case State::Resuming:
+      mNextState = State::FinishedTransferringData;
+      return;
+
+    case State::Disconnecting:
+    case State::Closing:
+    case State::Closed:
+      break;
+
+    default:
+      mState = State::FinishedTransferringData;
+      if (mStreamFilter) {
+        mStreamFilter->FireEvent(u"stop"_ns);
+        // We don't need access to the stream filter after this point, so break
+        // our reference cycle, so that it can be collected if we're the last
+        // reference.
+        mStreamFilter = nullptr;
+      }
+      break;
+  }
+}
+
+/*****************************************************************************
+ * State change acknowledgment callbacks
+ *****************************************************************************/
+
+void StreamFilterChild::RecvInitialized(bool aSuccess) {
+  MOZ_ASSERT(mState == State::Uninitialized);
+
+  if (aSuccess) {
+    mState = State::Initialized;
+  } else {
+    mState = State::Error;
+    if (mStreamFilter) {
+      mStreamFilter->FireErrorEvent(u"Invalid request ID"_ns);
+      mStreamFilter = nullptr;
+    }
+  }
+}
+
+IPCResult StreamFilterChild::RecvError(const nsCString& aError) {
+  mState = State::Error;
+  if (mStreamFilter) {
+    mStreamFilter->FireErrorEvent(NS_ConvertUTF8toUTF16(aError));
+    mStreamFilter = nullptr;
+  }
+  SendDestroy();
+  return IPC_OK();
+}
+
+IPCResult StreamFilterChild::RecvClosed() {
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Closing);
+
+  SetNextState();
+  return IPC_OK();
+}
+
+IPCResult StreamFilterChild::RecvSuspended() {
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Suspending);
+
+  SetNextState();
+  return IPC_OK();
+}
+
+IPCResult StreamFilterChild::RecvResumed() {
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Resuming);
+
+  SetNextState();
+  return IPC_OK();
+}
+
+IPCResult StreamFilterChild::RecvFlushData() {
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Disconnecting);
+
+  SendFlushedData();
+  SetNextState();
+  return IPC_OK();
+}
+
+/*****************************************************************************
+ * Other binding methods
+ *****************************************************************************/
+
+void StreamFilterChild::Write(Data&& aData, ErrorResult& aRv) {
+  switch (mState) {
+    case State::Suspending:
+    case State::Resuming:
+      switch (mNextState) {
+        case State::Suspended:
+        case State::TransferringData:
+          break;
+
+        default:
+          aRv.Throw(NS_ERROR_FAILURE);
+          return;
+      }
+      break;
+
+    case State::Suspended:
+    case State::TransferringData:
+    case State::FinishedTransferringData:
+      break;
+
+    default:
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+  }
+
+  SendWrite(std::move(aData));
+}
+
+StreamFilterStatus StreamFilterChild::Status() const {
+  switch (mState) {
+    case State::Uninitialized:
+    case State::Initialized:
+      return StreamFilterStatus::Uninitialized;
+
+    case State::TransferringData:
+      return StreamFilterStatus::Transferringdata;
+
+    case State::Suspended:
+      return StreamFilterStatus::Suspended;
+
+    case State::FinishedTransferringData:
+      return StreamFilterStatus::Finishedtransferringdata;
+
+    case State::Resuming:
+    case State::Suspending:
+      switch (mNextState) {
+        case State::TransferringData:
+        case State::Resuming:
+          return StreamFilterStatus::Transferringdata;
+
+        case State::Suspended:
+        case State::Suspending:
+          return StreamFilterStatus::Suspended;
+
+        case State::Closing:
+          return StreamFilterStatus::Closed;
+
+        case State::Disconnecting:
+          return StreamFilterStatus::Disconnected;
+
+        default:
+          MOZ_ASSERT_UNREACHABLE("Unexpected next state");
+          return StreamFilterStatus::Suspended;
+      }
+      break;
+
+    case State::Closing:
+    case State::Closed:
+      return StreamFilterStatus::Closed;
+
+    case State::Disconnecting:
+    case State::Disconnected:
+      return StreamFilterStatus::Disconnected;
+
+    case State::Error:
+      return StreamFilterStatus::Failed;
+  };
+
+  MOZ_ASSERT_UNREACHABLE("Not reached");
+  return StreamFilterStatus::Failed;
+}
+
+/*****************************************************************************
+ * Request state notifications
+ *****************************************************************************/
+
+IPCResult StreamFilterChild::RecvStartRequest() {
+  MOZ_ASSERT(mState == State::Initialized);
+
+  mState = State::TransferringData;
+
+  if (mStreamFilter) {
+    mStreamFilter->FireEvent(u"start"_ns);
+    Unused << mStreamFilter->CheckAlive();
+  }
+  return IPC_OK();
+}
+
+IPCResult StreamFilterChild::RecvStopRequest(const nsresult& aStatus) {
+  mReceivedOnStop = true;
+  MaybeStopRequest();
+  return IPC_OK();
+}
+
+/*****************************************************************************
+ * Incoming request data handling
+ *****************************************************************************/
+
+void StreamFilterChild::EmitData(const Data& aData) {
+  MOZ_ASSERT(CanFlushData());
+  if (mStreamFilter) {
+    mStreamFilter->FireDataEvent(aData);
+  }
+
+  MaybeStopRequest();
+}
+
+void StreamFilterChild::FlushBufferedData() {
+  while (!mBufferedData.isEmpty() && CanFlushData()) {
+    UniquePtr<BufferedData> data(mBufferedData.popFirst());
+
+    EmitData(data->mData);
+  }
+}
+
+void StreamFilterChild::WriteBufferedData() {
+  while (!mBufferedData.isEmpty()) {
+    UniquePtr<BufferedData> data(mBufferedData.popFirst());
+
+    SendWrite(data->mData);
+  }
+}
+
+IPCResult StreamFilterChild::RecvData(Data&& aData) {
+  MOZ_ASSERT(!mReceivedOnStop);
+
+  if (mStreamFilter) {
+    Unused << mStreamFilter->CheckAlive();
+  }
+
+  switch (mState) {
+    case State::TransferringData:
+    case State::Resuming:
+      EmitData(aData);
+      break;
+
+    case State::FinishedTransferringData:
+      MOZ_ASSERT_UNREACHABLE("Received data in unexpected state");
+      EmitData(aData);
+      break;
+
+    case State::Suspending:
+    case State::Suspended:
+      BufferData(std::move(aData));
+      break;
+
+    case State::Disconnecting:
+      SendWrite(std::move(aData));
+      break;
+
+    case State::Closing:
+      break;
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Received data in unexpected state");
+      return IPC_FAIL_NO_REASON(this);
+  }
+
+  return IPC_OK();
+}
+
+/*****************************************************************************
+ * Glue
+ *****************************************************************************/
+
+void StreamFilterChild::ActorDestroy(ActorDestroyReason aWhy) {
+  mStreamFilter = nullptr;
+}
+
+}  // namespace extensions
+}  // namespace mozilla
diff --git a/toolkit/components/extensions/webrequest/StreamFilterChild.h b/toolkit/components/extensions/webrequest/StreamFilterChild.h
new file mode 100644
index 0000000000..a3873c1283
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterChild.h
@@ -0,0 +1,135 @@
+/* -*- 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_extensions_StreamFilterChild_h
+#define mozilla_extensions_StreamFilterChild_h
+
+#include "StreamFilterBase.h"
+#include "mozilla/extensions/PStreamFilterChild.h"
+#include "mozilla/extensions/StreamFilter.h"
+
+#include "mozilla/LinkedList.h"
+#include "mozilla/dom/StreamFilterBinding.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace extensions {
+
+using mozilla::dom::StreamFilterStatus;
+using mozilla::ipc::IPCResult;
+
+class StreamFilter;
+
+class StreamFilterChild final : public PStreamFilterChild,
+                                public StreamFilterBase {
+  friend class StreamFilter;
+  friend class PStreamFilterChild;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(StreamFilterChild, final)
+
+  StreamFilterChild() : mState(State::Uninitialized), mReceivedOnStop(false) {}
+
+  enum class State {
+    // Uninitialized, waiting for constructor response from parent.
+    Uninitialized,
+    // Initialized, but channel has not begun transferring data.
+    Initialized,
+    // The stream's OnStartRequest event has been dispatched, and the channel is
+    // transferring data.
+    TransferringData,
+    // The channel's OnStopRequest event has been dispatched, and the channel is
+    // no longer transferring data. Data may still be written to the output
+    // stream listener.
+    FinishedTransferringData,
+    // The channel is being suspended, and we're waiting for confirmation of
+    // suspension from the parent.
+    Suspending,
+    // The channel has been suspended in the parent. Data may still be written
+    // to the output stream listener in this state.
+    Suspended,
+    // The channel is suspended. Resume has been called, and we are waiting for
+    // confirmation of resumption from the parent.
+    Resuming,
+    // The close() method has been called, and no further output may be written.
+    // We are waiting for confirmation from the parent.
+    Closing,
+    // The close() method has been called, and we have been disconnected from
+    // our parent.
+    Closed,
+    // The channel is being disconnected from the parent, and all further events
+    // and data will pass unfiltered. Data received by the child in this state
+    // will be automatically written to the output stream listener. No data may
+    // be explicitly written.
+    Disconnecting,
+    // The channel has been disconnected from the parent, and all further data
+    // and events will be transparently passed to the output stream listener
+    // without passing through the child.
+    Disconnected,
+    // An error has occurred and the child is disconnected from the parent.
+    Error,
+  };
+
+  void Suspend(ErrorResult& aRv);
+  void Resume(ErrorResult& aRv);
+  void Disconnect(ErrorResult& aRv);
+  void Close(ErrorResult& aRv);
+  void Cleanup();
+
+  void Write(Data&& aData, ErrorResult& aRv);
+
+  State GetState() const { return mState; }
+
+  StreamFilterStatus Status() const;
+
+  void RecvInitialized(bool aSuccess);
+
+ protected:
+  IPCResult RecvStartRequest();
+  IPCResult RecvData(Data&& data);
+  IPCResult RecvStopRequest(const nsresult& aStatus);
+  IPCResult RecvError(const nsCString& aError);
+
+  IPCResult RecvClosed();
+  IPCResult RecvSuspended();
+  IPCResult RecvResumed();
+  IPCResult RecvFlushData();
+
+  void SetStreamFilter(StreamFilter* aStreamFilter) {
+    mStreamFilter = aStreamFilter;
+  }
+
+ private:
+  ~StreamFilterChild() = default;
+
+  void SetNextState();
+
+  void MaybeStopRequest();
+
+  void EmitData(const Data& aData);
+
+  bool CanFlushData() {
+    return (mState == State::TransferringData || mState == State::Resuming);
+  }
+
+  void FlushBufferedData();
+  void WriteBufferedData();
+
+  virtual void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  State mState;
+  State mNextState;
+  bool mReceivedOnStop;
+
+  RefPtr<StreamFilter> mStreamFilter;
+};
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // mozilla_extensions_StreamFilterChild_h
diff --git a/toolkit/components/extensions/webrequest/StreamFilterEvents.cpp b/toolkit/components/extensions/webrequest/StreamFilterEvents.cpp
new file mode 100644
index 0000000000..02eaf80f49
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterEvents.cpp
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 2; 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/extensions/StreamFilterEvents.h"
+
+namespace mozilla {
+namespace extensions {
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(StreamFilterDataEvent)
+
+NS_IMPL_ADDREF_INHERITED(StreamFilterDataEvent, Event)
+NS_IMPL_RELEASE_INHERITED(StreamFilterDataEvent, Event)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(StreamFilterDataEvent, Event)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(StreamFilterDataEvent, Event)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mData)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(StreamFilterDataEvent, Event)
+  tmp->mData = nullptr;
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(StreamFilterDataEvent)
+NS_INTERFACE_MAP_END_INHERITING(Event)
+
+/* static */
+already_AddRefed<StreamFilterDataEvent> StreamFilterDataEvent::Constructor(
+    dom::EventTarget* aEventTarget, const nsAString& aType,
+    const dom::StreamFilterDataEventInit& aParam) {
+  RefPtr<StreamFilterDataEvent> event = new StreamFilterDataEvent(aEventTarget);
+
+  bool trusted = event->Init(aEventTarget);
+  event->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
+  event->SetTrusted(trusted);
+  event->SetComposed(aParam.mComposed);
+
+  event->SetData(aParam.mData);
+
+  return event.forget();
+}
+
+JSObject* StreamFilterDataEvent::WrapObjectInternal(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return dom::StreamFilterDataEvent_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+}  // namespace extensions
+}  // namespace mozilla
diff --git a/toolkit/components/extensions/webrequest/StreamFilterEvents.h b/toolkit/components/extensions/webrequest/StreamFilterEvents.h
new file mode 100644
index 0000000000..3c7c2e91ee
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterEvents.h
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 2; 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_extensions_StreamFilterEvents_h
+#define mozilla_extensions_StreamFilterEvents_h
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/StreamFilterDataEventBinding.h"
+#include "mozilla/extensions/StreamFilter.h"
+
+#include "js/RootingAPI.h"
+#include "js/TypeDecls.h"
+
+#include "mozilla/HoldDropJSObjects.h"
+#include "mozilla/dom/Event.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+
+namespace mozilla::extensions {
+
+class StreamFilterDataEvent : public dom::Event {
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(StreamFilterDataEvent,
+                                                         Event)
+
+  explicit StreamFilterDataEvent(dom::EventTarget* aEventTarget)
+      : Event(aEventTarget, nullptr, nullptr) {
+    mozilla::HoldJSObjects(this);
+  }
+
+  static already_AddRefed<StreamFilterDataEvent> Constructor(
+      dom::EventTarget* aEventTarget, const nsAString& aType,
+      const dom::StreamFilterDataEventInit& aParam);
+
+  static already_AddRefed<StreamFilterDataEvent> Constructor(
+      dom::GlobalObject& aGlobal, const nsAString& aType,
+      const dom::StreamFilterDataEventInit& aParam) {
+    nsCOMPtr<dom::EventTarget> target =
+        do_QueryInterface(aGlobal.GetAsSupports());
+    return Constructor(target, aType, aParam);
+  }
+
+  void GetData(JSContext* aCx, JS::MutableHandle<JSObject*> aResult) {
+    aResult.set(mData);
+  }
+
+  virtual JSObject* WrapObjectInternal(
+      JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
+
+ protected:
+  virtual ~StreamFilterDataEvent() { mozilla::DropJSObjects(this); }
+
+ private:
+  JS::Heap<JSObject*> mData;
+
+  void SetData(const dom::ArrayBuffer& aData) { mData = aData.Obj(); }
+};
+
+}  // namespace mozilla::extensions
+
+#endif  // mozilla_extensions_StreamFilterEvents_h
diff --git a/toolkit/components/extensions/webrequest/StreamFilterParent.cpp b/toolkit/components/extensions/webrequest/StreamFilterParent.cpp
new file mode 100644
index 0000000000..335115afbd
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterParent.cpp
@@ -0,0 +1,826 @@
+/* -*- 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 "StreamFilterParent.h"
+
+#include "HttpChannelChild.h"
+#include "mozilla/ExtensionPolicyService.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/net/ChannelEventQueue.h"
+#include "mozilla/StaticPrefs_extensions.h"
+#include "nsHttpChannel.h"
+#include "nsIChannel.h"
+#include "nsIInputStream.h"
+#include "nsITraceableChannel.h"
+#include "nsProxyRelease.h"
+#include "nsQueryObject.h"
+#include "nsSocketTransportService2.h"
+#include "nsStringStream.h"
+#include "mozilla/net/DocumentChannelChild.h"
+#include "nsIViewSourceChannel.h"
+
+namespace mozilla {
+namespace extensions {
+
+/*****************************************************************************
+ * Event queueing helpers
+ *****************************************************************************/
+
+using net::ChannelEvent;
+using net::ChannelEventQueue;
+
+namespace {
+
+// Define some simple ChannelEvent sub-classes that store the appropriate
+// EventTarget and delegate their Run methods to a wrapped Runnable or lambda
+// function.
+
+class ChannelEventWrapper : public ChannelEvent {
+ public:
+  ChannelEventWrapper(nsIEventTarget* aTarget) : mTarget(aTarget) {}
+
+  already_AddRefed<nsIEventTarget> GetEventTarget() override {
+    return do_AddRef(mTarget);
+  }
+
+ protected:
+  ~ChannelEventWrapper() override = default;
+
+ private:
+  nsCOMPtr<nsIEventTarget> mTarget;
+};
+
+class ChannelEventFunction final : public ChannelEventWrapper {
+ public:
+  ChannelEventFunction(nsIEventTarget* aTarget, std::function<void()>&& aFunc)
+      : ChannelEventWrapper(aTarget), mFunc(std::move(aFunc)) {}
+
+  void Run() override { mFunc(); }
+
+ protected:
+  ~ChannelEventFunction() override = default;
+
+ private:
+  std::function<void()> mFunc;
+};
+
+class ChannelEventRunnable final : public ChannelEventWrapper {
+ public:
+  ChannelEventRunnable(nsIEventTarget* aTarget,
+                       already_AddRefed<Runnable> aRunnable)
+      : ChannelEventWrapper(aTarget), mRunnable(aRunnable) {}
+
+  void Run() override {
+    nsresult rv = mRunnable->Run();
+    Unused << NS_WARN_IF(NS_FAILED(rv));
+  }
+
+ protected:
+  ~ChannelEventRunnable() override = default;
+
+ private:
+  RefPtr<Runnable> mRunnable;
+};
+
+}  // anonymous namespace
+
+/*****************************************************************************
+ * Initialization
+ *****************************************************************************/
+
+StreamFilterParent::StreamFilterParent()
+    : mMainThread(GetCurrentSerialEventTarget()),
+      mIOThread(mMainThread),
+      mQueue(new ChannelEventQueue(static_cast<nsIStreamListener*>(this))),
+      mBufferMutex("StreamFilter buffer mutex"),
+      mReceivedStop(false),
+      mSentStop(false),
+      mContext(nullptr),
+      mOffset(0),
+      mState(State::Uninitialized) {}
+
+StreamFilterParent::~StreamFilterParent() {
+  NS_ReleaseOnMainThread("StreamFilterParent::mChannel", mChannel.forget());
+  NS_ReleaseOnMainThread("StreamFilterParent::mLoadGroup", mLoadGroup.forget());
+  NS_ReleaseOnMainThread("StreamFilterParent::mOrigListener",
+                         mOrigListener.forget());
+  NS_ReleaseOnMainThread("StreamFilterParent::mContext", mContext.forget());
+  mQueue->NotifyReleasingOwner();
+}
+
+auto StreamFilterParent::Create(dom::ContentParent* aContentParent,
+                                uint64_t aChannelId, const nsAString& aAddonId)
+    -> RefPtr<ChildEndpointPromise> {
+  AssertIsMainThread();
+
+  auto& webreq = WebRequestService::GetSingleton();
+
+  RefPtr<nsAtom> addonId = NS_Atomize(aAddonId);
+  nsCOMPtr<nsITraceableChannel> channel =
+      webreq.GetTraceableChannel(aChannelId, addonId, aContentParent);
+
+  RefPtr<mozilla::net::nsHttpChannel> chan = do_QueryObject(channel);
+  if (!chan) {
+    return ChildEndpointPromise::CreateAndReject(false, __func__);
+  }
+
+  nsCOMPtr<nsIChannel> genChan(do_QueryInterface(channel));
+  if (!StaticPrefs::extensions_filterResponseServiceWorkerScript_disabled() &&
+      ChannelWrapper::IsServiceWorkerScript(genChan)) {
+    RefPtr<extensions::WebExtensionPolicy> addonPolicy =
+        ExtensionPolicyService::GetSingleton().GetByID(aAddonId);
+
+    if (!addonPolicy ||
+        !addonPolicy->HasPermission(
+            nsGkAtoms::webRequestFilterResponse_serviceWorkerScript)) {
+      return ChildEndpointPromise::CreateAndReject(false, __func__);
+    }
+  }
+
+  // Disable alt-data for extension stream listeners.
+  nsCOMPtr<nsIHttpChannelInternal> internal(do_QueryObject(channel));
+  internal->DisableAltDataCache();
+
+  return chan->AttachStreamFilter();
+}
+
+/* static */
+void StreamFilterParent::Attach(nsIChannel* aChannel,
+                                ParentEndpoint&& aEndpoint) {
+  auto self = MakeRefPtr<StreamFilterParent>();
+
+  self->ActorThread()->Dispatch(
+      NewRunnableMethod<ParentEndpoint&&>("StreamFilterParent::Bind", self,
+                                          &StreamFilterParent::Bind,
+                                          std::move(aEndpoint)),
+      NS_DISPATCH_NORMAL);
+
+  // If aChannel is a HttpChannelChild, ask HttpChannelChild to hold a weak
+  // reference on this StreamFilterParent. Such that HttpChannelChild has a
+  // chance to disconnect this StreamFilterParent if internal redirection
+  // happens, i.e. ServiceWorker fallback redirection.
+  RefPtr<net::HttpChannelChild> channelChild = do_QueryObject(aChannel);
+  if (channelChild) {
+    channelChild->RegisterStreamFilter(self);
+  }
+
+  self->Init(aChannel);
+}
+
+void StreamFilterParent::Disconnect(const nsACString& aReason) {
+  AssertIsMainThread();
+  MOZ_DIAGNOSTIC_ASSERT(mBeforeOnStartRequest);
+
+  mDisconnected = true;
+
+  nsAutoCString reason(aReason);
+
+  RefPtr<StreamFilterParent> self(this);
+  RunOnActorThread(FUNC, [self, reason] {
+    if (self->IPCActive()) {
+      self->mState = State::Disconnected;
+      self->CheckResult(self->SendError(reason));
+    }
+  });
+}
+
+void StreamFilterParent::Bind(ParentEndpoint&& aEndpoint) {
+  aEndpoint.Bind(this);
+}
+
+void StreamFilterParent::Init(nsIChannel* aChannel) {
+  mChannel = aChannel;
+
+  nsCOMPtr<nsITraceableChannel> traceable = do_QueryInterface(aChannel);
+  if (MOZ_UNLIKELY(!traceable)) {
+    // nsViewSourceChannel is not nsITraceableChannel, but wraps one. Unwrap it.
+    nsCOMPtr<nsIViewSourceChannel> vsc = do_QueryInterface(aChannel);
+    if (vsc) {
+      traceable = do_QueryObject(vsc->GetInnerChannel());
+      // OnStartRequest etc. is passed the unwrapped channel, so update mChannel
+      // to prevent OnStartRequest from mistaking it for a redirect, which would
+      // close the filter.
+      mChannel = do_QueryObject(traceable);
+    }
+    // TODO bug 1683403: Replace assertion; Close StreamFilter instead.
+    MOZ_RELEASE_ASSERT(traceable);
+  }
+
+  nsresult rv =
+      traceable->SetNewListener(this, /* aMustApplyContentConversion = */ true,
+                                getter_AddRefs(mOrigListener));
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+}
+
+/*****************************************************************************
+ * nsIThreadRetargetableStreamListener
+ *****************************************************************************/
+
+NS_IMETHODIMP
+StreamFilterParent::CheckListenerChain() {
+  AssertIsMainThread();
+
+  nsCOMPtr<nsIThreadRetargetableStreamListener> trsl =
+      do_QueryInterface(mOrigListener);
+  if (trsl) {
+    return trsl->CheckListenerChain();
+  }
+  return NS_ERROR_FAILURE;
+}
+
+/*****************************************************************************
+ * Error handling
+ *****************************************************************************/
+
+void StreamFilterParent::Broken() {
+  AssertIsActorThread();
+
+  switch (mState) {
+    case State::Initialized:
+    case State::TransferringData:
+    case State::Suspended: {
+      mState = State::Disconnecting;
+      RefPtr<StreamFilterParent> self(this);
+      RunOnMainThread(FUNC, [=] {
+        if (self->mChannel) {
+          self->mChannel->Cancel(NS_ERROR_FAILURE);
+        }
+      });
+
+      FinishDisconnect();
+    } break;
+
+    default:
+      break;
+  }
+}
+
+/*****************************************************************************
+ * State change requests
+ *****************************************************************************/
+
+IPCResult StreamFilterParent::RecvClose() {
+  AssertIsActorThread();
+
+  mState = State::Closed;
+
+  if (!mSentStop) {
+    RefPtr<StreamFilterParent> self(this);
+    RunOnMainThread(FUNC, [=] {
+      nsresult rv = self->EmitStopRequest(NS_OK);
+      Unused << NS_WARN_IF(NS_FAILED(rv));
+    });
+  }
+
+  Unused << SendClosed();
+  Destroy();
+  return IPC_OK();
+}
+
+void StreamFilterParent::Destroy() {
+  // Close the channel asynchronously so the actor is never destroyed before
+  // this message is fully processed.
+  ActorThread()->Dispatch(NewRunnableMethod("StreamFilterParent::Close", this,
+                                            &StreamFilterParent::Close),
+                          NS_DISPATCH_NORMAL);
+}
+
+IPCResult StreamFilterParent::RecvDestroy() {
+  AssertIsActorThread();
+  Destroy();
+  return IPC_OK();
+}
+
+IPCResult StreamFilterParent::RecvSuspend() {
+  AssertIsActorThread();
+
+  if (mState == State::TransferringData) {
+    RefPtr<StreamFilterParent> self(this);
+    RunOnMainThread(FUNC, [=] {
+      self->mChannel->Suspend();
+
+      RunOnActorThread(FUNC, [=] {
+        if (self->IPCActive()) {
+          self->mState = State::Suspended;
+          self->CheckResult(self->SendSuspended());
+        }
+      });
+    });
+  }
+  return IPC_OK();
+}
+
+IPCResult StreamFilterParent::RecvResume() {
+  AssertIsActorThread();
+
+  if (mState == State::Suspended) {
+    // Change state before resuming so incoming data is handled correctly
+    // immediately after resuming.
+    mState = State::TransferringData;
+
+    RefPtr<StreamFilterParent> self(this);
+    RunOnMainThread(FUNC, [=] {
+      self->mChannel->Resume();
+
+      RunOnActorThread(FUNC, [=] {
+        if (self->IPCActive()) {
+          self->CheckResult(self->SendResumed());
+        }
+      });
+    });
+  }
+  return IPC_OK();
+}
+IPCResult StreamFilterParent::RecvDisconnect() {
+  AssertIsActorThread();
+
+  if (mState == State::Suspended) {
+    RefPtr<StreamFilterParent> self(this);
+    RunOnMainThread(FUNC, [=] { self->mChannel->Resume(); });
+  } else if (mState != State::TransferringData) {
+    return IPC_OK();
+  }
+
+  mState = State::Disconnecting;
+  CheckResult(SendFlushData());
+  return IPC_OK();
+}
+
+IPCResult StreamFilterParent::RecvFlushedData() {
+  AssertIsActorThread();
+
+  MOZ_ASSERT(mState == State::Disconnecting);
+
+  Destroy();
+
+  FinishDisconnect();
+  return IPC_OK();
+}
+
+void StreamFilterParent::FinishDisconnect() {
+  RefPtr<StreamFilterParent> self(this);
+  RunOnIOThread(FUNC, [=] {
+    self->FlushBufferedData();
+
+    RunOnMainThread(FUNC, [=] {
+      if (self->mReceivedStop && !self->mSentStop) {
+        nsresult rv = self->EmitStopRequest(NS_OK);
+        Unused << NS_WARN_IF(NS_FAILED(rv));
+      } else if (self->mLoadGroup && !self->mDisconnected) {
+        Unused << self->mLoadGroup->RemoveRequest(self, nullptr, NS_OK);
+      }
+      self->mDisconnected = true;
+    });
+
+    RunOnActorThread(FUNC, [=] {
+      if (self->mState != State::Closed) {
+        self->mState = State::Disconnected;
+      }
+    });
+  });
+}
+
+/*****************************************************************************
+ * Data output
+ *****************************************************************************/
+
+IPCResult StreamFilterParent::RecvWrite(Data&& aData) {
+  AssertIsActorThread();
+
+  RunOnIOThread(NewRunnableMethod<Data&&>("StreamFilterParent::WriteMove", this,
+                                          &StreamFilterParent::WriteMove,
+                                          std::move(aData)));
+  return IPC_OK();
+}
+
+void StreamFilterParent::WriteMove(Data&& aData) {
+  nsresult rv = Write(aData);
+  Unused << NS_WARN_IF(NS_FAILED(rv));
+}
+
+nsresult StreamFilterParent::Write(Data& aData) {
+  AssertIsIOThread();
+
+  nsCOMPtr<nsIInputStream> stream;
+  nsresult rv = NS_NewByteInputStream(
+      getter_AddRefs(stream),
+      Span(reinterpret_cast<char*>(aData.Elements()), aData.Length()),
+      NS_ASSIGNMENT_DEPEND);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv =
+      mOrigListener->OnDataAvailable(mChannel, stream, mOffset, aData.Length());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mOffset += aData.Length();
+  return NS_OK;
+}
+
+/*****************************************************************************
+ * nsIRequest
+ *****************************************************************************/
+
+NS_IMETHODIMP
+StreamFilterParent::GetName(nsACString& aName) {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  return mChannel->GetName(aName);
+}
+
+NS_IMETHODIMP
+StreamFilterParent::GetStatus(nsresult* aStatus) {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  return mChannel->GetStatus(aStatus);
+}
+
+NS_IMETHODIMP
+StreamFilterParent::IsPending(bool* aIsPending) {
+  switch (mState) {
+    case State::Initialized:
+    case State::TransferringData:
+    case State::Suspended:
+      *aIsPending = true;
+      break;
+    default:
+      *aIsPending = false;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP StreamFilterParent::SetCanceledReason(const nsACString& aReason) {
+  return SetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP StreamFilterParent::GetCanceledReason(nsACString& aReason) {
+  return GetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP StreamFilterParent::CancelWithReason(nsresult aStatus,
+                                                   const nsACString& aReason) {
+  return CancelWithReasonImpl(aStatus, aReason);
+}
+
+NS_IMETHODIMP
+StreamFilterParent::Cancel(nsresult aResult) {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  return mChannel->Cancel(aResult);
+}
+
+NS_IMETHODIMP
+StreamFilterParent::Suspend() {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  return mChannel->Suspend();
+}
+
+NS_IMETHODIMP
+StreamFilterParent::Resume() {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  return mChannel->Resume();
+}
+
+NS_IMETHODIMP
+StreamFilterParent::GetLoadGroup(nsILoadGroup** aLoadGroup) {
+  *aLoadGroup = mLoadGroup;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StreamFilterParent::SetLoadGroup(nsILoadGroup* aLoadGroup) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+StreamFilterParent::GetLoadFlags(nsLoadFlags* aLoadFlags) {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  MOZ_TRY(mChannel->GetLoadFlags(aLoadFlags));
+  *aLoadFlags &= ~nsIChannel::LOAD_DOCUMENT_URI;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+StreamFilterParent::SetLoadFlags(nsLoadFlags aLoadFlags) {
+  AssertIsMainThread();
+  MOZ_ASSERT(mChannel);
+  return mChannel->SetLoadFlags(aLoadFlags);
+}
+
+NS_IMETHODIMP
+StreamFilterParent::GetTRRMode(nsIRequest::TRRMode* aTRRMode) {
+  return GetTRRModeImpl(aTRRMode);
+}
+
+NS_IMETHODIMP
+StreamFilterParent::SetTRRMode(nsIRequest::TRRMode aTRRMode) {
+  return SetTRRModeImpl(aTRRMode);
+}
+
+/*****************************************************************************
+ * nsIStreamListener
+ *****************************************************************************/
+
+NS_IMETHODIMP
+StreamFilterParent::OnStartRequest(nsIRequest* aRequest) {
+  AssertIsMainThread();
+
+  // Always reset mChannel if aRequest is different.  Various calls in
+  // StreamFilterParent will use mChannel, but aRequest is *always* the
+  // right channel to use at this point.
+  //
+  // For ALL redirections, we will disconnect this listener.  Extensions
+  // will create a new filter if they need it.
+  mBeforeOnStartRequest = false;
+  if (aRequest != mChannel) {
+    nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);
+    nsCOMPtr<nsILoadInfo> loadInfo = channel ? channel->LoadInfo() : nullptr;
+    mChannel = channel;
+
+    if (!(loadInfo &&
+          loadInfo->RedirectChainIncludingInternalRedirects().IsEmpty())) {
+      mDisconnected = true;
+      mDisconnectedByOnStartRequest = true;
+
+      RefPtr<StreamFilterParent> self(this);
+      RunOnActorThread(FUNC, [=] {
+        if (self->IPCActive()) {
+          self->mState = State::Disconnected;
+          CheckResult(self->SendError("Channel redirected"_ns));
+        }
+      });
+    }
+  }
+
+  // Check if alterate cached data is being sent, if so we receive un-decoded
+  // data and we must disconnect the filter and send an error to the extension.
+  if (!mDisconnected) {
+    RefPtr<net::HttpBaseChannel> chan = do_QueryObject(aRequest);
+    if (chan && chan->IsDeliveringAltData()) {
+      mDisconnected = true;
+      mDisconnectedByOnStartRequest = true;
+
+      RefPtr<StreamFilterParent> self(this);
+      RunOnActorThread(FUNC, [=] {
+        if (self->IPCActive()) {
+          self->mState = State::Disconnected;
+          CheckResult(
+              self->SendError("Channel is delivering cached alt-data"_ns));
+        }
+      });
+    }
+  }
+
+  if (!mDisconnected) {
+    Unused << mChannel->GetLoadGroup(getter_AddRefs(mLoadGroup));
+    if (mLoadGroup) {
+      Unused << mLoadGroup->AddRequest(this, nullptr);
+    }
+  }
+
+  nsresult rv = mOrigListener->OnStartRequest(aRequest);
+
+  // Important: Do this only *after* running the next listener in the chain, so
+  // that we get the final delivery target after any retargeting that it may do.
+  if (nsCOMPtr<nsIThreadRetargetableRequest> req =
+          do_QueryInterface(aRequest)) {
+    nsCOMPtr<nsISerialEventTarget> thread;
+    Unused << req->GetDeliveryTarget(getter_AddRefs(thread));
+    if (thread) {
+      mIOThread = std::move(thread);
+    }
+  }
+
+  // Important: Do this *after* we have set the thread delivery target, or it is
+  // possible in rare circumstances for an extension to attempt to write data
+  // before the thread has been set up, even though there are several layers of
+  // asynchrony involved.
+  if (!mDisconnected) {
+    RefPtr<StreamFilterParent> self(this);
+    RunOnActorThread(FUNC, [=] {
+      if (self->IPCActive()) {
+        self->mState = State::TransferringData;
+        self->CheckResult(self->SendStartRequest());
+      }
+    });
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+StreamFilterParent::OnStopRequest(nsIRequest* aRequest, nsresult aStatusCode) {
+  AssertIsMainThread();
+  MOZ_ASSERT(aRequest == mChannel);
+
+  mReceivedStop = true;
+  if (mDisconnected) {
+    return EmitStopRequest(aStatusCode);
+  }
+
+  RefPtr<StreamFilterParent> self(this);
+  RunOnActorThread(FUNC, [=] {
+    if (self->IPCActive()) {
+      self->CheckResult(self->SendStopRequest(aStatusCode));
+    } else if (self->mState != State::Disconnecting) {
+      // If we're currently disconnecting, then we'll emit a stop
+      // request at the end of that process. Otherwise we need to
+      // manually emit one here, since we won't be getting a response
+      // from the child.
+      RunOnMainThread(FUNC, [=] {
+        if (!self->mSentStop) {
+          self->EmitStopRequest(aStatusCode);
+        }
+      });
+    }
+  });
+  return NS_OK;
+}
+
+nsresult StreamFilterParent::EmitStopRequest(nsresult aStatusCode) {
+  AssertIsMainThread();
+  MOZ_ASSERT(!mSentStop);
+
+  mSentStop = true;
+  nsresult rv = mOrigListener->OnStopRequest(mChannel, aStatusCode);
+
+  if (mLoadGroup && !mDisconnected) {
+    Unused << mLoadGroup->RemoveRequest(this, nullptr, aStatusCode);
+  }
+
+  return rv;
+}
+
+/*****************************************************************************
+ * Incoming data handling
+ *****************************************************************************/
+
+void StreamFilterParent::DoSendData(Data&& aData) {
+  AssertIsActorThread();
+
+  if (mState == State::TransferringData) {
+    CheckResult(SendData(aData));
+  }
+}
+
+NS_IMETHODIMP
+StreamFilterParent::OnDataAvailable(nsIRequest* aRequest,
+                                    nsIInputStream* aInputStream,
+                                    uint64_t aOffset, uint32_t aCount) {
+  AssertIsIOThread();
+
+  if (mDisconnectedByOnStartRequest || mState == State::Disconnected) {
+    // If we're offloading data in a thread pool, it's possible that we'll
+    // have buffered some additional data while waiting for the buffer to
+    // flush. So, if there's any buffered data left, flush that before we
+    // flush this incoming data.
+    //
+    // Note: When in the eDisconnected state, the buffer list is guaranteed
+    // never to be accessed by another thread during an OnDataAvailable call.
+    if (!mBufferedData.isEmpty()) {
+      FlushBufferedData();
+    }
+
+    mOffset += aCount;
+    return mOrigListener->OnDataAvailable(aRequest, aInputStream,
+                                          mOffset - aCount, aCount);
+  }
+
+  Data data;
+  data.SetLength(aCount);
+
+  uint32_t count;
+  nsresult rv = aInputStream->Read(reinterpret_cast<char*>(data.Elements()),
+                                   aCount, &count);
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(count == aCount, NS_ERROR_UNEXPECTED);
+
+  if (mState == State::Disconnecting) {
+    MutexAutoLock al(mBufferMutex);
+    BufferData(std::move(data));
+  } else if (mState == State::Closed) {
+    return NS_ERROR_FAILURE;
+  } else {
+    ActorThread()->Dispatch(
+        NewRunnableMethod<Data&&>("StreamFilterParent::DoSendData", this,
+                                  &StreamFilterParent::DoSendData,
+                                  std::move(data)),
+        NS_DISPATCH_NORMAL);
+  }
+  return NS_OK;
+}
+
+nsresult StreamFilterParent::FlushBufferedData() {
+  AssertIsIOThread();
+
+  // When offloading data to a thread pool, OnDataAvailable isn't guaranteed
+  // to always run in the same thread, so it's possible for this function to
+  // run in parallel with OnDataAvailable.
+  MutexAutoLock al(mBufferMutex);
+
+  while (!mBufferedData.isEmpty()) {
+    UniquePtr<BufferedData> data(mBufferedData.popFirst());
+
+    nsresult rv = Write(data->mData);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+/*****************************************************************************
+ * Thread helpers
+ *****************************************************************************/
+
+nsIEventTarget* StreamFilterParent::ActorThread() {
+  return net::gSocketTransportService;
+}
+
+bool StreamFilterParent::IsActorThread() {
+  return ActorThread()->IsOnCurrentThread();
+}
+
+void StreamFilterParent::AssertIsActorThread() { MOZ_ASSERT(IsActorThread()); }
+
+nsISerialEventTarget* StreamFilterParent::IOThread() { return mIOThread; }
+
+bool StreamFilterParent::IsIOThread() { return mIOThread->IsOnCurrentThread(); }
+
+void StreamFilterParent::AssertIsIOThread() { MOZ_ASSERT(IsIOThread()); }
+
+template <typename Function>
+void StreamFilterParent::RunOnMainThread(const char* aName, Function&& aFunc) {
+  mQueue->RunOrEnqueue(new ChannelEventFunction(mMainThread, std::move(aFunc)));
+}
+
+void StreamFilterParent::RunOnMainThread(already_AddRefed<Runnable> aRunnable) {
+  mQueue->RunOrEnqueue(
+      new ChannelEventRunnable(mMainThread, std::move(aRunnable)));
+}
+
+template <typename Function>
+void StreamFilterParent::RunOnIOThread(const char* aName, Function&& aFunc) {
+  mQueue->RunOrEnqueue(new ChannelEventFunction(mIOThread, std::move(aFunc)));
+}
+
+void StreamFilterParent::RunOnIOThread(already_AddRefed<Runnable> aRunnable) {
+  mQueue->RunOrEnqueue(
+      new ChannelEventRunnable(mIOThread, std::move(aRunnable)));
+}
+
+template <typename Function>
+void StreamFilterParent::RunOnActorThread(const char* aName, Function&& aFunc) {
+  // We don't use mQueue for dispatch to the actor thread.
+  //
+  // The main thread and IO thread are used for dispatching events to the
+  // wrapped stream listener, and those events need to be processed
+  // consistently, in the order they were dispatched. An event dispatched to the
+  // main thread can't be run before events that were dispatched to the IO
+  // thread before it.
+  //
+  // Additionally, the IO thread is likely to be a thread pool, which means that
+  // without thread-safe queuing, it's possible for multiple events dispatched
+  // to it to be processed in parallel, or out of order.
+  //
+  // The actor thread, however, is always a serial event target. Its events are
+  // always processed in order, and events dispatched to the actor thread are
+  // independent of the events in the output event queue.
+  if (IsActorThread()) {
+    aFunc();
+  } else {
+    ActorThread()->Dispatch(std::move(NS_NewRunnableFunction(aName, aFunc)),
+                            NS_DISPATCH_NORMAL);
+  }
+}
+
+/*****************************************************************************
+ * Glue
+ *****************************************************************************/
+
+void StreamFilterParent::ActorDestroy(ActorDestroyReason aWhy) {
+  AssertIsActorThread();
+
+  if (mState != State::Disconnected && mState != State::Closed) {
+    Broken();
+  }
+}
+
+NS_INTERFACE_MAP_BEGIN(StreamFilterParent)
+  NS_INTERFACE_MAP_ENTRY(nsIStreamListener)
+  NS_INTERFACE_MAP_ENTRY(nsIRequestObserver)
+  NS_INTERFACE_MAP_ENTRY(nsIRequest)
+  NS_INTERFACE_MAP_ENTRY(nsIThreadRetargetableStreamListener)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIStreamListener)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_ADDREF(StreamFilterParent)
+NS_IMPL_RELEASE(StreamFilterParent)
+
+}  // namespace extensions
+}  // namespace mozilla
diff --git a/toolkit/components/extensions/webrequest/StreamFilterParent.h b/toolkit/components/extensions/webrequest/StreamFilterParent.h
new file mode 100644
index 0000000000..a4b011d41f
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/StreamFilterParent.h
@@ -0,0 +1,199 @@
+/* -*- 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_extensions_StreamFilterParent_h
+#define mozilla_extensions_StreamFilterParent_h
+
+#include "StreamFilterBase.h"
+#include "mozilla/extensions/PStreamFilterParent.h"
+
+#include "mozilla/LinkedList.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/WebRequestService.h"
+#include "nsIStreamListener.h"
+#include "nsIThread.h"
+#include "nsIThreadRetargetableStreamListener.h"
+#include "nsThreadUtils.h"
+
+#if defined(_MSC_VER)
+#  define FUNC __FUNCSIG__
+#else
+#  define FUNC __PRETTY_FUNCTION__
+#endif
+
+namespace mozilla {
+namespace dom {
+class ContentParent;
+}
+namespace net {
+class ChannelEventQueue;
+class nsHttpChannel;
+}  // namespace net
+
+namespace extensions {
+
+using namespace mozilla::dom;
+using mozilla::ipc::IPCResult;
+
+class StreamFilterParent final : public PStreamFilterParent,
+                                 public nsIStreamListener,
+                                 public nsIThreadRetargetableStreamListener,
+                                 public nsIRequest,
+                                 public StreamFilterBase {
+  friend class PStreamFilterParent;
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSISTREAMLISTENER
+  NS_DECL_NSIREQUEST
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER
+
+  StreamFilterParent();
+
+  using ParentEndpoint = mozilla::ipc::Endpoint<PStreamFilterParent>;
+  using ChildEndpoint = mozilla::ipc::Endpoint<PStreamFilterChild>;
+
+  using ChildEndpointPromise = MozPromise<ChildEndpoint, bool, true>;
+
+  [[nodiscard]] static RefPtr<ChildEndpointPromise> Create(
+      ContentParent* aContentParent, uint64_t aChannelId,
+      const nsAString& aAddonId);
+
+  static void Attach(nsIChannel* aChannel, ParentEndpoint&& aEndpoint);
+
+  enum class State {
+    // The parent has been created, but not yet constructed by the child.
+    Uninitialized,
+    // The parent has been successfully constructed.
+    Initialized,
+    // The OnRequestStarted event has been received, and data is being
+    // transferred to the child.
+    TransferringData,
+    // The channel is suspended.
+    Suspended,
+    // The channel has been closed by the child, and will send or receive data.
+    Closed,
+    // The channel is being disconnected from the child, so that all further
+    // data and events pass unfiltered to the output listener. Any data
+    // currnetly in transit to, or buffered by, the child will be written to the
+    // output listener before we enter the Disconnected atate.
+    Disconnecting,
+    // The channel has been disconnected from the child, and all further data
+    // and events will be passed directly to the output listener.
+    Disconnected,
+  };
+
+  // This method makes StreamFilterParent to disconnect from channel.
+  // Notice that this method can only be called before OnStartRequest().
+  void Disconnect(const nsACString& aReason);
+
+ protected:
+  virtual ~StreamFilterParent();
+
+  IPCResult RecvWrite(Data&& aData);
+  IPCResult RecvFlushedData();
+  IPCResult RecvSuspend();
+  IPCResult RecvResume();
+  IPCResult RecvClose();
+  IPCResult RecvDisconnect();
+  IPCResult RecvDestroy();
+
+ private:
+  bool IPCActive() {
+    return (mState != State::Closed && mState != State::Disconnecting &&
+            mState != State::Disconnected);
+  }
+
+  void Init(nsIChannel* aChannel);
+
+  void Bind(ParentEndpoint&& aEndpoint);
+
+  void Destroy();
+
+  nsresult FlushBufferedData();
+
+  nsresult Write(Data& aData);
+
+  void WriteMove(Data&& aData);
+
+  void DoSendData(Data&& aData);
+
+  nsresult EmitStopRequest(nsresult aStatusCode);
+
+  virtual void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  void Broken();
+  void FinishDisconnect();
+
+  void CheckResult(bool aResult) {
+    if (NS_WARN_IF(!aResult)) {
+      Broken();
+    }
+  }
+
+  inline nsIEventTarget* ActorThread();
+
+  inline nsISerialEventTarget* IOThread();
+
+  inline bool IsIOThread();
+
+  inline bool IsActorThread();
+
+  inline void AssertIsActorThread();
+
+  inline void AssertIsIOThread();
+
+  static void AssertIsMainThread() { MOZ_ASSERT(NS_IsMainThread()); }
+
+  template <typename Function>
+  void RunOnMainThread(const char* aName, Function&& aFunc);
+
+  void RunOnMainThread(already_AddRefed<Runnable> aRunnable);
+
+  template <typename Function>
+  void RunOnActorThread(const char* aName, Function&& aFunc);
+
+  template <typename Function>
+  void RunOnIOThread(const char* aName, Function&& aFunc);
+
+  void RunOnIOThread(already_AddRefed<Runnable>);
+
+  nsCOMPtr<nsIChannel> mChannel;
+  nsCOMPtr<nsILoadGroup> mLoadGroup;
+  nsCOMPtr<nsIStreamListener> mOrigListener;
+
+  nsCOMPtr<nsISerialEventTarget> mMainThread;
+  nsCOMPtr<nsISerialEventTarget> mIOThread;
+
+  RefPtr<net::ChannelEventQueue> mQueue;
+
+  Mutex mBufferMutex MOZ_UNANNOTATED;
+
+  bool mReceivedStop;
+  bool mSentStop;
+  bool mDisconnected = false;
+
+  // If redirection happens or alterate cached data is being sent, the stream
+  // filter is disconnected in OnStartRequest and the following ODA would not
+  // be filtered. Using mDisconnected causes race condition. mState is possible
+  // to late to be set, which leads out of sync.
+  bool mDisconnectedByOnStartRequest = false;
+
+  bool mBeforeOnStartRequest = true;
+
+  nsCOMPtr<nsISupports> mContext;
+  uint64_t mOffset;
+
+  // Use Release-Acquire ordering to ensure the OMT ODA is not sent while
+  // the channel is disconnecting or closed.
+  Atomic<State, ReleaseAcquire> mState;
+};
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // mozilla_extensions_StreamFilterParent_h
diff --git a/toolkit/components/extensions/webrequest/WebNavigationContent.cpp b/toolkit/components/extensions/webrequest/WebNavigationContent.cpp
new file mode 100644
index 0000000000..7de4516372
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/WebNavigationContent.cpp
@@ -0,0 +1,325 @@
+/* -*- 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/extensions/WebNavigationContent.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/ContentFrameMessageManager.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/EventTarget.h"
+#include "mozilla/extensions/ExtensionsChild.h"
+#include "mozilla/EventListenerManager.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/Services.h"
+#include "nsCRT.h"
+#include "nsDocShellLoadTypes.h"
+#include "nsPIWindowRoot.h"
+#include "nsIChannel.h"
+#include "nsIDocShell.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIObserverService.h"
+#include "nsIPropertyBag2.h"
+#include "nsIWebNavigation.h"
+#include "nsIWebProgress.h"
+#include "nsGlobalWindowOuter.h"
+#include "nsQueryObject.h"
+
+namespace mozilla {
+namespace extensions {
+
+/* static */
+already_AddRefed<WebNavigationContent> WebNavigationContent::GetSingleton() {
+  static RefPtr<WebNavigationContent> sSingleton;
+  if (!sSingleton) {
+    sSingleton = new WebNavigationContent();
+    sSingleton->Init();
+    ClearOnShutdown(&sSingleton);
+  }
+  return do_AddRef(sSingleton);
+}
+
+NS_IMPL_ISUPPORTS(WebNavigationContent, nsIObserver, nsIDOMEventListener,
+                  nsIWebProgressListener, nsISupportsWeakReference)
+
+void WebNavigationContent::Init() {
+  nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+
+  obs->AddObserver(this, "chrome-event-target-created", true);
+  obs->AddObserver(this, "webNavigation-createdNavigationTarget-from-js", true);
+}
+
+NS_IMETHODIMP WebNavigationContent::Observe(nsISupports* aSubject,
+                                            char const* aTopic,
+                                            char16_t const* aData) {
+  if (!nsCRT::strcmp(aTopic, "chrome-event-target-created")) {
+    // This notification is sent whenever a new window root is created, with the
+    // subject being an EventTarget corresponding to either an nsWindowRoot, or
+    // additionally also an InProcessBrowserChildMessageManager in the parent.
+    // This is the same entry point used to register listeners for the JS window
+    // actor API.
+    if (RefPtr<dom::EventTarget> eventTarget = do_QueryObject(aSubject)) {
+      AttachListeners(eventTarget);
+    }
+
+    nsCOMPtr<nsIDocShell> docShell;
+    if (nsCOMPtr<nsPIWindowRoot> root = do_QueryInterface(aSubject)) {
+      docShell = root->GetWindow()->GetDocShell();
+    } else if (RefPtr<dom::ContentFrameMessageManager> mm =
+                   do_QueryObject(aSubject)) {
+      docShell = mm->GetDocShell(IgnoreErrors());
+    }
+    if (docShell && docShell->GetBrowsingContext()->IsContent()) {
+      nsCOMPtr<nsIWebProgress> webProgress(do_GetInterface(docShell));
+
+      webProgress->AddProgressListener(this,
+                                       nsIWebProgress::NOTIFY_STATE_WINDOW |
+                                           nsIWebProgress::NOTIFY_LOCATION);
+    }
+  } else if (!nsCRT::strcmp(aTopic,
+                            "webNavigation-createdNavigationTarget-from-js")) {
+    if (nsCOMPtr<nsIPropertyBag2> props = do_QueryInterface(aSubject)) {
+      return OnCreatedNavigationTargetFromJS(props);
+    }
+  }
+  return NS_OK;
+}
+
+void WebNavigationContent::AttachListeners(dom::EventTarget* aEventTarget) {
+  EventListenerManager* elm = aEventTarget->GetOrCreateListenerManager();
+  NS_ENSURE_TRUE_VOID(elm);
+
+  elm->AddEventListenerByType(this, u"DOMContentLoaded"_ns,
+                              TrustedEventsAtCapture());
+}
+
+NS_IMETHODIMP
+WebNavigationContent::HandleEvent(dom::Event* aEvent) {
+  if (aEvent->ShouldIgnoreChromeEventTargetListener()) {
+    return NS_OK;
+  }
+
+#ifdef DEBUG
+  {
+    nsAutoString type;
+    aEvent->GetType(type);
+    MOZ_ASSERT(type.EqualsLiteral("DOMContentLoaded"));
+  }
+#endif
+
+  if (RefPtr<dom::Document> doc = do_QueryObject(aEvent->GetTarget())) {
+    dom::BrowsingContext* bc = doc->GetBrowsingContext();
+    if (bc && bc->IsContent()) {
+      ExtensionsChild::Get().SendDOMContentLoaded(bc, doc->GetDocumentURI());
+    }
+  }
+
+  return NS_OK;
+}
+
+static dom::BrowsingContext* GetBrowsingContext(nsIWebProgress* aWebProgress) {
+  // FIXME: Get this via nsIWebNavigation instead.
+  nsCOMPtr<nsIDocShell> docShell(do_GetInterface(aWebProgress));
+  return docShell->GetBrowsingContext();
+}
+
+FrameTransitionData WebNavigationContent::GetFrameTransitionData(
+    nsIWebProgress* aWebProgress, nsIRequest* aRequest) {
+  FrameTransitionData result;
+
+  uint32_t loadType = 0;
+  Unused << aWebProgress->GetLoadType(&loadType);
+
+  if (loadType & nsIDocShell::LOAD_CMD_HISTORY) {
+    result.forwardBack() = true;
+  }
+
+  if (loadType & nsIDocShell::LOAD_CMD_RELOAD) {
+    result.reload() = true;
+  }
+
+  if (LOAD_TYPE_HAS_FLAGS(loadType, nsIWebNavigation::LOAD_FLAGS_IS_REFRESH)) {
+    result.clientRedirect() = true;
+  }
+
+  if (nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest)) {
+    nsCOMPtr<nsILoadInfo> loadInfo(channel->LoadInfo());
+    if (loadInfo->RedirectChain().Length()) {
+      result.serverRedirect() = true;
+    }
+    if (loadInfo->GetIsFormSubmission() &&
+        !(loadType & (nsIDocShell::LOAD_CMD_HISTORY |
+
+                      nsIDocShell::LOAD_CMD_RELOAD))) {
+      result.formSubmit() = true;
+    }
+  }
+
+  return result;
+}
+
+nsresult WebNavigationContent::OnCreatedNavigationTargetFromJS(
+    nsIPropertyBag2* aProps) {
+  nsCOMPtr<nsIDocShell> createdDocShell(
+      do_GetProperty(aProps, u"createdTabDocShell"_ns));
+  nsCOMPtr<nsIDocShell> sourceDocShell(
+      do_GetProperty(aProps, u"sourceTabDocShell"_ns));
+
+  NS_ENSURE_ARG_POINTER(createdDocShell);
+  NS_ENSURE_ARG_POINTER(sourceDocShell);
+
+  dom::BrowsingContext* createdBC = createdDocShell->GetBrowsingContext();
+  dom::BrowsingContext* sourceBC = sourceDocShell->GetBrowsingContext();
+  if (createdBC->IsContent() && sourceBC->IsContent()) {
+    nsCString url;
+    Unused << aProps->GetPropertyAsACString(u"url"_ns, url);
+
+    ExtensionsChild::Get().SendCreatedNavigationTarget(createdBC, sourceBC,
+                                                       url);
+  }
+  return NS_OK;
+}
+
+// nsIWebProgressListener
+NS_IMETHODIMP
+WebNavigationContent::OnStateChange(nsIWebProgress* aWebProgress,
+                                    nsIRequest* aRequest, uint32_t aStateFlags,
+                                    nsresult aStatus) {
+  nsCOMPtr<nsIChannel> channel(do_QueryInterface(aRequest));
+  NS_ENSURE_TRUE(channel, NS_ERROR_UNEXPECTED);
+
+  nsCOMPtr<nsIURI> uri;
+  MOZ_TRY(channel->GetURI(getter_AddRefs(uri)));
+
+  // Prevents "about", "chrome", "resource" and "moz-extension" URI schemes to
+  // be reported with the resolved "file" or "jar" URIs (see bug 1246125)
+  if (uri->SchemeIs("file") || uri->SchemeIs("jar")) {
+    nsCOMPtr<nsIURI> originalURI;
+    MOZ_TRY(channel->GetOriginalURI(getter_AddRefs(originalURI)));
+    // FIXME: We probably actually want NS_GetFinalChannelURI here.
+    if (originalURI->SchemeIs("about") || originalURI->SchemeIs("chrome") ||
+        originalURI->SchemeIs("resource") ||
+        originalURI->SchemeIs("moz-extension")) {
+      uri = originalURI.forget();
+    }
+  }
+
+  RefPtr<dom::BrowsingContext> bc(GetBrowsingContext(aWebProgress));
+  NS_ENSURE_ARG_POINTER(bc);
+
+  ExtensionsChild::Get().SendStateChange(bc, uri, aStatus, aStateFlags);
+
+  // Based on the docs of the webNavigation.onCommitted event, it should be
+  // raised when: "The document  might still be downloading, but at least part
+  // of the document has been received" and for some reason we don't fire
+  // onLocationChange for the initial navigation of a sub-frame. For the above
+  // two reasons, when the navigation event is related to a sub-frame we process
+  // the document change here and then send an OnDocumentChange message to the
+  // main process, where it will be turned into a webNavigation.onCommitted
+  // event. (bug 1264936 and bug 125662)
+  if (!bc->IsTop() && aStateFlags & nsIWebProgressListener::STATE_IS_DOCUMENT) {
+    ExtensionsChild::Get().SendDocumentChange(
+        bc, GetFrameTransitionData(aWebProgress, aRequest), uri);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebNavigationContent::OnProgressChange(nsIWebProgress* aWebProgress,
+                                       nsIRequest* aRequest,
+                                       int32_t aCurSelfProgress,
+                                       int32_t aMaxSelfProgress,
+                                       int32_t aCurTotalProgress,
+                                       int32_t aMaxTotalProgress) {
+  MOZ_ASSERT_UNREACHABLE("Listener did not request ProgressChange events");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebNavigationContent::OnLocationChange(nsIWebProgress* aWebProgress,
+                                       nsIRequest* aRequest, nsIURI* aLocation,
+                                       uint32_t aFlags) {
+  RefPtr<dom::BrowsingContext> bc(GetBrowsingContext(aWebProgress));
+  NS_ENSURE_ARG_POINTER(bc);
+
+  // When a frame navigation doesn't change the current loaded document
+  // (which can be due to history.pushState/replaceState or to a changed hash in
+  // the url), it is reported only to the onLocationChange, for this reason we
+  // process the history change here and then we are going to send an
+  // OnHistoryChange message to the main process, where it will be turned into
+  // a webNavigation.onHistoryStateUpdated/onReferenceFragmentUpdated event.
+  if (aFlags & nsIWebProgressListener::LOCATION_CHANGE_SAME_DOCUMENT) {
+    uint32_t loadType = 0;
+    MOZ_TRY(aWebProgress->GetLoadType(&loadType));
+
+    // When the location changes but the document is the same:
+    // - path not changed and hash changed -> |onReferenceFragmentUpdated|
+    //   (even if it changed using |history.pushState|)
+    // - path not changed and hash not changed -> |onHistoryStateUpdated|
+    //   (only if it changes using |history.pushState|)
+    // - path changed -> |onHistoryStateUpdated|
+    bool isHistoryStateUpdated = false;
+    bool isReferenceFragmentUpdated = false;
+    if (aFlags & nsIWebProgressListener::LOCATION_CHANGE_HASHCHANGE) {
+      isReferenceFragmentUpdated = true;
+    } else if (loadType & nsIDocShell::LOAD_CMD_PUSHSTATE) {
+      isHistoryStateUpdated = true;
+    } else if (loadType & nsIDocShell::LOAD_CMD_HISTORY) {
+      isHistoryStateUpdated = true;
+    }
+
+    if (isHistoryStateUpdated || isReferenceFragmentUpdated) {
+      ExtensionsChild::Get().SendHistoryChange(
+          bc, GetFrameTransitionData(aWebProgress, aRequest), aLocation,
+          isHistoryStateUpdated, isReferenceFragmentUpdated);
+    }
+  } else if (bc->IsTop()) {
+    MOZ_ASSERT(bc->IsInProcess());
+    if (RefPtr browserChild = dom::BrowserChild::GetFrom(bc->GetDocShell())) {
+      // Only send progress events which happen after we've started loading
+      // things into the BrowserChild. This matches the behavior of the remote
+      // WebProgress implementation.
+      if (browserChild->ShouldSendWebProgressEventsToParent()) {
+        // We have to catch the document changes from top level frames here,
+        // where we can detect the "server redirect" transition.
+        // (bug 1264936 and bug 125662)
+        ExtensionsChild::Get().SendDocumentChange(
+            bc, GetFrameTransitionData(aWebProgress, aRequest), aLocation);
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebNavigationContent::OnStatusChange(nsIWebProgress* aWebProgress,
+                                     nsIRequest* aRequest, nsresult aStatus,
+                                     const char16_t* aMessage) {
+  MOZ_ASSERT_UNREACHABLE("Listener did not request StatusChange events");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebNavigationContent::OnSecurityChange(nsIWebProgress* aWebProgress,
+                                       nsIRequest* aRequest, uint32_t aState) {
+  MOZ_ASSERT_UNREACHABLE("Listener did not request SecurityChange events");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebNavigationContent::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             uint32_t aEvent) {
+  MOZ_ASSERT_UNREACHABLE("Listener did not request ContentBlocking events");
+  return NS_OK;
+}
+
+}  // namespace extensions
+}  // namespace mozilla
diff --git a/toolkit/components/extensions/webrequest/WebNavigationContent.h b/toolkit/components/extensions/webrequest/WebNavigationContent.h
new file mode 100644
index 0000000000..8916b4436e
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/WebNavigationContent.h
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 2; 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_extensions_WebNavigationContent_h
+#define mozilla_extensions_WebNavigationContent_h
+
+#include "nsIDOMEventListener.h"
+#include "nsIObserver.h"
+#include "nsIWebProgressListener.h"
+#include "nsWeakReference.h"
+
+class nsIPropertyBag2;
+class nsIRequest;
+class nsIWebProgress;
+
+namespace mozilla {
+namespace dom {
+class EventTarget;
+}  // namespace dom
+
+namespace extensions {
+
+class FrameTransitionData;
+
+class WebNavigationContent final : public nsIObserver,
+                                   public nsIDOMEventListener,
+                                   public nsIWebProgressListener,
+                                   public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+  NS_DECL_NSIDOMEVENTLISTENER
+  NS_DECL_NSIWEBPROGRESSLISTENER
+
+  static already_AddRefed<WebNavigationContent> GetSingleton();
+
+ private:
+  WebNavigationContent() = default;
+  ~WebNavigationContent() = default;
+
+  void AttachListeners(mozilla::dom::EventTarget* aEventTarget);
+
+  void Init();
+
+  FrameTransitionData GetFrameTransitionData(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest);
+
+  nsresult OnCreatedNavigationTargetFromJS(nsIPropertyBag2* aProps);
+};
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // defined mozilla_extensions_WebNavigationContent_h
diff --git a/toolkit/components/extensions/webrequest/WebRequest.sys.mjs b/toolkit/components/extensions/webrequest/WebRequest.sys.mjs
new file mode 100644
index 0000000000..e6e81f5484
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/WebRequest.sys.mjs
@@ -0,0 +1,1338 @@
+/* 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/. */
+
+const { nsIHttpActivityObserver, nsISocketTransport } = Ci;
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  ExtensionParent: "resource://gre/modules/ExtensionParent.sys.mjs",
+  ExtensionUtils: "resource://gre/modules/ExtensionUtils.sys.mjs",
+  SecurityInfo: "resource://gre/modules/SecurityInfo.sys.mjs",
+  WebRequestUpload: "resource://gre/modules/WebRequestUpload.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(lazy, {
+  ExtensionDNR: "resource://gre/modules/ExtensionDNR.jsm",
+});
+
+// WebRequest.jsm's only consumer is ext-webRequest.js, so we can depend on
+// the apiManager.global being initialized.
+XPCOMUtils.defineLazyGetter(lazy, "tabTracker", () => {
+  return lazy.ExtensionParent.apiManager.global.tabTracker;
+});
+XPCOMUtils.defineLazyGetter(lazy, "getCookieStoreIdForOriginAttributes", () => {
+  return lazy.ExtensionParent.apiManager.global
+    .getCookieStoreIdForOriginAttributes;
+});
+
+// URI schemes that service workers are allowed to load scripts from (any other
+// scheme is not allowed by the specs and it is not expected by the service workers
+// internals neither, which would likely trigger unexpected behaviors).
+const ALLOWED_SERVICEWORKER_SCHEMES = ["https", "http", "moz-extension"];
+
+// Response HTTP Headers matching the following patterns are restricted for changes
+// applied by MV3 extensions.
+const MV3_RESTRICTED_HEADERS_PATTERNS = [
+  /^cross-origin-embedder-policy$/,
+  /^cross-origin-opener-policy$/,
+  /^cross-origin-resource-policy$/,
+  /^x-frame-options$/,
+  /^access-control-/,
+];
+
+// Classes of requests that should be sent immediately instead of batched.
+// Covers basically anything that can delay first paint or DOMContentLoaded:
+// top frame HTML, <head> blocking CSS, fonts preflight, sync JS and XHR.
+const URGENT_CLASSES =
+  Ci.nsIClassOfService.Leader |
+  Ci.nsIClassOfService.Unblocked |
+  Ci.nsIClassOfService.UrgentStart |
+  Ci.nsIClassOfService.TailForbidden;
+
+function runLater(job) {
+  Services.tm.dispatchToMainThread(job);
+}
+
+function parseFilter(filter) {
+  if (!filter) {
+    filter = {};
+  }
+
+  return {
+    urls: filter.urls || null,
+    types: filter.types || null,
+    tabId: filter.tabId ?? null,
+    windowId: filter.windowId ?? null,
+    incognito: filter.incognito ?? null,
+  };
+}
+
+function parseExtra(extra, allowed = [], optionsObj = {}) {
+  if (extra) {
+    for (let ex of extra) {
+      if (!allowed.includes(ex)) {
+        throw new lazy.ExtensionUtils.ExtensionError(`Invalid option ${ex}`);
+      }
+    }
+  }
+
+  let result = Object.assign({}, optionsObj);
+  for (let al of allowed) {
+    if (extra && extra.includes(al)) {
+      result[al] = true;
+    }
+  }
+  return result;
+}
+
+function isThenable(value) {
+  return value && typeof value === "object" && typeof value.then === "function";
+}
+
+// Verify a requested redirect and throw a more explicit error.
+function verifyRedirect(channel, redirectUri, finalUrl, addonId) {
+  const { isServiceWorkerScript } = channel;
+
+  if (
+    isServiceWorkerScript &&
+    channel.loadInfo?.internalContentPolicyType ===
+      Ci.nsIContentPolicy.TYPE_INTERNAL_SERVICE_WORKER
+  ) {
+    throw new Error(
+      `Invalid redirectUrl ${redirectUri?.spec} on service worker main script ${finalUrl} requested by ${addonId}`
+    );
+  }
+
+  if (
+    isServiceWorkerScript &&
+    (channel.loadInfo?.internalContentPolicyType ===
+      Ci.nsIContentPolicy.TYPE_INTERNAL_WORKER_IMPORT_SCRIPTS ||
+      channel.loadInfo?.internalContentPolicyType ===
+        Ci.nsIContentPolicy.TYPE_INTERNAL_WORKER_STATIC_MODULE) &&
+    !ALLOWED_SERVICEWORKER_SCHEMES.includes(redirectUri?.scheme)
+  ) {
+    throw new Error(
+      `Invalid redirectUrl ${redirectUri?.spec} on service worker imported script ${finalUrl} requested by ${addonId}`
+    );
+  }
+}
+
+class HeaderChanger {
+  constructor(channel) {
+    this.channel = channel;
+
+    this.array = this.readHeaders();
+  }
+
+  getMap() {
+    if (!this.map) {
+      this.map = new Map();
+      for (let header of this.array) {
+        this.map.set(header.name.toLowerCase(), header);
+      }
+    }
+    return this.map;
+  }
+
+  toArray() {
+    return this.array;
+  }
+
+  validateHeaders(headers) {
+    // We should probably use schema validation for this.
+
+    if (!Array.isArray(headers)) {
+      return false;
+    }
+
+    return headers.every(header => {
+      if (typeof header !== "object" || header === null) {
+        return false;
+      }
+
+      if (typeof header.name !== "string") {
+        return false;
+      }
+
+      return (
+        typeof header.value === "string" || Array.isArray(header.binaryValue)
+      );
+    });
+  }
+
+  applyChanges(headers, opts = {}) {
+    if (!this.validateHeaders(headers)) {
+      /* globals uneval */
+      Cu.reportError(`Invalid header array: ${uneval(headers)}`);
+      return;
+    }
+
+    let newHeaders = new Set(headers.map(({ name }) => name.toLowerCase()));
+
+    // Remove missing headers.
+    let origHeaders = this.getMap();
+    for (let name of origHeaders.keys()) {
+      if (!newHeaders.has(name)) {
+        this.setHeader(name, "", false, opts, name);
+      }
+    }
+
+    // Set new or changed headers.  If there are multiple headers with the same
+    // name (e.g. Set-Cookie), merge them, instead of having new values
+    // overwrite previous ones.
+    //
+    // When the new value of a header is equal the existing value of the header
+    // (e.g. the initial response set "Set-Cookie: examplename=examplevalue",
+    // and an extension also added the header
+    // "Set-Cookie: examplename=examplevalue") then the header value is not
+    // re-set, but subsequent headers of the same type will be merged in.
+    //
+    // Multiple addons will be able to provide modifications to any headers
+    // listed in the default set.
+    let headersAlreadySet = new Set();
+    for (let { name, value, binaryValue } of headers) {
+      if (binaryValue) {
+        value = String.fromCharCode(...binaryValue);
+      }
+
+      let lowerCaseName = name.toLowerCase();
+      let original = origHeaders.get(lowerCaseName);
+
+      if (!original || value !== original.value) {
+        let shouldMerge = headersAlreadySet.has(lowerCaseName);
+        this.setHeader(name, value, shouldMerge, opts, lowerCaseName);
+      }
+
+      headersAlreadySet.add(lowerCaseName);
+    }
+  }
+}
+
+const checkRestrictedHeaderValue = (value, opts = {}) => {
+  let uri = Services.io.newURI(`https://${value}/`);
+  let { policy } = opts;
+
+  if (policy && !policy.allowedOrigins.matches(uri)) {
+    throw new Error(`Unable to set host header, url missing from permissions.`);
+  }
+
+  if (WebExtensionPolicy.isRestrictedURI(uri)) {
+    throw new Error(`Unable to set host header to restricted url.`);
+  }
+};
+
+class RequestHeaderChanger extends HeaderChanger {
+  setHeader(name, value, merge, opts, lowerCaseName) {
+    try {
+      if (value && lowerCaseName === "host") {
+        checkRestrictedHeaderValue(value, opts);
+      }
+      this.channel.setRequestHeader(name, value, merge);
+    } catch (e) {
+      Cu.reportError(new Error(`Error setting request header ${name}: ${e}`));
+    }
+  }
+
+  readHeaders() {
+    return this.channel.getRequestHeaders();
+  }
+}
+
+class ResponseHeaderChanger extends HeaderChanger {
+  didModifyCSP = false;
+
+  setHeader(name, value, merge, opts, lowerCaseName) {
+    if (lowerCaseName === "content-security-policy") {
+      // When multiple add-ons change the CSP, enforce the combined (strictest)
+      // policy - see bug 1462989 for motivation.
+      // When value is unset, don't force the header to be merged, to allow
+      // add-ons to clear the header if wanted.
+      if (value) {
+        merge = merge || this.didModifyCSP;
+      }
+
+      // For manifest_version 3 extension, we are currently only allowing to
+      // merge additional CSP strings to the existing ones, which will be initially
+      // stricter than currently allowed to manifest_version 2 extensions, then
+      // following up with either a new permission and/or some more changes to the
+      // APIs (and possibly making the behavior more deterministic than it is for
+      // manifest_version 2 at the moment).
+      if (opts.policy.manifestVersion > 2) {
+        if (value) {
+          // If the given CSP header value is non empty, then it should be
+          // merged to the existing one.
+          merge = true;
+        } else {
+          // If the given CSP header value is empty (which would be clearing the
+          // CSP header), it should be considered a no-op and this.didModifyCSP
+          // shouldn't be changed to true.
+          return;
+        }
+      }
+
+      this.didModifyCSP = true;
+    } else if (
+      opts.policy.manifestVersion > 2 &&
+      this.isResponseHeaderRestricted(lowerCaseName)
+    ) {
+      // TODO (Bug 1787155 and Bug 1273281) open this up to MV3 extensions,
+      // locked behind manifest.json declarative permission and a separate
+      // explicit user-controlled permission (and ideally also check for
+      // changes that would lead to security downgrades).
+      Cu.reportError(
+        `Disallowed change restricted response header ${name} on ${this.channel.finalURL} from ${opts.policy.debugName}`
+      );
+      return;
+    }
+
+    try {
+      this.channel.setResponseHeader(name, value, merge);
+    } catch (e) {
+      Cu.reportError(new Error(`Error setting response header ${name}: ${e}`));
+    }
+  }
+
+  isResponseHeaderRestricted(lowerCaseHeaderName) {
+    return MV3_RESTRICTED_HEADERS_PATTERNS.some(regex =>
+      regex.test(lowerCaseHeaderName)
+    );
+  }
+
+  readHeaders() {
+    return this.channel.getResponseHeaders();
+  }
+}
+
+const MAYBE_CACHED_EVENTS = new Set([
+  "onResponseStarted",
+  "onHeadersReceived",
+  "onBeforeRedirect",
+  "onCompleted",
+  "onErrorOccurred",
+]);
+
+const OPTIONAL_PROPERTIES = [
+  "requestHeaders",
+  "responseHeaders",
+  "statusCode",
+  "statusLine",
+  "error",
+  "redirectUrl",
+  "requestBody",
+  "scheme",
+  "realm",
+  "isProxy",
+  "challenger",
+  "proxyInfo",
+  "ip",
+  "frameAncestors",
+  "urlClassification",
+  "requestSize",
+  "responseSize",
+];
+
+function serializeRequestData(eventName) {
+  let data = {
+    requestId: this.requestId,
+    url: this.url,
+    originUrl: this.originUrl,
+    documentUrl: this.documentUrl,
+    method: this.method,
+    type: this.type,
+    timeStamp: Date.now(),
+    tabId: this.tabId,
+    frameId: this.frameId,
+    parentFrameId: this.parentFrameId,
+    incognito: this.incognito,
+    thirdParty: this.thirdParty,
+    cookieStoreId: this.cookieStoreId,
+    urgentSend: this.urgentSend,
+  };
+
+  if (MAYBE_CACHED_EVENTS.has(eventName)) {
+    data.fromCache = !!this.fromCache;
+  }
+
+  for (let opt of OPTIONAL_PROPERTIES) {
+    if (typeof this[opt] !== "undefined") {
+      data[opt] = this[opt];
+    }
+  }
+
+  if (this.urlClassification) {
+    data.urlClassification = {
+      firstParty: this.urlClassification.firstParty.filter(
+        c => !c.startsWith("socialtracking_")
+      ),
+      thirdParty: this.urlClassification.thirdParty.filter(
+        c => !c.startsWith("socialtracking_")
+      ),
+    };
+  }
+
+  return data;
+}
+
+var HttpObserverManager;
+
+var ChannelEventSink = {
+  _classDescription: "WebRequest channel event sink",
+  _classID: Components.ID("115062f8-92f1-11e5-8b7f-080027b0f7ec"),
+  _contractID: "@mozilla.org/webrequest/channel-event-sink;1",
+
+  QueryInterface: ChromeUtils.generateQI(["nsIChannelEventSink", "nsIFactory"]),
+
+  init() {
+    Components.manager
+      .QueryInterface(Ci.nsIComponentRegistrar)
+      .registerFactory(
+        this._classID,
+        this._classDescription,
+        this._contractID,
+        this
+      );
+  },
+
+  register() {
+    Services.catMan.addCategoryEntry(
+      "net-channel-event-sinks",
+      this._contractID,
+      this._contractID,
+      false,
+      true
+    );
+  },
+
+  unregister() {
+    Services.catMan.deleteCategoryEntry(
+      "net-channel-event-sinks",
+      this._contractID,
+      false
+    );
+  },
+
+  // nsIChannelEventSink implementation
+  asyncOnChannelRedirect(oldChannel, newChannel, flags, redirectCallback) {
+    runLater(() => redirectCallback.onRedirectVerifyCallback(Cr.NS_OK));
+    try {
+      HttpObserverManager.onChannelReplaced(oldChannel, newChannel);
+    } catch (e) {
+      // we don't wanna throw: it would abort the redirection
+    }
+  },
+
+  // nsIFactory implementation
+  createInstance(iid) {
+    return this.QueryInterface(iid);
+  },
+};
+
+ChannelEventSink.init();
+
+// nsIAuthPrompt2 implementation for onAuthRequired
+class AuthRequestor {
+  constructor(channel, httpObserver) {
+    this.notificationCallbacks = channel.notificationCallbacks;
+    this.loadGroupCallbacks =
+      channel.loadGroup && channel.loadGroup.notificationCallbacks;
+    this.httpObserver = httpObserver;
+  }
+
+  getInterface(iid) {
+    if (iid.equals(Ci.nsIAuthPromptProvider) || iid.equals(Ci.nsIAuthPrompt2)) {
+      return this;
+    }
+    try {
+      return this.notificationCallbacks.getInterface(iid);
+    } catch (e) {}
+    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
+  }
+
+  _getForwardedInterface(iid) {
+    try {
+      return this.notificationCallbacks.getInterface(iid);
+    } catch (e) {
+      return this.loadGroupCallbacks.getInterface(iid);
+    }
+  }
+
+  // nsIAuthPromptProvider getAuthPrompt
+  getAuthPrompt(reason, iid) {
+    // This should never get called without getInterface having been called first.
+    if (iid.equals(Ci.nsIAuthPrompt2)) {
+      return this;
+    }
+    return this._getForwardedInterface(Ci.nsIAuthPromptProvider).getAuthPrompt(
+      reason,
+      iid
+    );
+  }
+
+  // nsIAuthPrompt2 promptAuth
+  promptAuth(channel, level, authInfo) {
+    this._getForwardedInterface(Ci.nsIAuthPrompt2).promptAuth(
+      channel,
+      level,
+      authInfo
+    );
+  }
+
+  _getForwardPrompt(data) {
+    let reason = data.isProxy
+      ? Ci.nsIAuthPromptProvider.PROMPT_PROXY
+      : Ci.nsIAuthPromptProvider.PROMPT_NORMAL;
+    for (let callbacks of [
+      this.notificationCallbacks,
+      this.loadGroupCallbacks,
+    ]) {
+      try {
+        return callbacks
+          .getInterface(Ci.nsIAuthPromptProvider)
+          .getAuthPrompt(reason, Ci.nsIAuthPrompt2);
+      } catch (e) {}
+      try {
+        return callbacks.getInterface(Ci.nsIAuthPrompt2);
+      } catch (e) {}
+    }
+    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
+  }
+
+  // nsIAuthPrompt2 asyncPromptAuth
+  asyncPromptAuth(channel, callback, context, level, authInfo) {
+    let wrapper = ChannelWrapper.get(channel);
+
+    let uri = channel.URI;
+    let proxyInfo;
+    let isProxy = !!(authInfo.flags & authInfo.AUTH_PROXY);
+    if (isProxy && channel instanceof Ci.nsIProxiedChannel) {
+      proxyInfo = channel.proxyInfo;
+    }
+    let data = {
+      scheme: authInfo.authenticationScheme,
+      realm: authInfo.realm,
+      isProxy,
+      challenger: {
+        host: proxyInfo ? proxyInfo.host : uri.host,
+        port: proxyInfo ? proxyInfo.port : uri.port,
+      },
+    };
+
+    // In the case that no listener provides credentials, we fallback to the
+    // previously set callback class for authentication.
+    wrapper.authPromptForward = () => {
+      try {
+        let prompt = this._getForwardPrompt(data);
+        prompt.asyncPromptAuth(channel, callback, context, level, authInfo);
+      } catch (e) {
+        Cu.reportError(`webRequest asyncPromptAuth failure ${e}`);
+        callback.onAuthCancelled(context, false);
+      }
+      wrapper.authPromptForward = null;
+      wrapper.authPromptCallback = null;
+    };
+    wrapper.authPromptCallback = authCredentials => {
+      // The API allows for canceling the request, providing credentials or
+      // doing nothing, so we do not provide a way to call onAuthCanceled.
+      // Canceling the request will result in canceling the authentication.
+      if (
+        authCredentials &&
+        typeof authCredentials.username === "string" &&
+        typeof authCredentials.password === "string"
+      ) {
+        authInfo.username = authCredentials.username;
+        authInfo.password = authCredentials.password;
+        try {
+          callback.onAuthAvailable(context, authInfo);
+        } catch (e) {
+          Cu.reportError(`webRequest onAuthAvailable failure ${e}`);
+        }
+        // At least one addon has responded, so we won't forward to the regular
+        // prompt handlers.
+        wrapper.authPromptForward = null;
+        wrapper.authPromptCallback = null;
+      }
+    };
+
+    this.httpObserver.runChannelListener(wrapper, "onAuthRequired", data);
+
+    return {
+      QueryInterface: ChromeUtils.generateQI(["nsICancelable"]),
+      cancel() {
+        try {
+          callback.onAuthCancelled(context, false);
+        } catch (e) {
+          Cu.reportError(`webRequest onAuthCancelled failure ${e}`);
+        }
+        wrapper.authPromptForward = null;
+        wrapper.authPromptCallback = null;
+      },
+    };
+  }
+}
+
+AuthRequestor.prototype.QueryInterface = ChromeUtils.generateQI([
+  "nsIInterfaceRequestor",
+  "nsIAuthPromptProvider",
+  "nsIAuthPrompt2",
+]);
+
+// Most WebRequest events are implemented via the observer services, but
+// a few use custom xpcom interfaces.  This class (HttpObserverManager)
+// serves two main purposes:
+//  1. It abstracts away the names and details of the underlying
+//     implementation (e.g., onBeforeBeforeRequest is dispatched from
+//     the http-on-modify-request observable).
+//  2. It aggregates multiple listeners so that a single observer or
+//     handler can serve multiple webRequest listeners.
+HttpObserverManager = {
+  listeners: {
+    // onBeforeRequest uses http-on-modify observer for HTTP(S).
+    onBeforeRequest: new Map(),
+
+    // onBeforeSendHeaders and onSendHeaders correspond to the
+    // http-on-before-connect observer.
+    onBeforeSendHeaders: new Map(),
+    onSendHeaders: new Map(),
+
+    // onHeadersReceived corresponds to the http-on-examine-* obserservers.
+    onHeadersReceived: new Map(),
+
+    // onAuthRequired is handled via the nsIAuthPrompt2 xpcom interface
+    // which is managed here by AuthRequestor.
+    onAuthRequired: new Map(),
+
+    // onBeforeRedirect is handled by the nsIChannelEVentSink xpcom interface
+    // which is managed here by ChannelEventSink.
+    onBeforeRedirect: new Map(),
+
+    // onResponseStarted, onErrorOccurred, and OnCompleted correspond
+    // to events dispatched by the ChannelWrapper EventTarget.
+    onResponseStarted: new Map(),
+    onErrorOccurred: new Map(),
+    onCompleted: new Map(),
+  },
+  // Whether there are any registered declarativeNetRequest rules. These DNR
+  // rules may match new requests and result in request modifications.
+  dnrActive: false,
+
+  openingInitialized: false,
+  beforeConnectInitialized: false,
+  examineInitialized: false,
+  redirectInitialized: false,
+  activityInitialized: false,
+  needTracing: false,
+  hasRedirects: false,
+
+  getWrapper(nativeChannel) {
+    let wrapper = ChannelWrapper.get(nativeChannel);
+    if (!wrapper._addedListeners) {
+      /* eslint-disable mozilla/balanced-listeners */
+      if (this.listeners.onErrorOccurred.size) {
+        wrapper.addEventListener("error", this);
+      }
+      if (this.listeners.onResponseStarted.size) {
+        wrapper.addEventListener("start", this);
+      }
+      if (this.listeners.onCompleted.size) {
+        wrapper.addEventListener("stop", this);
+      }
+      /* eslint-enable mozilla/balanced-listeners */
+
+      wrapper._addedListeners = true;
+    }
+    return wrapper;
+  },
+
+  get activityDistributor() {
+    return Cc["@mozilla.org/network/http-activity-distributor;1"].getService(
+      Ci.nsIHttpActivityDistributor
+    );
+  },
+
+  // This method is called whenever webRequest listeners are added or removed.
+  // It reconciles the set of listeners with underlying observers, event
+  // handlers, etc. by adding new low-level handlers for any newly added
+  // webRequest listeners and removing those that are no longer needed if
+  // there are no more listeners for corresponding webRequest events.
+  addOrRemove() {
+    let needOpening = this.listeners.onBeforeRequest.size || this.dnrActive;
+    let needBeforeConnect =
+      this.listeners.onBeforeSendHeaders.size ||
+      this.listeners.onSendHeaders.size ||
+      this.dnrActive;
+    if (needOpening && !this.openingInitialized) {
+      this.openingInitialized = true;
+      Services.obs.addObserver(this, "http-on-modify-request");
+    } else if (!needOpening && this.openingInitialized) {
+      this.openingInitialized = false;
+      Services.obs.removeObserver(this, "http-on-modify-request");
+    }
+    if (needBeforeConnect && !this.beforeConnectInitialized) {
+      this.beforeConnectInitialized = true;
+      Services.obs.addObserver(this, "http-on-before-connect");
+    } else if (!needBeforeConnect && this.beforeConnectInitialized) {
+      this.beforeConnectInitialized = false;
+      Services.obs.removeObserver(this, "http-on-before-connect");
+    }
+
+    let haveBlocking = Object.values(this.listeners).some(listeners =>
+      Array.from(listeners.values()).some(listener => listener.blockingAllowed)
+    );
+
+    this.needTracing =
+      this.listeners.onResponseStarted.size ||
+      this.listeners.onErrorOccurred.size ||
+      this.listeners.onCompleted.size ||
+      haveBlocking;
+
+    let needExamine =
+      this.needTracing ||
+      this.listeners.onHeadersReceived.size ||
+      this.listeners.onAuthRequired.size ||
+      this.dnrActive;
+
+    if (needExamine && !this.examineInitialized) {
+      this.examineInitialized = true;
+      Services.obs.addObserver(this, "http-on-examine-response");
+      Services.obs.addObserver(this, "http-on-examine-cached-response");
+      Services.obs.addObserver(this, "http-on-examine-merged-response");
+    } else if (!needExamine && this.examineInitialized) {
+      this.examineInitialized = false;
+      Services.obs.removeObserver(this, "http-on-examine-response");
+      Services.obs.removeObserver(this, "http-on-examine-cached-response");
+      Services.obs.removeObserver(this, "http-on-examine-merged-response");
+    }
+
+    // If we have any listeners, we need the channelsink so the channelwrapper is
+    // updated properly. Otherwise events for channels that are redirected will not
+    // happen correctly.  If we have no listeners, shut it down.
+    this.hasRedirects = this.listeners.onBeforeRedirect.size > 0;
+    let needRedirect =
+      this.hasRedirects || needExamine || needOpening || needBeforeConnect;
+    if (needRedirect && !this.redirectInitialized) {
+      this.redirectInitialized = true;
+      ChannelEventSink.register();
+    } else if (!needRedirect && this.redirectInitialized) {
+      this.redirectInitialized = false;
+      ChannelEventSink.unregister();
+    }
+
+    let needActivity = this.listeners.onErrorOccurred.size;
+    if (needActivity && !this.activityInitialized) {
+      this.activityInitialized = true;
+      this.activityDistributor.addObserver(this);
+    } else if (!needActivity && this.activityInitialized) {
+      this.activityInitialized = false;
+      this.activityDistributor.removeObserver(this);
+    }
+  },
+
+  addListener(kind, callback, opts) {
+    this.listeners[kind].set(callback, opts);
+    this.addOrRemove();
+  },
+
+  removeListener(kind, callback) {
+    this.listeners[kind].delete(callback);
+    this.addOrRemove();
+  },
+
+  setDNRHandlingEnabled(dnrActive) {
+    this.dnrActive = dnrActive;
+    this.addOrRemove();
+  },
+
+  observe(subject, topic, data) {
+    let channel = this.getWrapper(subject);
+    switch (topic) {
+      case "http-on-modify-request":
+        this.runChannelListener(channel, "onBeforeRequest");
+        break;
+      case "http-on-before-connect":
+        this.runChannelListener(channel, "onBeforeSendHeaders");
+        break;
+      case "http-on-examine-cached-response":
+      case "http-on-examine-merged-response":
+        channel.fromCache = true;
+      // falls through
+      case "http-on-examine-response":
+        this.examine(channel, topic, data);
+        break;
+    }
+  },
+
+  // We map activity values with tentative error names, e.g. "STATUS_RESOLVING" => "NS_ERROR_NET_ON_RESOLVING".
+  get activityErrorsMap() {
+    let prefix = /^(?:ACTIVITY_SUBTYPE_|STATUS_)/;
+    let map = new Map();
+    for (let iface of [nsIHttpActivityObserver, nsISocketTransport]) {
+      for (let c of Object.keys(iface).filter(name => prefix.test(name))) {
+        map.set(iface[c], c.replace(prefix, "NS_ERROR_NET_ON_"));
+      }
+    }
+    delete this.activityErrorsMap;
+    this.activityErrorsMap = map;
+    return this.activityErrorsMap;
+  },
+  GOOD_LAST_ACTIVITY: nsIHttpActivityObserver.ACTIVITY_SUBTYPE_RESPONSE_HEADER,
+  observeActivity(
+    nativeChannel,
+    activityType,
+    activitySubtype /* , aTimestamp, aExtraSizeData, aExtraStringData */
+  ) {
+    // Sometimes we get a NullHttpChannel, which implements
+    // nsIHttpChannel but not nsIChannel.
+    if (!(nativeChannel instanceof Ci.nsIChannel)) {
+      return;
+    }
+    let channel = this.getWrapper(nativeChannel);
+
+    let lastActivity = channel.lastActivity || 0;
+    if (
+      activitySubtype ===
+        nsIHttpActivityObserver.ACTIVITY_SUBTYPE_RESPONSE_COMPLETE &&
+      lastActivity &&
+      lastActivity !== this.GOOD_LAST_ACTIVITY
+    ) {
+      // Since the channel's security info is assigned in onStartRequest and
+      // errorCheck is called in ChannelWrapper::onStartRequest, we should check
+      // the errorString after onStartRequest to make sure errors have a chance
+      // to be processed before we fall back to a generic error string.
+      channel.addEventListener(
+        "start",
+        () => {
+          if (!channel.errorString) {
+            this.runChannelListener(channel, "onErrorOccurred", {
+              error:
+                this.activityErrorsMap.get(lastActivity) ||
+                `NS_ERROR_NET_UNKNOWN_${lastActivity}`,
+            });
+          }
+        },
+        { once: true }
+      );
+    } else if (
+      lastActivity !== this.GOOD_LAST_ACTIVITY &&
+      lastActivity !==
+        nsIHttpActivityObserver.ACTIVITY_SUBTYPE_TRANSACTION_CLOSE
+    ) {
+      channel.lastActivity = activitySubtype;
+    }
+  },
+
+  getRequestData(channel, extraData) {
+    let originAttributes = channel.loadInfo?.originAttributes;
+    let cos = channel.channel.QueryInterface(Ci.nsIClassOfService);
+
+    let data = {
+      requestId: String(channel.id),
+      url: channel.finalURL,
+      method: channel.method,
+      type: channel.type,
+      fromCache: channel.fromCache,
+      incognito: originAttributes?.privateBrowsingId > 0,
+      thirdParty: channel.thirdParty,
+
+      originUrl: channel.originURL || undefined,
+      documentUrl: channel.documentURL || undefined,
+
+      tabId: this.getBrowserData(channel).tabId,
+      frameId: channel.frameId,
+      parentFrameId: channel.parentFrameId,
+
+      frameAncestors: channel.frameAncestors || undefined,
+
+      ip: channel.remoteAddress,
+
+      proxyInfo: channel.proxyInfo,
+
+      serialize: serializeRequestData,
+      requestSize: channel.requestSize,
+      responseSize: channel.responseSize,
+      urlClassification: channel.urlClassification,
+
+      // Figure out if this is an urgent request that shouldn't be batched.
+      urgentSend: (cos.classFlags & URGENT_CLASSES) > 0,
+    };
+
+    if (originAttributes) {
+      data.cookieStoreId =
+        lazy.getCookieStoreIdForOriginAttributes(originAttributes);
+    }
+
+    return Object.assign(data, extraData);
+  },
+
+  handleEvent(event) {
+    let channel = event.currentTarget;
+    switch (event.type) {
+      case "error":
+        this.runChannelListener(channel, "onErrorOccurred", {
+          error: channel.errorString,
+        });
+        break;
+      case "start":
+        this.runChannelListener(channel, "onResponseStarted");
+        break;
+      case "stop":
+        this.runChannelListener(channel, "onCompleted");
+        break;
+    }
+  },
+
+  STATUS_TYPES: new Set([
+    "onHeadersReceived",
+    "onAuthRequired",
+    "onBeforeRedirect",
+    "onResponseStarted",
+    "onCompleted",
+  ]),
+  FILTER_TYPES: new Set([
+    "onBeforeRequest",
+    "onBeforeSendHeaders",
+    "onSendHeaders",
+    "onHeadersReceived",
+    "onAuthRequired",
+    "onBeforeRedirect",
+  ]),
+
+  getBrowserData(wrapper) {
+    let browserData = wrapper._browserData;
+    if (!browserData) {
+      if (wrapper.browserElement) {
+        browserData = lazy.tabTracker.getBrowserData(wrapper.browserElement);
+      } else {
+        browserData = { tabId: -1, windowId: -1 };
+      }
+      wrapper._browserData = browserData;
+    }
+    return browserData;
+  },
+
+  runChannelListener(channel, kind, extraData = null) {
+    let handlerResults = [];
+    let requestHeaders;
+    let responseHeaders;
+
+    try {
+      if (kind !== "onErrorOccurred" && channel.errorString) {
+        return;
+      }
+      if (this.dnrActive) {
+        // DNR may modify (but not cancel) the request at this stage.
+        lazy.ExtensionDNR.beforeWebRequestEvent(channel, kind);
+      }
+
+      let registerFilter = this.FILTER_TYPES.has(kind);
+      let commonData = null;
+      let requestBody;
+      this.listeners[kind].forEach((opts, callback) => {
+        if (opts.filter.tabId !== null || opts.filter.windowId !== null) {
+          const { tabId, windowId } = this.getBrowserData(channel);
+          if (
+            (opts.filter.tabId !== null && tabId != opts.filter.tabId) ||
+            (opts.filter.windowId !== null && windowId != opts.filter.windowId)
+          ) {
+            return;
+          }
+        }
+        if (!channel.matches(opts.filter, opts.policy, extraData)) {
+          return;
+        }
+
+        let extension = opts.policy?.extension;
+        // TODO: Move this logic to ChannelWrapper::matches, see bug 1699481
+        if (
+          extension?.userContextIsolation &&
+          !extension.canAccessContainer(
+            channel.loadInfo?.originAttributes.userContextId
+          )
+        ) {
+          return;
+        }
+
+        if (!commonData) {
+          commonData = this.getRequestData(channel, extraData);
+          if (this.STATUS_TYPES.has(kind)) {
+            commonData.statusCode = channel.statusCode;
+            commonData.statusLine = channel.statusLine;
+          }
+        }
+        let data = Object.create(commonData);
+        data.urgentSend = data.urgentSend && opts.blocking;
+
+        if (registerFilter && opts.blocking && opts.policy) {
+          data.registerTraceableChannel = (policy, remoteTab) => {
+            // `channel` is a ChannelWrapper, which contains the actual
+            // underlying nsIChannel in `channel.channel`.  For startup events
+            // that are held until the extension background page is started,
+            // it is possible that the underlying channel can be closed and
+            // cleaned up between the time the event occurred and the time
+            // we reach this code.
+            if (channel.channel) {
+              channel.registerTraceableChannel(policy, remoteTab);
+            }
+          };
+        }
+
+        if (opts.requestHeaders) {
+          requestHeaders = requestHeaders || new RequestHeaderChanger(channel);
+          data.requestHeaders = requestHeaders.toArray();
+        }
+
+        if (opts.responseHeaders) {
+          try {
+            responseHeaders =
+              responseHeaders || new ResponseHeaderChanger(channel);
+            data.responseHeaders = responseHeaders.toArray();
+          } catch (e) {
+            /* headers may not be available on some redirects */
+          }
+        }
+
+        if (opts.requestBody && channel.canModify) {
+          requestBody =
+            requestBody ||
+            lazy.WebRequestUpload.createRequestBody(channel.channel);
+          data.requestBody = requestBody;
+        }
+
+        try {
+          let result = callback(data);
+
+          // isProxy is set during onAuth if the auth request is for a proxy.
+          // We allow handling proxy auth regardless of canModify.
+          if (
+            (channel.canModify || data.isProxy) &&
+            typeof result === "object" &&
+            opts.blocking
+          ) {
+            handlerResults.push({ opts, result });
+          }
+        } catch (e) {
+          Cu.reportError(e);
+        }
+      });
+    } catch (e) {
+      Cu.reportError(e);
+    }
+
+    if (this.dnrActive && lazy.ExtensionDNR.handleRequest(channel, kind)) {
+      return;
+    }
+
+    return this.applyChanges(
+      kind,
+      channel,
+      handlerResults,
+      requestHeaders,
+      responseHeaders
+    );
+  },
+
+  async applyChanges(
+    kind,
+    channel,
+    handlerResults,
+    requestHeaders,
+    responseHeaders
+  ) {
+    const { finalURL, id: chanId } = channel;
+    let shouldResume = !channel.suspended;
+    // NOTE: if a request has been suspended before the GeckoProfiler
+    // has been activated and then resumed while the GeckoProfiler is active
+    // and collecting data, the resulting "Extension Suspend" marker will be
+    // recorded with an empty marker text (and so without url, chan id and
+    // the supenders addon ids).
+    let markerText = "";
+    if (Services.profiler?.IsActive()) {
+      const suspenders = handlerResults
+        .filter(({ result }) => isThenable(result))
+        .map(({ opts }) => opts.addonId)
+        .join(", ");
+      markerText = `${kind} ${finalURL} by ${suspenders} (chanId: ${chanId})`;
+    }
+    try {
+      for (let { opts, result } of handlerResults) {
+        if (isThenable(result)) {
+          channel.suspend(markerText);
+          try {
+            result = await result;
+          } catch (e) {
+            let error;
+
+            if (e instanceof Error) {
+              error = e;
+            } else if (typeof e === "object" && e.message) {
+              error = new Error(e.message, e.fileName, e.lineNumber);
+            }
+
+            Cu.reportError(error);
+            continue;
+          }
+          if (!result || typeof result !== "object") {
+            continue;
+          }
+        }
+
+        if (
+          kind === "onAuthRequired" &&
+          result.authCredentials &&
+          channel.authPromptCallback
+        ) {
+          channel.authPromptCallback(result.authCredentials);
+        }
+
+        // We allow proxy auth to cancel or handle authCredentials regardless of
+        // canModify, but ensure we do nothing else.
+        if (!channel.canModify) {
+          continue;
+        }
+
+        if (result.cancel) {
+          channel.resume();
+          channel.cancel(
+            Cr.NS_ERROR_ABORT,
+            Ci.nsILoadInfo.BLOCKING_REASON_EXTENSION_WEBREQUEST
+          );
+          ChromeUtils.addProfilerMarker(
+            "Extension Canceled",
+            { category: "Network" },
+            `${kind} ${finalURL} canceled by ${opts.addonId} (chanId: ${chanId})`
+          );
+          if (opts.policy) {
+            let properties = channel.channel.QueryInterface(
+              Ci.nsIWritablePropertyBag
+            );
+            properties.setProperty("cancelledByExtension", opts.policy.id);
+          }
+          return;
+        }
+
+        if (result.redirectUrl) {
+          try {
+            const { redirectUrl } = result;
+            channel.resume();
+            const redirectUri = Services.io.newURI(redirectUrl);
+            verifyRedirect(channel, redirectUri, finalURL, opts.addonId);
+            channel.redirectTo(redirectUri);
+            ChromeUtils.addProfilerMarker(
+              "Extension Redirected",
+              { category: "Network" },
+              `${kind} ${finalURL} redirected to ${redirectUrl} by ${opts.addonId} (chanId: ${chanId})`
+            );
+            if (opts.policy) {
+              let properties = channel.channel.QueryInterface(
+                Ci.nsIWritablePropertyBag
+              );
+              properties.setProperty("redirectedByExtension", opts.policy.id);
+            }
+
+            // Web Extensions using the WebRequest API are allowed
+            // to redirect a channel to a data: URI, hence we mark
+            // the channel to let the redirect blocker know. Please
+            // note that this marking needs to happen after the
+            // channel.redirectTo is called because the channel's
+            // RedirectTo() implementation explicitly drops the flag
+            // to avoid additional redirects not caused by the
+            // Web Extension.
+            channel.loadInfo.allowInsecureRedirectToDataURI = true;
+
+            // To pass CORS checks, we pretend the current request's
+            // response allows the triggering origin to access.
+            let origin = channel.getRequestHeader("Origin");
+            if (origin) {
+              channel.setResponseHeader("Access-Control-Allow-Origin", origin);
+              channel.setResponseHeader(
+                "Access-Control-Allow-Credentials",
+                "true"
+              );
+
+              // Compute an arbitrary 'Access-Control-Allow-Headers'
+              // for the  internal Redirect
+
+              let allowHeaders = channel
+                .getRequestHeaders()
+                .map(header => header.name)
+                .join();
+              channel.setResponseHeader(
+                "Access-Control-Allow-Headers",
+                allowHeaders
+              );
+
+              channel.setResponseHeader(
+                "Access-Control-Allow-Methods",
+                channel.method
+              );
+            }
+
+            return;
+          } catch (e) {
+            Cu.reportError(e);
+          }
+        }
+
+        if (result.upgradeToSecure && kind === "onBeforeRequest") {
+          try {
+            channel.upgradeToSecure();
+          } catch (e) {
+            Cu.reportError(e);
+          }
+        }
+
+        if (opts.requestHeaders && result.requestHeaders && requestHeaders) {
+          requestHeaders.applyChanges(result.requestHeaders, opts);
+        }
+
+        if (opts.responseHeaders && result.responseHeaders && responseHeaders) {
+          responseHeaders.applyChanges(result.responseHeaders, opts);
+        }
+      }
+
+      // If a listener did not cancel the request or provide credentials, we
+      // forward the auth request to the base handler.
+      if (kind === "onAuthRequired" && channel.authPromptForward) {
+        channel.authPromptForward();
+      }
+
+      if (kind === "onBeforeSendHeaders" && this.listeners.onSendHeaders.size) {
+        this.runChannelListener(channel, "onSendHeaders");
+      } else if (kind !== "onErrorOccurred") {
+        channel.errorCheck();
+      }
+    } catch (e) {
+      Cu.reportError(e);
+    }
+
+    // Only resume the channel if it was suspended by this call.
+    if (shouldResume) {
+      channel.resume();
+    }
+  },
+
+  shouldHookListener(listener, channel, extraData) {
+    if (listener.size == 0) {
+      return false;
+    }
+
+    for (let opts of listener.values()) {
+      if (channel.matches(opts.filter, opts.policy, extraData)) {
+        return true;
+      }
+    }
+    return false;
+  },
+
+  examine(channel, topic, data) {
+    if (this.listeners.onHeadersReceived.size || this.dnrActive) {
+      this.runChannelListener(channel, "onHeadersReceived");
+    }
+
+    if (
+      !channel.hasAuthRequestor &&
+      this.shouldHookListener(this.listeners.onAuthRequired, channel, {
+        isProxy: true,
+      })
+    ) {
+      channel.channel.notificationCallbacks = new AuthRequestor(
+        channel.channel,
+        this
+      );
+      channel.hasAuthRequestor = true;
+    }
+  },
+
+  onChannelReplaced(oldChannel, newChannel) {
+    let channel = this.getWrapper(oldChannel);
+
+    // We want originalURI, this will provide a moz-ext rather than jar or file
+    // uri on redirects.
+    if (this.hasRedirects) {
+      this.runChannelListener(channel, "onBeforeRedirect", {
+        redirectUrl: newChannel.originalURI.spec,
+      });
+    }
+    channel.channel = newChannel;
+  },
+};
+
+function HttpEvent(internalEvent, options) {
+  this.internalEvent = internalEvent;
+  this.options = options;
+}
+
+HttpEvent.prototype = {
+  addListener(callback, filter = null, options = null, optionsObject = null) {
+    let opts = parseExtra(options, this.options, optionsObject);
+    opts.filter = parseFilter(filter);
+    HttpObserverManager.addListener(this.internalEvent, callback, opts);
+  },
+
+  removeListener(callback) {
+    HttpObserverManager.removeListener(this.internalEvent, callback);
+  },
+};
+
+var onBeforeRequest = new HttpEvent("onBeforeRequest", [
+  "blocking",
+  "requestBody",
+]);
+var onBeforeSendHeaders = new HttpEvent("onBeforeSendHeaders", [
+  "requestHeaders",
+  "blocking",
+]);
+var onSendHeaders = new HttpEvent("onSendHeaders", ["requestHeaders"]);
+var onHeadersReceived = new HttpEvent("onHeadersReceived", [
+  "blocking",
+  "responseHeaders",
+]);
+var onAuthRequired = new HttpEvent("onAuthRequired", [
+  "blocking",
+  "responseHeaders",
+]);
+var onBeforeRedirect = new HttpEvent("onBeforeRedirect", ["responseHeaders"]);
+var onResponseStarted = new HttpEvent("onResponseStarted", ["responseHeaders"]);
+var onCompleted = new HttpEvent("onCompleted", ["responseHeaders"]);
+var onErrorOccurred = new HttpEvent("onErrorOccurred");
+
+export var WebRequest = {
+  setDNRHandlingEnabled: dnrActive => {
+    HttpObserverManager.setDNRHandlingEnabled(dnrActive);
+  },
+  getTabIdForChannelWrapper: channel => {
+    // Warning: This method should only be called after the initialization of
+    // ExtensionParent.apiManager.global. Generally, this means that this method
+    // should only be used by implementations of extension API methods (which
+    // themselves are loaded in ExtensionParent.apiManager.global and therefore
+    // imply the initialization of ExtensionParent.apiManager.global).
+    return HttpObserverManager.getBrowserData(channel).tabId;
+  },
+
+  onBeforeRequest,
+  onBeforeSendHeaders,
+  onSendHeaders,
+  onHeadersReceived,
+  onAuthRequired,
+  onBeforeRedirect,
+  onResponseStarted,
+  onCompleted,
+  onErrorOccurred,
+
+  getSecurityInfo: details => {
+    let channel = ChannelWrapper.getRegisteredChannel(
+      details.id,
+      details.policy,
+      details.remoteTab
+    );
+    if (channel) {
+      return lazy.SecurityInfo.getSecurityInfo(
+        channel.channel,
+        details.options
+      );
+    }
+  },
+};
diff --git a/toolkit/components/extensions/webrequest/WebRequestService.cpp b/toolkit/components/extensions/webrequest/WebRequestService.cpp
new file mode 100644
index 0000000000..7ec2433ac5
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/WebRequestService.cpp
@@ -0,0 +1,55 @@
+/* -*- 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 "WebRequestService.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ClearOnShutdown.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::extensions;
+
+static StaticRefPtr<WebRequestService> sWebRequestService;
+
+/* static */ WebRequestService& WebRequestService::GetSingleton() {
+  if (!sWebRequestService) {
+    sWebRequestService = new WebRequestService();
+    ClearOnShutdown(&sWebRequestService);
+  }
+  return *sWebRequestService;
+}
+
+UniquePtr<WebRequestChannelEntry> WebRequestService::RegisterChannel(
+    ChannelWrapper* aChannel) {
+  UniquePtr<ChannelEntry> entry(new ChannelEntry(aChannel));
+
+  mChannelEntries.WithEntryHandle(entry->mChannelId, [&](auto&& key) {
+    MOZ_DIAGNOSTIC_ASSERT(!key);
+    key.Insert(entry.get());
+  });
+
+  return entry;
+}
+
+already_AddRefed<nsITraceableChannel> WebRequestService::GetTraceableChannel(
+    uint64_t aChannelId, nsAtom* aAddonId, ContentParent* aContentParent) {
+  if (auto entry = mChannelEntries.Get(aChannelId)) {
+    if (entry->mChannel) {
+      return entry->mChannel->GetTraceableChannel(aAddonId, aContentParent);
+    }
+  }
+  return nullptr;
+}
+
+WebRequestChannelEntry::WebRequestChannelEntry(ChannelWrapper* aChannel)
+    : mChannelId(aChannel->Id()), mChannel(aChannel) {}
+
+WebRequestChannelEntry::~WebRequestChannelEntry() {
+  if (sWebRequestService) {
+    sWebRequestService->mChannelEntries.Remove(mChannelId);
+  }
+}
diff --git a/toolkit/components/extensions/webrequest/WebRequestService.h b/toolkit/components/extensions/webrequest/WebRequestService.h
new file mode 100644
index 0000000000..b963586169
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/WebRequestService.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_WebRequestService_h
+#define mozilla_WebRequestService_h
+
+#include "mozilla/LinkedList.h"
+#include "mozilla/UniquePtr.h"
+
+#include "mozilla/extensions/ChannelWrapper.h"
+#include "mozilla/extensions/WebExtensionPolicy.h"
+
+#include "nsHashKeys.h"
+#include "nsTHashMap.h"
+
+class nsAtom;
+class nsIRemoteTab;
+class nsITraceableChannel;
+
+namespace mozilla {
+namespace dom {
+class BrowserParent;
+class ContentParent;
+}  // namespace dom
+
+namespace extensions {
+
+class ChannelWrapper;
+
+class WebRequestChannelEntry final {
+ public:
+  ~WebRequestChannelEntry();
+
+ private:
+  friend class WebRequestService;
+
+  explicit WebRequestChannelEntry(ChannelWrapper* aChannel);
+
+  uint64_t mChannelId;
+  WeakPtr<ChannelWrapper> mChannel;
+};
+
+class WebRequestService final {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(WebRequestService)
+
+  WebRequestService() = default;
+
+  static already_AddRefed<WebRequestService> GetInstance() {
+    return do_AddRef(&GetSingleton());
+  }
+
+  static WebRequestService& GetSingleton();
+
+  using ChannelEntry = WebRequestChannelEntry;
+
+  UniquePtr<ChannelEntry> RegisterChannel(ChannelWrapper* aChannel);
+
+  void UnregisterTraceableChannel(uint64_t aChannelId);
+
+  already_AddRefed<nsITraceableChannel> GetTraceableChannel(
+      uint64_t aChannelId, nsAtom* aAddonId,
+      dom::ContentParent* aContentParent);
+
+ private:
+  ~WebRequestService() = default;
+
+  friend ChannelEntry;
+
+  nsTHashMap<nsUint64HashKey, ChannelEntry*> mChannelEntries;
+};
+
+}  // namespace extensions
+}  // namespace mozilla
+
+#endif  // mozilla_WebRequestService_h
diff --git a/toolkit/components/extensions/webrequest/WebRequestUpload.sys.mjs b/toolkit/components/extensions/webrequest/WebRequestUpload.sys.mjs
new file mode 100644
index 0000000000..09f2e25a7e
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/WebRequestUpload.sys.mjs
@@ -0,0 +1,560 @@
+/* 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 { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+import { ExtensionUtils } from "resource://gre/modules/ExtensionUtils.sys.mjs";
+
+const { DefaultMap } = ExtensionUtils;
+
+const lazy = {};
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "mimeHeader",
+  "@mozilla.org/network/mime-hdrparam;1",
+  "nsIMIMEHeaderParam"
+);
+
+const BinaryInputStream = Components.Constructor(
+  "@mozilla.org/binaryinputstream;1",
+  "nsIBinaryInputStream",
+  "setInputStream"
+);
+const ConverterInputStream = Components.Constructor(
+  "@mozilla.org/intl/converter-input-stream;1",
+  "nsIConverterInputStream",
+  "init"
+);
+
+export var WebRequestUpload;
+
+/**
+ * Parses the given raw header block, and stores the value of each
+ * lower-cased header name in the resulting map.
+ */
+class Headers extends Map {
+  constructor(headerText) {
+    super();
+
+    if (headerText) {
+      this.parseHeaders(headerText);
+    }
+  }
+
+  parseHeaders(headerText) {
+    let lines = headerText.split("\r\n");
+
+    let lastHeader;
+    for (let line of lines) {
+      // The first empty line indicates the end of the header block.
+      if (line === "") {
+        return;
+      }
+
+      // Lines starting with whitespace are appended to the previous
+      // header.
+      if (/^\s/.test(line)) {
+        if (lastHeader) {
+          let val = this.get(lastHeader);
+          this.set(lastHeader, `${val}\r\n${line}`);
+        }
+        continue;
+      }
+
+      let match = /^(.*?)\s*:\s+(.*)/.exec(line);
+      if (match) {
+        lastHeader = match[1].toLowerCase();
+        this.set(lastHeader, match[2]);
+      }
+    }
+  }
+
+  /**
+   * If the given header exists, and contains the given parameter,
+   * returns the value of that parameter.
+   *
+   * @param {string} name
+   *        The lower-cased header name.
+   * @param {string} paramName
+   *        The name of the parameter to retrieve, or empty to retrieve
+   *        the first (possibly unnamed) parameter.
+   * @returns {string | null}
+   */
+  getParam(name, paramName) {
+    return Headers.getParam(this.get(name), paramName);
+  }
+
+  /**
+   * If the given header value is non-null, and contains the given
+   * parameter, returns the value of that parameter.
+   *
+   * @param {string | null} header
+   *        The text of the header from which to retrieve the param.
+   * @param {string} paramName
+   *        The name of the parameter to retrieve, or empty to retrieve
+   *        the first (possibly unnamed) parameter.
+   * @returns {string | null}
+   */
+  static getParam(header, paramName) {
+    if (header) {
+      // The service expects this to be a raw byte string, so convert to
+      // UTF-8.
+      let bytes = new TextEncoder().encode(header);
+      let binHeader = String.fromCharCode(...bytes);
+
+      return lazy.mimeHeader.getParameterHTTP(
+        binHeader,
+        paramName,
+        null,
+        false,
+        {}
+      );
+    }
+
+    return null;
+  }
+}
+
+/**
+ * Creates a new Object with a corresponding property for every
+ * key-value pair in the given Map.
+ *
+ * @param {Map} map
+ *        The map to convert.
+ * @returns {object}
+ */
+function mapToObject(map) {
+  let result = {};
+  for (let [key, value] of map) {
+    result[key] = value;
+  }
+  return result;
+}
+
+/**
+ * Rewinds the given seekable input stream to its beginning, and catches
+ * any resulting errors.
+ *
+ * @param {nsISeekableStream} stream
+ *        The stream to rewind.
+ */
+function rewind(stream) {
+  // Do this outside the try-catch so that we throw if the stream is not
+  // actually seekable.
+  stream.QueryInterface(Ci.nsISeekableStream);
+
+  try {
+    stream.seek(0, 0);
+  } catch (e) {
+    // It might be already closed, e.g. because of a previous error.
+    Cu.reportError(e);
+  }
+}
+
+/**
+ * Iterates over all of the sub-streams that make up the given stream,
+ * or yields the stream itself if it is not a multi-part stream.
+ *
+ * @param {nsIIMultiplexInputStream|nsIStreamBufferAccess<nsIMultiplexInputStream>|nsIInputStream} outerStream
+ *        The outer stream over which to iterate.
+ */
+function* getStreams(outerStream) {
+  // If this is a multi-part stream, we need to iterate over its sub-streams,
+  // rather than treating it as a simple input stream. Since it may be wrapped
+  // in a buffered input stream, unwrap it before we do any checks.
+  let unbuffered = outerStream;
+  if (outerStream instanceof Ci.nsIStreamBufferAccess) {
+    unbuffered = outerStream.unbufferedStream;
+  }
+
+  if (unbuffered instanceof Ci.nsIMultiplexInputStream) {
+    let count = unbuffered.count;
+    for (let i = 0; i < count; i++) {
+      yield unbuffered.getStream(i);
+    }
+  } else {
+    yield outerStream;
+  }
+}
+
+/**
+ * Parses the form data of the given stream as either multipart/form-data or
+ * x-www-form-urlencoded, and returns a map of its fields.
+ *
+ * @param {nsIInputStream} stream
+ *        The input stream from which to parse the form data.
+ * @param {nsIHttpChannel} channel
+ *        The channel to which the stream belongs.
+ * @param {boolean} [lenient = false]
+ *        If true, the operation will succeed even if there are UTF-8
+ *        decoding errors.
+ *
+ * @returns {Map<string, Array<string>> | null}
+ */
+function parseFormData(stream, channel, lenient = false) {
+  const BUFFER_SIZE = 8192;
+
+  let touchedStreams = new Set();
+  let converterStreams = [];
+
+  /**
+   * Creates a converter input stream from the given raw input stream,
+   * and adds it to the list of streams to be rewound at the end of
+   * parsing.
+   *
+   * Returns null if the given raw stream cannot be rewound.
+   *
+   * @param {nsIInputStream} stream
+   *        The base stream from which to create a converter.
+   * @returns {ConverterInputStream | null}
+   */
+  function createTextStream(stream) {
+    if (!(stream instanceof Ci.nsISeekableStream)) {
+      return null;
+    }
+
+    touchedStreams.add(stream);
+    let converterStream = ConverterInputStream(
+      stream,
+      "UTF-8",
+      0,
+      lenient ? Ci.nsIConverterInputStream.DEFAULT_REPLACEMENT_CHARACTER : 0
+    );
+    converterStreams.push(converterStream);
+    return converterStream;
+  }
+
+  /**
+   * Reads a string of no more than the given length from the given text
+   * stream.
+   *
+   * @param {ConverterInputStream} stream
+   *        The stream to read.
+   * @param {integer} [length = BUFFER_SIZE]
+   *        The maximum length of data to read.
+   * @returns {string}
+   */
+  function readString(stream, length = BUFFER_SIZE) {
+    let data = {};
+    stream.readString(length, data);
+    return data.value;
+  }
+
+  /**
+   * Iterates over all of the sub-streams of the given (possibly multi-part)
+   * input stream, and yields a ConverterInputStream for each
+   * nsIStringInputStream among them.
+   *
+   * @param {nsIInputStream|nsIMultiplexInputStream} outerStream
+   *        The multi-part stream over which to iterate.
+   */
+  function* getTextStreams(outerStream) {
+    for (let stream of getStreams(outerStream)) {
+      if (stream instanceof Ci.nsIStringInputStream) {
+        touchedStreams.add(outerStream);
+        yield createTextStream(stream);
+      }
+    }
+  }
+
+  /**
+   * Iterates over all of the string streams of the given (possibly
+   * multi-part) input stream, and yields all of the available data in each as
+   * chunked strings, each no more than BUFFER_SIZE in length.
+   *
+   * @param {nsIInputStream|nsIMultiplexInputStream} outerStream
+   *        The multi-part stream over which to iterate.
+   */
+  function* readAllStrings(outerStream) {
+    for (let textStream of getTextStreams(outerStream)) {
+      let str;
+      while ((str = readString(textStream))) {
+        yield str;
+      }
+    }
+  }
+
+  /**
+   * Iterates over the text contents of all of the string streams in the given
+   * (possibly multi-part) input stream, splits them at occurrences of the
+   * given boundary string, and yields each part.
+   *
+   * @param {nsIInputStream|nsIMultiplexInputStream} stream
+   *        The multi-part stream over which to iterate.
+   * @param {string} boundary
+   *        The boundary at which to split the parts.
+   * @param {string} [tail = ""]
+   *        Any initial data to prepend to the start of the stream data.
+   */
+  function* getParts(stream, boundary, tail = "") {
+    for (let chunk of readAllStrings(stream)) {
+      chunk = tail + chunk;
+
+      let parts = chunk.split(boundary);
+      tail = parts.pop();
+
+      yield* parts;
+    }
+
+    if (tail) {
+      yield tail;
+    }
+  }
+
+  /**
+   * Parses the given stream as multipart/form-data and returns a map of its fields.
+   *
+   * @param {nsIMultiplexInputStream|nsIInputStream} stream
+   *        The (possibly multi-part) stream to parse.
+   * @param {string} boundary
+   *        The boundary at which to split the parts.
+   * @returns {Map<string, Array<string>>}
+   */
+  function parseMultiPart(stream, boundary) {
+    let formData = new DefaultMap(() => []);
+
+    for (let part of getParts(stream, boundary, "\r\n")) {
+      if (part === "") {
+        // The first part will always be empty.
+        continue;
+      }
+      if (part === "--\r\n") {
+        // This indicates the end of the stream.
+        break;
+      }
+
+      let end = part.indexOf("\r\n\r\n");
+
+      // All valid parts must begin with \r\n, and we can't process form
+      // fields without any header block.
+      if (!part.startsWith("\r\n") || end <= 0) {
+        throw new Error("Invalid MIME stream");
+      }
+
+      let content = part.slice(end + 4);
+      let headerText = part.slice(2, end);
+      let headers = new Headers(headerText);
+
+      let name = headers.getParam("content-disposition", "name");
+      if (
+        !name ||
+        headers.getParam("content-disposition", "") !== "form-data"
+      ) {
+        throw new Error(
+          "Invalid MIME stream: No valid Content-Disposition header"
+        );
+      }
+
+      // Decode the percent-escapes in the name. Unlike with decodeURIComponent,
+      // partial percent-escapes are passed through as is rather than throwing
+      // exceptions.
+      name = name.replace(/(%[0-9A-Fa-f]{2})+/g, match => {
+        const bytes = new Uint8Array(match.length / 3);
+        for (let i = 0; i < match.length / 3; i++) {
+          bytes[i] = parseInt(match.substring(i * 3 + 1, (i + 1) * 3), 16);
+        }
+        return new TextDecoder("utf-8").decode(bytes);
+      });
+
+      if (headers.has("content-type")) {
+        // For file upload fields, we return the filename, rather than the
+        // file data. We're following Chrome in not percent-decoding the
+        // filename.
+        let filename = headers.getParam("content-disposition", "filename");
+        content = filename || "";
+      }
+      formData.get(name).push(content);
+    }
+
+    return formData;
+  }
+
+  /**
+   * Parses the given stream as x-www-form-urlencoded, and returns a map of its fields.
+   *
+   * @param {nsIInputStream} stream
+   *        The stream to parse.
+   * @returns {Map<string, Array<string>>}
+   */
+  function parseUrlEncoded(stream) {
+    let formData = new DefaultMap(() => []);
+
+    for (let part of getParts(stream, "&")) {
+      let [name, value] = part
+        .replace(/\+/g, " ")
+        .split("=")
+        .map(decodeURIComponent);
+      formData.get(name).push(value);
+    }
+
+    return formData;
+  }
+
+  try {
+    if (stream instanceof Ci.nsIMIMEInputStream && stream.data) {
+      stream = stream.data;
+    }
+
+    channel.QueryInterface(Ci.nsIHttpChannel);
+    let contentType = channel.getRequestHeader("Content-Type");
+
+    switch (Headers.getParam(contentType, "")) {
+      case "multipart/form-data":
+        let boundary = Headers.getParam(contentType, "boundary");
+        return parseMultiPart(stream, `\r\n--${boundary}`);
+
+      case "application/x-www-form-urlencoded":
+        return parseUrlEncoded(stream);
+    }
+  } finally {
+    for (let stream of touchedStreams) {
+      rewind(stream);
+    }
+    for (let converterStream of converterStreams) {
+      // Release the reference to the underlying input stream, to prevent the
+      // destructor of nsConverterInputStream from closing the stream, which
+      // would cause uploads to break.
+      converterStream.init(null, null, 0, 0);
+    }
+  }
+
+  return null;
+}
+
+/**
+ * Parses the form data of the given stream as either multipart/form-data or
+ * x-www-form-urlencoded, and returns a map of its fields.
+ *
+ * Returns null if the stream is not seekable.
+ *
+ * @param {nsIMultiplexInputStream|nsIInputStream} stream
+ *        The (possibly multi-part) stream from which to create the form data.
+ * @param {nsIChannel} channel
+ *        The channel to which the stream belongs.
+ * @param {boolean} [lenient = false]
+ *        If true, the operation will succeed even if there are UTF-8
+ *        decoding errors.
+ * @returns {Map<string, Array<string>> | null}
+ */
+function createFormData(stream, channel, lenient) {
+  if (!(stream instanceof Ci.nsISeekableStream)) {
+    return null;
+  }
+
+  try {
+    let formData = parseFormData(stream, channel, lenient);
+    if (formData) {
+      return mapToObject(formData);
+    }
+  } catch (e) {
+    Cu.reportError(e);
+  } finally {
+    rewind(stream);
+  }
+  return null;
+}
+
+/**
+ * Iterates over all of the sub-streams of the given (possibly multi-part)
+ * input stream, and yields an object containing the data for each chunk, up
+ * to a total of `maxRead` bytes.
+ *
+ * @param {nsIMultiplexInputStream|nsIInputStream} outerStream
+ *        The stream for which to return data.
+ * @param {integer} [maxRead = WebRequestUpload.MAX_RAW_BYTES]
+ *        The maximum total bytes to read.
+ */
+function* getRawDataChunked(
+  outerStream,
+  maxRead = WebRequestUpload.MAX_RAW_BYTES
+) {
+  for (let stream of getStreams(outerStream)) {
+    // We need to inspect the stream to make sure it's not a file input
+    // stream. If it's wrapped in a buffered input stream, unwrap it first,
+    // so we can inspect the inner stream directly.
+    let unbuffered = stream;
+    if (stream instanceof Ci.nsIStreamBufferAccess) {
+      unbuffered = stream.unbufferedStream;
+    }
+
+    // For file fields, we return an object containing the full path of
+    // the file, rather than its data.
+    if (
+      unbuffered instanceof Ci.nsIFileInputStream ||
+      unbuffered instanceof Ci.mozIRemoteLazyInputStream
+    ) {
+      // But this is not actually supported yet.
+      yield { file: "<file>" };
+      continue;
+    }
+
+    try {
+      let binaryStream = BinaryInputStream(stream);
+      let available;
+      while ((available = binaryStream.available())) {
+        let buffer = new ArrayBuffer(Math.min(maxRead, available));
+        binaryStream.readArrayBuffer(buffer.byteLength, buffer);
+
+        maxRead -= buffer.byteLength;
+
+        let chunk = { bytes: buffer };
+
+        if (buffer.byteLength < available) {
+          chunk.truncated = true;
+          chunk.originalSize = available;
+        }
+
+        yield chunk;
+
+        if (maxRead <= 0) {
+          return;
+        }
+      }
+    } finally {
+      rewind(stream);
+    }
+  }
+}
+
+WebRequestUpload = {
+  createRequestBody(channel) {
+    if (!(channel instanceof Ci.nsIUploadChannel) || !channel.uploadStream) {
+      return null;
+    }
+
+    if (
+      channel instanceof Ci.nsIUploadChannel2 &&
+      channel.uploadStreamHasHeaders
+    ) {
+      return { error: "Upload streams with headers are unsupported" };
+    }
+
+    try {
+      let stream = channel.uploadStream;
+
+      let formData = createFormData(stream, channel);
+      if (formData) {
+        return { formData };
+      }
+
+      // If we failed to parse the stream as form data, return it as a
+      // sequence of raw data chunks, along with a leniently-parsed form
+      // data object, which ignores encoding errors.
+      return {
+        raw: Array.from(getRawDataChunked(stream)),
+        lenientFormData: createFormData(stream, channel, true),
+      };
+    } catch (e) {
+      Cu.reportError(e);
+      return { error: e.message || String(e) };
+    }
+  },
+};
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  WebRequestUpload,
+  "MAX_RAW_BYTES",
+  "webextensions.webRequest.requestBodyMaxRawBytes"
+);
diff --git a/toolkit/components/extensions/webrequest/components.conf b/toolkit/components/extensions/webrequest/components.conf
new file mode 100644
index 0000000000..9b1e6f86da
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/components.conf
@@ -0,0 +1,16 @@
+# -*- 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/.
+
+Classes = [
+    {
+        'cid': '{acb22042-2b6c-427b-b550-b9f407c6fff6}',
+        'contract_ids': ['@mozilla.org/extensions/web-navigation-content;1'],
+        'type': 'mozilla::extensions::WebNavigationContent',
+        'constructor': 'mozilla::extensions::WebNavigationContent::GetSingleton',
+        'headers': ['mozilla/extensions/WebNavigationContent.h'],
+        'categories': {'app-startup': 'WebNavigationContent'},
+    },
+]
diff --git a/toolkit/components/extensions/webrequest/moz.build b/toolkit/components/extensions/webrequest/moz.build
new file mode 100644
index 0000000000..935531d916
--- /dev/null
+++ b/toolkit/components/extensions/webrequest/moz.build
@@ -0,0 +1,60 @@
+# -*- 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/.
+
+EXTRA_JS_MODULES += [
+    "SecurityInfo.sys.mjs",
+    "WebRequest.sys.mjs",
+    "WebRequestUpload.sys.mjs",
+]
+
+UNIFIED_SOURCES += [
+    "ChannelWrapper.cpp",
+    "StreamFilter.cpp",
+    "StreamFilterChild.cpp",
+    "StreamFilterEvents.cpp",
+    "StreamFilterParent.cpp",
+    "WebNavigationContent.cpp",
+    "WebRequestService.cpp",
+]
+
+IPDL_SOURCES += [
+    "PStreamFilter.ipdl",
+]
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+EXPORTS.mozilla += [
+    "WebRequestService.h",
+]
+
+EXPORTS.mozilla.extensions += [
+    "ChannelWrapper.h",
+    "StreamFilter.h",
+    "StreamFilterBase.h",
+    "StreamFilterChild.h",
+    "StreamFilterEvents.h",
+    "StreamFilterParent.h",
+    "WebNavigationContent.h",
+]
+
+LOCAL_INCLUDES += [
+    "/caps",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+LOCAL_INCLUDES += [
+    # For nsHttpChannel.h
+    "/netwerk/base",
+    "/netwerk/protocol/http",
+]
+
+FINAL_LIBRARY = "xul"
+
+with Files("**"):
+    BUG_COMPONENT = ("WebExtensions", "Request Handling")