Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

193 files changed, 35397 insertions, 0 deletions

diff --git a/ipc/glue/AsyncBlockers.h b/ipc/glue/AsyncBlockers.h
new file mode 100644
index 0000000000..16e7aa7528
--- /dev/null
+++ b/ipc/glue/AsyncBlockers.h
@@ -0,0 +1,82 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et ft=cpp : */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_AsyncBlockers_h
+#define mozilla_ipc_AsyncBlockers_h
+
+#include "mozilla/MozPromise.h"
+#include "mozilla/ThreadSafety.h"
+#include "nsTArray.h"
+
+// FIXME: when bug 1760855 is fixed, it should not be required anymore
+
+namespace mozilla::ipc {
+
+/**
+ * AsyncBlockers provide a simple registration service that allows to suspend
+ * completion of a particular task until all registered entries have been
+ * cleared. This can be used to implement a similar service to
+ * nsAsyncShutdownService in processes where it wouldn't normally be available.
+ * This class is thread-safe.
+ */
+class AsyncBlockers {
+ public:
+  AsyncBlockers()
+      : mLock("AsyncRegistrar"),
+        mPromise(new GenericPromise::Private(__func__)) {}
+  void Register(void* aBlocker) {
+    MutexAutoLock lock(mLock);
+    mBlockers.InsertElementSorted(aBlocker);
+  }
+  void Deregister(void* aBlocker) {
+    MutexAutoLock lock(mLock);
+    MOZ_ASSERT(mBlockers.ContainsSorted(aBlocker));
+    MOZ_ALWAYS_TRUE(mBlockers.RemoveElementSorted(aBlocker));
+    MaybeResolve();
+  }
+  RefPtr<GenericPromise> WaitUntilClear(uint32_t aTimeOutInMs = 0) {
+    {
+      MutexAutoLock lock(mLock);
+      MaybeResolve();
+    }
+
+    if (aTimeOutInMs > 0) {
+      GetCurrentSerialEventTarget()->DelayedDispatch(
+          NS_NewRunnableFunction("AsyncBlockers::WaitUntilClear",
+                                 [promise = mPromise]() {
+                                   // The AsyncBlockers object may have been
+                                   // deleted by now and the object isn't
+                                   // refcounted (nor do we want it to be). We
+                                   // can unconditionally resolve the promise
+                                   // even it has already been resolved as
+                                   // MozPromise are thread-safe and will just
+                                   // ignore the action if already resolved.
+                                   promise->Resolve(true, __func__);
+                                 }),
+          aTimeOutInMs);
+    }
+
+    return mPromise;
+  }
+
+  virtual ~AsyncBlockers() { mPromise->Resolve(true, __func__); }
+
+ private:
+  void MaybeResolve() MOZ_REQUIRES(mLock) {
+    mLock.AssertCurrentThreadOwns();
+    if (!mBlockers.IsEmpty()) {
+      return;
+    }
+    mPromise->Resolve(true, __func__);
+  }
+  Mutex mLock;
+  nsTArray<void*> mBlockers MOZ_GUARDED_BY(mLock);
+  const RefPtr<GenericPromise::Private> mPromise;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // mozilla_ipc_AsyncBlockers_h
diff --git a/ipc/glue/BackgroundChild.h b/ipc/glue/BackgroundChild.h
new file mode 100644
index 0000000000..82a28c43d5
--- /dev/null
+++ b/ipc/glue/BackgroundChild.h
@@ -0,0 +1,101 @@
+/* -*- 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_ipc_backgroundchild_h__
+#define mozilla_ipc_backgroundchild_h__
+
+#include "mozilla/Attributes.h"
+
+class nsIEventTarget;
+
+namespace mozilla {
+namespace dom {
+
+class BlobImpl;
+class ContentChild;
+class ContentParent;
+class ContentProcess;
+
+}  // namespace dom
+
+namespace net {
+
+class SocketProcessChild;
+class SocketProcessBridgeChild;
+
+}  // namespace net
+
+namespace ipc {
+
+class PBackgroundChild;
+class PBackgroundStarterChild;
+
+// This class allows access to the PBackground protocol. PBackground allows
+// communication between any thread (in the parent or a child process) and a
+// single background thread in the parent process. Each PBackgroundChild
+// instance is tied to the thread on which it is created and must not be shared
+// across threads. Each PBackgroundChild is unique and valid as long as its
+// designated thread lives.
+//
+// Creation of PBackground is synchronous. GetOrCreateForCurrentThread will
+// create the actor if it doesn't exist yet. Thereafter (assuming success)
+// GetForCurrentThread() will return the same actor every time.
+//
+// GetOrCreateSocketActorForCurrentThread, which is like
+// GetOrCreateForCurrentThread, is used to get or create PBackground actor
+// between child process and socket process.
+//
+// CloseForCurrentThread() will close the current PBackground actor.  Subsequent
+// calls to GetForCurrentThread will return null.  CloseForCurrentThread() may
+// only be called exactly once for each thread-specific actor.  Currently it is
+// illegal to call this before the PBackground actor has been created.
+//
+// The PBackgroundChild actor and all its sub-protocol actors will be
+// automatically destroyed when its designated thread completes.
+//
+// Init{Content,Socket,SocketBridge}Starter must be called on the main thread
+// with an actor bridging to the relevant target process type before these
+// methods can be used.
+class BackgroundChild final {
+  friend class mozilla::dom::ContentParent;
+  friend class mozilla::dom::ContentProcess;
+  friend class mozilla::net::SocketProcessChild;
+
+ public:
+  // See above.
+  static PBackgroundChild* GetForCurrentThread();
+
+  // See above.
+  static PBackgroundChild* GetOrCreateForCurrentThread();
+
+  // See above.
+  static PBackgroundChild* GetOrCreateSocketActorForCurrentThread();
+
+  // See above.
+  static PBackgroundChild* GetOrCreateForSocketParentBridgeForCurrentThread();
+
+  // See above.
+  static void CloseForCurrentThread();
+
+  // See above.
+  static void InitContentStarter(mozilla::dom::ContentChild* aContent);
+
+  // See above.
+  static void InitSocketStarter(mozilla::net::SocketProcessChild* aSocket);
+
+  // See above.
+  static void InitSocketBridgeStarter(
+      mozilla::net::SocketProcessBridgeChild* aSocketBridge);
+
+ private:
+  // Only called by this class's friends.
+  static void Startup();
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_backgroundchild_h__
diff --git a/ipc/glue/BackgroundChildImpl.cpp b/ipc/glue/BackgroundChildImpl.cpp
new file mode 100644
index 0000000000..536ef2a10e
--- /dev/null
+++ b/ipc/glue/BackgroundChildImpl.cpp
@@ -0,0 +1,540 @@
+/* -*- 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 "BackgroundChildImpl.h"
+
+#include "BroadcastChannelChild.h"
+#ifdef MOZ_WEBRTC
+#  include "CamerasChild.h"
+#endif
+#include "mozilla/Assertions.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/dom/ClientManagerActors.h"
+#include "mozilla/dom/FileCreatorChild.h"
+#include "mozilla/dom/PBackgroundLSDatabaseChild.h"
+#include "mozilla/dom/PBackgroundLSObserverChild.h"
+#include "mozilla/dom/PBackgroundLSRequestChild.h"
+#include "mozilla/dom/PBackgroundLSSimpleRequestChild.h"
+#include "mozilla/dom/PBackgroundSDBConnectionChild.h"
+#include "mozilla/dom/PFileSystemRequestChild.h"
+#include "mozilla/dom/EndpointForReportChild.h"
+#include "mozilla/dom/PMediaTransportChild.h"
+#include "mozilla/dom/PVsync.h"
+#include "mozilla/dom/TemporaryIPCBlobChild.h"
+#include "mozilla/dom/cache/ActorUtils.h"
+#include "mozilla/dom/indexedDB/PBackgroundIndexedDBUtilsChild.h"
+#include "mozilla/dom/indexedDB/ThreadLocal.h"
+#include "mozilla/dom/quota/PQuotaChild.h"
+#include "mozilla/dom/RemoteWorkerChild.h"
+#include "mozilla/dom/RemoteWorkerControllerChild.h"
+#include "mozilla/dom/RemoteWorkerServiceChild.h"
+#include "mozilla/dom/ServiceWorkerChild.h"
+#include "mozilla/dom/SharedWorkerChild.h"
+#include "mozilla/dom/StorageIPC.h"
+#include "mozilla/dom/MessagePortChild.h"
+#include "mozilla/dom/ServiceWorkerContainerChild.h"
+#include "mozilla/dom/ServiceWorkerManagerChild.h"
+#include "mozilla/ipc/PBackgroundTestChild.h"
+#include "mozilla/net/PUDPSocketChild.h"
+#include "mozilla/dom/network/UDPSocketChild.h"
+#include "mozilla/dom/WebAuthnTransactionChild.h"
+#include "mozilla/dom/MIDIPortChild.h"
+#include "mozilla/dom/MIDIManagerChild.h"
+#include "nsID.h"
+
+namespace {
+
+class TestChild final : public mozilla::ipc::PBackgroundTestChild {
+  friend class mozilla::ipc::BackgroundChildImpl;
+
+  nsCString mTestArg;
+
+  explicit TestChild(const nsACString& aTestArg) : mTestArg(aTestArg) {
+    MOZ_COUNT_CTOR(TestChild);
+  }
+
+ protected:
+  ~TestChild() override { MOZ_COUNT_DTOR(TestChild); }
+
+ public:
+  mozilla::ipc::IPCResult Recv__delete__(const nsACString& aTestArg) override;
+};
+
+}  // namespace
+
+namespace mozilla::ipc {
+
+using mozilla::dom::UDPSocketChild;
+using mozilla::net::PUDPSocketChild;
+
+using mozilla::dom::PRemoteWorkerChild;
+using mozilla::dom::PServiceWorkerChild;
+using mozilla::dom::PServiceWorkerContainerChild;
+using mozilla::dom::PServiceWorkerRegistrationChild;
+using mozilla::dom::RemoteWorkerChild;
+using mozilla::dom::StorageDBChild;
+using mozilla::dom::cache::PCacheChild;
+using mozilla::dom::cache::PCacheStreamControlChild;
+
+using mozilla::dom::WebAuthnTransactionChild;
+
+using mozilla::dom::PMIDIManagerChild;
+using mozilla::dom::PMIDIPortChild;
+
+// -----------------------------------------------------------------------------
+// BackgroundChildImpl::ThreadLocal
+// -----------------------------------------------------------------------------
+
+BackgroundChildImpl::ThreadLocal::ThreadLocal() : mCurrentFileHandle(nullptr) {
+  // May happen on any thread!
+  MOZ_COUNT_CTOR(mozilla::ipc::BackgroundChildImpl::ThreadLocal);
+}
+
+BackgroundChildImpl::ThreadLocal::~ThreadLocal() {
+  // May happen on any thread!
+  MOZ_COUNT_DTOR(mozilla::ipc::BackgroundChildImpl::ThreadLocal);
+}
+
+// -----------------------------------------------------------------------------
+// BackgroundChildImpl
+// -----------------------------------------------------------------------------
+
+BackgroundChildImpl::BackgroundChildImpl() {
+  // May happen on any thread!
+  MOZ_COUNT_CTOR(mozilla::ipc::BackgroundChildImpl);
+}
+
+BackgroundChildImpl::~BackgroundChildImpl() {
+  // May happen on any thread!
+  MOZ_COUNT_DTOR(mozilla::ipc::BackgroundChildImpl);
+}
+
+void BackgroundChildImpl::ProcessingError(Result aCode, const char* aReason) {
+  // May happen on any thread!
+
+  nsAutoCString abortMessage;
+
+  switch (aCode) {
+    case MsgDropped:
+      return;
+
+#define HANDLE_CASE(_result)              \
+  case _result:                           \
+    abortMessage.AssignLiteral(#_result); \
+    break
+
+      HANDLE_CASE(MsgNotKnown);
+      HANDLE_CASE(MsgNotAllowed);
+      HANDLE_CASE(MsgPayloadError);
+      HANDLE_CASE(MsgProcessingError);
+      HANDLE_CASE(MsgRouteError);
+      HANDLE_CASE(MsgValueError);
+
+#undef HANDLE_CASE
+
+    default:
+      MOZ_CRASH("Unknown error code!");
+  }
+
+  MOZ_CRASH_UNSAFE_PRINTF("%s: %s", abortMessage.get(), aReason);
+}
+
+void BackgroundChildImpl::ActorDestroy(ActorDestroyReason aWhy) {
+  // May happen on any thread!
+}
+
+PBackgroundTestChild* BackgroundChildImpl::AllocPBackgroundTestChild(
+    const nsACString& aTestArg) {
+  return new TestChild(aTestArg);
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundTestChild(
+    PBackgroundTestChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete static_cast<TestChild*>(aActor);
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundIndexedDBUtilsChild*
+BackgroundChildImpl::AllocPBackgroundIndexedDBUtilsChild() {
+  MOZ_CRASH(
+      "PBackgroundIndexedDBUtilsChild actors should be manually "
+      "constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundIndexedDBUtilsChild(
+    PBackgroundIndexedDBUtilsChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundSDBConnectionChild*
+BackgroundChildImpl::AllocPBackgroundSDBConnectionChild(
+    const PersistenceType& aPersistenceType,
+    const PrincipalInfo& aPrincipalInfo) {
+  MOZ_CRASH(
+      "PBackgroundSDBConnectionChild actor should be manually "
+      "constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundSDBConnectionChild(
+    PBackgroundSDBConnectionChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundLSDatabaseChild*
+BackgroundChildImpl::AllocPBackgroundLSDatabaseChild(
+    const PrincipalInfo& aPrincipalInfo, const uint32_t& aPrivateBrowsingId,
+    const uint64_t& aDatastoreId) {
+  MOZ_CRASH("PBackgroundLSDatabaseChild actor should be manually constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundLSDatabaseChild(
+    PBackgroundLSDatabaseChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundLSObserverChild*
+BackgroundChildImpl::AllocPBackgroundLSObserverChild(
+    const uint64_t& aObserverId) {
+  MOZ_CRASH("PBackgroundLSObserverChild actor should be manually constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundLSObserverChild(
+    PBackgroundLSObserverChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundLSRequestChild*
+BackgroundChildImpl::AllocPBackgroundLSRequestChild(
+    const LSRequestParams& aParams) {
+  MOZ_CRASH("PBackgroundLSRequestChild actor should be manually constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundLSRequestChild(
+    PBackgroundLSRequestChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundLocalStorageCacheChild*
+BackgroundChildImpl::AllocPBackgroundLocalStorageCacheChild(
+    const PrincipalInfo& aPrincipalInfo, const nsACString& aOriginKey,
+    const uint32_t& aPrivateBrowsingId) {
+  MOZ_CRASH(
+      "PBackgroundLocalStorageChild actors should be manually "
+      "constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundLocalStorageCacheChild(
+    PBackgroundLocalStorageCacheChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundLSSimpleRequestChild*
+BackgroundChildImpl::AllocPBackgroundLSSimpleRequestChild(
+    const LSSimpleRequestParams& aParams) {
+  MOZ_CRASH(
+      "PBackgroundLSSimpleRequestChild actor should be manually "
+      "constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundLSSimpleRequestChild(
+    PBackgroundLSSimpleRequestChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+BackgroundChildImpl::PBackgroundStorageChild*
+BackgroundChildImpl::AllocPBackgroundStorageChild(
+    const nsAString& aProfilePath, const uint32_t& aPrivateBrowsingId) {
+  MOZ_CRASH("PBackgroundStorageChild actors should be manually constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPBackgroundStorageChild(
+    PBackgroundStorageChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  StorageDBChild* child = static_cast<StorageDBChild*>(aActor);
+  child->ReleaseIPDLReference();
+  return true;
+}
+
+already_AddRefed<PRemoteWorkerChild>
+BackgroundChildImpl::AllocPRemoteWorkerChild(const RemoteWorkerData& aData) {
+  return MakeAndAddRef<RemoteWorkerChild>(aData);
+}
+
+IPCResult BackgroundChildImpl::RecvPRemoteWorkerConstructor(
+    PRemoteWorkerChild* aActor, const RemoteWorkerData& aData) {
+  dom::RemoteWorkerChild* actor = static_cast<dom::RemoteWorkerChild*>(aActor);
+  actor->ExecWorker(aData);
+  return IPC_OK();
+}
+
+dom::PRemoteWorkerControllerChild*
+BackgroundChildImpl::AllocPRemoteWorkerControllerChild(
+    const dom::RemoteWorkerData& aRemoteWorkerData) {
+  MOZ_CRASH(
+      "PRemoteWorkerControllerChild actors must be manually constructed!");
+  return nullptr;
+}
+
+bool BackgroundChildImpl::DeallocPRemoteWorkerControllerChild(
+    dom::PRemoteWorkerControllerChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  RefPtr<dom::RemoteWorkerControllerChild> actor =
+      dont_AddRef(static_cast<dom::RemoteWorkerControllerChild*>(aActor));
+  return true;
+}
+
+dom::PSharedWorkerChild* BackgroundChildImpl::AllocPSharedWorkerChild(
+    const dom::RemoteWorkerData& aData, const uint64_t& aWindowID,
+    const dom::MessagePortIdentifier& aPortIdentifier) {
+  RefPtr<dom::SharedWorkerChild> agent = new dom::SharedWorkerChild();
+  return agent.forget().take();
+}
+
+bool BackgroundChildImpl::DeallocPSharedWorkerChild(
+    dom::PSharedWorkerChild* aActor) {
+  RefPtr<dom::SharedWorkerChild> actor =
+      dont_AddRef(static_cast<dom::SharedWorkerChild*>(aActor));
+  return true;
+}
+
+dom::PTemporaryIPCBlobChild*
+BackgroundChildImpl::AllocPTemporaryIPCBlobChild() {
+  MOZ_CRASH("This is not supposed to be called.");
+  return nullptr;
+}
+
+bool BackgroundChildImpl::DeallocPTemporaryIPCBlobChild(
+    dom::PTemporaryIPCBlobChild* aActor) {
+  RefPtr<dom::TemporaryIPCBlobChild> actor =
+      dont_AddRef(static_cast<dom::TemporaryIPCBlobChild*>(aActor));
+  return true;
+}
+
+dom::PFileCreatorChild* BackgroundChildImpl::AllocPFileCreatorChild(
+    const nsAString& aFullPath, const nsAString& aType, const nsAString& aName,
+    const Maybe<int64_t>& aLastModified, const bool& aExistenceCheck,
+    const bool& aIsFromNsIFile) {
+  return new dom::FileCreatorChild();
+}
+
+bool BackgroundChildImpl::DeallocPFileCreatorChild(PFileCreatorChild* aActor) {
+  delete static_cast<dom::FileCreatorChild*>(aActor);
+  return true;
+}
+
+PUDPSocketChild* BackgroundChildImpl::AllocPUDPSocketChild(
+    const Maybe<PrincipalInfo>& aPrincipalInfo, const nsACString& aFilter) {
+  MOZ_CRASH("AllocPUDPSocket should not be called");
+  return nullptr;
+}
+
+bool BackgroundChildImpl::DeallocPUDPSocketChild(PUDPSocketChild* child) {
+  UDPSocketChild* p = static_cast<UDPSocketChild*>(child);
+  p->ReleaseIPDLReference();
+  return true;
+}
+
+// -----------------------------------------------------------------------------
+// BroadcastChannel API
+// -----------------------------------------------------------------------------
+
+dom::PBroadcastChannelChild* BackgroundChildImpl::AllocPBroadcastChannelChild(
+    const PrincipalInfo& aPrincipalInfo, const nsACString& aOrigin,
+    const nsAString& aChannel) {
+  RefPtr<dom::BroadcastChannelChild> agent = new dom::BroadcastChannelChild();
+  return agent.forget().take();
+}
+
+bool BackgroundChildImpl::DeallocPBroadcastChannelChild(
+    PBroadcastChannelChild* aActor) {
+  RefPtr<dom::BroadcastChannelChild> child =
+      dont_AddRef(static_cast<dom::BroadcastChannelChild*>(aActor));
+  MOZ_ASSERT(child);
+  return true;
+}
+
+camera::PCamerasChild* BackgroundChildImpl::AllocPCamerasChild() {
+#ifdef MOZ_WEBRTC
+  RefPtr<camera::CamerasChild> agent = new camera::CamerasChild();
+  return agent.forget().take();
+#else
+  return nullptr;
+#endif
+}
+
+bool BackgroundChildImpl::DeallocPCamerasChild(camera::PCamerasChild* aActor) {
+#ifdef MOZ_WEBRTC
+  RefPtr<camera::CamerasChild> child =
+      dont_AddRef(static_cast<camera::CamerasChild*>(aActor));
+  MOZ_ASSERT(aActor);
+  camera::Shutdown();
+#endif
+  return true;
+}
+
+// -----------------------------------------------------------------------------
+// ServiceWorkerManager
+// -----------------------------------------------------------------------------
+
+dom::PServiceWorkerManagerChild*
+BackgroundChildImpl::AllocPServiceWorkerManagerChild() {
+  RefPtr<dom::ServiceWorkerManagerChild> agent =
+      new dom::ServiceWorkerManagerChild();
+  return agent.forget().take();
+}
+
+bool BackgroundChildImpl::DeallocPServiceWorkerManagerChild(
+    PServiceWorkerManagerChild* aActor) {
+  RefPtr<dom::ServiceWorkerManagerChild> child =
+      dont_AddRef(static_cast<dom::ServiceWorkerManagerChild*>(aActor));
+  MOZ_ASSERT(child);
+  return true;
+}
+
+// -----------------------------------------------------------------------------
+// Cache API
+// -----------------------------------------------------------------------------
+
+already_AddRefed<PCacheChild> BackgroundChildImpl::AllocPCacheChild() {
+  return dom::cache::AllocPCacheChild();
+}
+
+already_AddRefed<PCacheStreamControlChild>
+BackgroundChildImpl::AllocPCacheStreamControlChild() {
+  return dom::cache::AllocPCacheStreamControlChild();
+}
+
+// -----------------------------------------------------------------------------
+// MessageChannel/MessagePort API
+// -----------------------------------------------------------------------------
+
+dom::PMessagePortChild* BackgroundChildImpl::AllocPMessagePortChild(
+    const nsID& aUUID, const nsID& aDestinationUUID,
+    const uint32_t& aSequenceID) {
+  RefPtr<dom::MessagePortChild> agent = new dom::MessagePortChild();
+  return agent.forget().take();
+}
+
+bool BackgroundChildImpl::DeallocPMessagePortChild(PMessagePortChild* aActor) {
+  RefPtr<dom::MessagePortChild> child =
+      dont_AddRef(static_cast<dom::MessagePortChild*>(aActor));
+  MOZ_ASSERT(child);
+  return true;
+}
+
+BackgroundChildImpl::PQuotaChild* BackgroundChildImpl::AllocPQuotaChild() {
+  MOZ_CRASH("PQuotaChild actor should be manually constructed!");
+}
+
+bool BackgroundChildImpl::DeallocPQuotaChild(PQuotaChild* aActor) {
+  MOZ_ASSERT(aActor);
+  delete aActor;
+  return true;
+}
+
+mozilla::dom::PClientManagerChild*
+BackgroundChildImpl::AllocPClientManagerChild() {
+  return mozilla::dom::AllocClientManagerChild();
+}
+
+bool BackgroundChildImpl::DeallocPClientManagerChild(
+    mozilla::dom::PClientManagerChild* aActor) {
+  return mozilla::dom::DeallocClientManagerChild(aActor);
+}
+
+dom::PWebAuthnTransactionChild*
+BackgroundChildImpl::AllocPWebAuthnTransactionChild() {
+  MOZ_CRASH("PWebAuthnTransaction actor should be manually constructed!");
+  return nullptr;
+}
+
+bool BackgroundChildImpl::DeallocPWebAuthnTransactionChild(
+    PWebAuthnTransactionChild* aActor) {
+  MOZ_ASSERT(aActor);
+  RefPtr<dom::WebAuthnTransactionChild> child =
+      dont_AddRef(static_cast<dom::WebAuthnTransactionChild*>(aActor));
+  return true;
+}
+
+already_AddRefed<PServiceWorkerChild>
+BackgroundChildImpl::AllocPServiceWorkerChild(
+    const IPCServiceWorkerDescriptor&) {
+  MOZ_CRASH("Shouldn't be called.");
+  return {};
+}
+
+already_AddRefed<PServiceWorkerContainerChild>
+BackgroundChildImpl::AllocPServiceWorkerContainerChild() {
+  return mozilla::dom::ServiceWorkerContainerChild::Create();
+}
+
+already_AddRefed<PServiceWorkerRegistrationChild>
+BackgroundChildImpl::AllocPServiceWorkerRegistrationChild(
+    const IPCServiceWorkerRegistrationDescriptor&) {
+  MOZ_CRASH("Shouldn't be called.");
+  return {};
+}
+
+dom::PEndpointForReportChild* BackgroundChildImpl::AllocPEndpointForReportChild(
+    const nsAString& aGroupName, const PrincipalInfo& aPrincipalInfo) {
+  return new dom::EndpointForReportChild();
+}
+
+bool BackgroundChildImpl::DeallocPEndpointForReportChild(
+    PEndpointForReportChild* aActor) {
+  MOZ_ASSERT(aActor);
+  delete static_cast<dom::EndpointForReportChild*>(aActor);
+  return true;
+}
+
+dom::PMediaTransportChild* BackgroundChildImpl::AllocPMediaTransportChild() {
+  // We don't allocate here: MediaTransportHandlerIPC is in charge of that,
+  // so we don't need to know the implementation particulars here.
+  MOZ_ASSERT_UNREACHABLE(
+      "The only thing that ought to be creating a PMediaTransportChild is "
+      "MediaTransportHandlerIPC!");
+  return nullptr;
+}
+
+bool BackgroundChildImpl::DeallocPMediaTransportChild(
+    dom::PMediaTransportChild* aActor) {
+  delete aActor;
+  return true;
+}
+
+}  // namespace mozilla::ipc
+
+mozilla::ipc::IPCResult TestChild::Recv__delete__(const nsACString& aTestArg) {
+  MOZ_RELEASE_ASSERT(aTestArg == mTestArg,
+                     "BackgroundTest message was corrupted!");
+
+  return IPC_OK();
+}
diff --git a/ipc/glue/BackgroundChildImpl.h b/ipc/glue/BackgroundChildImpl.h
new file mode 100644
index 0000000000..28d3dbc14c
--- /dev/null
+++ b/ipc/glue/BackgroundChildImpl.h
@@ -0,0 +1,227 @@
+/* -*- 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_ipc_backgroundchildimpl_h__
+#define mozilla_ipc_backgroundchildimpl_h__
+
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+namespace dom {
+
+class IDBFileHandle;
+
+namespace indexedDB {
+
+class ThreadLocal;
+
+}  // namespace indexedDB
+}  // namespace dom
+
+namespace ipc {
+
+// Instances of this class should never be created directly. This class is meant
+// to be inherited in BackgroundImpl.
+class BackgroundChildImpl : public PBackgroundChild {
+ public:
+  class ThreadLocal;
+
+  // Get the ThreadLocal for the current thread if
+  // BackgroundChild::GetOrCreateForCurrentThread() has been called and true was
+  // returned (e.g. a valid PBackgroundChild actor has been created or is in the
+  // process of being created). Otherwise this function returns null.
+  // This functions is implemented in BackgroundImpl.cpp.
+  static ThreadLocal* GetThreadLocalForCurrentThread();
+
+ protected:
+  BackgroundChildImpl();
+  virtual ~BackgroundChildImpl();
+
+  virtual void ProcessingError(Result aCode, const char* aReason) override;
+
+  virtual void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  virtual PBackgroundTestChild* AllocPBackgroundTestChild(
+      const nsACString& aTestArg) override;
+
+  virtual bool DeallocPBackgroundTestChild(
+      PBackgroundTestChild* aActor) override;
+
+  virtual PBackgroundIndexedDBUtilsChild* AllocPBackgroundIndexedDBUtilsChild()
+      override;
+
+  virtual bool DeallocPBackgroundIndexedDBUtilsChild(
+      PBackgroundIndexedDBUtilsChild* aActor) override;
+
+  virtual PBackgroundSDBConnectionChild* AllocPBackgroundSDBConnectionChild(
+      const PersistenceType& aPersistenceType,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  virtual bool DeallocPBackgroundSDBConnectionChild(
+      PBackgroundSDBConnectionChild* aActor) override;
+
+  virtual PBackgroundLSDatabaseChild* AllocPBackgroundLSDatabaseChild(
+      const PrincipalInfo& aPrincipalInfo, const uint32_t& aPrivateBrowsingId,
+      const uint64_t& aDatastoreId) override;
+
+  virtual bool DeallocPBackgroundLSDatabaseChild(
+      PBackgroundLSDatabaseChild* aActor) override;
+
+  virtual PBackgroundLSObserverChild* AllocPBackgroundLSObserverChild(
+      const uint64_t& aObserverId) override;
+
+  virtual bool DeallocPBackgroundLSObserverChild(
+      PBackgroundLSObserverChild* aActor) override;
+
+  virtual PBackgroundLSRequestChild* AllocPBackgroundLSRequestChild(
+      const LSRequestParams& aParams) override;
+
+  virtual bool DeallocPBackgroundLSRequestChild(
+      PBackgroundLSRequestChild* aActor) override;
+
+  virtual PBackgroundLSSimpleRequestChild* AllocPBackgroundLSSimpleRequestChild(
+      const LSSimpleRequestParams& aParams) override;
+
+  virtual bool DeallocPBackgroundLSSimpleRequestChild(
+      PBackgroundLSSimpleRequestChild* aActor) override;
+
+  virtual PBackgroundLocalStorageCacheChild*
+  AllocPBackgroundLocalStorageCacheChild(
+      const PrincipalInfo& aPrincipalInfo, const nsACString& aOriginKey,
+      const uint32_t& aPrivateBrowsingId) override;
+
+  virtual bool DeallocPBackgroundLocalStorageCacheChild(
+      PBackgroundLocalStorageCacheChild* aActor) override;
+
+  virtual PBackgroundStorageChild* AllocPBackgroundStorageChild(
+      const nsAString& aProfilePath,
+      const uint32_t& aPrivateBrowsingId) override;
+
+  virtual bool DeallocPBackgroundStorageChild(
+      PBackgroundStorageChild* aActor) override;
+
+  virtual PTemporaryIPCBlobChild* AllocPTemporaryIPCBlobChild() override;
+
+  virtual bool DeallocPTemporaryIPCBlobChild(
+      PTemporaryIPCBlobChild* aActor) override;
+
+  virtual PFileCreatorChild* AllocPFileCreatorChild(
+      const nsAString& aFullPath, const nsAString& aType,
+      const nsAString& aName, const Maybe<int64_t>& aLastModified,
+      const bool& aExistenceCheck, const bool& aIsFromNsIFile) override;
+
+  virtual bool DeallocPFileCreatorChild(PFileCreatorChild* aActor) override;
+
+  already_AddRefed<mozilla::dom::PRemoteWorkerChild> AllocPRemoteWorkerChild(
+      const RemoteWorkerData& aData) override;
+
+  virtual mozilla::ipc::IPCResult RecvPRemoteWorkerConstructor(
+      PRemoteWorkerChild* aActor, const RemoteWorkerData& aData) override;
+
+  virtual mozilla::dom::PRemoteWorkerControllerChild*
+  AllocPRemoteWorkerControllerChild(
+      const mozilla::dom::RemoteWorkerData& aRemoteWorkerData) override;
+
+  virtual bool DeallocPRemoteWorkerControllerChild(
+      mozilla::dom::PRemoteWorkerControllerChild* aActor) override;
+
+  virtual mozilla::dom::PSharedWorkerChild* AllocPSharedWorkerChild(
+      const mozilla::dom::RemoteWorkerData& aData, const uint64_t& aWindowID,
+      const mozilla::dom::MessagePortIdentifier& aPortIdentifier) override;
+
+  virtual bool DeallocPSharedWorkerChild(
+      mozilla::dom::PSharedWorkerChild* aActor) override;
+
+  virtual PCamerasChild* AllocPCamerasChild() override;
+
+  virtual bool DeallocPCamerasChild(PCamerasChild* aActor) override;
+
+  virtual PUDPSocketChild* AllocPUDPSocketChild(
+      const Maybe<PrincipalInfo>& aPrincipalInfo,
+      const nsACString& aFilter) override;
+  virtual bool DeallocPUDPSocketChild(PUDPSocketChild* aActor) override;
+
+  virtual PBroadcastChannelChild* AllocPBroadcastChannelChild(
+      const PrincipalInfo& aPrincipalInfo, const nsACString& aOrigin,
+      const nsAString& aChannel) override;
+
+  virtual bool DeallocPBroadcastChannelChild(
+      PBroadcastChannelChild* aActor) override;
+
+  virtual PServiceWorkerManagerChild* AllocPServiceWorkerManagerChild()
+      override;
+
+  virtual bool DeallocPServiceWorkerManagerChild(
+      PServiceWorkerManagerChild* aActor) override;
+
+  virtual already_AddRefed<dom::cache::PCacheChild> AllocPCacheChild() override;
+
+  virtual already_AddRefed<dom::cache::PCacheStreamControlChild>
+  AllocPCacheStreamControlChild() override;
+
+  virtual PMessagePortChild* AllocPMessagePortChild(
+      const nsID& aUUID, const nsID& aDestinationUUID,
+      const uint32_t& aSequenceID) override;
+
+  virtual bool DeallocPMessagePortChild(PMessagePortChild* aActor) override;
+
+  virtual PQuotaChild* AllocPQuotaChild() override;
+
+  virtual bool DeallocPQuotaChild(PQuotaChild* aActor) override;
+
+  virtual PClientManagerChild* AllocPClientManagerChild() override;
+
+  virtual bool DeallocPClientManagerChild(PClientManagerChild* aActor) override;
+
+  virtual PWebAuthnTransactionChild* AllocPWebAuthnTransactionChild() override;
+
+  virtual bool DeallocPWebAuthnTransactionChild(
+      PWebAuthnTransactionChild* aActor) override;
+
+  already_AddRefed<PServiceWorkerChild> AllocPServiceWorkerChild(
+      const IPCServiceWorkerDescriptor&);
+
+  already_AddRefed<PServiceWorkerContainerChild>
+  AllocPServiceWorkerContainerChild();
+
+  already_AddRefed<PServiceWorkerRegistrationChild>
+  AllocPServiceWorkerRegistrationChild(
+      const IPCServiceWorkerRegistrationDescriptor&);
+
+  virtual PEndpointForReportChild* AllocPEndpointForReportChild(
+      const nsAString& aGroupName,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  virtual bool DeallocPEndpointForReportChild(
+      PEndpointForReportChild* aActor) override;
+
+  virtual dom::PMediaTransportChild* AllocPMediaTransportChild() override;
+
+  virtual bool DeallocPMediaTransportChild(
+      dom::PMediaTransportChild* aActor) override;
+};
+
+class BackgroundChildImpl::ThreadLocal final {
+  friend class mozilla::DefaultDelete<ThreadLocal>;
+
+ public:
+  mozilla::UniquePtr<mozilla::dom::indexedDB::ThreadLocal>
+      mIndexedDBThreadLocal;
+  mozilla::dom::IDBFileHandle* mCurrentFileHandle;
+
+ public:
+  ThreadLocal();
+
+ private:
+  // Only destroyed by UniquePtr<ThreadLocal>.
+  ~ThreadLocal();
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_backgroundchildimpl_h__
diff --git a/ipc/glue/BackgroundImpl.cpp b/ipc/glue/BackgroundImpl.cpp
new file mode 100644
index 0000000000..420f047f42
--- /dev/null
+++ b/ipc/glue/BackgroundImpl.cpp
@@ -0,0 +1,1306 @@
+/* -*- 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 "BackgroundChild.h"
+#include "BackgroundParent.h"
+
+#include "BackgroundChildImpl.h"
+#include "BackgroundParentImpl.h"
+#include "MainThreadUtils.h"
+#include "base/process_util.h"
+#include "base/task.h"
+#include "FileDescriptor.h"
+#include "GeckoProfiler.h"
+#include "InputStreamUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/dom/WorkerRef.h"
+#include "mozilla/ipc/BackgroundStarterChild.h"
+#include "mozilla/ipc/BackgroundStarterParent.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/PBackgroundStarter.h"
+#include "mozilla/ipc/ProtocolTypes.h"
+#include "mozilla/net/SocketProcessChild.h"
+#include "mozilla/net/SocketProcessBridgeChild.h"
+#include "nsCOMPtr.h"
+#include "nsIEventTarget.h"
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+#include "nsIRunnable.h"
+#include "nsISupportsImpl.h"
+#include "nsIThread.h"
+#include "nsITimer.h"
+#include "nsTArray.h"
+#include "nsThreadUtils.h"
+#include "nsTraceRefcnt.h"
+#include "nsXULAppAPI.h"
+#include "nsXPCOMPrivate.h"
+#include "prthread.h"
+
+#include <functional>
+
+#ifdef RELEASE_OR_BETA
+#  define THREADSAFETY_ASSERT MOZ_ASSERT
+#else
+#  define THREADSAFETY_ASSERT MOZ_RELEASE_ASSERT
+#endif
+
+#define CRASH_IN_CHILD_PROCESS(_msg) \
+  do {                               \
+    if (XRE_IsParentProcess()) {     \
+      MOZ_ASSERT(false, _msg);       \
+    } else {                         \
+      MOZ_CRASH(_msg);               \
+    }                                \
+  } while (0)
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::ipc;
+using namespace mozilla::net;
+
+namespace {
+
+class ChildImpl;
+
+// -----------------------------------------------------------------------------
+// Utility Functions
+// -----------------------------------------------------------------------------
+
+void AssertIsInMainOrSocketProcess() {
+  MOZ_ASSERT(XRE_IsParentProcess() || XRE_IsSocketProcess());
+}
+
+void AssertIsOnMainThread() { THREADSAFETY_ASSERT(NS_IsMainThread()); }
+
+// -----------------------------------------------------------------------------
+// ParentImpl Declaration
+// -----------------------------------------------------------------------------
+
+class ParentImpl final : public BackgroundParentImpl {
+  friend class ChildImpl;
+  friend class mozilla::ipc::BackgroundParent;
+  friend class mozilla::ipc::BackgroundStarterParent;
+
+ private:
+  class ShutdownObserver;
+
+  struct MOZ_STACK_CLASS TimerCallbackClosure {
+    nsIThread* mThread;
+    nsTArray<IToplevelProtocol*>* mLiveActors;
+
+    TimerCallbackClosure(nsIThread* aThread,
+                         nsTArray<IToplevelProtocol*>* aLiveActors)
+        : mThread(aThread), mLiveActors(aLiveActors) {
+      AssertIsInMainOrSocketProcess();
+      AssertIsOnMainThread();
+      MOZ_ASSERT(aThread);
+      MOZ_ASSERT(aLiveActors);
+    }
+  };
+
+  // The length of time we will wait at shutdown for all actors to clean
+  // themselves up before forcing them to be destroyed.
+  static const uint32_t kShutdownTimerDelayMS = 10000;
+
+  // This is only modified on the main thread. It is null if the thread does not
+  // exist or is shutting down.
+  static StaticRefPtr<nsIThread> sBackgroundThread;
+
+  // This is created and destroyed on the main thread but only modified on the
+  // background thread. It is specific to each instance of sBackgroundThread.
+  static nsTArray<IToplevelProtocol*>* sLiveActorsForBackgroundThread;
+
+  // This is only modified on the main thread.
+  static StaticRefPtr<nsITimer> sShutdownTimer;
+
+  // This exists so that that [Assert]IsOnBackgroundThread() can continue to
+  // work during shutdown.
+  static Atomic<PRThread*> sBackgroundPRThread;
+
+  // Maintains a count of live actors so that the background thread can be shut
+  // down when it is no longer needed.
+  // May be incremented on either the background thread (by an existing actor)
+  // or on the main thread, but must be decremented on the main thread.
+  static Atomic<uint64_t> sLiveActorCount;
+
+  // This is only modified on the main thread. It is true after the shutdown
+  // observer is registered and is never unset thereafter.
+  static bool sShutdownObserverRegistered;
+
+  // This is only modified on the main thread. It prevents us from trying to
+  // create the background thread after application shutdown has started.
+  static bool sShutdownHasStarted;
+
+  // null if this is a same-process or socket process actor.
+  const RefPtr<ThreadsafeContentParentHandle> mContent;
+
+  // Set when the actor is opened successfully and used to handle shutdown
+  // hangs. Only touched on the background thread.
+  nsTArray<IToplevelProtocol*>* mLiveActorArray;
+
+  // Set at construction to indicate whether this parent actor corresponds to a
+  // child actor in another process or to a child actor from a different thread
+  // in the same process.
+  const bool mIsOtherProcessActor;
+
+  // Set after ActorDestroy has been called. Only touched on the background
+  // thread.
+  bool mActorDestroyed;
+
+ public:
+  static bool IsOnBackgroundThread() {
+    return PR_GetCurrentThread() == sBackgroundPRThread;
+  }
+
+  static void AssertIsOnBackgroundThread() {
+    THREADSAFETY_ASSERT(IsOnBackgroundThread());
+  }
+
+  // `ParentImpl` instances need to be deleted on the main thread, despite IPC
+  // controlling them on a background thread. Use `_WITH_DELETE_ON_MAIN_THREAD`
+  // to force destruction to occur on the desired thread.
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING_WITH_DELETE_ON_MAIN_THREAD(ParentImpl,
+                                                                   override)
+
+  void Destroy();
+
+ private:
+  // Forwarded from BackgroundParent.
+  static bool IsOtherProcessActor(PBackgroundParent* aBackgroundActor);
+
+  // Forwarded from BackgroundParent.
+  static ThreadsafeContentParentHandle* GetContentParentHandle(
+      PBackgroundParent* aBackgroundActor);
+
+  // Forwarded from BackgroundParent.
+  static uint64_t GetChildID(PBackgroundParent* aBackgroundActor);
+
+  // Forwarded from BackgroundParent.
+  static bool AllocStarter(ContentParent* aContent,
+                           Endpoint<PBackgroundStarterParent>&& aEndpoint,
+                           bool aCrossProcess = true);
+
+  static bool CreateBackgroundThread();
+
+  static void ShutdownBackgroundThread();
+
+  static void ShutdownTimerCallback(nsITimer* aTimer, void* aClosure);
+
+  // NOTE: ParentImpl could be used in 4 cases below.
+  // 1. Within the parent process.
+  // 2. Between parent process and content process.
+  // 3. Between socket process and content process.
+  // 4. Between parent process and socket process.
+  // |aContent| should be not null for case 2. For cases 1, 3 and 4, it's null.
+  explicit ParentImpl(ThreadsafeContentParentHandle* aContent,
+                      bool aIsOtherProcessActor)
+      : mContent(aContent),
+        mLiveActorArray(nullptr),
+        mIsOtherProcessActor(aIsOtherProcessActor),
+        mActorDestroyed(false) {
+    MOZ_ASSERT(XRE_IsParentProcess() || XRE_IsSocketProcess());
+    MOZ_ASSERT_IF(!aIsOtherProcessActor, XRE_IsParentProcess());
+  }
+
+  ~ParentImpl() {
+    AssertIsInMainOrSocketProcess();
+    AssertIsOnMainThread();
+  }
+
+  void MainThreadActorDestroy();
+
+  void SetLiveActorArray(nsTArray<IToplevelProtocol*>* aLiveActorArray) {
+    AssertIsInMainOrSocketProcess();
+    AssertIsOnBackgroundThread();
+    MOZ_ASSERT(aLiveActorArray);
+    MOZ_ASSERT(!aLiveActorArray->Contains(this));
+    MOZ_ASSERT(!mLiveActorArray);
+    MOZ_ASSERT(mIsOtherProcessActor);
+
+    mLiveActorArray = aLiveActorArray;
+    mLiveActorArray->AppendElement(this);
+  }
+
+  // These methods are only called by IPDL.
+  virtual void ActorDestroy(ActorDestroyReason aWhy) override;
+};
+
+// -----------------------------------------------------------------------------
+// ChildImpl Declaration
+// -----------------------------------------------------------------------------
+
+class ChildImpl final : public BackgroundChildImpl {
+  friend class mozilla::ipc::BackgroundChild;
+  friend class mozilla::ipc::BackgroundChildImpl;
+  friend class mozilla::ipc::BackgroundStarterChild;
+
+  typedef base::ProcessId ProcessId;
+
+  class ShutdownObserver;
+
+ public:
+  struct ThreadLocalInfo {
+    ThreadLocalInfo()
+#ifdef DEBUG
+        : mClosed(false)
+#endif
+    {
+    }
+
+    RefPtr<ChildImpl> mActor;
+    UniquePtr<BackgroundChildImpl::ThreadLocal> mConsumerThreadLocal;
+#ifdef DEBUG
+    bool mClosed;
+#endif
+  };
+
+ private:
+  // A thread-local index that is not valid.
+  static constexpr unsigned int kBadThreadLocalIndex =
+      static_cast<unsigned int>(-1);
+
+  // ThreadInfoWrapper encapsulates ThreadLocalInfo and ThreadLocalIndex and
+  // also provides some common functions for creating PBackground IPC actor.
+  class ThreadInfoWrapper final {
+    friend class ChildImpl;
+
+   public:
+    using ActorCreateFunc = void (*)(ThreadLocalInfo*, unsigned int,
+                                     nsIEventTarget*, ChildImpl**);
+
+    ThreadInfoWrapper() = default;
+
+    void Startup() {
+      MOZ_ASSERT(mThreadLocalIndex == kBadThreadLocalIndex,
+                 "ThreadInfoWrapper::Startup() called more than once!");
+
+      PRStatus status =
+          PR_NewThreadPrivateIndex(&mThreadLocalIndex, ThreadLocalDestructor);
+      MOZ_RELEASE_ASSERT(status == PR_SUCCESS,
+                         "PR_NewThreadPrivateIndex failed!");
+
+      MOZ_ASSERT(mThreadLocalIndex != kBadThreadLocalIndex);
+    }
+
+    void Shutdown() {
+      if (sShutdownHasStarted) {
+        MOZ_ASSERT_IF(mThreadLocalIndex != kBadThreadLocalIndex,
+                      !PR_GetThreadPrivate(mThreadLocalIndex));
+        return;
+      }
+
+      if (mThreadLocalIndex == kBadThreadLocalIndex) {
+        return;
+      }
+
+      RefPtr<BackgroundStarterChild> starter;
+      {
+        auto lock = mStarter.Lock();
+        starter = lock->forget();
+      }
+      if (starter) {
+        CloseStarter(starter);
+      }
+
+      ThreadLocalInfo* threadLocalInfo;
+#ifdef DEBUG
+      threadLocalInfo =
+          static_cast<ThreadLocalInfo*>(PR_GetThreadPrivate(mThreadLocalIndex));
+      MOZ_ASSERT(!threadLocalInfo);
+#endif
+
+      threadLocalInfo = mMainThreadInfo;
+      if (threadLocalInfo) {
+#ifdef DEBUG
+        MOZ_ASSERT(!threadLocalInfo->mClosed);
+        threadLocalInfo->mClosed = true;
+#endif
+
+        ThreadLocalDestructor(threadLocalInfo);
+        mMainThreadInfo = nullptr;
+      }
+    }
+
+    template <typename Actor>
+    void InitStarter(Actor* aActor) {
+      AssertIsOnMainThread();
+
+      // Create a pair of endpoints and send them to the other process.
+      Endpoint<PBackgroundStarterParent> parent;
+      Endpoint<PBackgroundStarterChild> child;
+      MOZ_ALWAYS_SUCCEEDS(PBackgroundStarter::CreateEndpoints(
+          aActor->OtherPid(), base::GetCurrentProcId(), &parent, &child));
+      MOZ_ALWAYS_TRUE(aActor->SendInitBackground(std::move(parent)));
+
+      InitStarter(std::move(child));
+    }
+
+    void InitStarter(Endpoint<PBackgroundStarterChild>&& aEndpoint) {
+      AssertIsOnMainThread();
+
+      base::ProcessId otherPid = aEndpoint.OtherPid();
+
+      nsCOMPtr<nsISerialEventTarget> taskQueue;
+      MOZ_ALWAYS_SUCCEEDS(NS_CreateBackgroundTaskQueue(
+          "PBackgroundStarter Queue", getter_AddRefs(taskQueue)));
+
+      RefPtr<BackgroundStarterChild> starter =
+          new BackgroundStarterChild(otherPid, taskQueue);
+
+      taskQueue->Dispatch(NS_NewRunnableFunction(
+          "PBackgroundStarterChild Init",
+          [starter, endpoint = std::move(aEndpoint)]() mutable {
+            MOZ_ALWAYS_TRUE(endpoint.Bind(starter));
+          }));
+
+      // Swap in the newly initialized `BackgroundStarterChild`, and close the
+      // previous one if we're replacing an existing PBackgroundStarterChild
+      // instance.
+      RefPtr<BackgroundStarterChild> prevStarter;
+      {
+        auto lock = mStarter.Lock();
+        prevStarter = lock->forget();
+        *lock = starter.forget();
+      }
+      if (prevStarter) {
+        CloseStarter(prevStarter);
+      }
+    }
+
+    void CloseForCurrentThread() {
+      MOZ_ASSERT(!NS_IsMainThread());
+
+      if (mThreadLocalIndex == kBadThreadLocalIndex) {
+        return;
+      }
+
+      auto* threadLocalInfo =
+          static_cast<ThreadLocalInfo*>(PR_GetThreadPrivate(mThreadLocalIndex));
+
+      if (!threadLocalInfo) {
+        return;
+      }
+
+#ifdef DEBUG
+      MOZ_ASSERT(!threadLocalInfo->mClosed);
+      threadLocalInfo->mClosed = true;
+#endif
+
+      // Clearing the thread local will synchronously close the actor.
+      DebugOnly<PRStatus> status =
+          PR_SetThreadPrivate(mThreadLocalIndex, nullptr);
+      MOZ_ASSERT(status == PR_SUCCESS);
+    }
+
+    PBackgroundChild* GetOrCreateForCurrentThread() {
+      // Processes can be told to do final CC's during shutdown even though
+      // they never finished starting (and thus call this), because they
+      // hadn't gotten far enough to call Startup() before shutdown began.
+      if (mThreadLocalIndex == kBadThreadLocalIndex) {
+        NS_ERROR("BackgroundChild::Startup() was never called");
+        return nullptr;
+      }
+      if (NS_IsMainThread() && ChildImpl::sShutdownHasStarted) {
+        return nullptr;
+      }
+
+      auto* threadLocalInfo = NS_IsMainThread()
+                                  ? mMainThreadInfo
+                                  : static_cast<ThreadLocalInfo*>(
+                                        PR_GetThreadPrivate(mThreadLocalIndex));
+
+      if (!threadLocalInfo) {
+        auto newInfo = MakeUnique<ThreadLocalInfo>();
+
+        if (NS_IsMainThread()) {
+          mMainThreadInfo = newInfo.get();
+        } else {
+          if (PR_SetThreadPrivate(mThreadLocalIndex, newInfo.get()) !=
+              PR_SUCCESS) {
+            CRASH_IN_CHILD_PROCESS("PR_SetThreadPrivate failed!");
+            return nullptr;
+          }
+        }
+
+        threadLocalInfo = newInfo.release();
+      }
+
+      if (threadLocalInfo->mActor) {
+        return threadLocalInfo->mActor;
+      }
+
+      RefPtr<BackgroundStarterChild> starter;
+      {
+        auto lock = mStarter.Lock();
+        starter = *lock;
+      }
+      if (!starter) {
+        CRASH_IN_CHILD_PROCESS("No BackgroundStarterChild");
+        return nullptr;
+      }
+
+      Endpoint<PBackgroundParent> parent;
+      Endpoint<PBackgroundChild> child;
+      nsresult rv;
+      rv = PBackground::CreateEndpoints(
+          starter->mOtherPid, base::GetCurrentProcId(), &parent, &child);
+      if (NS_FAILED(rv)) {
+        NS_WARNING("Failed to create top level actor!");
+        return nullptr;
+      }
+
+      RefPtr<ChildImpl> strongActor = new ChildImpl();
+      if (!child.Bind(strongActor)) {
+        CRASH_IN_CHILD_PROCESS("Failed to bind ChildImpl!");
+        return nullptr;
+      }
+      strongActor->SetActorAlive();
+      threadLocalInfo->mActor = strongActor;
+
+      // Dispatch to the background task queue to create the relevant actor in
+      // the remote process.
+      starter->mTaskQueue->Dispatch(NS_NewRunnableFunction(
+          "PBackground GetOrCreateForCurrentThread",
+          [starter, endpoint = std::move(parent)]() mutable {
+            if (!starter->SendInitBackground(std::move(endpoint))) {
+              NS_WARNING("Failed to create toplevel actor");
+            }
+          }));
+      return strongActor;
+    }
+
+   private:
+    static void CloseStarter(BackgroundStarterChild* aStarter) {
+      aStarter->mTaskQueue->Dispatch(NS_NewRunnableFunction(
+          "PBackgroundStarterChild Close",
+          [starter = RefPtr{aStarter}] { starter->Close(); }));
+    }
+
+    // This is only modified on the main thread. It is the thread-local index
+    // that we use to store the BackgroundChild for each thread.
+    unsigned int mThreadLocalIndex = kBadThreadLocalIndex;
+
+    // On the main thread, we store TLS in this global instead of in
+    // mThreadLocalIndex. That way, cooperative main threads all share the same
+    // thread info.
+    ThreadLocalInfo* mMainThreadInfo = nullptr;
+
+    // The starter which will be used to launch PBackground instances of this
+    // type. Only modified on the main thread, but may be read by any thread
+    // wanting to start background actors.
+    StaticDataMutex<StaticRefPtr<BackgroundStarterChild>> mStarter{"mStarter"};
+  };
+
+  // For PBackground between parent and content process.
+  static ThreadInfoWrapper sParentAndContentProcessThreadInfo;
+
+  // For PBackground between socket and content process.
+  static ThreadInfoWrapper sSocketAndContentProcessThreadInfo;
+
+  // For PBackground between socket and parent process.
+  static ThreadInfoWrapper sSocketAndParentProcessThreadInfo;
+
+  // This is only modified on the main thread. It prevents us from trying to
+  // create the background thread after application shutdown has started.
+  static bool sShutdownHasStarted;
+
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA)
+  nsISerialEventTarget* mOwningEventTarget;
+#endif
+
+#ifdef DEBUG
+  bool mActorWasAlive;
+  bool mActorDestroyed;
+#endif
+
+ public:
+  static void Shutdown();
+
+  void AssertIsOnOwningThread() {
+    THREADSAFETY_ASSERT(mOwningEventTarget);
+
+#ifdef RELEASE_OR_BETA
+    DebugOnly<bool> current;
+#else
+    bool current;
+#endif
+    THREADSAFETY_ASSERT(
+        NS_SUCCEEDED(mOwningEventTarget->IsOnCurrentThread(&current)));
+    THREADSAFETY_ASSERT(current);
+  }
+
+  void AssertActorDestroyed() {
+    MOZ_ASSERT(mActorDestroyed, "ChildImpl::ActorDestroy not called in time");
+  }
+
+  explicit ChildImpl()
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA)
+      : mOwningEventTarget(GetCurrentSerialEventTarget())
+#endif
+#ifdef DEBUG
+        ,
+        mActorWasAlive(false),
+        mActorDestroyed(false)
+#endif
+  {
+    AssertIsOnOwningThread();
+  }
+
+  void SetActorAlive() {
+    AssertIsOnOwningThread();
+    MOZ_ASSERT(!mActorWasAlive);
+    MOZ_ASSERT(!mActorDestroyed);
+
+#ifdef DEBUG
+    mActorWasAlive = true;
+#endif
+  }
+
+  NS_INLINE_DECL_REFCOUNTING(ChildImpl, override)
+
+ private:
+  // Forwarded from BackgroundChild.
+  static void Startup();
+
+  // Forwarded from BackgroundChild.
+  static PBackgroundChild* GetForCurrentThread();
+
+  // Forwarded from BackgroundChild.
+  static PBackgroundChild* GetOrCreateForCurrentThread();
+
+  // Forwarded from BackgroundChild.
+  static PBackgroundChild* GetOrCreateSocketActorForCurrentThread();
+
+  // Forwarded from BackgroundChild.
+  static PBackgroundChild* GetOrCreateForSocketParentBridgeForCurrentThread();
+
+  static void CloseForCurrentThread();
+
+  // Forwarded from BackgroundChildImpl.
+  static BackgroundChildImpl::ThreadLocal* GetThreadLocalForCurrentThread();
+
+  // Forwarded from BackgroundChild.
+  static void InitContentStarter(mozilla::dom::ContentChild* aContent);
+
+  // Forwarded from BackgroundChild.
+  static void InitSocketStarter(mozilla::net::SocketProcessChild* aSocket);
+
+  // Forwarded from BackgroundChild.
+  static void InitSocketBridgeStarter(
+      mozilla::net::SocketProcessBridgeChild* aSocketBridge);
+
+  static void ThreadLocalDestructor(void* aThreadLocal);
+
+  // This class is reference counted.
+  ~ChildImpl() { MOZ_ASSERT_IF(mActorWasAlive, mActorDestroyed); }
+
+  // Only called by IPDL.
+  virtual void ActorDestroy(ActorDestroyReason aWhy) override;
+};
+
+// -----------------------------------------------------------------------------
+// ParentImpl Helper Declarations
+// -----------------------------------------------------------------------------
+
+class ParentImpl::ShutdownObserver final : public nsIObserver {
+ public:
+  ShutdownObserver() { AssertIsOnMainThread(); }
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+ private:
+  ~ShutdownObserver() { AssertIsOnMainThread(); }
+};
+
+// -----------------------------------------------------------------------------
+// ChildImpl Helper Declarations
+// -----------------------------------------------------------------------------
+
+class ChildImpl::ShutdownObserver final : public nsIObserver {
+ public:
+  ShutdownObserver() { AssertIsOnMainThread(); }
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+ private:
+  ~ShutdownObserver() { AssertIsOnMainThread(); }
+};
+
+}  // namespace
+
+namespace mozilla {
+namespace ipc {
+
+bool IsOnBackgroundThread() { return ParentImpl::IsOnBackgroundThread(); }
+
+#ifdef DEBUG
+
+void AssertIsOnBackgroundThread() { ParentImpl::AssertIsOnBackgroundThread(); }
+
+#endif  // DEBUG
+
+}  // namespace ipc
+}  // namespace mozilla
+
+// -----------------------------------------------------------------------------
+// BackgroundParent Public Methods
+// -----------------------------------------------------------------------------
+
+// static
+bool BackgroundParent::IsOtherProcessActor(
+    PBackgroundParent* aBackgroundActor) {
+  return ParentImpl::IsOtherProcessActor(aBackgroundActor);
+}
+
+// static
+ThreadsafeContentParentHandle* BackgroundParent::GetContentParentHandle(
+    PBackgroundParent* aBackgroundActor) {
+  return ParentImpl::GetContentParentHandle(aBackgroundActor);
+}
+
+// static
+uint64_t BackgroundParent::GetChildID(PBackgroundParent* aBackgroundActor) {
+  return ParentImpl::GetChildID(aBackgroundActor);
+}
+
+// static
+bool BackgroundParent::AllocStarter(
+    ContentParent* aContent, Endpoint<PBackgroundStarterParent>&& aEndpoint) {
+  return ParentImpl::AllocStarter(aContent, std::move(aEndpoint));
+}
+
+// -----------------------------------------------------------------------------
+// BackgroundChild Public Methods
+// -----------------------------------------------------------------------------
+
+// static
+void BackgroundChild::Startup() { ChildImpl::Startup(); }
+
+// static
+PBackgroundChild* BackgroundChild::GetForCurrentThread() {
+  return ChildImpl::GetForCurrentThread();
+}
+
+// static
+PBackgroundChild* BackgroundChild::GetOrCreateForCurrentThread() {
+  return ChildImpl::GetOrCreateForCurrentThread();
+}
+
+// static
+PBackgroundChild* BackgroundChild::GetOrCreateSocketActorForCurrentThread() {
+  return ChildImpl::GetOrCreateSocketActorForCurrentThread();
+}
+
+// static
+PBackgroundChild*
+BackgroundChild::GetOrCreateForSocketParentBridgeForCurrentThread() {
+  return ChildImpl::GetOrCreateForSocketParentBridgeForCurrentThread();
+}
+
+// static
+void BackgroundChild::CloseForCurrentThread() {
+  ChildImpl::CloseForCurrentThread();
+}
+
+// static
+void BackgroundChild::InitContentStarter(ContentChild* aContent) {
+  ChildImpl::InitContentStarter(aContent);
+}
+
+// static
+void BackgroundChild::InitSocketStarter(net::SocketProcessChild* aSocket) {
+  ChildImpl::InitSocketStarter(aSocket);
+}
+
+// static
+void BackgroundChild::InitSocketBridgeStarter(
+    net::SocketProcessBridgeChild* aSocketBridge) {
+  ChildImpl::InitSocketBridgeStarter(aSocketBridge);
+}
+
+// -----------------------------------------------------------------------------
+// BackgroundChildImpl Public Methods
+// -----------------------------------------------------------------------------
+
+// static
+BackgroundChildImpl::ThreadLocal*
+BackgroundChildImpl::GetThreadLocalForCurrentThread() {
+  return ChildImpl::GetThreadLocalForCurrentThread();
+}
+
+// -----------------------------------------------------------------------------
+// ParentImpl Static Members
+// -----------------------------------------------------------------------------
+
+StaticRefPtr<nsIThread> ParentImpl::sBackgroundThread;
+
+nsTArray<IToplevelProtocol*>* ParentImpl::sLiveActorsForBackgroundThread;
+
+StaticRefPtr<nsITimer> ParentImpl::sShutdownTimer;
+
+Atomic<PRThread*> ParentImpl::sBackgroundPRThread;
+
+Atomic<uint64_t> ParentImpl::sLiveActorCount;
+
+bool ParentImpl::sShutdownObserverRegistered = false;
+
+bool ParentImpl::sShutdownHasStarted = false;
+
+// -----------------------------------------------------------------------------
+// ChildImpl Static Members
+// -----------------------------------------------------------------------------
+
+ChildImpl::ThreadInfoWrapper ChildImpl::sParentAndContentProcessThreadInfo;
+
+ChildImpl::ThreadInfoWrapper ChildImpl::sSocketAndContentProcessThreadInfo;
+
+ChildImpl::ThreadInfoWrapper ChildImpl::sSocketAndParentProcessThreadInfo;
+
+bool ChildImpl::sShutdownHasStarted = false;
+
+// -----------------------------------------------------------------------------
+// ParentImpl Implementation
+// -----------------------------------------------------------------------------
+
+// static
+bool ParentImpl::IsOtherProcessActor(PBackgroundParent* aBackgroundActor) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aBackgroundActor);
+
+  return static_cast<ParentImpl*>(aBackgroundActor)->mIsOtherProcessActor;
+}
+
+// static
+ThreadsafeContentParentHandle* ParentImpl::GetContentParentHandle(
+    PBackgroundParent* aBackgroundActor) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aBackgroundActor);
+
+  return static_cast<ParentImpl*>(aBackgroundActor)->mContent.get();
+}
+
+// static
+uint64_t ParentImpl::GetChildID(PBackgroundParent* aBackgroundActor) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aBackgroundActor);
+
+  auto actor = static_cast<ParentImpl*>(aBackgroundActor);
+  if (actor->mContent) {
+    return actor->mContent->ChildID();
+  }
+
+  return 0;
+}
+
+// static
+bool ParentImpl::AllocStarter(ContentParent* aContent,
+                              Endpoint<PBackgroundStarterParent>&& aEndpoint,
+                              bool aCrossProcess) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+
+  MOZ_ASSERT(aEndpoint.IsValid());
+
+  if (!sBackgroundThread && !CreateBackgroundThread()) {
+    NS_WARNING("Failed to create background thread!");
+    return false;
+  }
+
+  sLiveActorCount++;
+
+  RefPtr<BackgroundStarterParent> actor = new BackgroundStarterParent(
+      aContent ? aContent->ThreadsafeHandle() : nullptr, aCrossProcess);
+
+  if (NS_FAILED(sBackgroundThread->Dispatch(NS_NewRunnableFunction(
+          "BackgroundStarterParent::ConnectActorRunnable",
+          [actor = std::move(actor), endpoint = std::move(aEndpoint),
+           liveActorArray = sLiveActorsForBackgroundThread]() mutable {
+            MOZ_ASSERT(endpoint.IsValid());
+            MOZ_ALWAYS_TRUE(endpoint.Bind(actor));
+            actor->SetLiveActorArray(liveActorArray);
+          })))) {
+    NS_WARNING("Failed to dispatch connect runnable!");
+
+    MOZ_ASSERT(sLiveActorCount);
+    sLiveActorCount--;
+  }
+
+  return true;
+}
+
+// static
+bool ParentImpl::CreateBackgroundThread() {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+  MOZ_ASSERT(!sBackgroundThread);
+  MOZ_ASSERT(!sLiveActorsForBackgroundThread);
+
+  if (sShutdownHasStarted) {
+    NS_WARNING(
+        "Trying to create background thread after shutdown has "
+        "already begun!");
+    return false;
+  }
+
+  nsCOMPtr<nsITimer> newShutdownTimer;
+
+  if (!sShutdownTimer) {
+    newShutdownTimer = NS_NewTimer();
+    if (!newShutdownTimer) {
+      return false;
+    }
+  }
+
+  if (!sShutdownObserverRegistered) {
+    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+    if (NS_WARN_IF(!obs)) {
+      return false;
+    }
+
+    nsCOMPtr<nsIObserver> observer = new ShutdownObserver();
+
+    nsresult rv = obs->AddObserver(
+        observer, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID, false);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return false;
+    }
+
+    sShutdownObserverRegistered = true;
+  }
+
+  nsCOMPtr<nsIThread> thread;
+  if (NS_FAILED(NS_NewNamedThread(
+          "IPDL Background", getter_AddRefs(thread),
+          NS_NewRunnableFunction(
+              "Background::ParentImpl::CreateBackgroundThreadRunnable", []() {
+                DebugOnly<PRThread*> oldBackgroundThread =
+                    sBackgroundPRThread.exchange(PR_GetCurrentThread());
+
+                MOZ_ASSERT_IF(oldBackgroundThread,
+                              PR_GetCurrentThread() != oldBackgroundThread);
+              })))) {
+    NS_WARNING("NS_NewNamedThread failed!");
+    return false;
+  }
+
+  sBackgroundThread = thread.forget();
+
+  sLiveActorsForBackgroundThread = new nsTArray<IToplevelProtocol*>(1);
+
+  if (!sShutdownTimer) {
+    MOZ_ASSERT(newShutdownTimer);
+    sShutdownTimer = newShutdownTimer;
+  }
+
+  return true;
+}
+
+// static
+void ParentImpl::ShutdownBackgroundThread() {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+  MOZ_ASSERT(sShutdownHasStarted);
+  MOZ_ASSERT_IF(!sBackgroundThread, !sLiveActorCount);
+  MOZ_ASSERT_IF(sBackgroundThread, sShutdownTimer);
+
+  nsCOMPtr<nsITimer> shutdownTimer = sShutdownTimer.get();
+  sShutdownTimer = nullptr;
+
+  if (sBackgroundThread) {
+    nsCOMPtr<nsIThread> thread = sBackgroundThread.get();
+    sBackgroundThread = nullptr;
+
+    UniquePtr<nsTArray<IToplevelProtocol*>> liveActors(
+        sLiveActorsForBackgroundThread);
+    sLiveActorsForBackgroundThread = nullptr;
+
+    MOZ_ASSERT_IF(!sShutdownHasStarted, !sLiveActorCount);
+
+    if (sLiveActorCount) {
+      // We need to spin the event loop while we wait for all the actors to be
+      // cleaned up. We also set a timeout to force-kill any hanging actors.
+      TimerCallbackClosure closure(thread, liveActors.get());
+
+      MOZ_ALWAYS_SUCCEEDS(shutdownTimer->InitWithNamedFuncCallback(
+          &ShutdownTimerCallback, &closure, kShutdownTimerDelayMS,
+          nsITimer::TYPE_ONE_SHOT, "ParentImpl::ShutdownTimerCallback"));
+
+      SpinEventLoopUntil("ParentImpl::ShutdownBackgroundThread"_ns,
+                         [&]() { return !sLiveActorCount; });
+
+      MOZ_ASSERT(liveActors->IsEmpty());
+
+      MOZ_ALWAYS_SUCCEEDS(shutdownTimer->Cancel());
+    }
+
+    // Dispatch this runnable to unregister the PR thread from the profiler.
+    MOZ_ALWAYS_SUCCEEDS(thread->Dispatch(NS_NewRunnableFunction(
+        "Background::ParentImpl::ShutdownBackgroundThreadRunnable", []() {
+          // It is possible that another background thread was created while
+          // this thread was shutting down. In that case we can't assert
+          // anything about sBackgroundPRThread and we should not modify it
+          // here.
+          sBackgroundPRThread.compareExchange(PR_GetCurrentThread(), nullptr);
+        })));
+
+    MOZ_ALWAYS_SUCCEEDS(thread->Shutdown());
+  }
+}
+
+// static
+void ParentImpl::ShutdownTimerCallback(nsITimer* aTimer, void* aClosure) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+  MOZ_ASSERT(sShutdownHasStarted);
+  MOZ_ASSERT(sLiveActorCount);
+
+  auto closure = static_cast<TimerCallbackClosure*>(aClosure);
+  MOZ_ASSERT(closure);
+
+  // Don't let the stack unwind until the ForceCloseBackgroundActorsRunnable has
+  // finished.
+  sLiveActorCount++;
+
+  InvokeAsync(
+      closure->mThread, __func__,
+      [liveActors = closure->mLiveActors]() {
+        MOZ_ASSERT(liveActors);
+
+        if (!liveActors->IsEmpty()) {
+          // Copy the array since calling Close() could mutate the
+          // actual array.
+          nsTArray<IToplevelProtocol*> actorsToClose(liveActors->Clone());
+          for (IToplevelProtocol* actor : actorsToClose) {
+            actor->Close();
+          }
+        }
+        return GenericPromise::CreateAndResolve(true, __func__);
+      })
+      ->Then(GetCurrentSerialEventTarget(), __func__, []() {
+        MOZ_ASSERT(sLiveActorCount);
+        sLiveActorCount--;
+      });
+}
+
+void ParentImpl::Destroy() {
+  // May be called on any thread!
+
+  AssertIsInMainOrSocketProcess();
+
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(
+      NewNonOwningRunnableMethod("ParentImpl::MainThreadActorDestroy", this,
+                                 &ParentImpl::MainThreadActorDestroy)));
+}
+
+void ParentImpl::MainThreadActorDestroy() {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+  MOZ_ASSERT_IF(!mIsOtherProcessActor, !mContent);
+
+  MOZ_ASSERT(sLiveActorCount);
+  sLiveActorCount--;
+
+  // This may be the last reference!
+  Release();
+}
+
+void ParentImpl::ActorDestroy(ActorDestroyReason aWhy) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mActorDestroyed);
+  MOZ_ASSERT_IF(mIsOtherProcessActor, mLiveActorArray);
+
+  BackgroundParentImpl::ActorDestroy(aWhy);
+
+  mActorDestroyed = true;
+
+  if (mLiveActorArray) {
+    MOZ_ALWAYS_TRUE(mLiveActorArray->RemoveElement(this));
+    mLiveActorArray = nullptr;
+  }
+
+  // This is tricky. We should be able to call Destroy() here directly because
+  // we're not going to touch 'this' or our MessageChannel any longer on this
+  // thread. Destroy() dispatches the MainThreadActorDestroy runnable and when
+  // it runs it will destroy 'this' and our associated MessageChannel. However,
+  // IPDL is about to call MessageChannel::Clear() on this thread! To avoid
+  // racing with the main thread we must ensure that the MessageChannel lives
+  // long enough to be cleared in this call stack.
+
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchToCurrentThread(NewNonOwningRunnableMethod(
+      "ParentImpl::Destroy", this, &ParentImpl::Destroy)));
+}
+
+NS_IMPL_ISUPPORTS(ParentImpl::ShutdownObserver, nsIObserver)
+
+NS_IMETHODIMP
+ParentImpl::ShutdownObserver::Observe(nsISupports* aSubject, const char* aTopic,
+                                      const char16_t* aData) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+  MOZ_ASSERT(!sShutdownHasStarted);
+  MOZ_ASSERT(!strcmp(aTopic, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID));
+
+  sShutdownHasStarted = true;
+
+  // Do this first before calling (and spinning the event loop in)
+  // ShutdownBackgroundThread().
+  ChildImpl::Shutdown();
+
+  ShutdownBackgroundThread();
+
+  return NS_OK;
+}
+
+BackgroundStarterParent::BackgroundStarterParent(
+    ThreadsafeContentParentHandle* aContent, bool aCrossProcess)
+    : mCrossProcess(aCrossProcess), mContent(aContent) {
+  AssertIsOnMainThread();
+  AssertIsInMainOrSocketProcess();
+  MOZ_ASSERT_IF(!mCrossProcess, !mContent);
+  MOZ_ASSERT_IF(!mCrossProcess, XRE_IsParentProcess());
+}
+
+void BackgroundStarterParent::SetLiveActorArray(
+    nsTArray<IToplevelProtocol*>* aLiveActorArray) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aLiveActorArray);
+  MOZ_ASSERT(!aLiveActorArray->Contains(this));
+  MOZ_ASSERT(!mLiveActorArray);
+  MOZ_ASSERT_IF(!mCrossProcess, OtherPid() == base::GetCurrentProcId());
+
+  mLiveActorArray = aLiveActorArray;
+  mLiveActorArray->AppendElement(this);
+}
+
+IPCResult BackgroundStarterParent::RecvInitBackground(
+    Endpoint<PBackgroundParent>&& aEndpoint) {
+  AssertIsOnBackgroundThread();
+
+  if (!aEndpoint.IsValid()) {
+    return IPC_FAIL(this,
+                    "Cannot initialize PBackground with invalid endpoint");
+  }
+
+  ParentImpl* actor = new ParentImpl(mContent, mCrossProcess);
+
+  // Take a reference on this thread. If Open() fails then we will release this
+  // reference in Destroy.
+  NS_ADDREF(actor);
+
+  ParentImpl::sLiveActorCount++;
+
+  if (!aEndpoint.Bind(actor)) {
+    actor->Destroy();
+    return IPC_OK();
+  }
+
+  if (mCrossProcess) {
+    actor->SetLiveActorArray(mLiveActorArray);
+  }
+  return IPC_OK();
+}
+
+void BackgroundStarterParent::ActorDestroy(ActorDestroyReason aReason) {
+  AssertIsOnBackgroundThread();
+
+  if (mLiveActorArray) {
+    MOZ_ALWAYS_TRUE(mLiveActorArray->RemoveElement(this));
+    mLiveActorArray = nullptr;
+  }
+
+  // Make sure to decrement `sLiveActorCount` on the main thread.
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(
+      NS_NewRunnableFunction("BackgroundStarterParent::MainThreadDestroy",
+                             [] { ParentImpl::sLiveActorCount--; })));
+}
+
+// -----------------------------------------------------------------------------
+// ChildImpl Implementation
+// -----------------------------------------------------------------------------
+
+// static
+void ChildImpl::Startup() {
+  // This happens on the main thread but before XPCOM has started so we can't
+  // assert that we're being called on the main thread here.
+
+  sParentAndContentProcessThreadInfo.Startup();
+  sSocketAndContentProcessThreadInfo.Startup();
+  sSocketAndParentProcessThreadInfo.Startup();
+
+  nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
+  MOZ_RELEASE_ASSERT(observerService);
+
+  nsCOMPtr<nsIObserver> observer = new ShutdownObserver();
+
+  nsresult rv = observerService->AddObserver(
+      observer, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID, false);
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+
+  // Initialize a starter actor to allow starting PBackground within the parent
+  // process.
+  if (XRE_IsParentProcess()) {
+    Endpoint<PBackgroundStarterParent> parent;
+    Endpoint<PBackgroundStarterChild> child;
+    MOZ_ALWAYS_SUCCEEDS(PBackgroundStarter::CreateEndpoints(
+        base::GetCurrentProcId(), base::GetCurrentProcId(), &parent, &child));
+
+    MOZ_ALWAYS_TRUE(ParentImpl::AllocStarter(nullptr, std::move(parent),
+                                             /* aCrossProcess */ false));
+    sParentAndContentProcessThreadInfo.InitStarter(std::move(child));
+  }
+}
+
+// static
+void ChildImpl::Shutdown() {
+  AssertIsOnMainThread();
+
+  sParentAndContentProcessThreadInfo.Shutdown();
+  sSocketAndContentProcessThreadInfo.Shutdown();
+  sSocketAndParentProcessThreadInfo.Shutdown();
+
+  sShutdownHasStarted = true;
+}
+
+// static
+PBackgroundChild* ChildImpl::GetForCurrentThread() {
+  MOZ_ASSERT(sParentAndContentProcessThreadInfo.mThreadLocalIndex !=
+             kBadThreadLocalIndex);
+
+  auto threadLocalInfo =
+      NS_IsMainThread()
+          ? sParentAndContentProcessThreadInfo.mMainThreadInfo
+          : static_cast<ThreadLocalInfo*>(PR_GetThreadPrivate(
+                sParentAndContentProcessThreadInfo.mThreadLocalIndex));
+
+  if (!threadLocalInfo) {
+    return nullptr;
+  }
+
+  return threadLocalInfo->mActor;
+}
+
+/* static */
+PBackgroundChild* ChildImpl::GetOrCreateForCurrentThread() {
+  return sParentAndContentProcessThreadInfo.GetOrCreateForCurrentThread();
+}
+
+/* static */
+PBackgroundChild* ChildImpl::GetOrCreateSocketActorForCurrentThread() {
+  return sSocketAndContentProcessThreadInfo.GetOrCreateForCurrentThread();
+}
+
+/* static */
+PBackgroundChild*
+ChildImpl::GetOrCreateForSocketParentBridgeForCurrentThread() {
+  return sSocketAndParentProcessThreadInfo.GetOrCreateForCurrentThread();
+}
+
+// static
+void ChildImpl::CloseForCurrentThread() {
+  MOZ_ASSERT(!NS_IsMainThread(),
+             "PBackground for the main thread should be shut down via "
+             "ChildImpl::Shutdown().");
+
+  sParentAndContentProcessThreadInfo.CloseForCurrentThread();
+  sSocketAndContentProcessThreadInfo.CloseForCurrentThread();
+  sSocketAndParentProcessThreadInfo.CloseForCurrentThread();
+}
+
+// static
+BackgroundChildImpl::ThreadLocal* ChildImpl::GetThreadLocalForCurrentThread() {
+  MOZ_ASSERT(sParentAndContentProcessThreadInfo.mThreadLocalIndex !=
+                 kBadThreadLocalIndex,
+             "BackgroundChild::Startup() was never called!");
+
+  auto threadLocalInfo =
+      NS_IsMainThread()
+          ? sParentAndContentProcessThreadInfo.mMainThreadInfo
+          : static_cast<ThreadLocalInfo*>(PR_GetThreadPrivate(
+                sParentAndContentProcessThreadInfo.mThreadLocalIndex));
+
+  if (!threadLocalInfo) {
+    return nullptr;
+  }
+
+  if (!threadLocalInfo->mConsumerThreadLocal) {
+    threadLocalInfo->mConsumerThreadLocal =
+        MakeUnique<BackgroundChildImpl::ThreadLocal>();
+  }
+
+  return threadLocalInfo->mConsumerThreadLocal.get();
+}
+
+// static
+void ChildImpl::InitContentStarter(mozilla::dom::ContentChild* aContent) {
+  sParentAndContentProcessThreadInfo.InitStarter(aContent);
+}
+
+// static
+void ChildImpl::InitSocketStarter(mozilla::net::SocketProcessChild* aSocket) {
+  sSocketAndParentProcessThreadInfo.InitStarter(aSocket);
+}
+
+// static
+void ChildImpl::InitSocketBridgeStarter(
+    mozilla::net::SocketProcessBridgeChild* aSocketBridge) {
+  sSocketAndContentProcessThreadInfo.InitStarter(aSocketBridge);
+}
+
+// static
+void ChildImpl::ThreadLocalDestructor(void* aThreadLocal) {
+  auto threadLocalInfo = static_cast<ThreadLocalInfo*>(aThreadLocal);
+
+  if (threadLocalInfo) {
+    MOZ_ASSERT(threadLocalInfo->mClosed);
+
+    if (threadLocalInfo->mActor) {
+      threadLocalInfo->mActor->Close();
+      threadLocalInfo->mActor->AssertActorDestroyed();
+    }
+
+    delete threadLocalInfo;
+  }
+}
+
+void ChildImpl::ActorDestroy(ActorDestroyReason aWhy) {
+  AssertIsOnOwningThread();
+
+#ifdef DEBUG
+  MOZ_ASSERT(!mActorDestroyed);
+  mActorDestroyed = true;
+#endif
+
+  BackgroundChildImpl::ActorDestroy(aWhy);
+}
+
+NS_IMPL_ISUPPORTS(ChildImpl::ShutdownObserver, nsIObserver)
+
+NS_IMETHODIMP
+ChildImpl::ShutdownObserver::Observe(nsISupports* aSubject, const char* aTopic,
+                                     const char16_t* aData) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(!strcmp(aTopic, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID));
+
+  ChildImpl::Shutdown();
+
+  return NS_OK;
+}
diff --git a/ipc/glue/BackgroundParent.h b/ipc/glue/BackgroundParent.h
new file mode 100644
index 0000000000..650cf2ea29
--- /dev/null
+++ b/ipc/glue/BackgroundParent.h
@@ -0,0 +1,113 @@
+/* -*- 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_ipc_backgroundparent_h__
+#define mozilla_ipc_backgroundparent_h__
+
+#include "base/process.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/ContentParent.h"
+#include "nsStringFwd.h"
+#include "nsTArrayForwardDeclare.h"
+
+#ifdef DEBUG
+#  include "nsXULAppAPI.h"
+#endif
+
+template <class>
+struct already_AddRefed;
+
+namespace mozilla {
+
+namespace net {
+
+class SocketProcessBridgeParent;
+class SocketProcessParent;
+
+}  // namespace net
+
+namespace dom {
+
+class BlobImpl;
+class ContentParent;
+
+}  // namespace dom
+
+namespace ipc {
+
+class BackgroundStarterParent;
+class PBackgroundParent;
+class PBackgroundStarterParent;
+
+template <class PFooSide>
+class Endpoint;
+
+// This class is not designed for public consumption beyond the few static
+// member functions.
+class BackgroundParent final {
+  friend class mozilla::ipc::BackgroundStarterParent;
+  friend class mozilla::dom::ContentParent;
+  friend class mozilla::net::SocketProcessBridgeParent;
+  friend class mozilla::net::SocketProcessParent;
+
+  using ProcessId = base::ProcessId;
+  using BlobImpl = mozilla::dom::BlobImpl;
+  using ContentParent = mozilla::dom::ContentParent;
+  using ThreadsafeContentParentHandle =
+      mozilla::dom::ThreadsafeContentParentHandle;
+
+ public:
+  // This function allows the caller to determine if the given parent actor
+  // corresponds to a child actor from another process or a child actor from a
+  // different thread in the same process.
+  // This function may only be called on the background thread.
+  static bool IsOtherProcessActor(PBackgroundParent* aBackgroundActor);
+
+  // This function returns a handle to the ContentParent associated with the
+  // parent actor if the parent actor corresponds to a child actor from another
+  // content process. If the parent actor corresponds to a child actor from a
+  // different thread in the same process then this function returns null.
+  //
+  // This function may only be called on the background thread.
+  static ThreadsafeContentParentHandle* GetContentParentHandle(
+      PBackgroundParent* aBackgroundActor);
+
+  static uint64_t GetChildID(PBackgroundParent* aBackgroundActor);
+
+ private:
+  // Only called by ContentParent for cross-process actors.
+  static bool AllocStarter(ContentParent* aContent,
+                           Endpoint<PBackgroundStarterParent>&& aEndpoint);
+
+  // Called by SocketProcessBridgeParent and SocketProcessParent for
+  // cross-process actors.
+  static bool AllocStarter(Endpoint<PBackgroundStarterParent>&& aEndpoint);
+};
+
+// Implemented in BackgroundImpl.cpp.
+bool IsOnBackgroundThread();
+
+#ifdef DEBUG
+
+// Implemented in BackgroundImpl.cpp.
+void AssertIsOnBackgroundThread();
+
+#else
+
+inline void AssertIsOnBackgroundThread() {}
+
+#endif  // DEBUG
+
+inline void AssertIsInMainProcess() { MOZ_ASSERT(XRE_IsParentProcess()); }
+
+inline void AssertIsInMainOrSocketProcess() {
+  MOZ_ASSERT(XRE_IsParentProcess() || XRE_IsSocketProcess());
+}
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_backgroundparent_h__
diff --git a/ipc/glue/BackgroundParentImpl.cpp b/ipc/glue/BackgroundParentImpl.cpp
new file mode 100644
index 0000000000..9baa44488a
--- /dev/null
+++ b/ipc/glue/BackgroundParentImpl.cpp
@@ -0,0 +1,1893 @@
+/* -*- 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 "BackgroundParentImpl.h"
+
+#include "BroadcastChannelParent.h"
+#ifdef MOZ_WEBRTC
+#  include "CamerasParent.h"
+#endif
+#include "mozilla/Assertions.h"
+#include "mozilla/RDDProcessManager.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "mozilla/RemoteDecodeUtils.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/BackgroundSessionStorageServiceParent.h"
+#include "mozilla/dom/ClientManagerActors.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/DOMTypes.h"
+#include "mozilla/dom/EndpointForReportParent.h"
+#include "mozilla/dom/FetchParent.h"
+#include "mozilla/dom/FileCreatorParent.h"
+#include "mozilla/dom/FileSystemManagerParentFactory.h"
+#include "mozilla/dom/FileSystemRequestParent.h"
+#include "mozilla/dom/GamepadEventChannelParent.h"
+#include "mozilla/dom/GamepadTestChannelParent.h"
+#include "mozilla/dom/MIDIManagerParent.h"
+#include "mozilla/dom/MIDIPlatformService.h"
+#include "mozilla/dom/MIDIPortParent.h"
+#include "mozilla/dom/MediaTransportParent.h"
+#include "mozilla/dom/MessagePortParent.h"
+#include "mozilla/dom/PGamepadEventChannelParent.h"
+#include "mozilla/dom/PGamepadTestChannelParent.h"
+#include "mozilla/dom/RemoteWorkerControllerParent.h"
+#include "mozilla/dom/RemoteWorkerServiceParent.h"
+#include "mozilla/dom/ReportingHeader.h"
+#include "mozilla/dom/ServiceWorkerActors.h"
+#include "mozilla/dom/ServiceWorkerContainerParent.h"
+#include "mozilla/dom/ServiceWorkerManagerParent.h"
+#include "mozilla/dom/ServiceWorkerParent.h"
+#include "mozilla/dom/ServiceWorkerRegistrar.h"
+#include "mozilla/dom/ServiceWorkerRegistrationParent.h"
+#include "mozilla/dom/SessionStorageManager.h"
+#include "mozilla/dom/SharedWorkerParent.h"
+#include "mozilla/dom/StorageActivityService.h"
+#include "mozilla/dom/StorageIPC.h"
+#include "mozilla/dom/TemporaryIPCBlobParent.h"
+#include "mozilla/dom/WebAuthnTransactionParent.h"
+#include "mozilla/dom/WebTransportParent.h"
+#include "mozilla/dom/cache/ActorUtils.h"
+#include "mozilla/dom/indexedDB/ActorsParent.h"
+#include "mozilla/dom/locks/LockManagerParent.h"
+#include "mozilla/dom/localstorage/ActorsParent.h"
+#include "mozilla/dom/network/UDPSocketParent.h"
+#include "mozilla/dom/quota/ActorsParent.h"
+#include "mozilla/dom/simpledb/ActorsParent.h"
+#include "mozilla/dom/VsyncParent.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/IdleSchedulerParent.h"
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+#include "mozilla/ipc/PBackgroundTestParent.h"
+#include "mozilla/net/BackgroundDataBridgeParent.h"
+#include "mozilla/net/HttpBackgroundChannelParent.h"
+#include "mozilla/net/HttpConnectionMgrParent.h"
+#include "mozilla/net/WebSocketConnectionParent.h"
+#include "mozilla/psm/IPCClientCertsParent.h"
+#include "mozilla/psm/SelectTLSClientAuthCertParent.h"
+#include "mozilla/psm/VerifySSLServerCertParent.h"
+#include "nsIHttpChannelInternal.h"
+#include "nsIPrincipal.h"
+#include "nsProxyRelease.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+using mozilla::AssertIsOnMainThread;
+using mozilla::dom::FileSystemRequestParent;
+using mozilla::dom::MessagePortParent;
+using mozilla::dom::MIDIManagerParent;
+using mozilla::dom::MIDIPlatformService;
+using mozilla::dom::MIDIPortParent;
+using mozilla::dom::PMessagePortParent;
+using mozilla::dom::PMIDIManagerParent;
+using mozilla::dom::PMIDIPortParent;
+using mozilla::dom::PServiceWorkerContainerParent;
+using mozilla::dom::PServiceWorkerParent;
+using mozilla::dom::PServiceWorkerRegistrationParent;
+using mozilla::dom::ServiceWorkerParent;
+using mozilla::dom::UDPSocketParent;
+using mozilla::dom::WebAuthnTransactionParent;
+using mozilla::dom::cache::PCacheParent;
+using mozilla::dom::cache::PCacheStorageParent;
+using mozilla::dom::cache::PCacheStreamControlParent;
+using mozilla::ipc::AssertIsOnBackgroundThread;
+
+namespace {
+
+class TestParent final : public mozilla::ipc::PBackgroundTestParent {
+  friend class mozilla::ipc::BackgroundParentImpl;
+
+  MOZ_COUNTED_DEFAULT_CTOR(TestParent)
+
+ protected:
+  ~TestParent() override { MOZ_COUNT_DTOR(TestParent); }
+
+ public:
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+};
+
+}  // namespace
+
+namespace mozilla::ipc {
+
+using mozilla::dom::BroadcastChannelParent;
+using mozilla::dom::ContentParent;
+using mozilla::dom::ThreadsafeContentParentHandle;
+
+// A PBackgroundParent is a normal "content" actor if both the parent
+// side lives in the parent process and it either connects in-process, or
+// to a content process.
+static bool IsContentActor(PBackgroundParent* aActor) {
+  return XRE_IsParentProcess() &&
+         (!BackgroundParent::IsOtherProcessActor(aActor) ||
+          BackgroundParent::GetContentParentHandle(aActor));
+}
+
+// The parent side of socket bridge actors is always in the socket process.
+static bool IsSocketBridgeActor(PBackgroundParent* aActor) {
+  return XRE_IsSocketProcess();
+}
+
+// The parent side of socket actors is the parent process, and it must
+// not have a content process.
+static bool IsSocketActor(PBackgroundParent* aActor) {
+  return XRE_IsParentProcess() && !IsContentActor(aActor);
+}
+
+BackgroundParentImpl::BackgroundParentImpl() {
+  AssertIsInMainOrSocketProcess();
+
+  MOZ_COUNT_CTOR(mozilla::ipc::BackgroundParentImpl);
+}
+
+BackgroundParentImpl::~BackgroundParentImpl() {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnMainThread();
+
+  MOZ_COUNT_DTOR(mozilla::ipc::BackgroundParentImpl);
+}
+
+void BackgroundParentImpl::ActorDestroy(ActorDestroyReason aWhy) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+}
+
+already_AddRefed<net::PBackgroundDataBridgeParent>
+BackgroundParentImpl::AllocPBackgroundDataBridgeParent(
+    const uint64_t& aChannelID) {
+  if (!IsSocketBridgeActor(this)) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(XRE_IsSocketProcess(), "Should be in socket process");
+  AssertIsOnBackgroundThread();
+
+  RefPtr<net::BackgroundDataBridgeParent> actor =
+      new net::BackgroundDataBridgeParent(aChannelID);
+  return actor.forget();
+}
+
+BackgroundParentImpl::PBackgroundTestParent*
+BackgroundParentImpl::AllocPBackgroundTestParent(const nsACString& aTestArg) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return new TestParent();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPBackgroundTestConstructor(
+    PBackgroundTestParent* aActor, const nsACString& aTestArg) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!PBackgroundTestParent::Send__delete__(aActor, aTestArg)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundTestParent(
+    PBackgroundTestParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  delete static_cast<TestParent*>(aActor);
+  return true;
+}
+
+auto BackgroundParentImpl::AllocPBackgroundIDBFactoryParent(
+    const LoggingInfo& aLoggingInfo)
+    -> already_AddRefed<PBackgroundIDBFactoryParent> {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  using mozilla::dom::indexedDB::AllocPBackgroundIDBFactoryParent;
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return AllocPBackgroundIDBFactoryParent(aLoggingInfo);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundIDBFactoryConstructor(
+    PBackgroundIDBFactoryParent* aActor, const LoggingInfo& aLoggingInfo) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  using mozilla::dom::indexedDB::RecvPBackgroundIDBFactoryConstructor;
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!RecvPBackgroundIDBFactoryConstructor(aActor, aLoggingInfo)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+auto BackgroundParentImpl::AllocPBackgroundIndexedDBUtilsParent()
+    -> PBackgroundIndexedDBUtilsParent* {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::indexedDB::AllocPBackgroundIndexedDBUtilsParent();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundIndexedDBUtilsParent(
+    PBackgroundIndexedDBUtilsParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::indexedDB::DeallocPBackgroundIndexedDBUtilsParent(
+      aActor);
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvFlushPendingFileDeletions() {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (!mozilla::dom::indexedDB::RecvFlushPendingFileDeletions()) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+BackgroundParentImpl::PBackgroundSDBConnectionParent*
+BackgroundParentImpl::AllocPBackgroundSDBConnectionParent(
+    const PersistenceType& aPersistenceType,
+    const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundSDBConnectionParent(aPersistenceType,
+                                                           aPrincipalInfo);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundSDBConnectionConstructor(
+    PBackgroundSDBConnectionParent* aActor,
+    const PersistenceType& aPersistenceType,
+    const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!mozilla::dom::RecvPBackgroundSDBConnectionConstructor(
+          aActor, aPersistenceType, aPrincipalInfo)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundSDBConnectionParent(
+    PBackgroundSDBConnectionParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundSDBConnectionParent(aActor);
+}
+
+BackgroundParentImpl::PBackgroundLSDatabaseParent*
+BackgroundParentImpl::AllocPBackgroundLSDatabaseParent(
+    const PrincipalInfo& aPrincipalInfo, const uint32_t& aPrivateBrowsingId,
+    const uint64_t& aDatastoreId) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundLSDatabaseParent(
+      aPrincipalInfo, aPrivateBrowsingId, aDatastoreId);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundLSDatabaseConstructor(
+    PBackgroundLSDatabaseParent* aActor, const PrincipalInfo& aPrincipalInfo,
+    const uint32_t& aPrivateBrowsingId, const uint64_t& aDatastoreId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!mozilla::dom::RecvPBackgroundLSDatabaseConstructor(
+          aActor, aPrincipalInfo, aPrivateBrowsingId, aDatastoreId)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundLSDatabaseParent(
+    PBackgroundLSDatabaseParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundLSDatabaseParent(aActor);
+}
+
+BackgroundParentImpl::PBackgroundLSObserverParent*
+BackgroundParentImpl::AllocPBackgroundLSObserverParent(
+    const uint64_t& aObserverId) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundLSObserverParent(aObserverId);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundLSObserverConstructor(
+    PBackgroundLSObserverParent* aActor, const uint64_t& aObserverId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!mozilla::dom::RecvPBackgroundLSObserverConstructor(aActor,
+                                                          aObserverId)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundLSObserverParent(
+    PBackgroundLSObserverParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundLSObserverParent(aActor);
+}
+
+BackgroundParentImpl::PBackgroundLSRequestParent*
+BackgroundParentImpl::AllocPBackgroundLSRequestParent(
+    const LSRequestParams& aParams) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundLSRequestParent(this, aParams);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundLSRequestConstructor(
+    PBackgroundLSRequestParent* aActor, const LSRequestParams& aParams) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!mozilla::dom::RecvPBackgroundLSRequestConstructor(aActor, aParams)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundLSRequestParent(
+    PBackgroundLSRequestParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundLSRequestParent(aActor);
+}
+
+BackgroundParentImpl::PBackgroundLSSimpleRequestParent*
+BackgroundParentImpl::AllocPBackgroundLSSimpleRequestParent(
+    const LSSimpleRequestParams& aParams) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundLSSimpleRequestParent(this, aParams);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundLSSimpleRequestConstructor(
+    PBackgroundLSSimpleRequestParent* aActor,
+    const LSSimpleRequestParams& aParams) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!mozilla::dom::RecvPBackgroundLSSimpleRequestConstructor(aActor,
+                                                               aParams)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundLSSimpleRequestParent(
+    PBackgroundLSSimpleRequestParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundLSSimpleRequestParent(aActor);
+}
+
+BackgroundParentImpl::PBackgroundLocalStorageCacheParent*
+BackgroundParentImpl::AllocPBackgroundLocalStorageCacheParent(
+    const PrincipalInfo& aPrincipalInfo, const nsACString& aOriginKey,
+    const uint32_t& aPrivateBrowsingId) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundLocalStorageCacheParent(
+      aPrincipalInfo, aOriginKey, aPrivateBrowsingId);
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPBackgroundLocalStorageCacheConstructor(
+    PBackgroundLocalStorageCacheParent* aActor,
+    const PrincipalInfo& aPrincipalInfo, const nsACString& aOriginKey,
+    const uint32_t& aPrivateBrowsingId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::RecvPBackgroundLocalStorageCacheConstructor(
+      this, aActor, aPrincipalInfo, aOriginKey, aPrivateBrowsingId);
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundLocalStorageCacheParent(
+    PBackgroundLocalStorageCacheParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundLocalStorageCacheParent(aActor);
+}
+
+auto BackgroundParentImpl::AllocPBackgroundStorageParent(
+    const nsAString& aProfilePath, const uint32_t& aPrivateBrowsingId)
+    -> PBackgroundStorageParent* {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::AllocPBackgroundStorageParent(aProfilePath,
+                                                     aPrivateBrowsingId);
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPBackgroundStorageConstructor(
+    PBackgroundStorageParent* aActor, const nsAString& aProfilePath,
+    const uint32_t& aPrivateBrowsingId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::RecvPBackgroundStorageConstructor(aActor, aProfilePath,
+                                                         aPrivateBrowsingId);
+}
+
+bool BackgroundParentImpl::DeallocPBackgroundStorageParent(
+    PBackgroundStorageParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::DeallocPBackgroundStorageParent(aActor);
+}
+
+already_AddRefed<BackgroundParentImpl::PBackgroundSessionStorageManagerParent>
+BackgroundParentImpl::AllocPBackgroundSessionStorageManagerParent(
+    const uint64_t& aTopContextId) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return dom::AllocPBackgroundSessionStorageManagerParent(aTopContextId);
+}
+
+already_AddRefed<mozilla::dom::PBackgroundSessionStorageServiceParent>
+BackgroundParentImpl::AllocPBackgroundSessionStorageServiceParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return MakeAndAddRef<mozilla::dom::BackgroundSessionStorageServiceParent>();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvCreateFileSystemManagerParent(
+    const PrincipalInfo& aPrincipalInfo,
+    Endpoint<PFileSystemManagerParent>&& aParentEndpoint,
+    CreateFileSystemManagerParentResolver&& aResolver) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::CreateFileSystemManagerParent(
+      aPrincipalInfo, std::move(aParentEndpoint), std::move(aResolver));
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvCreateWebTransportParent(
+    const nsAString& aURL, nsIPrincipal* aPrincipal,
+    const mozilla::Maybe<IPCClientInfo>& aClientInfo, const bool& aDedicated,
+    const bool& aRequireUnreliable, const uint32_t& aCongestionControl,
+    // Sequence<WebTransportHash>* aServerCertHashes,
+    Endpoint<PWebTransportParent>&& aParentEndpoint,
+    CreateWebTransportParentResolver&& aResolver) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  RefPtr<mozilla::dom::WebTransportParent> webt =
+      new mozilla::dom::WebTransportParent();
+  webt->Create(aURL, aPrincipal, aClientInfo, aDedicated, aRequireUnreliable,
+               aCongestionControl,
+               /*aServerCertHashes, */ std::move(aParentEndpoint),
+               std::move(aResolver));
+  return IPC_OK();
+}
+
+already_AddRefed<PIdleSchedulerParent>
+BackgroundParentImpl::AllocPIdleSchedulerParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsOnBackgroundThread();
+  RefPtr<IdleSchedulerParent> actor = new IdleSchedulerParent();
+  return actor.forget();
+}
+
+dom::PRemoteWorkerControllerParent*
+BackgroundParentImpl::AllocPRemoteWorkerControllerParent(
+    const dom::RemoteWorkerData& aRemoteWorkerData) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<dom::RemoteWorkerControllerParent> actor =
+      new dom::RemoteWorkerControllerParent(aRemoteWorkerData);
+  return actor.forget().take();
+}
+
+IPCResult BackgroundParentImpl::RecvPRemoteWorkerControllerConstructor(
+    dom::PRemoteWorkerControllerParent* aActor,
+    const dom::RemoteWorkerData& aRemoteWorkerData) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  MOZ_ASSERT(aActor);
+
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPRemoteWorkerControllerParent(
+    dom::PRemoteWorkerControllerParent* aActor) {
+  RefPtr<dom::RemoteWorkerControllerParent> actor =
+      dont_AddRef(static_cast<dom::RemoteWorkerControllerParent*>(aActor));
+  return true;
+}
+
+already_AddRefed<dom::PRemoteWorkerServiceParent>
+BackgroundParentImpl::AllocPRemoteWorkerServiceParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<dom::RemoteWorkerServiceParent>();
+}
+
+IPCResult BackgroundParentImpl::RecvPRemoteWorkerServiceConstructor(
+    PRemoteWorkerServiceParent* aActor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  mozilla::dom::RemoteWorkerServiceParent* actor =
+      static_cast<mozilla::dom::RemoteWorkerServiceParent*>(aActor);
+
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(this);
+  // If the ContentParent is null we are dealing with a same-process actor.
+  if (!parent) {
+    actor->Initialize(NOT_REMOTE_TYPE);
+  } else {
+    actor->Initialize(parent->GetRemoteType());
+  }
+  return IPC_OK();
+}
+
+mozilla::dom::PSharedWorkerParent*
+BackgroundParentImpl::AllocPSharedWorkerParent(
+    const mozilla::dom::RemoteWorkerData& aData, const uint64_t& aWindowID,
+    const mozilla::dom::MessagePortIdentifier& aPortIdentifier) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<dom::SharedWorkerParent> agent =
+      new mozilla::dom::SharedWorkerParent();
+  return agent.forget().take();
+}
+
+IPCResult BackgroundParentImpl::RecvPSharedWorkerConstructor(
+    PSharedWorkerParent* aActor, const mozilla::dom::RemoteWorkerData& aData,
+    const uint64_t& aWindowID,
+    const mozilla::dom::MessagePortIdentifier& aPortIdentifier) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  mozilla::dom::SharedWorkerParent* actor =
+      static_cast<mozilla::dom::SharedWorkerParent*>(aActor);
+  actor->Initialize(aData, aWindowID, aPortIdentifier);
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPSharedWorkerParent(
+    mozilla::dom::PSharedWorkerParent* aActor) {
+  RefPtr<mozilla::dom::SharedWorkerParent> actor =
+      dont_AddRef(static_cast<mozilla::dom::SharedWorkerParent*>(aActor));
+  return true;
+}
+
+dom::PFileCreatorParent* BackgroundParentImpl::AllocPFileCreatorParent(
+    const nsAString& aFullPath, const nsAString& aType, const nsAString& aName,
+    const Maybe<int64_t>& aLastModified, const bool& aExistenceCheck,
+    const bool& aIsFromNsIFile) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<dom::FileCreatorParent> actor = new dom::FileCreatorParent();
+  return actor.forget().take();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPFileCreatorConstructor(
+    dom::PFileCreatorParent* aActor, const nsAString& aFullPath,
+    const nsAString& aType, const nsAString& aName,
+    const Maybe<int64_t>& aLastModified, const bool& aExistenceCheck,
+    const bool& aIsFromNsIFile) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  bool isFileRemoteType = false;
+
+  // If the ContentParentHandle is null we are dealing with a same-process
+  // actor.
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(this);
+  if (!parent) {
+    isFileRemoteType = true;
+  } else {
+    isFileRemoteType = parent->GetRemoteType() == FILE_REMOTE_TYPE;
+  }
+
+  dom::FileCreatorParent* actor = static_cast<dom::FileCreatorParent*>(aActor);
+
+  // We allow the creation of File via this IPC call only for the 'file' process
+  // or for testing.
+  if (!isFileRemoteType && !StaticPrefs::dom_file_createInChild()) {
+    Unused << dom::FileCreatorParent::Send__delete__(
+        actor, dom::FileCreationErrorResult(NS_ERROR_DOM_INVALID_STATE_ERR));
+    return IPC_OK();
+  }
+
+  return actor->CreateAndShareFile(aFullPath, aType, aName, aLastModified,
+                                   aExistenceCheck, aIsFromNsIFile);
+}
+
+bool BackgroundParentImpl::DeallocPFileCreatorParent(
+    dom::PFileCreatorParent* aActor) {
+  RefPtr<dom::FileCreatorParent> actor =
+      dont_AddRef(static_cast<dom::FileCreatorParent*>(aActor));
+  return true;
+}
+
+dom::PTemporaryIPCBlobParent*
+BackgroundParentImpl::AllocPTemporaryIPCBlobParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return new dom::TemporaryIPCBlobParent();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPTemporaryIPCBlobConstructor(
+    dom::PTemporaryIPCBlobParent* aActor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  dom::TemporaryIPCBlobParent* actor =
+      static_cast<dom::TemporaryIPCBlobParent*>(aActor);
+  return actor->CreateAndShareFile();
+}
+
+bool BackgroundParentImpl::DeallocPTemporaryIPCBlobParent(
+    dom::PTemporaryIPCBlobParent* aActor) {
+  delete aActor;
+  return true;
+}
+
+already_AddRefed<BackgroundParentImpl::PVsyncParent>
+BackgroundParentImpl::AllocPVsyncParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  RefPtr<mozilla::dom::VsyncParent> actor = new mozilla::dom::VsyncParent();
+
+  RefPtr<mozilla::VsyncDispatcher> vsyncDispatcher =
+      gfxPlatform::GetPlatform()->GetGlobalVsyncDispatcher();
+  actor->UpdateVsyncDispatcher(vsyncDispatcher);
+  return actor.forget();
+}
+
+camera::PCamerasParent* BackgroundParentImpl::AllocPCamerasParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+#ifdef MOZ_WEBRTC
+  RefPtr<mozilla::camera::CamerasParent> actor =
+      mozilla::camera::CamerasParent::Create();
+  return actor.forget().take();
+#else
+  return nullptr;
+#endif
+}
+
+#ifdef MOZ_WEBRTC
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPCamerasConstructor(
+    camera::PCamerasParent* aActor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+  return static_cast<camera::CamerasParent*>(aActor)->RecvPCamerasConstructor();
+}
+#endif
+
+bool BackgroundParentImpl::DeallocPCamerasParent(
+    camera::PCamerasParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+#ifdef MOZ_WEBRTC
+  RefPtr<mozilla::camera::CamerasParent> actor =
+      dont_AddRef(static_cast<mozilla::camera::CamerasParent*>(aActor));
+#endif
+  return true;
+}
+
+auto BackgroundParentImpl::AllocPUDPSocketParent(
+    const Maybe<PrincipalInfo>& /* unused */, const nsACString& /* unused */)
+    -> PUDPSocketParent* {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<UDPSocketParent> p = new UDPSocketParent(this);
+
+  return p.forget().take();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPUDPSocketConstructor(
+    PUDPSocketParent* aActor, const Maybe<PrincipalInfo>& aOptionalPrincipal,
+    const nsACString& aFilter) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (aOptionalPrincipal.isSome()) {
+    // Support for checking principals (for non-mtransport use) will be handled
+    // in bug 1167039
+    return IPC_FAIL_NO_REASON(this);
+  }
+  // No principal - This must be from mtransport (WebRTC/ICE) - We'd want
+  // to DispatchToMainThread() here, but if we do we must block RecvBind()
+  // until Init() gets run.  Since we don't have a principal, and we verify
+  // we have a filter, we can safely skip the Dispatch and just invoke Init()
+  // to install the filter.
+
+  // For mtransport, this will always be "stun", which doesn't allow outbound
+  // packets if they aren't STUN packets until a STUN response is seen.
+  if (!aFilter.EqualsASCII(NS_NETWORK_SOCKET_FILTER_HANDLER_STUN_SUFFIX)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  if (!static_cast<UDPSocketParent*>(aActor)->Init(nullptr, aFilter)) {
+    MOZ_CRASH("UDPSocketCallback - failed init");
+  }
+
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPUDPSocketParent(PUDPSocketParent* actor) {
+  UDPSocketParent* p = static_cast<UDPSocketParent*>(actor);
+  p->Release();
+  return true;
+}
+
+already_AddRefed<mozilla::psm::PVerifySSLServerCertParent>
+BackgroundParentImpl::AllocPVerifySSLServerCertParent(
+    const nsTArray<ByteArray>& aPeerCertChain, const nsACString& aHostName,
+    const int32_t& aPort, const OriginAttributes& aOriginAttributes,
+    const Maybe<ByteArray>& aStapledOCSPResponse,
+    const Maybe<ByteArray>& aSctsFromTLSExtension,
+    const Maybe<DelegatedCredentialInfoArg>& aDcInfo,
+    const uint32_t& aProviderFlags, const uint32_t& aCertVerifierFlags) {
+  if (!IsSocketActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<mozilla::psm::VerifySSLServerCertParent> parent =
+      new mozilla::psm::VerifySSLServerCertParent();
+  return parent.forget();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPVerifySSLServerCertConstructor(
+    PVerifySSLServerCertParent* aActor, nsTArray<ByteArray>&& aPeerCertChain,
+    const nsACString& aHostName, const int32_t& aPort,
+    const OriginAttributes& aOriginAttributes,
+    const Maybe<ByteArray>& aStapledOCSPResponse,
+    const Maybe<ByteArray>& aSctsFromTLSExtension,
+    const Maybe<DelegatedCredentialInfoArg>& aDcInfo,
+    const uint32_t& aProviderFlags, const uint32_t& aCertVerifierFlags) {
+  if (!IsSocketActor(this)) {
+    return IPC_FAIL(this, "must be a socket actor");
+  }
+
+  mozilla::psm::VerifySSLServerCertParent* authCert =
+      static_cast<mozilla::psm::VerifySSLServerCertParent*>(aActor);
+  if (!authCert->Dispatch(std::move(aPeerCertChain), aHostName, aPort,
+                          aOriginAttributes, aStapledOCSPResponse,
+                          aSctsFromTLSExtension, aDcInfo, aProviderFlags,
+                          aCertVerifierFlags)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+already_AddRefed<mozilla::psm::PSelectTLSClientAuthCertParent>
+BackgroundParentImpl::AllocPSelectTLSClientAuthCertParent(
+    const nsACString& aHostName, const OriginAttributes& aOriginAttributes,
+    const int32_t& aPort, const uint32_t& aProviderFlags,
+    const uint32_t& aProviderTlsFlags, const ByteArray& aServerCertBytes,
+    const nsTArray<ByteArray>& aCANames) {
+  if (!IsSocketActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<mozilla::psm::SelectTLSClientAuthCertParent> parent =
+      new mozilla::psm::SelectTLSClientAuthCertParent();
+  return parent.forget();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPSelectTLSClientAuthCertConstructor(
+    PSelectTLSClientAuthCertParent* actor, const nsACString& aHostName,
+    const OriginAttributes& aOriginAttributes, const int32_t& aPort,
+    const uint32_t& aProviderFlags, const uint32_t& aProviderTlsFlags,
+    const ByteArray& aServerCertBytes, nsTArray<ByteArray>&& aCANames) {
+  if (!IsSocketActor(this)) {
+    return IPC_FAIL(this, "must be a socket actor");
+  }
+
+  mozilla::psm::SelectTLSClientAuthCertParent* selectTLSClientAuthCertParent =
+      static_cast<mozilla::psm::SelectTLSClientAuthCertParent*>(actor);
+  if (!selectTLSClientAuthCertParent->Dispatch(
+          aHostName, aOriginAttributes, aPort, aProviderFlags,
+          aProviderTlsFlags, aServerCertBytes, std::move(aCANames))) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::dom::PBroadcastChannelParent*
+BackgroundParentImpl::AllocPBroadcastChannelParent(
+    const PrincipalInfo& aPrincipalInfo, const nsACString& aOrigin,
+    const nsAString& aChannel) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  nsString originChannelKey;
+
+  // The format of originChannelKey is:
+  //  <channelName>|<origin+OriginAttributes>
+
+  originChannelKey.Assign(aChannel);
+
+  originChannelKey.AppendLiteral("|");
+
+  originChannelKey.Append(NS_ConvertUTF8toUTF16(aOrigin));
+
+  return new BroadcastChannelParent(originChannelKey);
+}
+
+namespace {
+
+class CheckPrincipalRunnable final : public Runnable {
+ public:
+  CheckPrincipalRunnable(
+      already_AddRefed<ThreadsafeContentParentHandle> aParent,
+      const PrincipalInfo& aPrincipalInfo, const nsACString& aOrigin)
+      : Runnable("ipc::CheckPrincipalRunnable"),
+        mContentParent(aParent),
+        mPrincipalInfo(aPrincipalInfo),
+        mOrigin(aOrigin) {
+    AssertIsInMainOrSocketProcess();
+    AssertIsOnBackgroundThread();
+
+    MOZ_ASSERT(mContentParent);
+  }
+
+  NS_IMETHOD Run() override {
+    AssertIsOnMainThread();
+    RefPtr<ContentParent> contentParent = mContentParent->GetContentParent();
+    if (!contentParent) {
+      return NS_OK;
+    }
+
+    auto principalOrErr = PrincipalInfoToPrincipal(mPrincipalInfo);
+    if (NS_WARN_IF(principalOrErr.isErr())) {
+      contentParent->KillHard(
+          "BroadcastChannel killed: PrincipalInfoToPrincipal failed.");
+      return NS_OK;
+    }
+
+    nsAutoCString origin;
+    nsresult rv = principalOrErr.unwrap()->GetOrigin(origin);
+    if (NS_FAILED(rv)) {
+      contentParent->KillHard(
+          "BroadcastChannel killed: principal::GetOrigin failed.");
+      return NS_OK;
+    }
+
+    if (NS_WARN_IF(!mOrigin.Equals(origin))) {
+      contentParent->KillHard("BroadcastChannel killed: origins do not match.");
+      return NS_OK;
+    }
+
+    return NS_OK;
+  }
+
+ private:
+  RefPtr<ThreadsafeContentParentHandle> mContentParent;
+  PrincipalInfo mPrincipalInfo;
+  nsCString mOrigin;
+};
+
+}  // namespace
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPBroadcastChannelConstructor(
+    PBroadcastChannelParent* actor, const PrincipalInfo& aPrincipalInfo,
+    const nsACString& aOrigin, const nsAString& aChannel) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(this);
+
+  // If the ContentParent is null we are dealing with a same-process actor.
+  if (!parent) {
+    return IPC_OK();
+  }
+
+  RefPtr<CheckPrincipalRunnable> runnable =
+      new CheckPrincipalRunnable(parent.forget(), aPrincipalInfo, aOrigin);
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(runnable));
+
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPBroadcastChannelParent(
+    PBroadcastChannelParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  delete static_cast<BroadcastChannelParent*>(aActor);
+  return true;
+}
+
+mozilla::dom::PServiceWorkerManagerParent*
+BackgroundParentImpl::AllocPServiceWorkerManagerParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  RefPtr<dom::ServiceWorkerManagerParent> agent =
+      new dom::ServiceWorkerManagerParent();
+  return agent.forget().take();
+}
+
+bool BackgroundParentImpl::DeallocPServiceWorkerManagerParent(
+    PServiceWorkerManagerParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  RefPtr<dom::ServiceWorkerManagerParent> parent =
+      dont_AddRef(static_cast<dom::ServiceWorkerManagerParent*>(aActor));
+  MOZ_ASSERT(parent);
+  return true;
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvShutdownServiceWorkerRegistrar() {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  RefPtr<dom::ServiceWorkerRegistrar> service =
+      dom::ServiceWorkerRegistrar::Get();
+  MOZ_ASSERT(service);
+
+  service->Shutdown();
+  return IPC_OK();
+}
+
+already_AddRefed<PCacheStorageParent>
+BackgroundParentImpl::AllocPCacheStorageParent(
+    const Namespace& aNamespace, const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return dom::cache::AllocPCacheStorageParent(this, aNamespace, aPrincipalInfo);
+}
+
+PMessagePortParent* BackgroundParentImpl::AllocPMessagePortParent(
+    const nsID& aUUID, const nsID& aDestinationUUID,
+    const uint32_t& aSequenceID) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return new MessagePortParent(aUUID);
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPMessagePortConstructor(
+    PMessagePortParent* aActor, const nsID& aUUID, const nsID& aDestinationUUID,
+    const uint32_t& aSequenceID) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  MessagePortParent* mp = static_cast<MessagePortParent*>(aActor);
+  if (!mp->Entangle(aDestinationUUID, aSequenceID)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+already_AddRefed<psm::PIPCClientCertsParent>
+BackgroundParentImpl::AllocPIPCClientCertsParent() {
+  if (!IsSocketActor(this)) {
+    return nullptr;
+  }
+
+  // This should only be called in the parent process with the socket process
+  // as the child process, not any content processes, hence the check that the
+  // child ID be 0.
+  MOZ_ASSERT(XRE_IsParentProcess());
+  MOZ_ASSERT(mozilla::ipc::BackgroundParent::GetChildID(this) == 0);
+  if (!XRE_IsParentProcess() ||
+      mozilla::ipc::BackgroundParent::GetChildID(this) != 0) {
+    return nullptr;
+  }
+  RefPtr<psm::IPCClientCertsParent> result = new psm::IPCClientCertsParent();
+  return result.forget();
+}
+
+bool BackgroundParentImpl::DeallocPMessagePortParent(
+    PMessagePortParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  delete static_cast<MessagePortParent*>(aActor);
+  return true;
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvMessagePortForceClose(
+    const nsID& aUUID, const nsID& aDestinationUUID,
+    const uint32_t& aSequenceID) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (!MessagePortParent::ForceClose(aUUID, aDestinationUUID, aSequenceID)) {
+    return IPC_FAIL(this, "MessagePortParent::ForceClose failed.");
+  }
+
+  return IPC_OK();
+}
+
+BackgroundParentImpl::PQuotaParent* BackgroundParentImpl::AllocPQuotaParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  return mozilla::dom::quota::AllocPQuotaParent();
+}
+
+bool BackgroundParentImpl::DeallocPQuotaParent(PQuotaParent* aActor) {
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  return mozilla::dom::quota::DeallocPQuotaParent(aActor);
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvShutdownQuotaManager() {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  if (!mozilla::dom::quota::RecvShutdownQuotaManager()) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvShutdownBackgroundSessionStorageManagers() {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  if (!mozilla::dom::RecvShutdownBackgroundSessionStorageManagers()) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPropagateBackgroundSessionStorageManager(
+    const uint64_t& aCurrentTopContextId, const uint64_t& aTargetTopContextId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL(this, "Wrong actor");
+  }
+
+  mozilla::dom::RecvPropagateBackgroundSessionStorageManager(
+      aCurrentTopContextId, aTargetTopContextId);
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvRemoveBackgroundSessionStorageManager(
+    const uint64_t& aTopContextId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  if (!mozilla::dom::RecvRemoveBackgroundSessionStorageManager(aTopContextId)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvGetSessionStorageManagerData(
+    const uint64_t& aTopContextId, const uint32_t& aSizeLimit,
+    const bool& aCancelSessionStoreTimer,
+    GetSessionStorageManagerDataResolver&& aResolver) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL(this, "Wrong actor");
+  }
+
+  if (!mozilla::dom::RecvGetSessionStorageData(aTopContextId, aSizeLimit,
+                                               aCancelSessionStoreTimer,
+                                               std::move(aResolver))) {
+    return IPC_FAIL(this, "Couldn't get session storage data");
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvLoadSessionStorageManagerData(
+    const uint64_t& aTopContextId,
+    nsTArray<mozilla::dom::SSCacheCopy>&& aOriginCacheCopy) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL(this, "Wrong actor");
+  }
+
+  if (!mozilla::dom::RecvLoadSessionStorageData(aTopContextId,
+                                                std::move(aOriginCacheCopy))) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  return IPC_OK();
+}
+
+already_AddRefed<dom::PFileSystemRequestParent>
+BackgroundParentImpl::AllocPFileSystemRequestParent(
+    const FileSystemParams& aParams) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  RefPtr<FileSystemRequestParent> result = new FileSystemRequestParent();
+
+  if (NS_WARN_IF(!result->Initialize(aParams))) {
+    return nullptr;
+  }
+
+  return result.forget();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPFileSystemRequestConstructor(
+    PFileSystemRequestParent* aActor, const FileSystemParams& params) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  static_cast<FileSystemRequestParent*>(aActor)->Start();
+  return IPC_OK();
+}
+
+// Gamepad API Background IPC
+already_AddRefed<dom::PGamepadEventChannelParent>
+BackgroundParentImpl::AllocPGamepadEventChannelParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return dom::GamepadEventChannelParent::Create();
+}
+
+already_AddRefed<dom::PGamepadTestChannelParent>
+BackgroundParentImpl::AllocPGamepadTestChannelParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return dom::GamepadTestChannelParent::Create();
+}
+
+dom::PWebAuthnTransactionParent*
+BackgroundParentImpl::AllocPWebAuthnTransactionParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return new dom::WebAuthnTransactionParent();
+}
+
+bool BackgroundParentImpl::DeallocPWebAuthnTransactionParent(
+    dom::PWebAuthnTransactionParent* aActor) {
+  MOZ_ASSERT(aActor);
+  delete aActor;
+  return true;
+}
+
+already_AddRefed<net::PHttpBackgroundChannelParent>
+BackgroundParentImpl::AllocPHttpBackgroundChannelParent(
+    const uint64_t& aChannelId) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  RefPtr<net::HttpBackgroundChannelParent> actor =
+      new net::HttpBackgroundChannelParent();
+  return actor.forget();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPHttpBackgroundChannelConstructor(
+    net::PHttpBackgroundChannelParent* aActor, const uint64_t& aChannelId) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  MOZ_ASSERT(aActor);
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  net::HttpBackgroundChannelParent* aParent =
+      static_cast<net::HttpBackgroundChannelParent*>(aActor);
+
+  if (NS_WARN_IF(NS_FAILED(aParent->Init(aChannelId)))) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvCreateMIDIPort(
+    Endpoint<PMIDIPortParent>&& aEndpoint, const MIDIPortInfo& aPortInfo,
+    const bool& aSysexEnabled) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (!aEndpoint.IsValid()) {
+    return IPC_FAIL(this, "invalid endpoint for MIDIPort");
+  }
+
+  MIDIPlatformService::OwnerThread()->Dispatch(NS_NewRunnableFunction(
+      "CreateMIDIPortRunnable", [=, endpoint = std::move(aEndpoint)]() mutable {
+        RefPtr<MIDIPortParent> result =
+            new MIDIPortParent(aPortInfo, aSysexEnabled);
+        endpoint.Bind(result);
+      }));
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvCreateMIDIManager(
+    Endpoint<PMIDIManagerParent>&& aEndpoint) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  if (!aEndpoint.IsValid()) {
+    return IPC_FAIL(this, "invalid endpoint for MIDIManager");
+  }
+
+  MIDIPlatformService::OwnerThread()->Dispatch(NS_NewRunnableFunction(
+      "CreateMIDIManagerRunnable",
+      [=, endpoint = std::move(aEndpoint)]() mutable {
+        RefPtr<MIDIManagerParent> result = new MIDIManagerParent();
+        endpoint.Bind(result);
+        MIDIPlatformService::Get()->AddManager(result);
+      }));
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvHasMIDIDevice(
+    HasMIDIDeviceResolver&& aResolver) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+
+  InvokeAsync(MIDIPlatformService::OwnerThread(), __func__,
+              []() {
+                bool hasDevice = MIDIPlatformService::Get()->HasDevice();
+                return BoolPromise::CreateAndResolve(hasDevice, __func__);
+              })
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [resolver = std::move(aResolver)](
+                 const BoolPromise::ResolveOrRejectValue& r) {
+               resolver(r.IsResolve() && r.ResolveValue());
+             });
+
+  return IPC_OK();
+}
+
+mozilla::dom::PClientManagerParent*
+BackgroundParentImpl::AllocPClientManagerParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return mozilla::dom::AllocClientManagerParent();
+}
+
+bool BackgroundParentImpl::DeallocPClientManagerParent(
+    mozilla::dom::PClientManagerParent* aActor) {
+  return mozilla::dom::DeallocClientManagerParent(aActor);
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPClientManagerConstructor(
+    mozilla::dom::PClientManagerParent* aActor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  mozilla::dom::InitClientManagerParent(aActor);
+  return IPC_OK();
+}
+
+IPCResult BackgroundParentImpl::RecvStorageActivity(
+    const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  dom::StorageActivityService::SendActivity(aPrincipalInfo);
+  return IPC_OK();
+}
+
+IPCResult BackgroundParentImpl::RecvPServiceWorkerManagerConstructor(
+    PServiceWorkerManagerParent* const aActor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  // Only the parent process is allowed to construct this actor.
+  if (BackgroundParent::IsOtherProcessActor(this)) {
+    return IPC_FAIL_NO_REASON(aActor);
+  }
+  return IPC_OK();
+}
+
+already_AddRefed<PServiceWorkerParent>
+BackgroundParentImpl::AllocPServiceWorkerParent(
+    const IPCServiceWorkerDescriptor&) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<ServiceWorkerParent>();
+}
+
+IPCResult BackgroundParentImpl::RecvPServiceWorkerConstructor(
+    PServiceWorkerParent* aActor,
+    const IPCServiceWorkerDescriptor& aDescriptor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  dom::InitServiceWorkerParent(aActor, aDescriptor);
+  return IPC_OK();
+}
+
+already_AddRefed<PServiceWorkerContainerParent>
+BackgroundParentImpl::AllocPServiceWorkerContainerParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<mozilla::dom::ServiceWorkerContainerParent>();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPServiceWorkerContainerConstructor(
+    PServiceWorkerContainerParent* aActor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  dom::InitServiceWorkerContainerParent(aActor);
+  return IPC_OK();
+}
+
+already_AddRefed<PServiceWorkerRegistrationParent>
+BackgroundParentImpl::AllocPServiceWorkerRegistrationParent(
+    const IPCServiceWorkerRegistrationDescriptor&) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<mozilla::dom::ServiceWorkerRegistrationParent>();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPServiceWorkerRegistrationConstructor(
+    PServiceWorkerRegistrationParent* aActor,
+    const IPCServiceWorkerRegistrationDescriptor& aDescriptor) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  dom::InitServiceWorkerRegistrationParent(aActor, aDescriptor);
+  return IPC_OK();
+}
+
+dom::PEndpointForReportParent*
+BackgroundParentImpl::AllocPEndpointForReportParent(
+    const nsAString& aGroupName, const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  RefPtr<dom::EndpointForReportParent> actor =
+      new dom::EndpointForReportParent();
+  return actor.forget().take();
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvPEndpointForReportConstructor(
+    PEndpointForReportParent* aActor, const nsAString& aGroupName,
+    const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  static_cast<dom::EndpointForReportParent*>(aActor)->Run(aGroupName,
+                                                          aPrincipalInfo);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvEnsureRDDProcessAndCreateBridge(
+    EnsureRDDProcessAndCreateBridgeResolver&& aResolver) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  using Type = std::tuple<const nsresult&,
+                          Endpoint<mozilla::PRemoteDecoderManagerChild>&&>;
+
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(this);
+  if (NS_WARN_IF(!parent)) {
+    aResolver(
+        Type(NS_ERROR_NOT_AVAILABLE, Endpoint<PRemoteDecoderManagerChild>()));
+    return IPC_OK();
+  }
+
+  RDDProcessManager* rdd = RDDProcessManager::Get();
+  if (!rdd) {
+    aResolver(
+        Type(NS_ERROR_NOT_AVAILABLE, Endpoint<PRemoteDecoderManagerChild>()));
+    return IPC_OK();
+  }
+
+  rdd->EnsureRDDProcessAndCreateBridge(OtherPid(), parent->ChildID())
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [resolver = std::move(aResolver)](
+                 mozilla::RDDProcessManager::EnsureRDDPromise::
+                     ResolveOrRejectValue&& aValue) mutable {
+               if (aValue.IsReject()) {
+                 resolver(Type(aValue.RejectValue(),
+                               Endpoint<PRemoteDecoderManagerChild>()));
+                 return;
+               }
+               resolver(Type(NS_OK, std::move(aValue.ResolveValue())));
+             });
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvEnsureUtilityProcessAndCreateBridge(
+    const RemoteDecodeIn& aLocation,
+    EnsureUtilityProcessAndCreateBridgeResolver&& aResolver) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  base::ProcessId otherPid = OtherPid();
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(this);
+  if (NS_WARN_IF(!parent)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  dom::ContentParentId childId = parent->ChildID();
+  nsCOMPtr<nsISerialEventTarget> managerThread = GetCurrentSerialEventTarget();
+  if (!managerThread) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "BackgroundParentImpl::RecvEnsureUtilityProcessAndCreateBridge()",
+      [aResolver, managerThread, otherPid, childId, aLocation]() {
+        RefPtr<UtilityProcessManager> upm =
+            UtilityProcessManager::GetSingleton();
+        using Type =
+            std::tuple<const nsresult&,
+                       Endpoint<mozilla::PRemoteDecoderManagerChild>&&>;
+        if (!upm) {
+          managerThread->Dispatch(NS_NewRunnableFunction(
+              "BackgroundParentImpl::RecvEnsureUtilityProcessAndCreateBridge::"
+              "Failure",
+              [aResolver]() {
+                aResolver(Type(NS_ERROR_NOT_AVAILABLE,
+                               Endpoint<PRemoteDecoderManagerChild>()));
+              }));
+        } else {
+          SandboxingKind sbKind = GetSandboxingKindFromLocation(aLocation);
+          upm->StartProcessForRemoteMediaDecoding(otherPid, childId, sbKind)
+              ->Then(managerThread, __func__,
+                     [resolver = aResolver](
+                         mozilla::ipc::UtilityProcessManager::
+                             StartRemoteDecodingUtilityPromise::
+                                 ResolveOrRejectValue&& aValue) mutable {
+                       if (aValue.IsReject()) {
+                         resolver(Type(aValue.RejectValue(),
+                                       Endpoint<PRemoteDecoderManagerChild>()));
+                         return;
+                       }
+                       resolver(Type(NS_OK, std::move(aValue.ResolveValue())));
+                     });
+        }
+      }));
+  return IPC_OK();
+}
+
+bool BackgroundParentImpl::DeallocPEndpointForReportParent(
+    PEndpointForReportParent* aActor) {
+  RefPtr<dom::EndpointForReportParent> actor =
+      dont_AddRef(static_cast<dom::EndpointForReportParent*>(aActor));
+  return true;
+}
+
+mozilla::ipc::IPCResult BackgroundParentImpl::RecvRemoveEndpoint(
+    const nsAString& aGroupName, const nsACString& aEndpointURL,
+    const PrincipalInfo& aPrincipalInfo) {
+  if (!IsContentActor(this)) {
+    return IPC_FAIL(this, "must be a content actor");
+  }
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "BackgroundParentImpl::RecvRemoveEndpoint(",
+      [aGroupName = nsString(aGroupName),
+       aEndpointURL = nsCString(aEndpointURL), aPrincipalInfo]() {
+        dom::ReportingHeader::RemoveEndpoint(aGroupName, aEndpointURL,
+                                             aPrincipalInfo);
+      }));
+
+  return IPC_OK();
+}
+
+dom::PMediaTransportParent* BackgroundParentImpl::AllocPMediaTransportParent() {
+#ifdef MOZ_WEBRTC
+  if (!IsSocketBridgeActor(this)) {
+    return nullptr;
+  }
+
+  return new MediaTransportParent;
+#else
+  return nullptr;
+#endif
+}
+
+bool BackgroundParentImpl::DeallocPMediaTransportParent(
+    dom::PMediaTransportParent* aActor) {
+#ifdef MOZ_WEBRTC
+  delete aActor;
+#endif
+  return true;
+}
+
+already_AddRefed<dom::locks::PLockManagerParent>
+BackgroundParentImpl::AllocPLockManagerParent(
+    const ContentPrincipalInfo& aPrincipalInfo, const nsID& aClientId) {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<mozilla::dom::locks::LockManagerParent>(aPrincipalInfo,
+                                                               aClientId);
+}
+
+already_AddRefed<dom::PFetchParent> BackgroundParentImpl::AllocPFetchParent() {
+  if (!IsContentActor(this)) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<dom::FetchParent>();
+}
+
+already_AddRefed<mozilla::net::PWebSocketConnectionParent>
+BackgroundParentImpl::AllocPWebSocketConnectionParent(
+    const uint32_t& aListenerId) {
+  if (!IsSocketActor(this)) {
+    return nullptr;
+  }
+
+  Maybe<nsCOMPtr<nsIHttpUpgradeListener>> listener =
+      net::HttpConnectionMgrParent::GetAndRemoveHttpUpgradeListener(
+          aListenerId);
+  if (!listener) {
+    return nullptr;
+  }
+
+  RefPtr<mozilla::net::WebSocketConnectionParent> actor =
+      new mozilla::net::WebSocketConnectionParent(*listener);
+  return actor.forget();
+}
+
+mozilla::ipc::IPCResult
+BackgroundParentImpl::RecvPWebSocketConnectionConstructor(
+    PWebSocketConnectionParent* actor, const uint32_t& aListenerId) {
+  if (!IsSocketActor(this)) {
+    return IPC_FAIL(this, "must be a socket actor");
+  }
+
+  return IPC_OK();
+}
+
+}  // namespace mozilla::ipc
+
+void TestParent::ActorDestroy(ActorDestroyReason aWhy) {
+  mozilla::ipc::AssertIsInMainOrSocketProcess();
+  AssertIsOnBackgroundThread();
+}
diff --git a/ipc/glue/BackgroundParentImpl.h b/ipc/glue/BackgroundParentImpl.h
new file mode 100644
index 0000000000..50c1607e86
--- /dev/null
+++ b/ipc/glue/BackgroundParentImpl.h
@@ -0,0 +1,415 @@
+/* -*- 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_ipc_backgroundparentimpl_h__
+#define mozilla_ipc_backgroundparentimpl_h__
+
+#include "mozilla/ipc/PBackgroundParent.h"
+
+namespace mozilla::ipc {
+
+// Instances of this class should never be created directly. This class is meant
+// to be inherited in BackgroundImpl.
+class BackgroundParentImpl : public PBackgroundParent {
+ protected:
+  BackgroundParentImpl();
+  virtual ~BackgroundParentImpl();
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  PBackgroundTestParent* AllocPBackgroundTestParent(
+      const nsACString& aTestArg) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundTestConstructor(
+      PBackgroundTestParent* aActor, const nsACString& aTestArg) override;
+
+  bool DeallocPBackgroundTestParent(PBackgroundTestParent* aActor) override;
+
+  already_AddRefed<PBackgroundIDBFactoryParent>
+  AllocPBackgroundIDBFactoryParent(const LoggingInfo& aLoggingInfo) override;
+
+  already_AddRefed<net::PBackgroundDataBridgeParent>
+  AllocPBackgroundDataBridgeParent(const uint64_t& aChannelID) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundIDBFactoryConstructor(
+      PBackgroundIDBFactoryParent* aActor,
+      const LoggingInfo& aLoggingInfo) override;
+
+  PBackgroundIndexedDBUtilsParent* AllocPBackgroundIndexedDBUtilsParent()
+      override;
+
+  bool DeallocPBackgroundIndexedDBUtilsParent(
+      PBackgroundIndexedDBUtilsParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvFlushPendingFileDeletions() override;
+
+  PBackgroundSDBConnectionParent* AllocPBackgroundSDBConnectionParent(
+      const PersistenceType& aPersistenceType,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundSDBConnectionConstructor(
+      PBackgroundSDBConnectionParent* aActor,
+      const PersistenceType& aPersistenceType,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  bool DeallocPBackgroundSDBConnectionParent(
+      PBackgroundSDBConnectionParent* aActor) override;
+
+  PBackgroundLSDatabaseParent* AllocPBackgroundLSDatabaseParent(
+      const PrincipalInfo& aPrincipalInfo, const uint32_t& aPrivateBrowsingId,
+      const uint64_t& aDatastoreId) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundLSDatabaseConstructor(
+      PBackgroundLSDatabaseParent* aActor, const PrincipalInfo& aPrincipalInfo,
+      const uint32_t& aPrivateBrowsingId,
+      const uint64_t& aDatastoreId) override;
+
+  bool DeallocPBackgroundLSDatabaseParent(
+      PBackgroundLSDatabaseParent* aActor) override;
+
+  PBackgroundLSObserverParent* AllocPBackgroundLSObserverParent(
+      const uint64_t& aObserverId) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundLSObserverConstructor(
+      PBackgroundLSObserverParent* aActor,
+      const uint64_t& aObserverId) override;
+
+  bool DeallocPBackgroundLSObserverParent(
+      PBackgroundLSObserverParent* aActor) override;
+
+  PBackgroundLSRequestParent* AllocPBackgroundLSRequestParent(
+      const LSRequestParams& aParams) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundLSRequestConstructor(
+      PBackgroundLSRequestParent* aActor,
+      const LSRequestParams& aParams) override;
+
+  bool DeallocPBackgroundLSRequestParent(
+      PBackgroundLSRequestParent* aActor) override;
+
+  PBackgroundLSSimpleRequestParent* AllocPBackgroundLSSimpleRequestParent(
+      const LSSimpleRequestParams& aParams) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundLSSimpleRequestConstructor(
+      PBackgroundLSSimpleRequestParent* aActor,
+      const LSSimpleRequestParams& aParams) override;
+
+  bool DeallocPBackgroundLSSimpleRequestParent(
+      PBackgroundLSSimpleRequestParent* aActor) override;
+
+  PBackgroundLocalStorageCacheParent* AllocPBackgroundLocalStorageCacheParent(
+      const PrincipalInfo& aPrincipalInfo, const nsACString& aOriginKey,
+      const uint32_t& aPrivateBrowsingId) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundLocalStorageCacheConstructor(
+      PBackgroundLocalStorageCacheParent* aActor,
+      const PrincipalInfo& aPrincipalInfo, const nsACString& aOriginKey,
+      const uint32_t& aPrivateBrowsingId) override;
+
+  bool DeallocPBackgroundLocalStorageCacheParent(
+      PBackgroundLocalStorageCacheParent* aActor) override;
+
+  PBackgroundStorageParent* AllocPBackgroundStorageParent(
+      const nsAString& aProfilePath,
+      const uint32_t& aPrivateBrowsingId) override;
+
+  mozilla::ipc::IPCResult RecvPBackgroundStorageConstructor(
+      PBackgroundStorageParent* aActor, const nsAString& aProfilePath,
+      const uint32_t& aPrivateBrowsingId) override;
+
+  bool DeallocPBackgroundStorageParent(
+      PBackgroundStorageParent* aActor) override;
+
+  already_AddRefed<PBackgroundSessionStorageManagerParent>
+  AllocPBackgroundSessionStorageManagerParent(
+      const uint64_t& aTopContextId) override;
+
+  already_AddRefed<PBackgroundSessionStorageServiceParent>
+  AllocPBackgroundSessionStorageServiceParent() override;
+
+  mozilla::ipc::IPCResult RecvCreateFileSystemManagerParent(
+      const PrincipalInfo& aPrincipalInfo,
+      Endpoint<mozilla::dom::PFileSystemManagerParent>&& aParentEndpoint,
+      CreateFileSystemManagerParentResolver&& aResolver) override;
+
+  mozilla::ipc::IPCResult RecvCreateWebTransportParent(
+      const nsAString& aURL, nsIPrincipal* aPrincipal,
+      const mozilla::Maybe<IPCClientInfo>& aClientInfo, const bool& aDedicated,
+      const bool& aRequireUnreliable, const uint32_t& aCongestionControl,
+      // Sequence<WebTransportHash>* aServerCertHashes,
+      Endpoint<PWebTransportParent>&& aParentEndpoint,
+      CreateWebTransportParentResolver&& aResolver) override;
+
+  already_AddRefed<PIdleSchedulerParent> AllocPIdleSchedulerParent() override;
+
+  PTemporaryIPCBlobParent* AllocPTemporaryIPCBlobParent() override;
+
+  mozilla::ipc::IPCResult RecvPTemporaryIPCBlobConstructor(
+      PTemporaryIPCBlobParent* actor) override;
+
+  bool DeallocPTemporaryIPCBlobParent(PTemporaryIPCBlobParent* aActor) override;
+
+  PFileCreatorParent* AllocPFileCreatorParent(
+      const nsAString& aFullPath, const nsAString& aType,
+      const nsAString& aName, const Maybe<int64_t>& aLastModified,
+      const bool& aExistenceCheck, const bool& aIsFromNsIFile) override;
+
+  mozilla::ipc::IPCResult RecvPFileCreatorConstructor(
+      PFileCreatorParent* actor, const nsAString& aFullPath,
+      const nsAString& aType, const nsAString& aName,
+      const Maybe<int64_t>& aLastModified, const bool& aExistenceCheck,
+      const bool& aIsFromNsIFile) override;
+
+  bool DeallocPFileCreatorParent(PFileCreatorParent* aActor) override;
+
+  mozilla::dom::PRemoteWorkerControllerParent*
+  AllocPRemoteWorkerControllerParent(
+      const mozilla::dom::RemoteWorkerData& aRemoteWorkerData) override;
+
+  mozilla::ipc::IPCResult RecvPRemoteWorkerControllerConstructor(
+      mozilla::dom::PRemoteWorkerControllerParent* aActor,
+      const mozilla::dom::RemoteWorkerData& aRemoteWorkerData) override;
+
+  bool DeallocPRemoteWorkerControllerParent(
+      mozilla::dom::PRemoteWorkerControllerParent* aActor) override;
+
+  already_AddRefed<PRemoteWorkerServiceParent> AllocPRemoteWorkerServiceParent()
+      override;
+
+  mozilla::ipc::IPCResult RecvPRemoteWorkerServiceConstructor(
+      PRemoteWorkerServiceParent* aActor) override;
+
+  mozilla::dom::PSharedWorkerParent* AllocPSharedWorkerParent(
+      const mozilla::dom::RemoteWorkerData& aData, const uint64_t& aWindowID,
+      const mozilla::dom::MessagePortIdentifier& aPortIdentifier) override;
+
+  mozilla::ipc::IPCResult RecvPSharedWorkerConstructor(
+      PSharedWorkerParent* aActor, const mozilla::dom::RemoteWorkerData& aData,
+      const uint64_t& aWindowID,
+      const mozilla::dom::MessagePortIdentifier& aPortIdentifier) override;
+
+  bool DeallocPSharedWorkerParent(PSharedWorkerParent* aActor) override;
+
+  already_AddRefed<PVsyncParent> AllocPVsyncParent() override;
+
+  already_AddRefed<mozilla::psm::PVerifySSLServerCertParent>
+  AllocPVerifySSLServerCertParent(
+      const nsTArray<ByteArray>& aPeerCertChain, const nsACString& aHostName,
+      const int32_t& aPort, const OriginAttributes& aOriginAttributes,
+      const Maybe<ByteArray>& aStapledOCSPResponse,
+      const Maybe<ByteArray>& aSctsFromTLSExtension,
+      const Maybe<DelegatedCredentialInfoArg>& aDcInfo,
+      const uint32_t& aProviderFlags,
+      const uint32_t& aCertVerifierFlags) override;
+
+  mozilla::ipc::IPCResult RecvPVerifySSLServerCertConstructor(
+      PVerifySSLServerCertParent* aActor, nsTArray<ByteArray>&& aPeerCertChain,
+      const nsACString& aHostName, const int32_t& aPort,
+      const OriginAttributes& aOriginAttributes,
+      const Maybe<ByteArray>& aStapledOCSPResponse,
+      const Maybe<ByteArray>& aSctsFromTLSExtension,
+      const Maybe<DelegatedCredentialInfoArg>& aDcInfo,
+      const uint32_t& aProviderFlags,
+      const uint32_t& aCertVerifierFlags) override;
+
+  virtual already_AddRefed<mozilla::psm::PSelectTLSClientAuthCertParent>
+  AllocPSelectTLSClientAuthCertParent(
+      const nsACString& aHostName, const OriginAttributes& aOriginAttributes,
+      const int32_t& aPort, const uint32_t& aProviderFlags,
+      const uint32_t& aProviderTlsFlags, const ByteArray& aServerCertBytes,
+      const nsTArray<ByteArray>& aCANames) override;
+  virtual mozilla::ipc::IPCResult RecvPSelectTLSClientAuthCertConstructor(
+      PSelectTLSClientAuthCertParent* actor, const nsACString& aHostName,
+      const OriginAttributes& aOriginAttributes, const int32_t& aPort,
+      const uint32_t& aProviderFlags, const uint32_t& aProviderTlsFlags,
+      const ByteArray& aServerCertBytes,
+      nsTArray<ByteArray>&& aCANames) override;
+
+  PBroadcastChannelParent* AllocPBroadcastChannelParent(
+      const PrincipalInfo& aPrincipalInfo, const nsACString& aOrigin,
+      const nsAString& aChannel) override;
+
+  mozilla::ipc::IPCResult RecvPBroadcastChannelConstructor(
+      PBroadcastChannelParent* actor, const PrincipalInfo& aPrincipalInfo,
+      const nsACString& origin, const nsAString& channel) override;
+
+  bool DeallocPBroadcastChannelParent(PBroadcastChannelParent* aActor) override;
+
+  PServiceWorkerManagerParent* AllocPServiceWorkerManagerParent() override;
+
+  bool DeallocPServiceWorkerManagerParent(
+      PServiceWorkerManagerParent* aActor) override;
+
+  PCamerasParent* AllocPCamerasParent() override;
+#ifdef MOZ_WEBRTC
+  mozilla::ipc::IPCResult RecvPCamerasConstructor(
+      PCamerasParent* aActor) override;
+#endif
+  bool DeallocPCamerasParent(PCamerasParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvShutdownServiceWorkerRegistrar() override;
+
+  already_AddRefed<dom::cache::PCacheStorageParent> AllocPCacheStorageParent(
+      const dom::cache::Namespace& aNamespace,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  PUDPSocketParent* AllocPUDPSocketParent(const Maybe<PrincipalInfo>& pInfo,
+                                          const nsACString& aFilter) override;
+  mozilla::ipc::IPCResult RecvPUDPSocketConstructor(
+      PUDPSocketParent*, const Maybe<PrincipalInfo>& aPrincipalInfo,
+      const nsACString& aFilter) override;
+  bool DeallocPUDPSocketParent(PUDPSocketParent*) override;
+
+  PMessagePortParent* AllocPMessagePortParent(
+      const nsID& aUUID, const nsID& aDestinationUUID,
+      const uint32_t& aSequenceID) override;
+
+  mozilla::ipc::IPCResult RecvPMessagePortConstructor(
+      PMessagePortParent* aActor, const nsID& aUUID,
+      const nsID& aDestinationUUID, const uint32_t& aSequenceID) override;
+
+  already_AddRefed<PIPCClientCertsParent> AllocPIPCClientCertsParent() override;
+
+  bool DeallocPMessagePortParent(PMessagePortParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvMessagePortForceClose(
+      const nsID& aUUID, const nsID& aDestinationUUID,
+      const uint32_t& aSequenceID) override;
+
+  PQuotaParent* AllocPQuotaParent() override;
+
+  bool DeallocPQuotaParent(PQuotaParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvShutdownQuotaManager() override;
+
+  mozilla::ipc::IPCResult RecvShutdownBackgroundSessionStorageManagers()
+      override;
+
+  mozilla::ipc::IPCResult RecvPropagateBackgroundSessionStorageManager(
+      const uint64_t& aCurrentTopContextId,
+      const uint64_t& aTargetTopContextId) override;
+
+  mozilla::ipc::IPCResult RecvRemoveBackgroundSessionStorageManager(
+      const uint64_t& aTopContextId) override;
+
+  mozilla::ipc::IPCResult RecvLoadSessionStorageManagerData(
+      const uint64_t& aTopContextId,
+      nsTArray<mozilla::dom::SSCacheCopy>&& aOriginCacheCopy) override;
+
+  mozilla::ipc::IPCResult RecvGetSessionStorageManagerData(
+      const uint64_t& aTopContextId, const uint32_t& aSizeLimit,
+      const bool& aCancelSessionStoreTimer,
+      GetSessionStorageManagerDataResolver&& aResolver) override;
+
+  already_AddRefed<PFileSystemRequestParent> AllocPFileSystemRequestParent(
+      const FileSystemParams&) override;
+
+  mozilla::ipc::IPCResult RecvPFileSystemRequestConstructor(
+      PFileSystemRequestParent* actor, const FileSystemParams& params) override;
+
+  // Gamepad API Background IPC
+  already_AddRefed<PGamepadEventChannelParent> AllocPGamepadEventChannelParent()
+      override;
+
+  already_AddRefed<PGamepadTestChannelParent> AllocPGamepadTestChannelParent()
+      override;
+
+  PWebAuthnTransactionParent* AllocPWebAuthnTransactionParent() override;
+
+  bool DeallocPWebAuthnTransactionParent(
+      PWebAuthnTransactionParent* aActor) override;
+
+  already_AddRefed<PHttpBackgroundChannelParent>
+  AllocPHttpBackgroundChannelParent(const uint64_t& aChannelId) override;
+
+  mozilla::ipc::IPCResult RecvPHttpBackgroundChannelConstructor(
+      PHttpBackgroundChannelParent* aActor,
+      const uint64_t& aChannelId) override;
+
+  PClientManagerParent* AllocPClientManagerParent() override;
+
+  bool DeallocPClientManagerParent(PClientManagerParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvPClientManagerConstructor(
+      PClientManagerParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvCreateMIDIPort(
+      Endpoint<PMIDIPortParent>&& aEndpoint, const MIDIPortInfo& aPortInfo,
+      const bool& aSysexEnabled) override;
+
+  mozilla::ipc::IPCResult RecvCreateMIDIManager(
+      Endpoint<PMIDIManagerParent>&& aEndpoint) override;
+
+  mozilla::ipc::IPCResult RecvHasMIDIDevice(
+      HasMIDIDeviceResolver&& aResolver) override;
+
+  mozilla::ipc::IPCResult RecvStorageActivity(
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  already_AddRefed<PServiceWorkerParent> AllocPServiceWorkerParent(
+      const IPCServiceWorkerDescriptor&) final;
+
+  mozilla::ipc::IPCResult RecvPServiceWorkerManagerConstructor(
+      PServiceWorkerManagerParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvPServiceWorkerConstructor(
+      PServiceWorkerParent* aActor,
+      const IPCServiceWorkerDescriptor& aDescriptor) override;
+
+  already_AddRefed<PServiceWorkerContainerParent>
+  AllocPServiceWorkerContainerParent() final;
+
+  mozilla::ipc::IPCResult RecvPServiceWorkerContainerConstructor(
+      PServiceWorkerContainerParent* aActor) override;
+
+  already_AddRefed<PServiceWorkerRegistrationParent>
+  AllocPServiceWorkerRegistrationParent(
+      const IPCServiceWorkerRegistrationDescriptor&) final;
+
+  mozilla::ipc::IPCResult RecvPServiceWorkerRegistrationConstructor(
+      PServiceWorkerRegistrationParent* aActor,
+      const IPCServiceWorkerRegistrationDescriptor& aDescriptor) override;
+
+  PEndpointForReportParent* AllocPEndpointForReportParent(
+      const nsAString& aGroupName,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  mozilla::ipc::IPCResult RecvPEndpointForReportConstructor(
+      PEndpointForReportParent* actor, const nsAString& aGroupName,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  mozilla::ipc::IPCResult RecvEnsureRDDProcessAndCreateBridge(
+      EnsureRDDProcessAndCreateBridgeResolver&& aResolver) override;
+
+  mozilla::ipc::IPCResult RecvEnsureUtilityProcessAndCreateBridge(
+      const RemoteDecodeIn& aLocation,
+      EnsureUtilityProcessAndCreateBridgeResolver&& aResolver) override;
+
+  bool DeallocPEndpointForReportParent(
+      PEndpointForReportParent* aActor) override;
+
+  mozilla::ipc::IPCResult RecvRemoveEndpoint(
+      const nsAString& aGroupName, const nsACString& aEndpointURL,
+      const PrincipalInfo& aPrincipalInfo) override;
+
+  dom::PMediaTransportParent* AllocPMediaTransportParent() override;
+  bool DeallocPMediaTransportParent(
+      dom::PMediaTransportParent* aActor) override;
+
+  already_AddRefed<mozilla::net::PWebSocketConnectionParent>
+  AllocPWebSocketConnectionParent(const uint32_t& aListenerId) override;
+  mozilla::ipc::IPCResult RecvPWebSocketConnectionConstructor(
+      PWebSocketConnectionParent* actor, const uint32_t& aListenerId) override;
+
+  already_AddRefed<PLockManagerParent> AllocPLockManagerParent(
+      const ContentPrincipalInfo& aPrincipalInfo, const nsID& aClientId) final;
+
+  already_AddRefed<PFetchParent> AllocPFetchParent() override;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // mozilla_ipc_backgroundparentimpl_h__
diff --git a/ipc/glue/BackgroundStarterChild.h b/ipc/glue/BackgroundStarterChild.h
new file mode 100644
index 0000000000..1a0b5386f8
--- /dev/null
+++ b/ipc/glue/BackgroundStarterChild.h
@@ -0,0 +1,35 @@
+/* -*- 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_ipc_BackgroundStarterChild_h
+#define mozilla_ipc_BackgroundStarterChild_h
+
+#include "mozilla/ipc/PBackgroundStarterChild.h"
+#include "mozilla/dom/ContentChild.h"
+
+namespace mozilla::ipc {
+
+class BackgroundStarterChild final : public PBackgroundStarterChild {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(BackgroundStarterChild, override)
+
+  BackgroundStarterChild(base::ProcessId aOtherPid,
+                         nsISerialEventTarget* aTaskQueue)
+      : mOtherPid(aOtherPid), mTaskQueue(aTaskQueue) {}
+
+  // Unlike the methods on `IToplevelProtocol`, may be accessed on any thread
+  // and will not be modified after construction.
+  const base::ProcessId mOtherPid;
+  const nsCOMPtr<nsISerialEventTarget> mTaskQueue;
+
+ private:
+  friend class PBackgroundStarterChild;
+  ~BackgroundStarterChild() = default;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // mozilla_ipc_BackgroundStarterChild_h
diff --git a/ipc/glue/BackgroundStarterParent.h b/ipc/glue/BackgroundStarterParent.h
new file mode 100644
index 0000000000..4312b9ab2a
--- /dev/null
+++ b/ipc/glue/BackgroundStarterParent.h
@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_BackgroundStarterParent_h
+#define mozilla_ipc_BackgroundStarterParent_h
+
+#include "mozilla/ipc/PBackgroundStarterParent.h"
+#include "mozilla/dom/ContentParent.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla::ipc {
+
+class BackgroundStarterParent final : public PBackgroundStarterParent {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING_WITH_DELETE_ON_MAIN_THREAD(
+      BackgroundStarterParent, override)
+
+  // Implemented in BackgroundImpl.cpp
+  BackgroundStarterParent(mozilla::dom::ThreadsafeContentParentHandle* aContent,
+                          bool aCrossProcess);
+
+  void SetLiveActorArray(nsTArray<IToplevelProtocol*>* aLiveActorArray);
+
+ private:
+  friend class PBackgroundStarterParent;
+  ~BackgroundStarterParent() = default;
+
+  // Implemented in BackgroundImpl.cpp
+  void ActorDestroy(ActorDestroyReason aReason) override;
+
+  // Implemented in BackgroundImpl.cpp
+  IPCResult RecvInitBackground(Endpoint<PBackgroundParent>&& aEndpoint);
+
+  const bool mCrossProcess;
+
+  const RefPtr<mozilla::dom::ThreadsafeContentParentHandle> mContent;
+
+  // Set when the actor is opened successfully and used to handle shutdown
+  // hangs. Only touched on the background thread.
+  nsTArray<IToplevelProtocol*>* mLiveActorArray = nullptr;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // mozilla_ipc_BackgroundStarterParent_h
diff --git a/ipc/glue/BackgroundUtils.cpp b/ipc/glue/BackgroundUtils.cpp
new file mode 100644
index 0000000000..f3071bb627
--- /dev/null
+++ b/ipc/glue/BackgroundUtils.cpp
@@ -0,0 +1,1115 @@
+/* -*- 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 "BackgroundUtils.h"
+
+#include "MainThreadUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ContentPrincipal.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/SystemPrincipal.h"
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "mozilla/net/CookieJarSettings.h"
+#include "mozilla/net/InterceptionInfo.h"
+#include "mozilla/net/NeckoChannelParams.h"
+#include "ExpandedPrincipal.h"
+#include "nsIScriptSecurityManager.h"
+#include "nsIURI.h"
+#include "nsNetUtil.h"
+#include "mozilla/LoadInfo.h"
+#include "nsContentUtils.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "mozilla/nsRedirectHistoryEntry.h"
+#include "mozilla/dom/nsCSPUtils.h"
+#include "mozilla/dom/nsCSPContext.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/WindowGlobalParent.h"
+#include "mozilla/LoadInfo.h"
+
+using namespace mozilla::dom;
+using namespace mozilla::net;
+
+namespace mozilla {
+
+namespace ipc {
+
+Result<nsCOMPtr<nsIPrincipal>, nsresult> PrincipalInfoToPrincipal(
+    const PrincipalInfo& aPrincipalInfo) {
+  MOZ_ASSERT(aPrincipalInfo.type() != PrincipalInfo::T__None);
+
+  nsCOMPtr<nsIPrincipal> principal;
+  nsresult rv;
+
+  switch (aPrincipalInfo.type()) {
+    case PrincipalInfo::TSystemPrincipalInfo: {
+      principal = SystemPrincipal::Get();
+      if (NS_WARN_IF(!principal)) {
+        return Err(NS_ERROR_NOT_INITIALIZED);
+      }
+
+      return principal;
+    }
+
+    case PrincipalInfo::TNullPrincipalInfo: {
+      const NullPrincipalInfo& info = aPrincipalInfo.get_NullPrincipalInfo();
+
+      nsCOMPtr<nsIURI> uri;
+      rv = NS_NewURI(getter_AddRefs(uri), info.spec());
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return Err(rv);
+      }
+
+      if (!uri->SchemeIs(NS_NULLPRINCIPAL_SCHEME)) {
+        return Err(NS_ERROR_ILLEGAL_VALUE);
+      }
+
+      principal = NullPrincipal::Create(info.attrs(), uri);
+      return principal;
+    }
+
+    case PrincipalInfo::TContentPrincipalInfo: {
+      const ContentPrincipalInfo& info =
+          aPrincipalInfo.get_ContentPrincipalInfo();
+
+      nsCOMPtr<nsIURI> uri;
+      rv = NS_NewURI(getter_AddRefs(uri), info.spec());
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return Err(rv);
+      }
+
+      nsCOMPtr<nsIURI> domain;
+      if (info.domain()) {
+        rv = NS_NewURI(getter_AddRefs(domain), *info.domain());
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return Err(rv);
+        }
+      }
+
+      principal =
+          BasePrincipal::CreateContentPrincipal(uri, info.attrs(), domain);
+      if (NS_WARN_IF(!principal)) {
+        return Err(NS_ERROR_NULL_POINTER);
+      }
+
+      // Origin must match what the_new_principal.getOrigin returns.
+      nsAutoCString originNoSuffix;
+      rv = principal->GetOriginNoSuffix(originNoSuffix);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return Err(rv);
+      }
+
+      if (NS_WARN_IF(!info.originNoSuffix().Equals(originNoSuffix))) {
+        return Err(NS_ERROR_FAILURE);
+      }
+
+      if (!info.baseDomain().IsVoid()) {
+        nsAutoCString baseDomain;
+        rv = principal->GetBaseDomain(baseDomain);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return Err(rv);
+        }
+
+        if (NS_WARN_IF(!info.baseDomain().Equals(baseDomain))) {
+          return Err(NS_ERROR_FAILURE);
+        }
+      }
+      return principal;
+    }
+
+    case PrincipalInfo::TExpandedPrincipalInfo: {
+      const ExpandedPrincipalInfo& info =
+          aPrincipalInfo.get_ExpandedPrincipalInfo();
+
+      nsTArray<nsCOMPtr<nsIPrincipal>> allowlist;
+      nsCOMPtr<nsIPrincipal> alPrincipal;
+
+      for (uint32_t i = 0; i < info.allowlist().Length(); i++) {
+        auto principalOrErr = PrincipalInfoToPrincipal(info.allowlist()[i]);
+        if (NS_WARN_IF(principalOrErr.isErr())) {
+          nsresult ret = principalOrErr.unwrapErr();
+          return Err(ret);
+        }
+        // append that principal to the allowlist
+        allowlist.AppendElement(principalOrErr.unwrap());
+      }
+
+      RefPtr<ExpandedPrincipal> expandedPrincipal =
+          ExpandedPrincipal::Create(allowlist, info.attrs());
+      if (!expandedPrincipal) {
+        return Err(NS_ERROR_FAILURE);
+      }
+
+      principal = expandedPrincipal;
+      return principal;
+    }
+
+    default:
+      return Err(NS_ERROR_FAILURE);
+  }
+}
+
+bool StorageKeysEqual(const PrincipalInfo& aLeft, const PrincipalInfo& aRight) {
+  MOZ_RELEASE_ASSERT(aLeft.type() == PrincipalInfo::TContentPrincipalInfo ||
+                     aLeft.type() == PrincipalInfo::TSystemPrincipalInfo);
+  MOZ_RELEASE_ASSERT(aRight.type() == PrincipalInfo::TContentPrincipalInfo ||
+                     aRight.type() == PrincipalInfo::TSystemPrincipalInfo);
+
+  if (aLeft.type() != aRight.type()) {
+    return false;
+  }
+
+  if (aLeft.type() == PrincipalInfo::TContentPrincipalInfo) {
+    const ContentPrincipalInfo& leftContent = aLeft.get_ContentPrincipalInfo();
+    const ContentPrincipalInfo& rightContent =
+        aRight.get_ContentPrincipalInfo();
+
+    return leftContent.attrs() == rightContent.attrs() &&
+           leftContent.originNoSuffix() == rightContent.originNoSuffix();
+  }
+
+  // Storage keys for the System principal always equal.
+  return true;
+}
+
+already_AddRefed<nsIContentSecurityPolicy> CSPInfoToCSP(
+    const CSPInfo& aCSPInfo, Document* aRequestingDoc,
+    nsresult* aOptionalResult) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsresult stackResult;
+  nsresult& rv = aOptionalResult ? *aOptionalResult : stackResult;
+
+  RefPtr<nsCSPContext> csp = new nsCSPContext();
+
+  if (aRequestingDoc) {
+    rv = csp->SetRequestContextWithDocument(aRequestingDoc);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return nullptr;
+    }
+  } else {
+    auto principalOrErr =
+        PrincipalInfoToPrincipal(aCSPInfo.requestPrincipalInfo());
+    if (NS_WARN_IF(principalOrErr.isErr())) {
+      return nullptr;
+    }
+
+    nsCOMPtr<nsIURI> selfURI;
+    if (!aCSPInfo.selfURISpec().IsEmpty()) {
+      rv = NS_NewURI(getter_AddRefs(selfURI), aCSPInfo.selfURISpec());
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return nullptr;
+      }
+    }
+
+    nsCOMPtr<nsIPrincipal> principal = principalOrErr.unwrap();
+
+    rv = csp->SetRequestContextWithPrincipal(
+        principal, selfURI, aCSPInfo.referrer(), aCSPInfo.innerWindowID());
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return nullptr;
+    }
+  }
+  csp->SetSkipAllowInlineStyleCheck(aCSPInfo.skipAllowInlineStyleCheck());
+
+  for (uint32_t i = 0; i < aCSPInfo.policyInfos().Length(); i++) {
+    csp->AddIPCPolicy(aCSPInfo.policyInfos()[i]);
+  }
+  return csp.forget();
+}
+
+nsresult CSPToCSPInfo(nsIContentSecurityPolicy* aCSP, CSPInfo* aCSPInfo) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aCSP);
+  MOZ_ASSERT(aCSPInfo);
+
+  if (!aCSP || !aCSPInfo) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIPrincipal> requestPrincipal = aCSP->GetRequestPrincipal();
+
+  PrincipalInfo requestingPrincipalInfo;
+  nsresult rv =
+      PrincipalToPrincipalInfo(requestPrincipal, &requestingPrincipalInfo);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIURI> selfURI = aCSP->GetSelfURI();
+  nsAutoCString selfURISpec;
+  if (selfURI) {
+    selfURI->GetSpec(selfURISpec);
+  }
+
+  nsAutoString referrer;
+  aCSP->GetReferrer(referrer);
+
+  uint64_t windowID = aCSP->GetInnerWindowID();
+  bool skipAllowInlineStyleCheck = aCSP->GetSkipAllowInlineStyleCheck();
+
+  nsTArray<ContentSecurityPolicy> policies;
+  static_cast<nsCSPContext*>(aCSP)->SerializePolicies(policies);
+
+  *aCSPInfo = CSPInfo(std::move(policies), requestingPrincipalInfo, selfURISpec,
+                      referrer, windowID, skipAllowInlineStyleCheck);
+  return NS_OK;
+}
+
+nsresult PrincipalToPrincipalInfo(nsIPrincipal* aPrincipal,
+                                  PrincipalInfo* aPrincipalInfo,
+                                  bool aSkipBaseDomain) {
+  MOZ_ASSERT(aPrincipal);
+  MOZ_ASSERT(aPrincipalInfo);
+
+  nsresult rv;
+  if (aPrincipal->GetIsNullPrincipal()) {
+    nsAutoCString spec;
+    rv = aPrincipal->GetAsciiSpec(spec);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    *aPrincipalInfo =
+        NullPrincipalInfo(aPrincipal->OriginAttributesRef(), spec);
+    return NS_OK;
+  }
+
+  if (aPrincipal->IsSystemPrincipal()) {
+    *aPrincipalInfo = SystemPrincipalInfo();
+    return NS_OK;
+  }
+
+  // might be an expanded principal
+  auto* basePrin = BasePrincipal::Cast(aPrincipal);
+  if (basePrin->Is<ExpandedPrincipal>()) {
+    auto* expanded = basePrin->As<ExpandedPrincipal>();
+
+    nsTArray<PrincipalInfo> allowlistInfo;
+    PrincipalInfo info;
+
+    for (auto& prin : expanded->AllowList()) {
+      rv = PrincipalToPrincipalInfo(prin, &info, aSkipBaseDomain);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      // append that spec to the allowlist
+      allowlistInfo.AppendElement(info);
+    }
+
+    *aPrincipalInfo = ExpandedPrincipalInfo(aPrincipal->OriginAttributesRef(),
+                                            std::move(allowlistInfo));
+    return NS_OK;
+  }
+
+  nsAutoCString spec;
+  rv = aPrincipal->GetAsciiSpec(spec);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCString originNoSuffix;
+  rv = aPrincipal->GetOriginNoSuffix(originNoSuffix);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIURI> domainUri;
+  rv = aPrincipal->GetDomain(getter_AddRefs(domainUri));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  Maybe<nsCString> domain;
+  if (domainUri) {
+    domain.emplace();
+    rv = domainUri->GetSpec(domain.ref());
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  // This attribute is not crucial.
+  nsCString baseDomain;
+  if (aSkipBaseDomain) {
+    baseDomain.SetIsVoid(true);
+  } else {
+    if (NS_FAILED(aPrincipal->GetBaseDomain(baseDomain))) {
+      // No warning here. Some principal URLs do not have a base-domain.
+      baseDomain.SetIsVoid(true);
+    }
+  }
+
+  *aPrincipalInfo =
+      ContentPrincipalInfo(aPrincipal->OriginAttributesRef(), originNoSuffix,
+                           spec, domain, baseDomain);
+  return NS_OK;
+}
+
+bool IsPrincipalInfoPrivate(const PrincipalInfo& aPrincipalInfo) {
+  if (aPrincipalInfo.type() != ipc::PrincipalInfo::TContentPrincipalInfo) {
+    return false;
+  }
+
+  const ContentPrincipalInfo& info = aPrincipalInfo.get_ContentPrincipalInfo();
+  return !!info.attrs().mPrivateBrowsingId;
+}
+
+already_AddRefed<nsIRedirectHistoryEntry> RHEntryInfoToRHEntry(
+    const RedirectHistoryEntryInfo& aRHEntryInfo) {
+  auto principalOrErr = PrincipalInfoToPrincipal(aRHEntryInfo.principalInfo());
+  if (NS_WARN_IF(principalOrErr.isErr())) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIPrincipal> principal = principalOrErr.unwrap();
+  nsCOMPtr<nsIURI> referrerUri = DeserializeURI(aRHEntryInfo.referrerUri());
+
+  nsCOMPtr<nsIRedirectHistoryEntry> entry = new nsRedirectHistoryEntry(
+      principal, referrerUri, aRHEntryInfo.remoteAddress());
+
+  return entry.forget();
+}
+
+nsresult RHEntryToRHEntryInfo(nsIRedirectHistoryEntry* aRHEntry,
+                              RedirectHistoryEntryInfo* aRHEntryInfo) {
+  MOZ_ASSERT(aRHEntry);
+  MOZ_ASSERT(aRHEntryInfo);
+
+  nsresult rv;
+  aRHEntry->GetRemoteAddress(aRHEntryInfo->remoteAddress());
+
+  nsCOMPtr<nsIURI> referrerUri;
+  rv = aRHEntry->GetReferrerURI(getter_AddRefs(referrerUri));
+  NS_ENSURE_SUCCESS(rv, rv);
+  SerializeURI(referrerUri, aRHEntryInfo->referrerUri());
+
+  nsCOMPtr<nsIPrincipal> principal;
+  rv = aRHEntry->GetPrincipal(getter_AddRefs(principal));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return PrincipalToPrincipalInfo(principal, &aRHEntryInfo->principalInfo());
+}
+
+nsresult LoadInfoToLoadInfoArgs(nsILoadInfo* aLoadInfo,
+                                Maybe<LoadInfoArgs>* aOptionalLoadInfoArgs) {
+  nsresult rv = NS_OK;
+  Maybe<PrincipalInfo> loadingPrincipalInfo;
+  if (nsIPrincipal* loadingPrin = aLoadInfo->GetLoadingPrincipal()) {
+    loadingPrincipalInfo.emplace();
+    rv = PrincipalToPrincipalInfo(loadingPrin, loadingPrincipalInfo.ptr());
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  PrincipalInfo triggeringPrincipalInfo;
+  rv = PrincipalToPrincipalInfo(aLoadInfo->TriggeringPrincipal(),
+                                &triggeringPrincipalInfo);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  Maybe<PrincipalInfo> principalToInheritInfo;
+  if (nsIPrincipal* principalToInherit = aLoadInfo->PrincipalToInherit()) {
+    principalToInheritInfo.emplace();
+    rv = PrincipalToPrincipalInfo(principalToInherit,
+                                  principalToInheritInfo.ptr());
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  Maybe<PrincipalInfo> topLevelPrincipalInfo;
+  if (nsIPrincipal* topLevenPrin = aLoadInfo->GetTopLevelPrincipal()) {
+    topLevelPrincipalInfo.emplace();
+    rv = PrincipalToPrincipalInfo(topLevenPrin, topLevelPrincipalInfo.ptr());
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  Maybe<URIParams> optionalResultPrincipalURI;
+  nsCOMPtr<nsIURI> resultPrincipalURI;
+  Unused << aLoadInfo->GetResultPrincipalURI(
+      getter_AddRefs(resultPrincipalURI));
+  if (resultPrincipalURI) {
+    SerializeURI(resultPrincipalURI, optionalResultPrincipalURI);
+  }
+
+  nsCString triggeringRemoteType;
+  rv = aLoadInfo->GetTriggeringRemoteType(triggeringRemoteType);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsTArray<RedirectHistoryEntryInfo> redirectChainIncludingInternalRedirects;
+  for (const nsCOMPtr<nsIRedirectHistoryEntry>& redirectEntry :
+       aLoadInfo->RedirectChainIncludingInternalRedirects()) {
+    RedirectHistoryEntryInfo* entry =
+        redirectChainIncludingInternalRedirects.AppendElement();
+    rv = RHEntryToRHEntryInfo(redirectEntry, entry);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  nsTArray<RedirectHistoryEntryInfo> redirectChain;
+  for (const nsCOMPtr<nsIRedirectHistoryEntry>& redirectEntry :
+       aLoadInfo->RedirectChain()) {
+    RedirectHistoryEntryInfo* entry = redirectChain.AppendElement();
+    rv = RHEntryToRHEntryInfo(redirectEntry, entry);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  Maybe<IPCClientInfo> ipcClientInfo;
+  const Maybe<ClientInfo>& clientInfo = aLoadInfo->GetClientInfo();
+  if (clientInfo.isSome()) {
+    ipcClientInfo.emplace(clientInfo.ref().ToIPC());
+  }
+
+  Maybe<IPCClientInfo> ipcReservedClientInfo;
+  const Maybe<ClientInfo>& reservedClientInfo =
+      aLoadInfo->GetReservedClientInfo();
+  if (reservedClientInfo.isSome()) {
+    ipcReservedClientInfo.emplace(reservedClientInfo.ref().ToIPC());
+  }
+
+  Maybe<IPCClientInfo> ipcInitialClientInfo;
+  const Maybe<ClientInfo>& initialClientInfo =
+      aLoadInfo->GetInitialClientInfo();
+  if (initialClientInfo.isSome()) {
+    ipcInitialClientInfo.emplace(initialClientInfo.ref().ToIPC());
+  }
+
+  Maybe<IPCServiceWorkerDescriptor> ipcController;
+  const Maybe<ServiceWorkerDescriptor>& controller = aLoadInfo->GetController();
+  if (controller.isSome()) {
+    ipcController.emplace(controller.ref().ToIPC());
+  }
+
+  nsAutoString cspNonce;
+  Unused << NS_WARN_IF(NS_FAILED(aLoadInfo->GetCspNonce(cspNonce)));
+
+  nsCOMPtr<nsICookieJarSettings> cookieJarSettings;
+  rv = aLoadInfo->GetCookieJarSettings(getter_AddRefs(cookieJarSettings));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  CookieJarSettingsArgs cookieJarSettingsArgs;
+  static_cast<CookieJarSettings*>(cookieJarSettings.get())
+      ->Serialize(cookieJarSettingsArgs);
+
+  Maybe<CSPInfo> maybeCspToInheritInfo;
+  nsCOMPtr<nsIContentSecurityPolicy> cspToInherit =
+      aLoadInfo->GetCspToInherit();
+  if (cspToInherit) {
+    CSPInfo cspToInheritInfo;
+    Unused << NS_WARN_IF(
+        NS_FAILED(CSPToCSPInfo(cspToInherit, &cspToInheritInfo)));
+    maybeCspToInheritInfo.emplace(cspToInheritInfo);
+  }
+
+  nsCOMPtr<nsIURI> unstrippedURI;
+  Unused << aLoadInfo->GetUnstrippedURI(getter_AddRefs(unstrippedURI));
+
+  Maybe<bool> isThirdPartyContextToTopWindow;
+  if (static_cast<LoadInfo*>(aLoadInfo)
+          ->HasIsThirdPartyContextToTopWindowSet()) {
+    isThirdPartyContextToTopWindow.emplace(
+        aLoadInfo->GetIsThirdPartyContextToTopWindow());
+  }
+
+  Maybe<InterceptionInfoArg> interceptionInfoArg;
+  nsIInterceptionInfo* interceptionInfo = aLoadInfo->InterceptionInfo();
+  if (interceptionInfo) {
+    Maybe<PrincipalInfo> triggeringPrincipalInfo;
+    if (interceptionInfo->TriggeringPrincipal()) {
+      triggeringPrincipalInfo.emplace();
+      rv = PrincipalToPrincipalInfo(interceptionInfo->TriggeringPrincipal(),
+                                    triggeringPrincipalInfo.ptr());
+    }
+
+    nsTArray<RedirectHistoryEntryInfo> redirectChain;
+    for (const nsCOMPtr<nsIRedirectHistoryEntry>& redirectEntry :
+         interceptionInfo->RedirectChain()) {
+      RedirectHistoryEntryInfo* entry = redirectChain.AppendElement();
+      rv = RHEntryToRHEntryInfo(redirectEntry, entry);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    interceptionInfoArg = Some(InterceptionInfoArg(
+        triggeringPrincipalInfo, interceptionInfo->ContentPolicyType(),
+        redirectChain, interceptionInfo->FromThirdParty()));
+  }
+
+  *aOptionalLoadInfoArgs = Some(LoadInfoArgs(
+      loadingPrincipalInfo, triggeringPrincipalInfo, principalToInheritInfo,
+      topLevelPrincipalInfo, optionalResultPrincipalURI, triggeringRemoteType,
+      aLoadInfo->GetSandboxedNullPrincipalID(), aLoadInfo->GetSecurityFlags(),
+      aLoadInfo->GetSandboxFlags(), aLoadInfo->GetTriggeringSandboxFlags(),
+      aLoadInfo->InternalContentPolicyType(),
+      static_cast<uint32_t>(aLoadInfo->GetTainting()),
+      aLoadInfo->GetBlockAllMixedContent(),
+      aLoadInfo->GetUpgradeInsecureRequests(),
+      aLoadInfo->GetBrowserUpgradeInsecureRequests(),
+      aLoadInfo->GetBrowserDidUpgradeInsecureRequests(),
+      aLoadInfo->GetBrowserWouldUpgradeInsecureRequests(),
+      aLoadInfo->GetForceAllowDataURI(),
+      aLoadInfo->GetAllowInsecureRedirectToDataURI(),
+      aLoadInfo->GetSkipContentPolicyCheckForWebRequest(),
+      aLoadInfo->GetOriginalFrameSrcLoad(),
+      aLoadInfo->GetForceInheritPrincipalDropped(),
+      aLoadInfo->GetInnerWindowID(), aLoadInfo->GetBrowsingContextID(),
+      aLoadInfo->GetFrameBrowsingContextID(),
+      aLoadInfo->GetInitialSecurityCheckDone(),
+      aLoadInfo->GetIsInThirdPartyContext(), isThirdPartyContextToTopWindow,
+      aLoadInfo->GetIsFormSubmission(), aLoadInfo->GetSendCSPViolationEvents(),
+      aLoadInfo->GetOriginAttributes(), redirectChainIncludingInternalRedirects,
+      redirectChain, aLoadInfo->GetHasInjectedCookieForCookieBannerHandling(),
+      ipcClientInfo, ipcReservedClientInfo, ipcInitialClientInfo, ipcController,
+      aLoadInfo->CorsUnsafeHeaders(), aLoadInfo->GetForcePreflight(),
+      aLoadInfo->GetIsPreflight(), aLoadInfo->GetLoadTriggeredFromExternal(),
+      aLoadInfo->GetServiceWorkerTaintingSynthesized(),
+      aLoadInfo->GetDocumentHasUserInteracted(),
+      aLoadInfo->GetAllowListFutureDocumentsCreatedFromThisRedirectChain(),
+      aLoadInfo->GetNeedForCheckingAntiTrackingHeuristic(), cspNonce,
+      aLoadInfo->GetSkipContentSniffing(), aLoadInfo->GetHttpsOnlyStatus(),
+      aLoadInfo->GetHstsStatus(), aLoadInfo->GetHasValidUserGestureActivation(),
+      aLoadInfo->GetAllowDeprecatedSystemRequests(),
+      aLoadInfo->GetIsInDevToolsContext(), aLoadInfo->GetParserCreatedScript(),
+      aLoadInfo->GetIsFromProcessingFrameAttributes(),
+      aLoadInfo->GetIsMediaRequest(), aLoadInfo->GetIsMediaInitialRequest(),
+      aLoadInfo->GetIsFromObjectOrEmbed(), cookieJarSettingsArgs,
+      aLoadInfo->GetRequestBlockingReason(), maybeCspToInheritInfo,
+      aLoadInfo->GetStoragePermission(), aLoadInfo->GetIsMetaRefresh(),
+      aLoadInfo->GetLoadingEmbedderPolicy(),
+      aLoadInfo->GetIsOriginTrialCoepCredentiallessEnabledForTopLevel(),
+      unstrippedURI, interceptionInfoArg));
+
+  return NS_OK;
+}
+
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, nsILoadInfo** outLoadInfo) {
+  return LoadInfoArgsToLoadInfo(aOptionalLoadInfoArgs, aOriginRemoteType,
+                                nullptr, outLoadInfo);
+}
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, nsINode* aCspToInheritLoadingContext,
+    nsILoadInfo** outLoadInfo) {
+  RefPtr<LoadInfo> loadInfo;
+  nsresult rv = LoadInfoArgsToLoadInfo(aOptionalLoadInfoArgs, aOriginRemoteType,
+                                       aCspToInheritLoadingContext,
+                                       getter_AddRefs(loadInfo));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  loadInfo.forget(outLoadInfo);
+  return NS_OK;
+}
+
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, LoadInfo** outLoadInfo) {
+  return LoadInfoArgsToLoadInfo(aOptionalLoadInfoArgs, aOriginRemoteType,
+                                nullptr, outLoadInfo);
+}
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, nsINode* aCspToInheritLoadingContext,
+    LoadInfo** outLoadInfo) {
+  if (aOptionalLoadInfoArgs.isNothing()) {
+    *outLoadInfo = nullptr;
+    return NS_OK;
+  }
+
+  const LoadInfoArgs& loadInfoArgs = aOptionalLoadInfoArgs.ref();
+
+  nsCOMPtr<nsIPrincipal> loadingPrincipal;
+  if (loadInfoArgs.requestingPrincipalInfo().isSome()) {
+    auto loadingPrincipalOrErr =
+        PrincipalInfoToPrincipal(loadInfoArgs.requestingPrincipalInfo().ref());
+    if (NS_WARN_IF(loadingPrincipalOrErr.isErr())) {
+      return loadingPrincipalOrErr.unwrapErr();
+    }
+    loadingPrincipal = loadingPrincipalOrErr.unwrap();
+  }
+
+  auto triggeringPrincipalOrErr =
+      PrincipalInfoToPrincipal(loadInfoArgs.triggeringPrincipalInfo());
+  if (NS_WARN_IF(triggeringPrincipalOrErr.isErr())) {
+    return triggeringPrincipalOrErr.unwrapErr();
+  }
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal =
+      triggeringPrincipalOrErr.unwrap();
+
+  nsCOMPtr<nsIPrincipal> principalToInherit;
+  nsCOMPtr<nsIPrincipal> flattenedPrincipalToInherit;
+  if (loadInfoArgs.principalToInheritInfo().isSome()) {
+    auto principalToInheritOrErr =
+        PrincipalInfoToPrincipal(loadInfoArgs.principalToInheritInfo().ref());
+    if (NS_WARN_IF(principalToInheritOrErr.isErr())) {
+      return principalToInheritOrErr.unwrapErr();
+    }
+    flattenedPrincipalToInherit = principalToInheritOrErr.unwrap();
+  }
+
+  if (XRE_IsContentProcess()) {
+    auto targetBrowsingContextId = loadInfoArgs.frameBrowsingContextID()
+                                       ? loadInfoArgs.frameBrowsingContextID()
+                                       : loadInfoArgs.browsingContextID();
+    if (RefPtr<BrowsingContext> bc =
+            BrowsingContext::Get(targetBrowsingContextId)) {
+      auto [originalTriggeringPrincipal, originalPrincipalToInherit] =
+          bc->GetTriggeringAndInheritPrincipalsForCurrentLoad();
+
+      if (originalTriggeringPrincipal &&
+          originalTriggeringPrincipal->Equals(triggeringPrincipal)) {
+        triggeringPrincipal = originalTriggeringPrincipal;
+      }
+      if (originalPrincipalToInherit &&
+          (loadInfoArgs.securityFlags() &
+           nsILoadInfo::SEC_FORCE_INHERIT_PRINCIPAL) &&
+          originalPrincipalToInherit->Equals(flattenedPrincipalToInherit)) {
+        principalToInherit = originalPrincipalToInherit;
+      }
+    }
+  }
+  if (!principalToInherit && loadInfoArgs.principalToInheritInfo().isSome()) {
+    principalToInherit = flattenedPrincipalToInherit;
+  }
+
+  nsCOMPtr<nsIPrincipal> topLevelPrincipal;
+  if (loadInfoArgs.topLevelPrincipalInfo().isSome()) {
+    auto topLevelPrincipalOrErr =
+        PrincipalInfoToPrincipal(loadInfoArgs.topLevelPrincipalInfo().ref());
+    if (NS_WARN_IF(topLevelPrincipalOrErr.isErr())) {
+      return topLevelPrincipalOrErr.unwrapErr();
+    }
+    topLevelPrincipal = topLevelPrincipalOrErr.unwrap();
+  }
+
+  nsCOMPtr<nsIURI> resultPrincipalURI;
+  if (loadInfoArgs.resultPrincipalURI().isSome()) {
+    resultPrincipalURI = DeserializeURI(loadInfoArgs.resultPrincipalURI());
+    NS_ENSURE_TRUE(resultPrincipalURI, NS_ERROR_UNEXPECTED);
+  }
+
+  // If we received this message from a content process, reset
+  // triggeringRemoteType to the process which sent us the message. If the
+  // parent sent us the message, we trust it to provide the correct triggering
+  // remote type.
+  //
+  // This means that the triggering remote type will be reset if a LoadInfo is
+  // bounced through a content process, as the LoadInfo can no longer be
+  // validated to be coming from the originally specified remote type.
+  nsCString triggeringRemoteType = loadInfoArgs.triggeringRemoteType();
+  if (aOriginRemoteType != NOT_REMOTE_TYPE &&
+      aOriginRemoteType != triggeringRemoteType) {
+    triggeringRemoteType = aOriginRemoteType;
+  }
+
+  RedirectHistoryArray redirectChainIncludingInternalRedirects;
+  for (const RedirectHistoryEntryInfo& entryInfo :
+       loadInfoArgs.redirectChainIncludingInternalRedirects()) {
+    nsCOMPtr<nsIRedirectHistoryEntry> redirectHistoryEntry =
+        RHEntryInfoToRHEntry(entryInfo);
+    NS_ENSURE_TRUE(redirectHistoryEntry, NS_ERROR_UNEXPECTED);
+    redirectChainIncludingInternalRedirects.AppendElement(
+        redirectHistoryEntry.forget());
+  }
+
+  RedirectHistoryArray redirectChain;
+  for (const RedirectHistoryEntryInfo& entryInfo :
+       loadInfoArgs.redirectChain()) {
+    nsCOMPtr<nsIRedirectHistoryEntry> redirectHistoryEntry =
+        RHEntryInfoToRHEntry(entryInfo);
+    NS_ENSURE_TRUE(redirectHistoryEntry, NS_ERROR_UNEXPECTED);
+    redirectChain.AppendElement(redirectHistoryEntry.forget());
+  }
+  nsTArray<nsCOMPtr<nsIPrincipal>> ancestorPrincipals;
+  nsTArray<uint64_t> ancestorBrowsingContextIDs;
+  if (XRE_IsParentProcess() &&
+      (nsContentUtils::InternalContentPolicyTypeToExternal(
+           loadInfoArgs.contentPolicyType()) !=
+       ExtContentPolicy::TYPE_DOCUMENT)) {
+    // Only fill out ancestor principals and browsing context IDs when we
+    // are deserializing LoadInfoArgs to be LoadInfo for a subresource
+    RefPtr<BrowsingContext> parentBC =
+        BrowsingContext::Get(loadInfoArgs.browsingContextID());
+    if (parentBC) {
+      LoadInfo::ComputeAncestors(parentBC->Canonical(), ancestorPrincipals,
+                                 ancestorBrowsingContextIDs);
+    }
+  }
+
+  Maybe<ClientInfo> clientInfo;
+  if (loadInfoArgs.clientInfo().isSome()) {
+    clientInfo.emplace(ClientInfo(loadInfoArgs.clientInfo().ref()));
+  }
+
+  Maybe<ClientInfo> reservedClientInfo;
+  if (loadInfoArgs.reservedClientInfo().isSome()) {
+    reservedClientInfo.emplace(
+        ClientInfo(loadInfoArgs.reservedClientInfo().ref()));
+  }
+
+  Maybe<ClientInfo> initialClientInfo;
+  if (loadInfoArgs.initialClientInfo().isSome()) {
+    initialClientInfo.emplace(
+        ClientInfo(loadInfoArgs.initialClientInfo().ref()));
+  }
+
+  // We can have an initial client info or a reserved client info, but not both.
+  MOZ_DIAGNOSTIC_ASSERT(reservedClientInfo.isNothing() ||
+                        initialClientInfo.isNothing());
+  NS_ENSURE_TRUE(
+      reservedClientInfo.isNothing() || initialClientInfo.isNothing(),
+      NS_ERROR_UNEXPECTED);
+
+  Maybe<ServiceWorkerDescriptor> controller;
+  if (loadInfoArgs.controller().isSome()) {
+    controller.emplace(
+        ServiceWorkerDescriptor(loadInfoArgs.controller().ref()));
+  }
+
+  nsCOMPtr<nsICookieJarSettings> cookieJarSettings;
+  CookieJarSettings::Deserialize(loadInfoArgs.cookieJarSettings(),
+                                 getter_AddRefs(cookieJarSettings));
+
+  nsCOMPtr<nsIContentSecurityPolicy> cspToInherit;
+  Maybe<mozilla::ipc::CSPInfo> cspToInheritInfo =
+      loadInfoArgs.cspToInheritInfo();
+  if (cspToInheritInfo.isSome()) {
+    nsCOMPtr<Document> doc = do_QueryInterface(aCspToInheritLoadingContext);
+    cspToInherit = CSPInfoToCSP(cspToInheritInfo.ref(), doc);
+  }
+
+  // Restore the loadingContext for frames using the BrowsingContext's
+  // embedder element. Note that this only works if the embedder is
+  // same-process, so won't be fission compatible.
+  nsCOMPtr<nsINode> loadingContext;
+  RefPtr<BrowsingContext> frameBrowsingContext =
+      BrowsingContext::Get(loadInfoArgs.frameBrowsingContextID());
+  if (frameBrowsingContext) {
+    loadingContext = frameBrowsingContext->GetEmbedderElement();
+  }
+
+  Maybe<bool> isThirdPartyContextToTopWindow;
+  if (loadInfoArgs.isThirdPartyContextToTopWindow().isSome()) {
+    isThirdPartyContextToTopWindow.emplace(
+        loadInfoArgs.isThirdPartyContextToTopWindow().ref());
+  }
+
+  nsCOMPtr<nsIInterceptionInfo> interceptionInfo;
+  if (loadInfoArgs.interceptionInfo().isSome()) {
+    const InterceptionInfoArg& interceptionInfoArg =
+        loadInfoArgs.interceptionInfo().ref();
+    nsCOMPtr<nsIPrincipal> triggeringPrincipal;
+    if (interceptionInfoArg.triggeringPrincipalInfo().isSome()) {
+      auto triggeringPrincipalOrErr = PrincipalInfoToPrincipal(
+          interceptionInfoArg.triggeringPrincipalInfo().ref());
+      if (NS_WARN_IF(triggeringPrincipalOrErr.isErr())) {
+        return triggeringPrincipalOrErr.unwrapErr();
+      }
+      triggeringPrincipal = triggeringPrincipalOrErr.unwrap();
+    }
+
+    RedirectHistoryArray redirectChain;
+    for (const RedirectHistoryEntryInfo& entryInfo :
+         interceptionInfoArg.redirectChain()) {
+      nsCOMPtr<nsIRedirectHistoryEntry> redirectHistoryEntry =
+          RHEntryInfoToRHEntry(entryInfo);
+      NS_ENSURE_TRUE(redirectHistoryEntry, NS_ERROR_UNEXPECTED);
+      redirectChain.AppendElement(redirectHistoryEntry.forget());
+    }
+
+    interceptionInfo = new InterceptionInfo(
+        triggeringPrincipal, interceptionInfoArg.contentPolicyType(),
+        redirectChain, interceptionInfoArg.fromThirdParty());
+  }
+
+  RefPtr<mozilla::net::LoadInfo> loadInfo = new mozilla::net::LoadInfo(
+      loadingPrincipal, triggeringPrincipal, principalToInherit,
+      topLevelPrincipal, resultPrincipalURI, cookieJarSettings, cspToInherit,
+      triggeringRemoteType, loadInfoArgs.sandboxedNullPrincipalID(), clientInfo,
+      reservedClientInfo, initialClientInfo, controller,
+      loadInfoArgs.securityFlags(), loadInfoArgs.sandboxFlags(),
+      loadInfoArgs.triggeringSandboxFlags(), loadInfoArgs.contentPolicyType(),
+      static_cast<LoadTainting>(loadInfoArgs.tainting()),
+      loadInfoArgs.blockAllMixedContent(),
+      loadInfoArgs.upgradeInsecureRequests(),
+      loadInfoArgs.browserUpgradeInsecureRequests(),
+      loadInfoArgs.browserDidUpgradeInsecureRequests(),
+      loadInfoArgs.browserWouldUpgradeInsecureRequests(),
+      loadInfoArgs.forceAllowDataURI(),
+      loadInfoArgs.allowInsecureRedirectToDataURI(),
+      loadInfoArgs.skipContentPolicyCheckForWebRequest(),
+      loadInfoArgs.originalFrameSrcLoad(),
+      loadInfoArgs.forceInheritPrincipalDropped(), loadInfoArgs.innerWindowID(),
+      loadInfoArgs.browsingContextID(), loadInfoArgs.frameBrowsingContextID(),
+      loadInfoArgs.initialSecurityCheckDone(),
+      loadInfoArgs.isInThirdPartyContext(), isThirdPartyContextToTopWindow,
+      loadInfoArgs.isFormSubmission(), loadInfoArgs.sendCSPViolationEvents(),
+      loadInfoArgs.originAttributes(),
+      std::move(redirectChainIncludingInternalRedirects),
+      std::move(redirectChain), std::move(ancestorPrincipals),
+      ancestorBrowsingContextIDs, loadInfoArgs.corsUnsafeHeaders(),
+      loadInfoArgs.forcePreflight(), loadInfoArgs.isPreflight(),
+      loadInfoArgs.loadTriggeredFromExternal(),
+      loadInfoArgs.serviceWorkerTaintingSynthesized(),
+      loadInfoArgs.documentHasUserInteracted(),
+      loadInfoArgs.allowListFutureDocumentsCreatedFromThisRedirectChain(),
+      loadInfoArgs.needForCheckingAntiTrackingHeuristic(),
+      loadInfoArgs.cspNonce(), loadInfoArgs.skipContentSniffing(),
+      loadInfoArgs.httpsOnlyStatus(), loadInfoArgs.hstsStatus(),
+      loadInfoArgs.hasValidUserGestureActivation(),
+      loadInfoArgs.allowDeprecatedSystemRequests(),
+      loadInfoArgs.isInDevToolsContext(), loadInfoArgs.parserCreatedScript(),
+      loadInfoArgs.storagePermission(), loadInfoArgs.isMetaRefresh(),
+      loadInfoArgs.requestBlockingReason(), loadingContext,
+      loadInfoArgs.loadingEmbedderPolicy(),
+      loadInfoArgs.originTrialCoepCredentiallessEnabledForTopLevel(),
+      loadInfoArgs.unstrippedURI(), interceptionInfo,
+      loadInfoArgs.hasInjectedCookieForCookieBannerHandling());
+
+  if (loadInfoArgs.isFromProcessingFrameAttributes()) {
+    loadInfo->SetIsFromProcessingFrameAttributes();
+  }
+
+  if (loadInfoArgs.isMediaRequest()) {
+    loadInfo->SetIsMediaRequest(true);
+
+    if (loadInfoArgs.isMediaInitialRequest()) {
+      loadInfo->SetIsMediaInitialRequest(true);
+    }
+  }
+
+  if (loadInfoArgs.isFromObjectOrEmbed()) {
+    loadInfo->SetIsFromObjectOrEmbed(true);
+  }
+
+  loadInfo.forget(outLoadInfo);
+  return NS_OK;
+}
+
+void LoadInfoToParentLoadInfoForwarder(
+    nsILoadInfo* aLoadInfo, ParentLoadInfoForwarderArgs* aForwarderArgsOut) {
+  Maybe<IPCServiceWorkerDescriptor> ipcController;
+  Maybe<ServiceWorkerDescriptor> controller(aLoadInfo->GetController());
+  if (controller.isSome()) {
+    ipcController.emplace(controller.ref().ToIPC());
+  }
+
+  uint32_t tainting = nsILoadInfo::TAINTING_BASIC;
+  Unused << aLoadInfo->GetTainting(&tainting);
+
+  Maybe<CookieJarSettingsArgs> cookieJarSettingsArgs;
+
+  nsCOMPtr<nsICookieJarSettings> cookieJarSettings;
+  nsresult rv =
+      aLoadInfo->GetCookieJarSettings(getter_AddRefs(cookieJarSettings));
+  CookieJarSettings* cs =
+      static_cast<CookieJarSettings*>(cookieJarSettings.get());
+  if (NS_SUCCEEDED(rv) && cookieJarSettings && cs->HasBeenChanged()) {
+    CookieJarSettingsArgs args;
+    cs->Serialize(args);
+    cookieJarSettingsArgs = Some(args);
+  }
+
+  nsCOMPtr<nsIURI> unstrippedURI;
+  Unused << aLoadInfo->GetUnstrippedURI(getter_AddRefs(unstrippedURI));
+
+  Maybe<bool> isThirdPartyContextToTopWindow;
+  if (static_cast<LoadInfo*>(aLoadInfo)
+          ->HasIsThirdPartyContextToTopWindowSet()) {
+    isThirdPartyContextToTopWindow.emplace(
+        aLoadInfo->GetIsThirdPartyContextToTopWindow());
+  }
+
+  *aForwarderArgsOut = ParentLoadInfoForwarderArgs(
+      aLoadInfo->GetAllowInsecureRedirectToDataURI(), ipcController, tainting,
+      aLoadInfo->GetSkipContentSniffing(), aLoadInfo->GetHttpsOnlyStatus(),
+      aLoadInfo->GetHstsStatus(), aLoadInfo->GetHasValidUserGestureActivation(),
+      aLoadInfo->GetAllowDeprecatedSystemRequests(),
+      aLoadInfo->GetIsInDevToolsContext(), aLoadInfo->GetParserCreatedScript(),
+      aLoadInfo->GetTriggeringSandboxFlags(),
+      aLoadInfo->GetServiceWorkerTaintingSynthesized(),
+      aLoadInfo->GetDocumentHasUserInteracted(),
+      aLoadInfo->GetAllowListFutureDocumentsCreatedFromThisRedirectChain(),
+      cookieJarSettingsArgs, aLoadInfo->GetRequestBlockingReason(),
+      aLoadInfo->GetStoragePermission(), aLoadInfo->GetIsMetaRefresh(),
+      isThirdPartyContextToTopWindow, aLoadInfo->GetIsInThirdPartyContext(),
+      unstrippedURI);
+}
+
+nsresult MergeParentLoadInfoForwarder(
+    ParentLoadInfoForwarderArgs const& aForwarderArgs, nsILoadInfo* aLoadInfo) {
+  nsresult rv;
+
+  rv = aLoadInfo->SetAllowInsecureRedirectToDataURI(
+      aForwarderArgs.allowInsecureRedirectToDataURI());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aLoadInfo->ClearController();
+  auto& controller = aForwarderArgs.controller();
+  if (controller.isSome()) {
+    aLoadInfo->SetController(ServiceWorkerDescriptor(controller.ref()));
+  }
+
+  if (aForwarderArgs.serviceWorkerTaintingSynthesized()) {
+    aLoadInfo->SynthesizeServiceWorkerTainting(
+        static_cast<LoadTainting>(aForwarderArgs.tainting()));
+  } else {
+    aLoadInfo->MaybeIncreaseTainting(aForwarderArgs.tainting());
+  }
+
+  rv = aLoadInfo->SetSkipContentSniffing(aForwarderArgs.skipContentSniffing());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetHttpsOnlyStatus(aForwarderArgs.httpsOnlyStatus());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetHstsStatus(aForwarderArgs.hstsStatus());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetTriggeringSandboxFlags(
+      aForwarderArgs.triggeringSandboxFlags());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetHasValidUserGestureActivation(
+      aForwarderArgs.hasValidUserGestureActivation());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetAllowDeprecatedSystemRequests(
+      aForwarderArgs.allowDeprecatedSystemRequests());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetIsInDevToolsContext(aForwarderArgs.isInDevToolsContext());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetParserCreatedScript(aForwarderArgs.parserCreatedScript());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  MOZ_ALWAYS_SUCCEEDS(aLoadInfo->SetDocumentHasUserInteracted(
+      aForwarderArgs.documentHasUserInteracted()));
+  MOZ_ALWAYS_SUCCEEDS(
+      aLoadInfo->SetAllowListFutureDocumentsCreatedFromThisRedirectChain(
+          aForwarderArgs
+              .allowListFutureDocumentsCreatedFromThisRedirectChain()));
+  MOZ_ALWAYS_SUCCEEDS(aLoadInfo->SetRequestBlockingReason(
+      aForwarderArgs.requestBlockingReason()));
+
+  const Maybe<CookieJarSettingsArgs>& cookieJarSettingsArgs =
+      aForwarderArgs.cookieJarSettings();
+  if (cookieJarSettingsArgs.isSome()) {
+    nsCOMPtr<nsICookieJarSettings> cookieJarSettings;
+    nsresult rv =
+        aLoadInfo->GetCookieJarSettings(getter_AddRefs(cookieJarSettings));
+    if (NS_SUCCEEDED(rv) && cookieJarSettings) {
+      static_cast<CookieJarSettings*>(cookieJarSettings.get())
+          ->Merge(cookieJarSettingsArgs.ref());
+    }
+  }
+
+  rv = aLoadInfo->SetStoragePermission(aForwarderArgs.storagePermission());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetIsMetaRefresh(aForwarderArgs.isMetaRefresh());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  static_cast<LoadInfo*>(aLoadInfo)->ClearIsThirdPartyContextToTopWindow();
+  if (aForwarderArgs.isThirdPartyContextToTopWindow().isSome()) {
+    rv = aLoadInfo->SetIsThirdPartyContextToTopWindow(
+        aForwarderArgs.isThirdPartyContextToTopWindow().ref());
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetIsInThirdPartyContext(
+      aForwarderArgs.isInThirdPartyContext());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aLoadInfo->SetUnstrippedURI(aForwarderArgs.unstrippedURI());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+void LoadInfoToChildLoadInfoForwarder(
+    nsILoadInfo* aLoadInfo, ChildLoadInfoForwarderArgs* aForwarderArgsOut) {
+  Maybe<IPCClientInfo> ipcReserved;
+  Maybe<ClientInfo> reserved(aLoadInfo->GetReservedClientInfo());
+  if (reserved.isSome()) {
+    ipcReserved.emplace(reserved.ref().ToIPC());
+  }
+
+  Maybe<IPCClientInfo> ipcInitial;
+  Maybe<ClientInfo> initial(aLoadInfo->GetInitialClientInfo());
+  if (initial.isSome()) {
+    ipcInitial.emplace(initial.ref().ToIPC());
+  }
+
+  Maybe<IPCServiceWorkerDescriptor> ipcController;
+  Maybe<ServiceWorkerDescriptor> controller(aLoadInfo->GetController());
+  if (controller.isSome()) {
+    ipcController.emplace(controller.ref().ToIPC());
+  }
+
+  *aForwarderArgsOut =
+      ChildLoadInfoForwarderArgs(ipcReserved, ipcInitial, ipcController,
+                                 aLoadInfo->GetRequestBlockingReason());
+}
+
+nsresult MergeChildLoadInfoForwarder(
+    const ChildLoadInfoForwarderArgs& aForwarderArgs, nsILoadInfo* aLoadInfo) {
+  Maybe<ClientInfo> reservedClientInfo;
+  auto& ipcReserved = aForwarderArgs.reservedClientInfo();
+  if (ipcReserved.isSome()) {
+    reservedClientInfo.emplace(ClientInfo(ipcReserved.ref()));
+  }
+
+  Maybe<ClientInfo> initialClientInfo;
+  auto& ipcInitial = aForwarderArgs.initialClientInfo();
+  if (ipcInitial.isSome()) {
+    initialClientInfo.emplace(ClientInfo(ipcInitial.ref()));
+  }
+
+  // There should only be at most one reserved or initial ClientInfo.
+  if (NS_WARN_IF(reservedClientInfo.isSome() && initialClientInfo.isSome())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // If we received no reserved or initial ClientInfo, then we must not
+  // already have one set.  There are no use cases where this should
+  // happen and we don't have a way to clear the current value.
+  if (NS_WARN_IF(reservedClientInfo.isNothing() &&
+                 initialClientInfo.isNothing() &&
+                 (aLoadInfo->GetReservedClientInfo().isSome() ||
+                  aLoadInfo->GetInitialClientInfo().isSome()))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (reservedClientInfo.isSome()) {
+    // We need to override here instead of simply set the value.  This
+    // allows us to change the reserved client.  This is necessary when
+    // the ClientChannelHelper created a new reserved client in the
+    // child-side of the redirect.
+    aLoadInfo->OverrideReservedClientInfoInParent(reservedClientInfo.ref());
+  } else if (initialClientInfo.isSome()) {
+    aLoadInfo->SetInitialClientInfo(initialClientInfo.ref());
+  }
+
+  aLoadInfo->ClearController();
+  auto& controller = aForwarderArgs.controller();
+  if (controller.isSome()) {
+    aLoadInfo->SetController(ServiceWorkerDescriptor(controller.ref()));
+  }
+
+  uint32_t blockingReason = aForwarderArgs.requestBlockingReason();
+  if (blockingReason) {
+    // We only want to override when non-null, so that any earlier set non-null
+    // value is not reverted to 0.
+    aLoadInfo->SetRequestBlockingReason(blockingReason);
+  }
+
+  return NS_OK;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/BackgroundUtils.h b/ipc/glue/BackgroundUtils.h
new file mode 100644
index 0000000000..db1d48d2e0
--- /dev/null
+++ b/ipc/glue/BackgroundUtils.h
@@ -0,0 +1,195 @@
+/* -*- 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_ipc_backgroundutils_h__
+#define mozilla_ipc_backgroundutils_h__
+
+#include "ipc/IPCMessageUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/OriginAttributes.h"
+#include "nsCOMPtr.h"
+#include "nscore.h"
+
+class nsIContentSecurityPolicy;
+class nsILoadInfo;
+class nsINode;
+class nsIPrincipal;
+class nsIRedirectHistoryEntry;
+
+namespace IPC {
+
+namespace detail {
+template <class ParamType>
+struct OriginAttributesParamTraits {
+  typedef ParamType paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    nsAutoCString suffix;
+    aParam.CreateSuffix(suffix);
+    WriteParam(aWriter, suffix);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    nsAutoCString suffix;
+    return ReadParam(aReader, &suffix) && aResult->PopulateFromSuffix(suffix);
+  }
+};
+}  // namespace detail
+
+template <>
+struct ParamTraits<mozilla::OriginAttributes>
+    : public detail::OriginAttributesParamTraits<mozilla::OriginAttributes> {};
+
+}  // namespace IPC
+
+namespace mozilla {
+
+namespace dom {
+class Document;
+}
+
+namespace net {
+class ChildLoadInfoForwarderArgs;
+class LoadInfoArgs;
+class LoadInfo;
+class ParentLoadInfoForwarderArgs;
+class RedirectHistoryEntryInfo;
+}  // namespace net
+
+namespace ipc {
+
+class ContentSecurityPolicy;
+class CSPInfo;
+class PrincipalInfo;
+
+/**
+ * Convert a PrincipalInfo to an nsIPrincipal.
+ *
+ * MUST be called on the main thread.
+ */
+Result<nsCOMPtr<nsIPrincipal>, nsresult> PrincipalInfoToPrincipal(
+    const PrincipalInfo& aPrincipalInfo);
+
+/**
+ * Convert an nsIPrincipal to a PrincipalInfo.
+ *
+ * MUST be called on the main thread only.
+ */
+nsresult PrincipalToPrincipalInfo(nsIPrincipal* aPrincipal,
+                                  PrincipalInfo* aPrincipalInfo,
+                                  bool aSkipBaseDomain = false);
+
+/**
+ * Compare storage keys for equivalence.
+ *
+ * Only use with storage keys retrieved from nsIGlobalObject::GetStorageKey!
+ * Bug 1776271 tracks enhancing this into a proper type.
+ */
+bool StorageKeysEqual(const PrincipalInfo& aLeft, const PrincipalInfo& aRight);
+
+/**
+ * Convert a CSPInfo to an nsIContentSecurityPolicy.
+ *
+ * MUST be called on the main thread only.
+ *
+ * If possible, provide a requesting doc, so policy violation events can
+ * be dispatched correctly. If aRequestingDoc is null, then the CSPInfo holds
+ * the necessary fallback information, like a serialized requestPrincipal,
+ * to generate a valid nsIContentSecurityPolicy.
+ */
+already_AddRefed<nsIContentSecurityPolicy> CSPInfoToCSP(
+    const CSPInfo& aCSPInfo, mozilla::dom::Document* aRequestingDoc,
+    nsresult* aOptionalResult = nullptr);
+
+/**
+ * Convert an nsIContentSecurityPolicy to a CSPInfo.
+ *
+ * MUST be called on the main thread only.
+ */
+nsresult CSPToCSPInfo(nsIContentSecurityPolicy* aCSP, CSPInfo* aCSPInfo);
+
+/**
+ * Return true if this PrincipalInfo is a content principal and it has
+ * a privateBrowsing id in its OriginAttributes
+ */
+bool IsPrincipalInfoPrivate(const PrincipalInfo& aPrincipalInfo);
+
+/**
+ * Convert an RedirectHistoryEntryInfo to a nsIRedirectHistoryEntry.
+ */
+
+already_AddRefed<nsIRedirectHistoryEntry> RHEntryInfoToRHEntry(
+    const mozilla::net::RedirectHistoryEntryInfo& aRHEntryInfo);
+
+/**
+ * Convert an nsIRedirectHistoryEntry to a RedirectHistoryEntryInfo.
+ */
+
+nsresult RHEntryToRHEntryInfo(
+    nsIRedirectHistoryEntry* aRHEntry,
+    mozilla::net::RedirectHistoryEntryInfo* aRHEntryInfo);
+
+/**
+ * Convert a LoadInfo to LoadInfoArgs struct.
+ */
+nsresult LoadInfoToLoadInfoArgs(
+    nsILoadInfo* aLoadInfo,
+    Maybe<mozilla::net::LoadInfoArgs>* outOptionalLoadInfoArgs);
+
+/**
+ * Convert LoadInfoArgs to a LoadInfo.
+ */
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<mozilla::net::LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, nsILoadInfo** outLoadInfo);
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<mozilla::net::LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, nsINode* aCspToInheritLoadingContext,
+    nsILoadInfo** outLoadInfo);
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<net::LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, mozilla::net::LoadInfo** outLoadInfo);
+nsresult LoadInfoArgsToLoadInfo(
+    const Maybe<net::LoadInfoArgs>& aOptionalLoadInfoArgs,
+    const nsACString& aOriginRemoteType, nsINode* aCspToInheritLoadingContext,
+    mozilla::net::LoadInfo** outLoadInfo);
+
+/**
+ * Fills ParentLoadInfoForwarderArgs with properties we want to carry to child
+ * processes.
+ */
+void LoadInfoToParentLoadInfoForwarder(
+    nsILoadInfo* aLoadInfo,
+    mozilla::net::ParentLoadInfoForwarderArgs* aForwarderArgsOut);
+
+/**
+ * Merges (replaces) properties of an existing LoadInfo on a child process
+ * with properties carried down through ParentLoadInfoForwarderArgs.
+ */
+nsresult MergeParentLoadInfoForwarder(
+    mozilla::net::ParentLoadInfoForwarderArgs const& aForwarderArgs,
+    nsILoadInfo* aLoadInfo);
+
+/**
+ * Fills ChildLoadInfoForwarderArgs with properties we want to carry to the
+ * parent process after the initial channel creation.
+ */
+void LoadInfoToChildLoadInfoForwarder(
+    nsILoadInfo* aLoadInfo,
+    mozilla::net::ChildLoadInfoForwarderArgs* aForwarderArgsOut);
+
+/**
+ * Merges (replaces) properties of an existing LoadInfo on the parent process
+ * with properties contained in a ChildLoadInfoForwarderArgs.
+ */
+nsresult MergeChildLoadInfoForwarder(
+    const mozilla::net::ChildLoadInfoForwarderArgs& aForwardArgs,
+    nsILoadInfo* aLoadInfo);
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_backgroundutils_h__
diff --git a/ipc/glue/BigBuffer.cpp b/ipc/glue/BigBuffer.cpp
new file mode 100644
index 0000000000..822ffe20fe
--- /dev/null
+++ b/ipc/glue/BigBuffer.cpp
@@ -0,0 +1,105 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/BigBuffer.h"
+
+#include "mozilla/ipc/SharedMemoryBasic.h"
+#include "nsDebug.h"
+
+namespace mozilla::ipc {
+
+BigBuffer::BigBuffer(Adopt, SharedMemory* aSharedMemory, size_t aSize)
+    : mSize(aSize), mData(AsVariant(RefPtr{aSharedMemory})) {
+  MOZ_RELEASE_ASSERT(aSharedMemory && aSharedMemory->memory(),
+                     "shared memory must be non-null and mapped");
+  MOZ_RELEASE_ASSERT(mSize <= aSharedMemory->Size(),
+                     "shared memory region isn't large enough");
+}
+
+BigBuffer::BigBuffer(Adopt, uint8_t* aData, size_t aSize)
+    : mSize(aSize), mData(AsVariant(UniqueFreePtr<uint8_t[]>{aData})) {}
+
+uint8_t* BigBuffer::Data() {
+  return mData.is<0>() ? mData.as<0>().get()
+                       : reinterpret_cast<uint8_t*>(mData.as<1>()->memory());
+}
+const uint8_t* BigBuffer::Data() const {
+  return mData.is<0>()
+             ? mData.as<0>().get()
+             : reinterpret_cast<const uint8_t*>(mData.as<1>()->memory());
+}
+
+auto BigBuffer::TryAllocBuffer(size_t aSize) -> Maybe<Storage> {
+  if (aSize <= kShmemThreshold) {
+    auto mem = UniqueFreePtr<uint8_t[]>{
+        reinterpret_cast<uint8_t*>(malloc(aSize))};  // Fallible!
+    if (!mem) return {};
+    return Some(AsVariant(std::move(mem)));
+  }
+
+  RefPtr<SharedMemory> shmem = new SharedMemoryBasic();
+  size_t capacity = SharedMemory::PageAlignedSize(aSize);
+  if (!shmem->Create(capacity) || !shmem->Map(capacity)) {
+    return {};
+  }
+  return Some(AsVariant(shmem));
+}
+
+}  // namespace mozilla::ipc
+
+void IPC::ParamTraits<mozilla::ipc::BigBuffer>::Write(MessageWriter* aWriter,
+                                                      paramType&& aParam) {
+  using namespace mozilla::ipc;
+  size_t size = std::exchange(aParam.mSize, 0);
+  auto data = std::exchange(aParam.mData, BigBuffer::NoData());
+
+  WriteParam(aWriter, size);
+  bool isShmem = data.is<1>();
+  WriteParam(aWriter, isShmem);
+
+  if (isShmem) {
+    if (!data.as<1>()->WriteHandle(aWriter)) {
+      aWriter->FatalError("Failed to write data shmem");
+    }
+  } else {
+    aWriter->WriteBytes(data.as<0>().get(), size);
+  }
+}
+
+bool IPC::ParamTraits<mozilla::ipc::BigBuffer>::Read(MessageReader* aReader,
+                                                     paramType* aResult) {
+  using namespace mozilla::ipc;
+  size_t size = 0;
+  bool isShmem = false;
+  if (!ReadParam(aReader, &size) || !ReadParam(aReader, &isShmem)) {
+    aReader->FatalError("Failed to read data size and format");
+    return false;
+  }
+
+  if (isShmem) {
+    RefPtr<SharedMemory> shmem = new SharedMemoryBasic();
+    size_t capacity = SharedMemory::PageAlignedSize(size);
+    if (!shmem->ReadHandle(aReader) || !shmem->Map(capacity)) {
+      aReader->FatalError("Failed to read data shmem");
+      return false;
+    }
+    *aResult = BigBuffer(BigBuffer::Adopt{}, shmem, size);
+    return true;
+  }
+
+  mozilla::UniqueFreePtr<uint8_t[]> buf{
+      reinterpret_cast<uint8_t*>(malloc(size))};
+  if (!buf) {
+    aReader->FatalError("Failed to allocate data buffer");
+    return false;
+  }
+  if (!aReader->ReadBytesInto(buf.get(), size)) {
+    aReader->FatalError("Failed to read data");
+    return false;
+  }
+  *aResult = BigBuffer(BigBuffer::Adopt{}, buf.release(), size);
+  return true;
+}
diff --git a/ipc/glue/BigBuffer.h b/ipc/glue/BigBuffer.h
new file mode 100644
index 0000000000..7136b6c03c
--- /dev/null
+++ b/ipc/glue/BigBuffer.h
@@ -0,0 +1,131 @@
+/* -*- 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_ipc_BigBuffer_h
+#define mozilla_ipc_BigBuffer_h
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include "mozilla/Span.h"
+#include "mozilla/Variant.h"
+#include "mozilla/ipc/SharedMemory.h"
+
+namespace mozilla::ipc {
+
+class BigBuffer {
+ public:
+  static constexpr size_t kShmemThreshold = 64 * 1024;
+
+  static BigBuffer TryAlloc(const size_t aSize) {
+    auto ret = BigBuffer{};
+    auto data = TryAllocBuffer(aSize);
+    if (data) {
+      ret.mSize = aSize;
+      ret.mData = std::move(data.ref());
+    }
+    return ret;
+  }
+
+  // Return a new BigBuffer which wraps no data.
+  BigBuffer() : mSize(0), mData(NoData()) {}
+
+  BigBuffer(const BigBuffer&) = delete;
+  BigBuffer& operator=(const BigBuffer&) = delete;
+
+  BigBuffer(BigBuffer&& aOther) noexcept
+      : mSize(std::exchange(aOther.mSize, 0)),
+        mData(std::exchange(aOther.mData, NoData())) {}
+
+  BigBuffer& operator=(BigBuffer&& aOther) noexcept {
+    mSize = std::exchange(aOther.mSize, 0);
+    mData = std::exchange(aOther.mData, NoData());
+    return *this;
+  }
+
+  // Create a new BigBuffer with the given size.
+  // The buffer will be created uninitialized and must be fully initialized
+  // before sending over IPC to avoid leaking uninitialized memory to another
+  // process.
+  explicit BigBuffer(size_t aSize) : mSize(aSize), mData(AllocBuffer(aSize)) {}
+
+  // Create a new BigBuffer containing the data from the provided byte slice.
+  explicit BigBuffer(Span<const uint8_t> aData) : BigBuffer(aData.Length()) {
+    memcpy(Data(), aData.Elements(), aData.Length());
+  }
+
+  // Marker to indicate that a particular constructor of BigBuffer adopts
+  // ownership of the provided data.
+  struct Adopt {};
+
+  // Create a new BigBuffer from an existing shared memory region, taking
+  // ownership of that shared memory region. The shared memory region must be
+  // non-null, mapped, and large enough to fit aSize bytes.
+  BigBuffer(Adopt, SharedMemory* aSharedMemory, size_t aSize);
+
+  // Create a new BigBuffer from an existing memory buffer, taking ownership of
+  // that memory region. The region will be freed using `free()` when it is no
+  // longer needed.
+  BigBuffer(Adopt, uint8_t* aData, size_t aSize);
+
+  ~BigBuffer() = default;
+
+  // Returns a pointer to the data stored by this BigBuffer, regardless of
+  // backing storage type.
+  uint8_t* Data();
+  const uint8_t* Data() const;
+
+  // Returns the size of the data stored by this BigBuffer, regardless of
+  // backing storage type.
+  size_t Size() const { return mSize; }
+
+  // Get a view of the BigBuffer's data as a span.
+  Span<uint8_t> AsSpan() { return Span{Data(), Size()}; }
+  Span<const uint8_t> AsSpan() const { return Span{Data(), Size()}; }
+
+  // If the BigBuffer is backed by shared memory, returns a pointer to the
+  // backing SharedMemory region.
+  SharedMemory* GetSharedMemory() const {
+    return mData.is<1>() ? mData.as<1>().get() : nullptr;
+  }
+
+ private:
+  friend struct IPC::ParamTraits<mozilla::ipc::BigBuffer>;
+
+  using Storage = Variant<UniqueFreePtr<uint8_t[]>, RefPtr<SharedMemory>>;
+
+  // Empty storage which holds no data.
+  static Storage NoData() { return AsVariant(UniqueFreePtr<uint8_t[]>{}); }
+
+  // Fallibly allocate a new storage of the given size.
+  static Maybe<Storage> TryAllocBuffer(size_t aSize);
+
+  // Infallibly allocate a new storage of the given size.
+  static Storage AllocBuffer(size_t aSize) {
+    auto ret = TryAllocBuffer(aSize);
+    if (!ret) {
+      NS_ABORT_OOM(aSize);
+    }
+    return std::move(ret.ref());
+  }
+
+  size_t mSize;
+  Storage mData;
+};
+
+}  // namespace mozilla::ipc
+
+namespace IPC {
+
+template <>
+struct ParamTraits<mozilla::ipc::BigBuffer> {
+  using paramType = mozilla::ipc::BigBuffer;
+  static void Write(MessageWriter* aWriter, paramType&& aParam);
+  static bool Read(MessageReader* aReader, paramType* aResult);
+};
+
+}  // namespace IPC
+
+#endif  // mozilla_BigBuffer_h
diff --git a/ipc/glue/BrowserProcessSubThread.cpp b/ipc/glue/BrowserProcessSubThread.cpp
new file mode 100644
index 0000000000..bd24bf6e3f
--- /dev/null
+++ b/ipc/glue/BrowserProcessSubThread.cpp
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/BrowserProcessSubThread.h"
+#include "mozilla/ipc/NodeController.h"
+
+#if defined(OS_WIN)
+#  include <objbase.h>
+#endif
+
+namespace mozilla {
+namespace ipc {
+
+//
+// BrowserProcessSubThread
+//
+
+// Friendly names for the well-known threads.
+static const char* kBrowserThreadNames[BrowserProcessSubThread::ID_COUNT] = {
+    "IPC I/O Parent",  // IO
+};
+
+/* static */
+StaticMutex BrowserProcessSubThread::sLock;
+BrowserProcessSubThread* BrowserProcessSubThread::sBrowserThreads[ID_COUNT] = {
+    nullptr,  // IO
+};
+
+BrowserProcessSubThread::BrowserProcessSubThread(ID aId)
+    : base::Thread(kBrowserThreadNames[aId]), mIdentifier(aId) {
+  StaticMutexAutoLock lock(sLock);
+  DCHECK(aId >= 0 && aId < ID_COUNT);
+  DCHECK(sBrowserThreads[aId] == nullptr);
+  sBrowserThreads[aId] = this;
+}
+
+BrowserProcessSubThread::~BrowserProcessSubThread() {
+  Stop();
+  {
+    StaticMutexAutoLock lock(sLock);
+    sBrowserThreads[mIdentifier] = nullptr;
+  }
+}
+
+void BrowserProcessSubThread::Init() {
+#if defined(OS_WIN)
+  // Initializes the COM library on the current thread.
+  CoInitialize(nullptr);
+#endif
+
+  // Initialize the ports library in the current thread.
+  if (mIdentifier == IO) {
+    NodeController::InitBrokerProcess();
+  }
+}
+
+void BrowserProcessSubThread::CleanUp() {
+  if (mIdentifier == IO) {
+    NodeController::CleanUp();
+  }
+
+#if defined(OS_WIN)
+  // Closes the COM library on the current thread. CoInitialize must
+  // be balanced by a corresponding call to CoUninitialize.
+  CoUninitialize();
+#endif
+}
+
+// static
+MessageLoop* BrowserProcessSubThread::GetMessageLoop(ID aId) {
+  StaticMutexAutoLock lock(sLock);
+  DCHECK(aId >= 0 && aId < ID_COUNT);
+
+  if (sBrowserThreads[aId]) return sBrowserThreads[aId]->message_loop();
+
+  return nullptr;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/BrowserProcessSubThread.h b/ipc/glue/BrowserProcessSubThread.h
new file mode 100644
index 0000000000..9be8d1ec3d
--- /dev/null
+++ b/ipc/glue/BrowserProcessSubThread.h
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_BrowserProcessSubThread_h
+#define mozilla_ipc_BrowserProcessSubThread_h
+
+#include "base/thread.h"
+#include "mozilla/StaticMutex.h"
+
+#include "nsDebug.h"
+
+namespace mozilla {
+namespace ipc {
+
+// Copied from browser_process_impl.cc, modified slightly.
+class BrowserProcessSubThread : public base::Thread {
+ public:
+  // An enumeration of the well-known threads.
+  enum ID {
+    IO,
+
+    // This identifier does not represent a thread.  Instead it counts
+    // the number of well-known threads.  Insert new well-known
+    // threads before this identifier.
+    ID_COUNT
+  };
+
+  explicit BrowserProcessSubThread(ID aId);
+  ~BrowserProcessSubThread();
+
+  static MessageLoop* GetMessageLoop(ID identifier);
+
+ protected:
+  virtual void Init() override;
+  virtual void CleanUp() override;
+
+ private:
+  // The identifier of this thread.  Only one thread can exist with a given
+  // identifier at a given time.
+  ID mIdentifier;
+
+  // This lock protects |browser_threads_|.  Do not read or modify that array
+  // without holding this lock.  Do not block while holding this lock.
+
+  static StaticMutex sLock;
+
+  // An array of the ChromeThread objects.  This array is protected by |lock_|.
+  // The threads are not owned by this array.  Typically, the threads are owned
+  // on the UI thread by the g_browser_process object.  ChromeThreads remove
+  // themselves from this array upon destruction.
+  static BrowserProcessSubThread* sBrowserThreads[ID_COUNT] MOZ_GUARDED_BY(
+      sLock);
+};
+
+inline void AssertIOThread() {
+  NS_ASSERTION(MessageLoop::TYPE_IO == MessageLoop::current()->type(),
+               "should be on the IO thread!");
+}
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_BrowserProcessSubThread_h
diff --git a/ipc/glue/ByteBuf.h b/ipc/glue/ByteBuf.h
new file mode 100644
index 0000000000..3f3a798b89
--- /dev/null
+++ b/ipc/glue/ByteBuf.h
@@ -0,0 +1,71 @@
+/* -*- 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/. */
+
+/* A type that can be sent without needing to make a copy during
+ * serialization. In addition the receiver can take ownership of the
+ * data to avoid having to make an additional copy. */
+
+#ifndef mozilla_ipc_ByteBuf_h
+#define mozilla_ipc_ByteBuf_h
+
+#include "mozilla/Assertions.h"
+
+namespace IPC {
+template <typename T>
+struct ParamTraits;
+}
+
+namespace mozilla {
+
+namespace ipc {
+
+class ByteBuf final {
+  friend struct IPC::ParamTraits<mozilla::ipc::ByteBuf>;
+
+ public:
+  bool Allocate(size_t aLength) {
+    MOZ_ASSERT(mData == nullptr);
+    mData = (uint8_t*)malloc(aLength);
+    if (!mData) {
+      return false;
+    }
+    mLen = aLength;
+    mCapacity = aLength;
+    return true;
+  }
+
+  ByteBuf() : mData(nullptr), mLen(0), mCapacity(0) {}
+
+  ByteBuf(uint8_t* aData, size_t aLen, size_t aCapacity)
+      : mData(aData), mLen(aLen), mCapacity(aCapacity) {}
+
+  ByteBuf(const ByteBuf& aFrom) = delete;
+
+  ByteBuf(ByteBuf&& aFrom)
+      : mData(aFrom.mData), mLen(aFrom.mLen), mCapacity(aFrom.mCapacity) {
+    aFrom.mData = nullptr;
+    aFrom.mLen = 0;
+    aFrom.mCapacity = 0;
+  }
+
+  ByteBuf& operator=(ByteBuf&& aFrom) {
+    std::swap(mData, aFrom.mData);
+    std::swap(mLen, aFrom.mLen);
+    std::swap(mCapacity, aFrom.mCapacity);
+    return *this;
+  }
+
+  ~ByteBuf() { free(mData); }
+
+  uint8_t* mData;
+  size_t mLen;
+  size_t mCapacity;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_ByteBuf_h
diff --git a/ipc/glue/ByteBufUtils.h b/ipc/glue/ByteBufUtils.h
new file mode 100644
index 0000000000..ba19864214
--- /dev/null
+++ b/ipc/glue/ByteBufUtils.h
@@ -0,0 +1,56 @@
+/* -*- 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/. */
+
+/* A type that can be sent without needing to make a copy during
+ * serialization. In addition the receiver can take ownership of the
+ * data to avoid having to make an additional copy. */
+
+#ifndef mozilla_ipc_ByteBufUtils_h
+#define mozilla_ipc_ByteBufUtils_h
+
+#include "mozilla/ipc/ByteBuf.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/mozalloc_oom.h"
+#include "ipc/IPCMessageUtils.h"
+
+namespace IPC {
+
+template <>
+struct ParamTraits<mozilla::ipc::ByteBuf> {
+  typedef mozilla::ipc::ByteBuf paramType;
+
+  // this is where we transfer the memory from the ByteBuf to IPDL, avoiding a
+  // copy
+  static void Write(MessageWriter* aWriter, paramType&& aParam) {
+    // We need to send the length as a 32-bit value, not a size_t, because on
+    // ARM64 Windows we end up with a 32-bit GMP process sending a ByteBuf to
+    // a 64-bit parent process. WriteBytesZeroCopy takes a uint32_t as an
+    // argument, so it would end up getting truncated anyways. See bug 1757534.
+    mozilla::CheckedInt<uint32_t> length = aParam.mLen;
+    MOZ_RELEASE_ASSERT(length.isValid());
+    WriteParam(aWriter, length.value());
+    // hand over ownership of the buffer to the Message
+    aWriter->WriteBytesZeroCopy(aParam.mData, length.value(), aParam.mCapacity);
+    aParam.mData = nullptr;
+    aParam.mCapacity = 0;
+    aParam.mLen = 0;
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    // We make a copy from the BufferList so that we get a contigous result.
+    uint32_t length;
+    if (!ReadParam(aReader, &length)) return false;
+    if (!aResult->Allocate(length)) {
+      mozalloc_handle_oom(length);
+      return false;
+    }
+    return aReader->ReadBytesInto(aResult->mData, length);
+  }
+};
+
+}  // namespace IPC
+
+#endif  // ifndef mozilla_ipc_ByteBufUtils_h
diff --git a/ipc/glue/CrashReporterClient.cpp b/ipc/glue/CrashReporterClient.cpp
new file mode 100644
index 0000000000..7e0eabe6ca
--- /dev/null
+++ b/ipc/glue/CrashReporterClient.cpp
@@ -0,0 +1,47 @@
+/* -*- 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 "CrashReporterClient.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla {
+namespace ipc {
+
+StaticMutex CrashReporterClient::sLock;
+StaticRefPtr<CrashReporterClient> CrashReporterClient::sClientSingleton;
+
+CrashReporterClient::CrashReporterClient() {
+  MOZ_COUNT_CTOR(CrashReporterClient);
+}
+
+CrashReporterClient::~CrashReporterClient() {
+  MOZ_COUNT_DTOR(CrashReporterClient);
+}
+
+/* static */
+void CrashReporterClient::InitSingleton() {
+  {
+    StaticMutexAutoLock lock(sLock);
+
+    MOZ_ASSERT(!sClientSingleton);
+    sClientSingleton = new CrashReporterClient();
+  }
+}
+
+/* static */
+void CrashReporterClient::DestroySingleton() {
+  StaticMutexAutoLock lock(sLock);
+  sClientSingleton = nullptr;
+}
+
+/* static */
+RefPtr<CrashReporterClient> CrashReporterClient::GetSingleton() {
+  StaticMutexAutoLock lock(sLock);
+  return sClientSingleton;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/CrashReporterClient.h b/ipc/glue/CrashReporterClient.h
new file mode 100644
index 0000000000..26ada18a03
--- /dev/null
+++ b/ipc/glue/CrashReporterClient.h
@@ -0,0 +1,51 @@
+/* -*- 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_ipc_CrashReporterClient_h
+#define mozilla_ipc_CrashReporterClient_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Unused.h"
+#include "nsExceptionHandler.h"
+
+namespace mozilla {
+namespace ipc {
+
+class CrashReporterClient {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(CrashReporterClient);
+
+  // |aTopLevelProtocol| must have a child-to-parent message:
+  //
+  //   async InitCrashReporter(NativeThreadId threadId);
+  template <typename T>
+  static void InitSingleton(T* aToplevelProtocol) {
+    InitSingleton();
+    Unused << aToplevelProtocol->SendInitCrashReporter(
+        CrashReporter::CurrentThreadId());
+  }
+
+  static void InitSingleton();
+
+  static void DestroySingleton();
+  static RefPtr<CrashReporterClient> GetSingleton();
+
+ private:
+  explicit CrashReporterClient();
+  ~CrashReporterClient();
+
+ private:
+  static StaticMutex sLock;
+  static StaticRefPtr<CrashReporterClient> sClientSingleton
+      MOZ_GUARDED_BY(sLock);
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_CrashReporterClient_h
diff --git a/ipc/glue/CrashReporterHelper.h b/ipc/glue/CrashReporterHelper.h
new file mode 100644
index 0000000000..e124643e3e
--- /dev/null
+++ b/ipc/glue/CrashReporterHelper.h
@@ -0,0 +1,78 @@
+/* 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_ipc_CrashReporterHelper_h
+#define mozilla_ipc_CrashReporterHelper_h
+
+#include "CrashReporterHost.h"
+#include "mozilla/UniquePtr.h"
+#include "nsExceptionHandler.h"
+#include "nsICrashService.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla {
+namespace ipc {
+
+/**
+ * This class encapsulates the common elements of crash report handling for
+ * toplevel protocols representing processes. To use this class, you should:
+ *
+ * 1. Declare a method to initialize the crash reporter in your IPDL:
+ *    `async InitCrashReporter(NativeThreadId threadId)`
+ *
+ * 2. Inherit from this class, providing the appropriate `GeckoProcessType`
+ *    enum value for the template parameter PT.
+ *
+ * 3. When your protocol actor is destroyed with a reason of `AbnormalShutdown`,
+ *    you should call `GenerateCrashReport(OtherPid())`. If you need the crash
+ *    report ID it will be copied in the second optional parameter upon
+ *    successful crash report generation.
+ */
+template <GeckoProcessType PT>
+class CrashReporterHelper {
+ public:
+  CrashReporterHelper() : mCrashReporter(nullptr) {}
+  IPCResult RecvInitCrashReporter(const CrashReporter::ThreadId& aThreadId) {
+    mCrashReporter = MakeUnique<ipc::CrashReporterHost>(PT, aThreadId);
+    return IPC_OK();
+  }
+
+ protected:
+  void GenerateCrashReport(base::ProcessId aPid,
+                           nsString* aMinidumpId = nullptr) {
+    nsAutoString minidumpId;
+    if (!mCrashReporter) {
+      HandleOrphanedMinidump(aPid, minidumpId);
+    } else if (mCrashReporter->GenerateCrashReport(aPid)) {
+      minidumpId = mCrashReporter->MinidumpID();
+    }
+
+    if (aMinidumpId) {
+      *aMinidumpId = minidumpId;
+    }
+
+    mCrashReporter = nullptr;
+  }
+
+ private:
+  void HandleOrphanedMinidump(base::ProcessId aPid, nsString& aMinidumpId) {
+    if (CrashReporter::FinalizeOrphanedMinidump(aPid, PT, &aMinidumpId)) {
+      CrashReporterHost::RecordCrash(PT, nsICrashService::CRASH_TYPE_CRASH,
+                                     aMinidumpId);
+    } else {
+      NS_WARNING(nsPrintfCString("child process pid = %" PRIPID
+                                 " crashed without leaving a minidump behind",
+                                 aPid)
+                     .get());
+    }
+  }
+
+ protected:
+  UniquePtr<ipc::CrashReporterHost> mCrashReporter;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_CrashReporterHelper_h
diff --git a/ipc/glue/CrashReporterHost.cpp b/ipc/glue/CrashReporterHost.cpp
new file mode 100644
index 0000000000..d4f0c0f968
--- /dev/null
+++ b/ipc/glue/CrashReporterHost.cpp
@@ -0,0 +1,181 @@
+/* -*- 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 "CrashReporterHost.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/SyncRunnable.h"
+#include "mozilla/Telemetry.h"
+#include "nsServiceManagerUtils.h"
+#include "nsICrashService.h"
+#include "nsXULAppAPI.h"
+#include "nsIFile.h"
+
+namespace mozilla {
+namespace ipc {
+
+CrashReporterHost::CrashReporterHost(GeckoProcessType aProcessType,
+                                     CrashReporter::ThreadId aThreadId)
+    : mProcessType(aProcessType),
+      mThreadId(aThreadId),
+      mStartTime(::time(nullptr)),
+      mFinalized(false) {}
+
+bool CrashReporterHost::GenerateCrashReport(base::ProcessId aPid) {
+  if (!TakeCrashedChildMinidump(aPid, nullptr)) {
+    return false;
+  }
+
+  FinalizeCrashReport();
+  RecordCrash(mProcessType, nsICrashService::CRASH_TYPE_CRASH, mDumpID);
+  return true;
+}
+
+RefPtr<nsIFile> CrashReporterHost::TakeCrashedChildMinidump(
+    base::ProcessId aPid, uint32_t* aOutSequence) {
+  CrashReporter::AnnotationTable annotations;
+  MOZ_ASSERT(!HasMinidump());
+
+  RefPtr<nsIFile> crashDump;
+  if (!CrashReporter::TakeMinidumpForChild(aPid, getter_AddRefs(crashDump),
+                                           annotations, aOutSequence)) {
+    return nullptr;
+  }
+  if (!AdoptMinidump(crashDump, annotations)) {
+    return nullptr;
+  }
+  return crashDump;
+}
+
+bool CrashReporterHost::AdoptMinidump(nsIFile* aFile,
+                                      const AnnotationTable& aAnnotations) {
+  if (!CrashReporter::GetIDFromMinidump(aFile, mDumpID)) {
+    return false;
+  }
+
+  MergeCrashAnnotations(mExtraAnnotations, aAnnotations);
+  return true;
+}
+
+void CrashReporterHost::FinalizeCrashReport() {
+  MOZ_ASSERT(!mFinalized);
+  MOZ_ASSERT(HasMinidump());
+
+  mExtraAnnotations[CrashReporter::Annotation::ProcessType] =
+      XRE_ChildProcessTypeToAnnotation(mProcessType);
+
+  char startTime[32];
+  SprintfLiteral(startTime, "%lld", static_cast<long long>(mStartTime));
+  mExtraAnnotations[CrashReporter::Annotation::StartupTime] =
+      nsDependentCString(startTime);
+
+  CrashReporter::WriteExtraFile(mDumpID, mExtraAnnotations);
+  mFinalized = true;
+}
+
+void CrashReporterHost::DeleteCrashReport() {
+  if (mFinalized && HasMinidump()) {
+    CrashReporter::DeleteMinidumpFilesForID(mDumpID, Some(u"browser"_ns));
+  }
+}
+
+/* static */
+void CrashReporterHost::RecordCrash(GeckoProcessType aProcessType,
+                                    int32_t aCrashType,
+                                    const nsString& aChildDumpID) {
+  if (!NS_IsMainThread()) {
+    RefPtr<Runnable> runnable = NS_NewRunnableFunction(
+        "ipc::CrashReporterHost::RecordCrash", [&]() -> void {
+          CrashReporterHost::RecordCrash(aProcessType, aCrashType,
+                                         aChildDumpID);
+        });
+    RefPtr<nsIThread> mainThread = do_GetMainThread();
+    SyncRunnable::DispatchToThread(mainThread, runnable);
+    return;
+  }
+
+  RecordCrashWithTelemetry(aProcessType, aCrashType);
+  NotifyCrashService(aProcessType, aCrashType, aChildDumpID);
+}
+
+/* static */
+void CrashReporterHost::RecordCrashWithTelemetry(GeckoProcessType aProcessType,
+                                                 int32_t aCrashType) {
+  nsCString key;
+
+  switch (aProcessType) {
+#define GECKO_PROCESS_TYPE(enum_value, enum_name, string_name, proc_typename, \
+                           process_bin_type, procinfo_typename,               \
+                           webidl_typename, allcaps_name)                     \
+  case GeckoProcessType_##enum_name:                                          \
+    key.AssignLiteral(string_name);                                           \
+    break;
+#include "mozilla/GeckoProcessTypes.h"
+#undef GECKO_PROCESS_TYPE
+    // We can't really hit this, thanks to the above switch, but having it
+    // here will placate the compiler.
+    default:
+      MOZ_ASSERT_UNREACHABLE("unknown process type");
+  }
+
+  Telemetry::Accumulate(Telemetry::SUBPROCESS_CRASHES_WITH_DUMP, key, 1);
+}
+
+/* static */
+void CrashReporterHost::NotifyCrashService(GeckoProcessType aProcessType,
+                                           int32_t aCrashType,
+                                           const nsString& aChildDumpID) {
+  MOZ_ASSERT(!aChildDumpID.IsEmpty());
+
+  nsCOMPtr<nsICrashService> crashService =
+      do_GetService("@mozilla.org/crashservice;1");
+  if (!crashService) {
+    return;
+  }
+
+  int32_t processType;
+
+  switch (aProcessType) {
+    case GeckoProcessType_IPDLUnitTest:
+    case GeckoProcessType_Default:
+      NS_ERROR("unknown process type");
+      return;
+    default:
+      processType = (int)aProcessType;
+      break;
+  }
+
+  RefPtr<dom::Promise> promise;
+  crashService->AddCrash(processType, aCrashType, aChildDumpID,
+                         getter_AddRefs(promise));
+}
+
+void CrashReporterHost::AddAnnotation(CrashReporter::Annotation aKey,
+                                      bool aValue) {
+  mExtraAnnotations[aKey] = aValue ? "1"_ns : "0"_ns;
+}
+
+void CrashReporterHost::AddAnnotation(CrashReporter::Annotation aKey,
+                                      int aValue) {
+  nsAutoCString valueString;
+  valueString.AppendInt(aValue);
+  mExtraAnnotations[aKey] = valueString;
+}
+
+void CrashReporterHost::AddAnnotation(CrashReporter::Annotation aKey,
+                                      unsigned int aValue) {
+  nsAutoCString valueString;
+  valueString.AppendInt(aValue);
+  mExtraAnnotations[aKey] = valueString;
+}
+
+void CrashReporterHost::AddAnnotation(CrashReporter::Annotation aKey,
+                                      const nsACString& aValue) {
+  mExtraAnnotations[aKey] = aValue;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/CrashReporterHost.h b/ipc/glue/CrashReporterHost.h
new file mode 100644
index 0000000000..2abf59dce7
--- /dev/null
+++ b/ipc/glue/CrashReporterHost.h
@@ -0,0 +1,125 @@
+/* -*- 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_ipc_CrashReporterHost_h
+#define mozilla_ipc_CrashReporterHost_h
+
+#include <functional>
+
+#include "mozilla/UniquePtr.h"
+#include "base/process.h"
+#include "nsExceptionHandler.h"
+#include "nsThreadUtils.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+
+namespace mozilla {
+namespace ipc {
+
+// This is the newer replacement for CrashReporterParent. It is created in
+// response to a InitCrashReporter message on a top-level actor. When the
+// process terminates abnormally, the top-level should call GenerateCrashReport
+// to automatically integrate metadata.
+class CrashReporterHost {
+  typedef CrashReporter::AnnotationTable AnnotationTable;
+
+ public:
+  CrashReporterHost(GeckoProcessType aProcessType,
+                    CrashReporter::ThreadId aThreadId);
+
+  // Helper function for generating a crash report for a process that probably
+  // crashed (i.e., had an AbnormalShutdown in ActorDestroy). Returns true if
+  // the process has a minidump attached and we were able to generate a report.
+  bool GenerateCrashReport(base::ProcessId aPid);
+
+  // Given an existing minidump for a crashed child process, take ownership of
+  // it from IPDL. After this, FinalizeCrashReport may be called.
+  RefPtr<nsIFile> TakeCrashedChildMinidump(base::ProcessId aPid,
+                                           uint32_t* aOutSequence);
+
+  // Replace the stored minidump with a new one. After this,
+  // FinalizeCrashReport may be called.
+  bool AdoptMinidump(nsIFile* aFile, const AnnotationTable& aAnnotations);
+
+  // If a minidump was already captured (e.g. via the hang reporter), this
+  // finalizes the existing report by attaching metadata, writing out the
+  // .extra file and notifying the crash service.
+  void FinalizeCrashReport();
+
+  // Delete any crash report we might have generated.
+  void DeleteCrashReport();
+
+  // Generate a paired minidump. This does not take the crash report, as
+  // GenerateCrashReport does. After this, FinalizeCrashReport may be called.
+  //
+  // This calls TakeCrashedChildMinidump and FinalizeCrashReport.
+  template <typename Toplevel>
+  bool GenerateMinidumpAndPair(Toplevel* aToplevelProtocol,
+                               const nsACString& aPairName) {
+    ScopedProcessHandle childHandle;
+#ifdef XP_MACOSX
+    childHandle = aToplevelProtocol->Process()->GetChildTask();
+#else
+    if (!base::OpenPrivilegedProcessHandle(aToplevelProtocol->OtherPid(),
+                                           &childHandle.rwget())) {
+      NS_WARNING("Failed to open child process handle.");
+      return false;
+    }
+#endif
+
+    nsCOMPtr<nsIFile> targetDump;
+    if (!CrashReporter::CreateMinidumpsAndPair(childHandle, mThreadId,
+                                               aPairName, mExtraAnnotations,
+                                               getter_AddRefs(targetDump))) {
+      return false;
+    }
+
+    return CrashReporter::GetIDFromMinidump(targetDump, mDumpID);
+  }
+
+  void AddAnnotation(CrashReporter::Annotation aKey, bool aValue);
+  void AddAnnotation(CrashReporter::Annotation aKey, int aValue);
+  void AddAnnotation(CrashReporter::Annotation aKey, unsigned int aValue);
+  void AddAnnotation(CrashReporter::Annotation aKey, const nsACString& aValue);
+
+  bool HasMinidump() const { return !mDumpID.IsEmpty(); }
+  const nsString& MinidumpID() const {
+    MOZ_ASSERT(HasMinidump());
+    return mDumpID;
+  }
+  const nsCString& AdditionalMinidumps() const {
+    return mExtraAnnotations[CrashReporter::Annotation::additional_minidumps];
+  }
+
+  // This is a static helper function to notify the crash service that a
+  // crash has occurred and record the crash with telemetry. This can be called
+  // from any thread, and if not called from the main thread, will post a
+  // synchronous message to the main thread.
+  static void RecordCrash(GeckoProcessType aProcessType, int32_t aCrashType,
+                          const nsString& aChildDumpID);
+
+ private:
+  // Get the nsICrashService crash type to use for an impending crash.
+  int32_t GetCrashType();
+
+  static void RecordCrashWithTelemetry(GeckoProcessType aProcessType,
+                                       int32_t aCrashType);
+  static void NotifyCrashService(GeckoProcessType aProcessType,
+                                 int32_t aCrashType,
+                                 const nsString& aChildDumpID);
+
+ private:
+  GeckoProcessType mProcessType;
+  CrashReporter::ThreadId mThreadId;
+  time_t mStartTime;
+  AnnotationTable mExtraAnnotations;
+  nsString mDumpID;
+  bool mFinalized;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_CrashReporterHost_h
diff --git a/ipc/glue/CrossProcessMutex.h b/ipc/glue/CrossProcessMutex.h
new file mode 100644
index 0000000000..7376fb1b15
--- /dev/null
+++ b/ipc/glue/CrossProcessMutex.h
@@ -0,0 +1,118 @@
+/* -*- 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_CrossProcessMutex_h
+#define mozilla_CrossProcessMutex_h
+
+#include "base/process.h"
+#include "mozilla/Mutex.h"
+
+#if defined(OS_WIN)
+#  include "mozilla/UniquePtrExtensions.h"
+#endif
+#if !defined(OS_WIN) && !defined(OS_NETBSD) && !defined(OS_OPENBSD)
+#  include <pthread.h>
+#  include "mozilla/ipc/SharedMemoryBasic.h"
+#  include "mozilla/Atomics.h"
+#endif
+
+namespace IPC {
+template <typename T>
+struct ParamTraits;
+}  // namespace IPC
+
+//
+// Provides:
+//
+//  - CrossProcessMutex, a non-recursive mutex that can be shared across
+//    processes
+//  - CrossProcessMutexAutoLock, an RAII class for ensuring that Mutexes are
+//    properly locked and unlocked
+//
+// Using CrossProcessMutexAutoLock/CrossProcessMutexAutoUnlock is MUCH
+// preferred to making bare calls to CrossProcessMutex.Lock and Unlock.
+//
+namespace mozilla {
+#if defined(OS_WIN)
+typedef mozilla::UniqueFileHandle CrossProcessMutexHandle;
+#elif !defined(OS_NETBSD) && !defined(OS_OPENBSD)
+typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessMutexHandle;
+#else
+// Stub for other platforms. We can't use uintptr_t here since different
+// processes could disagree on its size.
+typedef uintptr_t CrossProcessMutexHandle;
+#endif
+
+class CrossProcessMutex {
+ public:
+  /**
+   * CrossProcessMutex
+   * @param name A name which can reference this lock (currently unused)
+   **/
+  explicit CrossProcessMutex(const char* aName);
+  /**
+   * CrossProcessMutex
+   * @param handle A handle of an existing cross process mutex that can be
+   *               opened.
+   */
+  explicit CrossProcessMutex(CrossProcessMutexHandle aHandle);
+
+  /**
+   * ~CrossProcessMutex
+   **/
+  ~CrossProcessMutex();
+
+  /**
+   * Lock
+   * This will lock the mutex. Any other thread in any other process that
+   * has access to this mutex calling lock will block execution until the
+   * initial caller of lock has made a call to Unlock.
+   *
+   * If the owning process is terminated unexpectedly the mutex will be
+   * released.
+   **/
+  void Lock();
+
+  /**
+   * Unlock
+   * This will unlock the mutex. A single thread currently waiting on a lock
+   * call will resume execution and aquire ownership of the lock. No
+   * guarantees are made as to the order in which waiting threads will resume
+   * execution.
+   **/
+  void Unlock();
+
+  /**
+   * CloneHandle
+   * This function is called to generate a serializable structure that can
+   * be sent to the specified process and opened on the other side.
+   *
+   * @returns A handle that can be shared to another process
+   */
+  CrossProcessMutexHandle CloneHandle();
+
+ private:
+  friend struct IPC::ParamTraits<CrossProcessMutex>;
+
+  CrossProcessMutex();
+  CrossProcessMutex(const CrossProcessMutex&);
+  CrossProcessMutex& operator=(const CrossProcessMutex&);
+
+#if defined(OS_WIN)
+  HANDLE mMutex;
+#elif !defined(OS_NETBSD) && !defined(OS_OPENBSD)
+  RefPtr<mozilla::ipc::SharedMemoryBasic> mSharedBuffer;
+  pthread_mutex_t* mMutex;
+  mozilla::Atomic<int32_t>* mCount;
+#endif
+};
+
+typedef detail::BaseAutoLock<CrossProcessMutex&> CrossProcessMutexAutoLock;
+typedef detail::BaseAutoUnlock<CrossProcessMutex&> CrossProcessMutexAutoUnlock;
+
+}  // namespace mozilla
+
+#endif
diff --git a/ipc/glue/CrossProcessMutex_posix.cpp b/ipc/glue/CrossProcessMutex_posix.cpp
new file mode 100644
index 0000000000..c37fcb797d
--- /dev/null
+++ b/ipc/glue/CrossProcessMutex_posix.cpp
@@ -0,0 +1,140 @@
+/* -*- 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 "CrossProcessMutex.h"
+#include "mozilla/Unused.h"
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"
+
+namespace {
+
+struct MutexData {
+  pthread_mutex_t mMutex;
+  mozilla::Atomic<int32_t> mCount;
+};
+
+}  // namespace
+
+namespace mozilla {
+
+static void InitMutex(pthread_mutex_t* mMutex) {
+  pthread_mutexattr_t mutexAttributes;
+  pthread_mutexattr_init(&mutexAttributes);
+  // Make the mutex reentrant so it behaves the same as a win32 mutex
+  if (pthread_mutexattr_settype(&mutexAttributes, PTHREAD_MUTEX_RECURSIVE)) {
+    MOZ_CRASH();
+  }
+  if (pthread_mutexattr_setpshared(&mutexAttributes, PTHREAD_PROCESS_SHARED)) {
+    MOZ_CRASH();
+  }
+
+  if (pthread_mutex_init(mMutex, &mutexAttributes)) {
+    MOZ_CRASH();
+  }
+}
+
+CrossProcessMutex::CrossProcessMutex(const char*)
+    : mMutex(nullptr), mCount(nullptr) {
+#if defined(MOZ_SANDBOX)
+  // POSIX mutexes in shared memory aren't guaranteed to be safe - and
+  // they specifically are not on Linux.
+  MOZ_RELEASE_ASSERT(false);
+#endif
+  mSharedBuffer = new ipc::SharedMemoryBasic;
+  if (!mSharedBuffer->Create(sizeof(MutexData))) {
+    MOZ_CRASH();
+  }
+
+  if (!mSharedBuffer->Map(sizeof(MutexData))) {
+    MOZ_CRASH();
+  }
+
+  MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());
+
+  if (!data) {
+    MOZ_CRASH();
+  }
+
+  mMutex = &(data->mMutex);
+  mCount = &(data->mCount);
+
+  *mCount = 1;
+  InitMutex(mMutex);
+
+  MOZ_COUNT_CTOR(CrossProcessMutex);
+}
+
+CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle aHandle)
+    : mMutex(nullptr), mCount(nullptr) {
+  mSharedBuffer = new ipc::SharedMemoryBasic;
+
+  if (!mSharedBuffer->IsHandleValid(aHandle)) {
+    MOZ_CRASH();
+  }
+
+  if (!mSharedBuffer->SetHandle(std::move(aHandle),
+                                ipc::SharedMemory::RightsReadWrite)) {
+    MOZ_CRASH();
+  }
+
+  if (!mSharedBuffer->Map(sizeof(MutexData))) {
+    MOZ_CRASH();
+  }
+
+  MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());
+
+  if (!data) {
+    MOZ_CRASH();
+  }
+
+  mMutex = &(data->mMutex);
+  mCount = &(data->mCount);
+  int32_t count = (*mCount)++;
+
+  if (count == 0) {
+    // The other side has already let go of their CrossProcessMutex, so now
+    // mMutex is garbage. We need to re-initialize it.
+    InitMutex(mMutex);
+  }
+
+  MOZ_COUNT_CTOR(CrossProcessMutex);
+}
+
+CrossProcessMutex::~CrossProcessMutex() {
+  int32_t count = --(*mCount);
+
+  if (count == 0) {
+    // Nothing can be done if the destroy fails so ignore return code.
+    Unused << pthread_mutex_destroy(mMutex);
+  }
+
+  MOZ_COUNT_DTOR(CrossProcessMutex);
+}
+
+void CrossProcessMutex::Lock() {
+  MOZ_ASSERT(*mCount > 0, "Attempting to lock mutex with zero ref count");
+  pthread_mutex_lock(mMutex);
+}
+
+void CrossProcessMutex::Unlock() {
+  MOZ_ASSERT(*mCount > 0, "Attempting to unlock mutex with zero ref count");
+  pthread_mutex_unlock(mMutex);
+}
+
+CrossProcessMutexHandle CrossProcessMutex::CloneHandle() {
+  CrossProcessMutexHandle result = ipc::SharedMemoryBasic::NULLHandle();
+
+  if (mSharedBuffer) {
+    result = mSharedBuffer->CloneHandle();
+    if (!result) {
+      MOZ_CRASH();
+    }
+  }
+
+  return result;
+}
+
+}  // namespace mozilla
diff --git a/ipc/glue/CrossProcessMutex_unimplemented.cpp b/ipc/glue/CrossProcessMutex_unimplemented.cpp
new file mode 100644
index 0000000000..70b63d7ea9
--- /dev/null
+++ b/ipc/glue/CrossProcessMutex_unimplemented.cpp
@@ -0,0 +1,46 @@
+/* -*- 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 "CrossProcessMutex.h"
+
+#include "nsDebug.h"
+
+namespace mozilla {
+
+CrossProcessMutex::CrossProcessMutex(const char*) {
+  MOZ_CRASH("Cross-process mutices not allowed on this platform.");
+}
+
+CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle) {
+  MOZ_CRASH("Cross-process mutices not allowed on this platform.");
+}
+
+CrossProcessMutex::~CrossProcessMutex() {
+  MOZ_CRASH(
+      "Cross-process mutices not allowed on this platform - woah! We should've "
+      "aborted by now!");
+}
+
+void CrossProcessMutex::Lock() {
+  MOZ_CRASH(
+      "Cross-process mutices not allowed on this platform - woah! We should've "
+      "aborted by now!");
+}
+
+void CrossProcessMutex::Unlock() {
+  MOZ_CRASH(
+      "Cross-process mutices not allowed on this platform - woah! We should've "
+      "aborted by now!");
+}
+
+CrossProcessMutexHandle CrossProcessMutex::CloneHandle() {
+  MOZ_CRASH(
+      "Cross-process mutices not allowed on this platform - woah! We should've "
+      "aborted by now!");
+  return 0;
+}
+
+}  // namespace mozilla
diff --git a/ipc/glue/CrossProcessMutex_windows.cpp b/ipc/glue/CrossProcessMutex_windows.cpp
new file mode 100644
index 0000000000..d4bbe2f2ba
--- /dev/null
+++ b/ipc/glue/CrossProcessMutex_windows.cpp
@@ -0,0 +1,65 @@
+/* -*- 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 <windows.h>
+
+#include "base/process_util.h"
+#include "CrossProcessMutex.h"
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"
+#include "ProtocolUtils.h"
+
+using base::GetCurrentProcessHandle;
+using base::ProcessHandle;
+
+namespace mozilla {
+
+CrossProcessMutex::CrossProcessMutex(const char*) {
+  // We explicitly share this using DuplicateHandle, we do -not- want this to
+  // be inherited by child processes by default! So no security attributes are
+  // given.
+  mMutex = ::CreateMutexA(nullptr, FALSE, nullptr);
+  if (!mMutex) {
+    MOZ_CRASH("This shouldn't happen - failed to create mutex!");
+  }
+  MOZ_COUNT_CTOR(CrossProcessMutex);
+}
+
+CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle aHandle) {
+  DWORD flags;
+  if (!::GetHandleInformation(aHandle.get(), &flags)) {
+    MOZ_CRASH("Attempt to construct a mutex from an invalid handle!");
+  }
+  mMutex = aHandle.release();
+  MOZ_COUNT_CTOR(CrossProcessMutex);
+}
+
+CrossProcessMutex::~CrossProcessMutex() {
+  NS_ASSERTION(mMutex, "Improper construction of mutex or double free.");
+  ::CloseHandle(mMutex);
+  MOZ_COUNT_DTOR(CrossProcessMutex);
+}
+
+void CrossProcessMutex::Lock() {
+  NS_ASSERTION(mMutex, "Improper construction of mutex.");
+  ::WaitForSingleObject(mMutex, INFINITE);
+}
+
+void CrossProcessMutex::Unlock() {
+  NS_ASSERTION(mMutex, "Improper construction of mutex.");
+  ::ReleaseMutex(mMutex);
+}
+
+CrossProcessMutexHandle CrossProcessMutex::CloneHandle() {
+  HANDLE newHandle;
+  if (!::DuplicateHandle(GetCurrentProcess(), mMutex, GetCurrentProcess(),
+                         &newHandle, 0, false, DUPLICATE_SAME_ACCESS)) {
+    return nullptr;
+  }
+  return mozilla::UniqueFileHandle(newHandle);
+}
+
+}  // namespace mozilla
diff --git a/ipc/glue/CrossProcessSemaphore.h b/ipc/glue/CrossProcessSemaphore.h
new file mode 100644
index 0000000000..297552853c
--- /dev/null
+++ b/ipc/glue/CrossProcessSemaphore.h
@@ -0,0 +1,118 @@
+/* -*- 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_CrossProcessSemaphore_h
+#define mozilla_CrossProcessSemaphore_h
+
+#include "base/process.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Maybe.h"
+
+#if defined(OS_WIN)
+#  include "mozilla/UniquePtrExtensions.h"
+#endif
+#if !defined(OS_WIN) && !defined(OS_MACOSX)
+#  include <pthread.h>
+#  include <semaphore.h>
+#  include "mozilla/ipc/SharedMemoryBasic.h"
+#  include "mozilla/Atomics.h"
+#endif
+
+namespace IPC {
+template <typename T>
+struct ParamTraits;
+}  // namespace IPC
+
+//
+// Provides:
+//
+//  - CrossProcessSemaphore, a semaphore that can be shared across processes
+namespace mozilla {
+
+template <typename T>
+inline bool IsHandleValid(const T& handle) {
+  return bool(handle);
+}
+
+#if defined(OS_WIN)
+typedef mozilla::UniqueFileHandle CrossProcessSemaphoreHandle;
+#elif !defined(OS_MACOSX)
+typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessSemaphoreHandle;
+
+template <>
+inline bool IsHandleValid<CrossProcessSemaphoreHandle>(
+    const CrossProcessSemaphoreHandle& handle) {
+  return !(handle == mozilla::ipc::SharedMemoryBasic::NULLHandle());
+}
+#else
+// Stub for other platforms. We can't use uintptr_t here since different
+// processes could disagree on its size.
+typedef uintptr_t CrossProcessSemaphoreHandle;
+#endif
+
+class CrossProcessSemaphore {
+ public:
+  /**
+   * CrossProcessSemaphore
+   * @param name A name which can reference this lock (currently unused)
+   **/
+  static CrossProcessSemaphore* Create(const char* aName,
+                                       uint32_t aInitialValue);
+
+  /**
+   * CrossProcessSemaphore
+   * @param handle A handle of an existing cross process semaphore that can be
+   *               opened.
+   */
+  static CrossProcessSemaphore* Create(CrossProcessSemaphoreHandle aHandle);
+
+  ~CrossProcessSemaphore();
+
+  /**
+   * Decrements the current value of the semaphore. This will block if the
+   * current value of the semaphore is 0, up to a maximum of aWaitTime (if
+   * specified).
+   * Returns true if the semaphore was succesfully decremented, false otherwise.
+   **/
+  bool Wait(const Maybe<TimeDuration>& aWaitTime = Nothing());
+
+  /**
+   * Increments the current value of the semaphore.
+   **/
+  void Signal();
+
+  /**
+   * CloneHandle
+   * This function is called to generate a serializable structure that can
+   * be sent to the specified process and opened on the other side.
+   *
+   * @returns A handle that can be shared to another process
+   */
+  CrossProcessSemaphoreHandle CloneHandle();
+
+  void CloseHandle();
+
+ private:
+  friend struct IPC::ParamTraits<CrossProcessSemaphore>;
+
+  CrossProcessSemaphore();
+  CrossProcessSemaphore(const CrossProcessSemaphore&);
+  CrossProcessSemaphore& operator=(const CrossProcessSemaphore&);
+
+#if defined(OS_WIN)
+  explicit CrossProcessSemaphore(HANDLE aSemaphore);
+
+  HANDLE mSemaphore;
+#elif !defined(OS_MACOSX)
+  RefPtr<mozilla::ipc::SharedMemoryBasic> mSharedBuffer;
+  sem_t* mSemaphore;
+  mozilla::Atomic<int32_t>* mRefCount;
+#endif
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/ipc/glue/CrossProcessSemaphore_posix.cpp b/ipc/glue/CrossProcessSemaphore_posix.cpp
new file mode 100644
index 0000000000..d74e9326f9
--- /dev/null
+++ b/ipc/glue/CrossProcessSemaphore_posix.cpp
@@ -0,0 +1,164 @@
+/* -*- 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 "CrossProcessSemaphore.h"
+#include "mozilla/Unused.h"
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"
+#include <errno.h>
+
+static const uint64_t kNsPerMs = 1000000;
+static const uint64_t kNsPerSec = 1000000000;
+
+namespace {
+
+struct SemaphoreData {
+  sem_t mSemaphore;
+  mozilla::Atomic<int32_t> mRefCount;
+  uint32_t mInitialValue;
+};
+
+}  // namespace
+
+namespace mozilla {
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*,
+                                                     uint32_t aInitialValue) {
+  RefPtr<ipc::SharedMemoryBasic> sharedBuffer = new ipc::SharedMemoryBasic;
+  if (!sharedBuffer->Create(sizeof(SemaphoreData))) {
+    return nullptr;
+  }
+
+  if (!sharedBuffer->Map(sizeof(SemaphoreData))) {
+    return nullptr;
+  }
+
+  SemaphoreData* data = static_cast<SemaphoreData*>(sharedBuffer->memory());
+
+  if (!data) {
+    return nullptr;
+  }
+
+  if (sem_init(&data->mSemaphore, 1, aInitialValue)) {
+    return nullptr;
+  }
+
+  CrossProcessSemaphore* sem = new CrossProcessSemaphore;
+  sem->mSharedBuffer = sharedBuffer;
+  sem->mSemaphore = &data->mSemaphore;
+  sem->mRefCount = &data->mRefCount;
+  *sem->mRefCount = 1;
+
+  data->mInitialValue = aInitialValue;
+
+  return sem;
+}
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(
+    CrossProcessSemaphoreHandle aHandle) {
+  RefPtr<ipc::SharedMemoryBasic> sharedBuffer = new ipc::SharedMemoryBasic;
+
+  if (!sharedBuffer->IsHandleValid(aHandle)) {
+    return nullptr;
+  }
+
+  if (!sharedBuffer->SetHandle(std::move(aHandle),
+                               ipc::SharedMemory::RightsReadWrite)) {
+    return nullptr;
+  }
+
+  if (!sharedBuffer->Map(sizeof(SemaphoreData))) {
+    return nullptr;
+  }
+
+  sharedBuffer->CloseHandle();
+
+  SemaphoreData* data = static_cast<SemaphoreData*>(sharedBuffer->memory());
+
+  if (!data) {
+    return nullptr;
+  }
+
+  int32_t oldCount = data->mRefCount++;
+  if (oldCount == 0) {
+    // The other side has already let go of their CrossProcessSemaphore, so now
+    // mSemaphore is garbage. We need to re-initialize it.
+    if (sem_init(&data->mSemaphore, 1, data->mInitialValue)) {
+      data->mRefCount--;
+      return nullptr;
+    }
+  }
+
+  CrossProcessSemaphore* sem = new CrossProcessSemaphore;
+  sem->mSharedBuffer = sharedBuffer;
+  sem->mSemaphore = &data->mSemaphore;
+  sem->mRefCount = &data->mRefCount;
+  return sem;
+}
+
+CrossProcessSemaphore::CrossProcessSemaphore()
+    : mSemaphore(nullptr), mRefCount(nullptr) {
+  MOZ_COUNT_CTOR(CrossProcessSemaphore);
+}
+
+CrossProcessSemaphore::~CrossProcessSemaphore() {
+  int32_t oldCount = --(*mRefCount);
+
+  if (oldCount == 0) {
+    // Nothing can be done if the destroy fails so ignore return code.
+    Unused << sem_destroy(mSemaphore);
+  }
+
+  MOZ_COUNT_DTOR(CrossProcessSemaphore);
+}
+
+bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
+  MOZ_ASSERT(*mRefCount > 0,
+             "Attempting to wait on a semaphore with zero ref count");
+  int ret;
+  if (aWaitTime.isSome()) {
+    struct timespec ts;
+    if (clock_gettime(CLOCK_REALTIME, &ts) == -1) {
+      return false;
+    }
+
+    ts.tv_nsec += (kNsPerMs * aWaitTime->ToMilliseconds());
+    ts.tv_sec += ts.tv_nsec / kNsPerSec;
+    ts.tv_nsec %= kNsPerSec;
+
+    while ((ret = sem_timedwait(mSemaphore, &ts)) == -1 && errno == EINTR) {
+    }
+  } else {
+    while ((ret = sem_wait(mSemaphore)) == -1 && errno == EINTR) {
+    }
+  }
+  return ret == 0;
+}
+
+void CrossProcessSemaphore::Signal() {
+  MOZ_ASSERT(*mRefCount > 0,
+             "Attempting to signal a semaphore with zero ref count");
+  sem_post(mSemaphore);
+}
+
+CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
+  CrossProcessSemaphoreHandle result = ipc::SharedMemoryBasic::NULLHandle();
+
+  if (mSharedBuffer) {
+    result = mSharedBuffer->CloneHandle();
+    if (!result) {
+      MOZ_CRASH();
+    }
+  }
+
+  return result;
+}
+
+void CrossProcessSemaphore::CloseHandle() { mSharedBuffer->CloseHandle(); }
+
+}  // namespace mozilla
diff --git a/ipc/glue/CrossProcessSemaphore_unimplemented.cpp b/ipc/glue/CrossProcessSemaphore_unimplemented.cpp
new file mode 100644
index 0000000000..822aeb76eb
--- /dev/null
+++ b/ipc/glue/CrossProcessSemaphore_unimplemented.cpp
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "CrossProcessSemaphore.h"
+
+#include "nsDebug.h"
+
+namespace mozilla {
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*, uint32_t) {
+  MOZ_CRASH("Cross-process semaphores not allowed on this platform.");
+  return nullptr;
+}
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(
+    CrossProcessSemaphoreHandle) {
+  MOZ_CRASH("Cross-process semaphores not allowed on this platform.");
+  return nullptr;
+}
+
+CrossProcessSemaphore::CrossProcessSemaphore() {
+  MOZ_CRASH(
+      "Cross-process semaphores not allowed on this platform - woah! We "
+      "should've aborted by now!");
+}
+
+CrossProcessSemaphore::~CrossProcessSemaphore() {
+  MOZ_CRASH(
+      "Cross-process semaphores not allowed on this platform - woah! We "
+      "should've aborted by now!");
+}
+
+bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
+  MOZ_CRASH(
+      "Cross-process semaphores not allowed on this platform - woah! We "
+      "should've aborted by now!");
+  return false;
+}
+
+void CrossProcessSemaphore::Signal() {
+  MOZ_CRASH(
+      "Cross-process semaphores not allowed on this platform - woah! We "
+      "should've aborted by now!");
+}
+
+CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
+  MOZ_CRASH(
+      "Cross-process semaphores not allowed on this platform - woah! We "
+      "should've aborted by now!");
+  return 0;
+}
+
+void CrossProcessSemaphore::CloseHandle() {
+  MOZ_CRASH(
+      "Cross-process semaphores not allowed on this platform - woah! We "
+      "should've aborted by now!");
+}
+
+}  // namespace mozilla
diff --git a/ipc/glue/CrossProcessSemaphore_windows.cpp b/ipc/glue/CrossProcessSemaphore_windows.cpp
new file mode 100644
index 0000000000..70644b7d51
--- /dev/null
+++ b/ipc/glue/CrossProcessSemaphore_windows.cpp
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+
+#include "base/process_util.h"
+#include "CrossProcessSemaphore.h"
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"
+#include "ProtocolUtils.h"
+
+using base::GetCurrentProcessHandle;
+using base::ProcessHandle;
+
+namespace mozilla {
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*,
+                                                     uint32_t aInitialValue) {
+  // We explicitly share this using DuplicateHandle, we do -not- want this to
+  // be inherited by child processes by default! So no security attributes are
+  // given.
+  HANDLE semaphore =
+      ::CreateSemaphoreA(nullptr, aInitialValue, 0x7fffffff, nullptr);
+  if (!semaphore) {
+    return nullptr;
+  }
+  return new CrossProcessSemaphore(semaphore);
+}
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(
+    CrossProcessSemaphoreHandle aHandle) {
+  DWORD flags;
+  if (!::GetHandleInformation(aHandle.get(), &flags)) {
+    return nullptr;
+  }
+
+  return new CrossProcessSemaphore(aHandle.release());
+}
+
+CrossProcessSemaphore::CrossProcessSemaphore(HANDLE aSemaphore)
+    : mSemaphore(aSemaphore) {
+  MOZ_COUNT_CTOR(CrossProcessSemaphore);
+}
+
+CrossProcessSemaphore::~CrossProcessSemaphore() {
+  MOZ_ASSERT(mSemaphore, "Improper construction of semaphore or double free.");
+  ::CloseHandle(mSemaphore);
+  MOZ_COUNT_DTOR(CrossProcessSemaphore);
+}
+
+bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
+  MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
+  HRESULT hr = ::WaitForSingleObject(
+      mSemaphore, aWaitTime.isSome() ? aWaitTime->ToMilliseconds() : INFINITE);
+  return hr == WAIT_OBJECT_0;
+}
+
+void CrossProcessSemaphore::Signal() {
+  MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
+  ::ReleaseSemaphore(mSemaphore, 1, nullptr);
+}
+
+CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
+  HANDLE newHandle;
+  bool succeeded =
+      ::DuplicateHandle(GetCurrentProcess(), mSemaphore, GetCurrentProcess(),
+                        &newHandle, 0, false, DUPLICATE_SAME_ACCESS);
+
+  if (!succeeded) {
+    return nullptr;
+  }
+
+  return UniqueFileHandle(newHandle);
+}
+
+void CrossProcessSemaphore::CloseHandle() {}
+
+}  // namespace mozilla
diff --git a/ipc/glue/DataPipe.cpp b/ipc/glue/DataPipe.cpp
new file mode 100644
index 0000000000..55e38ddd67
--- /dev/null
+++ b/ipc/glue/DataPipe.cpp
@@ -0,0 +1,741 @@
+/* -*- 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 "DataPipe.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/ErrorNames.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MoveOnlyFunction.h"
+#include "mozilla/ipc/InputStreamParams.h"
+#include "nsIAsyncInputStream.h"
+#include "nsStreamUtils.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+namespace ipc {
+
+LazyLogModule gDataPipeLog("DataPipe");
+
+namespace data_pipe_detail {
+
+// Helper for queueing up actions to be run once the mutex has been unlocked.
+// Actions will be run in-order.
+class MOZ_SCOPED_CAPABILITY DataPipeAutoLock {
+ public:
+  explicit DataPipeAutoLock(Mutex& aMutex) MOZ_CAPABILITY_ACQUIRE(aMutex)
+      : mMutex(aMutex) {
+    mMutex.Lock();
+  }
+  DataPipeAutoLock(const DataPipeAutoLock&) = delete;
+  DataPipeAutoLock& operator=(const DataPipeAutoLock&) = delete;
+
+  template <typename F>
+  void AddUnlockAction(F aAction) {
+    mActions.AppendElement(std::move(aAction));
+  }
+
+  ~DataPipeAutoLock() MOZ_CAPABILITY_RELEASE() {
+    mMutex.Unlock();
+    for (auto& action : mActions) {
+      action();
+    }
+  }
+
+ private:
+  Mutex& mMutex;
+  AutoTArray<MoveOnlyFunction<void()>, 4> mActions;
+};
+
+static void DoNotifyOnUnlock(DataPipeAutoLock& aLock,
+                             already_AddRefed<nsIRunnable> aCallback,
+                             already_AddRefed<nsIEventTarget> aTarget) {
+  nsCOMPtr<nsIRunnable> callback{std::move(aCallback)};
+  nsCOMPtr<nsIEventTarget> target{std::move(aTarget)};
+  if (callback) {
+    aLock.AddUnlockAction(
+        [callback = std::move(callback), target = std::move(target)]() mutable {
+          if (target) {
+            target->Dispatch(callback.forget());
+          } else {
+            NS_DispatchBackgroundTask(callback.forget());
+          }
+        });
+  }
+}
+
+class DataPipeLink : public NodeController::PortObserver {
+ public:
+  DataPipeLink(bool aReceiverSide, std::shared_ptr<Mutex> aMutex,
+               ScopedPort aPort, SharedMemory* aShmem, uint32_t aCapacity,
+               nsresult aPeerStatus, uint32_t aOffset, uint32_t aAvailable)
+      : mMutex(std::move(aMutex)),
+        mPort(std::move(aPort)),
+        mShmem(aShmem),
+        mCapacity(aCapacity),
+        mReceiverSide(aReceiverSide),
+        mPeerStatus(aPeerStatus),
+        mOffset(aOffset),
+        mAvailable(aAvailable) {}
+
+  void Init() MOZ_EXCLUDES(*mMutex) {
+    {
+      DataPipeAutoLock lock(*mMutex);
+      if (NS_FAILED(mPeerStatus)) {
+        return;
+      }
+      MOZ_ASSERT(mPort.IsValid());
+      mPort.Controller()->SetPortObserver(mPort.Port(), this);
+    }
+    OnPortStatusChanged();
+  }
+
+  void OnPortStatusChanged() final MOZ_EXCLUDES(*mMutex);
+
+  // Add a task to notify the callback after `aLock` is unlocked.
+  //
+  // This method is safe to call multiple times, as after the first time it is
+  // called, `mCallback` will be cleared.
+  void NotifyOnUnlock(DataPipeAutoLock& aLock) MOZ_REQUIRES(*mMutex) {
+    DoNotifyOnUnlock(aLock, mCallback.forget(), mCallbackTarget.forget());
+  }
+
+  void SendBytesConsumedOnUnlock(DataPipeAutoLock& aLock, uint32_t aBytes)
+      MOZ_REQUIRES(*mMutex) {
+    MOZ_LOG(gDataPipeLog, LogLevel::Verbose,
+            ("SendOnUnlock CONSUMED(%u) %s", aBytes, Describe(aLock).get()));
+    if (NS_FAILED(mPeerStatus)) {
+      return;
+    }
+
+    // `mPort` may be destroyed by `SetPeerError` after the DataPipe is unlocked
+    // but before we send the message. The strong controller and port references
+    // will allow us to try to send the message anyway, and it will be safely
+    // dropped if the port has already been closed. CONSUMED messages are safe
+    // to deliver out-of-order, so we don't need to worry about ordering here.
+    aLock.AddUnlockAction([controller = RefPtr{mPort.Controller()},
+                           port = mPort.Port(), aBytes]() mutable {
+      auto message = MakeUnique<IPC::Message>(
+          MSG_ROUTING_NONE, DATA_PIPE_BYTES_CONSUMED_MESSAGE_TYPE);
+      IPC::MessageWriter writer(*message);
+      WriteParam(&writer, aBytes);
+      controller->SendUserMessage(port, std::move(message));
+    });
+  }
+
+  void SetPeerError(DataPipeAutoLock& aLock, nsresult aStatus,
+                    bool aSendClosed = false) MOZ_REQUIRES(*mMutex) {
+    MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+            ("SetPeerError(%s%s) %s", GetStaticErrorName(aStatus),
+             aSendClosed ? ", send" : "", Describe(aLock).get()));
+    // The pipe was closed or errored. Clear the observer reference back
+    // to this type from the port layer, and ensure we notify waiters.
+    MOZ_ASSERT(NS_SUCCEEDED(mPeerStatus));
+    mPeerStatus = NS_SUCCEEDED(aStatus) ? NS_BASE_STREAM_CLOSED : aStatus;
+    aLock.AddUnlockAction([port = std::move(mPort), aStatus, aSendClosed] {
+      if (aSendClosed) {
+        auto message = MakeUnique<IPC::Message>(MSG_ROUTING_NONE,
+                                                DATA_PIPE_CLOSED_MESSAGE_TYPE);
+        IPC::MessageWriter writer(*message);
+        WriteParam(&writer, aStatus);
+        port.Controller()->SendUserMessage(port.Port(), std::move(message));
+      }
+      // The `ScopedPort` being destroyed with this action will close it,
+      // clearing the observer reference from the ports layer.
+    });
+    NotifyOnUnlock(aLock);
+  }
+
+  nsCString Describe(DataPipeAutoLock& aLock) const MOZ_REQUIRES(*mMutex) {
+    return nsPrintfCString(
+        "[%s(%p) c=%u e=%s o=%u a=%u, cb=%s]",
+        mReceiverSide ? "Receiver" : "Sender", this, mCapacity,
+        GetStaticErrorName(mPeerStatus), mOffset, mAvailable,
+        mCallback ? (mCallbackClosureOnly ? "clo" : "yes") : "no");
+  }
+
+  // This mutex is shared with the `DataPipeBase` which owns this
+  // `DataPipeLink`.
+  std::shared_ptr<Mutex> mMutex;
+
+  ScopedPort mPort MOZ_GUARDED_BY(*mMutex);
+  const RefPtr<SharedMemory> mShmem;
+  const uint32_t mCapacity;
+  const bool mReceiverSide;
+
+  bool mProcessingSegment MOZ_GUARDED_BY(*mMutex) = false;
+
+  nsresult mPeerStatus MOZ_GUARDED_BY(*mMutex) = NS_OK;
+  uint32_t mOffset MOZ_GUARDED_BY(*mMutex) = 0;
+  uint32_t mAvailable MOZ_GUARDED_BY(*mMutex) = 0;
+
+  bool mCallbackClosureOnly MOZ_GUARDED_BY(*mMutex) = false;
+  nsCOMPtr<nsIRunnable> mCallback MOZ_GUARDED_BY(*mMutex);
+  nsCOMPtr<nsIEventTarget> mCallbackTarget MOZ_GUARDED_BY(*mMutex);
+};
+
+void DataPipeLink::OnPortStatusChanged() {
+  DataPipeAutoLock lock(*mMutex);
+
+  while (NS_SUCCEEDED(mPeerStatus)) {
+    UniquePtr<IPC::Message> message;
+    if (!mPort.Controller()->GetMessage(mPort.Port(), &message)) {
+      SetPeerError(lock, NS_BASE_STREAM_CLOSED);
+      return;
+    }
+    if (!message) {
+      return;  // no more messages
+    }
+
+    IPC::MessageReader reader(*message);
+    switch (message->type()) {
+      case DATA_PIPE_CLOSED_MESSAGE_TYPE: {
+        nsresult status = NS_OK;
+        if (!ReadParam(&reader, &status)) {
+          NS_WARNING("Unable to parse nsresult error from peer");
+          status = NS_ERROR_UNEXPECTED;
+        }
+        MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+                ("Got CLOSED(%s) %s", GetStaticErrorName(status),
+                 Describe(lock).get()));
+        SetPeerError(lock, status);
+        return;
+      }
+      case DATA_PIPE_BYTES_CONSUMED_MESSAGE_TYPE: {
+        uint32_t consumed = 0;
+        if (!ReadParam(&reader, &consumed)) {
+          NS_WARNING("Unable to parse bytes consumed from peer");
+          SetPeerError(lock, NS_ERROR_UNEXPECTED);
+          return;
+        }
+
+        MOZ_LOG(gDataPipeLog, LogLevel::Verbose,
+                ("Got CONSUMED(%u) %s", consumed, Describe(lock).get()));
+        auto newAvailable = CheckedUint32{mAvailable} + consumed;
+        if (!newAvailable.isValid() || newAvailable.value() > mCapacity) {
+          NS_WARNING("Illegal bytes consumed message received from peer");
+          SetPeerError(lock, NS_ERROR_UNEXPECTED);
+          return;
+        }
+        mAvailable = newAvailable.value();
+        if (!mCallbackClosureOnly) {
+          NotifyOnUnlock(lock);
+        }
+        break;
+      }
+      default: {
+        NS_WARNING("Illegal message type received from peer");
+        SetPeerError(lock, NS_ERROR_UNEXPECTED);
+        return;
+      }
+    }
+  }
+}
+
+DataPipeBase::DataPipeBase(bool aReceiverSide, nsresult aError)
+    : mMutex(std::make_shared<Mutex>(aReceiverSide ? "DataPipeReceiver"
+                                                   : "DataPipeSender")),
+      mStatus(NS_SUCCEEDED(aError) ? NS_BASE_STREAM_CLOSED : aError) {}
+
+DataPipeBase::DataPipeBase(bool aReceiverSide, ScopedPort aPort,
+                           SharedMemory* aShmem, uint32_t aCapacity,
+                           nsresult aPeerStatus, uint32_t aOffset,
+                           uint32_t aAvailable)
+    : mMutex(std::make_shared<Mutex>(aReceiverSide ? "DataPipeReceiver"
+                                                   : "DataPipeSender")),
+      mStatus(NS_OK),
+      mLink(new DataPipeLink(aReceiverSide, mMutex, std::move(aPort), aShmem,
+                             aCapacity, aPeerStatus, aOffset, aAvailable)) {
+  mLink->Init();
+}
+
+DataPipeBase::~DataPipeBase() {
+  DataPipeAutoLock lock(*mMutex);
+  CloseInternal(lock, NS_BASE_STREAM_CLOSED);
+}
+
+void DataPipeBase::CloseInternal(DataPipeAutoLock& aLock, nsresult aStatus) {
+  if (NS_FAILED(mStatus)) {
+    return;
+  }
+
+  MOZ_LOG(
+      gDataPipeLog, LogLevel::Debug,
+      ("Closing(%s) %s", GetStaticErrorName(aStatus), Describe(aLock).get()));
+
+  // Set our status to an errored status.
+  mStatus = NS_SUCCEEDED(aStatus) ? NS_BASE_STREAM_CLOSED : aStatus;
+  RefPtr<DataPipeLink> link = mLink.forget();
+  AssertSameMutex(link->mMutex);
+  link->NotifyOnUnlock(aLock);
+
+  // If our peer hasn't disappeared yet, clean up our connection to it.
+  if (NS_SUCCEEDED(link->mPeerStatus)) {
+    link->SetPeerError(aLock, mStatus, /* aSendClosed */ true);
+  }
+}
+
+nsresult DataPipeBase::ProcessSegmentsInternal(
+    uint32_t aCount, ProcessSegmentFun aProcessSegment,
+    uint32_t* aProcessedCount) {
+  *aProcessedCount = 0;
+
+  while (*aProcessedCount < aCount) {
+    DataPipeAutoLock lock(*mMutex);
+    mMutex->AssertCurrentThreadOwns();
+
+    MOZ_LOG(gDataPipeLog, LogLevel::Verbose,
+            ("ProcessSegments(%u of %u) %s", *aProcessedCount, aCount,
+             Describe(lock).get()));
+
+    nsresult status = CheckStatus(lock);
+    if (NS_FAILED(status)) {
+      if (*aProcessedCount > 0) {
+        return NS_OK;
+      }
+      return status == NS_BASE_STREAM_CLOSED ? NS_OK : status;
+    }
+
+    RefPtr<DataPipeLink> link = mLink;
+    AssertSameMutex(link->mMutex);
+    if (!link->mAvailable) {
+      MOZ_DIAGNOSTIC_ASSERT(NS_SUCCEEDED(link->mPeerStatus),
+                            "CheckStatus will have returned an error");
+      return *aProcessedCount > 0 ? NS_OK : NS_BASE_STREAM_WOULD_BLOCK;
+    }
+
+    MOZ_RELEASE_ASSERT(!link->mProcessingSegment,
+                       "Only one thread may be processing a segment at a time");
+
+    // Extract an iterator over the next contiguous region of the shared memory
+    // buffer which will be used .
+    char* start = static_cast<char*>(link->mShmem->memory()) + link->mOffset;
+    char* iter = start;
+    char* end = start + std::min({aCount - *aProcessedCount, link->mAvailable,
+                                  link->mCapacity - link->mOffset});
+
+    // Record the consumed region from our segment when exiting this scope,
+    // telling our peer how many bytes were consumed. Hold on to `mLink` to keep
+    // the shmem mapped and make sure we can clean up even if we're closed while
+    // processing the shmem region.
+    link->mProcessingSegment = true;
+    auto scopeExit = MakeScopeExit([&] {
+      mMutex->AssertCurrentThreadOwns();  // should still be held
+      AssertSameMutex(link->mMutex);
+
+      MOZ_RELEASE_ASSERT(link->mProcessingSegment);
+      link->mProcessingSegment = false;
+      uint32_t totalProcessed = iter - start;
+      if (totalProcessed > 0) {
+        link->mOffset += totalProcessed;
+        MOZ_RELEASE_ASSERT(link->mOffset <= link->mCapacity);
+        if (link->mOffset == link->mCapacity) {
+          link->mOffset = 0;
+        }
+        link->mAvailable -= totalProcessed;
+        link->SendBytesConsumedOnUnlock(lock, totalProcessed);
+      }
+      MOZ_LOG(gDataPipeLog, LogLevel::Verbose,
+              ("Processed Segment(%u of %zu) %s", totalProcessed, end - start,
+               Describe(lock).get()));
+    });
+
+    {
+      MutexAutoUnlock unlock(*mMutex);
+      while (iter < end) {
+        uint32_t processed = 0;
+        Span segment{iter, end};
+        nsresult rv = aProcessSegment(segment, *aProcessedCount, &processed);
+        if (NS_FAILED(rv) || processed == 0) {
+          return NS_OK;
+        }
+
+        MOZ_RELEASE_ASSERT(processed <= segment.Length());
+        iter += processed;
+        *aProcessedCount += processed;
+      }
+    }
+  }
+  MOZ_DIAGNOSTIC_ASSERT(*aProcessedCount == aCount,
+                        "Must have processed exactly aCount");
+  return NS_OK;
+}
+
+void DataPipeBase::AsyncWaitInternal(already_AddRefed<nsIRunnable> aCallback,
+                                     already_AddRefed<nsIEventTarget> aTarget,
+                                     bool aClosureOnly) {
+  RefPtr<nsIRunnable> callback = std::move(aCallback);
+  RefPtr<nsIEventTarget> target = std::move(aTarget);
+
+  DataPipeAutoLock lock(*mMutex);
+  MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+          ("AsyncWait %s %p %s", aClosureOnly ? "(closure)" : "(ready)",
+           callback.get(), Describe(lock).get()));
+
+  if (NS_FAILED(CheckStatus(lock))) {
+#ifdef DEBUG
+    if (mLink) {
+      AssertSameMutex(mLink->mMutex);
+      MOZ_ASSERT(!mLink->mCallback);
+    }
+#endif
+    DoNotifyOnUnlock(lock, callback.forget(), target.forget());
+    return;
+  }
+
+  AssertSameMutex(mLink->mMutex);
+
+  // NOTE: After this point, `mLink` may have previously had a callback which is
+  // now being cancelled, make sure we clear `mCallback` even if we're going to
+  // call `aCallback` immediately.
+  mLink->mCallback = callback.forget();
+  mLink->mCallbackTarget = target.forget();
+  mLink->mCallbackClosureOnly = aClosureOnly;
+  if (!aClosureOnly && mLink->mAvailable) {
+    mLink->NotifyOnUnlock(lock);
+  }
+}
+
+nsresult DataPipeBase::CheckStatus(DataPipeAutoLock& aLock) {
+  // If our peer has closed or errored, we may need to close our local side to
+  // reflect the error code our peer provided. If we're a sender, we want to
+  // become closed immediately, whereas if we're a receiver we want to wait
+  // until our available buffer has been exhausted.
+  //
+  // NOTE: There may still be 2-stage writes/reads ongoing at this point, which
+  // will continue due to `mLink` being kept alive by the
+  // `ProcessSegmentsInternal` function.
+  if (NS_FAILED(mStatus)) {
+    return mStatus;
+  }
+  AssertSameMutex(mLink->mMutex);
+  if (NS_FAILED(mLink->mPeerStatus) &&
+      (!mLink->mReceiverSide || !mLink->mAvailable)) {
+    CloseInternal(aLock, mLink->mPeerStatus);
+  }
+  return mStatus;
+}
+
+nsCString DataPipeBase::Describe(DataPipeAutoLock& aLock) {
+  if (mLink) {
+    AssertSameMutex(mLink->mMutex);
+    return mLink->Describe(aLock);
+  }
+  return nsPrintfCString("[status=%s]", GetStaticErrorName(mStatus));
+}
+
+template <typename T>
+void DataPipeWrite(IPC::MessageWriter* aWriter, T* aParam) {
+  DataPipeAutoLock lock(*aParam->mMutex);
+  MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+          ("IPC Write: %s", aParam->Describe(lock).get()));
+
+  WriteParam(aWriter, aParam->mStatus);
+  if (NS_FAILED(aParam->mStatus)) {
+    return;
+  }
+
+  aParam->AssertSameMutex(aParam->mLink->mMutex);
+  MOZ_RELEASE_ASSERT(!aParam->mLink->mProcessingSegment,
+                     "cannot transfer while processing a segment");
+
+  // Serialize relevant parameters to our peer.
+  WriteParam(aWriter, std::move(aParam->mLink->mPort));
+  if (!aParam->mLink->mShmem->WriteHandle(aWriter)) {
+    aWriter->FatalError("failed to write DataPipe shmem handle");
+    MOZ_CRASH("failed to write DataPipe shmem handle");
+  }
+  WriteParam(aWriter, aParam->mLink->mCapacity);
+  WriteParam(aWriter, aParam->mLink->mPeerStatus);
+  WriteParam(aWriter, aParam->mLink->mOffset);
+  WriteParam(aWriter, aParam->mLink->mAvailable);
+
+  // Mark our peer as closed so we don't try to send to it when closing.
+  aParam->mLink->mPeerStatus = NS_ERROR_NOT_INITIALIZED;
+  aParam->CloseInternal(lock, NS_ERROR_NOT_INITIALIZED);
+}
+
+template <typename T>
+bool DataPipeRead(IPC::MessageReader* aReader, RefPtr<T>* aResult) {
+  nsresult rv = NS_OK;
+  if (!ReadParam(aReader, &rv)) {
+    aReader->FatalError("failed to read DataPipe status");
+    return false;
+  }
+  if (NS_FAILED(rv)) {
+    *aResult = new T(rv);
+    MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+            ("IPC Read: [status=%s]", GetStaticErrorName(rv)));
+    return true;
+  }
+
+  ScopedPort port;
+  if (!ReadParam(aReader, &port)) {
+    aReader->FatalError("failed to read DataPipe port");
+    return false;
+  }
+  RefPtr shmem = new SharedMemoryBasic();
+  if (!shmem->ReadHandle(aReader)) {
+    aReader->FatalError("failed to read DataPipe shmem");
+    return false;
+  }
+  uint32_t capacity = 0;
+  nsresult peerStatus = NS_OK;
+  uint32_t offset = 0;
+  uint32_t available = 0;
+  if (!ReadParam(aReader, &capacity) || !ReadParam(aReader, &peerStatus) ||
+      !ReadParam(aReader, &offset) || !ReadParam(aReader, &available)) {
+    aReader->FatalError("failed to read DataPipe fields");
+    return false;
+  }
+  if (!capacity || offset >= capacity || available > capacity) {
+    aReader->FatalError("received DataPipe state values are inconsistent");
+    return false;
+  }
+  if (!shmem->Map(SharedMemory::PageAlignedSize(capacity))) {
+    aReader->FatalError("failed to map DataPipe shared memory region");
+    return false;
+  }
+
+  *aResult =
+      new T(std::move(port), shmem, capacity, peerStatus, offset, available);
+  if (MOZ_LOG_TEST(gDataPipeLog, LogLevel::Debug)) {
+    DataPipeAutoLock lock(*(*aResult)->mMutex);
+    MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+            ("IPC Read: %s", (*aResult)->Describe(lock).get()));
+  }
+  return true;
+}
+
+}  // namespace data_pipe_detail
+
+//-----------------------------------------------------------------------------
+// DataPipeSender
+//-----------------------------------------------------------------------------
+
+NS_IMPL_ISUPPORTS(DataPipeSender, nsIOutputStream, nsIAsyncOutputStream,
+                  DataPipeSender)
+
+// nsIOutputStream
+
+NS_IMETHODIMP DataPipeSender::Close() {
+  return CloseWithStatus(NS_BASE_STREAM_CLOSED);
+}
+
+NS_IMETHODIMP DataPipeSender::Flush() { return NS_OK; }
+
+NS_IMETHODIMP DataPipeSender::StreamStatus() {
+  data_pipe_detail::DataPipeAutoLock lock(*mMutex);
+  return CheckStatus(lock);
+}
+
+NS_IMETHODIMP DataPipeSender::Write(const char* aBuf, uint32_t aCount,
+                                    uint32_t* aWriteCount) {
+  return WriteSegments(NS_CopyBufferToSegment, (void*)aBuf, aCount,
+                       aWriteCount);
+}
+
+NS_IMETHODIMP DataPipeSender::WriteFrom(nsIInputStream* aFromStream,
+                                        uint32_t aCount,
+                                        uint32_t* aWriteCount) {
+  return WriteSegments(NS_CopyStreamToSegment, aFromStream, aCount,
+                       aWriteCount);
+}
+
+NS_IMETHODIMP DataPipeSender::WriteSegments(nsReadSegmentFun aReader,
+                                            void* aClosure, uint32_t aCount,
+                                            uint32_t* aWriteCount) {
+  auto processSegment = [&](Span<char> aSpan, uint32_t aToOffset,
+                            uint32_t* aReadCount) -> nsresult {
+    return aReader(this, aClosure, aSpan.data(), aToOffset, aSpan.Length(),
+                   aReadCount);
+  };
+  return ProcessSegmentsInternal(aCount, processSegment, aWriteCount);
+}
+
+NS_IMETHODIMP DataPipeSender::IsNonBlocking(bool* _retval) {
+  *_retval = true;
+  return NS_OK;
+}
+
+// nsIAsyncOutputStream
+
+NS_IMETHODIMP DataPipeSender::CloseWithStatus(nsresult reason) {
+  data_pipe_detail::DataPipeAutoLock lock(*mMutex);
+  CloseInternal(lock, reason);
+  return NS_OK;
+}
+
+NS_IMETHODIMP DataPipeSender::AsyncWait(nsIOutputStreamCallback* aCallback,
+                                        uint32_t aFlags,
+                                        uint32_t aRequestedCount,
+                                        nsIEventTarget* aTarget) {
+  AsyncWaitInternal(
+      aCallback ? NS_NewCancelableRunnableFunction(
+                      "DataPipeReceiver::AsyncWait",
+                      [self = RefPtr{this}, callback = RefPtr{aCallback}] {
+                        MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+                                ("Calling OnOutputStreamReady(%p, %p)",
+                                 callback.get(), self.get()));
+                        callback->OnOutputStreamReady(self);
+                      })
+                : nullptr,
+      do_AddRef(aTarget), aFlags & WAIT_CLOSURE_ONLY);
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// DataPipeReceiver
+//-----------------------------------------------------------------------------
+
+NS_IMPL_ISUPPORTS(DataPipeReceiver, nsIInputStream, nsIAsyncInputStream,
+                  nsIIPCSerializableInputStream, DataPipeReceiver)
+
+// nsIInputStream
+
+NS_IMETHODIMP DataPipeReceiver::Close() {
+  return CloseWithStatus(NS_BASE_STREAM_CLOSED);
+}
+
+NS_IMETHODIMP DataPipeReceiver::Available(uint64_t* _retval) {
+  data_pipe_detail::DataPipeAutoLock lock(*mMutex);
+  nsresult rv = CheckStatus(lock);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  AssertSameMutex(mLink->mMutex);
+  *_retval = mLink->mAvailable;
+  return NS_OK;
+}
+
+NS_IMETHODIMP DataPipeReceiver::StreamStatus() {
+  data_pipe_detail::DataPipeAutoLock lock(*mMutex);
+  return CheckStatus(lock);
+}
+
+NS_IMETHODIMP DataPipeReceiver::Read(char* aBuf, uint32_t aCount,
+                                     uint32_t* aReadCount) {
+  return ReadSegments(NS_CopySegmentToBuffer, aBuf, aCount, aReadCount);
+}
+
+NS_IMETHODIMP DataPipeReceiver::ReadSegments(nsWriteSegmentFun aWriter,
+                                             void* aClosure, uint32_t aCount,
+                                             uint32_t* aReadCount) {
+  auto processSegment = [&](Span<char> aSpan, uint32_t aToOffset,
+                            uint32_t* aWriteCount) -> nsresult {
+    return aWriter(this, aClosure, aSpan.data(), aToOffset, aSpan.Length(),
+                   aWriteCount);
+  };
+  return ProcessSegmentsInternal(aCount, processSegment, aReadCount);
+}
+
+NS_IMETHODIMP DataPipeReceiver::IsNonBlocking(bool* _retval) {
+  *_retval = true;
+  return NS_OK;
+}
+
+// nsIAsyncInputStream
+
+NS_IMETHODIMP DataPipeReceiver::CloseWithStatus(nsresult aStatus) {
+  data_pipe_detail::DataPipeAutoLock lock(*mMutex);
+  CloseInternal(lock, aStatus);
+  return NS_OK;
+}
+
+NS_IMETHODIMP DataPipeReceiver::AsyncWait(nsIInputStreamCallback* aCallback,
+                                          uint32_t aFlags,
+                                          uint32_t aRequestedCount,
+                                          nsIEventTarget* aTarget) {
+  AsyncWaitInternal(
+      aCallback ? NS_NewCancelableRunnableFunction(
+                      "DataPipeReceiver::AsyncWait",
+                      [self = RefPtr{this}, callback = RefPtr{aCallback}] {
+                        MOZ_LOG(gDataPipeLog, LogLevel::Debug,
+                                ("Calling OnInputStreamReady(%p, %p)",
+                                 callback.get(), self.get()));
+                        callback->OnInputStreamReady(self);
+                      })
+                : nullptr,
+      do_AddRef(aTarget), aFlags & WAIT_CLOSURE_ONLY);
+  return NS_OK;
+}
+
+// nsIIPCSerializableInputStream
+
+void DataPipeReceiver::SerializedComplexity(uint32_t aMaxSize,
+                                            uint32_t* aSizeUsed,
+                                            uint32_t* aPipes,
+                                            uint32_t* aTransferables) {
+  // We report DataPipeReceiver as taking one transferrable to serialize, rather
+  // than one pipe, as we aren't starting a new pipe for this purpose, and are
+  // instead transferring an existing pipe.
+  *aTransferables = 1;
+}
+
+void DataPipeReceiver::Serialize(InputStreamParams& aParams, uint32_t aMaxSize,
+                                 uint32_t* aSizeUsed) {
+  *aSizeUsed = 0;
+  aParams = DataPipeReceiverStreamParams(this);
+}
+
+bool DataPipeReceiver::Deserialize(const InputStreamParams& aParams) {
+  MOZ_CRASH("Handled directly in `DeserializeInputStream`");
+}
+
+//-----------------------------------------------------------------------------
+// NewDataPipe
+//-----------------------------------------------------------------------------
+
+nsresult NewDataPipe(uint32_t aCapacity, DataPipeSender** aSender,
+                     DataPipeReceiver** aReceiver) {
+  if (!aCapacity) {
+    aCapacity = kDefaultDataPipeCapacity;
+  }
+
+  RefPtr<NodeController> controller = NodeController::GetSingleton();
+  if (!controller) {
+    return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+  }
+
+  auto [senderPort, receiverPort] = controller->CreatePortPair();
+  auto shmem = MakeRefPtr<SharedMemoryBasic>();
+  size_t alignedCapacity = SharedMemory::PageAlignedSize(aCapacity);
+  if (!shmem->Create(alignedCapacity) || !shmem->Map(alignedCapacity)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  RefPtr sender = new DataPipeSender(std::move(senderPort), shmem, aCapacity,
+                                     NS_OK, 0, aCapacity);
+  RefPtr receiver = new DataPipeReceiver(std::move(receiverPort), shmem,
+                                         aCapacity, NS_OK, 0, 0);
+  sender.forget(aSender);
+  receiver.forget(aReceiver);
+  return NS_OK;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
+
+void IPC::ParamTraits<mozilla::ipc::DataPipeSender*>::Write(
+    MessageWriter* aWriter, mozilla::ipc::DataPipeSender* aParam) {
+  mozilla::ipc::data_pipe_detail::DataPipeWrite(aWriter, aParam);
+}
+
+bool IPC::ParamTraits<mozilla::ipc::DataPipeSender*>::Read(
+    MessageReader* aReader, RefPtr<mozilla::ipc::DataPipeSender>* aResult) {
+  return mozilla::ipc::data_pipe_detail::DataPipeRead(aReader, aResult);
+}
+
+void IPC::ParamTraits<mozilla::ipc::DataPipeReceiver*>::Write(
+    MessageWriter* aWriter, mozilla::ipc::DataPipeReceiver* aParam) {
+  mozilla::ipc::data_pipe_detail::DataPipeWrite(aWriter, aParam);
+}
+
+bool IPC::ParamTraits<mozilla::ipc::DataPipeReceiver*>::Read(
+    MessageReader* aReader, RefPtr<mozilla::ipc::DataPipeReceiver>* aResult) {
+  return mozilla::ipc::data_pipe_detail::DataPipeRead(aReader, aResult);
+}
diff --git a/ipc/glue/DataPipe.h b/ipc/glue/DataPipe.h
new file mode 100644
index 0000000000..d6439189ad
--- /dev/null
+++ b/ipc/glue/DataPipe.h
@@ -0,0 +1,188 @@
+/* -*- 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 https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_DataPipe_h
+#define mozilla_ipc_DataPipe_h
+
+#include "mozilla/ipc/SharedMemoryBasic.h"
+#include "mozilla/ipc/NodeController.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsIIPCSerializableInputStream.h"
+#include "nsISupports.h"
+
+namespace mozilla {
+namespace ipc {
+
+namespace data_pipe_detail {
+
+class DataPipeAutoLock;
+class DataPipeLink;
+
+class DataPipeBase {
+ public:
+  DataPipeBase(const DataPipeBase&) = delete;
+  DataPipeBase& operator=(const DataPipeBase&) = delete;
+
+ protected:
+  explicit DataPipeBase(bool aReceiverSide, nsresult aError);
+  DataPipeBase(bool aReceiverSide, ScopedPort aPort, SharedMemory* aShmem,
+               uint32_t aCapacity, nsresult aPeerStatus, uint32_t aOffset,
+               uint32_t aAvailable);
+
+  void CloseInternal(DataPipeAutoLock&, nsresult aStatus) MOZ_REQUIRES(*mMutex);
+
+  void AsyncWaitInternal(already_AddRefed<nsIRunnable> aCallback,
+                         already_AddRefed<nsIEventTarget> aTarget,
+                         bool aClosureOnly) MOZ_EXCLUDES(*mMutex);
+
+  // Like `nsWriteSegmentFun` or `nsReadSegmentFun`.
+  using ProcessSegmentFun =
+      FunctionRef<nsresult(Span<char> aSpan, uint32_t aProcessedThisCall,
+                           uint32_t* aProcessedCount)>;
+  nsresult ProcessSegmentsInternal(uint32_t aCount,
+                                   ProcessSegmentFun aProcessSegment,
+                                   uint32_t* aProcessedCount)
+      MOZ_EXCLUDES(*mMutex);
+
+  nsresult CheckStatus(DataPipeAutoLock&) MOZ_REQUIRES(*mMutex);
+
+  nsCString Describe(DataPipeAutoLock&) MOZ_REQUIRES(*mMutex);
+
+  // Thread safety helper to tell the analysis that `mLink->mMutex` is held when
+  // `mMutex` is held.
+  void AssertSameMutex(const std::shared_ptr<Mutex>& aMutex)
+      MOZ_REQUIRES(*mMutex) MOZ_ASSERT_CAPABILITY(*aMutex) {
+    MOZ_ASSERT(mMutex == aMutex);
+  }
+
+  virtual ~DataPipeBase();
+
+  const std::shared_ptr<Mutex> mMutex;
+  nsresult mStatus MOZ_GUARDED_BY(*mMutex) = NS_OK;
+  RefPtr<DataPipeLink> mLink MOZ_GUARDED_BY(*mMutex);
+};
+
+template <typename T>
+void DataPipeWrite(IPC::MessageWriter* aWriter, T* aParam);
+
+template <typename T>
+bool DataPipeRead(IPC::MessageReader* aReader, RefPtr<T>* aResult);
+
+}  // namespace data_pipe_detail
+
+class DataPipeSender;
+class DataPipeReceiver;
+
+#define NS_DATAPIPESENDER_IID                        \
+  {                                                  \
+    0x6698ed77, 0x9fff, 0x425d, {                    \
+      0xb0, 0xa6, 0x1d, 0x30, 0x66, 0xee, 0xb8, 0x16 \
+    }                                                \
+  }
+
+// Helper class for streaming data to another process.
+class DataPipeSender final : public nsIAsyncOutputStream,
+                             public data_pipe_detail::DataPipeBase {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DATAPIPESENDER_IID)
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIOUTPUTSTREAM
+  NS_DECL_NSIASYNCOUTPUTSTREAM
+
+ private:
+  friend nsresult NewDataPipe(uint32_t, DataPipeSender**, DataPipeReceiver**);
+  friend void data_pipe_detail::DataPipeWrite<DataPipeSender>(
+      IPC::MessageWriter* aWriter, DataPipeSender* aParam);
+  friend bool data_pipe_detail::DataPipeRead<DataPipeSender>(
+      IPC::MessageReader* aReader, RefPtr<DataPipeSender>* aResult);
+
+  explicit DataPipeSender(nsresult aError)
+      : data_pipe_detail::DataPipeBase(/* aReceiverSide */ false, aError) {}
+  DataPipeSender(ScopedPort aPort, SharedMemory* aShmem, uint32_t aCapacity,
+                 nsresult aPeerStatus, uint32_t aOffset, uint32_t aAvailable)
+      : data_pipe_detail::DataPipeBase(/* aReceiverSide */ false,
+                                       std::move(aPort), aShmem, aCapacity,
+                                       aPeerStatus, aOffset, aAvailable) {}
+
+  ~DataPipeSender() = default;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(DataPipeSender, NS_DATAPIPESENDER_IID)
+
+#define NS_DATAPIPERECEIVER_IID                      \
+  {                                                  \
+    0x0a185f83, 0x499e, 0x450c, {                    \
+      0x95, 0x82, 0x27, 0x67, 0xad, 0x6d, 0x64, 0xb5 \
+    }                                                \
+  }
+
+// Helper class for streaming data from another process.
+class DataPipeReceiver final : public nsIAsyncInputStream,
+                               public nsIIPCSerializableInputStream,
+                               public data_pipe_detail::DataPipeBase {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DATAPIPERECEIVER_IID)
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIINPUTSTREAM
+  NS_DECL_NSIASYNCINPUTSTREAM
+  NS_DECL_NSIIPCSERIALIZABLEINPUTSTREAM
+
+ private:
+  friend nsresult NewDataPipe(uint32_t, DataPipeSender**, DataPipeReceiver**);
+  friend void data_pipe_detail::DataPipeWrite<DataPipeReceiver>(
+      IPC::MessageWriter* aWriter, DataPipeReceiver* aParam);
+  friend bool data_pipe_detail::DataPipeRead<DataPipeReceiver>(
+      IPC::MessageReader* aReader, RefPtr<DataPipeReceiver>* aResult);
+
+  explicit DataPipeReceiver(nsresult aError)
+      : data_pipe_detail::DataPipeBase(/* aReceiverSide */ true, aError) {}
+  DataPipeReceiver(ScopedPort aPort, SharedMemory* aShmem, uint32_t aCapacity,
+                   nsresult aPeerStatus, uint32_t aOffset, uint32_t aAvailable)
+      : data_pipe_detail::DataPipeBase(/* aReceiverSide */ true,
+                                       std::move(aPort), aShmem, aCapacity,
+                                       aPeerStatus, aOffset, aAvailable) {}
+
+  ~DataPipeReceiver() = default;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(DataPipeReceiver, NS_DATAPIPERECEIVER_IID)
+
+constexpr uint32_t kDefaultDataPipeCapacity = 64 * 1024;
+
+/**
+ * Create a new DataPipe pair. The sender and receiver ends of the pipe may be
+ * used to transfer data between processes. |aCapacity| is the capacity of the
+ * underlying ring buffer. If `0` is passed, `kDefaultDataPipeCapacity` will be
+ * used.
+ */
+nsresult NewDataPipe(uint32_t aCapacity, DataPipeSender** aSender,
+                     DataPipeReceiver** aReceiver);
+
+}  // namespace ipc
+}  // namespace mozilla
+
+namespace IPC {
+
+template <>
+struct ParamTraits<mozilla::ipc::DataPipeSender*> {
+  static void Write(MessageWriter* aWriter,
+                    mozilla::ipc::DataPipeSender* aParam);
+  static bool Read(MessageReader* aReader,
+                   RefPtr<mozilla::ipc::DataPipeSender>* aResult);
+};
+
+template <>
+struct ParamTraits<mozilla::ipc::DataPipeReceiver*> {
+  static void Write(MessageWriter* aWriter,
+                    mozilla::ipc::DataPipeReceiver* aParam);
+  static bool Read(MessageReader* aReader,
+                   RefPtr<mozilla::ipc::DataPipeReceiver>* aResult);
+};
+
+}  // namespace IPC
+
+#endif  // mozilla_ipc_DataPipe_h
diff --git a/ipc/glue/Endpoint.cpp b/ipc/glue/Endpoint.cpp
new file mode 100644
index 0000000000..3391f8b359
--- /dev/null
+++ b/ipc/glue/Endpoint.cpp
@@ -0,0 +1,167 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/Endpoint.h"
+#include "chrome/common/ipc_message.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "nsThreadUtils.h"
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+
+namespace mozilla::ipc {
+
+UntypedManagedEndpoint::UntypedManagedEndpoint(IProtocol* aActor)
+    : mInner(Some(Inner{
+          /* mOtherSide */ aActor->GetWeakLifecycleProxy(),
+          /* mToplevel */ nullptr,
+          aActor->Id(),
+          aActor->GetProtocolId(),
+          aActor->Manager()->Id(),
+          aActor->Manager()->GetProtocolId(),
+      })) {}
+
+UntypedManagedEndpoint::~UntypedManagedEndpoint() {
+  if (!IsValid()) {
+    return;
+  }
+
+  if (mInner->mOtherSide) {
+    // If this ManagedEndpoint was never sent over IPC, deliver a fake
+    // MANAGED_ENDPOINT_DROPPED_MESSAGE_TYPE message directly to the other side
+    // actor.
+    mInner->mOtherSide->ActorEventTarget()->Dispatch(NS_NewRunnableFunction(
+        "~ManagedEndpoint (Local)",
+        [otherSide = mInner->mOtherSide, id = mInner->mId] {
+          if (IProtocol* actor = otherSide->Get(); actor && actor->CanRecv()) {
+            MOZ_DIAGNOSTIC_ASSERT(actor->Id() == id, "Wrong Actor?");
+            RefPtr<ActorLifecycleProxy> strongProxy(actor->GetLifecycleProxy());
+            strongProxy->Get()->OnMessageReceived(
+                IPC::Message(id, MANAGED_ENDPOINT_DROPPED_MESSAGE_TYPE));
+          }
+        }));
+  } else if (mInner->mToplevel) {
+    // If it was sent over IPC, we'll need to send the message to the sending
+    // side. Let's send the message async.
+    mInner->mToplevel->ActorEventTarget()->Dispatch(NS_NewRunnableFunction(
+        "~ManagedEndpoint (Remote)",
+        [toplevel = mInner->mToplevel, id = mInner->mId] {
+          if (IProtocol* actor = toplevel->Get();
+              actor && actor->CanSend() && actor->GetIPCChannel()) {
+            actor->GetIPCChannel()->Send(MakeUnique<IPC::Message>(
+                id, MANAGED_ENDPOINT_DROPPED_MESSAGE_TYPE));
+          }
+        }));
+  }
+}
+
+bool UntypedManagedEndpoint::BindCommon(IProtocol* aActor,
+                                        IProtocol* aManager) {
+  MOZ_ASSERT(aManager);
+  if (!mInner) {
+    NS_WARNING("Cannot bind to invalid endpoint");
+    return false;
+  }
+
+  // Perform thread assertions.
+  if (mInner->mToplevel) {
+    MOZ_DIAGNOSTIC_ASSERT(
+        mInner->mToplevel->ActorEventTarget()->IsOnCurrentThread());
+    MOZ_DIAGNOSTIC_ASSERT(aManager->ToplevelProtocol() ==
+                          mInner->mToplevel->Get());
+  }
+
+  if (NS_WARN_IF(aManager->Id() != mInner->mManagerId) ||
+      NS_WARN_IF(aManager->GetProtocolId() != mInner->mManagerType) ||
+      NS_WARN_IF(aActor->GetProtocolId() != mInner->mType)) {
+    MOZ_ASSERT_UNREACHABLE("Actor and manager do not match Endpoint");
+    return false;
+  }
+
+  if (!aManager->CanSend() || !aManager->GetIPCChannel()) {
+    NS_WARNING("Manager cannot send");
+    return false;
+  }
+
+  int32_t id = mInner->mId;
+  mInner.reset();
+
+  // Our typed caller will insert the actor into the managed container.
+  aActor->SetManagerAndRegister(aManager, id);
+
+  aManager->GetIPCChannel()->Send(
+      MakeUnique<IPC::Message>(id, MANAGED_ENDPOINT_BOUND_MESSAGE_TYPE));
+  return true;
+}
+
+/* static */
+void IPDLParamTraits<UntypedManagedEndpoint>::Write(IPC::MessageWriter* aWriter,
+                                                    IProtocol* aActor,
+                                                    paramType&& aParam) {
+  bool isValid = aParam.mInner.isSome();
+  WriteIPDLParam(aWriter, aActor, isValid);
+  if (!isValid) {
+    return;
+  }
+
+  auto inner = std::move(*aParam.mInner);
+  aParam.mInner.reset();
+
+  MOZ_RELEASE_ASSERT(inner.mOtherSide, "Has not been sent over IPC yet");
+  MOZ_RELEASE_ASSERT(inner.mOtherSide->ActorEventTarget()->IsOnCurrentThread(),
+                     "Must be being sent from the correct thread");
+  MOZ_RELEASE_ASSERT(
+      inner.mOtherSide->Get() && inner.mOtherSide->Get()->ToplevelProtocol() ==
+                                     aActor->ToplevelProtocol(),
+      "Must be being sent over the same toplevel protocol");
+
+  WriteIPDLParam(aWriter, aActor, inner.mId);
+  WriteIPDLParam(aWriter, aActor, inner.mType);
+  WriteIPDLParam(aWriter, aActor, inner.mManagerId);
+  WriteIPDLParam(aWriter, aActor, inner.mManagerType);
+}
+
+/* static */
+bool IPDLParamTraits<UntypedManagedEndpoint>::Read(IPC::MessageReader* aReader,
+                                                   IProtocol* aActor,
+                                                   paramType* aResult) {
+  *aResult = UntypedManagedEndpoint{};
+  bool isValid = false;
+  if (!aActor || !ReadIPDLParam(aReader, aActor, &isValid)) {
+    return false;
+  }
+  if (!isValid) {
+    return true;
+  }
+
+  aResult->mInner.emplace();
+  auto& inner = *aResult->mInner;
+  inner.mToplevel = aActor->ToplevelProtocol()->GetWeakLifecycleProxy();
+  return ReadIPDLParam(aReader, aActor, &inner.mId) &&
+         ReadIPDLParam(aReader, aActor, &inner.mType) &&
+         ReadIPDLParam(aReader, aActor, &inner.mManagerId) &&
+         ReadIPDLParam(aReader, aActor, &inner.mManagerType);
+}
+
+}  // namespace mozilla::ipc
+
+namespace IPC {
+
+void ParamTraits<mozilla::ipc::UntypedEndpoint>::Write(MessageWriter* aWriter,
+                                                       paramType&& aParam) {
+  IPC::WriteParam(aWriter, std::move(aParam.mPort));
+  IPC::WriteParam(aWriter, aParam.mMessageChannelId);
+  IPC::WriteParam(aWriter, aParam.mMyPid);
+  IPC::WriteParam(aWriter, aParam.mOtherPid);
+}
+
+bool ParamTraits<mozilla::ipc::UntypedEndpoint>::Read(MessageReader* aReader,
+                                                      paramType* aResult) {
+  return IPC::ReadParam(aReader, &aResult->mPort) &&
+         IPC::ReadParam(aReader, &aResult->mMessageChannelId) &&
+         IPC::ReadParam(aReader, &aResult->mMyPid) &&
+         IPC::ReadParam(aReader, &aResult->mOtherPid);
+}
+
+}  // namespace IPC
diff --git a/ipc/glue/Endpoint.h b/ipc/glue/Endpoint.h
new file mode 100644
index 0000000000..d7eea94dfc
--- /dev/null
+++ b/ipc/glue/Endpoint.h
@@ -0,0 +1,288 @@
+/* -*- 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 https://mozilla.org/MPL/2.0/. */
+
+#ifndef IPC_GLUE_ENDPOINT_H_
+#define IPC_GLUE_ENDPOINT_H_
+
+#include <utility>
+#include "CrashAnnotations.h"
+#include "base/process.h"
+#include "base/process_util.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/ipc/MessageLink.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/ipc/NodeController.h"
+#include "mozilla/ipc/ScopedPort.h"
+#include "nsXULAppAPI.h"
+#include "nscore.h"
+
+namespace IPC {
+template <class P>
+struct ParamTraits;
+}
+
+namespace mozilla {
+namespace ipc {
+
+namespace endpoint_detail {
+
+template <class T>
+static auto ActorNeedsOtherPidHelper(int)
+    -> decltype(std::declval<T>().OtherPid(), std::true_type{});
+template <class>
+static auto ActorNeedsOtherPidHelper(long) -> std::false_type;
+
+template <typename T>
+constexpr bool ActorNeedsOtherPid =
+    decltype(ActorNeedsOtherPidHelper<T>(0))::value;
+
+}  // namespace endpoint_detail
+
+struct PrivateIPDLInterface {};
+
+class UntypedEndpoint {
+ public:
+  using ProcessId = base::ProcessId;
+
+  UntypedEndpoint() = default;
+
+  UntypedEndpoint(const PrivateIPDLInterface&, ScopedPort aPort,
+                  const nsID& aMessageChannelId,
+                  ProcessId aMyPid = base::kInvalidProcessId,
+                  ProcessId aOtherPid = base::kInvalidProcessId)
+      : mPort(std::move(aPort)),
+        mMessageChannelId(aMessageChannelId),
+        mMyPid(aMyPid),
+        mOtherPid(aOtherPid) {}
+
+  UntypedEndpoint(const UntypedEndpoint&) = delete;
+  UntypedEndpoint(UntypedEndpoint&& aOther) = default;
+
+  UntypedEndpoint& operator=(const UntypedEndpoint&) = delete;
+  UntypedEndpoint& operator=(UntypedEndpoint&& aOther) = default;
+
+  // This method binds aActor to this endpoint. After this call, the actor can
+  // be used to send and receive messages. The endpoint becomes invalid.
+  //
+  // If specified, aEventTarget is the target the actor will be bound to, and
+  // must be on the current thread. Otherwise, GetCurrentSerialEventTarget() is
+  // used.
+  bool Bind(IToplevelProtocol* aActor,
+            nsISerialEventTarget* aEventTarget = nullptr) {
+    MOZ_RELEASE_ASSERT(IsValid());
+    MOZ_RELEASE_ASSERT(mMyPid == base::kInvalidProcessId ||
+                       mMyPid == base::GetCurrentProcId());
+    MOZ_RELEASE_ASSERT(!aEventTarget || aEventTarget->IsOnCurrentThread());
+    return aActor->Open(std::move(mPort), mMessageChannelId, mOtherPid,
+                        aEventTarget);
+  }
+
+  bool IsValid() const { return mPort.IsValid(); }
+
+ protected:
+  friend struct IPC::ParamTraits<UntypedEndpoint>;
+
+  ScopedPort mPort;
+  nsID mMessageChannelId{};
+  ProcessId mMyPid = base::kInvalidProcessId;
+  ProcessId mOtherPid = base::kInvalidProcessId;
+};
+
+/**
+ * An endpoint represents one end of a partially initialized IPDL channel. To
+ * set up a new top-level protocol:
+ *
+ * Endpoint<PFooParent> parentEp;
+ * Endpoint<PFooChild> childEp;
+ * nsresult rv;
+ * rv = PFoo::CreateEndpoints(&parentEp, &childEp);
+ *
+ * Endpoints can be passed in IPDL messages or sent to other threads using
+ * PostTask. Once an Endpoint has arrived at its destination process and thread,
+ * you need to create the top-level actor and bind it to the endpoint:
+ *
+ * FooParent* parent = new FooParent();
+ * bool rv1 = parentEp.Bind(parent, processActor);
+ * bool rv2 = parent->SendBar(...);
+ *
+ * (See Bind below for an explanation of processActor.) Once the actor is bound
+ * to the endpoint, it can send and receive messages.
+ *
+ * If creating endpoints for a [NeedsOtherPid] actor, you're required to also
+ * pass in parentPid and childPid, which are the pids of the processes in which
+ * the parent and child endpoints will be used.
+ */
+template <class PFooSide>
+class Endpoint final : public UntypedEndpoint {
+ public:
+  using UntypedEndpoint::IsValid;
+  using UntypedEndpoint::UntypedEndpoint;
+
+  base::ProcessId OtherPid() const {
+    static_assert(
+        endpoint_detail::ActorNeedsOtherPid<PFooSide>,
+        "OtherPid may only be called on Endpoints for actors which are "
+        "[NeedsOtherPid]");
+    MOZ_RELEASE_ASSERT(mOtherPid != base::kInvalidProcessId);
+    return mOtherPid;
+  }
+
+  // This method binds aActor to this endpoint. After this call, the actor can
+  // be used to send and receive messages. The endpoint becomes invalid.
+  //
+  // If specified, aEventTarget is the target the actor will be bound to, and
+  // must be on the current thread. Otherwise, GetCurrentSerialEventTarget() is
+  // used.
+  bool Bind(PFooSide* aActor, nsISerialEventTarget* aEventTarget = nullptr) {
+    return UntypedEndpoint::Bind(aActor, aEventTarget);
+  }
+};
+
+#if defined(XP_MACOSX)
+void AnnotateCrashReportWithErrno(CrashReporter::Annotation tag, int error);
+#else
+inline void AnnotateCrashReportWithErrno(CrashReporter::Annotation tag,
+                                         int error) {}
+#endif
+
+// This function is used internally to create a pair of Endpoints. See the
+// comment above Endpoint for a description of how it might be used.
+template <class PFooParent, class PFooChild>
+nsresult CreateEndpoints(const PrivateIPDLInterface& aPrivate,
+                         Endpoint<PFooParent>* aParentEndpoint,
+                         Endpoint<PFooChild>* aChildEndpoint) {
+  static_assert(
+      !endpoint_detail::ActorNeedsOtherPid<PFooParent> &&
+          !endpoint_detail::ActorNeedsOtherPid<PFooChild>,
+      "Pids are required when creating endpoints for [NeedsOtherPid] actors");
+
+  auto [parentPort, childPort] =
+      NodeController::GetSingleton()->CreatePortPair();
+  nsID channelId = nsID::GenerateUUID();
+  *aParentEndpoint =
+      Endpoint<PFooParent>(aPrivate, std::move(parentPort), channelId);
+  *aChildEndpoint =
+      Endpoint<PFooChild>(aPrivate, std::move(childPort), channelId);
+  return NS_OK;
+}
+
+template <class PFooParent, class PFooChild>
+nsresult CreateEndpoints(const PrivateIPDLInterface& aPrivate,
+                         base::ProcessId aParentDestPid,
+                         base::ProcessId aChildDestPid,
+                         Endpoint<PFooParent>* aParentEndpoint,
+                         Endpoint<PFooChild>* aChildEndpoint) {
+  MOZ_RELEASE_ASSERT(aParentDestPid != base::kInvalidProcessId);
+  MOZ_RELEASE_ASSERT(aChildDestPid != base::kInvalidProcessId);
+
+  auto [parentPort, childPort] =
+      NodeController::GetSingleton()->CreatePortPair();
+  nsID channelId = nsID::GenerateUUID();
+  *aParentEndpoint =
+      Endpoint<PFooParent>(aPrivate, std::move(parentPort), channelId,
+                           aParentDestPid, aChildDestPid);
+  *aChildEndpoint = Endpoint<PFooChild>(
+      aPrivate, std::move(childPort), channelId, aChildDestPid, aParentDestPid);
+  return NS_OK;
+}
+
+class UntypedManagedEndpoint {
+ public:
+  bool IsValid() const { return mInner.isSome(); }
+
+  UntypedManagedEndpoint(const UntypedManagedEndpoint&) = delete;
+  UntypedManagedEndpoint& operator=(const UntypedManagedEndpoint&) = delete;
+
+ protected:
+  UntypedManagedEndpoint() = default;
+  explicit UntypedManagedEndpoint(IProtocol* aActor);
+
+  UntypedManagedEndpoint(UntypedManagedEndpoint&& aOther) noexcept
+      : mInner(std::move(aOther.mInner)) {
+    aOther.mInner = Nothing();
+  }
+  UntypedManagedEndpoint& operator=(UntypedManagedEndpoint&& aOther) noexcept {
+    this->~UntypedManagedEndpoint();
+    new (this) UntypedManagedEndpoint(std::move(aOther));
+    return *this;
+  }
+
+  ~UntypedManagedEndpoint() noexcept;
+
+  bool BindCommon(IProtocol* aActor, IProtocol* aManager);
+
+ private:
+  friend struct IPDLParamTraits<UntypedManagedEndpoint>;
+
+  struct Inner {
+    // Pointers to the toplevel actor which will manage this connection. When
+    // created, only `mOtherSide` will be set, and will reference the
+    // toplevel actor which the other side is managed by. After being sent over
+    // IPC, only `mToplevel` will be set, and will be the toplevel actor for the
+    // channel which received the IPC message.
+    RefPtr<WeakActorLifecycleProxy> mOtherSide;
+    RefPtr<WeakActorLifecycleProxy> mToplevel;
+
+    int32_t mId = 0;
+    ProtocolId mType = LastMsgIndex;
+    int32_t mManagerId = 0;
+    ProtocolId mManagerType = LastMsgIndex;
+  };
+  Maybe<Inner> mInner;
+};
+
+/**
+ * A managed endpoint represents one end of a partially initialized managed
+ * IPDL actor. It is used for situations where the usual IPDL Constructor
+ * methods do not give sufficient control over the construction of actors, such
+ * as when constructing actors within replies, or constructing multiple related
+ * actors simultaneously.
+ *
+ * FooParent* parent = new FooParent();
+ * ManagedEndpoint<PFooChild> childEp = parentMgr->OpenPFooEndpoint(parent);
+ *
+ * ManagedEndpoints should be sent using IPDL messages or other mechanisms to
+ * the other side of the manager channel. Once the ManagedEndpoint has arrived
+ * at its destination, you can create the actor, and bind it to the endpoint.
+ *
+ * FooChild* child = new FooChild();
+ * childMgr->BindPFooEndpoint(childEp, child);
+ *
+ * WARNING: If the remote side of an endpoint has not been bound before it
+ * begins to receive messages, an IPC routing error will occur, likely causing
+ * a browser crash.
+ */
+template <class PFooSide>
+class ManagedEndpoint : public UntypedManagedEndpoint {
+ public:
+  ManagedEndpoint() = default;
+  ManagedEndpoint(ManagedEndpoint&&) noexcept = default;
+  ManagedEndpoint& operator=(ManagedEndpoint&&) noexcept = default;
+
+  ManagedEndpoint(const PrivateIPDLInterface&, IProtocol* aActor)
+      : UntypedManagedEndpoint(aActor) {}
+
+  bool Bind(const PrivateIPDLInterface&, PFooSide* aActor, IProtocol* aManager,
+            ManagedContainer<PFooSide>& aContainer) {
+    if (!BindCommon(aActor, aManager)) {
+      return false;
+    }
+    aContainer.Insert(aActor);
+    return true;
+  }
+
+  // Only invalid ManagedEndpoints can be equal, as valid endpoints are unique.
+  bool operator==(const ManagedEndpoint& _o) const {
+    return !IsValid() && !_o.IsValid();
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // IPC_GLUE_ENDPOINT_H_
diff --git a/ipc/glue/EnumSerializer.h b/ipc/glue/EnumSerializer.h
new file mode 100644
index 0000000000..13c1de3841
--- /dev/null
+++ b/ipc/glue/EnumSerializer.h
@@ -0,0 +1,187 @@
+/* -*- 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 __IPC_GLUE_ENUMSERIALIZER_H__
+#define __IPC_GLUE_ENUMSERIALIZER_H__
+
+#include "CrashAnnotations.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/IntegerTypeTraits.h"
+#include "nsExceptionHandler.h"
+#include "nsLiteralString.h"
+#include "nsString.h"
+#include "nsTLiteralString.h"
+
+class PickleIterator;
+
+namespace IPC {
+class Message;
+class MessageReader;
+class MessageWriter;
+}  // namespace IPC
+
+#ifdef _MSC_VER
+#  pragma warning(disable : 4800)
+#endif
+
+namespace IPC {
+
+/**
+ * Generic enum serializer.
+ *
+ * Consider using the specializations below, such as ContiguousEnumSerializer.
+ *
+ * This is a generic serializer for any enum type used in IPDL.
+ * Programmers can define ParamTraits<E> for enum type E by deriving
+ * EnumSerializer<E, MyEnumValidator> where MyEnumValidator is a struct
+ * that has to define a static IsLegalValue function returning whether
+ * a given value is a legal value of the enum type at hand.
+ *
+ * \sa https://developer.mozilla.org/en/IPDL/Type_Serialization
+ */
+template <typename E, typename EnumValidator>
+struct EnumSerializer {
+  typedef E paramType;
+
+  // XXX(Bug 1690343) Should this be changed to
+  // std::make_unsigned_t<std::underlying_type_t<paramType>>, to make this more
+  // consistent with the type used for validating values?
+  typedef typename mozilla::UnsignedStdintTypeForSize<sizeof(paramType)>::Type
+      uintParamType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aValue) {
+    // XXX This assertion is somewhat meaningless at least for E that don't have
+    // a fixed underlying type: if aValue weren't a legal value, we would
+    // already have UB where this function is called.
+    MOZ_RELEASE_ASSERT(EnumValidator::IsLegalValue(
+        static_cast<std::underlying_type_t<paramType>>(aValue)));
+    WriteParam(aWriter, uintParamType(aValue));
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uintParamType value;
+    if (!ReadParam(aReader, &value)) {
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::IPCReadErrorReason, "Bad iter"_ns);
+      return false;
+    } else if (!EnumValidator::IsLegalValue(value)) {
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::IPCReadErrorReason, "Illegal value"_ns);
+      return false;
+    }
+    *aResult = paramType(value);
+    return true;
+  }
+};
+
+template <typename E, E MinLegal, E HighBound>
+class ContiguousEnumValidator {
+  // Silence overzealous -Wtype-limits bug in GCC fixed in GCC 4.8:
+  // "comparison of unsigned expression >= 0 is always true"
+  // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11856
+  template <typename T>
+  static bool IsLessThanOrEqual(T a, T b) {
+    return a <= b;
+  }
+
+ public:
+  using IntegralType = std::underlying_type_t<E>;
+  static constexpr auto kMinLegalIntegral = static_cast<IntegralType>(MinLegal);
+  static constexpr auto kHighBoundIntegral =
+      static_cast<IntegralType>(HighBound);
+
+  static bool IsLegalValue(const IntegralType e) {
+    return IsLessThanOrEqual(kMinLegalIntegral, e) && e < kHighBoundIntegral;
+  }
+};
+
+template <typename E, E MinLegal, E MaxLegal>
+class ContiguousEnumValidatorInclusive {
+  // Silence overzealous -Wtype-limits bug in GCC fixed in GCC 4.8:
+  // "comparison of unsigned expression >= 0 is always true"
+  // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11856
+  template <typename T>
+  static bool IsLessThanOrEqual(T a, T b) {
+    return a <= b;
+  }
+
+ public:
+  using IntegralType = std::underlying_type_t<E>;
+  static constexpr auto kMinLegalIntegral = static_cast<IntegralType>(MinLegal);
+  static constexpr auto kMaxLegalIntegral = static_cast<IntegralType>(MaxLegal);
+
+  static bool IsLegalValue(const IntegralType e) {
+    return IsLessThanOrEqual(kMinLegalIntegral, e) && e <= kMaxLegalIntegral;
+  }
+};
+
+template <typename E, E AllBits>
+struct BitFlagsEnumValidator {
+  static bool IsLegalValue(const std::underlying_type_t<E> e) {
+    return (e & static_cast<std::underlying_type_t<E>>(AllBits)) == e;
+  }
+};
+
+/**
+ * Specialization of EnumSerializer for enums with contiguous enum values.
+ *
+ * Provide two values: MinLegal, HighBound. An enum value x will be
+ * considered legal if MinLegal <= x < HighBound.
+ *
+ * For example, following is definition of serializer for enum type FOO.
+ * \code
+ * enum FOO { FOO_FIRST, FOO_SECOND, FOO_LAST, NUM_FOO };
+ *
+ * template <>
+ * struct ParamTraits<FOO>:
+ *     public ContiguousEnumSerializer<FOO, FOO_FIRST, NUM_FOO> {};
+ * \endcode
+ * FOO_FIRST, FOO_SECOND, and FOO_LAST are valid value.
+ */
+template <typename E, E MinLegal, E HighBound>
+struct ContiguousEnumSerializer
+    : EnumSerializer<E, ContiguousEnumValidator<E, MinLegal, HighBound>> {};
+
+/**
+ * This is similar to ContiguousEnumSerializer, but the last template
+ * parameter is expected to be the highest legal value, rather than a
+ * sentinel value. This is intended to support enumerations that don't
+ * have sentinel values.
+ */
+template <typename E, E MinLegal, E MaxLegal>
+struct ContiguousEnumSerializerInclusive
+    : EnumSerializer<E,
+                     ContiguousEnumValidatorInclusive<E, MinLegal, MaxLegal>> {
+};
+
+/**
+ * Specialization of EnumSerializer for enums representing bit flags.
+ *
+ * Provide one value: AllBits. An enum value x will be
+ * considered legal if (x & AllBits) == x;
+ *
+ * Example:
+ * \code
+ * enum FOO {
+ *   FOO_FIRST =  1 << 0,
+ *   FOO_SECOND = 1 << 1,
+ *   FOO_LAST =   1 << 2,
+ *   ALL_BITS =   (1 << 3) - 1
+ * };
+ *
+ * template <>
+ * struct ParamTraits<FOO>:
+ *     public BitFlagsEnumSerializer<FOO, FOO::ALL_BITS> {};
+ * \endcode
+ */
+template <typename E, E AllBits>
+struct BitFlagsEnumSerializer
+    : EnumSerializer<E, BitFlagsEnumValidator<E, AllBits>> {};
+
+} /* namespace IPC */
+
+#endif /* __IPC_GLUE_ENUMSERIALIZER_H__ */
diff --git a/ipc/glue/EnvironmentMap.h b/ipc/glue/EnvironmentMap.h
new file mode 100644
index 0000000000..5cd0ef8c58
--- /dev/null
+++ b/ipc/glue/EnvironmentMap.h
@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SANDBOXING_COMMON_ENVIRONMENTMAP_H_
+#define SANDBOXING_COMMON_ENVIRONMENTMAP_H_
+
+#include <map>
+#include <memory>
+#include <string>
+
+namespace base {
+
+#if defined(OS_WIN)
+
+typedef std::wstring NativeEnvironmentString;
+typedef std::map<NativeEnvironmentString, NativeEnvironmentString>
+    EnvironmentMap;
+
+#  define ENVIRONMENT_LITERAL(x) L##x
+#  define ENVIRONMENT_STRING(x) \
+    ((std::wstring)(NS_ConvertUTF8toUTF16((x)).get()))
+
+// Returns a modified environment vector constructed from the given environment
+// and the list of changes given in |changes|. Each key in the environment is
+// matched against the first element of the pairs. In the event of a match, the
+// value is replaced by the second of the pair, unless the second is empty, in
+// which case the key-value is removed.
+//
+// This Windows version takes and returns a Windows-style environment block
+// which is a concatenated list of null-terminated 16-bit strings. The end is
+// marked by a double-null terminator. The size of the returned string will
+// include the terminators.
+NativeEnvironmentString AlterEnvironment(const wchar_t* env,
+                                         const EnvironmentMap& changes);
+
+#elif defined(OS_POSIX)
+
+typedef std::string NativeEnvironmentString;
+typedef std::map<NativeEnvironmentString, NativeEnvironmentString>
+    EnvironmentMap;
+
+#  define ENVIRONMENT_LITERAL(x) x
+#  define ENVIRONMENT_STRING(x) x
+
+// See general comments for the Windows version above.
+//
+// This Posix version takes and returns a Posix-style environment block, which
+// is a null-terminated list of pointers to null-terminated strings. The
+// returned array will have appended to it the storage for the array itself so
+// there is only one pointer to manage, but this means that you can't copy the
+// array without keeping the original around.
+std::unique_ptr<char*[]> AlterEnvironment(const char* const* env,
+                                          const EnvironmentMap& changes);
+
+#endif
+
+}  // namespace base
+
+#endif  // SANDBOXING_COMMON_ENVIRONMENTMAP_H_
diff --git a/ipc/glue/FileDescriptor.cpp b/ipc/glue/FileDescriptor.cpp
new file mode 100644
index 0000000000..697de4cc63
--- /dev/null
+++ b/ipc/glue/FileDescriptor.cpp
@@ -0,0 +1,117 @@
+/* -*- 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 "FileDescriptor.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+#include "nsDebug.h"
+
+#ifdef XP_WIN
+#  include <windows.h>
+#  include "ProtocolUtils.h"
+#else  // XP_WIN
+#  include <unistd.h>
+#endif  // XP_WIN
+
+namespace mozilla {
+namespace ipc {
+
+FileDescriptor::FileDescriptor() = default;
+
+FileDescriptor::FileDescriptor(const FileDescriptor& aOther)
+    : mHandle(Clone(aOther.mHandle.get())) {}
+
+FileDescriptor::FileDescriptor(FileDescriptor&& aOther)
+    : mHandle(std::move(aOther.mHandle)) {}
+
+FileDescriptor::FileDescriptor(PlatformHandleType aHandle)
+    : mHandle(Clone(aHandle)) {}
+
+FileDescriptor::FileDescriptor(UniquePlatformHandle&& aHandle)
+    : mHandle(std::move(aHandle)) {}
+
+FileDescriptor::~FileDescriptor() = default;
+
+FileDescriptor& FileDescriptor::operator=(const FileDescriptor& aOther) {
+  if (this != &aOther) {
+    mHandle = Clone(aOther.mHandle.get());
+  }
+  return *this;
+}
+
+FileDescriptor& FileDescriptor::operator=(FileDescriptor&& aOther) {
+  if (this != &aOther) {
+    mHandle = std::move(aOther.mHandle);
+  }
+  return *this;
+}
+
+bool FileDescriptor::IsValid() const { return mHandle != nullptr; }
+
+FileDescriptor::UniquePlatformHandle FileDescriptor::ClonePlatformHandle()
+    const {
+  return Clone(mHandle.get());
+}
+
+FileDescriptor::UniquePlatformHandle FileDescriptor::TakePlatformHandle() {
+  return UniquePlatformHandle(mHandle.release());
+}
+
+bool FileDescriptor::operator==(const FileDescriptor& aOther) const {
+  return mHandle == aOther.mHandle;
+}
+
+// static
+FileDescriptor::UniquePlatformHandle FileDescriptor::Clone(
+    PlatformHandleType aHandle) {
+  FileDescriptor::PlatformHandleType newHandle;
+
+#ifdef XP_WIN
+  if (aHandle == INVALID_HANDLE_VALUE || aHandle == nullptr) {
+    return UniqueFileHandle();
+  }
+  if (::DuplicateHandle(GetCurrentProcess(), aHandle, GetCurrentProcess(),
+                        &newHandle, 0, FALSE, DUPLICATE_SAME_ACCESS)) {
+    return UniqueFileHandle(newHandle);
+  }
+#else  // XP_WIN
+  if (aHandle < 0) {
+    return UniqueFileHandle();
+  }
+  newHandle = dup(aHandle);
+  if (newHandle >= 0) {
+    return UniqueFileHandle(newHandle);
+  }
+#endif
+  NS_WARNING("Failed to duplicate file handle for current process!");
+  return UniqueFileHandle();
+}
+
+void IPDLParamTraits<FileDescriptor>::Write(IPC::MessageWriter* aWriter,
+                                            IProtocol* aActor,
+                                            const FileDescriptor& aParam) {
+  WriteIPDLParam(aWriter, aActor, aParam.ClonePlatformHandle());
+}
+
+bool IPDLParamTraits<FileDescriptor>::Read(IPC::MessageReader* aReader,
+                                           IProtocol* aActor,
+                                           FileDescriptor* aResult) {
+  UniqueFileHandle handle;
+  if (!ReadIPDLParam(aReader, aActor, &handle)) {
+    return false;
+  }
+
+  *aResult = FileDescriptor(std::move(handle));
+  if (!aResult->IsValid()) {
+    printf_stderr("IPDL protocol Error: Received an invalid file descriptor\n");
+  }
+  return true;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/FileDescriptor.h b/ipc/glue/FileDescriptor.h
new file mode 100644
index 0000000000..15160624da
--- /dev/null
+++ b/ipc/glue/FileDescriptor.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_ipc_FileDescriptor_h
+#define mozilla_ipc_FileDescriptor_h
+
+#include "base/basictypes.h"
+#include "base/process.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+namespace mozilla {
+namespace ipc {
+
+// This class is used by IPDL to share file descriptors across processes. When
+// sending a FileDescriptor, IPDL will transfer a duplicate of the handle into
+// the remote process.
+//
+// To use this class add 'FileDescriptor' as an argument in the IPDL protocol
+// and then pass a file descriptor from C++ to the Send method. The Recv method
+// will receive a FileDescriptor& on which PlatformHandle() can be called to
+// return the platform file handle.
+class FileDescriptor {
+ public:
+  typedef base::ProcessId ProcessId;
+
+  using UniquePlatformHandle = mozilla::UniqueFileHandle;
+  using PlatformHandleType = UniquePlatformHandle::ElementType;
+
+  // This should only ever be created by IPDL.
+  struct IPDLPrivate {};
+
+  // Represents an invalid handle.
+  FileDescriptor();
+
+  // Copy constructor will duplicate a new handle.
+  FileDescriptor(const FileDescriptor& aOther);
+
+  FileDescriptor(FileDescriptor&& aOther);
+
+  // This constructor will duplicate a new handle.
+  // The caller still have to close aHandle.
+  explicit FileDescriptor(PlatformHandleType aHandle);
+
+  explicit FileDescriptor(UniquePlatformHandle&& aHandle);
+
+  ~FileDescriptor();
+
+  FileDescriptor& operator=(const FileDescriptor& aOther);
+
+  FileDescriptor& operator=(FileDescriptor&& aOther);
+
+  // Tests mHandle against a well-known invalid platform-specific file handle
+  // (e.g. -1 on POSIX, INVALID_HANDLE_VALUE on Windows).
+  bool IsValid() const;
+
+  // Returns a duplicated handle, it is caller's responsibility to close the
+  // handle.
+  UniquePlatformHandle ClonePlatformHandle() const;
+
+  // Extracts the underlying handle and makes this object an invalid handle.
+  // (Compare UniquePtr::release.)
+  UniquePlatformHandle TakePlatformHandle();
+
+  // Only used in nsTArray.
+  bool operator==(const FileDescriptor& aOther) const;
+
+ private:
+  static UniqueFileHandle Clone(PlatformHandleType aHandle);
+
+  UniquePlatformHandle mHandle;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_FileDescriptor_h
diff --git a/ipc/glue/FileDescriptorShuffle.cpp b/ipc/glue/FileDescriptorShuffle.cpp
new file mode 100644
index 0000000000..7ce89e1b16
--- /dev/null
+++ b/ipc/glue/FileDescriptorShuffle.cpp
@@ -0,0 +1,113 @@
+/* -*- 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 "FileDescriptorShuffle.h"
+
+#include "base/eintr_wrapper.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+
+#include <algorithm>
+#include <unistd.h>
+#include <fcntl.h>
+
+namespace mozilla {
+namespace ipc {
+
+// F_DUPFD_CLOEXEC is like F_DUPFD (see below) but atomically makes
+// the new fd close-on-exec.  This is useful to prevent accidental fd
+// leaks into processes created by plain fork/exec, but IPC uses
+// CloseSuperfluousFds so it's not essential.
+//
+// F_DUPFD_CLOEXEC is in POSIX 2008, but as of 2018 there are still
+// some OSes that don't support it.  (Specifically: Solaris 10 doesn't
+// have it, and Android should have kernel support but doesn't define
+// the constant until API 21 (Lollipop).  We also don't use this for
+// IPC child launching on Android, so there's no point in hard-coding
+// the definitions like we do for Android in some other cases.)
+#ifdef F_DUPFD_CLOEXEC
+static const int kDupFdCmd = F_DUPFD_CLOEXEC;
+#else
+static const int kDupFdCmd = F_DUPFD;
+#endif
+
+// This implementation ensures that the *ranges* of the source and
+// destination fds don't overlap, which is unnecessary but sufficient
+// to avoid conflicts or identity mappings.
+//
+// In practice, the source fds will usually be large and the
+// destination fds will all be relatively small, so there mostly won't
+// be temporary fds.  This approach has the advantage of being simple
+// (and linear-time, but hopefully there aren't enough fds for that to
+// matter).
+bool FileDescriptorShuffle::Init(MappingRef aMapping) {
+  MOZ_ASSERT(mMapping.IsEmpty());
+
+  // Find the maximum destination fd; any source fds not greater than
+  // this will be duplicated.
+  int maxDst = STDERR_FILENO;
+  for (const auto& elem : aMapping) {
+    maxDst = std::max(maxDst, elem.second);
+  }
+  mMaxDst = maxDst;
+
+#ifdef DEBUG
+  // Increase the limit to make sure the F_DUPFD case gets test coverage.
+  if (!aMapping.IsEmpty()) {
+    // Try to find a value that will create a nontrivial partition.
+    int fd0 = aMapping[0].first;
+    int fdn = aMapping.rbegin()->first;
+    maxDst = std::max(maxDst, (fd0 + fdn) / 2);
+  }
+#endif
+
+  for (const auto& elem : aMapping) {
+    int src = elem.first;
+    // F_DUPFD is like dup() but allows placing a lower bound
+    // on the new fd, which is exactly what we want.
+    if (src <= maxDst) {
+      src = fcntl(src, kDupFdCmd, maxDst + 1);
+      if (src < 0) {
+        return false;
+      }
+      mTempFds.AppendElement(src);
+    }
+    MOZ_ASSERT(src > maxDst);
+#ifdef DEBUG
+    // Check for accidentally mapping two different fds to the same
+    // destination.  (This is O(n^2) time, but it shouldn't matter.)
+    for (const auto& otherElem : mMapping) {
+      MOZ_ASSERT(elem.second != otherElem.second);
+    }
+#endif
+    mMapping.AppendElement(std::make_pair(src, elem.second));
+  }
+  return true;
+}
+
+bool FileDescriptorShuffle::MapsTo(int aFd) const {
+  // Prune fds that are too large to be a destination, rather than
+  // searching; this should be the common case.
+  if (aFd > mMaxDst) {
+    return false;
+  }
+  for (const auto& elem : mMapping) {
+    if (elem.second == aFd) {
+      return true;
+    }
+  }
+  return false;
+}
+
+FileDescriptorShuffle::~FileDescriptorShuffle() {
+  for (const auto& fd : mTempFds) {
+    mozilla::DebugOnly<int> rv = IGNORE_EINTR(close(fd));
+    MOZ_ASSERT(rv == 0);
+  }
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/FileDescriptorShuffle.h b/ipc/glue/FileDescriptorShuffle.h
new file mode 100644
index 0000000000..4afa8e0474
--- /dev/null
+++ b/ipc/glue/FileDescriptorShuffle.h
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_FileDescriptorShuffle_h
+#define mozilla_ipc_FileDescriptorShuffle_h
+
+#include "mozilla/Span.h"
+#include "nsTArray.h"
+
+#include <functional>
+#include <utility>
+
+// This class converts a set of file descriptor mapping, which may
+// contain conflicts (like {a->b, b->c} or {a->b, b->a}) into a
+// sequence of dup2() operations that can be performed between fork
+// and exec, or with posix_spawn_file_actions_adddup2.  It may create
+// temporary duplicates of fds to use as the source of a dup2; they
+// are closed on destruction.
+//
+// The dup2 sequence is guaranteed to not contain dup2(x, x) for any
+// x; if such an element is present in the input, it will be dup2()ed
+// from a temporary fd to ensure that the close-on-exec bit is cleared.
+//
+// In general, this is *not* guaranteed to minimize the use of
+// temporary fds.
+
+namespace mozilla {
+namespace ipc {
+
+class FileDescriptorShuffle {
+ public:
+  FileDescriptorShuffle() = default;
+  ~FileDescriptorShuffle();
+
+  using MappingRef = mozilla::Span<const std::pair<int, int>>;
+
+  // Translate the given mapping, creating temporary fds as needed.
+  // Can fail (return false) on failure to duplicate fds.
+  bool Init(MappingRef aMapping);
+
+  // Accessor for the dup2() sequence.  Do not use the returned value
+  // or the fds contained in it after this object is destroyed.
+  MappingRef Dup2Sequence() const { return mMapping; }
+
+  // Tests whether the given fd is used as a destination in this mapping.
+  // Can be used to close other fds after performing the dup2()s.
+  bool MapsTo(int aFd) const;
+
+  // Forget the information, so that it's destructor will not try to
+  // delete FDs duped by itself.
+  void Forget() { mTempFds.Clear(); }
+
+ private:
+  nsTArray<std::pair<int, int>> mMapping;
+  nsTArray<int> mTempFds;
+  int mMaxDst;
+
+  FileDescriptorShuffle(const FileDescriptorShuffle&) = delete;
+  void operator=(const FileDescriptorShuffle&) = delete;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_FileDescriptorShuffle_h
diff --git a/ipc/glue/FileDescriptorUtils.cpp b/ipc/glue/FileDescriptorUtils.cpp
new file mode 100644
index 0000000000..e4af78e79e
--- /dev/null
+++ b/ipc/glue/FileDescriptorUtils.cpp
@@ -0,0 +1,109 @@
+/* -*- 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 "FileDescriptorUtils.h"
+
+#include "nsIEventTarget.h"
+
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsNetCID.h"
+#include "nsServiceManagerUtils.h"
+#include "prio.h"
+#include "private/pprio.h"
+
+#include <errno.h>
+#ifdef XP_WIN
+#  include <io.h>
+#else
+#  include <unistd.h>
+#endif
+
+using mozilla::ipc::CloseFileRunnable;
+
+CloseFileRunnable::CloseFileRunnable(const FileDescriptor& aFileDescriptor)
+    : Runnable("CloseFileRunnable"), mFileDescriptor(aFileDescriptor) {
+  MOZ_ASSERT(aFileDescriptor.IsValid());
+}
+
+CloseFileRunnable::~CloseFileRunnable() {
+  if (mFileDescriptor.IsValid()) {
+    // It's probably safer to take the main thread IO hit here rather than leak
+    // the file descriptor.
+    CloseFile();
+  }
+}
+
+NS_IMPL_ISUPPORTS_INHERITED0(CloseFileRunnable, Runnable)
+
+void CloseFileRunnable::Dispatch() {
+  nsCOMPtr<nsIEventTarget> eventTarget =
+      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+  NS_ENSURE_TRUE_VOID(eventTarget);
+
+  nsresult rv = eventTarget->Dispatch(this, NS_DISPATCH_NORMAL);
+  NS_ENSURE_SUCCESS_VOID(rv);
+}
+
+void CloseFileRunnable::CloseFile() {
+  // It's possible for this to happen on the main thread if the dispatch to the
+  // stream service fails so we can't assert the thread on which we're running.
+  mFileDescriptor = FileDescriptor();
+}
+
+NS_IMETHODIMP
+CloseFileRunnable::Run() {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  CloseFile();
+  return NS_OK;
+}
+
+namespace mozilla {
+namespace ipc {
+
+FILE* FileDescriptorToFILE(const FileDescriptor& aDesc, const char* aOpenMode) {
+  if (!aDesc.IsValid()) {
+    errno = EBADF;
+    return nullptr;
+  }
+  auto handle = aDesc.ClonePlatformHandle();
+#ifdef XP_WIN
+  int fd = _open_osfhandle(static_cast<intptr_t>(handle.get()), 0);
+  if (fd == -1) {
+    return nullptr;
+  }
+  Unused << handle.release();
+#else
+  int fd = handle.release();
+#endif
+  FILE* file = fdopen(fd, aOpenMode);
+  if (!file) {
+    int saved_errno = errno;
+    close(fd);
+    errno = saved_errno;
+  }
+  return file;
+}
+
+FileDescriptor FILEToFileDescriptor(FILE* aStream) {
+  if (!aStream) {
+    errno = EBADF;
+    return FileDescriptor();
+  }
+#ifdef XP_WIN
+  int fd = _fileno(aStream);
+  if (fd == -1) {
+    return FileDescriptor();
+  }
+  return FileDescriptor(reinterpret_cast<HANDLE>(_get_osfhandle(fd)));
+#else
+  return FileDescriptor(fileno(aStream));
+#endif
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/FileDescriptorUtils.h b/ipc/glue/FileDescriptorUtils.h
new file mode 100644
index 0000000000..e8aab0639e
--- /dev/null
+++ b/ipc/glue/FileDescriptorUtils.h
@@ -0,0 +1,53 @@
+/* -*- 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_ipc_FileDescriptorUtils_h
+#define mozilla_ipc_FileDescriptorUtils_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/ipc/FileDescriptor.h"
+#include "nsThreadUtils.h"
+#include <stdio.h>
+
+namespace mozilla {
+namespace ipc {
+
+// When Dispatch() is called (from main thread) this class arranges to close the
+// provided FileDescriptor on one of the socket transport service threads (to
+// avoid main thread I/O).
+class CloseFileRunnable final : public Runnable {
+  typedef mozilla::ipc::FileDescriptor FileDescriptor;
+
+  FileDescriptor mFileDescriptor;
+
+ public:
+  explicit CloseFileRunnable(const FileDescriptor& aFileDescriptor);
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIRUNNABLE
+
+  void Dispatch();
+
+ private:
+  ~CloseFileRunnable();
+
+  void CloseFile();
+};
+
+// On failure, FileDescriptorToFILE returns nullptr; on success,
+// returns duplicated FILE*.
+// This is meant for use with FileDescriptors received over IPC.
+FILE* FileDescriptorToFILE(const FileDescriptor& aDesc, const char* aOpenMode);
+
+// FILEToFileDescriptor does not consume the given FILE*; it must be
+// fclose()d as normal, and this does not invalidate the returned
+// FileDescriptor.
+FileDescriptor FILEToFileDescriptor(FILE* aStream);
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_FileDescriptorUtils_h
diff --git a/ipc/glue/ForkServer.cpp b/ipc/glue/ForkServer.cpp
new file mode 100644
index 0000000000..23ce9362fb
--- /dev/null
+++ b/ipc/glue/ForkServer.cpp
@@ -0,0 +1,298 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 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/ipc/ForkServer.h"
+#include "mozilla/Logging.h"
+#include "chrome/common/chrome_switches.h"
+#include "mozilla/BlockingResourceBase.h"
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+#include "mozilla/ipc/FileDescriptor.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "ipc/IPCMessageUtilsSpecializations.h"
+#include "nsTraceRefcnt.h"
+
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxLaunch.h"
+#endif
+
+#include <algorithm>
+
+namespace mozilla {
+namespace ipc {
+
+LazyLogModule gForkServiceLog("ForkService");
+
+ForkServer::ForkServer() {}
+
+/**
+ * Prepare an environment for running a fork server.
+ */
+void ForkServer::InitProcess(int* aArgc, char*** aArgv) {
+  base::InitForkServerProcess();
+
+  mTcver = MakeUnique<MiniTransceiver>(kClientPipeFd,
+                                       DataBufferClear::AfterReceiving);
+}
+
+/**
+ * Start providing the service at the IPC channel.
+ */
+bool ForkServer::HandleMessages() {
+  while (true) {
+    UniquePtr<IPC::Message> msg;
+    if (!mTcver->Recv(msg)) {
+      break;
+    }
+
+    OnMessageReceived(std::move(msg));
+
+    if (mAppProcBuilder) {
+      // New process - child
+      return false;
+    }
+  }
+  // Stop the server
+  return true;
+}
+
+inline void CleanCString(nsCString& str) {
+  char* data;
+  int sz = str.GetMutableData(&data);
+
+  memset(data, ' ', sz);
+}
+
+inline void CleanString(std::string& str) {
+  const char deadbeef[] =
+      "\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef"
+      "\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef";
+  int pos = 0;
+  size_t sz = str.size();
+  while (sz > 0) {
+    int toclean = std::min(sz, sizeof(deadbeef) - 1);
+    str.replace(pos, toclean, deadbeef);
+    sz -= toclean;
+    pos += toclean;
+  }
+}
+
+inline void PrepareArguments(std::vector<std::string>& aArgv,
+                             nsTArray<nsCString>& aArgvArray) {
+  for (auto& elt : aArgvArray) {
+    aArgv.push_back(elt.get());
+    CleanCString(elt);
+  }
+}
+
+// Prepare aOptions->env_map
+inline void PrepareEnv(base::LaunchOptions* aOptions,
+                       nsTArray<EnvVar>& aEnvMap) {
+  for (auto& elt : aEnvMap) {
+    nsCString& var = std::get<0>(elt);
+    nsCString& val = std::get<1>(elt);
+    aOptions->env_map[var.get()] = val.get();
+    CleanCString(var);
+    CleanCString(val);
+  }
+}
+
+// Prepare aOptions->fds_to_remap
+inline void PrepareFdsRemap(base::LaunchOptions* aOptions,
+                            nsTArray<FdMapping>& aFdsRemap) {
+  MOZ_LOG(gForkServiceLog, LogLevel::Verbose, ("fds mapping:"));
+  for (auto& elt : aFdsRemap) {
+    // FDs are duplicated here.
+    int fd = std::get<0>(elt).ClonePlatformHandle().release();
+    std::pair<int, int> fdmap(fd, std::get<1>(elt));
+    aOptions->fds_to_remap.push_back(fdmap);
+    MOZ_LOG(gForkServiceLog, LogLevel::Verbose,
+            ("\t%d => %d", fdmap.first, fdmap.second));
+  }
+}
+
+template <class P>
+static void ReadParamInfallible(IPC::MessageReader* aReader, P* aResult,
+                                const char* aCrashMessage) {
+  if (!IPC::ReadParam(aReader, aResult)) {
+    MOZ_CRASH_UNSAFE(aCrashMessage);
+  }
+}
+
+/**
+ * Parse a Message to get a list of arguments and fill a LaunchOptions.
+ */
+inline bool ParseForkNewSubprocess(IPC::Message& aMsg,
+                                   std::vector<std::string>& aArgv,
+                                   base::LaunchOptions* aOptions) {
+  if (aMsg.type() != Msg_ForkNewSubprocess__ID) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Verbose,
+            ("unknown message type %d\n", aMsg.type()));
+    return false;
+  }
+
+  IPC::MessageReader reader(aMsg);
+  nsTArray<nsCString> argv_array;
+  nsTArray<EnvVar> env_map;
+  nsTArray<FdMapping> fds_remap;
+
+  ReadParamInfallible(&reader, &argv_array,
+                      "Error deserializing 'nsCString[]'");
+  ReadParamInfallible(&reader, &env_map, "Error deserializing 'EnvVar[]'");
+  ReadParamInfallible(&reader, &fds_remap, "Error deserializing 'FdMapping[]'");
+  reader.EndRead();
+
+  PrepareArguments(aArgv, argv_array);
+  PrepareEnv(aOptions, env_map);
+  PrepareFdsRemap(aOptions, fds_remap);
+
+  return true;
+}
+
+inline void SanitizeBuffers(IPC::Message& aMsg, std::vector<std::string>& aArgv,
+                            base::LaunchOptions& aOptions) {
+  // Clean all buffers in the message to make sure content processes
+  // not peeking others.
+  auto& blist = aMsg.Buffers();
+  for (auto itr = blist.Iter(); !itr.Done();
+       itr.Advance(blist, itr.RemainingInSegment())) {
+    memset(itr.Data(), 0, itr.RemainingInSegment());
+  }
+
+  // clean all data string made from the message.
+  for (auto& var : aOptions.env_map) {
+    // Do it anyway since it is not going to be used anymore.
+    CleanString(*const_cast<std::string*>(&var.first));
+    CleanString(var.second);
+  }
+  for (auto& arg : aArgv) {
+    CleanString(arg);
+  }
+}
+
+/**
+ * Extract parameters from the |Message| to create a
+ * |base::AppProcessBuilder| as |mAppProcBuilder|.
+ *
+ * It will return in both the fork server process and the new content
+ * process.  |mAppProcBuilder| is null for the fork server.
+ */
+void ForkServer::OnMessageReceived(UniquePtr<IPC::Message> message) {
+  std::vector<std::string> argv;
+  base::LaunchOptions options;
+  if (!ParseForkNewSubprocess(*message, argv, &options)) {
+    return;
+  }
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+  mozilla::SandboxLaunchForkServerPrepare(argv, options);
+#endif
+
+  base::ProcessHandle child_pid = -1;
+  mAppProcBuilder = MakeUnique<base::AppProcessBuilder>();
+  if (!mAppProcBuilder->ForkProcess(argv, options, &child_pid)) {
+    MOZ_CRASH("fail to fork");
+  }
+  MOZ_ASSERT(child_pid >= 0);
+
+  if (child_pid == 0) {
+    // Content process
+    return;
+  }
+
+  // Fork server process
+
+  mAppProcBuilder = nullptr;
+
+  IPC::Message reply(MSG_ROUTING_CONTROL, Reply_ForkNewSubprocess__ID);
+  IPC::MessageWriter writer(reply);
+  WriteIPDLParam(&writer, nullptr, child_pid);
+  mTcver->SendInfallible(reply, "failed to send a reply message");
+
+  // Without this, the content processes that is forked later are
+  // able to read the content of buffers even the buffers have been
+  // released.
+  SanitizeBuffers(*message, argv, options);
+}
+
+/**
+ * Setup and run a fork server at the main thread.
+ *
+ * This function returns for two reasons:
+ *  - the fork server is stopped normally, or
+ *  - a new process is forked from the fork server and this function
+ *    returned in the child, the new process.
+ *
+ * For the later case, aArgc and aArgv are modified to pass the
+ * arguments from the chrome process.
+ */
+bool ForkServer::RunForkServer(int* aArgc, char*** aArgv) {
+#ifdef DEBUG
+  if (getenv("MOZ_FORKSERVER_WAIT_GDB")) {
+    printf(
+        "Waiting for 30 seconds."
+        "  Attach the fork server with gdb %s %d\n",
+        (*aArgv)[0], base::GetCurrentProcId());
+    sleep(30);
+  }
+  bool sleep_newproc = !!getenv("MOZ_FORKSERVER_WAIT_GDB_NEWPROC");
+#endif
+
+  // Do this before NS_LogInit() to avoid log files taking lower
+  // FDs.
+  ForkServer forkserver;
+  forkserver.InitProcess(aArgc, aArgv);
+
+  XRE_SetProcessType("forkserver");
+  NS_LogInit();
+  mozilla::LogModule::Init(0, nullptr);
+  MOZ_LOG(gForkServiceLog, LogLevel::Verbose, ("Start a fork server"));
+  {
+    DebugOnly<base::ProcessHandle> forkserver_pid = base::GetCurrentProcId();
+    if (forkserver.HandleMessages()) {
+      // In the fork server process
+      // The server has stopped.
+      MOZ_LOG(gForkServiceLog, LogLevel::Verbose,
+              ("Terminate the fork server"));
+      NS_LogTerm();
+      return true;
+    }
+    // Now, we are running in a content process just forked from
+    // the fork server process.
+    MOZ_ASSERT(base::GetCurrentProcId() != forkserver_pid);
+    MOZ_LOG(gForkServiceLog, LogLevel::Verbose, ("Fork a new content process"));
+  }
+#ifdef DEBUG
+  if (sleep_newproc) {
+    printf(
+        "Waiting for 30 seconds."
+        "  Attach the new process with gdb %s %d\n",
+        (*aArgv)[0], base::GetCurrentProcId());
+    sleep(30);
+  }
+#endif
+  NS_LogTerm();
+
+  MOZ_ASSERT(forkserver.mAppProcBuilder);
+  // |messageloop| has been destroyed.  So, we can intialized the
+  // process safely.  Message loops may allocates some file
+  // descriptors.  If it is destroyed later, it may mess up this
+  // content process by closing wrong file descriptors.
+  forkserver.mAppProcBuilder->InitAppProcess(aArgc, aArgv);
+  forkserver.mAppProcBuilder.reset();
+
+  MOZ_ASSERT("tab"_ns == (*aArgv)[*aArgc - 1], "Only |tab| is allowed!");
+
+  // Open log files again with right names and the new PID.
+  nsTraceRefcnt::ResetLogFiles((*aArgv)[*aArgc - 1]);
+
+  return false;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ForkServer.h b/ipc/glue/ForkServer.h
new file mode 100644
index 0000000000..ba4ed9d44e
--- /dev/null
+++ b/ipc/glue/ForkServer.h
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 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 __FORKSERVER_H_
+#define __FORKSERVER_H_
+
+#include "mozilla/UniquePtr.h"
+#include "base/process_util.h"
+#include "mozilla/ipc/MiniTransceiver.h"
+
+namespace mozilla {
+namespace ipc {
+
+class ForkServer {
+ public:
+  // NOTE: This can re-use the same ID as the initial IPC::Channel, as the
+  // initial IPC::Channel will not be used by the fork server.
+  static constexpr int kClientPipeFd = 3;
+
+  ForkServer();
+  ~ForkServer(){};
+
+  void InitProcess(int* aArgc, char*** aArgv);
+  bool HandleMessages();
+
+  // Called when a message is received.
+  void OnMessageReceived(UniquePtr<IPC::Message> message);
+
+  static bool RunForkServer(int* aArgc, char*** aArgv);
+
+ private:
+  UniquePtr<MiniTransceiver> mTcver;
+  UniquePtr<base::AppProcessBuilder> mAppProcBuilder;
+};
+
+enum {
+  Msg_ForkNewSubprocess__ID = 0x7f0,  // a random picked number
+  Reply_ForkNewSubprocess__ID,
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // __FORKSERVER_H_
diff --git a/ipc/glue/ForkServiceChild.cpp b/ipc/glue/ForkServiceChild.cpp
new file mode 100644
index 0000000000..db130343cc
--- /dev/null
+++ b/ipc/glue/ForkServiceChild.cpp
@@ -0,0 +1,190 @@
+/* -*- 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 "ForkServiceChild.h"
+#include "ForkServer.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "mozilla/Logging.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/Services.h"
+#include "ipc/IPCMessageUtilsSpecializations.h"
+#include "nsIObserverService.h"
+
+#include <unistd.h>
+#include <fcntl.h>
+
+namespace mozilla {
+namespace ipc {
+
+extern LazyLogModule gForkServiceLog;
+
+mozilla::UniquePtr<ForkServiceChild> ForkServiceChild::sForkServiceChild;
+
+static bool ConfigurePipeFd(int aFd) {
+  int flags = fcntl(aFd, F_GETFD, 0);
+  return flags != -1 && fcntl(aFd, F_SETFD, flags | FD_CLOEXEC) != -1;
+}
+
+void ForkServiceChild::StartForkServer() {
+  // Create the socket to use for communication, and mark both ends as
+  // FD_CLOEXEC.
+  int fds[2];
+  if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) < 0) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Error,
+            ("failed to create fork server socket"));
+    return;
+  }
+  UniqueFileHandle server(fds[0]);
+  UniqueFileHandle client(fds[1]);
+
+  if (!ConfigurePipeFd(server.get()) || !ConfigurePipeFd(client.get())) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Error,
+            ("failed to configure fork server socket"));
+    return;
+  }
+
+  GeckoChildProcessHost* subprocess =
+      new GeckoChildProcessHost(GeckoProcessType_ForkServer, false);
+  subprocess->AddFdToRemap(client.get(), ForkServer::kClientPipeFd);
+  if (!subprocess->LaunchAndWaitForProcessHandle(std::vector<std::string>{})) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Error, ("failed to launch fork server"));
+    return;
+  }
+
+  sForkServiceChild =
+      mozilla::MakeUnique<ForkServiceChild>(server.release(), subprocess);
+}
+
+void ForkServiceChild::StopForkServer() { sForkServiceChild = nullptr; }
+
+ForkServiceChild::ForkServiceChild(int aFd, GeckoChildProcessHost* aProcess)
+    : mFailed(false), mProcess(aProcess) {
+  mTcver = MakeUnique<MiniTransceiver>(aFd);
+}
+
+ForkServiceChild::~ForkServiceChild() {
+  mProcess->Destroy();
+  close(mTcver->GetFD());
+}
+
+Result<Ok, LaunchError> ForkServiceChild::SendForkNewSubprocess(
+    const nsTArray<nsCString>& aArgv, const nsTArray<EnvVar>& aEnvMap,
+    const nsTArray<FdMapping>& aFdsRemap, pid_t* aPid) {
+  mRecvPid = -1;
+  IPC::Message msg(MSG_ROUTING_CONTROL, Msg_ForkNewSubprocess__ID);
+
+  IPC::MessageWriter writer(msg);
+  WriteIPDLParam(&writer, nullptr, aArgv);
+  WriteIPDLParam(&writer, nullptr, aEnvMap);
+  WriteIPDLParam(&writer, nullptr, aFdsRemap);
+  if (!mTcver->Send(msg)) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Verbose,
+            ("the pipe to the fork server is closed or having errors"));
+    OnError();
+    return Err(LaunchError("FSC::SFNS::Send"));
+  }
+
+  UniquePtr<IPC::Message> reply;
+  if (!mTcver->Recv(reply)) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Verbose,
+            ("the pipe to the fork server is closed or having errors"));
+    OnError();
+    return Err(LaunchError("FSC::SFNS::Recv"));
+  }
+  OnMessageReceived(std::move(reply));
+
+  MOZ_ASSERT(mRecvPid != -1);
+  *aPid = mRecvPid;
+  return Ok();
+}
+
+void ForkServiceChild::OnMessageReceived(UniquePtr<IPC::Message> message) {
+  if (message->type() != Reply_ForkNewSubprocess__ID) {
+    MOZ_LOG(gForkServiceLog, LogLevel::Verbose,
+            ("unknown reply type %d", message->type()));
+    return;
+  }
+  IPC::MessageReader reader(*message);
+
+  if (!ReadIPDLParam(&reader, nullptr, &mRecvPid)) {
+    MOZ_CRASH("Error deserializing 'pid_t'");
+  }
+  reader.EndRead();
+}
+
+void ForkServiceChild::OnError() {
+  mFailed = true;
+  ForkServerLauncher::RestartForkServer();
+}
+
+NS_IMPL_ISUPPORTS(ForkServerLauncher, nsIObserver)
+
+bool ForkServerLauncher::mHaveStartedClient = false;
+StaticRefPtr<ForkServerLauncher> ForkServerLauncher::mSingleton;
+
+ForkServerLauncher::ForkServerLauncher() {}
+
+ForkServerLauncher::~ForkServerLauncher() {}
+
+already_AddRefed<ForkServerLauncher> ForkServerLauncher::Create() {
+  if (mSingleton == nullptr) {
+    mSingleton = new ForkServerLauncher();
+  }
+  RefPtr<ForkServerLauncher> launcher = mSingleton;
+  return launcher.forget();
+}
+
+NS_IMETHODIMP
+ForkServerLauncher::Observe(nsISupports* aSubject, const char* aTopic,
+                            const char16_t* aData) {
+  if (strcmp(aTopic, NS_XPCOM_STARTUP_CATEGORY) == 0) {
+    nsCOMPtr<nsIObserverService> obsSvc =
+        mozilla::services::GetObserverService();
+    MOZ_ASSERT(obsSvc != nullptr);
+    // preferences are not available until final-ui-startup
+    obsSvc->AddObserver(this, "final-ui-startup", false);
+  } else if (!mHaveStartedClient && strcmp(aTopic, "final-ui-startup") == 0) {
+    if (StaticPrefs::dom_ipc_forkserver_enable_AtStartup()) {
+      mHaveStartedClient = true;
+      ForkServiceChild::StartForkServer();
+
+      nsCOMPtr<nsIObserverService> obsSvc =
+          mozilla::services::GetObserverService();
+      MOZ_ASSERT(obsSvc != nullptr);
+      obsSvc->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
+    } else {
+      mSingleton = nullptr;
+    }
+  }
+
+  if (strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
+    if (mHaveStartedClient) {
+      mHaveStartedClient = false;
+      ForkServiceChild::StopForkServer();
+    }
+
+    // To make leak checker happy!
+    mSingleton = nullptr;
+  }
+  return NS_OK;
+}
+
+void ForkServerLauncher::RestartForkServer() {
+  // Restart fork server
+  NS_SUCCEEDED(NS_DispatchToMainThreadQueue(
+      NS_NewRunnableFunction("OnForkServerError",
+                             [] {
+                               if (mSingleton) {
+                                 ForkServiceChild::StopForkServer();
+                                 ForkServiceChild::StartForkServer();
+                               }
+                             }),
+      EventQueuePriority::Idle));
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ForkServiceChild.h b/ipc/glue/ForkServiceChild.h
new file mode 100644
index 0000000000..40699df061
--- /dev/null
+++ b/ipc/glue/ForkServiceChild.h
@@ -0,0 +1,105 @@
+/* -*- 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 __FORKSERVICE_CHILD_H_
+#define __FORKSERVICE_CHILD_H_
+
+#include "base/process_util.h"
+#include "nsIObserver.h"
+#include "nsString.h"
+#include "mozilla/ipc/MiniTransceiver.h"
+#include "mozilla/ipc/LaunchError.h"
+#include "mozilla/Result.h"
+
+#include <sys/types.h>
+#include <poll.h>
+
+namespace mozilla {
+namespace ipc {
+
+class GeckoChildProcessHost;
+
+/**
+ * This is the interface to the fork server.
+ *
+ * When the chrome process calls |ForkServiceChild| to create a new
+ * process, this class send a message to the fork server through a
+ * pipe and get the PID of the new process from the reply.
+ */
+class ForkServiceChild {
+ public:
+  ForkServiceChild(int aFd, GeckoChildProcessHost* aProcess);
+  virtual ~ForkServiceChild();
+
+  /**
+   * Ask the fork server to create a new process with given parameters.
+   *
+   * The fork server uses |base::LaunchApp()| to create a new
+   * content process with the following parameters.
+   *
+   * \param aArgv assigns |argv| of the content process.
+   * \param aEnvMap sets |LaunchOptions::env_map|.
+   * \param aFdsRemap sets |LaunchOptions::fd_to_remap|.
+   * \param aPid returns the PID of the content process created.
+   * \return true if success.
+   */
+  Result<Ok, LaunchError> SendForkNewSubprocess(
+      const nsTArray<nsCString>& aArgv, const nsTArray<EnvVar>& aEnvMap,
+      const nsTArray<FdMapping>& aFdsRemap, pid_t* aPid);
+
+  /**
+   * Create a fork server process and the singleton of this class.
+   *
+   * This function uses |GeckoChildProcessHost| to launch the fork
+   * server, getting the fd of a pipe/socket to the fork server from
+   * it's |IPC::Channel|.
+   */
+  static void StartForkServer();
+  static void StopForkServer();
+  /**
+   * Return the singleton.
+   */
+  static ForkServiceChild* Get() {
+    auto child = sForkServiceChild.get();
+    return child == nullptr || child->mFailed ? nullptr : child;
+  }
+
+ private:
+  // Called when a message is received.
+  void OnMessageReceived(UniquePtr<IPC::Message> message);
+  void OnError();
+
+  UniquePtr<MiniTransceiver> mTcver;
+  static UniquePtr<ForkServiceChild> sForkServiceChild;
+  pid_t mRecvPid;
+  bool mFailed;  // The forkserver has crashed or disconnected.
+  GeckoChildProcessHost* mProcess;
+};
+
+/**
+ * Start a fork server at |xpcom-startup| from the chrome process.
+ */
+class ForkServerLauncher : public nsIObserver {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  ForkServerLauncher();
+  static already_AddRefed<ForkServerLauncher> Create();
+
+ private:
+  friend class ForkServiceChild;
+  virtual ~ForkServerLauncher();
+
+  static void RestartForkServer();
+
+  static bool mHaveStartedClient;
+  static StaticRefPtr<ForkServerLauncher> mSingleton;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif /* __FORKSERVICE_CHILD_H_ */
diff --git a/ipc/glue/GeckoChildProcessHost.cpp b/ipc/glue/GeckoChildProcessHost.cpp
new file mode 100644
index 0000000000..b4895e0e45
--- /dev/null
+++ b/ipc/glue/GeckoChildProcessHost.cpp
@@ -0,0 +1,1896 @@
+/* -*- 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 "GeckoChildProcessHost.h"
+
+#include "base/command_line.h"
+#include "base/process_util.h"
+#include "base/string_util.h"
+#include "base/task.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/process_watcher.h"
+#ifdef MOZ_WIDGET_COCOA
+#  include <bsm/libbsm.h>
+#  include <mach/mach_traps.h>
+#  include <servers/bootstrap.h>
+#  include "SharedMemoryBasic.h"
+#  include "base/rand_util.h"
+#  include "chrome/common/mach_ipc_mac.h"
+#  include "nsILocalFileMac.h"
+#endif
+
+#include "GeckoProfiler.h"
+#include "MainThreadUtils.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Sprintf.h"
+#include "nsXPCOMPrivate.h"
+#include "prenv.h"
+#include "prerror.h"
+
+#if defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxSettings.h"
+#  include "nsAppDirectoryServiceDefs.h"
+#endif
+
+#include <sys/stat.h>
+
+#include "ProtocolUtils.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/GeckoArgs.h"
+#include "mozilla/Omnijar.h"
+#include "mozilla/RDDProcessHost.h"
+#include "mozilla/Scoped.h"
+#include "mozilla/Services.h"
+#include "mozilla/SharedThreadPool.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/TaskQueue.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/ipc/BrowserProcessSubThread.h"
+#include "mozilla/ipc/EnvironmentMap.h"
+#include "mozilla/ipc/NodeController.h"
+#include "mozilla/net/SocketProcessHost.h"
+#include "nsDirectoryService.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsExceptionHandler.h"
+#include "nsIFile.h"
+#include "nsIObserverService.h"
+#include "nsPrintfCString.h"
+
+#ifdef XP_WIN
+#  include <stdlib.h>
+
+#  include "nsIWinTaskbar.h"
+#  define NS_TASKBAR_CONTRACTID "@mozilla.org/windows-taskbar;1"
+
+#  if defined(MOZ_SANDBOX)
+#    include "WinUtils.h"
+#    include "mozilla/Preferences.h"
+#    include "mozilla/sandboxing/sandboxLogging.h"
+#    if defined(_ARM64_)
+#      include "mozilla/remoteSandboxBroker.h"
+#    endif
+#  endif
+
+#  include "mozilla/NativeNt.h"
+#  include "mozilla/CacheNtDllThunk.h"
+#endif
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxLaunch.h"
+#endif
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+#  include "GMPProcessParent.h"
+#  include "nsMacUtilsImpl.h"
+#endif
+
+#include "mozilla/ipc/UtilityProcessHost.h"
+
+#include "nsClassHashtable.h"
+#include "nsHashKeys.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsTArray.h"
+#include "nscore.h"  // for NS_FREE_PERMANENT_DATA
+#include "private/pprio.h"
+#include "nsIThread.h"
+
+using mozilla::MonitorAutoLock;
+using mozilla::Preferences;
+using mozilla::StaticMutexAutoLock;
+
+namespace mozilla {
+MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPRFileDesc, PRFileDesc,
+                                          PR_Close)
+}
+
+using mozilla::ScopedPRFileDesc;
+
+#ifdef MOZ_WIDGET_ANDROID
+#  include "AndroidBridge.h"
+#  include "mozilla/java/GeckoProcessManagerWrappers.h"
+#  include "mozilla/java/GeckoProcessTypeWrappers.h"
+#  include "mozilla/java/GeckoResultWrappers.h"
+#  include "mozilla/jni/Refs.h"
+#  include "mozilla/jni/Utils.h"
+#endif
+
+#ifdef MOZ_ENABLE_FORKSERVER
+#  include "mozilla/ipc/ForkServiceChild.h"
+#endif
+
+static bool ShouldHaveDirectoryService() {
+  return GeckoProcessType_Default == XRE_GetProcessType();
+}
+
+namespace mozilla {
+namespace ipc {
+
+struct LaunchResults {
+  base::ProcessHandle mHandle = 0;
+#ifdef XP_MACOSX
+  task_t mChildTask = MACH_PORT_NULL;
+#endif
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+  RefPtr<AbstractSandboxBroker> mSandboxBroker;
+#endif
+};
+typedef mozilla::MozPromise<LaunchResults, LaunchError, true>
+    ProcessLaunchPromise;
+
+static Atomic<int32_t> gChildCounter;
+
+static inline nsISerialEventTarget* IOThread() {
+  return XRE_GetIOMessageLoop()->SerialEventTarget();
+}
+
+class BaseProcessLauncher {
+ public:
+  BaseProcessLauncher(GeckoChildProcessHost* aHost,
+                      std::vector<std::string>&& aExtraOpts)
+      : mProcessType(aHost->mProcessType),
+        mLaunchOptions(std::move(aHost->mLaunchOptions)),
+        mExtraOpts(std::move(aExtraOpts)),
+#ifdef XP_WIN
+        mGroupId(aHost->mGroupId),
+#endif
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+        mAllowedFilesRead(aHost->mAllowedFilesRead),
+        mSandboxLevel(aHost->mSandboxLevel),
+        mSandbox(aHost->mSandbox),
+        mIsFileContent(aHost->mIsFileContent),
+        mEnableSandboxLogging(aHost->mEnableSandboxLogging),
+#endif
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+        mDisableOSActivityMode(aHost->mDisableOSActivityMode),
+#endif
+        mTmpDirName(aHost->mTmpDirName),
+        mChildId(++gChildCounter) {
+    SprintfLiteral(mPidString, "%" PRIPID, base::GetCurrentProcId());
+    aHost->mInitialChannelId.ToProvidedString(mInitialChannelIdString);
+
+    // Compute the serial event target we'll use for launching.
+    nsCOMPtr<nsIEventTarget> threadOrPool = GetIPCLauncher();
+    mLaunchThread =
+        TaskQueue::Create(threadOrPool.forget(), "BaseProcessLauncher");
+
+    if (ShouldHaveDirectoryService()) {
+      // "Current process directory" means the app dir, not the current
+      // working dir or similar.
+      mozilla::Unused
+          << nsDirectoryService::gService->GetCurrentProcessDirectory(
+                 getter_AddRefs(mAppDir));
+    }
+  }
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(BaseProcessLauncher);
+
+#ifdef ALLOW_GECKO_CHILD_PROCESS_ARCH
+  void SetLaunchArchitecture(uint32_t aLaunchArch) {
+    mLaunchArch = aLaunchArch;
+  }
+#endif
+
+  RefPtr<ProcessLaunchPromise> Launch(GeckoChildProcessHost*);
+
+ protected:
+  virtual ~BaseProcessLauncher() = default;
+
+  RefPtr<ProcessLaunchPromise> PerformAsyncLaunch();
+  RefPtr<ProcessLaunchPromise> FinishLaunch();
+
+  // Overrideable hooks. If superclass behavior is invoked, it's always at the
+  // top of the override.
+  virtual bool SetChannel(IPC::Channel*) = 0;
+  virtual Result<Ok, LaunchError> DoSetup();
+  virtual RefPtr<ProcessHandlePromise> DoLaunch() = 0;
+  virtual Result<Ok, LaunchError> DoFinishLaunch() { return Ok(); };
+
+  void MapChildLogging();
+
+  static BinPathType GetPathToBinary(FilePath&, GeckoProcessType);
+
+  void GetChildLogName(const char* origLogName, nsACString& buffer);
+
+  const char* ChildProcessType() {
+    return XRE_GeckoProcessTypeToString(mProcessType);
+  }
+
+  nsCOMPtr<nsISerialEventTarget> mLaunchThread;
+  GeckoProcessType mProcessType;
+  UniquePtr<base::LaunchOptions> mLaunchOptions;
+#ifdef ALLOW_GECKO_CHILD_PROCESS_ARCH
+  uint32_t mLaunchArch = base::PROCESS_ARCH_INVALID;
+#endif
+  std::vector<std::string> mExtraOpts;
+#ifdef XP_WIN
+  nsString mGroupId;
+#endif
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+  std::vector<std::wstring> mAllowedFilesRead;
+  int32_t mSandboxLevel;
+  SandboxingKind mSandbox;
+  bool mIsFileContent;
+  bool mEnableSandboxLogging;
+#endif
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  // Controls whether or not the process will be launched with
+  // environment variable OS_ACTIVITY_MODE set to "disabled".
+  bool mDisableOSActivityMode;
+#endif
+  nsCString mTmpDirName;
+  LaunchResults mResults = LaunchResults();
+  int32_t mChildId;
+  TimeStamp mStartTimeStamp = TimeStamp::Now();
+  char mPidString[32];
+  char mInitialChannelIdString[NSID_LENGTH];
+
+  // Set during launch.
+  IPC::Channel::ChannelId mChannelId;
+  ScopedPRFileDesc mCrashAnnotationReadPipe;
+  ScopedPRFileDesc mCrashAnnotationWritePipe;
+  nsCOMPtr<nsIFile> mAppDir;
+};
+
+#ifdef XP_WIN
+class WindowsProcessLauncher : public BaseProcessLauncher {
+ public:
+  WindowsProcessLauncher(GeckoChildProcessHost* aHost,
+                         std::vector<std::string>&& aExtraOpts)
+      : BaseProcessLauncher(aHost, std::move(aExtraOpts)),
+        mCachedNtdllThunk(GetCachedNtDllThunk()),
+        mWerDataPointer(&(aHost->mWerData)) {}
+
+ protected:
+  bool SetChannel(IPC::Channel*) override { return true; }
+  virtual Result<Ok, LaunchError> DoSetup() override;
+  virtual RefPtr<ProcessHandlePromise> DoLaunch() override;
+  virtual Result<Ok, LaunchError> DoFinishLaunch() override;
+
+  mozilla::Maybe<CommandLine> mCmdLine;
+  bool mUseSandbox = false;
+
+  const Buffer<IMAGE_THUNK_DATA>* mCachedNtdllThunk;
+  CrashReporter::WindowsErrorReportingData const* mWerDataPointer;
+};
+typedef WindowsProcessLauncher ProcessLauncher;
+#endif  // XP_WIN
+
+#ifdef OS_POSIX
+class PosixProcessLauncher : public BaseProcessLauncher {
+ public:
+  PosixProcessLauncher(GeckoChildProcessHost* aHost,
+                       std::vector<std::string>&& aExtraOpts)
+      : BaseProcessLauncher(aHost, std::move(aExtraOpts)),
+        mProfileDir(aHost->mProfileDir),
+        mChannelDstFd(-1) {}
+
+ protected:
+  bool SetChannel(IPC::Channel* aChannel) override {
+    // The source fd is owned by the channel; take ownership by
+    // dup()ing it and closing the channel's copy.  The destination fd
+    // is with respect to the not-yet-launched child process, so for
+    // this purpose it's just a number.
+    int origSrcFd;
+    aChannel->GetClientFileDescriptorMapping(&origSrcFd, &mChannelDstFd);
+#  ifndef MOZ_WIDGET_ANDROID
+    MOZ_ASSERT(mChannelDstFd >= 0);
+#  endif
+    mChannelSrcFd.reset(dup(origSrcFd));
+    if (NS_WARN_IF(!mChannelSrcFd)) {
+      return false;
+    }
+    aChannel->CloseClientFileDescriptor();
+    return true;
+  }
+
+  virtual Result<Ok, LaunchError> DoSetup() override;
+  virtual RefPtr<ProcessHandlePromise> DoLaunch() override;
+  virtual Result<Ok, LaunchError> DoFinishLaunch() override;
+
+  nsCOMPtr<nsIFile> mProfileDir;
+
+  std::vector<std::string> mChildArgv;
+  UniqueFileHandle mChannelSrcFd;
+  int mChannelDstFd;
+};
+
+#  if defined(XP_MACOSX)
+class MacProcessLauncher : public PosixProcessLauncher {
+ public:
+  MacProcessLauncher(GeckoChildProcessHost* aHost,
+                     std::vector<std::string>&& aExtraOpts)
+      : PosixProcessLauncher(aHost, std::move(aExtraOpts)),
+        // Put a random number into the channel name, so that
+        // a compromised renderer can't pretend being the child
+        // that's forked off.
+        mMachConnectionName(
+            StringPrintf("org.mozilla.machname.%d",
+                         base::RandInt(0, std::numeric_limits<int>::max()))) {
+    MOZ_ASSERT(mMachConnectionName.size() < BOOTSTRAP_MAX_NAME_LEN);
+  }
+
+ protected:
+  virtual Result<Ok, LaunchError> DoFinishLaunch() override;
+
+  std::string mMachConnectionName;
+  // We add a mach port to the command line so the child can communicate its
+  // 'task_t' back to the parent.
+  mozilla::UniqueMachReceiveRight mParentRecvPort;
+
+  friend class PosixProcessLauncher;
+};
+typedef MacProcessLauncher ProcessLauncher;
+#  elif defined(MOZ_WIDGET_ANDROID)
+class AndroidProcessLauncher : public PosixProcessLauncher {
+ public:
+  AndroidProcessLauncher(GeckoChildProcessHost* aHost,
+                         std::vector<std::string>&& aExtraOpts)
+      : PosixProcessLauncher(aHost, std::move(aExtraOpts)) {}
+
+ protected:
+  virtual RefPtr<ProcessHandlePromise> DoLaunch() override;
+  RefPtr<ProcessHandlePromise> LaunchAndroidService(
+      const GeckoProcessType aType, const std::vector<std::string>& argv,
+      const base::file_handle_mapping_vector& fds_to_remap);
+};
+typedef AndroidProcessLauncher ProcessLauncher;
+// NB: Technically Android is linux (i.e. XP_LINUX is defined), but we want
+// orthogonal IPC machinery there. Conversely, there are tier-3 non-Linux
+// platforms (BSD and Solaris) where we want the "linux" IPC machinery. So
+// we use MOZ_WIDGET_* to choose the platform backend.
+#  elif defined(MOZ_WIDGET_GTK)
+class LinuxProcessLauncher : public PosixProcessLauncher {
+ public:
+  LinuxProcessLauncher(GeckoChildProcessHost* aHost,
+                       std::vector<std::string>&& aExtraOpts)
+      : PosixProcessLauncher(aHost, std::move(aExtraOpts)) {}
+
+ protected:
+  virtual Result<Ok, LaunchError> DoSetup() override;
+};
+typedef LinuxProcessLauncher ProcessLauncher;
+#  elif
+#    error "Unknown platform"
+#  endif
+#endif  // OS_POSIX
+
+using base::ProcessHandle;
+using mozilla::ipc::BaseProcessLauncher;
+using mozilla::ipc::ProcessLauncher;
+
+mozilla::StaticAutoPtr<mozilla::LinkedList<GeckoChildProcessHost>>
+    GeckoChildProcessHost::sGeckoChildProcessHosts;
+
+mozilla::StaticMutex GeckoChildProcessHost::sMutex;
+
+GeckoChildProcessHost::GeckoChildProcessHost(GeckoProcessType aProcessType,
+                                             bool aIsFileContent)
+    : mProcessType(aProcessType),
+      mIsFileContent(aIsFileContent),
+      mMonitor("mozilla.ipc.GeckoChildProcessHost.mMonitor"),
+      mLaunchOptions(MakeUnique<base::LaunchOptions>()),
+      mInitialChannelId(nsID::GenerateUUID()),
+      mProcessState(CREATING_CHANNEL),
+#ifdef XP_WIN
+      mGroupId(u"-"),
+      mWerData{.mWerNotifyProc = CrashReporter::WerNotifyProc,
+               .mChildPid = 0,
+               .mMinidumpFile = {}},
+#endif
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+      mEnableSandboxLogging(false),
+      mSandboxLevel(0),
+#endif
+      mHandleLock("mozilla.ipc.GeckoChildProcessHost.mHandleLock"),
+      mChildProcessHandle(0),
+#if defined(MOZ_WIDGET_COCOA)
+      mChildTask(MACH_PORT_NULL),
+#endif
+#if defined(MOZ_SANDBOX) && defined(XP_MACOSX)
+      mDisableOSActivityMode(false),
+#endif
+      mDestroying(false) {
+  MOZ_COUNT_CTOR(GeckoChildProcessHost);
+  StaticMutexAutoLock lock(sMutex);
+  if (!sGeckoChildProcessHosts) {
+    sGeckoChildProcessHosts = new mozilla::LinkedList<GeckoChildProcessHost>();
+  }
+  sGeckoChildProcessHosts->insertBack(this);
+#if defined(MOZ_SANDBOX) && defined(XP_LINUX)
+  if (aProcessType == GeckoProcessType_Content) {
+#  if defined(MOZ_CONTENT_TEMP_DIR)
+    // The content process needs the content temp dir:
+    nsCOMPtr<nsIFile> contentTempDir;
+    nsresult rv = NS_GetSpecialDirectory(NS_APP_CONTENT_PROCESS_TEMP_DIR,
+                                         getter_AddRefs(contentTempDir));
+    if (NS_SUCCEEDED(rv)) {
+      contentTempDir->GetNativePath(mTmpDirName);
+    }
+#  endif
+  } else if (aProcessType == GeckoProcessType_RDD) {
+    // The RDD process makes limited use of EGL.  If Mesa's shader
+    // cache is enabled and the directory isn't explicitly set, then
+    // it will try to getpwuid() the user which can cause problems
+    // with sandboxing.  Because we shouldn't need shader caching in
+    // this process, we just disable the cache to prevent that.
+    mLaunchOptions->env_map["MESA_GLSL_CACHE_DISABLE"] = "true";
+    mLaunchOptions->env_map["MESA_SHADER_CACHE_DISABLE"] = "true";
+    // In case the nvidia driver is also loaded:
+    mLaunchOptions->env_map["__GL_SHADER_DISK_CACHE"] = "0";
+  }
+#endif
+#if defined(MOZ_ENABLE_FORKSERVER)
+  if (aProcessType == GeckoProcessType_Content && ForkServiceChild::Get()) {
+    mLaunchOptions->use_forkserver = true;
+  }
+#endif
+}
+
+GeckoChildProcessHost::~GeckoChildProcessHost()
+
+{
+  AssertIOThread();
+  MOZ_RELEASE_ASSERT(mDestroying);
+
+  MOZ_COUNT_DTOR(GeckoChildProcessHost);
+
+  {
+    mozilla::AutoWriteLock hLock(mHandleLock);
+#if defined(MOZ_WIDGET_COCOA)
+    if (mChildTask != MACH_PORT_NULL) {
+      mach_port_deallocate(mach_task_self(), mChildTask);
+    }
+#endif
+
+    if (mChildProcessHandle != 0) {
+#if defined(XP_WIN)
+      CrashReporter::DeregisterChildCrashAnnotationFileDescriptor(
+          base::GetProcId(mChildProcessHandle));
+#else
+      CrashReporter::DeregisterChildCrashAnnotationFileDescriptor(
+          mChildProcessHandle);
+#endif
+
+      ProcessWatcher::EnsureProcessTerminated(
+          mChildProcessHandle
+#ifdef NS_FREE_PERMANENT_DATA
+          // If we're doing leak logging, shutdown can be slow.
+          ,
+          false  // don't "force"
+#endif
+      );
+      mChildProcessHandle = 0;
+    }
+  }
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+  if (mSandboxBroker) {
+    mSandboxBroker->Shutdown();
+    mSandboxBroker = nullptr;
+  }
+#endif
+}
+
+base::ProcessHandle GeckoChildProcessHost::GetChildProcessHandle() {
+  mozilla::AutoReadLock handleLock(mHandleLock);
+  return mChildProcessHandle;
+}
+
+base::ProcessId GeckoChildProcessHost::GetChildProcessId() {
+  mozilla::AutoReadLock handleLock(mHandleLock);
+  if (!mChildProcessHandle) {
+    return 0;
+  }
+  return base::GetProcId(mChildProcessHandle);
+}
+
+#ifdef XP_MACOSX
+task_t GeckoChildProcessHost::GetChildTask() {
+  mozilla::AutoReadLock handleLock(mHandleLock);
+  return mChildTask;
+}
+#endif
+
+void GeckoChildProcessHost::RemoveFromProcessList() {
+  StaticMutexAutoLock lock(sMutex);
+  if (!sGeckoChildProcessHosts) {
+    return;
+  }
+  LinkedListElement<GeckoChildProcessHost>::removeFrom(
+      *sGeckoChildProcessHosts);
+}
+
+void GeckoChildProcessHost::Destroy() {
+  MOZ_RELEASE_ASSERT(!mDestroying);
+  // We can remove from the list before it's really destroyed
+  RemoveFromProcessList();
+  RefPtr<ProcessHandlePromise> whenReady = mHandlePromise;
+
+  if (!whenReady) {
+    // AsyncLaunch not called yet, so dispatch immediately.
+    whenReady = ProcessHandlePromise::CreateAndReject(
+        LaunchError("DestroyEarly"), __func__);
+  }
+
+  using Value = ProcessHandlePromise::ResolveOrRejectValue;
+  mDestroying = true;
+  whenReady->Then(XRE_GetIOMessageLoop()->SerialEventTarget(), __func__,
+                  [this](const Value&) { delete this; });
+}
+
+// static
+mozilla::BinPathType BaseProcessLauncher::GetPathToBinary(
+    FilePath& exePath, GeckoProcessType processType) {
+  BinPathType pathType = XRE_GetChildProcBinPathType(processType);
+
+  if (pathType == BinPathType::Self) {
+#if defined(OS_WIN)
+    wchar_t exePathBuf[MAXPATHLEN];
+    if (!::GetModuleFileNameW(nullptr, exePathBuf, MAXPATHLEN)) {
+      MOZ_CRASH("GetModuleFileNameW failed (FIXME)");
+    }
+    exePath = FilePath::FromWStringHack(exePathBuf);
+#elif defined(OS_POSIX)
+    exePath = FilePath(CommandLine::ForCurrentProcess()->argv()[0]);
+#else
+#  error Sorry; target OS not supported yet.
+#endif
+    return pathType;
+  }
+
+  if (ShouldHaveDirectoryService()) {
+    MOZ_ASSERT(gGREBinPath);
+#ifdef OS_WIN
+    exePath = FilePath(char16ptr_t(gGREBinPath));
+#elif MOZ_WIDGET_COCOA
+    nsCOMPtr<nsIFile> childProcPath;
+    NS_NewLocalFile(nsDependentString(gGREBinPath), false,
+                    getter_AddRefs(childProcPath));
+
+    // We need to use an App Bundle on OS X so that we can hide
+    // the dock icon. See Bug 557225.
+    childProcPath->AppendNative("plugin-container.app"_ns);
+    childProcPath->AppendNative("Contents"_ns);
+    childProcPath->AppendNative("MacOS"_ns);
+    nsCString tempCPath;
+    childProcPath->GetNativePath(tempCPath);
+    exePath = FilePath(tempCPath.get());
+#else
+    nsCString path;
+    NS_CopyUnicodeToNative(nsDependentString(gGREBinPath), path);
+    exePath = FilePath(path.get());
+#endif
+  }
+
+  if (exePath.empty()) {
+#ifdef OS_WIN
+    exePath =
+        FilePath::FromWStringHack(CommandLine::ForCurrentProcess()->program());
+#else
+    exePath = FilePath(CommandLine::ForCurrentProcess()->argv()[0]);
+#endif
+    exePath = exePath.DirName();
+  }
+
+  exePath = exePath.AppendASCII(MOZ_CHILD_PROCESS_NAME);
+
+  return pathType;
+}
+
+#ifdef MOZ_WIDGET_COCOA
+class AutoCFTypeObject {
+ public:
+  explicit AutoCFTypeObject(CFTypeRef object) { mObject = object; }
+  ~AutoCFTypeObject() { ::CFRelease(mObject); }
+
+ private:
+  CFTypeRef mObject;
+};
+#endif
+
+// We start the unique IDs at 1 so that 0 can be used to mean that
+// a component has no unique ID assigned to it.
+uint32_t GeckoChildProcessHost::sNextUniqueID = 1;
+
+/* static */
+uint32_t GeckoChildProcessHost::GetUniqueID() { return sNextUniqueID++; }
+
+/* static */
+void GeckoChildProcessHost::SetEnv(const char* aKey, const char* aValue) {
+  MOZ_ASSERT(mLaunchOptions);
+  mLaunchOptions->env_map[ENVIRONMENT_STRING(aKey)] =
+      ENVIRONMENT_STRING(aValue);
+}
+
+void GeckoChildProcessHost::PrepareLaunch() {
+  if (CrashReporter::GetEnabled()) {
+    CrashReporter::OOPInit();
+  }
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+  SandboxLaunchPrepare(mProcessType, mLaunchOptions.get());
+#endif
+
+#ifdef XP_WIN
+
+#  if defined(MOZ_SANDBOX)
+  // We need to get the pref here as the process is launched off main thread.
+  if (mProcessType == GeckoProcessType_Content) {
+    // Win32k Lockdown state must be initialized on the main thread.
+    // This is our last chance to do it before it is read on the IPC Launch
+    // thread
+    GetWin32kLockdownState();
+    mSandboxLevel = GetEffectiveContentSandboxLevel();
+    mEnableSandboxLogging =
+        Preferences::GetBool("security.sandbox.logging.enabled");
+
+    // We currently have to whitelist certain paths for tests to work in some
+    // development configurations.
+    nsAutoString readPaths;
+    nsresult rv = Preferences::GetString(
+        "security.sandbox.content.read_path_whitelist", readPaths);
+    if (NS_SUCCEEDED(rv)) {
+      for (const nsAString& readPath : readPaths.Split(',')) {
+        nsString trimmedPath(readPath);
+        trimmedPath.Trim(" ", true, true);
+        std::wstring resolvedPath(trimmedPath.Data());
+        // Check if path ends with '\' as this indicates we want to give read
+        // access to a directory and so it needs a wildcard.
+        if (resolvedPath.back() == L'\\') {
+          resolvedPath.append(L"*");
+        }
+        mAllowedFilesRead.push_back(resolvedPath);
+      }
+    }
+  }
+#  endif
+
+#  if defined(MOZ_SANDBOX)
+  // For other process types we can't rely on them being launched on main
+  // thread and they may not have access to prefs in the child process, so allow
+  // them to turn on logging via an environment variable.
+  mEnableSandboxLogging =
+      mEnableSandboxLogging || !!PR_GetEnv("MOZ_SANDBOX_LOGGING");
+
+#  endif
+#elif defined(XP_MACOSX)
+#  if defined(MOZ_SANDBOX)
+  if (ShouldHaveDirectoryService() &&
+      mProcessType != GeckoProcessType_GMPlugin) {
+    mozilla::Unused << NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                                              getter_AddRefs(mProfileDir));
+  }
+#  endif
+#endif
+}
+
+#ifdef XP_WIN
+void GeckoChildProcessHost::InitWindowsGroupID() {
+  // On Win7+, pass the application user model to the child, so it can
+  // register with it. This insures windows created by the container
+  // properly group with the parent app on the Win7 taskbar.
+  nsCOMPtr<nsIWinTaskbar> taskbarInfo = do_GetService(NS_TASKBAR_CONTRACTID);
+  if (taskbarInfo) {
+    bool isSupported = false;
+    taskbarInfo->GetAvailable(&isSupported);
+    nsAutoString appId;
+    if (isSupported && NS_SUCCEEDED(taskbarInfo->GetDefaultGroupId(appId))) {
+      MOZ_ASSERT(mGroupId.EqualsLiteral("-"));
+      mGroupId.Assign(appId);
+    }
+  }
+}
+#endif
+
+bool GeckoChildProcessHost::SyncLaunch(std::vector<std::string> aExtraOpts,
+                                       int aTimeoutMs) {
+  if (!AsyncLaunch(std::move(aExtraOpts))) {
+    return false;
+  }
+  return WaitUntilConnected(aTimeoutMs);
+}
+
+// Note: for most process types, we currently call AsyncLaunch, and therefore
+// the *ProcessLauncher constructor, on the main thread, while the
+// ProcessLauncher methods to actually execute the launch are called on the IO
+// or IPC launcher thread. GMP processes are an exception - the GMP code
+// invokes GeckoChildProcessHost from non-main-threads, and therefore we cannot
+// rely on having access to mainthread-only services (like the directory
+// service) from this code if we're launching that type of process.
+bool GeckoChildProcessHost::AsyncLaunch(std::vector<std::string> aExtraOpts) {
+  PrepareLaunch();
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  if (IsMacSandboxLaunchEnabled() && !AppendMacSandboxParams(aExtraOpts)) {
+    return false;
+  }
+#endif
+
+  RefPtr<BaseProcessLauncher> launcher =
+      new ProcessLauncher(this, std::move(aExtraOpts));
+#ifdef ALLOW_GECKO_CHILD_PROCESS_ARCH
+  launcher->SetLaunchArchitecture(mLaunchArch);
+#endif
+
+  // Note: Destroy() waits on mHandlePromise to delete |this|. As such, we want
+  // to be sure that all of our post-launch processing on |this| happens before
+  // mHandlePromise notifies.
+  MOZ_ASSERT(mHandlePromise == nullptr);
+  mHandlePromise =
+      mozilla::InvokeAsync<GeckoChildProcessHost*>(
+          IOThread(), launcher.get(), __func__, &BaseProcessLauncher::Launch,
+          this)
+          ->Then(
+              IOThread(), __func__,
+              [this](LaunchResults&& aResults) {
+                {
+                  {
+                    mozilla::AutoWriteLock handleLock(mHandleLock);
+                    if (!OpenPrivilegedHandle(base::GetProcId(aResults.mHandle))
+#ifdef XP_WIN
+                        // If we failed in opening the process handle, try
+                        // harder by duplicating one.
+                        && !::DuplicateHandle(
+                               ::GetCurrentProcess(), aResults.mHandle,
+                               ::GetCurrentProcess(), &mChildProcessHandle,
+                               PROCESS_DUP_HANDLE | PROCESS_TERMINATE |
+                                   PROCESS_QUERY_INFORMATION | PROCESS_VM_READ |
+                                   SYNCHRONIZE,
+                               FALSE, 0)
+#endif  // XP_WIN
+                    ) {
+                      MOZ_CRASH("cannot open handle to child process");
+                    }
+                    // The original handle is no longer needed; it must
+                    // be closed to prevent a resource leak.
+                    base::CloseProcessHandle(aResults.mHandle);
+                    // FIXME (bug 1720523): define a cross-platform
+                    // "safe" invalid value to use in places like this.
+                    aResults.mHandle = 0;
+
+#ifdef XP_MACOSX
+                    this->mChildTask = aResults.mChildTask;
+                    if (mNodeChannel) {
+                      mNodeChannel->SetMachTaskPort(this->mChildTask);
+                    }
+#endif
+                  }
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+                  this->mSandboxBroker = std::move(aResults.mSandboxBroker);
+#endif
+
+                  MonitorAutoLock lock(mMonitor);
+                  // The OnChannel{Connected,Error} may have already advanced
+                  // the state.
+                  if (mProcessState < PROCESS_CREATED) {
+                    mProcessState = PROCESS_CREATED;
+                  }
+                  lock.Notify();
+                }
+                return ProcessHandlePromise::CreateAndResolve(
+                    GetChildProcessHandle(), __func__);
+              },
+              [this](const LaunchError aError) {
+                // WaitUntilConnected might be waiting for us to signal.
+                // If something failed let's set the error state and notify.
+                CHROMIUM_LOG(ERROR)
+                    << "Failed to launch "
+                    << XRE_GeckoProcessTypeToString(mProcessType)
+                    << " subprocess";
+                Telemetry::Accumulate(
+                    Telemetry::SUBPROCESS_LAUNCH_FAILURE,
+                    nsDependentCString(
+                        XRE_GeckoProcessTypeToString(mProcessType)));
+                nsCString telemetryKey = nsPrintfCString(
+#if defined(XP_WIN)
+                    "%s,0x%lx,%s",
+#else
+                    "%s,%d,%s",
+#endif
+                    aError.FunctionName(), aError.ErrorCode(),
+                    XRE_GeckoProcessTypeToString(mProcessType));
+                // Max telemetry key is 72 chars
+                // https://searchfox.org/mozilla-central/rev/c244b16815d1fc827d141472b9faac5610f250e7/toolkit/components/telemetry/core/TelemetryScalar.cpp#105
+                if (telemetryKey.Length() > 72) {
+                  NS_WARNING(nsPrintfCString("Truncating telemetry key: %s",
+                                             telemetryKey.get())
+                                 .get());
+                  telemetryKey.Truncate(72);
+                }
+                Telemetry::ScalarAdd(
+                    Telemetry::ScalarID::
+                        DOM_PARENTPROCESS_PROCESS_LAUNCH_ERRORS,
+                    NS_ConvertUTF8toUTF16(telemetryKey), 1);
+                {
+                  MonitorAutoLock lock(mMonitor);
+                  mProcessState = PROCESS_ERROR;
+                  lock.Notify();
+                }
+                return ProcessHandlePromise::CreateAndReject(aError, __func__);
+              });
+  return true;
+}
+
+bool GeckoChildProcessHost::WaitUntilConnected(int32_t aTimeoutMs) {
+  AUTO_PROFILER_LABEL("GeckoChildProcessHost::WaitUntilConnected", OTHER);
+
+  // NB: this uses a different mechanism than the chromium parent
+  // class.
+  TimeDuration timeout = (aTimeoutMs > 0)
+                             ? TimeDuration::FromMilliseconds(aTimeoutMs)
+                             : TimeDuration::Forever();
+
+  MonitorAutoLock lock(mMonitor);
+  TimeStamp waitStart = TimeStamp::Now();
+  TimeStamp current;
+
+  // We'll receive several notifications, we need to exit when we
+  // have either successfully launched or have timed out.
+  while (mProcessState != PROCESS_CONNECTED) {
+    // If there was an error then return it, don't wait out the timeout.
+    if (mProcessState == PROCESS_ERROR) {
+      break;
+    }
+
+    CVStatus status = lock.Wait(timeout);
+    if (status == CVStatus::Timeout) {
+      break;
+    }
+
+    if (timeout != TimeDuration::Forever()) {
+      current = TimeStamp::Now();
+      timeout -= current - waitStart;
+      waitStart = current;
+    }
+  }
+
+  return mProcessState == PROCESS_CONNECTED;
+}
+
+bool GeckoChildProcessHost::WaitForProcessHandle() {
+  MonitorAutoLock lock(mMonitor);
+  while (mProcessState < PROCESS_CREATED) {
+    lock.Wait();
+  }
+  MOZ_ASSERT(mProcessState == PROCESS_ERROR || GetChildProcessHandle());
+
+  return mProcessState < PROCESS_ERROR;
+}
+
+bool GeckoChildProcessHost::LaunchAndWaitForProcessHandle(
+    StringVector aExtraOpts) {
+  if (!AsyncLaunch(std::move(aExtraOpts))) {
+    return false;
+  }
+  return WaitForProcessHandle();
+}
+
+void GeckoChildProcessHost::InitializeChannel(
+    const std::function<void(IPC::Channel*)>& aChannelReady) {
+  CreateChannel();
+
+  aChannelReady(GetChannel());
+
+  mNodeController = NodeController::GetSingleton();
+  std::tie(mInitialPort, mNodeChannel) =
+      mNodeController->InviteChildProcess(TakeChannel());
+
+  MonitorAutoLock lock(mMonitor);
+  mProcessState = CHANNEL_INITIALIZED;
+  lock.Notify();
+}
+
+void GeckoChildProcessHost::SetAlreadyDead() {
+  mozilla::AutoWriteLock handleLock(mHandleLock);
+  if (mChildProcessHandle &&
+      mChildProcessHandle != base::kInvalidProcessHandle) {
+    base::CloseProcessHandle(mChildProcessHandle);
+  }
+
+  mChildProcessHandle = 0;
+}
+
+void BaseProcessLauncher::GetChildLogName(const char* origLogName,
+                                          nsACString& buffer) {
+#ifdef XP_WIN
+  // On Windows we must expand relative paths because sandboxing rules
+  // bound only to full paths.  fopen fowards to NtCreateFile which checks
+  // the path against the sanboxing rules as passed to fopen (left relative).
+  char absPath[MAX_PATH + 2];
+  if (_fullpath(absPath, origLogName, sizeof(absPath))) {
+    buffer.Append(absPath);
+  } else
+#endif
+  {
+    buffer.Append(origLogName);
+  }
+
+  // Remove .moz_log extension to avoid its duplication, it will be added
+  // automatically by the logging backend
+  static constexpr auto kMozLogExt = nsLiteralCString{MOZ_LOG_FILE_EXTENSION};
+  if (StringEndsWith(buffer, kMozLogExt)) {
+    buffer.Truncate(buffer.Length() - kMozLogExt.Length());
+  }
+
+  // Append child-specific postfix to name
+  buffer.AppendLiteral(".child-");
+  buffer.AppendInt(mChildId);
+}
+
+// Windows needs a single dedicated thread for process launching,
+// because of thread-safety restrictions/assertions in the sandbox
+// code.
+//
+// Android also needs a single dedicated thread to simplify thread
+// safety in java.
+//
+// Fork server needs a dedicated thread for accessing
+// |ForkServiceChild|.
+#if defined(XP_WIN) || defined(MOZ_WIDGET_ANDROID) || \
+    defined(MOZ_ENABLE_FORKSERVER)
+
+static mozilla::StaticMutex gIPCLaunchThreadMutex;
+static mozilla::StaticRefPtr<nsIThread> gIPCLaunchThread
+    MOZ_GUARDED_BY(gIPCLaunchThreadMutex);
+
+class IPCLaunchThreadObserver final : public nsIObserver {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+ protected:
+  virtual ~IPCLaunchThreadObserver() = default;
+};
+
+NS_IMPL_ISUPPORTS(IPCLaunchThreadObserver, nsIObserver, nsISupports)
+
+NS_IMETHODIMP
+IPCLaunchThreadObserver::Observe(nsISupports* aSubject, const char* aTopic,
+                                 const char16_t* aData) {
+  MOZ_RELEASE_ASSERT(strcmp(aTopic, "xpcom-shutdown-threads") == 0);
+  StaticMutexAutoLock lock(gIPCLaunchThreadMutex);
+
+  nsresult rv = NS_OK;
+  if (gIPCLaunchThread) {
+    rv = gIPCLaunchThread->Shutdown();
+    gIPCLaunchThread = nullptr;
+  }
+  mozilla::Unused << NS_WARN_IF(NS_FAILED(rv));
+  return rv;
+}
+
+nsCOMPtr<nsIEventTarget> GetIPCLauncher() {
+  StaticMutexAutoLock lock(gIPCLaunchThreadMutex);
+  if (!gIPCLaunchThread) {
+    nsCOMPtr<nsIThread> thread;
+    nsresult rv = NS_NewNamedThread("IPC Launch"_ns, getter_AddRefs(thread));
+    if (!NS_WARN_IF(NS_FAILED(rv))) {
+      NS_DispatchToMainThread(
+          NS_NewRunnableFunction("GeckoChildProcessHost::GetIPCLauncher", [] {
+            nsCOMPtr<nsIObserverService> obsService =
+                mozilla::services::GetObserverService();
+            nsCOMPtr<nsIObserver> obs = new IPCLaunchThreadObserver();
+            obsService->AddObserver(obs, "xpcom-shutdown-threads", false);
+          }));
+      gIPCLaunchThread = thread.forget();
+    }
+  }
+
+  nsCOMPtr<nsIEventTarget> thread = gIPCLaunchThread.get();
+  MOZ_DIAGNOSTIC_ASSERT(thread);
+  return thread;
+}
+
+#else  // defined(XP_WIN) || defined(MOZ_WIDGET_ANDROID) ||
+       // defined(MOZ_ENABLE_FORKSERVER)
+
+// Other platforms use an on-demand thread pool.
+
+nsCOMPtr<nsIEventTarget> GetIPCLauncher() {
+  nsCOMPtr<nsIEventTarget> pool =
+      mozilla::SharedThreadPool::Get("IPC Launch"_ns);
+  MOZ_DIAGNOSTIC_ASSERT(pool);
+  return pool;
+}
+
+#endif  // XP_WIN || MOZ_WIDGET_ANDROID || MOZ_ENABLE_FORKSERVER
+
+void
+#if defined(XP_WIN)
+AddAppDirToCommandLine(CommandLine& aCmdLine, nsIFile* aAppDir)
+#else
+AddAppDirToCommandLine(std::vector<std::string>& aCmdLine, nsIFile* aAppDir,
+    nsIFile* aProfileDir)
+#endif
+{
+  // Content processes need access to application resources, so pass
+  // the full application directory path to the child process.
+  if (aAppDir) {
+#if defined(XP_WIN)
+    nsString path;
+    MOZ_ALWAYS_SUCCEEDS(aAppDir->GetPath(path));
+    aCmdLine.AppendLooseValue(UTF8ToWide(geckoargs::sAppDir.Name()));
+    std::wstring wpath(path.get());
+    aCmdLine.AppendLooseValue(wpath);
+#else
+    nsAutoCString path;
+    MOZ_ALWAYS_SUCCEEDS(aAppDir->GetNativePath(path));
+    geckoargs::sAppDir.Put(path.get(), aCmdLine);
+#endif
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+    // Full path to the profile dir
+    if (aProfileDir) {
+      // If the profile doesn't exist, normalization will
+      // fail. But we don't return an error here because some
+      // tests require startup with a missing profile dir.
+      // For users, almost universally, the profile will be in
+      // the home directory and normalization isn't required.
+      mozilla::Unused << aProfileDir->Normalize();
+      nsAutoCString path;
+      MOZ_ALWAYS_SUCCEEDS(aProfileDir->GetNativePath(path));
+      geckoargs::sProfile.Put(path.get(), aCmdLine);
+    }
+#endif
+  }
+}
+
+#if defined(XP_WIN) && (defined(MOZ_SANDBOX) || defined(_ARM64_))
+static bool Contains(const std::vector<std::string>& aExtraOpts,
+                     const char* aValue) {
+  return std::any_of(aExtraOpts.begin(), aExtraOpts.end(),
+                     [&](const std::string arg) {
+                       return arg.find(aValue) != std::string::npos;
+                     });
+}
+#endif  // defined(XP_WIN) && (defined(MOZ_SANDBOX) || defined(_ARM64_))
+
+RefPtr<ProcessLaunchPromise> BaseProcessLauncher::PerformAsyncLaunch() {
+  Result<Ok, LaunchError> aError = DoSetup();
+  if (aError.isErr()) {
+    return ProcessLaunchPromise::CreateAndReject(aError.unwrapErr(), __func__);
+  }
+  RefPtr<BaseProcessLauncher> self = this;
+  return DoLaunch()->Then(
+      mLaunchThread, __func__,
+      [self](base::ProcessHandle aHandle) {
+        self->mResults.mHandle = aHandle;
+        return self->FinishLaunch();
+      },
+      [](LaunchError aError) {
+        return ProcessLaunchPromise::CreateAndReject(aError, __func__);
+      });
+}
+
+Result<Ok, LaunchError> BaseProcessLauncher::DoSetup() {
+  RefPtr<BaseProcessLauncher> self = this;
+  GetProfilerEnvVarsForChildProcess([self](const char* key, const char* value) {
+    self->mLaunchOptions->env_map[ENVIRONMENT_STRING(key)] =
+        ENVIRONMENT_STRING(value);
+  });
+#ifdef MOZ_MEMORY
+  if (mProcessType == GeckoProcessType_Content) {
+    nsAutoCString mallocOpts(PR_GetEnv("MALLOC_OPTIONS"));
+    // Disable randomization of small arenas in content.
+    mallocOpts.Append("r");
+    self->mLaunchOptions->env_map[ENVIRONMENT_LITERAL("MALLOC_OPTIONS")] =
+        ENVIRONMENT_STRING(mallocOpts.get());
+  }
+#endif
+
+  MapChildLogging();
+
+  PRStatus status = PR_CreatePipe(&mCrashAnnotationReadPipe.rwget(),
+                                  &mCrashAnnotationWritePipe.rwget());
+  if (status != PR_SUCCESS) {
+    return Err(LaunchError("PR_CreatePipe", PR_GetError()));
+  }
+  return Ok();
+}
+
+void BaseProcessLauncher::MapChildLogging() {
+  const char* origNSPRLogName = PR_GetEnv("NSPR_LOG_FILE");
+  const char* origMozLogName = PR_GetEnv("MOZ_LOG_FILE");
+
+  if (origNSPRLogName) {
+    nsAutoCString nsprLogName;
+    GetChildLogName(origNSPRLogName, nsprLogName);
+    mLaunchOptions->env_map[ENVIRONMENT_LITERAL("NSPR_LOG_FILE")] =
+        ENVIRONMENT_STRING(nsprLogName.get());
+  }
+  if (origMozLogName) {
+    nsAutoCString mozLogName;
+    GetChildLogName(origMozLogName, mozLogName);
+    mLaunchOptions->env_map[ENVIRONMENT_LITERAL("MOZ_LOG_FILE")] =
+        ENVIRONMENT_STRING(mozLogName.get());
+  }
+
+  // `RUST_LOG_CHILD` is meant for logging child processes only.
+  nsAutoCString childRustLog(PR_GetEnv("RUST_LOG_CHILD"));
+  if (!childRustLog.IsEmpty()) {
+    mLaunchOptions->env_map[ENVIRONMENT_LITERAL("RUST_LOG")] =
+        ENVIRONMENT_STRING(childRustLog.get());
+  }
+}
+
+#if defined(MOZ_WIDGET_GTK)
+Result<Ok, LaunchError> LinuxProcessLauncher::DoSetup() {
+  Result<Ok, LaunchError> aError = PosixProcessLauncher::DoSetup();
+  if (aError.isErr()) {
+    return aError;
+  }
+
+  if (mProcessType == GeckoProcessType_Content) {
+    // disable IM module to avoid sandbox violation
+    mLaunchOptions->env_map["GTK_IM_MODULE"] = "gtk-im-context-simple";
+
+    // Disable ATK accessibility code in content processes because it conflicts
+    // with the sandbox, and we proxy that information through the main process
+    // anyway.
+    mLaunchOptions->env_map["NO_AT_BRIDGE"] = "1";
+  }
+
+#  ifdef MOZ_SANDBOX
+  if (!mTmpDirName.IsEmpty()) {
+    // Point a bunch of things that might want to write from content to our
+    // shiny new content-process specific tmpdir
+    mLaunchOptions->env_map[ENVIRONMENT_LITERAL("TMPDIR")] =
+        ENVIRONMENT_STRING(mTmpDirName.get());
+    // Partial fix for bug 1380051 (not persistent - should be)
+    mLaunchOptions->env_map[ENVIRONMENT_LITERAL("MESA_GLSL_CACHE_DIR")] =
+        ENVIRONMENT_STRING(mTmpDirName.get());
+  }
+#  endif  // MOZ_SANDBOX
+
+  return Ok();
+}
+#endif  // MOZ_WIDGET_GTK
+
+#ifdef OS_POSIX
+Result<Ok, LaunchError> PosixProcessLauncher::DoSetup() {
+  Result<Ok, LaunchError> aError = BaseProcessLauncher::DoSetup();
+  if (aError.isErr()) {
+    return aError;
+  }
+
+  // XPCOM may not be initialized in some subprocesses.  We don't want
+  // to initialize XPCOM just for the directory service, especially
+  // since LD_LIBRARY_PATH is already set correctly in subprocesses
+  // (meaning that we don't need to set that up in the environment).
+  if (ShouldHaveDirectoryService()) {
+    MOZ_ASSERT(gGREBinPath);
+    nsCString path;
+    NS_CopyUnicodeToNative(nsDependentString(gGREBinPath), path);
+#  if defined(OS_LINUX) || defined(OS_BSD)
+    const char* ld_library_path = PR_GetEnv("LD_LIBRARY_PATH");
+    nsCString new_ld_lib_path(path.get());
+
+    if (ld_library_path && *ld_library_path) {
+      new_ld_lib_path.Append(':');
+      new_ld_lib_path.Append(ld_library_path);
+    }
+    mLaunchOptions->env_map["LD_LIBRARY_PATH"] = new_ld_lib_path.get();
+
+#  elif OS_MACOSX  // defined(OS_LINUX) || defined(OS_BSD)
+    // With signed production Mac builds, the dynamic linker (dyld) will
+    // ignore dyld environment variables preventing the use of variables
+    // such as DYLD_LIBRARY_PATH and DYLD_INSERT_LIBRARIES.
+
+    // If we're running with gtests, add the gtest XUL ahead of normal XUL on
+    // the DYLD_LIBRARY_PATH so that plugin-container.app loads it instead.
+    nsCString new_dyld_lib_path(path.get());
+    if (PR_GetEnv("MOZ_RUN_GTEST")) {
+      new_dyld_lib_path = path + "/gtest:"_ns + new_dyld_lib_path;
+      mLaunchOptions->env_map["DYLD_LIBRARY_PATH"] = new_dyld_lib_path.get();
+    }
+
+    // DYLD_INSERT_LIBRARIES is currently unused by default but we allow
+    // it to be set by the external environment.
+    const char* interpose = PR_GetEnv("DYLD_INSERT_LIBRARIES");
+    if (interpose && strlen(interpose) > 0) {
+      mLaunchOptions->env_map["DYLD_INSERT_LIBRARIES"] = interpose;
+    }
+
+    // Prevent connection attempts to diagnosticd(8) to save cycles. Log
+    // messages can trigger these connection attempts, but access to
+    // diagnosticd is blocked in sandboxed child processes.
+#    ifdef MOZ_SANDBOX
+    if (mDisableOSActivityMode) {
+      mLaunchOptions->env_map["OS_ACTIVITY_MODE"] = "disable";
+    }
+#    endif  // defined(MOZ_SANDBOX)
+#  endif    // defined(OS_LINUX) || defined(OS_BSD)
+  }
+
+  FilePath exePath;
+  BinPathType pathType = GetPathToBinary(exePath, mProcessType);
+
+  // remap the IPC socket fd to a well-known int, as the OS does for
+  // STDOUT_FILENO, for example
+  // The fork server doesn't use IPC::Channel, so can skip this step.
+  if (mProcessType != GeckoProcessType_ForkServer) {
+#  ifdef MOZ_WIDGET_ANDROID
+    // On Android mChannelDstFd is uninitialised and the launching code uses
+    // only the first of each pair.
+    mLaunchOptions->fds_to_remap.push_back(
+        std::pair<int, int>(mChannelSrcFd.get(), -1));
+#  else
+    MOZ_ASSERT(mChannelDstFd >= 0);
+    mLaunchOptions->fds_to_remap.push_back(
+        std::pair<int, int>(mChannelSrcFd.get(), mChannelDstFd));
+#  endif
+  }
+
+  // no need for kProcessChannelID, the child process inherits the
+  // other end of the socketpair() from us
+
+  mChildArgv.push_back(exePath.value());
+
+  if (pathType == BinPathType::Self) {
+    mChildArgv.push_back("-contentproc");
+  }
+
+  mChildArgv.insert(mChildArgv.end(), mExtraOpts.begin(), mExtraOpts.end());
+
+  if (mProcessType != GeckoProcessType_GMPlugin) {
+#  if defined(MOZ_WIDGET_ANDROID)
+    if (Omnijar::IsInitialized()) {
+      // Make sure that child processes can find the omnijar
+      // See XRE_InitCommandLine in nsAppRunner.cpp
+      nsAutoCString path;
+      nsCOMPtr<nsIFile> file = Omnijar::GetPath(Omnijar::GRE);
+      if (file && NS_SUCCEEDED(file->GetNativePath(path))) {
+        mChildArgv.push_back("-greomni");
+        mChildArgv.push_back(path.get());
+      }
+    }
+#  endif
+    // Add the application directory path (-appdir path)
+#  ifdef XP_MACOSX
+    AddAppDirToCommandLine(mChildArgv, mAppDir, mProfileDir);
+#  else
+    AddAppDirToCommandLine(mChildArgv, mAppDir, nullptr);
+#  endif
+  }
+
+  mChildArgv.push_back(mInitialChannelIdString);
+
+  mChildArgv.push_back(mPidString);
+
+  if (!CrashReporter::IsDummy()) {
+#  if defined(OS_LINUX) || defined(OS_BSD) || defined(OS_SOLARIS)
+    int childCrashFd, childCrashRemapFd;
+    if (NS_WARN_IF(!CrashReporter::CreateNotificationPipeForChild(
+            &childCrashFd, &childCrashRemapFd))) {
+      return Err(LaunchError("CR::CreateNotificationPipeForChild"));
+    }
+
+    if (0 <= childCrashFd) {
+      mLaunchOptions->fds_to_remap.push_back(
+          std::pair<int, int>(childCrashFd, childCrashRemapFd));
+      // "true" == crash reporting enabled
+      mChildArgv.push_back("true");
+    } else {
+      // "false" == crash reporting disabled
+      mChildArgv.push_back("false");
+    }
+#  elif defined(MOZ_WIDGET_COCOA) /* defined(OS_LINUX) || defined(OS_BSD) || \
+                                     defined(OS_SOLARIS) */
+    mChildArgv.push_back(CrashReporter::GetChildNotificationPipe());
+#  endif  // defined(OS_LINUX) || defined(OS_BSD) || defined(OS_SOLARIS)
+  }
+
+  int fd = PR_FileDesc2NativeHandle(mCrashAnnotationWritePipe);
+  mLaunchOptions->fds_to_remap.push_back(
+      std::make_pair(fd, CrashReporter::GetAnnotationTimeCrashFd()));
+
+#  ifdef MOZ_WIDGET_COCOA
+  {
+    auto* thisMac = static_cast<MacProcessLauncher*>(this);
+    kern_return_t kr =
+        bootstrap_check_in(bootstrap_port, thisMac->mMachConnectionName.c_str(),
+                           getter_Transfers(thisMac->mParentRecvPort));
+    if (kr != KERN_SUCCESS) {
+      CHROMIUM_LOG(ERROR) << "parent bootstrap_check_in failed: "
+                          << mach_error_string(kr);
+      return Err(LaunchError("bootstrap_check_in", kr));
+    }
+    mChildArgv.push_back(thisMac->mMachConnectionName.c_str());
+  }
+#  endif  // MOZ_WIDGET_COCOA
+
+  mChildArgv.push_back(ChildProcessType());
+  return Ok();
+}
+#endif  // OS_POSIX
+
+#if defined(MOZ_WIDGET_ANDROID)
+RefPtr<ProcessHandlePromise> AndroidProcessLauncher::DoLaunch() {
+  return LaunchAndroidService(mProcessType, mChildArgv,
+                              mLaunchOptions->fds_to_remap);
+}
+#endif  // MOZ_WIDGET_ANDROID
+
+#ifdef OS_POSIX
+RefPtr<ProcessHandlePromise> PosixProcessLauncher::DoLaunch() {
+  ProcessHandle handle = 0;
+  Result<Ok, LaunchError> aError =
+      base::LaunchApp(mChildArgv, *mLaunchOptions, &handle);
+  if (aError.isErr()) {
+    return ProcessHandlePromise::CreateAndReject(aError.unwrapErr(), __func__);
+  }
+  return ProcessHandlePromise::CreateAndResolve(handle, __func__);
+}
+
+Result<Ok, LaunchError> PosixProcessLauncher::DoFinishLaunch() {
+  Result<Ok, LaunchError> aError = BaseProcessLauncher::DoFinishLaunch();
+  if (aError.isErr()) {
+    return aError;
+  }
+
+  // We're in the parent and the child was launched. Close the child FD in the
+  // parent as soon as possible, which will allow the parent to detect when the
+  // child closes its FD (either due to normal exit or due to crash).
+  mChannelSrcFd = nullptr;
+
+  return Ok();
+}
+#endif  // OS_POSIX
+
+#ifdef XP_MACOSX
+Result<Ok, LaunchError> MacProcessLauncher::DoFinishLaunch() {
+  Result<Ok, LaunchError> aError = PosixProcessLauncher::DoFinishLaunch();
+  if (aError.isErr()) {
+    return aError;
+  }
+
+  MOZ_ASSERT(mParentRecvPort, "should have been configured during DoSetup()");
+
+  // Wait for the child process to send us its 'task_t' data.
+  const int kTimeoutMs = 10000;
+
+  mozilla::UniqueMachSendRight child_task;
+  audit_token_t audit_token{};
+  kern_return_t kr = MachReceivePortSendRight(
+      mParentRecvPort, mozilla::Some(kTimeoutMs), &child_task, &audit_token);
+  if (kr != KERN_SUCCESS) {
+    std::string errString = StringPrintf("0x%x %s", kr, mach_error_string(kr));
+    CHROMIUM_LOG(ERROR) << "parent MachReceivePortSendRight failed: "
+                        << errString;
+    return Err(LaunchError("MachReceivePortSendRight", kr));
+  }
+
+  // Ensure the message was sent by the newly spawned child process.
+  if (audit_token_to_pid(audit_token) != base::GetProcId(mResults.mHandle)) {
+    CHROMIUM_LOG(ERROR) << "task_t was not sent by child process";
+    return Err(LaunchError("audit_token_to_pid"));
+  }
+
+  // Ensure the task_t corresponds to the newly spawned child process.
+  pid_t task_pid = -1;
+  kr = pid_for_task(child_task.get(), &task_pid);
+  if (kr != KERN_SUCCESS) {
+    CHROMIUM_LOG(ERROR) << "pid_for_task failed: " << mach_error_string(kr);
+    return Err(LaunchError("pid_for_task", kr));
+  }
+  if (task_pid != base::GetProcId(mResults.mHandle)) {
+    CHROMIUM_LOG(ERROR) << "task_t is not for child process";
+    return Err(LaunchError("task_pid"));
+  }
+
+  mResults.mChildTask = child_task.release();
+
+  return Ok();
+}
+#endif  // XP_MACOSX
+
+#ifdef XP_WIN
+Result<Ok, LaunchError> WindowsProcessLauncher::DoSetup() {
+  Result<Ok, LaunchError> aError = BaseProcessLauncher::DoSetup();
+  if (aError.isErr()) {
+    return aError;
+  }
+
+  FilePath exePath;
+  BinPathType pathType = GetPathToBinary(exePath, mProcessType);
+
+#  if defined(MOZ_SANDBOX) || defined(_ARM64_)
+  const bool isGMP = mProcessType == GeckoProcessType_GMPlugin;
+  const bool isWidevine = isGMP && Contains(mExtraOpts, "gmp-widevinecdm");
+#    if defined(_ARM64_)
+  bool useRemoteSandboxBroker = false;
+  if (mLaunchArch & (base::PROCESS_ARCH_I386 | base::PROCESS_ARCH_X86_64)) {
+    // On Windows on ARM64 for ClearKey and Widevine, and for the sandbox
+    // launcher process, we want to run the x86 plugin-container.exe in
+    // the "i686" subdirectory, instead of the aarch64 plugin-container.exe.
+    // So insert "i686" into the exePath.
+    exePath = exePath.DirName().AppendASCII("i686").Append(exePath.BaseName());
+    useRemoteSandboxBroker =
+        mProcessType != GeckoProcessType_RemoteSandboxBroker;
+  }
+#    endif  // if defined(_ARM64_)
+#  endif    // defined(MOZ_SANDBOX) || defined(_ARM64_)
+
+  mCmdLine.emplace(exePath.ToWStringHack());
+
+  if (pathType == BinPathType::Self) {
+    mCmdLine->AppendLooseValue(UTF8ToWide("-contentproc"));
+  }
+
+#  ifdef HAS_DLL_BLOCKLIST
+  if (IsDynamicBlocklistDisabled(
+          gSafeMode,
+          CommandLine::ForCurrentProcess()->HasSwitch(UTF8ToWide(
+              mozilla::geckoargs::sDisableDynamicDllBlocklist.sMatch)))) {
+    mCmdLine->AppendLooseValue(
+        UTF8ToWide(mozilla::geckoargs::sDisableDynamicDllBlocklist.sMatch));
+  }
+#  endif  // HAS_DLL_BLOCKLIST
+
+  mCmdLine->AppendSwitchWithValue(switches::kProcessChannelID, mChannelId);
+
+  for (std::vector<std::string>::iterator it = mExtraOpts.begin();
+       it != mExtraOpts.end(); ++it) {
+    mCmdLine->AppendLooseValue(UTF8ToWide(*it));
+  }
+
+#  if defined(MOZ_SANDBOX)
+#    if defined(_ARM64_)
+  if (useRemoteSandboxBroker)
+    mResults.mSandboxBroker = new RemoteSandboxBroker(mLaunchArch);
+  else
+#    endif  // if defined(_ARM64_)
+    mResults.mSandboxBroker = new SandboxBroker();
+
+  // XXX: Bug 1124167: We should get rid of the process specific logic for
+  // sandboxing in this class at some point. Unfortunately it will take a bit
+  // of reorganizing so I don't think this patch is the right time.
+  switch (mProcessType) {
+    case GeckoProcessType_Content:
+      if (mSandboxLevel > 0) {
+        // For now we treat every failure as fatal in
+        // SetSecurityLevelForContentProcess and just crash there right away.
+        // Should this change in the future then we should also handle the error
+        // here.
+        mResults.mSandboxBroker->SetSecurityLevelForContentProcess(
+            mSandboxLevel, mIsFileContent);
+        mUseSandbox = true;
+      }
+      break;
+    case GeckoProcessType_IPDLUnitTest:
+      // XXX: We don't sandbox this process type yet
+      break;
+    case GeckoProcessType_GMPlugin:
+      if (!PR_GetEnv("MOZ_DISABLE_GMP_SANDBOX")) {
+        // The Widevine CDM on Windows can only load at USER_RESTRICTED,
+        // not at USER_LOCKDOWN. So look in the command line arguments
+        // to see if we're loading the path to the Widevine CDM, and if
+        // so use sandbox level USER_RESTRICTED instead of USER_LOCKDOWN.
+        auto level =
+            isWidevine ? SandboxBroker::Restricted : SandboxBroker::LockDown;
+        if (NS_WARN_IF(
+                !mResults.mSandboxBroker->SetSecurityLevelForGMPlugin(level))) {
+          return Err(LaunchError("SetSecurityLevelForGMPlugin"));
+        }
+        mUseSandbox = true;
+      }
+      break;
+    case GeckoProcessType_GPU:
+      if (mSandboxLevel > 0 && !PR_GetEnv("MOZ_DISABLE_GPU_SANDBOX")) {
+        // For now we treat every failure as fatal in
+        // SetSecurityLevelForGPUProcess and just crash there right away. Should
+        // this change in the future then we should also handle the error here.
+        mResults.mSandboxBroker->SetSecurityLevelForGPUProcess(mSandboxLevel);
+        mUseSandbox = true;
+      }
+      break;
+    case GeckoProcessType_VR:
+      if (mSandboxLevel > 0 && !PR_GetEnv("MOZ_DISABLE_VR_SANDBOX")) {
+        // TODO: Implement sandbox for VR process, Bug 1430043.
+      }
+      break;
+    case GeckoProcessType_RDD:
+      if (!PR_GetEnv("MOZ_DISABLE_RDD_SANDBOX")) {
+        if (NS_WARN_IF(
+                !mResults.mSandboxBroker->SetSecurityLevelForRDDProcess())) {
+          return Err(LaunchError("SetSecurityLevelForRDDProcess"));
+        }
+        mUseSandbox = true;
+      }
+      break;
+    case GeckoProcessType_Socket:
+      if (!PR_GetEnv("MOZ_DISABLE_SOCKET_PROCESS_SANDBOX")) {
+        if (NS_WARN_IF(
+                !mResults.mSandboxBroker->SetSecurityLevelForSocketProcess())) {
+          return Err(LaunchError("SetSecurityLevelForSocketProcess"));
+        }
+        mUseSandbox = true;
+      }
+      break;
+    case GeckoProcessType_Utility:
+      if (!PR_GetEnv("MOZ_DISABLE_UTILITY_SANDBOX")) {
+        if (!mResults.mSandboxBroker->SetSecurityLevelForUtilityProcess(
+                mSandbox)) {
+          return Err(LaunchError("SetSecurityLevelForUtilityProcess"));
+        }
+        mUseSandbox = true;
+      }
+      break;
+    case GeckoProcessType_RemoteSandboxBroker:
+      // We don't sandbox the sandbox launcher...
+      break;
+    case GeckoProcessType_Default:
+    default:
+      MOZ_CRASH("Bad process type in GeckoChildProcessHost");
+      break;
+  };
+
+  if (mUseSandbox) {
+    for (auto it = mAllowedFilesRead.begin(); it != mAllowedFilesRead.end();
+         ++it) {
+      mResults.mSandboxBroker->AllowReadFile(it->c_str());
+    }
+
+    if (mResults.mSandboxBroker->IsWin32kLockedDown()) {
+      mCmdLine->AppendLooseValue(
+          UTF8ToWide(geckoargs::sWin32kLockedDown.Name()));
+    }
+  }
+#  endif  // defined(MOZ_SANDBOX)
+
+  // Add the application directory path (-appdir path)
+  AddAppDirToCommandLine(mCmdLine.ref(), mAppDir);
+
+  // XXX Command line params past this point are expected to be at
+  // the end of the command line string, and in a specific order.
+  // See XRE_InitChildProcess in nsEmbedFunction.
+
+  // Win app model id
+  mCmdLine->AppendLooseValue(mGroupId.get());
+
+  // Initial MessageChannel id
+  mCmdLine->AppendLooseValue(UTF8ToWide(mInitialChannelIdString));
+
+  // Process id
+  mCmdLine->AppendLooseValue(UTF8ToWide(mPidString));
+
+  mCmdLine->AppendLooseValue(
+      UTF8ToWide(CrashReporter::GetChildNotificationPipe()));
+
+  if (!CrashReporter::IsDummy()) {
+    PROsfd h = PR_FileDesc2NativeHandle(mCrashAnnotationWritePipe);
+    mLaunchOptions->handles_to_inherit.push_back(reinterpret_cast<HANDLE>(h));
+    std::string hStr = std::to_string(h);
+    mCmdLine->AppendLooseValue(UTF8ToWide(hStr));
+
+    char werDataAddress[17] = {};
+    SprintfLiteral(werDataAddress, "%p", mWerDataPointer);
+    mCmdLine->AppendLooseValue(UTF8ToWide(werDataAddress));
+  }
+
+  // Process type
+  mCmdLine->AppendLooseValue(UTF8ToWide(ChildProcessType()));
+
+#  ifdef MOZ_SANDBOX
+  if (mUseSandbox) {
+    // Mark the handles to inherit as inheritable.
+    for (HANDLE h : mLaunchOptions->handles_to_inherit) {
+      mResults.mSandboxBroker->AddHandleToShare(h);
+    }
+  }
+#  endif  // MOZ_SANDBOX
+
+  return Ok();
+}
+
+RefPtr<ProcessHandlePromise> WindowsProcessLauncher::DoLaunch() {
+  ProcessHandle handle = 0;
+#  ifdef MOZ_SANDBOX
+  if (mUseSandbox) {
+    const IMAGE_THUNK_DATA* cachedNtdllThunk =
+        mCachedNtdllThunk ? mCachedNtdllThunk->begin() : nullptr;
+    Result<Ok, LaunchError> err = mResults.mSandboxBroker->LaunchApp(
+        mCmdLine->program().c_str(), mCmdLine->command_line_string().c_str(),
+        mLaunchOptions->env_map, mProcessType, mEnableSandboxLogging,
+        cachedNtdllThunk, &handle);
+    if (err.isOk()) {
+      EnvironmentLog("MOZ_PROCESS_LOG")
+          .print("==> process %d launched child process %d (%S)\n",
+                 base::GetCurrentProcId(), base::GetProcId(handle),
+                 mCmdLine->command_line_string().c_str());
+      return ProcessHandlePromise::CreateAndResolve(handle, __func__);
+    }
+    return ProcessHandlePromise::CreateAndReject(err.unwrapErr(), __func__);
+  }
+#  endif  // defined(MOZ_SANDBOX)
+
+  Result<Ok, LaunchError> launchErr =
+      base::LaunchApp(mCmdLine.ref(), *mLaunchOptions, &handle);
+  if (launchErr.isErr()) {
+    return ProcessHandlePromise::CreateAndReject(launchErr.unwrapErr(),
+                                                 __func__);
+  }
+  return ProcessHandlePromise::CreateAndResolve(handle, __func__);
+}
+
+Result<Ok, LaunchError> WindowsProcessLauncher::DoFinishLaunch() {
+  Result<Ok, LaunchError> err = BaseProcessLauncher::DoFinishLaunch();
+  if (err.isErr()) {
+    return err;
+  }
+
+#  ifdef MOZ_SANDBOX
+  if (!mUseSandbox) {
+    // We need to be able to duplicate handles to some types of non-sandboxed
+    // child processes.
+    switch (mProcessType) {
+      case GeckoProcessType_Default:
+        MOZ_CRASH("shouldn't be launching a parent process");
+      case GeckoProcessType_IPDLUnitTest:
+        // No handle duplication necessary.
+        break;
+      default:
+        if (!SandboxBroker::AddTargetPeer(mResults.mHandle)) {
+          NS_WARNING("Failed to add child process as target peer.");
+        }
+        break;
+    }
+  }
+#  endif  // MOZ_SANDBOX
+
+  return Ok();
+}
+#endif  // XP_WIN
+
+RefPtr<ProcessLaunchPromise> BaseProcessLauncher::FinishLaunch() {
+  Result<Ok, LaunchError> aError = DoFinishLaunch();
+  if (aError.isErr()) {
+    return ProcessLaunchPromise::CreateAndReject(aError.unwrapErr(), __func__);
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(mResults.mHandle);
+
+  CrashReporter::RegisterChildCrashAnnotationFileDescriptor(
+      base::GetProcId(mResults.mHandle), mCrashAnnotationReadPipe.forget());
+
+  Telemetry::AccumulateTimeDelta(Telemetry::CHILD_PROCESS_LAUNCH_MS,
+                                 mStartTimeStamp);
+
+  return ProcessLaunchPromise::CreateAndResolve(mResults, __func__);
+}
+
+bool GeckoChildProcessHost::OpenPrivilegedHandle(base::ProcessId aPid) {
+  if (mChildProcessHandle) {
+    MOZ_ASSERT(aPid == base::GetProcId(mChildProcessHandle));
+    return true;
+  }
+
+  return base::OpenPrivilegedProcessHandle(aPid, &mChildProcessHandle);
+}
+
+void GeckoChildProcessHost::OnChannelConnected(base::ProcessId peer_pid) {
+  {
+    mozilla::AutoWriteLock hLock(mHandleLock);
+    if (!OpenPrivilegedHandle(peer_pid)) {
+      MOZ_CRASH("can't open handle to child process");
+    }
+  }
+  MonitorAutoLock lock(mMonitor);
+  mProcessState = PROCESS_CONNECTED;
+  lock.Notify();
+}
+
+void GeckoChildProcessHost::OnMessageReceived(UniquePtr<IPC::Message> aMsg) {
+  // We never process messages ourself, just save them up for the next
+  // listener.
+  mQueue.push(std::move(aMsg));
+}
+
+void GeckoChildProcessHost::OnChannelError() {
+  // Update the process state to an error state if we have a channel
+  // error before we're connected. This fixes certain failures,
+  // but does not address the full range of possible issues described
+  // in the FIXME comment below.
+  MonitorAutoLock lock(mMonitor);
+  if (mProcessState < PROCESS_CONNECTED) {
+    mProcessState = PROCESS_ERROR;
+    lock.Notify();
+  }
+  // FIXME/bug 773925: save up this error for the next listener.
+}
+
+RefPtr<ProcessHandlePromise> GeckoChildProcessHost::WhenProcessHandleReady() {
+  MOZ_ASSERT(mHandlePromise != nullptr);
+  return mHandlePromise;
+}
+
+void GeckoChildProcessHost::GetQueuedMessages(
+    std::queue<UniquePtr<IPC::Message>>& queue) {
+  // If this is called off the IO thread, bad things will happen.
+  DCHECK(MessageLoopForIO::current());
+  swap(queue, mQueue);
+  // We expect the next listener to take over processing of our queue.
+}
+
+#ifdef MOZ_WIDGET_ANDROID
+RefPtr<ProcessHandlePromise> AndroidProcessLauncher::LaunchAndroidService(
+    const GeckoProcessType aType, const std::vector<std::string>& argv,
+    const base::file_handle_mapping_vector& fds_to_remap) {
+  MOZ_RELEASE_ASSERT((2 <= fds_to_remap.size()) && (fds_to_remap.size() <= 5));
+  JNIEnv* const env = mozilla::jni::GetEnvForThread();
+  MOZ_ASSERT(env);
+
+  const int argvSize = argv.size();
+  jni::ObjectArray::LocalRef jargs =
+      jni::ObjectArray::New<jni::String>(argvSize);
+  for (int ix = 0; ix < argvSize; ix++) {
+    jargs->SetElement(ix, jni::StringParam(argv[ix].c_str(), env));
+  }
+
+  // XXX: this processing depends entirely on the internals of
+  // ContentParent::LaunchSubprocess()
+  // GeckoChildProcessHost::PerformAsyncLaunch(), and the order in
+  // which they append to fds_to_remap. There must be a better way to do it.
+  // See bug 1440207.
+  int32_t prefsFd = fds_to_remap[0].first;
+  int32_t prefMapFd = fds_to_remap[1].first;
+  int32_t ipcFd = fds_to_remap[2].first;
+  int32_t crashFd = -1;
+  int32_t crashAnnotationFd = -1;
+  if (fds_to_remap.size() == 4) {
+    crashAnnotationFd = fds_to_remap[3].first;
+  }
+  if (fds_to_remap.size() == 5) {
+    crashFd = fds_to_remap[3].first;
+    crashAnnotationFd = fds_to_remap[4].first;
+  }
+
+  auto type = java::GeckoProcessType::FromInt(aType);
+  auto genericResult = java::GeckoProcessManager::Start(
+      type, jargs, prefsFd, prefMapFd, ipcFd, crashFd, crashAnnotationFd);
+  auto typedResult = java::GeckoResult::LocalRef(std::move(genericResult));
+  return ProcessHandlePromise::FromGeckoResult(typedResult);
+}
+#endif
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+bool GeckoChildProcessHost::AppendMacSandboxParams(StringVector& aArgs) {
+  MacSandboxInfo info;
+  if (NS_WARN_IF(!FillMacSandboxInfo(info))) {
+    return false;
+  }
+  info.AppendAsParams(aArgs);
+  return true;
+}
+
+// Fill |aInfo| with the flags needed to launch the utility sandbox
+bool GeckoChildProcessHost::FillMacSandboxInfo(MacSandboxInfo& aInfo) {
+  aInfo.type = GetDefaultMacSandboxType();
+  aInfo.shouldLog = Preferences::GetBool("security.sandbox.logging.enabled") ||
+                    PR_GetEnv("MOZ_SANDBOX_LOGGING");
+
+  nsAutoCString appPath;
+  if (!nsMacUtilsImpl::GetAppPath(appPath)) {
+    MOZ_CRASH("Failed to get app path");
+  }
+  aInfo.appPath.assign(appPath.get());
+  return true;
+}
+
+void GeckoChildProcessHost::DisableOSActivityMode() {
+  mDisableOSActivityMode = true;
+}
+
+//
+// If early sandbox startup is enabled for this process type, map the
+// process type to the sandbox type and enable the sandbox. Returns true
+// if no errors were encountered or if early sandbox startup is not
+// enabled for this process. Returns false if an error was encountered.
+//
+/* static */
+bool GeckoChildProcessHost::StartMacSandbox(int aArgc, char** aArgv,
+                                            std::string& aErrorMessage) {
+  MacSandboxType sandboxType = MacSandboxType_Invalid;
+  switch (XRE_GetProcessType()) {
+    // For now, only support early sandbox startup for content,
+    // RDD, and GMP processes. Add case statements for the additional
+    // process types once early sandbox startup is implemented for them.
+    case GeckoProcessType_Content:
+      // Content processes don't use GeckoChildProcessHost
+      // to configure sandboxing so hard code the sandbox type.
+      sandboxType = MacSandboxType_Content;
+      break;
+    case GeckoProcessType_RDD:
+      sandboxType = RDDProcessHost::GetMacSandboxType();
+      break;
+    case GeckoProcessType_Socket:
+      sandboxType = net::SocketProcessHost::GetMacSandboxType();
+      break;
+    case GeckoProcessType_GMPlugin:
+      sandboxType = gmp::GMPProcessParent::GetMacSandboxType();
+      break;
+    case GeckoProcessType_Utility:
+      sandboxType = ipc::UtilityProcessHost::GetMacSandboxType();
+      break;
+    default:
+      return true;
+  }
+
+  return mozilla::StartMacSandboxIfEnabled(sandboxType, aArgc, aArgv,
+                                           aErrorMessage);
+}
+
+#endif /* XP_MACOSX && MOZ_SANDBOX */
+
+/* static */
+void GeckoChildProcessHost::GetAll(const GeckoProcessCallback& aCallback) {
+  StaticMutexAutoLock lock(sMutex);
+  if (!sGeckoChildProcessHosts) {
+    return;
+  }
+  for (GeckoChildProcessHost* gp = sGeckoChildProcessHosts->getFirst(); gp;
+       gp = static_cast<mozilla::LinkedListElement<GeckoChildProcessHost>*>(gp)
+                ->getNext()) {
+    aCallback(gp);
+  }
+}
+
+RefPtr<ProcessLaunchPromise> BaseProcessLauncher::Launch(
+    GeckoChildProcessHost* aHost) {
+  AssertIOThread();
+
+  // The ForkServer doesn't use IPC::Channel for communication, so we can skip
+  // initializing it.
+  if (mProcessType != GeckoProcessType_ForkServer) {
+    // Initializing the channel needs to happen on the I/O thread, but
+    // everything else can run on the launcher thread (or pool), to avoid
+    // blocking IPC messages.
+    //
+    // We avoid passing the host to the launcher thread to reduce the chances of
+    // data races with the IO thread (where e.g. OnChannelConnected may run
+    // concurrently). The pool currently needs access to the channel, which is
+    // not great.
+    bool failed = false;
+    aHost->InitializeChannel([&](IPC::Channel* channel) {
+      if (NS_WARN_IF(!channel || !SetChannel(channel))) {
+        failed = true;
+      }
+    });
+    if (failed) {
+      return ProcessLaunchPromise::CreateAndReject(LaunchError("SetChannel"),
+                                                   __func__);
+    }
+    mChannelId = aHost->GetChannelId();
+  }
+
+  return InvokeAsync(mLaunchThread, this, __func__,
+                     &BaseProcessLauncher::PerformAsyncLaunch);
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/GeckoChildProcessHost.h b/ipc/glue/GeckoChildProcessHost.h
new file mode 100644
index 0000000000..ccf8a4aca4
--- /dev/null
+++ b/ipc/glue/GeckoChildProcessHost.h
@@ -0,0 +1,335 @@
+/* -*- 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 __IPC_GLUE_GECKOCHILDPROCESSHOST_H__
+#define __IPC_GLUE_GECKOCHILDPROCESSHOST_H__
+
+#include "base/file_path.h"
+#include "base/process_util.h"
+#include "base/waitable_event.h"
+#include "chrome/common/child_process_host.h"
+#include "chrome/common/ipc_message.h"
+#include "mojo/core/ports/port_ref.h"
+
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/FileDescriptor.h"
+#include "mozilla/ipc/NodeChannel.h"
+#include "mozilla/ipc/LaunchError.h"
+#include "mozilla/ipc/ScopedPort.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Buffer.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/RWLock.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/UniquePtr.h"
+
+#include "nsCOMPtr.h"
+#include "nsExceptionHandler.h"
+#include "nsXULAppAPI.h"  // for GeckoProcessType
+#include "nsString.h"
+
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+#  include "sandboxBroker.h"
+#endif
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+#  include "mozilla/Sandbox.h"
+#endif
+
+#if defined(MOZ_SANDBOX)
+#  include "mozilla/ipc/UtilityProcessSandboxing.h"
+#endif
+
+#if (defined(XP_WIN) && defined(_ARM64_)) || \
+    (defined(XP_MACOSX) && defined(__aarch64__))
+#  define ALLOW_GECKO_CHILD_PROCESS_ARCH
+#endif
+
+struct _MacSandboxInfo;
+typedef _MacSandboxInfo MacSandboxInfo;
+
+namespace mozilla {
+namespace ipc {
+
+typedef mozilla::MozPromise<base::ProcessHandle, LaunchError, false>
+    ProcessHandlePromise;
+
+class GeckoChildProcessHost : public ChildProcessHost,
+                              public LinkedListElement<GeckoChildProcessHost> {
+ protected:
+  typedef mozilla::Monitor Monitor;
+  typedef std::vector<std::string> StringVector;
+
+ public:
+  using ProcessId = base::ProcessId;
+  using ProcessHandle = base::ProcessHandle;
+
+  explicit GeckoChildProcessHost(GeckoProcessType aProcessType,
+                                 bool aIsFileContent = false);
+
+  // Causes the object to be deleted, on the I/O thread, after any
+  // pending asynchronous work (like launching) is complete.  This
+  // method can be called from any thread.  If called from the I/O
+  // thread itself, deletion won't happen until the event loop spins;
+  // otherwise, it could happen immediately.
+  //
+  // GeckoChildProcessHost instances must not be deleted except
+  // through this method.
+  void Destroy();
+
+  static uint32_t GetUniqueID();
+
+  // Call this before launching to set an environment variable for the
+  // child process.  The arguments must be UTF-8.
+  void SetEnv(const char* aKey, const char* aValue);
+
+  // Does not block.  The IPC channel may not be initialized yet, and
+  // the child process may or may not have been created when this
+  // method returns.
+  bool AsyncLaunch(StringVector aExtraOpts = StringVector());
+
+  virtual bool WaitUntilConnected(int32_t aTimeoutMs = 0);
+
+  // Block until the IPC channel for our subprocess is initialized and
+  // the OS process is created.  The subprocess may or may not have
+  // connected back to us when this method returns.
+  //
+  // NB: on POSIX, this method is relatively cheap, and doesn't
+  // require disk IO.  On win32 however, it requires at least the
+  // analogue of stat().  This difference induces a semantic
+  // difference in this method: on POSIX, when we return, we know the
+  // subprocess has been created, but we don't know whether its
+  // executable image can be loaded.  On win32, we do know that when
+  // we return.  But we don't know if dynamic linking succeeded on
+  // either platform.
+  bool LaunchAndWaitForProcessHandle(StringVector aExtraOpts = StringVector());
+  bool WaitForProcessHandle();
+
+  // Block until the child process has been created and it connects to
+  // the IPC channel, meaning it's fully initialized.  (Or until an
+  // error occurs.)
+  bool SyncLaunch(StringVector aExtraOpts = StringVector(),
+                  int32_t timeoutMs = 0);
+
+  virtual void OnChannelConnected(base::ProcessId peer_pid) override;
+  virtual void OnMessageReceived(UniquePtr<IPC::Message> aMsg) override;
+  virtual void OnChannelError() override;
+  virtual void GetQueuedMessages(
+      std::queue<UniquePtr<IPC::Message>>& queue) override;
+
+  // Resolves to the process handle when it's available (see
+  // LaunchAndWaitForProcessHandle); use with AsyncLaunch.
+  RefPtr<ProcessHandlePromise> WhenProcessHandleReady();
+
+  void InitializeChannel(
+      const std::function<void(IPC::Channel*)>& aChannelReady);
+
+  virtual bool CanShutdown() override { return true; }
+
+  IPC::Channel* GetChannel() { return channelp(); }
+  ChannelId GetChannelId() { return channel_id(); }
+
+  UntypedEndpoint TakeInitialEndpoint() {
+    return UntypedEndpoint{PrivateIPDLInterface{}, std::move(mInitialPort),
+                           mInitialChannelId, base::GetCurrentProcId(),
+                           GetChildProcessId()};
+  }
+
+  // Returns a "borrowed" handle to the child process - the handle returned
+  // by this function must not be closed by the caller.  The handle is also
+  // not guaranteed to remain valid; if the caller is using it for anything
+  // more than logging or asserting non-null, it will need to deal with
+  // synchronization.
+  //
+  // Warning: the null value here is 0, not kInvalidProcessHandle.
+  ProcessHandle GetChildProcessHandle();
+
+  // Returns the child's process ID; as for GetChildProcessHandle, there is
+  // no inherent guarantee that it will remain valid or continue to
+  // reference the same process.
+  //
+  // The null value here is also 0; this matches the result of
+  // GetProcId on a zero or (on Windows) invalid handle.
+  ProcessId GetChildProcessId();
+
+  GeckoProcessType GetProcessType() { return mProcessType; }
+
+#ifdef XP_MACOSX
+  task_t GetChildTask();
+#endif
+
+#ifdef XP_WIN
+
+  void AddHandleToShare(HANDLE aHandle) {
+    mLaunchOptions->handles_to_inherit.push_back(aHandle);
+  }
+#else
+  void AddFdToRemap(int aSrcFd, int aDstFd) {
+    mLaunchOptions->fds_to_remap.push_back(std::make_pair(aSrcFd, aDstFd));
+  }
+#endif
+
+#ifdef ALLOW_GECKO_CHILD_PROCESS_ARCH
+  void SetLaunchArchitecture(uint32_t aArch) { mLaunchArch = aArch; }
+#endif
+
+  // For bug 943174: Skip the EnsureProcessTerminated call in the destructor.
+  void SetAlreadyDead();
+
+#if defined(MOZ_SANDBOX) && defined(XP_MACOSX)
+  // Start the sandbox from the child process.
+  static bool StartMacSandbox(int aArgc, char** aArgv,
+                              std::string& aErrorMessage);
+
+  // The sandbox type that will be use when sandboxing is
+  // enabled in the derived class and FillMacSandboxInfo
+  // has not been overridden.
+  static MacSandboxType GetDefaultMacSandboxType() {
+    return MacSandboxType_Utility;
+  };
+
+  // Must be called before the process is launched. Determines if
+  // child processes will be launched with OS_ACTIVITY_MODE set to
+  // "disabled" or not. When |mDisableOSActivityMode| is set to true,
+  // child processes will be launched with OS_ACTIVITY_MODE
+  // disabled to avoid connection attempts to diagnosticd(8) which are
+  // blocked in child processes due to sandboxing.
+  void DisableOSActivityMode();
+#endif  // defined(MOZ_SANDBOX) && defined(XP_MACOSX)
+  typedef std::function<void(GeckoChildProcessHost*)> GeckoProcessCallback;
+
+  // Iterates over all instances and calls aCallback with each one of them.
+  // This method will lock any addition/removal of new processes
+  // so you need to make sure the callback is as fast as possible.
+  //
+  // To reiterate: the callbacks are executed synchronously.
+  static void GetAll(const GeckoProcessCallback& aCallback);
+
+  friend class BaseProcessLauncher;
+  friend class PosixProcessLauncher;
+  friend class WindowsProcessLauncher;
+
+ protected:
+  ~GeckoChildProcessHost();
+  GeckoProcessType mProcessType;
+  bool mIsFileContent;
+  Monitor mMonitor;
+  FilePath mProcessPath;
+#ifdef ALLOW_GECKO_CHILD_PROCESS_ARCH
+  // Used on platforms where we may launch a child process with a different
+  // architecture than the parent process.
+  uint32_t mLaunchArch = base::PROCESS_ARCH_INVALID;
+#endif
+  // GeckoChildProcessHost holds the launch options so they can be set
+  // up on the main thread using main-thread-only APIs like prefs, and
+  // then used for the actual launch on another thread.  This pointer
+  // is set to null to free the options after the child is launched.
+  UniquePtr<base::LaunchOptions> mLaunchOptions;
+  ScopedPort mInitialPort;
+  nsID mInitialChannelId;
+  RefPtr<NodeController> mNodeController;
+  RefPtr<NodeChannel> mNodeChannel;
+
+  // This value must be accessed while holding mMonitor.
+  enum {
+    // This object has been constructed, but the OS process has not
+    // yet.
+    CREATING_CHANNEL = 0,
+    // The IPC channel for our subprocess has been created, but the OS
+    // process has still not been created.
+    CHANNEL_INITIALIZED,
+    // The OS process has been created, but it hasn't yet connected to
+    // our IPC channel.
+    PROCESS_CREATED,
+    // The process is launched and connected to our IPC channel.  All
+    // is well.
+    PROCESS_CONNECTED,
+    PROCESS_ERROR
+  } mProcessState MOZ_GUARDED_BY(mMonitor);
+
+  void PrepareLaunch();
+
+#ifdef XP_WIN
+  void InitWindowsGroupID();
+  nsString mGroupId;
+  CrashReporter::WindowsErrorReportingData mWerData;
+#  ifdef MOZ_SANDBOX
+  RefPtr<AbstractSandboxBroker> mSandboxBroker;
+  std::vector<std::wstring> mAllowedFilesRead;
+  bool mEnableSandboxLogging;
+  int32_t mSandboxLevel;
+#  endif
+#endif  // XP_WIN
+
+#if defined(MOZ_SANDBOX)
+  SandboxingKind mSandbox;
+#endif
+
+  mozilla::RWLock mHandleLock;
+  ProcessHandle mChildProcessHandle MOZ_GUARDED_BY(mHandleLock);
+#if defined(OS_MACOSX)
+  task_t mChildTask MOZ_GUARDED_BY(mHandleLock);
+#endif
+  RefPtr<ProcessHandlePromise> mHandlePromise;
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  bool mDisableOSActivityMode;
+#endif
+
+  bool OpenPrivilegedHandle(base::ProcessId aPid) MOZ_REQUIRES(mHandleLock);
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  // Override this method to return true to launch the child process
+  // using the Mac utility (by default) sandbox. Override
+  // FillMacSandboxInfo() to change the sandbox type and settings.
+  virtual bool IsMacSandboxLaunchEnabled() { return false; }
+
+  // Fill a MacSandboxInfo to configure the sandbox
+  virtual bool FillMacSandboxInfo(MacSandboxInfo& aInfo);
+
+  // Adds the command line arguments needed to enable
+  // sandboxing of the child process at startup before
+  // the child event loop is up.
+  virtual bool AppendMacSandboxParams(StringVector& aArgs);
+#endif
+
+ private:
+  DISALLOW_EVIL_CONSTRUCTORS(GeckoChildProcessHost);
+
+  // Removes the instance from sGeckoChildProcessHosts
+  void RemoveFromProcessList();
+
+  // In between launching the subprocess and handing off its IPC
+  // channel, there's a small window of time in which *we* might still
+  // be the channel listener, and receive messages.  That's bad
+  // because we have no idea what to do with those messages.  So queue
+  // them here until we hand off the eventual listener.
+  //
+  // FIXME/cjones: this strongly indicates bad design.  Shame on us.
+  std::queue<UniquePtr<IPC::Message>> mQueue;
+
+  // Linux-Only. Set this up before we're called from a different thread.
+  nsCString mTmpDirName;
+  // Mac and Windows. Set this up before we're called from a different thread.
+  nsCOMPtr<nsIFile> mProfileDir;
+
+  mozilla::Atomic<bool> mDestroying;
+
+  static uint32_t sNextUniqueID;
+  static StaticAutoPtr<LinkedList<GeckoChildProcessHost>>
+      sGeckoChildProcessHosts MOZ_GUARDED_BY(sMutex);
+  static StaticMutex sMutex;
+};
+
+nsCOMPtr<nsIEventTarget> GetIPCLauncher();
+
+} /* namespace ipc */
+} /* namespace mozilla */
+
+#endif /* __IPC_GLUE_GECKOCHILDPROCESSHOST_H__ */
diff --git a/ipc/glue/IOThreadChild.h b/ipc/glue/IOThreadChild.h
new file mode 100644
index 0000000000..632389bf08
--- /dev/null
+++ b/ipc/glue/IOThreadChild.h
@@ -0,0 +1,46 @@
+/* -*- 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 dom_plugins_IOThreadChild_h
+#define dom_plugins_IOThreadChild_h
+
+#include "chrome/common/child_thread.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/NodeController.h"
+#include "mozilla/ipc/ProcessChild.h"
+
+namespace mozilla {
+namespace ipc {
+//-----------------------------------------------------------------------------
+
+// The IOThreadChild class represents a background thread where the
+// IPC IO MessageLoop lives.
+class IOThreadChild : public ChildThread {
+ public:
+  IOThreadChild()
+      : ChildThread(base::Thread::Options(MessageLoop::TYPE_IO,
+                                          0))  // stack size
+  {}
+
+  ~IOThreadChild() = default;
+
+  static MessageLoop* message_loop() {
+    return IOThreadChild::current()->Thread::message_loop();
+  }
+
+ protected:
+  static IOThreadChild* current() {
+    return static_cast<IOThreadChild*>(ChildThread::current());
+  }
+
+ private:
+  DISALLOW_EVIL_CONSTRUCTORS(IOThreadChild);
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef dom_plugins_IOThreadChild_h
diff --git a/ipc/glue/IPCCore.h b/ipc/glue/IPCCore.h
new file mode 100644
index 0000000000..bb6b725c35
--- /dev/null
+++ b/ipc/glue/IPCCore.h
@@ -0,0 +1,22 @@
+/* -*- 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 IPC_GLUE_IPCCORE_H_
+#define IPC_GLUE_IPCCORE_H_
+
+namespace mozilla {
+
+struct void_t {
+  constexpr bool operator==(const void_t&) const { return true; }
+};
+
+struct null_t {
+  constexpr bool operator==(const null_t&) const { return true; }
+};
+
+}  // namespace mozilla
+
+#endif  // IPC_GLUE_IPCCORE_H_
diff --git a/ipc/glue/IPCForwards.h b/ipc/glue/IPCForwards.h
new file mode 100644
index 0000000000..8aef885257
--- /dev/null
+++ b/ipc/glue/IPCForwards.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_ipc_IPCForwards_h
+#define mozilla_ipc_IPCForwards_h
+
+// A few helpers to avoid having to include lots of stuff in headers.
+
+namespace mozilla {
+template <typename T>
+class Maybe;
+
+namespace ipc {
+class IProtocol;
+}
+}  // namespace mozilla
+
+namespace IPC {
+class Message;
+class MessageReader;
+class MessageWriter;
+template <typename T, bool>
+class ReadResult;
+}  // namespace IPC
+
+// TODO(bug 1812271): Remove users of this macro.
+#define ALLOW_DEPRECATED_READPARAM                           \
+ public:                                                     \
+  enum { kHasDeprecatedReadParamPrivateConstructor = true }; \
+  template <typename, bool>                                  \
+  friend class IPC::ReadResult;                              \
+                                                             \
+ private:
+
+#endif
diff --git a/ipc/glue/IPCMessageUtils.h b/ipc/glue/IPCMessageUtils.h
new file mode 100644
index 0000000000..ab9b84e3ea
--- /dev/null
+++ b/ipc/glue/IPCMessageUtils.h
@@ -0,0 +1,238 @@
+/* -*- 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 __IPC_GLUE_IPCMESSAGEUTILS_H__
+#define __IPC_GLUE_IPCMESSAGEUTILS_H__
+
+#include <cstdint>
+#include <string>
+#include <type_traits>
+#include "build/build_config.h"
+#include "chrome/common/ipc_message.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "mozilla/ipc/IPCCore.h"
+#include "mozilla/MacroForEach.h"
+
+class PickleIterator;
+
+// XXX Things that are not necessary if moving implementations to the cpp file
+#include "base/string_util.h"
+
+#ifdef _MSC_VER
+#  pragma warning(disable : 4800)
+#endif
+
+#if !defined(OS_POSIX)
+// This condition must be kept in sync with the one in
+// ipc_message_utils.h, but this dummy definition of
+// base::FileDescriptor acts as a static assert that we only get one
+// def or the other (or neither, in which case code using
+// FileDescriptor fails to build)
+namespace base {
+struct FileDescriptor {};
+}  // namespace base
+#endif
+
+namespace mozilla {
+template <typename...>
+class Variant;
+
+namespace detail {
+template <typename...>
+struct VariantTag;
+}
+}  // namespace mozilla
+
+namespace IPC {
+
+/**
+ * A helper class for serializing plain-old data (POD) structures.
+ * The memory representation of the structure is written to and read from
+ * the serialized stream directly, without individual processing of the
+ * structure's members.
+ *
+ * Derive ParamTraits<T> from PlainOldDataSerializer<T> if T is POD.
+ *
+ * Note: For POD structures with enumeration fields, this will not do
+ *   validation of the enum values the way serializing the fields
+ *   individually would. Prefer serializing the fields individually
+ *   in such cases.
+ */
+template <typename T>
+struct PlainOldDataSerializer {
+  static_assert(
+      std::is_trivially_copyable<T>::value,
+      "PlainOldDataSerializer can only be used with trivially copyable types!");
+
+  typedef T paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteBytes(&aParam, sizeof(aParam));
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return aReader->ReadBytesInto(aResult, sizeof(paramType));
+  }
+};
+
+/**
+ * A helper class for serializing empty structs. Since the struct is empty there
+ * is nothing to write, and a priori we know the result of the read.
+ */
+template <typename T>
+struct EmptyStructSerializer {
+  typedef T paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {}
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    *aResult = {};
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<int8_t> {
+  typedef int8_t paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteBytes(&aParam, sizeof(aParam));
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return aReader->ReadBytesInto(aResult, sizeof(*aResult));
+  }
+};
+
+template <>
+struct ParamTraits<uint8_t> {
+  typedef uint8_t paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteBytes(&aParam, sizeof(aParam));
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return aReader->ReadBytesInto(aResult, sizeof(*aResult));
+  }
+};
+
+#if !defined(OS_POSIX)
+// See above re: keeping definitions in sync
+template <>
+struct ParamTraits<base::FileDescriptor> {
+  typedef base::FileDescriptor paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    MOZ_CRASH("FileDescriptor isn't meaningful on this platform");
+  }
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    MOZ_CRASH("FileDescriptor isn't meaningful on this platform");
+    return false;
+  }
+};
+#endif  // !defined(OS_POSIX)
+
+template <>
+struct ParamTraits<mozilla::void_t> {
+  typedef mozilla::void_t paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {}
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    *aResult = paramType();
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::null_t> {
+  typedef mozilla::null_t paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {}
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    *aResult = paramType();
+    return true;
+  }
+};
+
+// Helper class for reading bitfields.
+// If T has bitfields members, derive ParamTraits<T> from BitfieldHelper<T>.
+template <typename ParamType>
+struct BitfieldHelper {
+  // We need this helper because we can't get the address of a bitfield to
+  // pass directly to ReadParam. So instead we read it into a temporary bool
+  // and set the bitfield using a setter function
+  static bool ReadBoolForBitfield(MessageReader* aReader, ParamType* aResult,
+                                  void (ParamType::*aSetter)(bool)) {
+    bool value;
+    if (ReadParam(aReader, &value)) {
+      (aResult->*aSetter)(value);
+      return true;
+    }
+    return false;
+  }
+};
+
+// A couple of recursive helper functions, allows syntax like:
+// WriteParams(aMsg, aParam.foo, aParam.bar, aParam.baz)
+// ReadParams(aMsg, aIter, aParam.foo, aParam.bar, aParam.baz)
+
+template <typename... Ts>
+static void WriteParams(MessageWriter* aWriter, const Ts&... aArgs) {
+  (WriteParam(aWriter, aArgs), ...);
+}
+
+template <typename... Ts>
+static bool ReadParams(MessageReader* aReader, Ts&... aArgs) {
+  return (ReadParam(aReader, &aArgs) && ...);
+}
+
+// Macros that allow syntax like:
+// DEFINE_IPC_SERIALIZER_WITH_FIELDS(SomeType, member1, member2, member3)
+// Makes sure that serialize/deserialize code do the same members in the same
+// order.
+#define ACCESS_PARAM_FIELD(Field) aParam.Field
+
+#define DEFINE_IPC_SERIALIZER_WITH_FIELDS(Type, ...)                         \
+  template <>                                                                \
+  struct ParamTraits<Type> {                                                 \
+    typedef Type paramType;                                                  \
+    static void Write(MessageWriter* aWriter, const paramType& aParam) {     \
+      WriteParams(aWriter, MOZ_FOR_EACH_SEPARATED(ACCESS_PARAM_FIELD, (, ),  \
+                                                  (), (__VA_ARGS__)));       \
+    }                                                                        \
+                                                                             \
+    static bool Read(MessageReader* aReader, paramType* aResult) {           \
+      paramType& aParam = *aResult;                                          \
+      return ReadParams(aReader,                                             \
+                        MOZ_FOR_EACH_SEPARATED(ACCESS_PARAM_FIELD, (, ), (), \
+                                               (__VA_ARGS__)));              \
+    }                                                                        \
+  };
+
+#define DEFINE_IPC_SERIALIZER_WITHOUT_FIELDS(Type) \
+  template <>                                      \
+  struct ParamTraits<Type> : public EmptyStructSerializer<Type> {};
+
+} /* namespace IPC */
+
+#define DEFINE_IPC_SERIALIZER_WITH_SUPER_CLASS_AND_FIELDS(Type, Super, ...)  \
+  template <>                                                                \
+  struct ParamTraits<Type> {                                                 \
+    typedef Type paramType;                                                  \
+    static void Write(MessageWriter* aWriter, const paramType& aParam) {     \
+      WriteParam(aWriter, static_cast<const Super&>(aParam));                \
+      WriteParams(aWriter, MOZ_FOR_EACH_SEPARATED(ACCESS_PARAM_FIELD, (, ),  \
+                                                  (), (__VA_ARGS__)));       \
+    }                                                                        \
+                                                                             \
+    static bool Read(MessageReader* aReader, paramType* aResult) {           \
+      paramType& aParam = *aResult;                                          \
+      return ReadParam(aReader, static_cast<Super*>(aResult)) &&             \
+             ReadParams(aReader,                                             \
+                        MOZ_FOR_EACH_SEPARATED(ACCESS_PARAM_FIELD, (, ), (), \
+                                               (__VA_ARGS__)));              \
+    }                                                                        \
+  };
+
+#endif /* __IPC_GLUE_IPCMESSAGEUTILS_H__ */
diff --git a/ipc/glue/IPCMessageUtilsSpecializations.cpp b/ipc/glue/IPCMessageUtilsSpecializations.cpp
new file mode 100644
index 0000000000..410b1e730f
--- /dev/null
+++ b/ipc/glue/IPCMessageUtilsSpecializations.cpp
@@ -0,0 +1,67 @@
+/* -*- 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 "IPCMessageUtilsSpecializations.h"
+#include "nsGkAtoms.h"
+
+namespace IPC {
+
+static const uint16_t kDynamicAtomToken = 0xffff;
+static const uint16_t kAtomsCount =
+    static_cast<uint16_t>(mozilla::detail::GkAtoms::Atoms::AtomsCount);
+
+static_assert(static_cast<size_t>(
+                  mozilla::detail::GkAtoms::Atoms::AtomsCount) == kAtomsCount,
+              "Number of static atoms must fit in a uint16_t");
+
+static_assert(kDynamicAtomToken >= kAtomsCount,
+              "Exceeded supported number of static atoms");
+
+/* static */
+void ParamTraits<nsAtom*>::Write(MessageWriter* aWriter, const nsAtom* aParam) {
+  MOZ_ASSERT(aParam);
+
+  if (aParam->IsStatic()) {
+    const nsStaticAtom* atom = aParam->AsStatic();
+    uint16_t index = static_cast<uint16_t>(nsGkAtoms::IndexOf(atom));
+    MOZ_ASSERT(index < kAtomsCount);
+    WriteParam(aWriter, index);
+    return;
+  }
+  WriteParam(aWriter, kDynamicAtomToken);
+  nsDependentAtomString atomStr(aParam);
+  // nsDependentAtomString is serialized as its base, nsString, but we
+  // can be explicit about it.
+  nsString& str = atomStr;
+  WriteParam(aWriter, str);
+}
+
+/* static */
+bool ParamTraits<nsAtom*>::Read(MessageReader* aReader,
+                                RefPtr<nsAtom>* aResult) {
+  uint16_t token;
+  if (!ReadParam(aReader, &token)) {
+    return false;
+  }
+  if (token != kDynamicAtomToken) {
+    if (token >= kAtomsCount) {
+      return false;
+    }
+    *aResult = nsGkAtoms::GetAtomByIndex(token);
+    return true;
+  }
+
+  nsAutoString str;
+  if (!ReadParam(aReader, static_cast<nsString*>(&str))) {
+    return false;
+  }
+
+  *aResult = NS_Atomize(str);
+  MOZ_ASSERT(*aResult);
+  return true;
+}
+
+}  // namespace IPC
diff --git a/ipc/glue/IPCMessageUtilsSpecializations.h b/ipc/glue/IPCMessageUtilsSpecializations.h
new file mode 100644
index 0000000000..4f357405d9
--- /dev/null
+++ b/ipc/glue/IPCMessageUtilsSpecializations.h
@@ -0,0 +1,802 @@
+/* -*- 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 __IPC_GLUE_IPCMESSAGEUTILSSPECIALIZATIONS_H__
+#define __IPC_GLUE_IPCMESSAGEUTILSSPECIALIZATIONS_H__
+
+#include <cstdint>
+#include <cstdlib>
+#include <limits>
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+#include "chrome/common/ipc_message.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "ipc/EnumSerializer.h"
+#include "ipc/IPCMessageUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/BitSet.h"
+#include "mozilla/EnumSet.h"
+#include "mozilla/EnumTypeTraits.h"
+#include "mozilla/IntegerRange.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+#ifdef XP_WIN
+#  include "mozilla/TimeStamp_windows.h"
+#endif
+
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Vector.h"
+#include "mozilla/dom/ipc/StructuredCloneData.h"
+#include "nsCSSPropertyID.h"
+#include "nsDebug.h"
+#include "nsIContentPolicy.h"
+#include "nsID.h"
+#include "nsILoadInfo.h"
+#include "nsIThread.h"
+#include "nsLiteralString.h"
+#include "nsNetUtil.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "nsTHashSet.h"
+
+// XXX Includes that are only required by implementations which could be moved
+// to the cpp file.
+#include "base/string_util.h"    // for StringPrintf
+#include "mozilla/ArrayUtils.h"  // for ArrayLength
+#include "mozilla/CheckedInt.h"
+
+#ifdef _MSC_VER
+#  pragma warning(disable : 4800)
+#endif
+
+namespace mozilla {
+template <typename... Ts>
+class Variant;
+
+namespace detail {
+template <typename... Ts>
+struct VariantTag;
+}
+}  // namespace mozilla
+
+namespace mozilla::dom {
+template <typename T>
+class Optional;
+}
+
+class nsAtom;
+
+namespace IPC {
+
+template <class T>
+struct ParamTraits<nsTSubstring<T>> {
+  typedef nsTSubstring<T> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    bool isVoid = aParam.IsVoid();
+    aWriter->WriteBool(isVoid);
+
+    if (isVoid) {
+      // represents a nullptr pointer
+      return;
+    }
+
+    WriteSequenceParam<const T&>(aWriter, aParam.BeginReading(),
+                                 aParam.Length());
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    bool isVoid;
+    if (!aReader->ReadBool(&isVoid)) {
+      return false;
+    }
+
+    if (isVoid) {
+      aResult->SetIsVoid(true);
+      return true;
+    }
+
+    return ReadSequenceParam<T>(aReader, [&](uint32_t aLength) -> T* {
+      T* data = nullptr;
+      aResult->GetMutableData(&data, aLength);
+      return data;
+    });
+  }
+};
+
+template <class T>
+struct ParamTraits<nsTString<T>> : ParamTraits<nsTSubstring<T>> {};
+
+template <class T>
+struct ParamTraits<nsTLiteralString<T>> : ParamTraits<nsTSubstring<T>> {};
+
+template <class T, size_t N>
+struct ParamTraits<nsTAutoStringN<T, N>> : ParamTraits<nsTSubstring<T>> {};
+
+template <class T>
+struct ParamTraits<nsTDependentString<T>> : ParamTraits<nsTSubstring<T>> {};
+
+// XXX While this has no special dependencies, it's currently only used in
+// GfxMessageUtils and could be moved there, or generalized to potentially work
+// with any nsTHashSet.
+template <>
+struct ParamTraits<nsTHashSet<uint64_t>> {
+  typedef nsTHashSet<uint64_t> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    uint32_t count = aParam.Count();
+    WriteParam(aWriter, count);
+    for (const auto& key : aParam) {
+      WriteParam(aWriter, key);
+    }
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    uint32_t count;
+    if (!ReadParam(aReader, &count)) {
+      return false;
+    }
+    paramType table(count);
+    for (uint32_t i = 0; i < count; ++i) {
+      uint64_t key;
+      if (!ReadParam(aReader, &key)) {
+        return false;
+      }
+      table.Insert(key);
+    }
+    *aResult = std::move(table);
+    return true;
+  }
+};
+
+template <typename E>
+struct ParamTraits<nsTArray<E>> {
+  typedef nsTArray<E> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteSequenceParam<const E&>(aWriter, aParam.Elements(), aParam.Length());
+  }
+
+  static void Write(MessageWriter* aWriter, paramType&& aParam) {
+    WriteSequenceParam<E&&>(aWriter, aParam.Elements(), aParam.Length());
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadSequenceParam<E>(aReader, [&](uint32_t aLength) {
+      if constexpr (std::is_trivially_default_constructible_v<E>) {
+        return aResult->AppendElements(aLength);
+      } else {
+        aResult->SetCapacity(aLength);
+        return mozilla::Some(MakeBackInserter(*aResult));
+      }
+    });
+  }
+};
+
+template <typename E>
+struct ParamTraits<CopyableTArray<E>> : ParamTraits<nsTArray<E>> {};
+
+template <typename E>
+struct ParamTraits<FallibleTArray<E>> {
+  typedef FallibleTArray<E> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteSequenceParam<const E&>(aWriter, aParam.Elements(), aParam.Length());
+  }
+
+  static void Write(MessageWriter* aWriter, paramType&& aParam) {
+    WriteSequenceParam<E&&>(aWriter, aParam.Elements(), aParam.Length());
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadSequenceParam<E>(aReader, [&](uint32_t aLength) {
+      if constexpr (std::is_trivially_default_constructible_v<E>) {
+        return aResult->AppendElements(aLength, mozilla::fallible);
+      } else {
+        if (!aResult->SetCapacity(aLength, mozilla::fallible)) {
+          return mozilla::Maybe<BackInserter>{};
+        }
+        return mozilla::Some(BackInserter{.mArray = aResult});
+      }
+    });
+  }
+
+ private:
+  struct BackInserter {
+    using iterator_category = std::output_iterator_tag;
+    using value_type = void;
+    using difference_type = void;
+    using pointer = void;
+    using reference = void;
+
+    struct Proxy {
+      paramType& mArray;
+
+      template <typename U>
+      void operator=(U&& aValue) {
+        // This won't fail because we've reserved capacity earlier.
+        MOZ_ALWAYS_TRUE(mArray.AppendElement(aValue, mozilla::fallible));
+      }
+    };
+    Proxy operator*() { return Proxy{.mArray = *mArray}; }
+
+    BackInserter& operator++() { return *this; }
+    BackInserter& operator++(int) { return *this; }
+
+    paramType* mArray = nullptr;
+  };
+};
+
+template <typename E, size_t N>
+struct ParamTraits<AutoTArray<E, N>> : ParamTraits<nsTArray<E>> {
+  typedef AutoTArray<E, N> paramType;
+};
+
+template <typename E, size_t N>
+struct ParamTraits<CopyableAutoTArray<E, N>> : ParamTraits<AutoTArray<E, N>> {};
+
+template <typename T>
+struct ParamTraits<mozilla::dom::Sequence<T>> : ParamTraits<FallibleTArray<T>> {
+};
+
+template <typename E, size_t N, typename AP>
+struct ParamTraits<mozilla::Vector<E, N, AP>> {
+  typedef mozilla::Vector<E, N, AP> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteSequenceParam<const E&>(aWriter, aParam.Elements(), aParam.Length());
+  }
+
+  static void Write(MessageWriter* aWriter, paramType&& aParam) {
+    WriteSequenceParam<E&&>(aWriter, aParam.Elements(), aParam.Length());
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadSequenceParam<E>(aReader, [&](uint32_t aLength) -> E* {
+      if (!aResult->resize(aLength)) {
+        // So that OOM failure shows up as OOM crash instead of IPC FatalError.
+        NS_ABORT_OOM(aLength * sizeof(E));
+      }
+      return aResult->begin();
+    });
+  }
+};
+
+template <typename E>
+struct ParamTraits<std::vector<E>> {
+  typedef std::vector<E> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteSequenceParam<const E&>(aWriter, aParam.data(), aParam.size());
+  }
+  static void Write(MessageWriter* aWriter, paramType&& aParam) {
+    WriteSequenceParam<E&&>(aWriter, aParam.data(), aParam.size());
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadSequenceParam<E>(aReader, [&](uint32_t aLength) {
+      if constexpr (std::is_trivially_default_constructible_v<E>) {
+        aResult->resize(aLength);
+        return aResult->data();
+      } else {
+        aResult->reserve(aLength);
+        return mozilla::Some(std::back_inserter(*aResult));
+      }
+    });
+  }
+};
+
+template <typename K, typename V>
+struct ParamTraits<std::unordered_map<K, V>> final {
+  using T = std::unordered_map<K, V>;
+
+  static void Write(MessageWriter* const writer, const T& in) {
+    WriteParam(writer, in.size());
+    for (const auto& pair : in) {
+      WriteParam(writer, pair.first);
+      WriteParam(writer, pair.second);
+    }
+  }
+
+  static bool Read(MessageReader* const reader, T* const out) {
+    size_t size = 0;
+    if (!ReadParam(reader, &size)) return false;
+    T map;
+    map.reserve(size);
+    for (const auto i : mozilla::IntegerRange(size)) {
+      std::pair<K, V> pair;
+      mozilla::Unused << i;
+      if (!ReadParam(reader, &(pair.first)) ||
+          !ReadParam(reader, &(pair.second))) {
+        return false;
+      }
+      map.insert(std::move(pair));
+    }
+    *out = std::move(map);
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<float> {
+  typedef float paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aWriter->WriteBytes(&aParam, sizeof(paramType));
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return aReader->ReadBytesInto(aResult, sizeof(*aResult));
+  }
+};
+
+template <>
+struct ParamTraits<nsCSSPropertyID>
+    : public ContiguousEnumSerializer<nsCSSPropertyID, eCSSProperty_UNKNOWN,
+                                      eCSSProperty_COUNT> {};
+
+template <>
+struct ParamTraits<nsID> {
+  typedef nsID paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.m0);
+    WriteParam(aWriter, aParam.m1);
+    WriteParam(aWriter, aParam.m2);
+    for (unsigned int i = 0; i < mozilla::ArrayLength(aParam.m3); i++) {
+      WriteParam(aWriter, aParam.m3[i]);
+    }
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    if (!ReadParam(aReader, &(aResult->m0)) ||
+        !ReadParam(aReader, &(aResult->m1)) ||
+        !ReadParam(aReader, &(aResult->m2)))
+      return false;
+
+    for (unsigned int i = 0; i < mozilla::ArrayLength(aResult->m3); i++)
+      if (!ReadParam(aReader, &(aResult->m3[i]))) return false;
+
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<nsContentPolicyType>
+    : public ContiguousEnumSerializer<nsContentPolicyType,
+                                      nsIContentPolicy::TYPE_INVALID,
+                                      nsIContentPolicy::TYPE_END> {};
+
+template <>
+struct ParamTraits<mozilla::TimeDuration> {
+  typedef mozilla::TimeDuration paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mValue);
+  }
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->mValue);
+  };
+};
+
+template <>
+struct ParamTraits<mozilla::TimeStamp> {
+  typedef mozilla::TimeStamp paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mValue);
+  }
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->mValue);
+  };
+};
+
+#ifdef XP_WIN
+
+template <>
+struct ParamTraits<mozilla::TimeStampValue> {
+  typedef mozilla::TimeStampValue paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mGTC);
+    WriteParam(aWriter, aParam.mQPC);
+    WriteParam(aWriter, aParam.mIsNull);
+    WriteParam(aWriter, aParam.mHasQPC);
+  }
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return (ReadParam(aReader, &aResult->mGTC) &&
+            ReadParam(aReader, &aResult->mQPC) &&
+            ReadParam(aReader, &aResult->mIsNull) &&
+            ReadParam(aReader, &aResult->mHasQPC));
+  }
+};
+
+#endif
+
+template <>
+struct ParamTraits<mozilla::dom::ipc::StructuredCloneData> {
+  typedef mozilla::dom::ipc::StructuredCloneData paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    aParam.WriteIPCParams(aWriter);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return aResult->ReadIPCParams(aReader);
+  }
+};
+
+template <class T>
+struct ParamTraits<mozilla::Maybe<T>> {
+  typedef mozilla::Maybe<T> paramType;
+
+  static void Write(MessageWriter* writer, const paramType& param) {
+    if (param.isSome()) {
+      WriteParam(writer, true);
+      WriteParam(writer, param.ref());
+    } else {
+      WriteParam(writer, false);
+    }
+  }
+
+  static void Write(MessageWriter* writer, paramType&& param) {
+    if (param.isSome()) {
+      WriteParam(writer, true);
+      WriteParam(writer, std::move(param.ref()));
+    } else {
+      WriteParam(writer, false);
+    }
+  }
+
+  static bool Read(MessageReader* reader, paramType* result) {
+    bool isSome;
+    if (!ReadParam(reader, &isSome)) {
+      return false;
+    }
+    if (isSome) {
+      mozilla::Maybe<T> tmp = ReadParam<T>(reader).TakeMaybe();
+      if (!tmp) {
+        return false;
+      }
+      *result = std::move(tmp);
+    } else {
+      *result = mozilla::Nothing();
+    }
+    return true;
+  }
+};
+
+template <typename T, typename U>
+struct ParamTraits<mozilla::EnumSet<T, U>> {
+  typedef mozilla::EnumSet<T, U> paramType;
+  typedef U serializedType;
+
+  static void Write(MessageWriter* writer, const paramType& param) {
+    MOZ_RELEASE_ASSERT(IsLegalValue(param.serialize()));
+    WriteParam(writer, param.serialize());
+  }
+
+  static bool Read(MessageReader* reader, paramType* result) {
+    serializedType tmp;
+
+    if (ReadParam(reader, &tmp)) {
+      if (IsLegalValue(tmp)) {
+        result->deserialize(tmp);
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  static constexpr serializedType AllEnumBits() {
+    return ~serializedType(0) >> (std::numeric_limits<serializedType>::digits -
+                                  (mozilla::MaxEnumValue<T>::value + 1));
+  }
+
+  static constexpr bool IsLegalValue(const serializedType value) {
+    static_assert(mozilla::MaxEnumValue<T>::value <
+                      std::numeric_limits<serializedType>::digits,
+                  "Enum max value is not in the range!");
+    static_assert(
+        std::is_unsigned<decltype(mozilla::MaxEnumValue<T>::value)>::value,
+        "Type of MaxEnumValue<T>::value specialization should be unsigned!");
+
+    return (value & AllEnumBits()) == value;
+  }
+};
+
+template <class... Ts>
+struct ParamTraits<mozilla::Variant<Ts...>> {
+  typedef mozilla::Variant<Ts...> paramType;
+  using Tag = typename mozilla::detail::VariantTag<Ts...>::Type;
+
+  static void Write(MessageWriter* writer, const paramType& param) {
+    WriteParam(writer, param.tag);
+    param.match([writer](const auto& t) { WriteParam(writer, t); });
+  }
+
+  // Because VariantReader is a nested struct, we need the dummy template
+  // parameter to avoid making VariantReader<0> an explicit specialization,
+  // which is not allowed for a nested class template
+  template <size_t N, typename dummy = void>
+  struct VariantReader {
+    using Next = VariantReader<N - 1>;
+
+    static bool Read(MessageReader* reader, Tag tag, paramType* result) {
+      // Since the VariantReader specializations start at N , we need to
+      // subtract one to look at N - 1, the first valid tag.  This means our
+      // comparisons are off by 1.  If we get to N = 0 then we have failed to
+      // find a match to the tag.
+      if (tag == N - 1) {
+        // Recall, even though the template parameter is N, we are
+        // actually interested in the N - 1 tag.
+        // Default construct our field within the result outparameter and
+        // directly deserialize into the variant. Note that this means that
+        // every type in Ts needs to be default constructible
+        return ReadParam(reader, &result->template emplace<N - 1>());
+      } else {
+        return Next::Read(reader, tag, result);
+      }
+    }
+
+  };  // VariantReader<N>
+
+  // Since we are conditioning on tag = N - 1 in the preceding specialization,
+  // if we get to `VariantReader<0, dummy>` we have failed to find
+  // a matching tag.
+  template <typename dummy>
+  struct VariantReader<0, dummy> {
+    static bool Read(MessageReader* reader, Tag tag, paramType* result) {
+      return false;
+    }
+  };
+
+  static bool Read(MessageReader* reader, paramType* result) {
+    Tag tag;
+    if (ReadParam(reader, &tag)) {
+      return VariantReader<sizeof...(Ts)>::Read(reader, tag, result);
+    }
+    return false;
+  }
+};
+
+template <typename T>
+struct ParamTraits<mozilla::dom::Optional<T>> {
+  typedef mozilla::dom::Optional<T> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    if (aParam.WasPassed()) {
+      WriteParam(aWriter, true);
+      WriteParam(aWriter, aParam.Value());
+      return;
+    }
+
+    WriteParam(aWriter, false);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    bool wasPassed = false;
+
+    if (!ReadParam(aReader, &wasPassed)) {
+      return false;
+    }
+
+    aResult->Reset();
+
+    if (wasPassed) {
+      if (!ReadParam(aReader, &aResult->Construct())) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+};
+
+template <>
+struct ParamTraits<nsAtom*> {
+  typedef nsAtom paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType* aParam);
+  static bool Read(MessageReader* aReader, RefPtr<paramType>* aResult);
+};
+
+struct CrossOriginOpenerPolicyValidator {
+  using IntegralType =
+      std::underlying_type_t<nsILoadInfo::CrossOriginOpenerPolicy>;
+
+  static bool IsLegalValue(const IntegralType e) {
+    return AreIntegralValuesEqual(e, nsILoadInfo::OPENER_POLICY_UNSAFE_NONE) ||
+           AreIntegralValuesEqual(e, nsILoadInfo::OPENER_POLICY_SAME_ORIGIN) ||
+           AreIntegralValuesEqual(
+               e, nsILoadInfo::OPENER_POLICY_SAME_ORIGIN_ALLOW_POPUPS) ||
+           AreIntegralValuesEqual(
+               e, nsILoadInfo::
+                      OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP);
+  }
+
+ private:
+  static bool AreIntegralValuesEqual(
+      const IntegralType aLhs,
+      const nsILoadInfo::CrossOriginOpenerPolicy aRhs) {
+    return aLhs == static_cast<IntegralType>(aRhs);
+  }
+};
+
+template <>
+struct ParamTraits<nsILoadInfo::CrossOriginOpenerPolicy>
+    : EnumSerializer<nsILoadInfo::CrossOriginOpenerPolicy,
+                     CrossOriginOpenerPolicyValidator> {};
+
+struct CrossOriginEmbedderPolicyValidator {
+  using IntegralType =
+      std::underlying_type_t<nsILoadInfo::CrossOriginEmbedderPolicy>;
+
+  static bool IsLegalValue(const IntegralType e) {
+    return AreIntegralValuesEqual(e, nsILoadInfo::EMBEDDER_POLICY_NULL) ||
+           AreIntegralValuesEqual(e,
+                                  nsILoadInfo::EMBEDDER_POLICY_REQUIRE_CORP) ||
+           AreIntegralValuesEqual(e,
+                                  nsILoadInfo::EMBEDDER_POLICY_CREDENTIALLESS);
+  }
+
+ private:
+  static bool AreIntegralValuesEqual(
+      const IntegralType aLhs,
+      const nsILoadInfo::CrossOriginEmbedderPolicy aRhs) {
+    return aLhs == static_cast<IntegralType>(aRhs);
+  }
+};
+
+template <>
+struct ParamTraits<nsILoadInfo::CrossOriginEmbedderPolicy>
+    : EnumSerializer<nsILoadInfo::CrossOriginEmbedderPolicy,
+                     CrossOriginEmbedderPolicyValidator> {};
+
+template <size_t N, typename Word>
+struct ParamTraits<mozilla::BitSet<N, Word>> {
+  typedef mozilla::BitSet<N, Word> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    for (Word word : aParam.Storage()) {
+      WriteParam(aWriter, word);
+    }
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    for (Word& word : aResult->Storage()) {
+      if (!ReadParam(aReader, &word)) {
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+template <typename T>
+struct ParamTraits<mozilla::UniquePtr<T>> {
+  typedef mozilla::UniquePtr<T> paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    bool isNull = aParam == nullptr;
+    WriteParam(aWriter, isNull);
+
+    if (!isNull) {
+      WriteParam(aWriter, *aParam.get());
+    }
+  }
+
+  static bool Read(IPC::MessageReader* aReader, paramType* aResult) {
+    bool isNull = true;
+    if (!ReadParam(aReader, &isNull)) {
+      return false;
+    }
+
+    if (isNull) {
+      aResult->reset();
+    } else {
+      *aResult = mozilla::MakeUnique<T>();
+      if (!ReadParam(aReader, aResult->get())) {
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+template <typename... Ts>
+struct ParamTraits<std::tuple<Ts...>> {
+  typedef std::tuple<Ts...> paramType;
+
+  template <typename U>
+  static void Write(IPC::MessageWriter* aWriter, U&& aParam) {
+    WriteInternal(aWriter, std::forward<U>(aParam),
+                  std::index_sequence_for<Ts...>{});
+  }
+
+  static bool Read(IPC::MessageReader* aReader, std::tuple<Ts...>* aResult) {
+    return ReadInternal(aReader, *aResult, std::index_sequence_for<Ts...>{});
+  }
+
+ private:
+  template <size_t... Is>
+  static void WriteInternal(IPC::MessageWriter* aWriter,
+                            const std::tuple<Ts...>& aParam,
+                            std::index_sequence<Is...>) {
+    WriteParams(aWriter, std::get<Is>(aParam)...);
+  }
+
+  template <size_t... Is>
+  static void WriteInternal(IPC::MessageWriter* aWriter,
+                            std::tuple<Ts...>&& aParam,
+                            std::index_sequence<Is...>) {
+    WriteParams(aWriter, std::move(std::get<Is>(aParam))...);
+  }
+
+  template <size_t... Is>
+  static bool ReadInternal(IPC::MessageReader* aReader,
+                           std::tuple<Ts...>& aResult,
+                           std::index_sequence<Is...>) {
+    return ReadParams(aReader, std::get<Is>(aResult)...);
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::net::LinkHeader> {
+  typedef mozilla::net::LinkHeader paramType;
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.mHref);
+    WriteParam(aWriter, aParam.mRel);
+    WriteParam(aWriter, aParam.mTitle);
+    WriteParam(aWriter, aParam.mIntegrity);
+    WriteParam(aWriter, aParam.mSrcset);
+    WriteParam(aWriter, aParam.mSizes);
+    WriteParam(aWriter, aParam.mType);
+    WriteParam(aWriter, aParam.mMedia);
+    WriteParam(aWriter, aParam.mCrossOrigin);
+    WriteParam(aWriter, aParam.mReferrerPolicy);
+    WriteParam(aWriter, aParam.mAs);
+  }
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    if (!ReadParam(aReader, &aResult->mHref)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mRel)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mTitle)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mIntegrity)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mSrcset)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mSizes)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mType)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mMedia)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mCrossOrigin)) {
+      return false;
+    }
+    if (!ReadParam(aReader, &aResult->mReferrerPolicy)) {
+      return false;
+    }
+    return ReadParam(aReader, &aResult->mAs);
+  };
+};
+
+} /* namespace IPC */
+
+#endif /* __IPC_GLUE_IPCMESSAGEUTILSSPECIALIZATIONS_H__ */
diff --git a/ipc/glue/IPCStream.ipdlh b/ipc/glue/IPCStream.ipdlh
new file mode 100644
index 0000000000..abf7ef7714
--- /dev/null
+++ b/ipc/glue/IPCStream.ipdlh
@@ -0,0 +1,22 @@
+/* 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 InputStreamParams;
+include ProtocolTypes;
+
+namespace mozilla {
+namespace ipc {
+
+// Use IPCStream in your ipdl to represent serialized nsIInputStreams. Then use
+// SerializeIPCStream from IPCStreamUtils.h to perform the serialization.
+//
+// NOTE: If you don't need to handle nsIInputStream serialization failure,
+// `nsIInputStream` may be used directly by IPDL protocols.
+struct IPCStream
+{
+  InputStreamParams stream;
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/IPCStreamUtils.cpp b/ipc/glue/IPCStreamUtils.cpp
new file mode 100644
index 0000000000..265cb1cff8
--- /dev/null
+++ b/ipc/glue/IPCStreamUtils.cpp
@@ -0,0 +1,191 @@
+/* -*- 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 "IPCStreamUtils.h"
+
+#include "ipc/IPCMessageUtilsSpecializations.h"
+
+#include "nsIHttpHeaderVisitor.h"
+#include "nsIIPCSerializableInputStream.h"
+#include "mozIRemoteLazyInputStream.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/ipc/IPCStream.h"
+#include "mozilla/ipc/InputStreamUtils.h"
+#include "mozilla/InputStreamLengthHelper.h"
+#include "mozilla/RemoteLazyInputStreamParent.h"
+#include "mozilla/Unused.h"
+#include "nsIMIMEInputStream.h"
+#include "nsNetCID.h"
+
+using namespace mozilla::dom;
+
+namespace mozilla::ipc {
+
+namespace {
+
+class MIMEStreamHeaderVisitor final : public nsIHttpHeaderVisitor {
+ public:
+  explicit MIMEStreamHeaderVisitor(
+      nsTArray<mozilla::ipc::HeaderEntry>& aHeaders)
+      : mHeaders(aHeaders) {}
+
+  NS_DECL_ISUPPORTS
+  NS_IMETHOD VisitHeader(const nsACString& aName,
+                         const nsACString& aValue) override {
+    auto el = mHeaders.AppendElement();
+    el->name() = aName;
+    el->value() = aValue;
+    return NS_OK;
+  }
+
+ private:
+  ~MIMEStreamHeaderVisitor() = default;
+
+  nsTArray<mozilla::ipc::HeaderEntry>& mHeaders;
+};
+
+NS_IMPL_ISUPPORTS(MIMEStreamHeaderVisitor, nsIHttpHeaderVisitor)
+
+static bool SerializeLazyInputStream(nsIInputStream* aStream,
+                                     IPCStream& aValue) {
+  MOZ_ASSERT(aStream);
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  // If we're serializing a MIME stream, ensure we preserve header data which
+  // would not be preserved by a RemoteLazyInputStream wrapper.
+  if (nsCOMPtr<nsIMIMEInputStream> mimeStream = do_QueryInterface(aStream)) {
+    MIMEInputStreamParams params;
+    params.startedReading() = false;
+
+    nsCOMPtr<nsIHttpHeaderVisitor> visitor =
+        new MIMEStreamHeaderVisitor(params.headers());
+    if (NS_WARN_IF(NS_FAILED(mimeStream->VisitHeaders(visitor)))) {
+      return false;
+    }
+
+    nsCOMPtr<nsIInputStream> dataStream;
+    if (NS_FAILED(mimeStream->GetData(getter_AddRefs(dataStream)))) {
+      return false;
+    }
+    if (dataStream) {
+      IPCStream data;
+      if (!SerializeLazyInputStream(dataStream, data)) {
+        return false;
+      }
+      params.optionalStream().emplace(std::move(data.stream()));
+    }
+
+    aValue.stream() = std::move(params);
+    return true;
+  }
+
+  RefPtr<RemoteLazyInputStream> lazyStream =
+      RemoteLazyInputStream::WrapStream(aStream);
+  if (NS_WARN_IF(!lazyStream)) {
+    return false;
+  }
+
+  aValue.stream() = RemoteLazyInputStreamParams(lazyStream);
+
+  return true;
+}
+
+}  // anonymous namespace
+
+bool SerializeIPCStream(already_AddRefed<nsIInputStream> aInputStream,
+                        IPCStream& aValue, bool aAllowLazy) {
+  nsCOMPtr<nsIInputStream> stream(std::move(aInputStream));
+  if (!stream) {
+    MOZ_ASSERT_UNREACHABLE(
+        "Use the Maybe<...> overload to serialize optional nsIInputStreams");
+    return false;
+  }
+
+  // When requesting a delayed start stream from the parent process, serialize
+  // it as a remote lazy stream to avoid bloating payloads.
+  if (aAllowLazy && XRE_IsParentProcess()) {
+    return SerializeLazyInputStream(stream, aValue);
+  }
+
+  if (nsCOMPtr<nsIIPCSerializableInputStream> serializable =
+          do_QueryInterface(stream)) {
+    // If you change this size, please also update the payload size in
+    // test_reload_large_postdata.html.
+    const uint64_t kTooLargeStream = 1024 * 1024;
+
+    uint32_t sizeUsed = 0;
+    serializable->Serialize(aValue.stream(), kTooLargeStream, &sizeUsed);
+
+    MOZ_ASSERT(sizeUsed <= kTooLargeStream);
+
+    if (aValue.stream().type() == InputStreamParams::T__None) {
+      MOZ_CRASH("Serialize failed!");
+    }
+    return true;
+  }
+
+  InputStreamHelper::SerializeInputStreamAsPipe(stream, aValue.stream());
+  if (aValue.stream().type() == InputStreamParams::T__None) {
+    MOZ_ASSERT_UNREACHABLE("Serializing as a pipe failed");
+    return false;
+  }
+  return true;
+}
+
+bool SerializeIPCStream(already_AddRefed<nsIInputStream> aInputStream,
+                        Maybe<IPCStream>& aValue, bool aAllowLazy) {
+  nsCOMPtr<nsIInputStream> stream(std::move(aInputStream));
+  if (!stream) {
+    aValue.reset();
+    return true;
+  }
+
+  IPCStream value;
+  if (SerializeIPCStream(stream.forget(), value, aAllowLazy)) {
+    aValue = Some(value);
+    return true;
+  }
+  return false;
+}
+
+already_AddRefed<nsIInputStream> DeserializeIPCStream(const IPCStream& aValue) {
+  return InputStreamHelper::DeserializeInputStream(aValue.stream());
+}
+
+already_AddRefed<nsIInputStream> DeserializeIPCStream(
+    const Maybe<IPCStream>& aValue) {
+  if (aValue.isNothing()) {
+    return nullptr;
+  }
+
+  return DeserializeIPCStream(aValue.ref());
+}
+
+}  // namespace mozilla::ipc
+
+void IPC::ParamTraits<nsIInputStream*>::Write(IPC::MessageWriter* aWriter,
+                                              nsIInputStream* aParam) {
+  mozilla::Maybe<mozilla::ipc::IPCStream> stream;
+  if (!mozilla::ipc::SerializeIPCStream(do_AddRef(aParam), stream,
+                                        /* aAllowLazy */ true)) {
+    MOZ_CRASH("Failed to serialize nsIInputStream");
+  }
+
+  WriteParam(aWriter, stream);
+}
+
+bool IPC::ParamTraits<nsIInputStream*>::Read(IPC::MessageReader* aReader,
+                                             RefPtr<nsIInputStream>* aResult) {
+  mozilla::Maybe<mozilla::ipc::IPCStream> ipcStream;
+  if (!ReadParam(aReader, &ipcStream)) {
+    return false;
+  }
+
+  *aResult = mozilla::ipc::DeserializeIPCStream(ipcStream);
+  return true;
+}
diff --git a/ipc/glue/IPCStreamUtils.h b/ipc/glue/IPCStreamUtils.h
new file mode 100644
index 0000000000..c681f7cf1a
--- /dev/null
+++ b/ipc/glue/IPCStreamUtils.h
@@ -0,0 +1,51 @@
+/* -*- 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_ipc_IPCStreamUtils_h
+#define mozilla_ipc_IPCStreamUtils_h
+
+#include "mozilla/ipc/IPCStream.h"
+#include "nsCOMPtr.h"
+#include "nsIInputStream.h"
+
+namespace mozilla::ipc {
+
+// Serialize an IPCStream to be sent over IPC fallibly.
+//
+// If |aAllowLazy| is true the stream may be serialized as a
+// RemoteLazyInputStream when being sent from child to parent.
+//
+// ParamTraits<nsIInputStream> may be used instead if serialization cannot be
+// fallible.
+[[nodiscard]] bool SerializeIPCStream(
+    already_AddRefed<nsIInputStream> aInputStream, IPCStream& aValue,
+    bool aAllowLazy);
+
+// If serialization fails, `aValue` will be initialized to `Nothing()`, so this
+// return value is safe to ignore.
+bool SerializeIPCStream(already_AddRefed<nsIInputStream> aInputStream,
+                        Maybe<IPCStream>& aValue, bool aAllowLazy);
+
+// Deserialize an IPCStream received from an actor call.  These methods
+// work in both the child and parent.
+already_AddRefed<nsIInputStream> DeserializeIPCStream(const IPCStream& aValue);
+
+already_AddRefed<nsIInputStream> DeserializeIPCStream(
+    const Maybe<IPCStream>& aValue);
+
+}  // namespace mozilla::ipc
+
+namespace IPC {
+
+template <>
+struct ParamTraits<nsIInputStream*> {
+  static void Write(MessageWriter* aWriter, nsIInputStream* aParam);
+  static bool Read(MessageReader* aReader, RefPtr<nsIInputStream>* aResult);
+};
+
+}  // namespace IPC
+
+#endif  // mozilla_ipc_IPCStreamUtils_h
diff --git a/ipc/glue/IPCTypes.h b/ipc/glue/IPCTypes.h
new file mode 100644
index 0000000000..fc6bf765e2
--- /dev/null
+++ b/ipc/glue/IPCTypes.h
@@ -0,0 +1,20 @@
+/* -*- 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 IPC_GLUE_IPCTYPES_H_
+#define IPC_GLUE_IPCTYPES_H_
+
+#include <cstdint>
+
+namespace mozilla {
+
+// This is a cross-platform approximation to HANDLE, which we expect
+// to be typedef'd to void* or thereabouts.
+typedef uintptr_t WindowsHandle;
+
+}  // namespace mozilla
+
+#endif  // IPC_GLUE_IPCTYPES_H_
diff --git a/ipc/glue/IPDLParamTraits.h b/ipc/glue/IPDLParamTraits.h
new file mode 100644
index 0000000000..48649d92de
--- /dev/null
+++ b/ipc/glue/IPDLParamTraits.h
@@ -0,0 +1,65 @@
+/* -*- 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_ipc_IPDLParamTraits_h
+#define mozilla_ipc_IPDLParamTraits_h
+
+#include "chrome/common/ipc_message_utils.h"
+#include "ipc/IPCMessageUtilsSpecializations.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Variant.h"
+
+#include "nsTArray.h"
+
+#include <type_traits>
+
+namespace mozilla {
+namespace ipc {
+
+class IProtocol;
+
+//
+// IPDLParamTraits was an extended version of ParamTraits. Unlike ParamTraits,
+// IPDLParamTraits passes an additional IProtocol* argument to the
+// write and read methods.
+//
+// Previously this was required for serializing and deserializing types which
+// require knowledge of which protocol they're being sent over, however the
+// actor is now available through `IPC::Message{Writer,Reader}::GetActor()` so
+// the extra argument is no longer necessary. Please use `IPC::ParamTraits` in
+// the future.
+//
+// Types which implement IPDLParamTraits are also supported by ParamTraits.
+//
+template <typename P>
+struct IPDLParamTraits {};
+
+//
+// WriteIPDLParam and ReadIPDLParam are like IPC::WriteParam and IPC::ReadParam,
+// however, they also accept a redundant extra actor argument.
+//
+// NOTE: WriteIPDLParam takes a universal reference, so that it can support
+// whatever reference type is supported by the underlying ParamTraits::Write
+// implementation.
+//
+template <typename P>
+static MOZ_NEVER_INLINE void WriteIPDLParam(IPC::MessageWriter* aWriter,
+                                            IProtocol* aActor, P&& aParam) {
+  MOZ_ASSERT(aActor == aWriter->GetActor());
+  IPC::WriteParam(aWriter, std::forward<P>(aParam));
+}
+
+template <typename P>
+static MOZ_NEVER_INLINE bool ReadIPDLParam(IPC::MessageReader* aReader,
+                                           IProtocol* aActor, P* aResult) {
+  MOZ_ASSERT(aActor == aReader->GetActor());
+  return IPC::ReadParam(aReader, aResult);
+}
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // defined(mozilla_ipc_IPDLParamTraits_h)
diff --git a/ipc/glue/IPDLStructMember.h b/ipc/glue/IPDLStructMember.h
new file mode 100644
index 0000000000..d2e3636054
--- /dev/null
+++ b/ipc/glue/IPDLStructMember.h
@@ -0,0 +1,37 @@
+/* -*- 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_ipc_IPDLStructMember_h
+#define mozilla_ipc_IPDLStructMember_h
+
+#include <type_traits>
+#include <utility>
+#include "mozilla/Attributes.h"
+
+namespace mozilla::ipc {
+
+// For types which are trivially default constructible, like `int`, force the
+// value constructor by wrapping the type in this struct.  This is an
+// implementation detail which will be hidden by the generated IPDL compiler
+// code.
+template <typename T>
+struct IPDLStructMemberWrapper {
+  template <typename... Args>
+  MOZ_IMPLICIT IPDLStructMemberWrapper(Args&&... aArgs)
+      : mVal(std::forward<Args>(aArgs)...) {}
+  MOZ_IMPLICIT operator T&() { return mVal; }
+  MOZ_IMPLICIT operator const T&() const { return mVal; }
+  T mVal{};
+};
+
+template <typename T>
+using IPDLStructMember =
+    std::conditional_t<std::is_trivially_default_constructible_v<T>,
+                       IPDLStructMemberWrapper<T>, T>;
+
+}  // namespace mozilla::ipc
+
+#endif  // mozilla_ipc_IPDLStructMember_h
diff --git a/ipc/glue/IdleSchedulerChild.cpp b/ipc/glue/IdleSchedulerChild.cpp
new file mode 100644
index 0000000000..bd05f0958a
--- /dev/null
+++ b/ipc/glue/IdleSchedulerChild.cpp
@@ -0,0 +1,152 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/IdleSchedulerChild.h"
+#include "mozilla/ipc/IdleSchedulerParent.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/IdlePeriodState.h"
+#include "mozilla/Telemetry.h"
+#include "BackgroundChild.h"
+
+namespace mozilla::ipc {
+
+static IdleSchedulerChild* sMainThreadIdleScheduler = nullptr;
+static bool sIdleSchedulerDestroyed = false;
+
+IdleSchedulerChild::~IdleSchedulerChild() {
+  if (sMainThreadIdleScheduler == this) {
+    sMainThreadIdleScheduler = nullptr;
+    sIdleSchedulerDestroyed = true;
+  }
+  MOZ_ASSERT(!mIdlePeriodState);
+}
+
+void IdleSchedulerChild::Init(IdlePeriodState* aIdlePeriodState) {
+  mIdlePeriodState = aIdlePeriodState;
+
+  RefPtr<IdleSchedulerChild> scheduler = this;
+  auto resolve =
+      [&](std::tuple<mozilla::Maybe<SharedMemoryHandle>, uint32_t>&& aResult) {
+        if (std::get<0>(aResult)) {
+          mActiveCounter.SetHandle(std::move(*std::get<0>(aResult)), false);
+          mActiveCounter.Map(sizeof(int32_t));
+          mChildId = std::get<1>(aResult);
+          if (mChildId && mIdlePeriodState && mIdlePeriodState->IsActive()) {
+            SetActive();
+          }
+        }
+      };
+
+  auto reject = [&](ResponseRejectReason) {};
+  SendInitForIdleUse(std::move(resolve), std::move(reject));
+}
+
+IPCResult IdleSchedulerChild::RecvIdleTime(uint64_t aId, TimeDuration aBudget) {
+  if (mIdlePeriodState) {
+    mIdlePeriodState->SetIdleToken(aId, aBudget);
+  }
+  return IPC_OK();
+}
+
+void IdleSchedulerChild::SetActive() {
+  if (mChildId && CanSend() && mActiveCounter.memory()) {
+    ++(static_cast<Atomic<int32_t>*>(
+        mActiveCounter.memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER]);
+    ++(static_cast<Atomic<int32_t>*>(mActiveCounter.memory())[mChildId]);
+  }
+}
+
+bool IdleSchedulerChild::SetPaused() {
+  if (mChildId && CanSend() && mActiveCounter.memory()) {
+    --(static_cast<Atomic<int32_t>*>(mActiveCounter.memory())[mChildId]);
+    // The following expression reduces the global activity count and checks if
+    // it drops below the cpu counter limit.
+    return (static_cast<Atomic<int32_t>*>(
+               mActiveCounter
+                   .memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER])-- ==
+           static_cast<Atomic<int32_t>*>(
+               mActiveCounter.memory())[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER];
+  }
+
+  return false;
+}
+
+RefPtr<IdleSchedulerChild::MayGCPromise> IdleSchedulerChild::MayGCNow() {
+  if (mIsRequestingGC || mIsDoingGC) {
+    return MayGCPromise::CreateAndResolve(false, __func__);
+  }
+  TimeStamp wait_since = TimeStamp::Now();
+
+  mIsRequestingGC = true;
+  return SendRequestGC()->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [self = RefPtr(this), wait_since](bool aIgnored) {
+        // Only one of these may be true at a time.
+        MOZ_ASSERT(!(self->mIsRequestingGC && self->mIsDoingGC));
+
+        // The parent process always says yes, sometimes after a delay.
+        if (self->mIsRequestingGC) {
+          Telemetry::AccumulateTimeDelta(Telemetry::GC_WAIT_FOR_IDLE_MS,
+                                         wait_since);
+          self->mIsRequestingGC = false;
+          self->mIsDoingGC = true;
+          return MayGCPromise::CreateAndResolve(true, __func__);
+        }
+        return MayGCPromise::CreateAndResolve(false, __func__);
+      },
+      [self = RefPtr(this)](ResponseRejectReason reason) {
+        self->mIsRequestingGC = false;
+        return MayGCPromise::CreateAndReject(reason, __func__);
+      });
+}
+
+void IdleSchedulerChild::StartedGC() {
+  // Only one of these may be true at a time.
+  MOZ_ASSERT(!(mIsRequestingGC && mIsDoingGC));
+
+  // If mRequestingGC was true then when the outstanding GC request returns
+  // it'll see that the GC has already started.
+  mIsRequestingGC = false;
+
+  if (!mIsDoingGC) {
+    if (CanSend()) {
+      SendStartedGC();
+    }
+    mIsDoingGC = true;
+  }
+}
+
+void IdleSchedulerChild::DoneGC() {
+  if (mIsDoingGC) {
+    if (CanSend()) {
+      SendDoneGC();
+    }
+    mIsDoingGC = false;
+  }
+}
+
+IdleSchedulerChild* IdleSchedulerChild::GetMainThreadIdleScheduler() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (sMainThreadIdleScheduler) {
+    return sMainThreadIdleScheduler;
+  }
+
+  if (sIdleSchedulerDestroyed) {
+    return nullptr;
+  }
+
+  ipc::PBackgroundChild* background =
+      ipc::BackgroundChild::GetOrCreateForCurrentThread();
+  if (background) {
+    sMainThreadIdleScheduler = new ipc::IdleSchedulerChild();
+    background->SendPIdleSchedulerConstructor(sMainThreadIdleScheduler);
+  }
+  return sMainThreadIdleScheduler;
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/IdleSchedulerChild.h b/ipc/glue/IdleSchedulerChild.h
new file mode 100644
index 0000000000..cf93084bfc
--- /dev/null
+++ b/ipc/glue/IdleSchedulerChild.h
@@ -0,0 +1,75 @@
+/* -*- 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_ipc_IdleSchedulerChild_h__
+#define mozilla_ipc_IdleSchedulerChild_h__
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ipc/PIdleSchedulerChild.h"
+
+class nsIIdlePeriod;
+
+namespace mozilla {
+class IdlePeriodState;
+
+namespace ipc {
+
+class BackgroundChildImpl;
+
+class IdleSchedulerChild final : public PIdleSchedulerChild {
+ public:
+  IdleSchedulerChild() = default;
+
+  NS_INLINE_DECL_REFCOUNTING(IdleSchedulerChild)
+
+  IPCResult RecvIdleTime(uint64_t aId, TimeDuration aBudget);
+
+  void Init(IdlePeriodState* aIdlePeriodState);
+
+  void Disconnect() { mIdlePeriodState = nullptr; }
+
+  // See similar methods on PrioritizedEventQueue.
+  void SetActive();
+  // Returns true if activity state dropped below cpu count.
+  bool SetPaused();
+
+  typedef MozPromise<bool, ResponseRejectReason, true> MayGCPromise;
+
+  // Returns null if a GC or GC request is already in progress.
+  RefPtr<MayGCPromise> MayGCNow();
+
+  // Regardless of how a GC is started we get informed via these.
+  void StartedGC();
+  void DoneGC();
+
+  // Returns nullptr if this is the parent process or the IdleSchedulerChild has
+  // already been destroyed, eg if IPC is shutting down.
+  static IdleSchedulerChild* GetMainThreadIdleScheduler();
+
+ private:
+  ~IdleSchedulerChild();
+
+  friend class BackgroundChildImpl;
+
+  // See IdleScheduleParent::sActiveChildCounter
+  base::SharedMemory mActiveCounter;
+
+  IdlePeriodState* mIdlePeriodState = nullptr;
+
+  uint32_t mChildId = 0;
+
+  // These fields replicate those in IdleSchedulerParent.  Tracking them here
+  // ensures we don't send confusing information to the parent, while
+  // nsJSEnvironment is free to tell us about any GCs.
+  bool mIsRequestingGC = false;
+  bool mIsDoingGC = false;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_IdleSchedulerChild_h__
diff --git a/ipc/glue/IdleSchedulerParent.cpp b/ipc/glue/IdleSchedulerParent.cpp
new file mode 100644
index 0000000000..c5cf0b3b20
--- /dev/null
+++ b/ipc/glue/IdleSchedulerParent.cpp
@@ -0,0 +1,467 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/StaticPrefs_page_load.h"
+#include "mozilla/StaticPrefs_javascript.h"
+#include "mozilla/Unused.h"
+#include "mozilla/ipc/IdleSchedulerParent.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/Telemetry.h"
+#include "nsSystemInfo.h"
+#include "nsThreadUtils.h"
+#include "nsITimer.h"
+#include "nsIThread.h"
+
+namespace mozilla::ipc {
+
+base::SharedMemory* IdleSchedulerParent::sActiveChildCounter = nullptr;
+std::bitset<NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT>
+    IdleSchedulerParent::sInUseChildCounters;
+LinkedList<IdleSchedulerParent> IdleSchedulerParent::sIdleAndGCRequests;
+int32_t IdleSchedulerParent::sMaxConcurrentIdleTasksInChildProcesses = 1;
+uint32_t IdleSchedulerParent::sMaxConcurrentGCs = 1;
+uint32_t IdleSchedulerParent::sActiveGCs = 0;
+bool IdleSchedulerParent::sRecordGCTelemetry = false;
+uint32_t IdleSchedulerParent::sNumWaitingGC = 0;
+uint32_t IdleSchedulerParent::sChildProcessesRunningPrioritizedOperation = 0;
+uint32_t IdleSchedulerParent::sChildProcessesAlive = 0;
+nsITimer* IdleSchedulerParent::sStarvationPreventer = nullptr;
+
+uint32_t IdleSchedulerParent::sNumCPUs = 0;
+uint32_t IdleSchedulerParent::sPrefConcurrentGCsMax = 0;
+uint32_t IdleSchedulerParent::sPrefConcurrentGCsCPUDivisor = 0;
+
+IdleSchedulerParent::IdleSchedulerParent() {
+  MOZ_ASSERT(!AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownThreads));
+
+  sChildProcessesAlive++;
+
+  uint32_t max_gcs_pref =
+      StaticPrefs::javascript_options_concurrent_multiprocess_gcs_max();
+  uint32_t cpu_divisor_pref =
+      StaticPrefs::javascript_options_concurrent_multiprocess_gcs_cpu_divisor();
+  if (!max_gcs_pref) {
+    max_gcs_pref = UINT32_MAX;
+  }
+  if (!cpu_divisor_pref) {
+    cpu_divisor_pref = 4;
+  }
+
+  if (!sNumCPUs) {
+    // While waiting for the real logical core count behave as if there was
+    // just one core.
+    sNumCPUs = 1;
+
+    // nsISystemInfo can be initialized only on the main thread.
+    nsCOMPtr<nsIThread> thread = do_GetCurrentThread();
+    nsCOMPtr<nsIRunnable> runnable =
+        NS_NewRunnableFunction("cpucount getter", [thread]() {
+          ProcessInfo processInfo = {};
+          if (NS_SUCCEEDED(CollectProcessInfo(processInfo))) {
+            uint32_t num_cpus = processInfo.cpuCount;
+            // We have a new cpu count, Update the number of idle tasks.
+            if (MOZ_LIKELY(!AppShutdown::IsInOrBeyond(
+                    ShutdownPhase::XPCOMShutdownThreads))) {
+              nsCOMPtr<nsIRunnable> runnable = NS_NewRunnableFunction(
+                  "IdleSchedulerParent::CalculateNumIdleTasks", [num_cpus]() {
+                    // We're setting this within this lambda because it's run on
+                    // the correct thread and avoids a race.
+                    sNumCPUs = num_cpus;
+
+                    // This reads the sPrefConcurrentGCsMax and
+                    // sPrefConcurrentGCsCPUDivisor values set below, it will
+                    // run after the code that sets those.
+                    CalculateNumIdleTasks();
+                  });
+
+              thread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+            }
+          }
+        });
+    NS_DispatchBackgroundTask(runnable.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
+  }
+
+  if (sPrefConcurrentGCsMax != max_gcs_pref ||
+      sPrefConcurrentGCsCPUDivisor != cpu_divisor_pref) {
+    // We execute this if these preferences have changed. We also want to make
+    // sure it executes for the first IdleSchedulerParent, which it does because
+    // sPrefConcurrentGCsMax and sPrefConcurrentGCsCPUDivisor are initially
+    // zero.
+    sPrefConcurrentGCsMax = max_gcs_pref;
+    sPrefConcurrentGCsCPUDivisor = cpu_divisor_pref;
+
+    CalculateNumIdleTasks();
+  }
+}
+
+void IdleSchedulerParent::CalculateNumIdleTasks() {
+  MOZ_ASSERT(sNumCPUs);
+  MOZ_ASSERT(sPrefConcurrentGCsMax);
+  MOZ_ASSERT(sPrefConcurrentGCsCPUDivisor);
+
+  // On one and two processor (or hardware thread) systems this will
+  // allow one concurrent idle task.
+  sMaxConcurrentIdleTasksInChildProcesses = int32_t(std::max(sNumCPUs, 1u));
+  sMaxConcurrentGCs =
+      std::min(std::max(sNumCPUs / sPrefConcurrentGCsCPUDivisor, 1u),
+               sPrefConcurrentGCsMax);
+
+  if (sActiveChildCounter && sActiveChildCounter->memory()) {
+    static_cast<Atomic<int32_t>*>(
+        sActiveChildCounter->memory())[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] =
+        static_cast<int32_t>(sMaxConcurrentIdleTasksInChildProcesses);
+  }
+  IdleSchedulerParent::Schedule(nullptr);
+}
+
+IdleSchedulerParent::~IdleSchedulerParent() {
+  // We can't know if an active process just crashed, so we just always expect
+  // that is the case.
+  if (mChildId) {
+    sInUseChildCounters[mChildId] = false;
+    if (sActiveChildCounter && sActiveChildCounter->memory() &&
+        static_cast<Atomic<int32_t>*>(
+            sActiveChildCounter->memory())[mChildId]) {
+      --static_cast<Atomic<int32_t>*>(
+          sActiveChildCounter
+              ->memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER];
+      static_cast<Atomic<int32_t>*>(sActiveChildCounter->memory())[mChildId] =
+          0;
+    }
+  }
+
+  if (mRunningPrioritizedOperation) {
+    --sChildProcessesRunningPrioritizedOperation;
+  }
+
+  if (mDoingGC) {
+    // Give back our GC token.
+    sActiveGCs--;
+  }
+
+  if (mRequestingGC) {
+    mRequestingGC.value()(false);
+    mRequestingGC = Nothing();
+  }
+
+  // Remove from the scheduler's queue.
+  if (isInList()) {
+    remove();
+  }
+
+  MOZ_ASSERT(sChildProcessesAlive > 0);
+  sChildProcessesAlive--;
+  if (sChildProcessesAlive == 0) {
+    MOZ_ASSERT(sIdleAndGCRequests.isEmpty());
+    delete sActiveChildCounter;
+    sActiveChildCounter = nullptr;
+
+    if (sStarvationPreventer) {
+      sStarvationPreventer->Cancel();
+      NS_RELEASE(sStarvationPreventer);
+    }
+  }
+
+  Schedule(nullptr);
+}
+
+IPCResult IdleSchedulerParent::RecvInitForIdleUse(
+    InitForIdleUseResolver&& aResolve) {
+  // This must already be non-zero, if it is zero then the cleanup code for the
+  // shared memory (initialised below) will never run.  The invariant is that if
+  // the shared memory is initialsed, then this is non-zero.
+  MOZ_ASSERT(sChildProcessesAlive > 0);
+
+  MOZ_ASSERT(IsNotDoingIdleTask());
+
+  // Create a shared memory object which is shared across all the relevant
+  // processes.
+  if (!sActiveChildCounter) {
+    sActiveChildCounter = new base::SharedMemory();
+    size_t shmemSize = NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT * sizeof(int32_t);
+    if (sActiveChildCounter->Create(shmemSize) &&
+        sActiveChildCounter->Map(shmemSize)) {
+      memset(sActiveChildCounter->memory(), 0, shmemSize);
+      sInUseChildCounters[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER] = true;
+      sInUseChildCounters[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] = true;
+      static_cast<Atomic<int32_t>*>(
+          sActiveChildCounter
+              ->memory())[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] =
+          static_cast<int32_t>(sMaxConcurrentIdleTasksInChildProcesses);
+    } else {
+      delete sActiveChildCounter;
+      sActiveChildCounter = nullptr;
+    }
+  }
+  Maybe<SharedMemoryHandle> activeCounter;
+  if (SharedMemoryHandle handle =
+          sActiveChildCounter ? sActiveChildCounter->CloneHandle() : nullptr) {
+    activeCounter.emplace(std::move(handle));
+  }
+
+  uint32_t unusedId = 0;
+  for (uint32_t i = 0; i < NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT; ++i) {
+    if (!sInUseChildCounters[i]) {
+      sInUseChildCounters[i] = true;
+      unusedId = i;
+      break;
+    }
+  }
+
+  // If there wasn't an empty item, we'll fallback to 0.
+  mChildId = unusedId;
+
+  aResolve(std::tuple<mozilla::Maybe<SharedMemoryHandle>&&, const uint32_t&>(
+      std::move(activeCounter), mChildId));
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvRequestIdleTime(uint64_t aId,
+                                                   TimeDuration aBudget) {
+  MOZ_ASSERT(aBudget);
+  MOZ_ASSERT(IsNotDoingIdleTask());
+
+  mCurrentRequestId = aId;
+  mRequestedIdleBudget = aBudget;
+
+  if (!isInList()) {
+    sIdleAndGCRequests.insertBack(this);
+  }
+
+  Schedule(this);
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvIdleTimeUsed(uint64_t aId) {
+  // The client can either signal that they've used the idle time or they're
+  // canceling the request.  We cannot use a seperate cancel message because it
+  // could arrive after the parent has granted the request.
+  MOZ_ASSERT(IsWaitingForIdle() || IsDoingIdleTask());
+
+  // The parent process will always know the ID of the current request (since
+  // the IPC channel is reliable).  The IDs are provided so that the client can
+  // check them (it's possible for the client to race ahead of the server).
+  MOZ_ASSERT(mCurrentRequestId == aId);
+
+  if (IsWaitingForIdle() && !mRequestingGC) {
+    remove();
+  }
+  mRequestedIdleBudget = TimeDuration();
+  Schedule(nullptr);
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvSchedule() {
+  Schedule(nullptr);
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvRunningPrioritizedOperation() {
+  ++mRunningPrioritizedOperation;
+  if (mRunningPrioritizedOperation == 1) {
+    ++sChildProcessesRunningPrioritizedOperation;
+  }
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvPrioritizedOperationDone() {
+  MOZ_ASSERT(mRunningPrioritizedOperation);
+
+  --mRunningPrioritizedOperation;
+  if (mRunningPrioritizedOperation == 0) {
+    --sChildProcessesRunningPrioritizedOperation;
+    Schedule(nullptr);
+  }
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvRequestGC(RequestGCResolver&& aResolver) {
+  MOZ_ASSERT(!mDoingGC);
+  MOZ_ASSERT(!mRequestingGC);
+
+  mRequestingGC = Some(aResolver);
+  if (!isInList()) {
+    sIdleAndGCRequests.insertBack(this);
+  }
+
+  sRecordGCTelemetry = true;
+  sNumWaitingGC++;
+  Schedule(nullptr);
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvStartedGC() {
+  if (mDoingGC) {
+    return IPC_OK();
+  }
+
+  mDoingGC = true;
+  sActiveGCs++;
+
+  if (mRequestingGC) {
+    sNumWaitingGC--;
+    // We have to respond to the request before dropping it, even though the
+    // content process is already doing the GC.
+    mRequestingGC.value()(true);
+    mRequestingGC = Nothing();
+    if (!IsWaitingForIdle()) {
+      remove();
+    }
+    sRecordGCTelemetry = true;
+  }
+
+  return IPC_OK();
+}
+
+IPCResult IdleSchedulerParent::RecvDoneGC() {
+  MOZ_ASSERT(mDoingGC);
+  sActiveGCs--;
+  mDoingGC = false;
+  sRecordGCTelemetry = true;
+  Schedule(nullptr);
+  return IPC_OK();
+}
+
+int32_t IdleSchedulerParent::ActiveCount() {
+  if (sActiveChildCounter) {
+    return (static_cast<Atomic<int32_t>*>(
+        sActiveChildCounter
+            ->memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER]);
+  }
+  return 0;
+}
+
+bool IdleSchedulerParent::HasSpareCycles(int32_t aActiveCount) {
+  // We can run a new task if we have a spare core.  If we're running a
+  // prioritised operation we halve the number of regular spare cores.
+  //
+  // sMaxConcurrentIdleTasksInChildProcesses will always be >0 so on 1 and 2
+  // core systems this will allow 1 idle tasks (0 if running a prioritized
+  // operation).
+  MOZ_ASSERT(sMaxConcurrentIdleTasksInChildProcesses > 0);
+  return sChildProcessesRunningPrioritizedOperation
+             ? sMaxConcurrentIdleTasksInChildProcesses / 2 > aActiveCount
+             : sMaxConcurrentIdleTasksInChildProcesses > aActiveCount;
+}
+
+bool IdleSchedulerParent::HasSpareGCCycles() {
+  return sMaxConcurrentGCs > sActiveGCs;
+}
+
+void IdleSchedulerParent::SendIdleTime() {
+  // We would assert that IsWaitingForIdle() except after potentially removing
+  // the task from it's list this will return false.  Instead check
+  // mRequestedIdleBudget.
+  MOZ_ASSERT(mRequestedIdleBudget);
+  Unused << SendIdleTime(mCurrentRequestId, mRequestedIdleBudget);
+}
+
+void IdleSchedulerParent::SendMayGC() {
+  MOZ_ASSERT(mRequestingGC);
+  mRequestingGC.value()(true);
+  mRequestingGC = Nothing();
+  mDoingGC = true;
+  sActiveGCs++;
+  sRecordGCTelemetry = true;
+  MOZ_ASSERT(sNumWaitingGC > 0);
+  sNumWaitingGC--;
+}
+
+void IdleSchedulerParent::Schedule(IdleSchedulerParent* aRequester) {
+  // Tasks won't update the active count until after they receive their message
+  // and start to run, so make a copy of it here and increment it for every task
+  // we schedule. It will become an estimate of how many tasks will be active
+  // shortly.
+  int32_t activeCount = ActiveCount();
+
+  if (aRequester && aRequester->mRunningPrioritizedOperation) {
+    // Prioritised operations are requested only for idle time requests, so this
+    // must be an idle time request.
+    MOZ_ASSERT(aRequester->IsWaitingForIdle());
+
+    // If the requester is prioritized, just let it run itself.
+    if (aRequester->isInList() && !aRequester->mRequestingGC) {
+      aRequester->remove();
+    }
+    aRequester->SendIdleTime();
+    activeCount++;
+  }
+
+  RefPtr<IdleSchedulerParent> idleRequester = sIdleAndGCRequests.getFirst();
+
+  bool has_spare_cycles = HasSpareCycles(activeCount);
+  bool has_spare_gc_cycles = HasSpareGCCycles();
+
+  while (idleRequester && (has_spare_cycles || has_spare_gc_cycles)) {
+    // Get the next element before potentially removing the current one from the
+    // list.
+    RefPtr<IdleSchedulerParent> next = idleRequester->getNext();
+
+    if (has_spare_cycles && idleRequester->IsWaitingForIdle()) {
+      // We can run an idle task.
+      activeCount++;
+      if (!idleRequester->mRequestingGC) {
+        idleRequester->remove();
+      }
+      idleRequester->SendIdleTime();
+      has_spare_cycles = HasSpareCycles(activeCount);
+    }
+
+    if (has_spare_gc_cycles && idleRequester->mRequestingGC) {
+      if (!idleRequester->IsWaitingForIdle()) {
+        idleRequester->remove();
+      }
+      idleRequester->SendMayGC();
+      has_spare_gc_cycles = HasSpareGCCycles();
+    }
+
+    idleRequester = next;
+  }
+
+  if (!sIdleAndGCRequests.isEmpty() && HasSpareCycles(activeCount)) {
+    EnsureStarvationTimer();
+  }
+
+  if (sRecordGCTelemetry) {
+    sRecordGCTelemetry = false;
+    Telemetry::Accumulate(Telemetry::GC_WAIT_FOR_IDLE_COUNT, sNumWaitingGC);
+  }
+}
+
+void IdleSchedulerParent::EnsureStarvationTimer() {
+  // Even though idle runnables aren't really guaranteed to get run ever (which
+  // is why most of them have the timer fallback), try to not let any child
+  // process' idle handling to starve forever in case other processes are busy
+  if (!sStarvationPreventer) {
+    // Reuse StaticPrefs::page_load_deprioritization_period(), since that
+    // is used on child side when deciding the minimum idle period.
+    NS_NewTimerWithFuncCallback(
+        &sStarvationPreventer, StarvationCallback, nullptr,
+        StaticPrefs::page_load_deprioritization_period(),
+        nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY, "StarvationCallback");
+  }
+}
+
+void IdleSchedulerParent::StarvationCallback(nsITimer* aTimer, void* aData) {
+  RefPtr<IdleSchedulerParent> idleRequester = sIdleAndGCRequests.getFirst();
+  while (idleRequester) {
+    if (idleRequester->IsWaitingForIdle()) {
+      // Treat the first process waiting for idle time as running prioritized
+      // operation so that it gets run.
+      ++idleRequester->mRunningPrioritizedOperation;
+      ++sChildProcessesRunningPrioritizedOperation;
+      Schedule(idleRequester);
+      --idleRequester->mRunningPrioritizedOperation;
+      --sChildProcessesRunningPrioritizedOperation;
+      break;
+    }
+
+    idleRequester = idleRequester->getNext();
+  }
+  NS_RELEASE(sStarvationPreventer);
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/IdleSchedulerParent.h b/ipc/glue/IdleSchedulerParent.h
new file mode 100644
index 0000000000..62cf6fb772
--- /dev/null
+++ b/ipc/glue/IdleSchedulerParent.h
@@ -0,0 +1,137 @@
+/* -*- 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_ipc_IdleSchedulerParent_h__
+#define mozilla_ipc_IdleSchedulerParent_h__
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/ipc/PIdleSchedulerParent.h"
+#include "base/shared_memory.h"
+#include <bitset>
+
+#define NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT 1024
+#define NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER 0
+#define NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER 1
+
+class nsITimer;
+
+namespace mozilla {
+
+namespace ipc {
+
+class BackgroundParentImpl;
+
+class IdleSchedulerParent final
+    : public PIdleSchedulerParent,
+      public LinkedListElement<IdleSchedulerParent> {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(IdleSchedulerParent)
+
+  IPCResult RecvInitForIdleUse(InitForIdleUseResolver&& aResolve);
+  IPCResult RecvRequestIdleTime(uint64_t aId, TimeDuration aBudget);
+  IPCResult RecvIdleTimeUsed(uint64_t aId);
+  IPCResult RecvSchedule();
+  IPCResult RecvRunningPrioritizedOperation();
+  IPCResult RecvPrioritizedOperationDone();
+  IPCResult RecvRequestGC(RequestGCResolver&& aResolve);
+  IPCResult RecvStartedGC();
+  IPCResult RecvDoneGC();
+
+ private:
+  friend class BackgroundParentImpl;
+  IdleSchedulerParent();
+  ~IdleSchedulerParent();
+
+  static void CalculateNumIdleTasks();
+
+  static int32_t ActiveCount();
+  static void Schedule(IdleSchedulerParent* aRequester);
+  static bool HasSpareCycles(int32_t aActiveCount);
+  static bool HasSpareGCCycles();
+  using PIdleSchedulerParent::SendIdleTime;
+  void SendIdleTime();
+  void SendMayGC();
+
+  static void EnsureStarvationTimer();
+  static void StarvationCallback(nsITimer* aTimer, void* aData);
+
+  uint64_t mCurrentRequestId = 0;
+  // For now we don't really use idle budget for scheduling.  Zero if the
+  // process isn't requestiong or running an idle task.
+  TimeDuration mRequestedIdleBudget;
+
+  // Counting all the prioritized operations the process is doing.
+  uint32_t mRunningPrioritizedOperation = 0;
+
+  // Only one of these may be true at a time, giving three states:
+  // No active GC request, A pending GC request, or a granted GC request.
+  Maybe<RequestGCResolver> mRequestingGC;
+  bool mDoingGC = false;
+
+  uint32_t mChildId = 0;
+
+  // Current state, only one of these may be true at a time.
+  bool IsWaitingForIdle() const { return isInList() && mRequestedIdleBudget; }
+  bool IsDoingIdleTask() const { return !isInList() && mRequestedIdleBudget; }
+  bool IsNotDoingIdleTask() const { return !mRequestedIdleBudget; }
+
+  // Shared memory for counting how many child processes are running
+  // tasks. This memory is shared across all the child processes.
+  // The [0] is used for counting all the processes and
+  // [childId] is for counting per process activity.
+  // This way the global activity can be checked in a fast way by just looking
+  // at [0] value.
+  // [1] is used for cpu count for child processes.
+  static base::SharedMemory* sActiveChildCounter;
+  // A bit is set if there is a child with child Id as the offset.
+  // The bit is used to check per child specific activity counters in
+  // sActiveChildCounter.
+  static std::bitset<NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT>
+      sInUseChildCounters;
+
+  // Processes on this list have requested (but the request hasn't yet been
+  // granted) idle time or to start a GC or both.
+  //
+  // Either or both their mRequestedIdleBudget or mRequestingGC fields are
+  // non-zero.  Child processes not on this list have either been granted all
+  // their requests not made a request ever or since they last finished an idle
+  // or GC task.
+  //
+  // Use the methods above to determine a process' idle time state, or check the
+  // mRequestingGC and mDoingGC fields for the GC state.
+  static LinkedList<IdleSchedulerParent> sIdleAndGCRequests;
+
+  static int32_t sMaxConcurrentIdleTasksInChildProcesses;
+  static uint32_t sMaxConcurrentGCs;
+  static uint32_t sActiveGCs;
+
+  // True if we should record some telemetry for GCs in the next Schedule().
+  // This is set to true by either requesting a GC job or scheduling a GC job.
+  static bool sRecordGCTelemetry;
+  // The current number of waiting GCs.
+  static uint32_t sNumWaitingGC;
+
+  // Counting all the child processes which have at least one prioritized
+  // operation.
+  static uint32_t sChildProcessesRunningPrioritizedOperation;
+
+  // When this hits zero, it's time to free the shared memory and pack up.
+  static uint32_t sChildProcessesAlive;
+
+  static nsITimer* sStarvationPreventer;
+
+  static uint32_t sNumCPUs;
+  static uint32_t sPrefConcurrentGCsMax;
+  static uint32_t sPrefConcurrentGCsCPUDivisor;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_IdleSchedulerParent_h__
diff --git a/ipc/glue/InputStreamParams.ipdlh b/ipc/glue/InputStreamParams.ipdlh
new file mode 100644
index 0000000000..8d1f727eca
--- /dev/null
+++ b/ipc/glue/InputStreamParams.ipdlh
@@ -0,0 +1,101 @@
+/* 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 ProtocolTypes;
+
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+[RefCounted] using mozilla::ipc::DataPipeReceiver from "mozilla/ipc/DataPipe.h";
+[RefCounted] using mozilla::RemoteLazyInputStream from "mozilla/RemoteLazyInputStream.h";
+
+namespace mozilla {
+namespace ipc {
+
+struct HeaderEntry
+{
+  nsCString name;
+  nsCString value;
+};
+
+struct StringInputStreamParams
+{
+  nsCString data;
+};
+
+struct FileInputStreamParams
+{
+  FileDescriptor fileDescriptor;
+  int32_t behaviorFlags;
+  int32_t ioFlags;
+};
+
+struct MultiplexInputStreamParams
+{
+  InputStreamParams[] streams;
+  uint32_t currentStream;
+  nsresult status;
+  bool startedReadingCurrent;
+};
+
+struct SlicedInputStreamParams
+{
+  InputStreamParams stream;
+  uint64_t start;
+  uint64_t length;
+  uint64_t curPos;
+  bool closed;
+};
+
+struct RemoteLazyInputStreamParams
+{
+  nullable RemoteLazyInputStream stream;
+};
+
+struct DataPipeReceiverStreamParams
+{
+  nullable DataPipeReceiver pipe;
+};
+
+union InputStreamParams
+{
+  StringInputStreamParams;
+  FileInputStreamParams;
+  BufferedInputStreamParams;
+  MIMEInputStreamParams;
+  MultiplexInputStreamParams;
+  SlicedInputStreamParams;
+  RemoteLazyInputStreamParams;
+  InputStreamLengthWrapperParams;
+  EncryptedFileInputStreamParams;
+  DataPipeReceiverStreamParams;
+};
+
+struct EncryptedFileInputStreamParams
+{
+  FileInputStreamParams fileInputStreamParams;
+  uint8_t[] key;
+  uint32_t blockSize;
+};
+
+struct BufferedInputStreamParams
+{
+  InputStreamParams? optionalStream;
+  uint32_t bufferSize;
+};
+
+struct MIMEInputStreamParams
+{
+  InputStreamParams? optionalStream;
+  HeaderEntry[] headers;
+  bool startedReading;
+};
+
+struct InputStreamLengthWrapperParams
+{
+  InputStreamParams stream;
+  int64_t length;
+  bool consumed;
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/InputStreamUtils.cpp b/ipc/glue/InputStreamUtils.cpp
new file mode 100644
index 0000000000..888afce859
--- /dev/null
+++ b/ipc/glue/InputStreamUtils.cpp
@@ -0,0 +1,211 @@
+/* -*- 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 "InputStreamUtils.h"
+
+#include "nsIIPCSerializableInputStream.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/quota/DecryptingInputStream_impl.h"
+#include "mozilla/dom/quota/IPCStreamCipherStrategy.h"
+#include "mozilla/ipc/DataPipe.h"
+#include "mozilla/InputStreamLengthHelper.h"
+#include "mozilla/RemoteLazyInputStream.h"
+#include "mozilla/RemoteLazyInputStreamChild.h"
+#include "mozilla/RemoteLazyInputStreamStorage.h"
+#include "mozilla/SlicedInputStream.h"
+#include "mozilla/InputStreamLengthWrapper.h"
+#include "nsBufferedStreams.h"
+#include "nsComponentManagerUtils.h"
+#include "nsDebug.h"
+#include "nsFileStreams.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsID.h"
+#include "nsIMIMEInputStream.h"
+#include "nsIMultiplexInputStream.h"
+#include "nsIPipe.h"
+#include "nsMIMEInputStream.h"
+#include "nsMultiplexInputStream.h"
+#include "nsNetCID.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "nsXULAppAPI.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+namespace mozilla {
+namespace ipc {
+
+void InputStreamHelper::SerializedComplexity(nsIInputStream* aInputStream,
+                                             uint32_t aMaxSize,
+                                             uint32_t* aSizeUsed,
+                                             uint32_t* aPipes,
+                                             uint32_t* aTransferables) {
+  MOZ_ASSERT(aInputStream);
+
+  nsCOMPtr<nsIIPCSerializableInputStream> serializable =
+      do_QueryInterface(aInputStream);
+  if (!serializable) {
+    MOZ_CRASH("Input stream is not serializable!");
+  }
+
+  serializable->SerializedComplexity(aMaxSize, aSizeUsed, aPipes,
+                                     aTransferables);
+}
+
+void InputStreamHelper::SerializeInputStream(nsIInputStream* aInputStream,
+                                             InputStreamParams& aParams,
+                                             uint32_t aMaxSize,
+                                             uint32_t* aSizeUsed) {
+  MOZ_ASSERT(aInputStream);
+
+  nsCOMPtr<nsIIPCSerializableInputStream> serializable =
+      do_QueryInterface(aInputStream);
+  if (!serializable) {
+    MOZ_CRASH("Input stream is not serializable!");
+  }
+
+  serializable->Serialize(aParams, aMaxSize, aSizeUsed);
+
+  if (aParams.type() == InputStreamParams::T__None) {
+    MOZ_CRASH("Serialize failed!");
+  }
+}
+
+void InputStreamHelper::SerializeInputStreamAsPipe(nsIInputStream* aInputStream,
+                                                   InputStreamParams& aParams) {
+  MOZ_ASSERT(aInputStream);
+
+  // Let's try to take the length using InputStreamLengthHelper. If the length
+  // cannot be taken synchronously, and its length is needed, the stream needs
+  // to be fully copied in memory on the deserialization side.
+  int64_t length;
+  if (!InputStreamLengthHelper::GetSyncLength(aInputStream, &length)) {
+    length = -1;
+  }
+
+  RefPtr<DataPipeSender> sender;
+  RefPtr<DataPipeReceiver> receiver;
+  nsresult rv = NewDataPipe(kDefaultDataPipeCapacity, getter_AddRefs(sender),
+                            getter_AddRefs(receiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  nsCOMPtr<nsIEventTarget> target =
+      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+
+  rv =
+      NS_AsyncCopy(aInputStream, sender, target, NS_ASYNCCOPY_VIA_WRITESEGMENTS,
+                   kDefaultDataPipeCapacity, nullptr, nullptr);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  aParams = DataPipeReceiverStreamParams(receiver);
+  if (length != -1) {
+    aParams = InputStreamLengthWrapperParams(aParams, length, false);
+  }
+}
+
+already_AddRefed<nsIInputStream> InputStreamHelper::DeserializeInputStream(
+    const InputStreamParams& aParams) {
+  if (aParams.type() == InputStreamParams::TRemoteLazyInputStreamParams) {
+    const RemoteLazyInputStreamParams& params =
+        aParams.get_RemoteLazyInputStreamParams();
+
+    // If the RemoteLazyInputStream already has an internal stream, unwrap it.
+    // This is required as some code unfortunately depends on the precise
+    // topology of received streams, and cannot handle being passed a
+    // `RemoteLazyInputStream` in the parent process.
+    nsCOMPtr<nsIInputStream> innerStream;
+    if (XRE_IsParentProcess() &&
+        NS_SUCCEEDED(
+            params.stream()->TakeInternalStream(getter_AddRefs(innerStream)))) {
+      return innerStream.forget();
+    }
+    return do_AddRef(params.stream());
+  }
+
+  if (aParams.type() == InputStreamParams::TDataPipeReceiverStreamParams) {
+    const DataPipeReceiverStreamParams& pipeParams =
+        aParams.get_DataPipeReceiverStreamParams();
+    return do_AddRef(pipeParams.pipe());
+  }
+
+  nsCOMPtr<nsIIPCSerializableInputStream> serializable;
+
+  switch (aParams.type()) {
+    case InputStreamParams::TStringInputStreamParams: {
+      nsCOMPtr<nsIInputStream> stream;
+      NS_NewCStringInputStream(getter_AddRefs(stream), ""_ns);
+      serializable = do_QueryInterface(stream);
+    } break;
+
+    case InputStreamParams::TFileInputStreamParams: {
+      nsCOMPtr<nsIFileInputStream> stream;
+      nsFileInputStream::Create(NS_GET_IID(nsIFileInputStream),
+                                getter_AddRefs(stream));
+      serializable = do_QueryInterface(stream);
+    } break;
+
+    case InputStreamParams::TBufferedInputStreamParams: {
+      nsCOMPtr<nsIBufferedInputStream> stream;
+      nsBufferedInputStream::Create(NS_GET_IID(nsIBufferedInputStream),
+                                    getter_AddRefs(stream));
+      serializable = do_QueryInterface(stream);
+    } break;
+
+    case InputStreamParams::TMIMEInputStreamParams: {
+      nsCOMPtr<nsIMIMEInputStream> stream;
+      nsMIMEInputStreamConstructor(NS_GET_IID(nsIMIMEInputStream),
+                                   getter_AddRefs(stream));
+      serializable = do_QueryInterface(stream);
+    } break;
+
+    case InputStreamParams::TMultiplexInputStreamParams: {
+      nsCOMPtr<nsIMultiplexInputStream> stream;
+      nsMultiplexInputStreamConstructor(NS_GET_IID(nsIMultiplexInputStream),
+                                        getter_AddRefs(stream));
+      serializable = do_QueryInterface(stream);
+    } break;
+
+    case InputStreamParams::TSlicedInputStreamParams:
+      serializable = new SlicedInputStream();
+      break;
+
+    case InputStreamParams::TInputStreamLengthWrapperParams:
+      serializable = new InputStreamLengthWrapper();
+      break;
+
+    case InputStreamParams::TEncryptedFileInputStreamParams:
+      serializable = new dom::quota::DecryptingInputStream<
+          dom::quota::IPCStreamCipherStrategy>();
+      break;
+
+    default:
+      MOZ_ASSERT(false, "Unknown params!");
+      return nullptr;
+  }
+
+  MOZ_ASSERT(serializable);
+
+  if (!serializable->Deserialize(aParams)) {
+    MOZ_ASSERT(false, "Deserialize failed!");
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIInputStream> stream = do_QueryInterface(serializable);
+  MOZ_ASSERT(stream);
+
+  return stream.forget();
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/InputStreamUtils.h b/ipc/glue/InputStreamUtils.h
new file mode 100644
index 0000000000..27a65b02e2
--- /dev/null
+++ b/ipc/glue/InputStreamUtils.h
@@ -0,0 +1,50 @@
+/* -*- 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_ipc_InputStreamUtils_h
+#define mozilla_ipc_InputStreamUtils_h
+
+#include "mozilla/ipc/InputStreamParams.h"
+#include "nsCOMPtr.h"
+#include "nsIInputStream.h"
+#include "nsTArray.h"
+
+namespace mozilla {
+namespace ipc {
+
+class FileDescriptor;
+
+// If you want to serialize an inputStream, please use SerializeIPCStream or
+// nsIInputStream directly.
+class InputStreamHelper {
+ public:
+  static void SerializedComplexity(nsIInputStream* aInputStream,
+                                   uint32_t aMaxSize, uint32_t* aSizeUsed,
+                                   uint32_t* aPipes, uint32_t* aTransferables);
+
+  // These 2 methods allow to serialize an inputStream into InputStreamParams.
+  // The manager is needed in case a stream needs to serialize itself as
+  // IPCRemoteStream.
+  // The stream serializes itself fully only if the resulting IPC message will
+  // be smaller than |aMaxSize|. Otherwise, the stream serializes itself as a
+  // DataPipe, and, its content will be sent to the other side of the IPC pipe
+  // in chunks. The IPC message size is returned into |aSizeUsed|.
+  static void SerializeInputStream(nsIInputStream* aInputStream,
+                                   InputStreamParams& aParams,
+                                   uint32_t aMaxSize, uint32_t* aSizeUsed);
+
+  // When a stream wants to serialize itself as a DataPipe, it uses this method.
+  static void SerializeInputStreamAsPipe(nsIInputStream* aInputStream,
+                                         InputStreamParams& aParams);
+
+  static already_AddRefed<nsIInputStream> DeserializeInputStream(
+      const InputStreamParams& aParams);
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_InputStreamUtils_h
diff --git a/ipc/glue/LaunchError.cpp b/ipc/glue/LaunchError.cpp
new file mode 100644
index 0000000000..04ae34cfa6
--- /dev/null
+++ b/ipc/glue/LaunchError.cpp
@@ -0,0 +1,31 @@
+/* -*- 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 "LaunchError.h"
+
+#if defined(XP_WIN)
+#  include "mozilla/WinHeaderOnlyUtils.h"
+#endif
+
+namespace mozilla::ipc {
+
+LaunchError::LaunchError(const char* aFunction, OsError aError)
+    : mFunction(aFunction), mError(aError) {}
+
+#if defined(XP_WIN)
+LaunchError::LaunchError(const char* aFunction, PRErrorCode aError)
+    : mFunction(aFunction), mError((int)aError) {}
+
+LaunchError::LaunchError(const char* aFunction, DWORD aError)
+    : mFunction(aFunction),
+      mError(WindowsError::FromWin32Error(aError).AsHResult()) {}
+#endif  // defined(XP_WIN)
+
+const char* LaunchError::FunctionName() const { return mFunction; }
+
+OsError LaunchError::ErrorCode() const { return mError; }
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/LaunchError.h b/ipc/glue/LaunchError.h
new file mode 100644
index 0000000000..efa8ba4de4
--- /dev/null
+++ b/ipc/glue/LaunchError.h
@@ -0,0 +1,40 @@
+/* -*- 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_ipc_LaunchError_h
+#define mozilla_ipc_LaunchError_h
+
+#include "prerror.h"
+
+#if defined(XP_WIN)
+#  include <windows.h>
+#  include <winerror.h>
+using OsError = HRESULT;
+#else
+using OsError = int;
+#endif
+
+namespace mozilla::ipc {
+
+class LaunchError {
+ public:
+  explicit LaunchError(const char* aFunction, OsError aError = 0);
+#if defined(XP_WIN)
+  explicit LaunchError(const char* aFunction, PRErrorCode aError);
+  explicit LaunchError(const char* aFunction, DWORD aError);
+#endif  // defined(XP_WIN)
+
+  const char* FunctionName() const;
+  OsError ErrorCode() const;
+
+ private:
+  const char* mFunction;
+  OsError mError;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // ifndef mozilla_ipc_LaunchError_h
diff --git a/ipc/glue/LibrarySandboxPreload.cpp b/ipc/glue/LibrarySandboxPreload.cpp
new file mode 100644
index 0000000000..0d7889d461
--- /dev/null
+++ b/ipc/glue/LibrarySandboxPreload.cpp
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LibrarySandboxPreload.h"
+#include "nsXPCOMPrivate.h"  // for XPCOM_DLL
+
+#include "BinaryPath.h"
+#include "prlink.h"
+
+namespace mozilla {
+namespace ipc {
+
+PathString GetSandboxedRLBoxPath() {
+  nsCOMPtr<nsIFile> libFile;
+  nsresult rv = mozilla::BinaryPath::GetFile(getter_AddRefs(libFile));
+  if (NS_FAILED(rv)) {
+    MOZ_CRASH("Library preload failure: Failed to get binary file\n");
+  }
+
+  rv = libFile->SetNativeLeafName(XPCOM_DLL ""_ns);
+  if (NS_FAILED(rv)) {
+    MOZ_CRASH("Library preload failure: Failed to get library file\n");
+  }
+
+  return libFile->NativePath();
+}
+
+PRLibrary* PreloadLibrary(const PathString& path) {
+  PRLibSpec libSpec;
+#ifdef XP_WIN
+  libSpec.type = PR_LibSpec_PathnameU;
+  libSpec.value.pathname_u = path.get();
+#else
+  libSpec.type = PR_LibSpec_Pathname;
+  libSpec.value.pathname = path.get();
+#endif
+  PRLibrary* ret = PR_LoadLibraryWithFlags(libSpec, PR_LD_LAZY);
+  return ret;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/LibrarySandboxPreload.h b/ipc/glue/LibrarySandboxPreload.h
new file mode 100644
index 0000000000..6be91c605b
--- /dev/null
+++ b/ipc/glue/LibrarySandboxPreload.h
@@ -0,0 +1,18 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=4 et :
+ */
+/* 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 ipc_glue_LibrarySandboxPreload_h
+#define ipc_glue_LibrarySandboxPreload_h
+
+#include "mozilla/FileUtils.h"
+
+namespace mozilla {
+namespace ipc {
+PathString GetSandboxedRLBoxPath();
+}  // namespace ipc
+}  // namespace mozilla
+#endif
diff --git a/ipc/glue/MessageChannel.cpp b/ipc/glue/MessageChannel.cpp
new file mode 100644
index 0000000000..ea01c54f0d
--- /dev/null
+++ b/ipc/glue/MessageChannel.cpp
@@ -0,0 +1,2482 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=4 et :
+ */
+/* 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/ipc/MessageChannel.h"
+
+#include <math.h>
+
+#include <utility>
+
+#include "CrashAnnotations.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Fuzzing.h"
+#include "mozilla/IntentionalCrash.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/ipc/NodeController.h"
+#include "mozilla/ipc/ProcessChild.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "nsAppRunner.h"
+#include "nsContentUtils.h"
+#include "nsIDirectTaskDispatcher.h"
+#include "nsTHashMap.h"
+#include "nsDebug.h"
+#include "nsExceptionHandler.h"
+#include "nsIMemoryReporter.h"
+#include "nsISupportsImpl.h"
+#include "nsPrintfCString.h"
+#include "nsThreadUtils.h"
+
+#ifdef OS_WIN
+#  include "mozilla/gfx/Logging.h"
+#endif
+
+#ifdef FUZZING_SNAPSHOT
+#  include "mozilla/fuzzing/IPCFuzzController.h"
+#endif
+
+// Undo the damage done by mozzconf.h
+#undef compress
+
+static mozilla::LazyLogModule sLogModule("ipc");
+#define IPC_LOG(...) MOZ_LOG(sLogModule, LogLevel::Debug, (__VA_ARGS__))
+
+/*
+ * IPC design:
+ *
+ * There are two kinds of messages: async and sync. Sync messages are blocking.
+ *
+ * Terminology: To dispatch a message Foo is to run the RecvFoo code for
+ * it. This is also called "handling" the message.
+ *
+ * Sync and async messages can sometimes "nest" inside other sync messages
+ * (i.e., while waiting for the sync reply, we can dispatch the inner
+ * message). The three possible nesting levels are NOT_NESTED,
+ * NESTED_INSIDE_SYNC, and NESTED_INSIDE_CPOW.  The intended uses are:
+ *   NOT_NESTED - most messages.
+ *   NESTED_INSIDE_SYNC - CPOW-related messages, which are always sync
+ *                        and can go in either direction.
+ *   NESTED_INSIDE_CPOW - messages where we don't want to dispatch
+ *                        incoming CPOWs while waiting for the response.
+ * These nesting levels are ordered: NOT_NESTED, NESTED_INSIDE_SYNC,
+ * NESTED_INSIDE_CPOW.  Async messages cannot be NESTED_INSIDE_SYNC but they can
+ * be NESTED_INSIDE_CPOW.
+ *
+ * To avoid jank, the parent process is not allowed to send NOT_NESTED sync
+ * messages. When a process is waiting for a response to a sync message M0, it
+ * will dispatch an incoming message M if:
+ *   1. M has a higher nesting level than M0, or
+ *   2. if M has the same nesting level as M0 and we're in the child, or
+ *   3. if M has the same nesting level as M0 and it was sent by the other side
+ *      while dispatching M0.
+ * The idea is that messages with higher nesting should take precendence. The
+ * purpose of rule 2 is to handle a race where both processes send to each other
+ * simultaneously. In this case, we resolve the race in favor of the parent (so
+ * the child dispatches first).
+ *
+ * Messages satisfy the following properties:
+ *   A. When waiting for a response to a sync message, we won't dispatch any
+ *      messages of a lower nesting level.
+ *   B. Messages of the same nesting level will be dispatched roughly in the
+ *      order they were sent. The exception is when the parent and child send
+ *      sync messages to each other simulataneously. In this case, the parent's
+ *      message is dispatched first. While it is dispatched, the child may send
+ *      further nested messages, and these messages may be dispatched before the
+ *      child's original message. We can consider ordering to be preserved here
+ *      because we pretend that the child's original message wasn't sent until
+ *      after the parent's message is finished being dispatched.
+ *
+ * When waiting for a sync message reply, we dispatch an async message only if
+ * it is NESTED_INSIDE_CPOW. Normally NESTED_INSIDE_CPOW async
+ * messages are sent only from the child. However, the parent can send
+ * NESTED_INSIDE_CPOW async messages when it is creating a bridged protocol.
+ */
+
+using namespace mozilla;
+using namespace mozilla::ipc;
+
+using mozilla::MonitorAutoLock;
+using mozilla::MonitorAutoUnlock;
+using mozilla::dom::AutoNoJSAPI;
+
+#define IPC_ASSERT(_cond, ...)                                           \
+  do {                                                                   \
+    AssertWorkerThread();                                                \
+    mMonitor->AssertCurrentThreadOwns();                                 \
+    if (!(_cond)) DebugAbort(__FILE__, __LINE__, #_cond, ##__VA_ARGS__); \
+  } while (0)
+
+static MessageChannel* gParentProcessBlocker = nullptr;
+
+namespace mozilla {
+namespace ipc {
+
+static const uint32_t kMinTelemetryMessageSize = 4096;
+
+// Note: we round the time we spend waiting for a response to the nearest
+// millisecond. So a min value of 1 ms actually captures from 500us and above.
+// This is used for both the sending and receiving side telemetry for sync IPC,
+// (IPC_SYNC_MAIN_LATENCY_MS and IPC_SYNC_RECEIVE_MS).
+static const uint32_t kMinTelemetrySyncIPCLatencyMs = 1;
+
+// static
+bool MessageChannel::sIsPumpingMessages = false;
+
+class AutoEnterTransaction {
+ public:
+  explicit AutoEnterTransaction(MessageChannel* aChan, int32_t aMsgSeqno,
+                                int32_t aTransactionID, int aNestedLevel)
+      MOZ_REQUIRES(*aChan->mMonitor)
+      : mChan(aChan),
+        mActive(true),
+        mOutgoing(true),
+        mNestedLevel(aNestedLevel),
+        mSeqno(aMsgSeqno),
+        mTransaction(aTransactionID),
+        mNext(mChan->mTransactionStack) {
+    mChan->mMonitor->AssertCurrentThreadOwns();
+    mChan->mTransactionStack = this;
+  }
+
+  explicit AutoEnterTransaction(MessageChannel* aChan,
+                                const IPC::Message& aMessage)
+      MOZ_REQUIRES(*aChan->mMonitor)
+      : mChan(aChan),
+        mActive(true),
+        mOutgoing(false),
+        mNestedLevel(aMessage.nested_level()),
+        mSeqno(aMessage.seqno()),
+        mTransaction(aMessage.transaction_id()),
+        mNext(mChan->mTransactionStack) {
+    mChan->mMonitor->AssertCurrentThreadOwns();
+
+    if (!aMessage.is_sync()) {
+      mActive = false;
+      return;
+    }
+
+    mChan->mTransactionStack = this;
+  }
+
+  ~AutoEnterTransaction() {
+    mChan->mMonitor->AssertCurrentThreadOwns();
+    if (mActive) {
+      mChan->mTransactionStack = mNext;
+    }
+  }
+
+  void Cancel() {
+    mChan->mMonitor->AssertCurrentThreadOwns();
+    AutoEnterTransaction* cur = mChan->mTransactionStack;
+    MOZ_RELEASE_ASSERT(cur == this);
+    while (cur && cur->mNestedLevel != IPC::Message::NOT_NESTED) {
+      // Note that, in the following situation, we will cancel multiple
+      // transactions:
+      // 1. Parent sends NESTED_INSIDE_SYNC message P1 to child.
+      // 2. Child sends NESTED_INSIDE_SYNC message C1 to child.
+      // 3. Child dispatches P1, parent blocks.
+      // 4. Child cancels.
+      // In this case, both P1 and C1 are cancelled. The parent will
+      // remove C1 from its queue when it gets the cancellation message.
+      MOZ_RELEASE_ASSERT(cur->mActive);
+      cur->mActive = false;
+      cur = cur->mNext;
+    }
+
+    mChan->mTransactionStack = cur;
+
+    MOZ_RELEASE_ASSERT(IsComplete());
+  }
+
+  bool AwaitingSyncReply() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    if (mOutgoing) {
+      return true;
+    }
+    return mNext ? mNext->AwaitingSyncReply() : false;
+  }
+
+  int AwaitingSyncReplyNestedLevel() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    if (mOutgoing) {
+      return mNestedLevel;
+    }
+    return mNext ? mNext->AwaitingSyncReplyNestedLevel() : 0;
+  }
+
+  bool DispatchingSyncMessage() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    if (!mOutgoing) {
+      return true;
+    }
+    return mNext ? mNext->DispatchingSyncMessage() : false;
+  }
+
+  int DispatchingSyncMessageNestedLevel() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    if (!mOutgoing) {
+      return mNestedLevel;
+    }
+    return mNext ? mNext->DispatchingSyncMessageNestedLevel() : 0;
+  }
+
+  int NestedLevel() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    return mNestedLevel;
+  }
+
+  int32_t SequenceNumber() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    return mSeqno;
+  }
+
+  int32_t TransactionID() const {
+    MOZ_RELEASE_ASSERT(mActive);
+    return mTransaction;
+  }
+
+  void ReceivedReply(UniquePtr<IPC::Message> aMessage) {
+    MOZ_RELEASE_ASSERT(aMessage->seqno() == mSeqno);
+    MOZ_RELEASE_ASSERT(aMessage->transaction_id() == mTransaction);
+    MOZ_RELEASE_ASSERT(!mReply);
+    IPC_LOG("Reply received on worker thread: seqno=%d", mSeqno);
+    mReply = std::move(aMessage);
+    MOZ_RELEASE_ASSERT(IsComplete());
+  }
+
+  void HandleReply(UniquePtr<IPC::Message> aMessage) {
+    mChan->mMonitor->AssertCurrentThreadOwns();
+    AutoEnterTransaction* cur = mChan->mTransactionStack;
+    MOZ_RELEASE_ASSERT(cur == this);
+    while (cur) {
+      MOZ_RELEASE_ASSERT(cur->mActive);
+      if (aMessage->seqno() == cur->mSeqno) {
+        cur->ReceivedReply(std::move(aMessage));
+        break;
+      }
+      cur = cur->mNext;
+      MOZ_RELEASE_ASSERT(cur);
+    }
+  }
+
+  bool IsComplete() { return !mActive || mReply; }
+
+  bool IsOutgoing() { return mOutgoing; }
+
+  bool IsCanceled() { return !mActive; }
+
+  bool IsBottom() const { return !mNext; }
+
+  bool IsError() {
+    MOZ_RELEASE_ASSERT(mReply);
+    return mReply->is_reply_error();
+  }
+
+  UniquePtr<IPC::Message> GetReply() { return std::move(mReply); }
+
+ private:
+  MessageChannel* mChan;
+
+  // Active is true if this transaction is on the mChan->mTransactionStack
+  // stack. Generally we're not on the stack if the transaction was canceled
+  // or if it was for a message that doesn't require transactions (an async
+  // message).
+  bool mActive;
+
+  // Is this stack frame for an outgoing message?
+  bool mOutgoing;
+
+  // Properties of the message being sent/received.
+  int mNestedLevel;
+  int32_t mSeqno;
+  int32_t mTransaction;
+
+  // Next item in mChan->mTransactionStack.
+  AutoEnterTransaction* mNext;
+
+  // Pointer the a reply received for this message, if one was received.
+  UniquePtr<IPC::Message> mReply;
+};
+
+class PendingResponseReporter final : public nsIMemoryReporter {
+  ~PendingResponseReporter() = default;
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  NS_IMETHOD
+  CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
+                 bool aAnonymize) override {
+    MOZ_COLLECT_REPORT(
+        "unresolved-ipc-responses", KIND_OTHER, UNITS_COUNT,
+        MessageChannel::gUnresolvedResponses,
+        "Outstanding IPC async message responses that are still not resolved.");
+    return NS_OK;
+  }
+};
+
+NS_IMPL_ISUPPORTS(PendingResponseReporter, nsIMemoryReporter)
+
+class ChannelCountReporter final : public nsIMemoryReporter {
+  ~ChannelCountReporter() = default;
+
+  struct ChannelCounts {
+    size_t mNow;
+    size_t mMax;
+
+    ChannelCounts() : mNow(0), mMax(0) {}
+
+    void Inc() {
+      ++mNow;
+      if (mMax < mNow) {
+        mMax = mNow;
+      }
+    }
+
+    void Dec() {
+      MOZ_ASSERT(mNow > 0);
+      --mNow;
+    }
+  };
+
+  using CountTable = nsTHashMap<nsDepCharHashKey, ChannelCounts>;
+
+  static StaticMutex sChannelCountMutex;
+  static CountTable* sChannelCounts MOZ_GUARDED_BY(sChannelCountMutex);
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  NS_IMETHOD
+  CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
+                 bool aAnonymize) override {
+    AutoTArray<std::pair<const char*, ChannelCounts>, 16> counts;
+    {
+      StaticMutexAutoLock countLock(sChannelCountMutex);
+      if (!sChannelCounts) {
+        return NS_OK;
+      }
+      counts.SetCapacity(sChannelCounts->Count());
+      for (const auto& entry : *sChannelCounts) {
+        counts.AppendElement(std::pair{entry.GetKey(), entry.GetData()});
+      }
+    }
+
+    for (const auto& entry : counts) {
+      nsPrintfCString pathNow("ipc-channels/%s", entry.first);
+      nsPrintfCString pathMax("ipc-channels-peak/%s", entry.first);
+      nsPrintfCString descNow(
+          "Number of IPC channels for"
+          " top-level actor type %s",
+          entry.first);
+      nsPrintfCString descMax(
+          "Peak number of IPC channels for"
+          " top-level actor type %s",
+          entry.first);
+
+      aHandleReport->Callback(""_ns, pathNow, KIND_OTHER, UNITS_COUNT,
+                              entry.second.mNow, descNow, aData);
+      aHandleReport->Callback(""_ns, pathMax, KIND_OTHER, UNITS_COUNT,
+                              entry.second.mMax, descMax, aData);
+    }
+    return NS_OK;
+  }
+
+  static void Increment(const char* aName) {
+    StaticMutexAutoLock countLock(sChannelCountMutex);
+    if (!sChannelCounts) {
+      sChannelCounts = new CountTable;
+    }
+    sChannelCounts->LookupOrInsert(aName).Inc();
+  }
+
+  static void Decrement(const char* aName) {
+    StaticMutexAutoLock countLock(sChannelCountMutex);
+    MOZ_ASSERT(sChannelCounts);
+    sChannelCounts->LookupOrInsert(aName).Dec();
+  }
+};
+
+StaticMutex ChannelCountReporter::sChannelCountMutex;
+ChannelCountReporter::CountTable* ChannelCountReporter::sChannelCounts;
+
+NS_IMPL_ISUPPORTS(ChannelCountReporter, nsIMemoryReporter)
+
+// In child processes, the first MessageChannel is created before
+// XPCOM is initialized enough to construct the memory reporter
+// manager.  This retries every time a MessageChannel is constructed,
+// which is good enough in practice.
+template <class Reporter>
+static void TryRegisterStrongMemoryReporter() {
+  static Atomic<bool> registered;
+  if (registered.compareExchange(false, true)) {
+    RefPtr<Reporter> reporter = new Reporter();
+    if (NS_FAILED(RegisterStrongMemoryReporter(reporter))) {
+      registered = false;
+    }
+  }
+}
+
+Atomic<size_t> MessageChannel::gUnresolvedResponses;
+
+MessageChannel::MessageChannel(const char* aName, IToplevelProtocol* aListener)
+    : mName(aName), mListener(aListener), mMonitor(new RefCountedMonitor()) {
+  MOZ_COUNT_CTOR(ipc::MessageChannel);
+
+#ifdef OS_WIN
+  mEvent = CreateEventW(nullptr, TRUE, FALSE, nullptr);
+  MOZ_RELEASE_ASSERT(mEvent, "CreateEvent failed! Nothing is going to work!");
+#endif
+
+  TryRegisterStrongMemoryReporter<PendingResponseReporter>();
+  TryRegisterStrongMemoryReporter<ChannelCountReporter>();
+}
+
+MessageChannel::~MessageChannel() {
+  MOZ_COUNT_DTOR(ipc::MessageChannel);
+  MonitorAutoLock lock(*mMonitor);
+  MOZ_RELEASE_ASSERT(!mOnCxxStack,
+                     "MessageChannel destroyed while code on CxxStack");
+#ifdef OS_WIN
+  if (mEvent) {
+    BOOL ok = CloseHandle(mEvent);
+    mEvent = nullptr;
+
+    if (!ok) {
+      gfxDevCrash(mozilla::gfx::LogReason::MessageChannelCloseFailure)
+          << "MessageChannel failed to close. GetLastError: " << GetLastError();
+    }
+    MOZ_RELEASE_ASSERT(ok);
+  } else {
+    gfxDevCrash(mozilla::gfx::LogReason::MessageChannelCloseFailure)
+        << "MessageChannel destructor ran without an mEvent Handle";
+  }
+#endif
+
+  // Make sure that the MessageChannel was closed (and therefore cleared) before
+  // it was destroyed. We can't properly close the channel at this point, as it
+  // would be unsafe to invoke our listener's callbacks, and we may be being
+  // destroyed on a thread other than `mWorkerThread`.
+  if (!IsClosedLocked()) {
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCFatalErrorProtocol,
+        nsDependentCString(mName));
+    switch (mChannelState) {
+      case ChannelConnected:
+        MOZ_CRASH(
+            "MessageChannel destroyed without being closed "
+            "(mChannelState == ChannelConnected).");
+        break;
+      case ChannelClosing:
+        MOZ_CRASH(
+            "MessageChannel destroyed without being closed "
+            "(mChannelState == ChannelClosing).");
+        break;
+      case ChannelError:
+        MOZ_CRASH(
+            "MessageChannel destroyed without being closed "
+            "(mChannelState == ChannelError).");
+        break;
+      default:
+        MOZ_CRASH("MessageChannel destroyed without being closed.");
+    }
+  }
+
+  // Double-check other properties for thoroughness.
+  MOZ_RELEASE_ASSERT(!mLink);
+  MOZ_RELEASE_ASSERT(mPendingResponses.empty());
+  MOZ_RELEASE_ASSERT(!mChannelErrorTask);
+  MOZ_RELEASE_ASSERT(mPending.isEmpty());
+  MOZ_RELEASE_ASSERT(!mShutdownTask);
+}
+
+#ifdef DEBUG
+void MessageChannel::AssertMaybeDeferredCountCorrect() {
+  mMonitor->AssertCurrentThreadOwns();
+
+  size_t count = 0;
+  for (MessageTask* task : mPending) {
+    task->AssertMonitorHeld(*mMonitor);
+    if (!IsAlwaysDeferred(*task->Msg())) {
+      count++;
+    }
+  }
+
+  MOZ_ASSERT(count == mMaybeDeferredPendingCount);
+}
+#endif
+
+// This function returns the current transaction ID. Since the notion of a
+// "current transaction" can be hard to define when messages race with each
+// other and one gets canceled and the other doesn't, we require that this
+// function is only called when the current transaction is known to be for a
+// NESTED_INSIDE_SYNC message. In that case, we know for sure what the caller is
+// looking for.
+int32_t MessageChannel::CurrentNestedInsideSyncTransaction() const {
+  mMonitor->AssertCurrentThreadOwns();
+  if (!mTransactionStack) {
+    return 0;
+  }
+  MOZ_RELEASE_ASSERT(mTransactionStack->NestedLevel() ==
+                     IPC::Message::NESTED_INSIDE_SYNC);
+  return mTransactionStack->TransactionID();
+}
+
+bool MessageChannel::AwaitingSyncReply() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return mTransactionStack ? mTransactionStack->AwaitingSyncReply() : false;
+}
+
+int MessageChannel::AwaitingSyncReplyNestedLevel() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return mTransactionStack ? mTransactionStack->AwaitingSyncReplyNestedLevel()
+                           : 0;
+}
+
+bool MessageChannel::DispatchingSyncMessage() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return mTransactionStack ? mTransactionStack->DispatchingSyncMessage()
+                           : false;
+}
+
+int MessageChannel::DispatchingSyncMessageNestedLevel() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return mTransactionStack
+             ? mTransactionStack->DispatchingSyncMessageNestedLevel()
+             : 0;
+}
+
+static const char* StringFromIPCSide(Side side) {
+  switch (side) {
+    case ChildSide:
+      return "Child";
+    case ParentSide:
+      return "Parent";
+    default:
+      return "Unknown";
+  }
+}
+
+static void PrintErrorMessage(Side side, const char* channelName,
+                              const char* msg) {
+  printf_stderr("\n###!!! [%s][%s] Error: %s\n\n", StringFromIPCSide(side),
+                channelName, msg);
+}
+
+bool MessageChannel::Connected() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return ChannelConnected == mChannelState;
+}
+
+bool MessageChannel::ConnectedOrClosing() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return ChannelConnected == mChannelState || ChannelClosing == mChannelState;
+}
+
+bool MessageChannel::CanSend() const {
+  if (!mMonitor) {
+    return false;
+  }
+  MonitorAutoLock lock(*mMonitor);
+  return Connected();
+}
+
+void MessageChannel::Clear() {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+  MOZ_DIAGNOSTIC_ASSERT(IsClosedLocked(), "MessageChannel cleared too early?");
+  MOZ_ASSERT(ChannelClosed == mChannelState || ChannelError == mChannelState);
+
+  // Don't clear mWorkerThread; we use it in AssertWorkerThread().
+  //
+  // Also don't clear mListener.  If we clear it, then sending a message
+  // through this channel after it's Clear()'ed can cause this process to
+  // crash.
+
+  if (mShutdownTask) {
+    mShutdownTask->Clear();
+    mWorkerThread->UnregisterShutdownTask(mShutdownTask);
+  }
+  mShutdownTask = nullptr;
+
+  if (NS_IsMainThread() && gParentProcessBlocker == this) {
+    gParentProcessBlocker = nullptr;
+  }
+
+  gUnresolvedResponses -= mPendingResponses.size();
+  {
+    CallbackMap map = std::move(mPendingResponses);
+    MonitorAutoUnlock unlock(*mMonitor);
+    for (auto& pair : map) {
+      pair.second->Reject(ResponseRejectReason::ChannelClosed);
+    }
+  }
+  mPendingResponses.clear();
+
+  SetIsCrossProcess(false);
+
+  mLink = nullptr;
+
+  if (mChannelErrorTask) {
+    mChannelErrorTask->Cancel();
+    mChannelErrorTask = nullptr;
+  }
+
+  if (mFlushLazySendTask) {
+    mFlushLazySendTask->Cancel();
+    mFlushLazySendTask = nullptr;
+  }
+
+  // Free up any memory used by pending messages.
+  mPending.clear();
+
+  mMaybeDeferredPendingCount = 0;
+}
+
+bool MessageChannel::Open(ScopedPort aPort, Side aSide,
+                          const nsID& aMessageChannelId,
+                          nsISerialEventTarget* aEventTarget) {
+  nsCOMPtr<nsISerialEventTarget> eventTarget =
+      aEventTarget ? aEventTarget : GetCurrentSerialEventTarget();
+  MOZ_RELEASE_ASSERT(eventTarget,
+                     "Must open MessageChannel on a nsISerialEventTarget");
+  MOZ_RELEASE_ASSERT(eventTarget->IsOnCurrentThread(),
+                     "Must open MessageChannel from worker thread");
+
+  auto shutdownTask = MakeRefPtr<WorkerTargetShutdownTask>(eventTarget, this);
+  nsresult rv = eventTarget->RegisterShutdownTask(shutdownTask);
+  MOZ_ASSERT(rv != NS_ERROR_NOT_IMPLEMENTED,
+             "target for MessageChannel must support shutdown tasks");
+  if (rv == NS_ERROR_UNEXPECTED) {
+    // If shutdown tasks have already started running, dispatch our shutdown
+    // task manually.
+    NS_WARNING("Opening MessageChannel on EventTarget in shutdown");
+    rv = eventTarget->Dispatch(shutdownTask->AsRunnable());
+  }
+  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv),
+                     "error registering ShutdownTask for MessageChannel");
+
+  {
+    MonitorAutoLock lock(*mMonitor);
+    MOZ_RELEASE_ASSERT(!mLink, "Open() called > once");
+    MOZ_RELEASE_ASSERT(ChannelClosed == mChannelState, "Not currently closed");
+    MOZ_ASSERT(mSide == UnknownSide);
+
+    mMessageChannelId = aMessageChannelId;
+    mWorkerThread = eventTarget;
+    mShutdownTask = shutdownTask;
+    mLink = MakeUnique<PortLink>(this, std::move(aPort));
+    mChannelState = ChannelConnected;
+    mSide = aSide;
+  }
+
+  // Notify our listener that the underlying IPC channel has been established.
+  // IProtocol will use this callback to create the ActorLifecycleProxy, and
+  // perform an `AddRef` call to keep the actor alive until the channel is
+  // disconnected.
+  //
+  // We unlock our monitor before calling `OnIPCChannelOpened` to ensure that
+  // any calls back into `MessageChannel` do not deadlock. At this point, we may
+  // be receiving messages on the IO thread, however we cannot process them on
+  // the worker thread or have notified our listener until after this function
+  // returns.
+  mListener->OnIPCChannelOpened();
+  return true;
+}
+
+static Side GetOppSide(Side aSide) {
+  switch (aSide) {
+    case ChildSide:
+      return ParentSide;
+    case ParentSide:
+      return ChildSide;
+    default:
+      return UnknownSide;
+  }
+}
+
+bool MessageChannel::Open(MessageChannel* aTargetChan,
+                          nsISerialEventTarget* aEventTarget, Side aSide) {
+  // Opens a connection to another thread in the same process.
+
+  MOZ_ASSERT(aTargetChan, "Need a target channel");
+
+  nsID channelId = nsID::GenerateUUID();
+
+  std::pair<ScopedPort, ScopedPort> ports =
+      NodeController::GetSingleton()->CreatePortPair();
+
+  // NOTE: This dispatch must be sync as it captures locals by non-owning
+  // reference, however we can't use `NS_DispatchAndSpinEventLoopUntilComplete`
+  // as that will spin a nested event loop, and doesn't work with certain types
+  // of calling event targets.
+  base::WaitableEvent event(/* manual_reset */ true,
+                            /* initially_signaled */ false);
+  MOZ_ALWAYS_SUCCEEDS(aEventTarget->Dispatch(NS_NewCancelableRunnableFunction(
+      "ipc::MessageChannel::OpenAsOtherThread", [&]() {
+        aTargetChan->Open(std::move(ports.second), GetOppSide(aSide), channelId,
+                          aEventTarget);
+        event.Signal();
+      })));
+  bool ok = event.Wait();
+  MOZ_RELEASE_ASSERT(ok);
+
+  // Now that the other side has connected, open the port on our side.
+  return Open(std::move(ports.first), aSide, channelId);
+}
+
+bool MessageChannel::OpenOnSameThread(MessageChannel* aTargetChan,
+                                      mozilla::ipc::Side aSide) {
+  auto [porta, portb] = NodeController::GetSingleton()->CreatePortPair();
+
+  nsID channelId = nsID::GenerateUUID();
+
+  aTargetChan->mIsSameThreadChannel = true;
+  mIsSameThreadChannel = true;
+
+  auto* currentThread = GetCurrentSerialEventTarget();
+  return aTargetChan->Open(std::move(portb), GetOppSide(aSide), channelId,
+                           currentThread) &&
+         Open(std::move(porta), aSide, channelId, currentThread);
+}
+
+bool MessageChannel::Send(UniquePtr<Message> aMsg) {
+  if (aMsg->size() >= kMinTelemetryMessageSize) {
+    Telemetry::Accumulate(Telemetry::IPC_MESSAGE_SIZE2, aMsg->size());
+  }
+
+  MOZ_RELEASE_ASSERT(!aMsg->is_sync());
+  MOZ_RELEASE_ASSERT(aMsg->nested_level() != IPC::Message::NESTED_INSIDE_SYNC);
+
+  AutoSetValue<bool> setOnCxxStack(mOnCxxStack, true);
+
+  AssertWorkerThread();
+  mMonitor->AssertNotCurrentThreadOwns();
+  if (MSG_ROUTING_NONE == aMsg->routing_id()) {
+    ReportMessageRouteError("MessageChannel::Send");
+    return false;
+  }
+
+  if (aMsg->seqno() == 0) {
+    aMsg->set_seqno(NextSeqno());
+  }
+
+  MonitorAutoLock lock(*mMonitor);
+  if (!Connected()) {
+    ReportConnectionError("Send", aMsg->type());
+    return false;
+  }
+
+  AddProfilerMarker(*aMsg, MessageDirection::eSending);
+  SendMessageToLink(std::move(aMsg));
+  return true;
+}
+
+void MessageChannel::SendMessageToLink(UniquePtr<Message> aMsg) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  // If the channel is not cross-process, there's no reason to be lazy, so we
+  // ignore the flag in that case.
+  if (aMsg->is_lazy_send() && mIsCrossProcess) {
+    // If this is the first lazy message in the queue and our worker thread
+    // supports direct task dispatch, dispatch a task to flush messages,
+    // ensuring we don't leave them pending forever.
+    if (!mFlushLazySendTask) {
+      if (nsCOMPtr<nsIDirectTaskDispatcher> dispatcher =
+              do_QueryInterface(mWorkerThread)) {
+        mFlushLazySendTask = new FlushLazySendMessagesRunnable(this);
+        MOZ_ALWAYS_SUCCEEDS(
+            dispatcher->DispatchDirectTask(do_AddRef(mFlushLazySendTask)));
+      }
+    }
+    if (mFlushLazySendTask) {
+      mFlushLazySendTask->PushMessage(std::move(aMsg));
+      return;
+    }
+  }
+
+  if (mFlushLazySendTask) {
+    FlushLazySendMessages();
+  }
+  mLink->SendMessage(std::move(aMsg));
+}
+
+void MessageChannel::FlushLazySendMessages() {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  // Clean up any SendLazyTask which might be pending.
+  auto messages = mFlushLazySendTask->TakeMessages();
+  mFlushLazySendTask = nullptr;
+
+  // Send all lazy messages, then clear the queue.
+  for (auto& msg : messages) {
+    mLink->SendMessage(std::move(msg));
+  }
+}
+
+UniquePtr<MessageChannel::UntypedCallbackHolder> MessageChannel::PopCallback(
+    const Message& aMsg, int32_t aActorId) {
+  auto iter = mPendingResponses.find(aMsg.seqno());
+  if (iter != mPendingResponses.end() && iter->second->mActorId == aActorId &&
+      iter->second->mReplyMsgId == aMsg.type()) {
+    UniquePtr<MessageChannel::UntypedCallbackHolder> ret =
+        std::move(iter->second);
+    mPendingResponses.erase(iter);
+    gUnresolvedResponses--;
+    return ret;
+  }
+  return nullptr;
+}
+
+void MessageChannel::RejectPendingResponsesForActor(int32_t aActorId) {
+  auto itr = mPendingResponses.begin();
+  while (itr != mPendingResponses.end()) {
+    if (itr->second.get()->mActorId != aActorId) {
+      ++itr;
+      continue;
+    }
+    itr->second.get()->Reject(ResponseRejectReason::ActorDestroyed);
+    // Take special care of advancing the iterator since we are
+    // removing it while iterating.
+    itr = mPendingResponses.erase(itr);
+    gUnresolvedResponses--;
+  }
+}
+
+class BuildIDsMatchMessage : public IPC::Message {
+ public:
+  BuildIDsMatchMessage()
+      : IPC::Message(MSG_ROUTING_NONE, BUILD_IDS_MATCH_MESSAGE_TYPE) {}
+  void Log(const std::string& aPrefix, FILE* aOutf) const {
+    fputs("(special `Build IDs match' message)", aOutf);
+  }
+};
+
+// Send the parent a special async message to confirm when the parent and child
+// are of the same buildID. Skips sending the message and returns false if the
+// buildIDs don't match. This is a minor variation on
+// MessageChannel::Send(Message* aMsg).
+bool MessageChannel::SendBuildIDsMatchMessage(const char* aParentBuildID) {
+  MOZ_ASSERT(!XRE_IsParentProcess());
+
+  nsCString parentBuildID(aParentBuildID);
+  nsCString childBuildID(mozilla::PlatformBuildID());
+
+  if (parentBuildID != childBuildID) {
+    // The build IDs didn't match, usually because an update occurred in the
+    // background.
+    return false;
+  }
+
+  auto msg = MakeUnique<BuildIDsMatchMessage>();
+
+  MOZ_RELEASE_ASSERT(!msg->is_sync());
+  MOZ_RELEASE_ASSERT(msg->nested_level() != IPC::Message::NESTED_INSIDE_SYNC);
+
+  AssertWorkerThread();
+  mMonitor->AssertNotCurrentThreadOwns();
+  // Don't check for MSG_ROUTING_NONE.
+
+  MonitorAutoLock lock(*mMonitor);
+  if (!Connected()) {
+    ReportConnectionError("SendBuildIDsMatchMessage", msg->type());
+    return false;
+  }
+
+#if defined(MOZ_DEBUG) && defined(ENABLE_TESTS)
+  // Technically, the behavior is interesting for any kind of process
+  // but when exercising tests, we want to crash only a content process and
+  // avoid making noise with other kind of processes crashing
+  if (const char* dontSend = PR_GetEnv("MOZ_BUILDID_MATCH_DONTSEND")) {
+    if (dontSend[0] == '1') {
+      // Bug 1732999: We are going to crash, so we need to advise leak check
+      // tooling to avoid intermittent missing leakcheck
+      NoteIntentionalCrash(XRE_GetProcessTypeString());
+      if (XRE_IsContentProcess()) {
+        return false;
+      }
+    }
+  }
+#endif
+
+  SendMessageToLink(std::move(msg));
+  return true;
+}
+
+class CancelMessage : public IPC::Message {
+ public:
+  explicit CancelMessage(int transaction)
+      : IPC::Message(MSG_ROUTING_NONE, CANCEL_MESSAGE_TYPE) {
+    set_transaction_id(transaction);
+  }
+  static bool Read(const Message* msg) { return true; }
+  void Log(const std::string& aPrefix, FILE* aOutf) const {
+    fputs("(special `Cancel' message)", aOutf);
+  }
+};
+
+bool MessageChannel::MaybeInterceptSpecialIOMessage(const Message& aMsg) {
+  mMonitor->AssertCurrentThreadOwns();
+
+  if (MSG_ROUTING_NONE == aMsg.routing_id()) {
+    if (GOODBYE_MESSAGE_TYPE == aMsg.type()) {
+      // We've received a GOODBYE message, close the connection and mark
+      // ourselves as "Closing".
+      mLink->Close();
+      mChannelState = ChannelClosing;
+      if (LoggingEnabled()) {
+        printf(
+            "[%s %u] NOTE: %s actor received `Goodbye' message.  Closing "
+            "channel.\n",
+            XRE_GeckoProcessTypeToString(XRE_GetProcessType()),
+            static_cast<uint32_t>(base::GetCurrentProcId()),
+            (mSide == ChildSide) ? "child" : "parent");
+      }
+
+      // Notify the worker thread that the connection has been closed, as we
+      // will not receive an `OnChannelErrorFromLink` after calling
+      // `mLink->Close()`.
+      if (AwaitingSyncReply()) {
+        NotifyWorkerThread();
+      }
+      PostErrorNotifyTask();
+      return true;
+    } else if (CANCEL_MESSAGE_TYPE == aMsg.type()) {
+      IPC_LOG("Cancel from message");
+      CancelTransaction(aMsg.transaction_id());
+      NotifyWorkerThread();
+      return true;
+    } else if (BUILD_IDS_MATCH_MESSAGE_TYPE == aMsg.type()) {
+      IPC_LOG("Build IDs match message");
+      mBuildIDsConfirmedMatch = true;
+      return true;
+    } else if (IMPENDING_SHUTDOWN_MESSAGE_TYPE == aMsg.type()) {
+      IPC_LOG("Impending Shutdown received");
+      ProcessChild::NotifiedImpendingShutdown();
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */
+bool MessageChannel::IsAlwaysDeferred(const Message& aMsg) {
+  // If a message is not NESTED_INSIDE_CPOW and not sync, then we always defer
+  // it.
+  return aMsg.nested_level() != IPC::Message::NESTED_INSIDE_CPOW &&
+         !aMsg.is_sync();
+}
+
+bool MessageChannel::ShouldDeferMessage(const Message& aMsg) {
+  // Never defer messages that have the highest nested level, even async
+  // ones. This is safe because only the child can send these messages, so
+  // they can never nest.
+  if (aMsg.nested_level() == IPC::Message::NESTED_INSIDE_CPOW) {
+    MOZ_ASSERT(!IsAlwaysDeferred(aMsg));
+    return false;
+  }
+
+  // Unless they're NESTED_INSIDE_CPOW, we always defer async messages.
+  // Note that we never send an async NESTED_INSIDE_SYNC message.
+  if (!aMsg.is_sync()) {
+    MOZ_RELEASE_ASSERT(aMsg.nested_level() == IPC::Message::NOT_NESTED);
+    MOZ_ASSERT(IsAlwaysDeferred(aMsg));
+    return true;
+  }
+
+  MOZ_ASSERT(!IsAlwaysDeferred(aMsg));
+
+  int msgNestedLevel = aMsg.nested_level();
+  int waitingNestedLevel = AwaitingSyncReplyNestedLevel();
+
+  // Always defer if the nested level of the incoming message is less than the
+  // nested level of the message we're awaiting.
+  if (msgNestedLevel < waitingNestedLevel) return true;
+
+  // Never defer if the message has strictly greater nested level.
+  if (msgNestedLevel > waitingNestedLevel) return false;
+
+  // When both sides send sync messages of the same nested level, we resolve the
+  // race by dispatching in the child and deferring the incoming message in
+  // the parent. However, the parent still needs to dispatch nested sync
+  // messages.
+  //
+  // Deferring in the parent only sort of breaks message ordering. When the
+  // child's message comes in, we can pretend the child hasn't quite
+  // finished sending it yet. Since the message is sync, we know that the
+  // child hasn't moved on yet.
+  return mSide == ParentSide &&
+         aMsg.transaction_id() != CurrentNestedInsideSyncTransaction();
+}
+
+void MessageChannel::OnMessageReceivedFromLink(UniquePtr<Message> aMsg) {
+  mMonitor->AssertCurrentThreadOwns();
+  MOZ_ASSERT(mChannelState == ChannelConnected);
+
+  if (MaybeInterceptSpecialIOMessage(*aMsg)) {
+    return;
+  }
+
+  mListener->OnChannelReceivedMessage(*aMsg);
+
+  // If we're awaiting a sync reply, we know that it needs to be immediately
+  // handled to unblock us.
+  if (aMsg->is_sync() && aMsg->is_reply()) {
+    IPC_LOG("Received reply seqno=%d xid=%d", aMsg->seqno(),
+            aMsg->transaction_id());
+
+    if (aMsg->seqno() == mTimedOutMessageSeqno) {
+      // Drop the message, but allow future sync messages to be sent.
+      IPC_LOG("Received reply to timedout message; igoring; xid=%d",
+              mTimedOutMessageSeqno);
+      EndTimeout();
+      return;
+    }
+
+    MOZ_RELEASE_ASSERT(AwaitingSyncReply());
+    MOZ_RELEASE_ASSERT(!mTimedOutMessageSeqno);
+
+    mTransactionStack->HandleReply(std::move(aMsg));
+    NotifyWorkerThread();
+    return;
+  }
+
+  // Nested messages cannot be compressed.
+  MOZ_RELEASE_ASSERT(aMsg->compress_type() == IPC::Message::COMPRESSION_NONE ||
+                     aMsg->nested_level() == IPC::Message::NOT_NESTED);
+
+  if (aMsg->compress_type() == IPC::Message::COMPRESSION_ENABLED &&
+      !mPending.isEmpty()) {
+    auto* last = mPending.getLast();
+    last->AssertMonitorHeld(*mMonitor);
+    bool compress = last->Msg()->type() == aMsg->type() &&
+                    last->Msg()->routing_id() == aMsg->routing_id();
+    if (compress) {
+      // This message type has compression enabled, and the back of the
+      // queue was the same message type and routed to the same destination.
+      // Replace it with the newer message.
+      MOZ_RELEASE_ASSERT(last->Msg()->compress_type() ==
+                         IPC::Message::COMPRESSION_ENABLED);
+      last->Msg() = std::move(aMsg);
+      return;
+    }
+  } else if (aMsg->compress_type() == IPC::Message::COMPRESSION_ALL &&
+             !mPending.isEmpty()) {
+    for (MessageTask* p = mPending.getLast(); p; p = p->getPrevious()) {
+      p->AssertMonitorHeld(*mMonitor);
+      if (p->Msg()->type() == aMsg->type() &&
+          p->Msg()->routing_id() == aMsg->routing_id()) {
+        // This message type has compression enabled, and the queue
+        // holds a message with the same message type and routed to the
+        // same destination. Erase it. Note that, since we always
+        // compress these redundancies, There Can Be Only One.
+        MOZ_RELEASE_ASSERT(p->Msg()->compress_type() ==
+                           IPC::Message::COMPRESSION_ALL);
+        MOZ_RELEASE_ASSERT(IsAlwaysDeferred(*p->Msg()));
+        p->remove();
+        break;
+      }
+    }
+  }
+
+  bool alwaysDeferred = IsAlwaysDeferred(*aMsg);
+
+  bool shouldWakeUp = AwaitingSyncReply() && !ShouldDeferMessage(*aMsg);
+
+  IPC_LOG("Receive from link; seqno=%d, xid=%d, shouldWakeUp=%d", aMsg->seqno(),
+          aMsg->transaction_id(), shouldWakeUp);
+
+  // There are two cases we're concerned about, relating to the state of the
+  // worker thread:
+  //
+  // (1) We are waiting on a sync reply - worker thread is blocked on the
+  //     IPC monitor.
+  //   - If the message is NESTED_INSIDE_SYNC, we wake up the worker thread to
+  //     deliver the message depending on ShouldDeferMessage. Otherwise, we
+  //     leave it in the mPending queue, posting a task to the worker event
+  //     loop, where it will be processed once the synchronous reply has been
+  //     received.
+  //
+  // (2) We are not waiting on a reply.
+  //   - We post a task to the worker event loop.
+  //
+  // Note that, we may notify the worker thread even though the monitor is not
+  // blocked. This is okay, since we always check for pending events before
+  // blocking again.
+
+  RefPtr<MessageTask> task = new MessageTask(this, std::move(aMsg));
+  mPending.insertBack(task);
+
+  if (!alwaysDeferred) {
+    mMaybeDeferredPendingCount++;
+  }
+
+  if (shouldWakeUp) {
+    NotifyWorkerThread();
+  }
+
+  // Although we usually don't need to post a message task if
+  // shouldWakeUp is true, it's easier to post anyway than to have to
+  // guarantee that every Send call processes everything it's supposed to
+  // before returning.
+  task->AssertMonitorHeld(*mMonitor);
+  task->Post();
+}
+
+void MessageChannel::PeekMessages(
+    const std::function<bool(const Message& aMsg)>& aInvoke) {
+  // FIXME: We shouldn't be holding the lock for aInvoke!
+  MonitorAutoLock lock(*mMonitor);
+
+  for (MessageTask* it : mPending) {
+    it->AssertMonitorHeld(*mMonitor);
+    const Message& msg = *it->Msg();
+    if (!aInvoke(msg)) {
+      break;
+    }
+  }
+}
+
+void MessageChannel::ProcessPendingRequests(
+    ActorLifecycleProxy* aProxy, AutoEnterTransaction& aTransaction) {
+  mMonitor->AssertCurrentThreadOwns();
+
+  AssertMaybeDeferredCountCorrect();
+  if (mMaybeDeferredPendingCount == 0) {
+    return;
+  }
+
+  IPC_LOG("ProcessPendingRequests for seqno=%d, xid=%d",
+          aTransaction.SequenceNumber(), aTransaction.TransactionID());
+
+  // Loop until there aren't any more nested messages to process.
+  for (;;) {
+    // If we canceled during ProcessPendingRequest, then we need to leave
+    // immediately because the results of ShouldDeferMessage will be
+    // operating with weird state (as if no Send is in progress). That could
+    // cause even NOT_NESTED sync messages to be processed (but not
+    // NOT_NESTED async messages), which would break message ordering.
+    if (aTransaction.IsCanceled()) {
+      return;
+    }
+
+    Vector<UniquePtr<Message>> toProcess;
+
+    for (MessageTask* p = mPending.getFirst(); p;) {
+      p->AssertMonitorHeld(*mMonitor);
+      UniquePtr<Message>& msg = p->Msg();
+
+      MOZ_RELEASE_ASSERT(!aTransaction.IsCanceled(),
+                         "Calling ShouldDeferMessage when cancelled");
+      bool defer = ShouldDeferMessage(*msg);
+
+      // Only log the interesting messages.
+      if (msg->is_sync() ||
+          msg->nested_level() == IPC::Message::NESTED_INSIDE_CPOW) {
+        IPC_LOG("ShouldDeferMessage(seqno=%d) = %d", msg->seqno(), defer);
+      }
+
+      if (!defer) {
+        MOZ_ASSERT(!IsAlwaysDeferred(*msg));
+
+        if (!toProcess.append(std::move(msg))) MOZ_CRASH();
+
+        mMaybeDeferredPendingCount--;
+
+        p = p->removeAndGetNext();
+        continue;
+      }
+      p = p->getNext();
+    }
+
+    if (toProcess.empty()) {
+      break;
+    }
+
+    // Processing these messages could result in more messages, so we
+    // loop around to check for more afterwards.
+
+    for (auto& msg : toProcess) {
+      ProcessPendingRequest(aProxy, std::move(msg));
+    }
+  }
+
+  AssertMaybeDeferredCountCorrect();
+}
+
+bool MessageChannel::Send(UniquePtr<Message> aMsg, UniquePtr<Message>* aReply) {
+  mozilla::TimeStamp start = TimeStamp::Now();
+  if (aMsg->size() >= kMinTelemetryMessageSize) {
+    Telemetry::Accumulate(Telemetry::IPC_MESSAGE_SIZE2, aMsg->size());
+  }
+
+  // Sanity checks.
+  AssertWorkerThread();
+  mMonitor->AssertNotCurrentThreadOwns();
+  MOZ_RELEASE_ASSERT(!mIsSameThreadChannel,
+                     "sync send over same-thread channel will deadlock!");
+
+  RefPtr<ActorLifecycleProxy> proxy = Listener()->GetLifecycleProxy();
+
+#ifdef OS_WIN
+  SyncStackFrame frame(this);
+  NeuteredWindowRegion neuteredRgn(mFlags &
+                                   REQUIRE_DEFERRED_MESSAGE_PROTECTION);
+#endif
+
+  AutoSetValue<bool> setOnCxxStack(mOnCxxStack, true);
+
+  MonitorAutoLock lock(*mMonitor);
+
+  if (mTimedOutMessageSeqno) {
+    // Don't bother sending another sync message if a previous one timed out
+    // and we haven't received a reply for it. Once the original timed-out
+    // message receives a reply, we'll be able to send more sync messages
+    // again.
+    IPC_LOG("Send() failed due to previous timeout");
+    mLastSendError = SyncSendError::PreviousTimeout;
+    return false;
+  }
+
+  if (DispatchingSyncMessageNestedLevel() == IPC::Message::NOT_NESTED &&
+      aMsg->nested_level() > IPC::Message::NOT_NESTED) {
+    // Don't allow sending CPOWs while we're dispatching a sync message.
+    IPC_LOG("Nested level forbids send");
+    mLastSendError = SyncSendError::SendingCPOWWhileDispatchingSync;
+    return false;
+  }
+
+  if (DispatchingSyncMessageNestedLevel() == IPC::Message::NESTED_INSIDE_CPOW ||
+      DispatchingAsyncMessageNestedLevel() ==
+          IPC::Message::NESTED_INSIDE_CPOW) {
+    // Generally only the parent dispatches urgent messages. And the only
+    // sync messages it can send are NESTED_INSIDE_SYNC. Mainly we want to
+    // ensure here that we don't return false for non-CPOW messages.
+    MOZ_RELEASE_ASSERT(aMsg->nested_level() ==
+                       IPC::Message::NESTED_INSIDE_SYNC);
+    IPC_LOG("Sending while dispatching urgent message");
+    mLastSendError = SyncSendError::SendingCPOWWhileDispatchingUrgent;
+    return false;
+  }
+
+  if (aMsg->nested_level() < DispatchingSyncMessageNestedLevel() ||
+      aMsg->nested_level() < AwaitingSyncReplyNestedLevel()) {
+    MOZ_RELEASE_ASSERT(DispatchingSyncMessage() || DispatchingAsyncMessage());
+    IPC_LOG("Cancel from Send");
+    auto cancel =
+        MakeUnique<CancelMessage>(CurrentNestedInsideSyncTransaction());
+    CancelTransaction(CurrentNestedInsideSyncTransaction());
+    SendMessageToLink(std::move(cancel));
+  }
+
+  IPC_ASSERT(aMsg->is_sync(), "can only Send() sync messages here");
+
+  IPC_ASSERT(aMsg->nested_level() >= DispatchingSyncMessageNestedLevel(),
+             "can't send sync message of a lesser nested level than what's "
+             "being dispatched");
+  IPC_ASSERT(AwaitingSyncReplyNestedLevel() <= aMsg->nested_level(),
+             "nested sync message sends must be of increasing nested level");
+  IPC_ASSERT(
+      DispatchingSyncMessageNestedLevel() != IPC::Message::NESTED_INSIDE_CPOW,
+      "not allowed to send messages while dispatching urgent messages");
+
+  IPC_ASSERT(
+      DispatchingAsyncMessageNestedLevel() != IPC::Message::NESTED_INSIDE_CPOW,
+      "not allowed to send messages while dispatching urgent messages");
+
+  if (!Connected()) {
+    ReportConnectionError("SendAndWait", aMsg->type());
+    mLastSendError = SyncSendError::NotConnectedBeforeSend;
+    return false;
+  }
+
+  aMsg->set_seqno(NextSeqno());
+
+  int32_t seqno = aMsg->seqno();
+  int nestedLevel = aMsg->nested_level();
+  msgid_t replyType = aMsg->type() + 1;
+
+  AutoEnterTransaction* stackTop = mTransactionStack;
+
+  // If the most recent message on the stack is NESTED_INSIDE_SYNC, then our
+  // message should nest inside that and we use the same transaction
+  // ID. Otherwise we need a new transaction ID (so we use the seqno of the
+  // message we're sending).
+  bool nest =
+      stackTop && stackTop->NestedLevel() == IPC::Message::NESTED_INSIDE_SYNC;
+  int32_t transaction = nest ? stackTop->TransactionID() : seqno;
+  aMsg->set_transaction_id(transaction);
+
+  AutoEnterTransaction transact(this, seqno, transaction, nestedLevel);
+
+  IPC_LOG("Send seqno=%d, xid=%d", seqno, transaction);
+
+  // aMsg will be destroyed soon, let's keep its type.
+  const char* msgName = aMsg->name();
+  const msgid_t msgType = aMsg->type();
+
+  AddProfilerMarker(*aMsg, MessageDirection::eSending);
+  SendMessageToLink(std::move(aMsg));
+
+  while (true) {
+    MOZ_RELEASE_ASSERT(!transact.IsCanceled());
+    ProcessPendingRequests(proxy, transact);
+    if (transact.IsComplete()) {
+      break;
+    }
+    if (!Connected()) {
+      ReportConnectionError("Send", msgType);
+      mLastSendError = SyncSendError::DisconnectedDuringSend;
+      return false;
+    }
+
+    MOZ_RELEASE_ASSERT(!mTimedOutMessageSeqno);
+    MOZ_RELEASE_ASSERT(!transact.IsComplete());
+    MOZ_RELEASE_ASSERT(mTransactionStack == &transact);
+
+    bool maybeTimedOut = !WaitForSyncNotify();
+
+    if (mListener->NeedArtificialSleep()) {
+      MonitorAutoUnlock unlock(*mMonitor);
+      mListener->ArtificialSleep();
+    }
+
+    if (!Connected()) {
+      ReportConnectionError("SendAndWait", msgType);
+      mLastSendError = SyncSendError::DisconnectedDuringSend;
+      return false;
+    }
+
+    if (transact.IsCanceled()) {
+      break;
+    }
+
+    MOZ_RELEASE_ASSERT(mTransactionStack == &transact);
+
+    // We only time out a message if it initiated a new transaction (i.e.,
+    // if neither side has any other message Sends on the stack).
+    bool canTimeOut = transact.IsBottom();
+    if (maybeTimedOut && canTimeOut && !ShouldContinueFromTimeout()) {
+      // Since ShouldContinueFromTimeout drops the lock, we need to
+      // re-check all our conditions here. We shouldn't time out if any of
+      // these things happen because there won't be a reply to the timed
+      // out message in these cases.
+      if (transact.IsComplete()) {
+        break;
+      }
+
+      IPC_LOG("Timing out Send: xid=%d", transaction);
+
+      mTimedOutMessageSeqno = seqno;
+      mTimedOutMessageNestedLevel = nestedLevel;
+      mLastSendError = SyncSendError::TimedOut;
+      return false;
+    }
+
+    if (transact.IsCanceled()) {
+      break;
+    }
+  }
+
+  if (transact.IsCanceled()) {
+    IPC_LOG("Other side canceled seqno=%d, xid=%d", seqno, transaction);
+    mLastSendError = SyncSendError::CancelledAfterSend;
+    return false;
+  }
+
+  if (transact.IsError()) {
+    IPC_LOG("Error: seqno=%d, xid=%d", seqno, transaction);
+    mLastSendError = SyncSendError::ReplyError;
+    return false;
+  }
+
+  uint32_t latencyMs = round((TimeStamp::Now() - start).ToMilliseconds());
+  IPC_LOG("Got reply: seqno=%d, xid=%d, msgName=%s, latency=%ums", seqno,
+          transaction, msgName, latencyMs);
+
+  UniquePtr<Message> reply = transact.GetReply();
+
+  MOZ_RELEASE_ASSERT(reply);
+  MOZ_RELEASE_ASSERT(reply->is_reply(), "expected reply");
+  MOZ_RELEASE_ASSERT(!reply->is_reply_error());
+  MOZ_RELEASE_ASSERT(reply->seqno() == seqno);
+  MOZ_RELEASE_ASSERT(reply->type() == replyType, "wrong reply type");
+  MOZ_RELEASE_ASSERT(reply->is_sync());
+
+  AddProfilerMarker(*reply, MessageDirection::eReceiving);
+
+  if (reply->size() >= kMinTelemetryMessageSize) {
+    Telemetry::Accumulate(Telemetry::IPC_REPLY_SIZE,
+                          nsDependentCString(msgName), reply->size());
+  }
+
+  *aReply = std::move(reply);
+
+  // NOTE: Only collect IPC_SYNC_MAIN_LATENCY_MS on the main thread (bug
+  // 1343729)
+  if (NS_IsMainThread() && latencyMs >= kMinTelemetrySyncIPCLatencyMs) {
+    Telemetry::Accumulate(Telemetry::IPC_SYNC_MAIN_LATENCY_MS,
+                          nsDependentCString(msgName), latencyMs);
+  }
+  return true;
+}
+
+bool MessageChannel::HasPendingEvents() {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+  return ConnectedOrClosing() && !mPending.isEmpty();
+}
+
+bool MessageChannel::ProcessPendingRequest(ActorLifecycleProxy* aProxy,
+                                           UniquePtr<Message> aUrgent) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  IPC_LOG("Process pending: seqno=%d, xid=%d", aUrgent->seqno(),
+          aUrgent->transaction_id());
+
+  // keep the error relevant information
+  msgid_t msgType = aUrgent->type();
+
+  DispatchMessage(aProxy, std::move(aUrgent));
+  if (!ConnectedOrClosing()) {
+    ReportConnectionError("ProcessPendingRequest", msgType);
+    return false;
+  }
+
+  return true;
+}
+
+bool MessageChannel::ShouldRunMessage(const Message& aMsg) {
+  if (!mTimedOutMessageSeqno) {
+    return true;
+  }
+
+  // If we've timed out a message and we're awaiting the reply to the timed
+  // out message, we have to be careful what messages we process. Here's what
+  // can go wrong:
+  // 1. child sends a NOT_NESTED sync message S
+  // 2. parent sends a NESTED_INSIDE_SYNC sync message H at the same time
+  // 3. parent times out H
+  // 4. child starts processing H and sends a NESTED_INSIDE_SYNC message H'
+  //    nested within the same transaction
+  // 5. parent dispatches S and sends reply
+  // 6. child asserts because it instead expected a reply to H'.
+  //
+  // To solve this, we refuse to process S in the parent until we get a reply
+  // to H. More generally, let the timed out message be M. We don't process a
+  // message unless the child would need the response to that message in order
+  // to process M. Those messages are the ones that have a higher nested level
+  // than M or that are part of the same transaction as M.
+  if (aMsg.nested_level() < mTimedOutMessageNestedLevel ||
+      (aMsg.nested_level() == mTimedOutMessageNestedLevel &&
+       aMsg.transaction_id() != mTimedOutMessageSeqno)) {
+    return false;
+  }
+
+  return true;
+}
+
+void MessageChannel::RunMessage(ActorLifecycleProxy* aProxy,
+                                MessageTask& aTask) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+  aTask.AssertMonitorHeld(*mMonitor);
+
+  UniquePtr<Message>& msg = aTask.Msg();
+
+  if (!ConnectedOrClosing()) {
+    ReportConnectionError("RunMessage", msg->type());
+    return;
+  }
+
+  // Check that we're going to run the first message that's valid to run.
+#if 0
+#  ifdef DEBUG
+    for (MessageTask* task : mPending) {
+        if (task == &aTask) {
+            break;
+        }
+
+        MOZ_ASSERT(!ShouldRunMessage(*task->Msg()) ||
+                   aTask.Msg()->priority() != task->Msg()->priority());
+
+    }
+#  endif
+#endif
+
+  if (!ShouldRunMessage(*msg)) {
+    return;
+  }
+
+  MOZ_RELEASE_ASSERT(aTask.isInList());
+  aTask.remove();
+
+  if (!IsAlwaysDeferred(*msg)) {
+    mMaybeDeferredPendingCount--;
+  }
+
+  DispatchMessage(aProxy, std::move(msg));
+}
+
+NS_IMPL_ISUPPORTS_INHERITED(MessageChannel::MessageTask, CancelableRunnable,
+                            nsIRunnablePriority, nsIRunnableIPCMessageType)
+
+static uint32_t ToRunnablePriority(IPC::Message::PriorityValue aPriority) {
+  switch (aPriority) {
+    case IPC::Message::NORMAL_PRIORITY:
+      return nsIRunnablePriority::PRIORITY_NORMAL;
+    case IPC::Message::INPUT_PRIORITY:
+      return nsIRunnablePriority::PRIORITY_INPUT_HIGH;
+    case IPC::Message::VSYNC_PRIORITY:
+      return nsIRunnablePriority::PRIORITY_VSYNC;
+    case IPC::Message::MEDIUMHIGH_PRIORITY:
+      return nsIRunnablePriority::PRIORITY_MEDIUMHIGH;
+    case IPC::Message::CONTROL_PRIORITY:
+      return nsIRunnablePriority::PRIORITY_CONTROL;
+    default:
+      MOZ_ASSERT_UNREACHABLE();
+      return nsIRunnablePriority::PRIORITY_NORMAL;
+  }
+}
+
+MessageChannel::MessageTask::MessageTask(MessageChannel* aChannel,
+                                         UniquePtr<Message> aMessage)
+    : CancelableRunnable(aMessage->name()),
+      mMonitor(aChannel->mMonitor),
+      mChannel(aChannel),
+      mMessage(std::move(aMessage)),
+      mPriority(ToRunnablePriority(mMessage->priority())),
+      mScheduled(false)
+#ifdef FUZZING_SNAPSHOT
+      ,
+      mIsFuzzMsg(mMessage->IsFuzzMsg()),
+      mFuzzStopped(false)
+#endif
+{
+  MOZ_DIAGNOSTIC_ASSERT(mMessage, "message may not be null");
+#ifdef FUZZING_SNAPSHOT
+  if (mIsFuzzMsg) {
+    MOZ_FUZZING_IPC_MT_CTOR();
+  }
+#endif
+}
+
+MessageChannel::MessageTask::~MessageTask() {
+#ifdef FUZZING_SNAPSHOT
+  // We track fuzzing messages until their run is complete. To make sure
+  // that we don't miss messages that are for some reason destroyed without
+  // being run (e.g. canceled), we catch this condition in the destructor.
+  if (mIsFuzzMsg && !mFuzzStopped) {
+    MOZ_FUZZING_IPC_MT_STOP();
+  } else if (!mIsFuzzMsg && !fuzzing::Nyx::instance().started()) {
+    MOZ_FUZZING_IPC_PRE_FUZZ_MT_STOP();
+  }
+#endif
+}
+
+nsresult MessageChannel::MessageTask::Run() {
+  mMonitor->AssertNotCurrentThreadOwns();
+
+  // Drop the toplevel actor's lifecycle proxy outside of our monitor if we take
+  // it, as destroying our ActorLifecycleProxy reference can acquire the
+  // monitor.
+  RefPtr<ActorLifecycleProxy> proxy;
+
+  MonitorAutoLock lock(*mMonitor);
+
+  // In case we choose not to run this message, we may need to be able to Post
+  // it again.
+  mScheduled = false;
+
+  if (!isInList()) {
+    return NS_OK;
+  }
+
+#ifdef FUZZING_SNAPSHOT
+  if (!mIsFuzzMsg) {
+    if (fuzzing::Nyx::instance().started()) {
+      // Once we started fuzzing, prevent non-fuzzing tasks from being
+      // run and potentially blocking worker threads.
+      //
+      // TODO: This currently blocks all MessageTasks from running, not
+      // just those belonging to the target process pair. We currently
+      // do this for performance reasons, but it should be re-evaluated
+      // at a later stage when we found a better snapshot point.
+      return NS_OK;
+    }
+    // Record all running tasks prior to fuzzing, so we can wait for
+    // them to settle before snapshotting.
+    MOZ_FUZZING_IPC_PRE_FUZZ_MT_RUN();
+  }
+#endif
+
+  Channel()->AssertWorkerThread();
+  mMonitor->AssertSameMonitor(*Channel()->mMonitor);
+  proxy = Channel()->Listener()->GetLifecycleProxy();
+  Channel()->RunMessage(proxy, *this);
+
+#ifdef FUZZING_SNAPSHOT
+  if (mIsFuzzMsg && !mFuzzStopped) {
+    MOZ_FUZZING_IPC_MT_STOP();
+    mFuzzStopped = true;
+  }
+#endif
+  return NS_OK;
+}
+
+// Warning: This method removes the receiver from whatever list it might be in.
+nsresult MessageChannel::MessageTask::Cancel() {
+  mMonitor->AssertNotCurrentThreadOwns();
+
+  MonitorAutoLock lock(*mMonitor);
+
+  if (!isInList()) {
+    return NS_OK;
+  }
+
+  Channel()->AssertWorkerThread();
+  mMonitor->AssertSameMonitor(*Channel()->mMonitor);
+  if (!IsAlwaysDeferred(*Msg())) {
+    Channel()->mMaybeDeferredPendingCount--;
+  }
+
+  remove();
+
+#ifdef FUZZING_SNAPSHOT
+  if (mIsFuzzMsg && !mFuzzStopped) {
+    MOZ_FUZZING_IPC_MT_STOP();
+    mFuzzStopped = true;
+  }
+#endif
+
+  return NS_OK;
+}
+
+void MessageChannel::MessageTask::Post() {
+  mMonitor->AssertCurrentThreadOwns();
+  mMonitor->AssertSameMonitor(*Channel()->mMonitor);
+  MOZ_RELEASE_ASSERT(!mScheduled);
+  MOZ_RELEASE_ASSERT(isInList());
+
+  mScheduled = true;
+
+  Channel()->mWorkerThread->Dispatch(do_AddRef(this));
+}
+
+NS_IMETHODIMP
+MessageChannel::MessageTask::GetPriority(uint32_t* aPriority) {
+  *aPriority = mPriority;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MessageChannel::MessageTask::GetType(uint32_t* aType) {
+  mMonitor->AssertNotCurrentThreadOwns();
+
+  MonitorAutoLock lock(*mMonitor);
+  if (!mMessage) {
+    // If mMessage has been moved already elsewhere, we can't know what the type
+    // has been.
+    return NS_ERROR_FAILURE;
+  }
+
+  *aType = mMessage->type();
+  return NS_OK;
+}
+
+void MessageChannel::DispatchMessage(ActorLifecycleProxy* aProxy,
+                                     UniquePtr<Message> aMsg) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  Maybe<AutoNoJSAPI> nojsapi;
+  if (NS_IsMainThread() && CycleCollectedJSContext::Get()) {
+    nojsapi.emplace();
+  }
+
+  UniquePtr<Message> reply;
+
+  IPC_LOG("DispatchMessage: seqno=%d, xid=%d", aMsg->seqno(),
+          aMsg->transaction_id());
+  AddProfilerMarker(*aMsg, MessageDirection::eReceiving);
+
+  {
+    AutoEnterTransaction transaction(this, *aMsg);
+
+    int id = aMsg->transaction_id();
+    MOZ_RELEASE_ASSERT(!aMsg->is_sync() || id == transaction.TransactionID());
+
+    {
+      MonitorAutoUnlock unlock(*mMonitor);
+      AutoSetValue<bool> setOnCxxStack(mOnCxxStack, true);
+
+      mListener->ArtificialSleep();
+
+      if (aMsg->is_sync()) {
+        DispatchSyncMessage(aProxy, *aMsg, reply);
+      } else {
+        DispatchAsyncMessage(aProxy, *aMsg);
+      }
+
+      mListener->ArtificialSleep();
+    }
+
+    if (reply && transaction.IsCanceled()) {
+      // The transaction has been canceled. Don't send a reply.
+      IPC_LOG("Nulling out reply due to cancellation, seqno=%d, xid=%d",
+              aMsg->seqno(), id);
+      reply = nullptr;
+    }
+  }
+
+  if (reply && ChannelConnected == mChannelState) {
+    IPC_LOG("Sending reply seqno=%d, xid=%d", aMsg->seqno(),
+            aMsg->transaction_id());
+    AddProfilerMarker(*reply, MessageDirection::eSending);
+
+    SendMessageToLink(std::move(reply));
+  }
+}
+
+void MessageChannel::DispatchSyncMessage(ActorLifecycleProxy* aProxy,
+                                         const Message& aMsg,
+                                         UniquePtr<Message>& aReply) {
+  AssertWorkerThread();
+
+  mozilla::TimeStamp start = TimeStamp::Now();
+
+  int nestedLevel = aMsg.nested_level();
+
+  MOZ_RELEASE_ASSERT(nestedLevel == IPC::Message::NOT_NESTED ||
+                     NS_IsMainThread());
+
+  MessageChannel* dummy;
+  MessageChannel*& blockingVar =
+      mSide == ChildSide && NS_IsMainThread() ? gParentProcessBlocker : dummy;
+
+  Result rv;
+  {
+    AutoSetValue<MessageChannel*> blocked(blockingVar, this);
+    rv = aProxy->Get()->OnMessageReceived(aMsg, aReply);
+  }
+
+  uint32_t latencyMs = round((TimeStamp::Now() - start).ToMilliseconds());
+  if (latencyMs >= kMinTelemetrySyncIPCLatencyMs) {
+    Telemetry::Accumulate(Telemetry::IPC_SYNC_RECEIVE_MS,
+                          nsDependentCString(aMsg.name()), latencyMs);
+  }
+
+  if (!MaybeHandleError(rv, aMsg, "DispatchSyncMessage")) {
+    aReply = Message::ForSyncDispatchError(aMsg.nested_level());
+  }
+  aReply->set_seqno(aMsg.seqno());
+  aReply->set_transaction_id(aMsg.transaction_id());
+}
+
+void MessageChannel::DispatchAsyncMessage(ActorLifecycleProxy* aProxy,
+                                          const Message& aMsg) {
+  AssertWorkerThread();
+  MOZ_RELEASE_ASSERT(!aMsg.is_sync());
+
+  if (aMsg.routing_id() == MSG_ROUTING_NONE) {
+    NS_WARNING("unhandled special message!");
+    MaybeHandleError(MsgNotKnown, aMsg, "DispatchAsyncMessage");
+    return;
+  }
+
+  Result rv;
+  {
+    int nestedLevel = aMsg.nested_level();
+    AutoSetValue<bool> async(mDispatchingAsyncMessage, true);
+    AutoSetValue<int> nestedLevelSet(mDispatchingAsyncMessageNestedLevel,
+                                     nestedLevel);
+    rv = aProxy->Get()->OnMessageReceived(aMsg);
+  }
+  MaybeHandleError(rv, aMsg, "DispatchAsyncMessage");
+}
+
+void MessageChannel::EnqueuePendingMessages() {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  // XXX performance tuning knob: could process all or k pending
+  // messages here, rather than enqueuing for later processing
+
+  RepostAllMessages();
+}
+
+bool MessageChannel::WaitResponse(bool aWaitTimedOut) {
+  AssertWorkerThread();
+  if (aWaitTimedOut) {
+    if (mInTimeoutSecondHalf) {
+      // We've really timed out this time.
+      return false;
+    }
+    // Try a second time.
+    mInTimeoutSecondHalf = true;
+  } else {
+    mInTimeoutSecondHalf = false;
+  }
+  return true;
+}
+
+#ifndef OS_WIN
+bool MessageChannel::WaitForSyncNotify() {
+  AssertWorkerThread();
+#  ifdef DEBUG
+  // WARNING: We don't release the lock here. We can't because the link
+  // could signal at this time and we would miss it. Instead we require
+  // ArtificialTimeout() to be extremely simple.
+  if (mListener->ArtificialTimeout()) {
+    return false;
+  }
+#  endif
+
+  MOZ_RELEASE_ASSERT(!mIsSameThreadChannel,
+                     "Wait on same-thread channel will deadlock!");
+
+  TimeDuration timeout = (kNoTimeout == mTimeoutMs)
+                             ? TimeDuration::Forever()
+                             : TimeDuration::FromMilliseconds(mTimeoutMs);
+  CVStatus status = mMonitor->Wait(timeout);
+
+  // If the timeout didn't expire, we know we received an event. The
+  // converse is not true.
+  return WaitResponse(status == CVStatus::Timeout);
+}
+
+void MessageChannel::NotifyWorkerThread() { mMonitor->Notify(); }
+#endif
+
+bool MessageChannel::ShouldContinueFromTimeout() {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  bool cont;
+  {
+    MonitorAutoUnlock unlock(*mMonitor);
+    cont = mListener->ShouldContinueFromReplyTimeout();
+    mListener->ArtificialSleep();
+  }
+
+  static enum {
+    UNKNOWN,
+    NOT_DEBUGGING,
+    DEBUGGING
+  } sDebuggingChildren = UNKNOWN;
+
+  if (sDebuggingChildren == UNKNOWN) {
+    sDebuggingChildren =
+        getenv("MOZ_DEBUG_CHILD_PROCESS") || getenv("MOZ_DEBUG_CHILD_PAUSE")
+            ? DEBUGGING
+            : NOT_DEBUGGING;
+  }
+  if (sDebuggingChildren == DEBUGGING) {
+    return true;
+  }
+
+  return cont;
+}
+
+void MessageChannel::SetReplyTimeoutMs(int32_t aTimeoutMs) {
+  // Set channel timeout value. Since this is broken up into
+  // two period, the minimum timeout value is 2ms.
+  AssertWorkerThread();
+  mTimeoutMs =
+      (aTimeoutMs <= 0) ? kNoTimeout : (int32_t)ceil((double)aTimeoutMs / 2.0);
+}
+
+void MessageChannel::ReportConnectionError(const char* aFunctionName,
+                                           const uint32_t aMsgType) const {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  const char* errorMsg = nullptr;
+  switch (mChannelState) {
+    case ChannelClosed:
+      errorMsg = "Closed channel: cannot send/recv";
+      break;
+    case ChannelClosing:
+      errorMsg = "Channel closing: too late to send, messages will be lost";
+      break;
+    case ChannelError:
+      errorMsg = "Channel error: cannot send/recv";
+      break;
+
+    default:
+      MOZ_CRASH("unreached");
+  }
+
+  // IPC connection errors are fairly common, especially "Channel closing: too
+  // late to send/recv, messages will be lost", so shouldn't be being reported
+  // on release builds, as that's misleading as to their severity.
+  NS_WARNING(nsPrintfCString("IPC Connection Error: [%s][%s] %s(msgname=%s) %s",
+                             StringFromIPCSide(mSide), mName, aFunctionName,
+                             IPC::StringFromIPCMessageType(aMsgType), errorMsg)
+                 .get());
+
+  MonitorAutoUnlock unlock(*mMonitor);
+  mListener->ProcessingError(MsgDropped, errorMsg);
+}
+
+void MessageChannel::ReportMessageRouteError(const char* channelName) const {
+  PrintErrorMessage(mSide, channelName, "Need a route");
+  mListener->ProcessingError(MsgRouteError, "MsgRouteError");
+}
+
+bool MessageChannel::MaybeHandleError(Result code, const Message& aMsg,
+                                      const char* channelName) {
+  if (MsgProcessed == code) return true;
+
+  const char* errorMsg = nullptr;
+  switch (code) {
+    case MsgNotKnown:
+      errorMsg = "Unknown message: not processed";
+      break;
+    case MsgNotAllowed:
+      errorMsg = "Message not allowed: cannot be sent/recvd in this state";
+      break;
+    case MsgPayloadError:
+      errorMsg = "Payload error: message could not be deserialized";
+      break;
+    case MsgProcessingError:
+      errorMsg =
+          "Processing error: message was deserialized, but the handler "
+          "returned false (indicating failure)";
+      break;
+    case MsgRouteError:
+      errorMsg = "Route error: message sent to unknown actor ID";
+      break;
+    case MsgValueError:
+      errorMsg =
+          "Value error: message was deserialized, but contained an illegal "
+          "value";
+      break;
+
+    default:
+      MOZ_CRASH("unknown Result code");
+      return false;
+  }
+
+  char reason[512];
+  const char* msgname = aMsg.name();
+  if (msgname[0] == '?') {
+    SprintfLiteral(reason, "(msgtype=0x%X) %s", aMsg.type(), errorMsg);
+  } else {
+    SprintfLiteral(reason, "%s %s", msgname, errorMsg);
+  }
+
+  PrintErrorMessage(mSide, channelName, reason);
+
+  // Error handled in mozilla::ipc::IPCResult.
+  if (code == MsgProcessingError) {
+    return false;
+  }
+
+  mListener->ProcessingError(code, reason);
+
+  return false;
+}
+
+void MessageChannel::OnChannelErrorFromLink() {
+  mMonitor->AssertCurrentThreadOwns();
+  MOZ_ASSERT(mChannelState == ChannelConnected);
+
+  IPC_LOG("OnChannelErrorFromLink");
+
+  if (AwaitingSyncReply()) {
+    NotifyWorkerThread();
+  }
+
+  if (mAbortOnError) {
+    // mAbortOnError is set by main actors (e.g., ContentChild) to ensure
+    // that the process terminates even if normal shutdown is prevented.
+    // A MOZ_CRASH() here is not helpful because crash reporting relies
+    // on the parent process which we know is dead or otherwise unusable.
+    //
+    // Additionally, the parent process can (and often is) killed on Android
+    // when apps are backgrounded. We don't need to report a crash for
+    // normal behavior in that case.
+    printf_stderr("Exiting due to channel error.\n");
+    ProcessChild::QuickExit();
+  }
+  mChannelState = ChannelError;
+  mMonitor->Notify();
+
+  PostErrorNotifyTask();
+}
+
+void MessageChannel::NotifyMaybeChannelError(ReleasableMonitorAutoLock& aLock) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+  aLock.AssertCurrentThreadOwns();
+  MOZ_ASSERT(mChannelState != ChannelConnected);
+
+  if (ChannelClosing == mChannelState || ChannelClosed == mChannelState) {
+    // the channel closed, but we received a "Goodbye" message warning us
+    // about it. no worries
+    mChannelState = ChannelClosed;
+    NotifyChannelClosed(aLock);
+    return;
+  }
+
+  MOZ_ASSERT(ChannelError == mChannelState);
+
+  Clear();
+
+  // IPDL assumes these notifications do not fire twice, so we do not let
+  // that happen.
+  if (mNotifiedChannelDone) {
+    return;
+  }
+  mNotifiedChannelDone = true;
+
+  // Let our listener know that the channel errored. This may cause the
+  // channel to be deleted. Release our caller's `MonitorAutoLock` before
+  // invoking the listener, as this may call back into MessageChannel, and/or
+  // cause the channel to be destroyed.
+  aLock.Unlock();
+  mListener->OnChannelError();
+}
+
+void MessageChannel::OnNotifyMaybeChannelError() {
+  AssertWorkerThread();
+  mMonitor->AssertNotCurrentThreadOwns();
+
+  // This lock guard may be reset by `NotifyMaybeChannelError` before invoking
+  // listener callbacks which may destroy this `MessageChannel`.
+  //
+  // Acquiring the lock here also allows us to ensure that
+  // `OnChannelErrorFromLink` has finished running before this task is allowed
+  // to continue.
+  ReleasableMonitorAutoLock lock(*mMonitor);
+
+  mChannelErrorTask = nullptr;
+
+  if (IsOnCxxStack()) {
+    // This used to post a 10ms delayed task; however not all
+    // nsISerialEventTarget implementations support delayed dispatch.
+    // The delay being completely arbitrary, we may not as well have any.
+    PostErrorNotifyTask();
+    return;
+  }
+
+  // This call may destroy `this`.
+  NotifyMaybeChannelError(lock);
+}
+
+void MessageChannel::PostErrorNotifyTask() {
+  mMonitor->AssertCurrentThreadOwns();
+
+  if (mChannelErrorTask) {
+    return;
+  }
+
+  // This must be the last code that runs on this thread!
+  mChannelErrorTask = NewNonOwningCancelableRunnableMethod(
+      "ipc::MessageChannel::OnNotifyMaybeChannelError", this,
+      &MessageChannel::OnNotifyMaybeChannelError);
+  mWorkerThread->Dispatch(do_AddRef(mChannelErrorTask));
+}
+
+// Special async message.
+class GoodbyeMessage : public IPC::Message {
+ public:
+  GoodbyeMessage() : IPC::Message(MSG_ROUTING_NONE, GOODBYE_MESSAGE_TYPE) {}
+  static bool Read(const Message* msg) { return true; }
+  void Log(const std::string& aPrefix, FILE* aOutf) const {
+    fputs("(special `Goodbye' message)", aOutf);
+  }
+};
+
+void MessageChannel::CloseWithError() {
+  AssertWorkerThread();
+
+  // This lock guard may be reset by `NotifyMaybeChannelError` before invoking
+  // listener callbacks which may destroy this `MessageChannel`.
+  ReleasableMonitorAutoLock lock(*mMonitor);
+
+  switch (mChannelState) {
+    case ChannelError:
+      // Already errored, ensure we notify if we haven't yet.
+      NotifyMaybeChannelError(lock);
+      return;
+    case ChannelClosed:
+      // Already closed, we can't do anything.
+      return;
+    default:
+      // Either connected or closing, immediately convert to an error, and
+      // notify.
+      MOZ_ASSERT(mChannelState == ChannelConnected ||
+                 mChannelState == ChannelClosing);
+      mLink->Close();
+      mChannelState = ChannelError;
+      NotifyMaybeChannelError(lock);
+      return;
+  }
+}
+
+void MessageChannel::NotifyImpendingShutdown() {
+  UniquePtr<Message> msg =
+      MakeUnique<Message>(MSG_ROUTING_NONE, IMPENDING_SHUTDOWN_MESSAGE_TYPE);
+  MonitorAutoLock lock(*mMonitor);
+  if (Connected()) {
+    SendMessageToLink(std::move(msg));
+  }
+}
+
+void MessageChannel::Close() {
+  AssertWorkerThread();
+  mMonitor->AssertNotCurrentThreadOwns();
+
+  // This lock guard may be reset by `Notify{ChannelClosed,MaybeChannelError}`
+  // before invoking listener callbacks which may destroy this `MessageChannel`.
+  ReleasableMonitorAutoLock lock(*mMonitor);
+
+  switch (mChannelState) {
+    case ChannelError:
+      // See bug 538586: if the listener gets deleted while the
+      // IO thread's NotifyChannelError event is still enqueued
+      // and subsequently deletes us, then the error event will
+      // also be deleted and the listener will never be notified
+      // of the channel error.
+      NotifyMaybeChannelError(lock);
+      return;
+    case ChannelClosed:
+      // Slightly unexpected but harmless; ignore.  See bug 1554244.
+      return;
+
+    default:
+      // Notify the other side that we're about to close our socket. If we've
+      // already received a Goodbye from the other side (and our state is
+      // ChannelClosing), there's no reason to send one.
+      if (ChannelConnected == mChannelState) {
+        SendMessageToLink(MakeUnique<GoodbyeMessage>());
+      }
+      mLink->Close();
+      mChannelState = ChannelClosed;
+      NotifyChannelClosed(lock);
+      return;
+  }
+}
+
+void MessageChannel::NotifyChannelClosed(ReleasableMonitorAutoLock& aLock) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+  aLock.AssertCurrentThreadOwns();
+
+  if (ChannelClosed != mChannelState) {
+    MOZ_CRASH("channel should have been closed!");
+  }
+
+  Clear();
+
+  // IPDL assumes these notifications do not fire twice, so we do not let
+  // that happen.
+  if (mNotifiedChannelDone) {
+    return;
+  }
+  mNotifiedChannelDone = true;
+
+  // Let our listener know that the channel was closed. This may cause the
+  // channel to be deleted. Release our caller's `MonitorAutoLock` before
+  // invoking the listener, as this may call back into MessageChannel, and/or
+  // cause the channel to be destroyed.
+  aLock.Unlock();
+  mListener->OnChannelClose();
+}
+
+void MessageChannel::DebugAbort(const char* file, int line, const char* cond,
+                                const char* why, bool reply) {
+  AssertWorkerThread();
+  mMonitor->AssertCurrentThreadOwns();
+
+  printf_stderr(
+      "###!!! [MessageChannel][%s][%s:%d] "
+      "Assertion (%s) failed.  %s %s\n",
+      mSide == ChildSide ? "Child" : "Parent", file, line, cond, why,
+      reply ? "(reply)" : "");
+
+  MessageQueue pending = std::move(mPending);
+  while (!pending.isEmpty()) {
+    pending.getFirst()->AssertMonitorHeld(*mMonitor);
+    printf_stderr("    [ %s%s ]\n",
+                  pending.getFirst()->Msg()->is_sync() ? "sync" : "async",
+                  pending.getFirst()->Msg()->is_reply() ? "reply" : "");
+    pending.popFirst();
+  }
+
+  MOZ_CRASH_UNSAFE(why);
+}
+
+void MessageChannel::AddProfilerMarker(const IPC::Message& aMessage,
+                                       MessageDirection aDirection) {
+  mMonitor->AssertCurrentThreadOwns();
+
+  if (profiler_feature_active(ProfilerFeature::IPCMessages)) {
+    base::ProcessId pid = mListener->OtherPidMaybeInvalid();
+    // Only record markers for IPCs with a valid pid.
+    // And if one of the profiler mutexes is locked on this thread, don't record
+    // markers, because we don't want to expose profiler IPCs due to the
+    // profiler itself, and also to avoid possible re-entrancy issues.
+    if (pid != base::kInvalidProcessId &&
+        !profiler_is_locked_on_current_thread()) {
+      // The current timestamp must be given to the `IPCMarker` payload.
+      [[maybe_unused]] const TimeStamp now = TimeStamp::Now();
+      bool isThreadBeingProfiled =
+          profiler_thread_is_being_profiled_for_markers();
+      PROFILER_MARKER(
+          "IPC", IPC,
+          mozilla::MarkerOptions(
+              mozilla::MarkerTiming::InstantAt(now),
+              // If the thread is being profiled, add the marker to
+              // the current thread. If the thread is not being
+              // profiled, add the marker to the main thread. It
+              // will appear in the main thread's IPC track. Profiler analysis
+              // UI correlates all the IPC markers from different threads and
+              // generates processed markers.
+              isThreadBeingProfiled ? mozilla::MarkerThreadId::CurrentThread()
+                                    : mozilla::MarkerThreadId::MainThread()),
+          IPCMarker, now, now, pid, aMessage.seqno(), aMessage.type(), mSide,
+          aDirection, MessagePhase::Endpoint, aMessage.is_sync(),
+          // aOriginThreadId: If the thread is being profiled, do not include a
+          // thread ID, as it's the same as the markers. Only include this field
+          // when the marker is being sent from another thread.
+          isThreadBeingProfiled ? mozilla::MarkerThreadId{}
+                                : mozilla::MarkerThreadId::CurrentThread());
+    }
+  }
+}
+
+void MessageChannel::EndTimeout() {
+  mMonitor->AssertCurrentThreadOwns();
+
+  IPC_LOG("Ending timeout of seqno=%d", mTimedOutMessageSeqno);
+  mTimedOutMessageSeqno = 0;
+  mTimedOutMessageNestedLevel = 0;
+
+  RepostAllMessages();
+}
+
+void MessageChannel::RepostAllMessages() {
+  mMonitor->AssertCurrentThreadOwns();
+
+  bool needRepost = false;
+  for (MessageTask* task : mPending) {
+    task->AssertMonitorHeld(*mMonitor);
+    if (!task->IsScheduled()) {
+      needRepost = true;
+      break;
+    }
+  }
+  if (!needRepost) {
+    // If everything is already scheduled to run, do nothing.
+    return;
+  }
+
+  // In some cases we may have deferred dispatch of some messages in the
+  // queue. Now we want to run them again. However, we can't just re-post
+  // those messages since the messages after them in mPending would then be
+  // before them in the event queue. So instead we cancel everything and
+  // re-post all messages in the correct order.
+  MessageQueue queue = std::move(mPending);
+  while (RefPtr<MessageTask> task = queue.popFirst()) {
+    task->AssertMonitorHeld(*mMonitor);
+    RefPtr<MessageTask> newTask = new MessageTask(this, std::move(task->Msg()));
+    newTask->AssertMonitorHeld(*mMonitor);
+    mPending.insertBack(newTask);
+    newTask->Post();
+  }
+
+  AssertMaybeDeferredCountCorrect();
+}
+
+void MessageChannel::CancelTransaction(int transaction) {
+  mMonitor->AssertCurrentThreadOwns();
+
+  // When we cancel a transaction, we need to behave as if there's no longer
+  // any IPC on the stack. Anything we were dispatching or sending will get
+  // canceled. Consequently, we have to update the state variables below.
+  //
+  // We also need to ensure that when any IPC functions on the stack return,
+  // they don't reset these values using an RAII class like AutoSetValue. To
+  // avoid that, these RAII classes check if the variable they set has been
+  // tampered with (by us). If so, they don't reset the variable to the old
+  // value.
+
+  IPC_LOG("CancelTransaction: xid=%d", transaction);
+
+  // An unusual case: We timed out a transaction which the other side then
+  // cancelled. In this case we just leave the timedout state and try to
+  // forget this ever happened.
+  if (transaction == mTimedOutMessageSeqno) {
+    IPC_LOG("Cancelled timed out message %d", mTimedOutMessageSeqno);
+    EndTimeout();
+
+    // Normally mCurrentTransaction == 0 here. But it can be non-zero if:
+    // 1. Parent sends NESTED_INSIDE_SYNC message H.
+    // 2. Parent times out H.
+    // 3. Child dispatches H and sends nested message H' (same transaction).
+    // 4. Parent dispatches H' and cancels.
+    MOZ_RELEASE_ASSERT(!mTransactionStack ||
+                       mTransactionStack->TransactionID() == transaction);
+    if (mTransactionStack) {
+      mTransactionStack->Cancel();
+    }
+  } else {
+    MOZ_RELEASE_ASSERT(mTransactionStack->TransactionID() == transaction);
+    mTransactionStack->Cancel();
+  }
+
+  bool foundSync = false;
+  for (MessageTask* p = mPending.getFirst(); p;) {
+    p->AssertMonitorHeld(*mMonitor);
+    UniquePtr<Message>& msg = p->Msg();
+
+    // If there was a race between the parent and the child, then we may
+    // have a queued sync message. We want to drop this message from the
+    // queue since if will get cancelled along with the transaction being
+    // cancelled. This happens if the message in the queue is
+    // NESTED_INSIDE_SYNC.
+    if (msg->is_sync() && msg->nested_level() != IPC::Message::NOT_NESTED) {
+      MOZ_RELEASE_ASSERT(!foundSync);
+      MOZ_RELEASE_ASSERT(msg->transaction_id() != transaction);
+      IPC_LOG("Removing msg from queue seqno=%d xid=%d", msg->seqno(),
+              msg->transaction_id());
+      foundSync = true;
+      if (!IsAlwaysDeferred(*msg)) {
+        mMaybeDeferredPendingCount--;
+      }
+      p = p->removeAndGetNext();
+      continue;
+    }
+
+    p = p->getNext();
+  }
+
+  AssertMaybeDeferredCountCorrect();
+}
+
+void MessageChannel::CancelCurrentTransaction() {
+  MonitorAutoLock lock(*mMonitor);
+  if (DispatchingSyncMessageNestedLevel() >= IPC::Message::NESTED_INSIDE_SYNC) {
+    if (DispatchingSyncMessageNestedLevel() ==
+            IPC::Message::NESTED_INSIDE_CPOW ||
+        DispatchingAsyncMessageNestedLevel() ==
+            IPC::Message::NESTED_INSIDE_CPOW) {
+      mListener->IntentionalCrash();
+    }
+
+    IPC_LOG("Cancel requested: current xid=%d",
+            CurrentNestedInsideSyncTransaction());
+    MOZ_RELEASE_ASSERT(DispatchingSyncMessage());
+    auto cancel =
+        MakeUnique<CancelMessage>(CurrentNestedInsideSyncTransaction());
+    CancelTransaction(CurrentNestedInsideSyncTransaction());
+    SendMessageToLink(std::move(cancel));
+  }
+}
+
+void CancelCPOWs() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (gParentProcessBlocker) {
+    mozilla::Telemetry::Accumulate(mozilla::Telemetry::IPC_TRANSACTION_CANCEL,
+                                   true);
+    gParentProcessBlocker->CancelCurrentTransaction();
+  }
+}
+
+bool MessageChannel::IsCrossProcess() const {
+  mMonitor->AssertCurrentThreadOwns();
+  return mIsCrossProcess;
+}
+
+void MessageChannel::SetIsCrossProcess(bool aIsCrossProcess) {
+  mMonitor->AssertCurrentThreadOwns();
+  if (aIsCrossProcess == mIsCrossProcess) {
+    return;
+  }
+  mIsCrossProcess = aIsCrossProcess;
+  if (mIsCrossProcess) {
+    ChannelCountReporter::Increment(mName);
+  } else {
+    ChannelCountReporter::Decrement(mName);
+  }
+}
+
+NS_IMPL_ISUPPORTS(MessageChannel::WorkerTargetShutdownTask,
+                  nsITargetShutdownTask)
+
+MessageChannel::WorkerTargetShutdownTask::WorkerTargetShutdownTask(
+    nsISerialEventTarget* aTarget, MessageChannel* aChannel)
+    : mTarget(aTarget), mChannel(aChannel) {}
+
+void MessageChannel::WorkerTargetShutdownTask::TargetShutdown() {
+  MOZ_RELEASE_ASSERT(mTarget->IsOnCurrentThread());
+  IPC_LOG("Closing channel due to event target shutdown");
+  if (MessageChannel* channel = std::exchange(mChannel, nullptr)) {
+    channel->Close();
+  }
+}
+
+void MessageChannel::WorkerTargetShutdownTask::Clear() {
+  MOZ_RELEASE_ASSERT(mTarget->IsOnCurrentThread());
+  mChannel = nullptr;
+}
+
+NS_IMPL_ISUPPORTS_INHERITED0(MessageChannel::FlushLazySendMessagesRunnable,
+                             CancelableRunnable)
+
+MessageChannel::FlushLazySendMessagesRunnable::FlushLazySendMessagesRunnable(
+    MessageChannel* aChannel)
+    : CancelableRunnable("MessageChannel::FlushLazyMessagesRunnable"),
+      mChannel(aChannel) {}
+
+NS_IMETHODIMP MessageChannel::FlushLazySendMessagesRunnable::Run() {
+  if (mChannel) {
+    MonitorAutoLock lock(*mChannel->mMonitor);
+    MOZ_ASSERT(mChannel->mFlushLazySendTask == this);
+    mChannel->FlushLazySendMessages();
+  }
+  return NS_OK;
+}
+
+nsresult MessageChannel::FlushLazySendMessagesRunnable::Cancel() {
+  mQueue.Clear();
+  mChannel = nullptr;
+  return NS_OK;
+}
+
+void MessageChannel::FlushLazySendMessagesRunnable::PushMessage(
+    UniquePtr<Message> aMsg) {
+  MOZ_ASSERT(mChannel);
+  mQueue.AppendElement(std::move(aMsg));
+}
+
+nsTArray<UniquePtr<IPC::Message>>
+MessageChannel::FlushLazySendMessagesRunnable::TakeMessages() {
+  mChannel = nullptr;
+  return std::move(mQueue);
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/MessageChannel.h b/ipc/glue/MessageChannel.h
new file mode 100644
index 0000000000..e52ce7974f
--- /dev/null
+++ b/ipc/glue/MessageChannel.h
@@ -0,0 +1,878 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=4 et :
+ */
+/* 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 ipc_glue_MessageChannel_h
+#define ipc_glue_MessageChannel_h 1
+
+#include "ipc/EnumSerializer.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/BaseProfilerMarkers.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/Vector.h"
+#if defined(OS_WIN)
+#  include "mozilla/ipc/Neutering.h"
+#endif  // defined(OS_WIN)
+
+#include <functional>
+#include <map>
+#include <stack>
+#include <vector>
+
+#include "MessageLink.h"  // for HasResultCodes
+#include "mozilla/ipc/ScopedPort.h"
+#include "nsITargetShutdownTask.h"
+
+#ifdef FUZZING_SNAPSHOT
+#  include "mozilla/fuzzing/IPCFuzzController.h"
+#endif
+
+class MessageLoop;
+
+namespace IPC {
+template <typename T>
+struct ParamTraits;
+}
+
+namespace mozilla {
+namespace ipc {
+
+class IToplevelProtocol;
+class ActorLifecycleProxy;
+
+class RefCountedMonitor : public Monitor {
+ public:
+  RefCountedMonitor() : Monitor("mozilla.ipc.MessageChannel.mMonitor") {}
+
+  void AssertSameMonitor(const RefCountedMonitor& aOther) const
+      MOZ_REQUIRES(*this) MOZ_ASSERT_CAPABILITY(aOther) {
+    MOZ_ASSERT(this == &aOther);
+  }
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefCountedMonitor)
+
+ private:
+  ~RefCountedMonitor() = default;
+};
+
+enum class MessageDirection {
+  eSending,
+  eReceiving,
+};
+
+enum class MessagePhase {
+  Endpoint,
+  TransferStart,
+  TransferEnd,
+};
+
+enum class SyncSendError {
+  SendSuccess,
+  PreviousTimeout,
+  SendingCPOWWhileDispatchingSync,
+  SendingCPOWWhileDispatchingUrgent,
+  NotConnectedBeforeSend,
+  DisconnectedDuringSend,
+  CancelledBeforeSend,
+  CancelledAfterSend,
+  TimedOut,
+  ReplyError,
+};
+
+enum class ResponseRejectReason {
+  SendError,
+  ChannelClosed,
+  HandlerRejected,
+  ActorDestroyed,
+  ResolverDestroyed,
+  EndGuard_,
+};
+
+template <typename T>
+using ResolveCallback = std::function<void(T&&)>;
+
+using RejectCallback = std::function<void(ResponseRejectReason)>;
+
+enum ChannelState {
+  ChannelClosed,
+  ChannelConnected,
+  ChannelClosing,
+  ChannelError
+};
+
+class AutoEnterTransaction;
+
+class MessageChannel : HasResultCodes {
+  friend class PortLink;
+
+  typedef mozilla::Monitor Monitor;
+
+ public:
+  using Message = IPC::Message;
+
+  struct UntypedCallbackHolder {
+    UntypedCallbackHolder(int32_t aActorId, Message::msgid_t aReplyMsgId,
+                          RejectCallback&& aReject)
+        : mActorId(aActorId),
+          mReplyMsgId(aReplyMsgId),
+          mReject(std::move(aReject)) {}
+
+    virtual ~UntypedCallbackHolder() = default;
+
+    void Reject(ResponseRejectReason&& aReason) { mReject(std::move(aReason)); }
+
+    int32_t mActorId;
+    Message::msgid_t mReplyMsgId;
+    RejectCallback mReject;
+  };
+
+  template <typename Value>
+  struct CallbackHolder : public UntypedCallbackHolder {
+    CallbackHolder(int32_t aActorId, Message::msgid_t aReplyMsgId,
+                   ResolveCallback<Value>&& aResolve, RejectCallback&& aReject)
+        : UntypedCallbackHolder(aActorId, aReplyMsgId, std::move(aReject)),
+          mResolve(std::move(aResolve)) {}
+
+    void Resolve(Value&& aReason) { mResolve(std::move(aReason)); }
+
+    ResolveCallback<Value> mResolve;
+  };
+
+ private:
+  static Atomic<size_t> gUnresolvedResponses;
+  friend class PendingResponseReporter;
+
+ public:
+  static constexpr int32_t kNoTimeout = INT32_MIN;
+
+  using ScopedPort = mozilla::ipc::ScopedPort;
+
+  explicit MessageChannel(const char* aName, IToplevelProtocol* aListener);
+  ~MessageChannel();
+
+  IToplevelProtocol* Listener() const { return mListener; }
+
+  // Returns the event target which the worker lives on and must be used for
+  // operations on the current thread. Only safe to access after the
+  // MessageChannel has been opened.
+  nsISerialEventTarget* GetWorkerEventTarget() const { return mWorkerThread; }
+
+  // "Open" a connection using an existing ScopedPort. The ScopedPort must be
+  // valid and connected to a remote.
+  //
+  // The `aEventTarget` parameter must be on the current thread.
+  bool Open(ScopedPort aPort, Side aSide, const nsID& aMessageChannelId,
+            nsISerialEventTarget* aEventTarget = nullptr);
+
+  // "Open" a connection to another thread in the same process.
+  //
+  // Returns true if the transport layer was successfully connected,
+  // i.e., mChannelState == ChannelConnected.
+  //
+  // For more details on the process of opening a channel between
+  // threads, see the extended comment on this function
+  // in MessageChannel.cpp.
+  bool Open(MessageChannel* aTargetChan, nsISerialEventTarget* aEventTarget,
+            Side aSide);
+
+  // "Open" a connection to an actor on the current thread.
+  //
+  // Returns true if the transport layer was successfully connected,
+  // i.e., mChannelState == ChannelConnected.
+  //
+  // Same-thread channels may not perform synchronous or blocking message
+  // sends, to avoid deadlocks.
+  bool OpenOnSameThread(MessageChannel* aTargetChan, Side aSide);
+
+  /**
+   * This sends a special message that is processed on the IO thread, so that
+   * other actors can know that the process will soon shutdown.
+   */
+  void NotifyImpendingShutdown() MOZ_EXCLUDES(*mMonitor);
+
+  // Close the underlying transport channel.
+  void Close() MOZ_EXCLUDES(*mMonitor);
+
+  // Close the underlying transport channel, treating the closure as a
+  // connection error.
+  void CloseWithError() MOZ_EXCLUDES(*mMonitor);
+
+  void SetAbortOnError(bool abort) MOZ_EXCLUDES(*mMonitor) {
+    MonitorAutoLock lock(*mMonitor);
+    mAbortOnError = abort;
+  }
+
+  // Call aInvoke for each pending message until it returns false.
+  // XXX: You must get permission from an IPC peer to use this function
+  //      since it requires custom deserialization and re-orders events.
+  void PeekMessages(const std::function<bool(const Message& aMsg)>& aInvoke)
+      MOZ_EXCLUDES(*mMonitor);
+
+  // Misc. behavioral traits consumers can request for this channel
+  enum ChannelFlags {
+    REQUIRE_DEFAULT = 0,
+    // Windows: if this channel operates on the UI thread, indicates
+    // WindowsMessageLoop code should enable deferred native message
+    // handling to prevent deadlocks. Should only be used for protocols
+    // that manage child processes which might create native UI, like
+    // plugins.
+    REQUIRE_DEFERRED_MESSAGE_PROTECTION = 1 << 0,
+  };
+  void SetChannelFlags(ChannelFlags aFlags) { mFlags = aFlags; }
+  ChannelFlags GetChannelFlags() { return mFlags; }
+
+  // Asynchronously send a message to the other side of the channel
+  bool Send(UniquePtr<Message> aMsg) MOZ_EXCLUDES(*mMonitor);
+
+  // Asynchronously send a message to the other side of the channel
+  // and wait for asynchronous reply.
+  template <typename Value>
+  void Send(UniquePtr<Message> aMsg, int32_t aActorId,
+            Message::msgid_t aReplyMsgId, ResolveCallback<Value>&& aResolve,
+            RejectCallback&& aReject) MOZ_EXCLUDES(*mMonitor) {
+    int32_t seqno = NextSeqno();
+    aMsg->set_seqno(seqno);
+    if (!Send(std::move(aMsg))) {
+      aReject(ResponseRejectReason::SendError);
+      return;
+    }
+
+    UniquePtr<UntypedCallbackHolder> callback =
+        MakeUnique<CallbackHolder<Value>>(
+            aActorId, aReplyMsgId, std::move(aResolve), std::move(aReject));
+    mPendingResponses.insert(std::make_pair(seqno, std::move(callback)));
+    gUnresolvedResponses++;
+  }
+
+  bool SendBuildIDsMatchMessage(const char* aParentBuildID)
+      MOZ_EXCLUDES(*mMonitor);
+  bool DoBuildIDsMatch() MOZ_EXCLUDES(*mMonitor) {
+    MonitorAutoLock lock(*mMonitor);
+    return mBuildIDsConfirmedMatch;
+  }
+
+  // Synchronously send |aMsg| (i.e., wait for |aReply|)
+  bool Send(UniquePtr<Message> aMsg, UniquePtr<Message>* aReply)
+      MOZ_EXCLUDES(*mMonitor);
+
+  bool CanSend() const MOZ_EXCLUDES(*mMonitor);
+
+  // Remove and return a callback that needs reply
+  UniquePtr<UntypedCallbackHolder> PopCallback(const Message& aMsg,
+                                               int32_t aActorId);
+
+  // Used to reject and remove pending responses owned by the given
+  // actor when it's about to be destroyed.
+  void RejectPendingResponsesForActor(int32_t aActorId);
+
+  // If sending a sync message returns an error, this function gives a more
+  // descriptive error message.
+  SyncSendError LastSendError() const {
+    AssertWorkerThread();
+    return mLastSendError;
+  }
+
+  void SetReplyTimeoutMs(int32_t aTimeoutMs);
+
+  bool IsOnCxxStack() const { return mOnCxxStack; }
+
+  void CancelCurrentTransaction() MOZ_EXCLUDES(*mMonitor);
+
+  // IsClosed and NumQueuedMessages are safe to call from any thread, but
+  // may provide an out-of-date value.
+  bool IsClosed() MOZ_EXCLUDES(*mMonitor) {
+    MonitorAutoLock lock(*mMonitor);
+    return IsClosedLocked();
+  }
+  bool IsClosedLocked() const MOZ_REQUIRES(*mMonitor) {
+    mMonitor->AssertCurrentThreadOwns();
+    return mLink ? mLink->IsClosed() : true;
+  }
+
+  static bool IsPumpingMessages() { return sIsPumpingMessages; }
+  static void SetIsPumpingMessages(bool aIsPumping) {
+    sIsPumpingMessages = aIsPumping;
+  }
+
+  /**
+   * Does this MessageChannel currently cross process boundaries?
+   */
+  bool IsCrossProcess() const MOZ_REQUIRES(*mMonitor);
+  void SetIsCrossProcess(bool aIsCrossProcess) MOZ_REQUIRES(*mMonitor);
+
+  nsID GetMessageChannelId() const {
+    MonitorAutoLock lock(*mMonitor);
+    return mMessageChannelId;
+  }
+
+#ifdef FUZZING_SNAPSHOT
+  Maybe<mojo::core::ports::PortName> GetPortName() {
+    MonitorAutoLock lock(*mMonitor);
+    return mLink ? mLink->GetPortName() : Nothing();
+  }
+#endif
+
+#ifdef OS_WIN
+  struct MOZ_STACK_CLASS SyncStackFrame {
+    explicit SyncStackFrame(MessageChannel* channel);
+    ~SyncStackFrame();
+
+    bool mSpinNestedEvents;
+    bool mListenerNotified;
+    MessageChannel* mChannel;
+
+    // The previous stack frame for this channel.
+    SyncStackFrame* mPrev;
+
+    // The previous stack frame on any channel.
+    SyncStackFrame* mStaticPrev;
+  };
+  friend struct MessageChannel::SyncStackFrame;
+
+  static bool IsSpinLoopActive() {
+    for (SyncStackFrame* frame = sStaticTopFrame; frame; frame = frame->mPrev) {
+      if (frame->mSpinNestedEvents) return true;
+    }
+    return false;
+  }
+
+ protected:
+  // The deepest sync stack frame for this channel.
+  SyncStackFrame* mTopFrame = nullptr;
+
+  bool mIsSyncWaitingOnNonMainThread = false;
+
+  // The deepest sync stack frame on any channel.
+  static SyncStackFrame* sStaticTopFrame;
+
+ public:
+  void ProcessNativeEventsInInterruptCall();
+  static void NotifyGeckoEventDispatch();
+
+ private:
+  void SpinInternalEventLoop();
+#endif  // defined(OS_WIN)
+
+ private:
+  void PostErrorNotifyTask() MOZ_REQUIRES(*mMonitor);
+  void OnNotifyMaybeChannelError() MOZ_EXCLUDES(*mMonitor);
+  void ReportConnectionError(const char* aFunctionName,
+                             const uint32_t aMsgTyp) const
+      MOZ_REQUIRES(*mMonitor);
+  void ReportMessageRouteError(const char* channelName) const
+      MOZ_EXCLUDES(*mMonitor);
+  bool MaybeHandleError(Result code, const Message& aMsg,
+                        const char* channelName) MOZ_EXCLUDES(*mMonitor);
+
+  void Clear() MOZ_REQUIRES(*mMonitor);
+
+  bool HasPendingEvents() MOZ_REQUIRES(*mMonitor);
+
+  void ProcessPendingRequests(ActorLifecycleProxy* aProxy,
+                              AutoEnterTransaction& aTransaction)
+      MOZ_REQUIRES(*mMonitor);
+  bool ProcessPendingRequest(ActorLifecycleProxy* aProxy,
+                             UniquePtr<Message> aUrgent)
+      MOZ_REQUIRES(*mMonitor);
+
+  void EnqueuePendingMessages() MOZ_REQUIRES(*mMonitor);
+
+  // Dispatches an incoming message to its appropriate handler.
+  void DispatchMessage(ActorLifecycleProxy* aProxy, UniquePtr<Message> aMsg)
+      MOZ_REQUIRES(*mMonitor);
+
+  // DispatchMessage will route to one of these functions depending on the
+  // protocol type of the message.
+  void DispatchSyncMessage(ActorLifecycleProxy* aProxy, const Message& aMsg,
+                           UniquePtr<Message>& aReply) MOZ_EXCLUDES(*mMonitor);
+  void DispatchAsyncMessage(ActorLifecycleProxy* aProxy, const Message& aMsg)
+      MOZ_EXCLUDES(*mMonitor);
+
+  // Return true if the wait ended because a notification was received.
+  //
+  // Return false if the time elapsed from when we started the process of
+  // waiting until afterwards exceeded the currently allotted timeout.
+  // That *DOES NOT* mean false => "no event" (== timeout); there are many
+  // circumstances that could cause the measured elapsed time to exceed the
+  // timeout EVEN WHEN we were notified.
+  //
+  // So in sum: true is a meaningful return value; false isn't,
+  // necessarily.
+  bool WaitForSyncNotify() MOZ_REQUIRES(*mMonitor);
+
+  bool WaitResponse(bool aWaitTimedOut);
+
+  bool ShouldContinueFromTimeout() MOZ_REQUIRES(*mMonitor);
+
+  void EndTimeout() MOZ_REQUIRES(*mMonitor);
+  void CancelTransaction(int transaction) MOZ_REQUIRES(*mMonitor);
+
+  void RepostAllMessages() MOZ_REQUIRES(*mMonitor);
+
+  int32_t NextSeqno() {
+    AssertWorkerThread();
+    return (mSide == ChildSide) ? --mNextSeqno : ++mNextSeqno;
+  }
+
+  void DebugAbort(const char* file, int line, const char* cond, const char* why,
+                  bool reply = false) MOZ_REQUIRES(*mMonitor);
+
+  void AddProfilerMarker(const IPC::Message& aMessage,
+                         MessageDirection aDirection) MOZ_REQUIRES(*mMonitor);
+
+ private:
+  // Returns true if we're dispatching an async message's callback.
+  bool DispatchingAsyncMessage() const {
+    AssertWorkerThread();
+    return mDispatchingAsyncMessage;
+  }
+
+  int DispatchingAsyncMessageNestedLevel() const {
+    AssertWorkerThread();
+    return mDispatchingAsyncMessageNestedLevel;
+  }
+
+  // Check if there is still a live connection to our peer. This may change to
+  // `false` at any time due to the connection to our peer being closed or
+  // dropped (e.g. due to a crash).
+  bool Connected() const MOZ_REQUIRES(*mMonitor);
+
+  // Check if there is either still a live connection to our peer, or we have
+  // received a `Goodbye` from our peer, and are actively shutting down our
+  // connection with our peer.
+  bool ConnectedOrClosing() const MOZ_REQUIRES(*mMonitor);
+
+ private:
+  // Executed on the IO thread.
+  void NotifyWorkerThread() MOZ_REQUIRES(*mMonitor);
+
+  // Return true if |aMsg| is a special message targeted at the IO
+  // thread, in which case it shouldn't be delivered to the worker.
+  bool MaybeInterceptSpecialIOMessage(const Message& aMsg)
+      MOZ_REQUIRES(*mMonitor);
+
+  // Returns true if ShouldDeferMessage(aMsg) is guaranteed to return true.
+  // Otherwise, the result of ShouldDeferMessage(aMsg) may be true or false,
+  // depending on context.
+  static bool IsAlwaysDeferred(const Message& aMsg);
+
+  // Helper for sending a message via the link. If the message is [LazySend], it
+  // will be queued, and if the message is not-[LazySend], it will flush any
+  // pending [LazySend] messages.
+  void SendMessageToLink(UniquePtr<Message> aMsg) MOZ_REQUIRES(*mMonitor);
+
+  // Called to flush [LazySend] messages to the link.
+  void FlushLazySendMessages() MOZ_REQUIRES(*mMonitor);
+
+  bool WasTransactionCanceled(int transaction);
+  bool ShouldDeferMessage(const Message& aMsg) MOZ_REQUIRES(*mMonitor);
+  void OnMessageReceivedFromLink(UniquePtr<Message> aMsg)
+      MOZ_REQUIRES(*mMonitor);
+  void OnChannelErrorFromLink() MOZ_REQUIRES(*mMonitor);
+
+ private:
+  // Clear this channel, and notify the listener that the channel has either
+  // closed or errored.
+  //
+  // These methods must be called on the worker thread, passing in a
+  // `ReleasableMonitorAutoLock`. This lock guard will be reset before the
+  // listener is called, allowing for the monitor to be unlocked before the
+  // MessageChannel is potentially destroyed.
+  void NotifyChannelClosed(ReleasableMonitorAutoLock& aLock)
+      MOZ_REQUIRES(*mMonitor);
+  void NotifyMaybeChannelError(ReleasableMonitorAutoLock& aLock)
+      MOZ_REQUIRES(*mMonitor);
+
+ private:
+  void AssertWorkerThread() const {
+    MOZ_ASSERT(mWorkerThread, "Channel hasn't been opened yet");
+    MOZ_RELEASE_ASSERT(mWorkerThread && mWorkerThread->IsOnCurrentThread(),
+                       "not on worker thread!");
+  }
+
+ private:
+  class MessageTask : public CancelableRunnable,
+                      public LinkedListElement<RefPtr<MessageTask>>,
+                      public nsIRunnablePriority,
+                      public nsIRunnableIPCMessageType {
+   public:
+    explicit MessageTask(MessageChannel* aChannel, UniquePtr<Message> aMessage);
+    MessageTask() = delete;
+    MessageTask(const MessageTask&) = delete;
+
+    NS_DECL_ISUPPORTS_INHERITED
+
+    NS_IMETHOD Run() override;
+    nsresult Cancel() override;
+    NS_IMETHOD GetPriority(uint32_t* aPriority) override;
+    NS_DECL_NSIRUNNABLEIPCMESSAGETYPE
+    void Post() MOZ_REQUIRES(*mMonitor);
+
+    bool IsScheduled() const MOZ_REQUIRES(*mMonitor) {
+      mMonitor->AssertCurrentThreadOwns();
+      return mScheduled;
+    }
+
+    UniquePtr<Message>& Msg() MOZ_REQUIRES(*mMonitor) {
+      MOZ_DIAGNOSTIC_ASSERT(mMessage, "message was moved");
+      return mMessage;
+    }
+    const UniquePtr<Message>& Msg() const MOZ_REQUIRES(*mMonitor) {
+      MOZ_DIAGNOSTIC_ASSERT(mMessage, "message was moved");
+      return mMessage;
+    }
+
+    void AssertMonitorHeld(const RefCountedMonitor& aMonitor)
+        MOZ_REQUIRES(aMonitor) MOZ_ASSERT_CAPABILITY(*mMonitor) {
+      aMonitor.AssertSameMonitor(*mMonitor);
+    }
+
+   private:
+    ~MessageTask();
+
+    MessageChannel* Channel() MOZ_REQUIRES(*mMonitor) {
+      mMonitor->AssertCurrentThreadOwns();
+      MOZ_RELEASE_ASSERT(isInList());
+      return mChannel;
+    }
+
+    // The connected MessageChannel's monitor. Guards `mChannel` and
+    // `mScheduled`.
+    RefPtr<RefCountedMonitor> const mMonitor;
+    // The channel which this MessageTask is associated with. Only valid while
+    // `mMonitor` is held, and this MessageTask `isInList()`.
+    MessageChannel* const mChannel;
+    UniquePtr<Message> mMessage MOZ_GUARDED_BY(*mMonitor);
+    uint32_t const mPriority;
+    bool mScheduled : 1 MOZ_GUARDED_BY(*mMonitor);
+#ifdef FUZZING_SNAPSHOT
+    const bool mIsFuzzMsg;
+    bool mFuzzStopped MOZ_GUARDED_BY(*mMonitor);
+#endif
+  };
+
+  bool ShouldRunMessage(const Message& aMsg) MOZ_REQUIRES(*mMonitor);
+  void RunMessage(ActorLifecycleProxy* aProxy, MessageTask& aTask)
+      MOZ_REQUIRES(*mMonitor);
+
+  class WorkerTargetShutdownTask final : public nsITargetShutdownTask {
+   public:
+    NS_DECL_THREADSAFE_ISUPPORTS
+
+    WorkerTargetShutdownTask(nsISerialEventTarget* aTarget,
+                             MessageChannel* aChannel);
+
+    void TargetShutdown() override;
+    void Clear();
+
+   private:
+    ~WorkerTargetShutdownTask() = default;
+
+    const nsCOMPtr<nsISerialEventTarget> mTarget;
+    // Cleared by MessageChannel before it is destroyed.
+    MessageChannel* MOZ_NON_OWNING_REF mChannel;
+  };
+
+  class FlushLazySendMessagesRunnable final : public CancelableRunnable {
+   public:
+    explicit FlushLazySendMessagesRunnable(MessageChannel* aChannel);
+
+    NS_DECL_ISUPPORTS_INHERITED
+
+    NS_IMETHOD Run() override;
+    nsresult Cancel() override;
+
+    void PushMessage(UniquePtr<Message> aMsg);
+    nsTArray<UniquePtr<Message>> TakeMessages();
+
+   private:
+    ~FlushLazySendMessagesRunnable() = default;
+
+    // Cleared by MessageChannel before it is destroyed.
+    MessageChannel* MOZ_NON_OWNING_REF mChannel;
+
+    // LazySend messages which haven't been sent yet, but will be sent as soon
+    // as a non-LazySend message is sent, or this runnable is executed.
+    nsTArray<UniquePtr<Message>> mQueue;
+  };
+
+  typedef LinkedList<RefPtr<MessageTask>> MessageQueue;
+  typedef std::map<size_t, UniquePtr<UntypedCallbackHolder>> CallbackMap;
+  typedef IPC::Message::msgid_t msgid_t;
+
+ private:
+  // This will be a string literal, so lifetime is not an issue.
+  const char* const mName;
+
+  // ID for each MessageChannel. Set when it is opened, and never cleared
+  // afterwards.
+  //
+  // This ID is only intended for diagnostics, debugging, and reporting
+  // purposes, and shouldn't be used for message routing or permissions checks.
+  nsID mMessageChannelId MOZ_GUARDED_BY(*mMonitor) = {};
+
+  // Based on presumption the listener owns and overlives the channel,
+  // this is never nullified.
+  IToplevelProtocol* const mListener;
+
+  // This monitor guards all state in this MessageChannel, except where
+  // otherwise noted. It is refcounted so a reference to it can be shared with
+  // IPC listener objects which need to access weak references to this
+  // `MessageChannel`.
+  RefPtr<RefCountedMonitor> const mMonitor;
+
+  ChannelState mChannelState MOZ_GUARDED_BY(*mMonitor) = ChannelClosed;
+  Side mSide = UnknownSide;
+  bool mIsCrossProcess MOZ_GUARDED_BY(*mMonitor) = false;
+  UniquePtr<MessageLink> mLink MOZ_GUARDED_BY(*mMonitor);
+
+  // NotifyMaybeChannelError runnable
+  RefPtr<CancelableRunnable> mChannelErrorTask MOZ_GUARDED_BY(*mMonitor);
+
+  // Thread we are allowed to send and receive on.  Set in Open(); never
+  // changed, and we can only call Open() once.  We shouldn't be accessing
+  // from multiple threads before Open().
+  nsCOMPtr<nsISerialEventTarget> mWorkerThread;
+
+  // Shutdown task to close the channel before mWorkerThread goes away.
+  RefPtr<WorkerTargetShutdownTask> mShutdownTask MOZ_GUARDED_BY(*mMonitor);
+
+  // Task to force sending lazy messages when mQueuedLazyMessages is non-empty.
+  RefPtr<FlushLazySendMessagesRunnable> mFlushLazySendTask
+      MOZ_GUARDED_BY(*mMonitor);
+
+  // Timeout periods are broken up in two to prevent system suspension from
+  // triggering an abort. This method (called by WaitForEvent with a 'did
+  // timeout' flag) decides if we should wait again for half of mTimeoutMs
+  // or give up.
+  // only accessed on WorkerThread
+  int32_t mTimeoutMs = kNoTimeout;
+  bool mInTimeoutSecondHalf = false;
+
+  // Worker-thread only; sequence numbers for messages that require
+  // replies.
+  int32_t mNextSeqno = 0;
+
+  static bool sIsPumpingMessages;
+
+  // If ::Send returns false, this gives a more descriptive error.
+  SyncSendError mLastSendError = SyncSendError::SendSuccess;
+
+  template <class T>
+  class AutoSetValue {
+   public:
+    explicit AutoSetValue(T& var, const T& newValue)
+        : mVar(var), mPrev(var), mNew(newValue) {
+      mVar = newValue;
+    }
+    ~AutoSetValue() {
+      // The value may have been zeroed if the transaction was
+      // canceled. In that case we shouldn't return it to its previous
+      // value.
+      if (mVar == mNew) {
+        mVar = mPrev;
+      }
+    }
+
+   private:
+    T& mVar;
+    T mPrev;
+    T mNew;
+  };
+
+  bool mDispatchingAsyncMessage = false;
+  int mDispatchingAsyncMessageNestedLevel = 0;
+
+  // When we send an urgent request from the parent process, we could race
+  // with an RPC message that was issued by the child beforehand. In this
+  // case, if the parent were to wake up while waiting for the urgent reply,
+  // and process the RPC, it could send an additional urgent message. The
+  // child would wake up to process the urgent message (as it always will),
+  // then send a reply, which could be received by the parent out-of-order
+  // with respect to the first urgent reply.
+  //
+  // To address this problem, urgent or RPC requests are associated with a
+  // "transaction". Whenever one side of the channel wishes to start a
+  // chain of RPC/urgent messages, it allocates a new transaction ID. Any
+  // messages the parent receives, not apart of this transaction, are
+  // deferred. When issuing RPC/urgent requests on top of a started
+  // transaction, the initiating transaction ID is used.
+  //
+  // To ensure IDs are unique, we use sequence numbers for transaction IDs,
+  // which grow in opposite directions from child to parent.
+
+  friend class AutoEnterTransaction;
+  AutoEnterTransaction* mTransactionStack MOZ_GUARDED_BY(*mMonitor) = nullptr;
+
+  int32_t CurrentNestedInsideSyncTransaction() const MOZ_REQUIRES(*mMonitor);
+
+  bool AwaitingSyncReply() const MOZ_REQUIRES(*mMonitor);
+  int AwaitingSyncReplyNestedLevel() const MOZ_REQUIRES(*mMonitor);
+
+  bool DispatchingSyncMessage() const MOZ_REQUIRES(*mMonitor);
+  int DispatchingSyncMessageNestedLevel() const MOZ_REQUIRES(*mMonitor);
+
+#ifdef DEBUG
+  void AssertMaybeDeferredCountCorrect() MOZ_REQUIRES(*mMonitor);
+#else
+  void AssertMaybeDeferredCountCorrect() MOZ_REQUIRES(*mMonitor) {}
+#endif
+
+  // If a sync message times out, we store its sequence number here. Any
+  // future sync messages will fail immediately. Once the reply for original
+  // sync message is received, we allow sync messages again.
+  //
+  // When a message times out, nothing is done to inform the other side. The
+  // other side will eventually dispatch the message and send a reply. Our
+  // side is responsible for replying to all sync messages sent by the other
+  // side when it dispatches the timed out message. The response is always an
+  // error.
+  //
+  // A message is only timed out if it initiated a transaction. This avoids
+  // hitting a lot of corner cases with message nesting that we don't really
+  // care about.
+  int32_t mTimedOutMessageSeqno MOZ_GUARDED_BY(*mMonitor) = 0;
+  int mTimedOutMessageNestedLevel MOZ_GUARDED_BY(*mMonitor) = 0;
+
+  // Queue of all incoming messages.
+  //
+  // If both this side and the other side are functioning correctly, the other
+  // side can send as many async messages as it wants before sending us a
+  // blocking message.  After sending a blocking message, the other side must be
+  // blocked, and thus can't send us any more messages until we process the sync
+  // in-msg.
+  //
+  MessageQueue mPending MOZ_GUARDED_BY(*mMonitor);
+
+  // The number of messages in mPending for which IsAlwaysDeferred is false
+  // (i.e., the number of messages that might not be deferred, depending on
+  // context).
+  size_t mMaybeDeferredPendingCount MOZ_GUARDED_BY(*mMonitor) = 0;
+
+  // Is there currently MessageChannel logic for this channel on the C++ stack?
+  // This member is only accessed on the worker thread, and so is not protected
+  // by mMonitor.
+  bool mOnCxxStack = false;
+
+  // Map of async Callbacks that are still waiting replies.
+  CallbackMap mPendingResponses;
+
+#ifdef OS_WIN
+  HANDLE mEvent;
+#endif
+
+  // Should the channel abort the process from the I/O thread when
+  // a channel error occurs?
+  bool mAbortOnError MOZ_GUARDED_BY(*mMonitor) = false;
+
+  // True if the listener has already been notified of a channel close or
+  // error.
+  bool mNotifiedChannelDone MOZ_GUARDED_BY(*mMonitor) = false;
+
+  // See SetChannelFlags
+  ChannelFlags mFlags = REQUIRE_DEFAULT;
+
+  bool mBuildIDsConfirmedMatch MOZ_GUARDED_BY(*mMonitor) = false;
+
+  // If this is true, both ends of this message channel have event targets
+  // on the same thread.
+  bool mIsSameThreadChannel = false;
+};
+
+void CancelCPOWs();
+
+}  // namespace ipc
+}  // namespace mozilla
+
+namespace IPC {
+template <>
+struct ParamTraits<mozilla::ipc::ResponseRejectReason>
+    : public ContiguousEnumSerializer<
+          mozilla::ipc::ResponseRejectReason,
+          mozilla::ipc::ResponseRejectReason::SendError,
+          mozilla::ipc::ResponseRejectReason::EndGuard_> {};
+}  // namespace IPC
+
+namespace geckoprofiler::markers {
+
+struct IPCMarker {
+  static constexpr mozilla::Span<const char> MarkerTypeName() {
+    return mozilla::MakeStringSpan("IPC");
+  }
+  static void StreamJSONMarkerData(
+      mozilla::baseprofiler::SpliceableJSONWriter& aWriter,
+      mozilla::TimeStamp aStart, mozilla::TimeStamp aEnd, int32_t aOtherPid,
+      int32_t aMessageSeqno, IPC::Message::msgid_t aMessageType,
+      mozilla::ipc::Side aSide, mozilla::ipc::MessageDirection aDirection,
+      mozilla::ipc::MessagePhase aPhase, bool aSync,
+      mozilla::MarkerThreadId aOriginThreadId) {
+    using namespace mozilla::ipc;
+    // This payload still streams a startTime and endTime property because it
+    // made the migration to MarkerTiming on the front-end easier.
+    aWriter.TimeProperty("startTime", aStart);
+    aWriter.TimeProperty("endTime", aEnd);
+
+    aWriter.IntProperty("otherPid", aOtherPid);
+    aWriter.IntProperty("messageSeqno", aMessageSeqno);
+    aWriter.StringProperty(
+        "messageType",
+        mozilla::MakeStringSpan(IPC::StringFromIPCMessageType(aMessageType)));
+    aWriter.StringProperty("side", IPCSideToString(aSide));
+    aWriter.StringProperty("direction",
+                           aDirection == MessageDirection::eSending
+                               ? mozilla::MakeStringSpan("sending")
+                               : mozilla::MakeStringSpan("receiving"));
+    aWriter.StringProperty("phase", IPCPhaseToString(aPhase));
+    aWriter.BoolProperty("sync", aSync);
+    if (!aOriginThreadId.IsUnspecified()) {
+      // Tech note: If `ToNumber()` returns a uint64_t, the conversion to
+      // int64_t is "implementation-defined" before C++20. This is acceptable
+      // here, because this is a one-way conversion to a unique identifier
+      // that's used to visually separate data by thread on the front-end.
+      aWriter.IntProperty(
+          "threadId",
+          static_cast<int64_t>(aOriginThreadId.ThreadId().ToNumber()));
+    }
+  }
+  static mozilla::MarkerSchema MarkerTypeDisplay() {
+    return mozilla::MarkerSchema::SpecialFrontendLocation{};
+  }
+
+ private:
+  static mozilla::Span<const char> IPCSideToString(mozilla::ipc::Side aSide) {
+    switch (aSide) {
+      case mozilla::ipc::ParentSide:
+        return mozilla::MakeStringSpan("parent");
+      case mozilla::ipc::ChildSide:
+        return mozilla::MakeStringSpan("child");
+      case mozilla::ipc::UnknownSide:
+        return mozilla::MakeStringSpan("unknown");
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid IPC side");
+        return mozilla::MakeStringSpan("<invalid IPC side>");
+    }
+  }
+
+  static mozilla::Span<const char> IPCPhaseToString(
+      mozilla::ipc::MessagePhase aPhase) {
+    switch (aPhase) {
+      case mozilla::ipc::MessagePhase::Endpoint:
+        return mozilla::MakeStringSpan("endpoint");
+      case mozilla::ipc::MessagePhase::TransferStart:
+        return mozilla::MakeStringSpan("transferStart");
+      case mozilla::ipc::MessagePhase::TransferEnd:
+        return mozilla::MakeStringSpan("transferEnd");
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid IPC phase");
+        return mozilla::MakeStringSpan("<invalid IPC phase>");
+    }
+  }
+};
+
+}  // namespace geckoprofiler::markers
+
+#endif  // ifndef ipc_glue_MessageChannel_h
diff --git a/ipc/glue/MessageLink.cpp b/ipc/glue/MessageLink.cpp
new file mode 100644
index 0000000000..872ff48b27
--- /dev/null
+++ b/ipc/glue/MessageLink.cpp
@@ -0,0 +1,195 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=4 et :
+ */
+/* 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/ipc/MessageLink.h"
+#include "mojo/core/ports/event.h"
+#include "mojo/core/ports/node.h"
+#include "mozilla/ipc/MessageChannel.h"
+#include "mozilla/ipc/BrowserProcessSubThread.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/ipc/NodeController.h"
+#include "chrome/common/ipc_channel.h"
+#include "base/task.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+#include "nsDebug.h"
+#include "nsExceptionHandler.h"
+#include "nsISupportsImpl.h"
+#include "nsPrintfCString.h"
+#include "nsXULAppAPI.h"
+
+using namespace mozilla;
+
+namespace mozilla {
+namespace ipc {
+
+MessageLink::MessageLink(MessageChannel* aChan) : mChan(aChan) {}
+
+MessageLink::~MessageLink() {
+#ifdef DEBUG
+  mChan = nullptr;
+#endif
+}
+
+class PortLink::PortObserverThunk : public NodeController::PortObserver {
+ public:
+  PortObserverThunk(RefCountedMonitor* aMonitor, PortLink* aLink)
+      : mMonitor(aMonitor), mLink(aLink) {}
+
+  void OnPortStatusChanged() override {
+    MonitorAutoLock lock(*mMonitor);
+    if (mLink) {
+      mLink->OnPortStatusChanged();
+    }
+  }
+
+ private:
+  friend class PortLink;
+
+  // The monitor from our PortLink's MessageChannel. Guards access to `mLink`.
+  RefPtr<RefCountedMonitor> mMonitor;
+
+  // Cleared by `PortLink` in `PortLink::Clear()`.
+  PortLink* MOZ_NON_OWNING_REF mLink;
+};
+
+PortLink::PortLink(MessageChannel* aChan, ScopedPort aPort)
+    : MessageLink(aChan), mNode(aPort.Controller()), mPort(aPort.Release()) {
+  mChan->mMonitor->AssertCurrentThreadOwns();
+
+  mObserver = new PortObserverThunk(mChan->mMonitor, this);
+  mNode->SetPortObserver(mPort, mObserver);
+
+  // Dispatch an event to the IO loop to trigger an initial
+  // `OnPortStatusChanged` to deliver any pending messages. This needs to be run
+  // asynchronously from a different thread (or in the case of a same-thread
+  // channel, from the current thread), for now due to assertions in
+  // `MessageChannel`.
+  nsCOMPtr<nsIRunnable> openRunnable = NewRunnableMethod(
+      "PortLink::Open", mObserver, &PortObserverThunk::OnPortStatusChanged);
+  if (aChan->mIsSameThreadChannel) {
+    aChan->mWorkerThread->Dispatch(openRunnable.forget());
+  } else {
+    XRE_GetIOMessageLoop()->PostTask(openRunnable.forget());
+  }
+}
+
+PortLink::~PortLink() {
+  MOZ_RELEASE_ASSERT(!mObserver, "PortLink destroyed without being closed!");
+}
+
+void PortLink::SendMessage(UniquePtr<Message> aMessage) {
+  mChan->mMonitor->AssertCurrentThreadOwns();
+
+  if (aMessage->size() > IPC::Channel::kMaximumMessageSize) {
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCMessageName,
+        nsDependentCString(aMessage->name()));
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCMessageSize,
+        static_cast<unsigned int>(aMessage->size()));
+    MOZ_CRASH("IPC message size is too large");
+  }
+  aMessage->AssertAsLargeAsHeader();
+
+  RefPtr<PortObserverThunk> observer = mObserver;
+  if (!observer) {
+    NS_WARNING("Ignoring message to closed PortLink");
+    return;
+  }
+
+  // Make local copies of relevant member variables, so we can unlock the
+  // monitor for the rest of this function. This protects us in case `this` is
+  // deleted during the call (although that shouldn't happen in practice).
+  //
+  // We don't want the monitor to be held when calling into ports, as we may be
+  // re-entrantly called by our `PortObserverThunk` which will attempt to
+  // acquire the monitor.
+  RefPtr<RefCountedMonitor> monitor = mChan->mMonitor;
+  RefPtr<NodeController> node = mNode;
+  PortRef port = mPort;
+
+  bool ok = false;
+  monitor->AssertCurrentThreadOwns();
+  {
+    MonitorAutoUnlock guard(*monitor);
+    ok = node->SendUserMessage(port, std::move(aMessage));
+  }
+  if (!ok) {
+    // The send failed, but double-check that we weren't closed racily while
+    // sending, which could lead to an invalid state error.
+    if (observer->mLink) {
+      MOZ_CRASH("Invalid argument to SendUserMessage");
+    }
+    NS_WARNING("Message dropped as PortLink was closed");
+  }
+}
+
+void PortLink::Close() {
+  mChan->mMonitor->AssertCurrentThreadOwns();
+
+  if (!mObserver) {
+    // We're already being closed.
+    return;
+  }
+
+  Clear();
+}
+
+void PortLink::Clear() {
+  mChan->mMonitor->AssertCurrentThreadOwns();
+
+  // NOTE: We're calling into `ports` with our monitor held! Usually, this could
+  // lead to deadlocks due to the PortObserverThunk acquiring the lock
+  // re-entrantly, but is OK here as we're immediately clearing the port's
+  // observer. We shouldn't have issues with any re-entrant calls on this thread
+  // acquiring this MessageChannel's monitor.
+  //
+  // We also clear out the reference in `mObserver` back to this type so that
+  // notifications from other threads won't try to call us again once we release
+  // the monitor.
+  mNode->SetPortObserver(mPort, nullptr);
+  mObserver->mLink = nullptr;
+  mObserver = nullptr;
+  mNode->ClosePort(mPort);
+}
+
+void PortLink::OnPortStatusChanged() {
+  mChan->mMonitor->AssertCurrentThreadOwns();
+
+  // Check if the port's remoteness status has updated, and tell our channel if
+  // it has.
+  if (Maybe<PortStatus> status = mNode->GetStatus(mPort);
+      status && status->peer_remote != mChan->IsCrossProcess()) {
+    mChan->SetIsCrossProcess(status->peer_remote);
+  }
+
+  while (mObserver) {
+    UniquePtr<IPC::Message> message;
+    if (!mNode->GetMessage(mPort, &message)) {
+      Clear();
+      mChan->OnChannelErrorFromLink();
+      return;
+    }
+    if (!message) {
+      return;
+    }
+
+    mChan->OnMessageReceivedFromLink(std::move(message));
+  }
+}
+
+bool PortLink::IsClosed() const {
+  if (Maybe<PortStatus> status = mNode->GetStatus(mPort)) {
+    return !(status->has_messages || status->receiving_messages);
+  }
+  return true;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/MessageLink.h b/ipc/glue/MessageLink.h
new file mode 100644
index 0000000000..854dc6e2f1
--- /dev/null
+++ b/ipc/glue/MessageLink.h
@@ -0,0 +1,112 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=4 et :
+ */
+/* 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 ipc_glue_MessageLink_h
+#define ipc_glue_MessageLink_h 1
+
+#include <cstdint>
+#include "base/message_loop.h"
+#include "mojo/core/ports/node.h"
+#include "mojo/core/ports/port_ref.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/ipc/ScopedPort.h"
+
+namespace IPC {
+class Message;
+class MessageReader;
+class MessageWriter;
+}  // namespace IPC
+
+namespace mozilla {
+namespace ipc {
+
+class MessageChannel;
+class NodeController;
+
+struct HasResultCodes {
+  enum Result {
+    MsgProcessed,
+    MsgDropped,
+    MsgNotKnown,
+    MsgNotAllowed,
+    MsgPayloadError,
+    MsgProcessingError,
+    MsgRouteError,
+    MsgValueError
+  };
+};
+
+enum Side : uint8_t { ParentSide, ChildSide, UnknownSide };
+
+class MessageLink {
+ public:
+  typedef IPC::Message Message;
+
+  explicit MessageLink(MessageChannel* aChan);
+  virtual ~MessageLink();
+
+  // n.b.: These methods all require that the channel monitor is
+  // held when they are invoked.
+  virtual void SendMessage(mozilla::UniquePtr<Message> msg) = 0;
+
+  // Synchronously close the connection, such that no further notifications will
+  // be delivered to the MessageChannel instance. Must be called with the
+  // channel monitor held.
+  virtual void Close() = 0;
+
+  virtual bool IsClosed() const = 0;
+
+#ifdef FUZZING_SNAPSHOT
+  virtual Maybe<mojo::core::ports::PortName> GetPortName() { return Nothing(); }
+#endif
+
+ protected:
+  MessageChannel* mChan;
+};
+
+class PortLink final : public MessageLink {
+  using PortRef = mojo::core::ports::PortRef;
+  using PortStatus = mojo::core::ports::PortStatus;
+  using UserMessage = mojo::core::ports::UserMessage;
+  using UserMessageEvent = mojo::core::ports::UserMessageEvent;
+
+ public:
+  PortLink(MessageChannel* aChan, ScopedPort aPort);
+  virtual ~PortLink();
+
+  void SendMessage(UniquePtr<Message> aMessage) override;
+  void Close() override;
+
+  bool IsClosed() const override;
+
+#ifdef FUZZING_SNAPSHOT
+  Maybe<mojo::core::ports::PortName> GetPortName() override {
+    return Some(mPort.name());
+  }
+#endif
+
+ private:
+  class PortObserverThunk;
+  friend class PortObserverThunk;
+
+  void OnPortStatusChanged();
+
+  // Called either when an error is detected on the port from the port observer,
+  // or when `SendClose()` is called.
+  void Clear();
+
+  const RefPtr<NodeController> mNode;
+  const PortRef mPort;
+
+  RefPtr<PortObserverThunk> mObserver;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef ipc_glue_MessageLink_h
diff --git a/ipc/glue/MessagePump.cpp b/ipc/glue/MessagePump.cpp
new file mode 100644
index 0000000000..50c916608c
--- /dev/null
+++ b/ipc/glue/MessagePump.cpp
@@ -0,0 +1,336 @@
+/* -*- 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 "MessagePump.h"
+
+#include "nsIThread.h"
+#include "nsITimer.h"
+#include "nsICancelableRunnable.h"
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/scoped_nsautorelease_pool.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+#include "nsComponentManagerUtils.h"
+#include "nsDebug.h"
+#include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "nsTimerImpl.h"
+#include "nsXULAppAPI.h"
+#include "prthread.h"
+
+using base::TimeTicks;
+using namespace mozilla::ipc;
+
+#ifdef DEBUG
+static MessagePump::Delegate* gFirstDelegate;
+#endif
+
+namespace mozilla {
+namespace ipc {
+
+class DoWorkRunnable final : public CancelableRunnable,
+                             public nsITimerCallback {
+ public:
+  explicit DoWorkRunnable(MessagePump* aPump)
+      : CancelableRunnable("ipc::DoWorkRunnable"), mPump(aPump) {
+    MOZ_ASSERT(aPump);
+  }
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIRUNNABLE
+  NS_DECL_NSITIMERCALLBACK
+  nsresult Cancel() override;
+
+ private:
+  ~DoWorkRunnable() = default;
+
+  MessagePump* mPump;
+  // DoWorkRunnable is designed as a stateless singleton.  Do not add stateful
+  // members here!
+};
+
+} /* namespace ipc */
+} /* namespace mozilla */
+
+MessagePump::MessagePump(nsISerialEventTarget* aEventTarget)
+    : mEventTarget(aEventTarget) {
+  mDoWorkEvent = new DoWorkRunnable(this);
+}
+
+MessagePump::~MessagePump() = default;
+
+void MessagePump::Run(MessagePump::Delegate* aDelegate) {
+  MOZ_ASSERT(keep_running_);
+  MOZ_RELEASE_ASSERT(NS_IsMainThread(),
+                     "Use mozilla::ipc::MessagePumpForNonMainThreads instead!");
+  MOZ_RELEASE_ASSERT(!mEventTarget);
+
+  nsIThread* thisThread = NS_GetCurrentThread();
+  MOZ_ASSERT(thisThread);
+
+  mDelayedWorkTimer = NS_NewTimer();
+  MOZ_ASSERT(mDelayedWorkTimer);
+
+  base::ScopedNSAutoreleasePool autoReleasePool;
+
+  for (;;) {
+    autoReleasePool.Recycle();
+
+    bool did_work = NS_ProcessNextEvent(thisThread, false) ? true : false;
+    if (!keep_running_) break;
+
+    // NB: it is crucial *not* to directly call |aDelegate->DoWork()|
+    // here.  To ensure that MessageLoop tasks and XPCOM events have
+    // equal priority, we sensitively rely on processing exactly one
+    // Task per DoWorkRunnable XPCOM event.
+
+    did_work |= aDelegate->DoDelayedWork(&delayed_work_time_);
+
+    if (did_work && delayed_work_time_.is_null()) mDelayedWorkTimer->Cancel();
+
+    if (!keep_running_) break;
+
+    if (did_work) continue;
+
+    did_work = aDelegate->DoIdleWork();
+    if (!keep_running_) break;
+
+    if (did_work) continue;
+
+    // This will either sleep or process an event.
+    NS_ProcessNextEvent(thisThread, true);
+  }
+
+  mDelayedWorkTimer->Cancel();
+
+  keep_running_ = true;
+}
+
+void MessagePump::ScheduleWork() {
+  // Make sure the event loop wakes up.
+  if (mEventTarget) {
+    mEventTarget->Dispatch(mDoWorkEvent, NS_DISPATCH_NORMAL);
+  } else {
+    // Some things (like xpcshell) don't use the app shell and so Run hasn't
+    // been called. We still need to wake up the main thread.
+    NS_DispatchToMainThread(mDoWorkEvent);
+  }
+  event_.Signal();
+}
+
+void MessagePump::ScheduleWorkForNestedLoop() {
+  // This method is called when our MessageLoop has just allowed
+  // nested tasks.  In our setup, whenever that happens we know that
+  // DoWork() will be called "soon", so there's no need to pay the
+  // cost of what will be a no-op nsThread::Dispatch(mDoWorkEvent).
+}
+
+void MessagePump::ScheduleDelayedWork(const base::TimeTicks& aDelayedTime) {
+  // To avoid racing on mDelayedWorkTimer, we need to be on the same thread as
+  // ::Run().
+  MOZ_RELEASE_ASSERT((!mEventTarget && NS_IsMainThread()) ||
+                     mEventTarget->IsOnCurrentThread());
+
+  if (!mDelayedWorkTimer) {
+    mDelayedWorkTimer = NS_NewTimer();
+    if (!mDelayedWorkTimer) {
+      // Called before XPCOM has started up? We can't do this correctly.
+      NS_WARNING("Delayed task might not run!");
+      delayed_work_time_ = aDelayedTime;
+      return;
+    }
+  }
+
+  if (!delayed_work_time_.is_null()) {
+    mDelayedWorkTimer->Cancel();
+  }
+
+  delayed_work_time_ = aDelayedTime;
+
+  // TimeDelta's constructor initializes to 0
+  base::TimeDelta delay;
+  if (aDelayedTime > base::TimeTicks::Now())
+    delay = aDelayedTime - base::TimeTicks::Now();
+
+  uint32_t delayMS = uint32_t(delay.InMilliseconds());
+  mDelayedWorkTimer->InitWithCallback(mDoWorkEvent, delayMS,
+                                      nsITimer::TYPE_ONE_SHOT);
+}
+
+nsISerialEventTarget* MessagePump::GetXPCOMThread() {
+  if (mEventTarget) {
+    return mEventTarget;
+  }
+
+  // Main thread
+  return GetMainThreadSerialEventTarget();
+}
+
+void MessagePump::DoDelayedWork(base::MessagePump::Delegate* aDelegate) {
+  aDelegate->DoDelayedWork(&delayed_work_time_);
+  if (!delayed_work_time_.is_null()) {
+    ScheduleDelayedWork(delayed_work_time_);
+  }
+}
+
+NS_IMPL_ISUPPORTS_INHERITED(DoWorkRunnable, CancelableRunnable,
+                            nsITimerCallback)
+
+NS_IMETHODIMP
+DoWorkRunnable::Run() {
+  MessageLoop* loop = MessageLoop::current();
+  MOZ_ASSERT(loop);
+
+  bool nestableTasksAllowed = loop->NestableTasksAllowed();
+
+  // MessageLoop::RunTask() disallows nesting, but our Frankenventloop will
+  // always dispatch DoWork() below from what looks to MessageLoop like a nested
+  // context.  So we unconditionally allow nesting here.
+  loop->SetNestableTasksAllowed(true);
+  loop->DoWork();
+  loop->SetNestableTasksAllowed(nestableTasksAllowed);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DoWorkRunnable::Notify(nsITimer* aTimer) {
+  MessageLoop* loop = MessageLoop::current();
+  MOZ_ASSERT(loop);
+
+  bool nestableTasksAllowed = loop->NestableTasksAllowed();
+  loop->SetNestableTasksAllowed(true);
+  mPump->DoDelayedWork(loop);
+  loop->SetNestableTasksAllowed(nestableTasksAllowed);
+
+  return NS_OK;
+}
+
+nsresult DoWorkRunnable::Cancel() {
+  // Workers require cancelable runnables, but we can't really cancel cleanly
+  // here.  If we don't process this runnable then we will leave something
+  // unprocessed in the message_loop.  Therefore, eagerly complete our work
+  // instead by immediately calling Run().  Run() should be called separately
+  // after this.  Unfortunately we cannot use flags to verify this because
+  // DoWorkRunnable is a stateless singleton that can be in the event queue
+  // multiple times simultaneously.
+  MOZ_ALWAYS_SUCCEEDS(Run());
+  return NS_OK;
+}
+
+void MessagePumpForChildProcess::Run(base::MessagePump::Delegate* aDelegate) {
+  if (mFirstRun) {
+    MOZ_ASSERT(aDelegate && !gFirstDelegate);
+#ifdef DEBUG
+    gFirstDelegate = aDelegate;
+#endif
+
+    mFirstRun = false;
+    if (NS_FAILED(XRE_RunAppShell())) {
+      NS_WARNING("Failed to run app shell?!");
+    }
+
+    MOZ_ASSERT(aDelegate && aDelegate == gFirstDelegate);
+#ifdef DEBUG
+    gFirstDelegate = nullptr;
+#endif
+
+    return;
+  }
+
+  MOZ_ASSERT(aDelegate && aDelegate == gFirstDelegate);
+
+  // We can get to this point in startup with Tasks in our loop's
+  // incoming_queue_ or pending_queue_, but without a matching
+  // DoWorkRunnable().  In MessagePump::Run() above, we sensitively
+  // depend on *not* directly calling delegate->DoWork(), because that
+  // prioritizes Tasks above XPCOM events.  However, from this point
+  // forward, any Task posted to our loop is guaranteed to have a
+  // DoWorkRunnable enqueued for it.
+  //
+  // So we just flush the pending work here and move on.
+  MessageLoop* loop = MessageLoop::current();
+  bool nestableTasksAllowed = loop->NestableTasksAllowed();
+  loop->SetNestableTasksAllowed(true);
+
+  while (aDelegate->DoWork())
+    ;
+
+  loop->SetNestableTasksAllowed(nestableTasksAllowed);
+
+  // Really run.
+  mozilla::ipc::MessagePump::Run(aDelegate);
+}
+
+void MessagePumpForNonMainThreads::Run(base::MessagePump::Delegate* aDelegate) {
+  MOZ_ASSERT(keep_running_);
+  MOZ_RELEASE_ASSERT(!NS_IsMainThread(),
+                     "Use mozilla::ipc::MessagePump instead!");
+
+  nsIThread* thread = NS_GetCurrentThread();
+  MOZ_RELEASE_ASSERT(mEventTarget->IsOnCurrentThread());
+
+  mDelayedWorkTimer = NS_NewTimer(mEventTarget);
+  MOZ_ASSERT(mDelayedWorkTimer);
+
+  // Chromium event notifications to be processed will be received by this
+  // event loop as a DoWorkRunnables via ScheduleWork. Chromium events that
+  // were received before our thread is valid, however, will not generate
+  // runnable wrappers. We must process any of these before we enter this
+  // loop, or we will forever have unprocessed chromium messages in our queue.
+  //
+  // Note we would like to request a flush of the chromium event queue
+  // using a runnable on the xpcom side, but some thread implementations
+  // (dom workers) get cranky if we call ScheduleWork here (ScheduleWork
+  // calls dispatch on mEventTarget) before the thread processes an event. As
+  // such, clear the queue manually.
+  while (aDelegate->DoWork()) {
+  }
+
+  base::ScopedNSAutoreleasePool autoReleasePool;
+  for (;;) {
+    autoReleasePool.Recycle();
+
+    bool didWork = NS_ProcessNextEvent(thread, false) ? true : false;
+    if (!keep_running_) {
+      break;
+    }
+
+    didWork |= aDelegate->DoDelayedWork(&delayed_work_time_);
+
+    if (didWork && delayed_work_time_.is_null()) {
+      mDelayedWorkTimer->Cancel();
+    }
+
+    if (!keep_running_) {
+      break;
+    }
+
+    if (didWork) {
+      continue;
+    }
+
+    DebugOnly<bool> didIdleWork = aDelegate->DoIdleWork();
+    MOZ_ASSERT(!didIdleWork);
+    if (!keep_running_) {
+      break;
+    }
+
+    if (didWork) {
+      continue;
+    }
+
+    // This will either sleep or process an event.
+    NS_ProcessNextEvent(thread, true);
+  }
+
+  mDelayedWorkTimer->Cancel();
+
+  keep_running_ = true;
+}
diff --git a/ipc/glue/MessagePump.h b/ipc/glue/MessagePump.h
new file mode 100644
index 0000000000..50b97efd79
--- /dev/null
+++ b/ipc/glue/MessagePump.h
@@ -0,0 +1,203 @@
+/* -*- 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 __IPC_GLUE_MESSAGEPUMP_H__
+#define __IPC_GLUE_MESSAGEPUMP_H__
+
+#include "base/message_pump_default.h"
+#if defined(XP_WIN)
+#  include "base/message_pump_win.h"
+#elif defined(XP_DARWIN)
+#  include "base/message_pump_mac.h"
+#endif
+
+#include "base/time.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Mutex.h"
+#include "nsCOMPtr.h"
+#include "nsIThreadInternal.h"
+
+class nsIEventTarget;
+class nsITimer;
+
+namespace mozilla {
+namespace ipc {
+
+class DoWorkRunnable;
+
+class MessagePump : public base::MessagePumpDefault {
+  friend class DoWorkRunnable;
+
+ public:
+  explicit MessagePump(nsISerialEventTarget* aEventTarget);
+
+  // From base::MessagePump.
+  virtual void Run(base::MessagePump::Delegate* aDelegate) override;
+
+  // From base::MessagePump.
+  virtual void ScheduleWork() override;
+
+  // From base::MessagePump.
+  virtual void ScheduleWorkForNestedLoop() override;
+
+  // From base::MessagePump.
+  virtual void ScheduleDelayedWork(
+      const base::TimeTicks& aDelayedWorkTime) override;
+
+  virtual nsISerialEventTarget* GetXPCOMThread() override;
+
+ protected:
+  virtual ~MessagePump();
+
+ private:
+  // Only called by DoWorkRunnable.
+  void DoDelayedWork(base::MessagePump::Delegate* aDelegate);
+
+ protected:
+  nsISerialEventTarget* mEventTarget;
+
+  // mDelayedWorkTimer and mEventTarget are set in Run() by this class or its
+  // subclasses.
+  nsCOMPtr<nsITimer> mDelayedWorkTimer;
+
+ private:
+  // Only accessed by this class.
+  RefPtr<DoWorkRunnable> mDoWorkEvent;
+};
+
+class MessagePumpForChildProcess final : public MessagePump {
+ public:
+  MessagePumpForChildProcess() : MessagePump(nullptr), mFirstRun(true) {}
+
+  virtual void Run(base::MessagePump::Delegate* aDelegate) override;
+
+ private:
+  ~MessagePumpForChildProcess() = default;
+
+  bool mFirstRun;
+};
+
+class MessagePumpForNonMainThreads final : public MessagePump {
+ public:
+  explicit MessagePumpForNonMainThreads(nsISerialEventTarget* aEventTarget)
+      : MessagePump(aEventTarget) {}
+
+  virtual void Run(base::MessagePump::Delegate* aDelegate) override;
+
+ private:
+  ~MessagePumpForNonMainThreads() = default;
+};
+
+#if defined(XP_WIN)
+// Extends the TYPE_UI message pump to process xpcom events.
+class MessagePumpForNonMainUIThreads final : public base::MessagePumpForUI,
+                                             public nsIThreadObserver {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSITHREADOBSERVER
+
+ public:
+  explicit MessagePumpForNonMainUIThreads(nsISerialEventTarget* aEventTarget)
+      : mInWait(false), mWaitLock("mInWait") {}
+
+  // The main run loop for this thread.
+  virtual void DoRunLoop() override;
+
+  virtual nsISerialEventTarget* GetXPCOMThread() override {
+    return nullptr;  // not sure what to do with this one
+  }
+
+ protected:
+  void SetInWait() {
+    MutexAutoLock lock(mWaitLock);
+    mInWait = true;
+  }
+
+  void ClearInWait() {
+    MutexAutoLock lock(mWaitLock);
+    mInWait = false;
+  }
+
+  bool GetInWait() {
+    MutexAutoLock lock(mWaitLock);
+    return mInWait;
+  }
+
+ private:
+  ~MessagePumpForNonMainUIThreads() {}
+
+  bool mInWait MOZ_GUARDED_BY(mWaitLock);
+  mozilla::Mutex mWaitLock;
+};
+#elif defined(XP_DARWIN)
+// Extends the CFRunLoopBase message pump to process xpcom events. Based on
+// MessagePumpNSRunLoop.
+class MessagePumpForNonMainUIThreads final
+    : public base::MessagePumpCFRunLoopBase,
+      public nsIThreadObserver {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSITHREADOBSERVER
+
+ public:
+  explicit MessagePumpForNonMainUIThreads(nsISerialEventTarget* aEventTarget);
+
+  void DoRun(base::MessagePump::Delegate* aDelegate) override;
+  void Quit() override;
+
+  nsISerialEventTarget* GetXPCOMThread() override { return mEventTarget; }
+
+ private:
+  ~MessagePumpForNonMainUIThreads();
+
+  nsISerialEventTarget* mEventTarget;
+
+  // A source that doesn't do anything but provide something signalable
+  // attached to the run loop.  This source will be signalled when Quit
+  // is called, to cause the loop to wake up so that it can stop.
+  CFRunLoopSourceRef quit_source_;
+
+  // False after Quit is called.
+  bool keep_running_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessagePumpForNonMainUIThreads);
+};
+#endif  // defined(XP_DARWIN)
+
+#if defined(MOZ_WIDGET_ANDROID)
+/*`
+ * The MessagePumpForAndroidUI exists to enable IPDL in the Android UI thread.
+ * The Android UI thread event loop is controlled by Android. This prevents
+ * running an existing MessagePump implementation in the Android UI thread. In
+ * order to enable IPDL on the Android UI thread it is necessary to have a
+ * non-looping MessagePump. This class enables forwarding of nsIRunnables from
+ * MessageLoop::PostTask_Helper to the registered nsIEventTarget with out the
+ * need to control the event loop. The only member function that should be
+ * invoked is GetXPCOMThread. All other member functions will invoke MOZ_CRASH
+ */
+class MessagePumpForAndroidUI : public base::MessagePump {
+ public:
+  explicit MessagePumpForAndroidUI(nsISerialEventTarget* aEventTarget)
+      : mEventTarget(aEventTarget) {}
+
+  virtual void Run(Delegate* delegate);
+  virtual void Quit();
+  virtual void ScheduleWork();
+  virtual void ScheduleDelayedWork(const base::TimeTicks& delayed_work_time);
+  virtual nsISerialEventTarget* GetXPCOMThread() { return mEventTarget; }
+
+ private:
+  ~MessagePumpForAndroidUI() {}
+  MessagePumpForAndroidUI() {}
+
+  nsISerialEventTarget* mEventTarget;
+};
+#endif  // defined(MOZ_WIDGET_ANDROID)
+
+} /* namespace ipc */
+} /* namespace mozilla */
+
+#endif /* __IPC_GLUE_MESSAGEPUMP_H__ */
diff --git a/ipc/glue/MessagePump_android.cpp b/ipc/glue/MessagePump_android.cpp
new file mode 100644
index 0000000000..0288041ad3
--- /dev/null
+++ b/ipc/glue/MessagePump_android.cpp
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MessagePump.h"
+
+namespace mozilla::ipc {
+void MessagePumpForAndroidUI::Run(Delegate* delegate) {
+  MOZ_CRASH("MessagePumpForAndroidUI should never be Run.");
+}
+
+void MessagePumpForAndroidUI::Quit() {
+  MOZ_CRASH("MessagePumpForAndroidUI should never be Quit.");
+}
+
+void MessagePumpForAndroidUI::ScheduleWork() {
+  MOZ_CRASH("MessagePumpForAndroidUI should never ScheduleWork");
+}
+
+void MessagePumpForAndroidUI::ScheduleDelayedWork(
+    const TimeTicks& delayed_work_time) {
+  MOZ_CRASH("MessagePumpForAndroidUI should never ScheduleDelayedWork");
+}
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/MessagePump_mac.mm b/ipc/glue/MessagePump_mac.mm
new file mode 100644
index 0000000000..2af0e07203
--- /dev/null
+++ b/ipc/glue/MessagePump_mac.mm
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=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 "MessagePump.h"
+
+#include <Foundation/Foundation.h>
+
+#include "base/scoped_nsautorelease_pool.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "nsISupportsImpl.h"
+
+using namespace mozilla::ipc;
+
+static void NoOp(void* info) {}
+
+NS_IMPL_ADDREF_INHERITED(MessagePumpForNonMainUIThreads, MessagePump)
+NS_IMPL_RELEASE_INHERITED(MessagePumpForNonMainUIThreads, MessagePump)
+NS_IMPL_QUERY_INTERFACE(MessagePumpForNonMainUIThreads, nsIThreadObserver)
+
+MessagePumpForNonMainUIThreads::MessagePumpForNonMainUIThreads(nsISerialEventTarget* aEventTarget)
+    : mEventTarget(aEventTarget), keep_running_(true) {
+  MOZ_ASSERT(mEventTarget);
+  CFRunLoopSourceContext source_context = CFRunLoopSourceContext();
+  source_context.perform = NoOp;
+  quit_source_ = CFRunLoopSourceCreate(nullptr,  // allocator
+                                       0,        // priority
+                                       &source_context);
+  CFRunLoopAddSource(run_loop(), quit_source_, kCFRunLoopCommonModes);
+}
+
+MessagePumpForNonMainUIThreads::~MessagePumpForNonMainUIThreads() {
+  CFRunLoopRemoveSource(run_loop(), quit_source_, kCFRunLoopCommonModes);
+  CFRelease(quit_source_);
+}
+
+void MessagePumpForNonMainUIThreads::DoRun(base::MessagePump::Delegate* aDelegate) {
+  // If this is a chromium thread and no nsThread is associated with it, this call will create a
+  // new nsThread.
+  nsIThread* thread = NS_GetCurrentThread();
+  MOZ_ASSERT(thread);
+
+  // Set the main thread observer so we can wake up when xpcom events need to get processed.
+  nsCOMPtr<nsIThreadInternal> ti(do_QueryInterface(thread));
+  MOZ_ASSERT(ti);
+  ti->SetObserver(this);
+
+  base::ScopedNSAutoreleasePool autoReleasePool;
+
+  while (keep_running_) {
+    // Drain the xpcom event loop first.
+    if (NS_ProcessNextEvent(nullptr, false)) {
+      continue;
+    }
+
+    autoReleasePool.Recycle();
+
+    if (!keep_running_) {
+      break;
+    }
+
+    // Now process the CFRunLoop. It exits after running once.
+    // NSRunLoop manages autorelease pools itself.
+    [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
+  }
+
+  ti->SetObserver(nullptr);
+  keep_running_ = true;
+}
+
+void MessagePumpForNonMainUIThreads::Quit() {
+  keep_running_ = false;
+  CFRunLoopSourceSignal(quit_source_);
+  CFRunLoopWakeUp(run_loop());
+}
+
+NS_IMETHODIMP MessagePumpForNonMainUIThreads::OnDispatchedEvent() {
+  // ScheduleWork will signal an input source to the run loop, making it exit so it can process the
+  // xpcom event.
+  ScheduleWork();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MessagePumpForNonMainUIThreads::OnProcessNextEvent(nsIThreadInternal* thread, bool mayWait) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MessagePumpForNonMainUIThreads::AfterProcessNextEvent(nsIThreadInternal* thread,
+                                                      bool eventWasProcessed) {
+  return NS_OK;
+}
diff --git a/ipc/glue/MessagePump_windows.cpp b/ipc/glue/MessagePump_windows.cpp
new file mode 100644
index 0000000000..c0109f3f43
--- /dev/null
+++ b/ipc/glue/MessagePump_windows.cpp
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=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 "MessagePump.h"
+
+using namespace mozilla::ipc;
+
+NS_IMPL_ADDREF_INHERITED(MessagePumpForNonMainUIThreads, MessagePump)
+NS_IMPL_RELEASE_INHERITED(MessagePumpForNonMainUIThreads, MessagePump)
+NS_IMPL_QUERY_INTERFACE(MessagePumpForNonMainUIThreads, nsIThreadObserver)
+
+#define CHECK_QUIT_STATE       \
+  {                            \
+    if (state_->should_quit) { \
+      break;                   \
+    }                          \
+  }
+
+void MessagePumpForNonMainUIThreads::DoRunLoop() {
+  MOZ_RELEASE_ASSERT(!NS_IsMainThread(),
+                     "Use mozilla::ipc::MessagePump instead!");
+
+  // If this is a chromium thread and no nsThread is associated
+  // with it, this call will create a new nsThread.
+  nsIThread* thread = NS_GetCurrentThread();
+  MOZ_ASSERT(thread);
+
+  // Set the main thread observer so we can wake up when
+  // xpcom events need to get processed.
+  nsCOMPtr<nsIThreadInternal> ti(do_QueryInterface(thread));
+  MOZ_ASSERT(ti);
+  ti->SetObserver(this);
+
+  for (;;) {
+    bool didWork = NS_ProcessNextEvent(thread, false);
+
+    didWork |= ProcessNextWindowsMessage();
+    CHECK_QUIT_STATE
+
+    didWork |= state_->delegate->DoWork();
+    CHECK_QUIT_STATE
+
+    didWork |= state_->delegate->DoDelayedWork(&delayed_work_time_);
+    if (didWork && delayed_work_time_.is_null()) {
+      KillTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this));
+    }
+    CHECK_QUIT_STATE
+
+    if (didWork) {
+      continue;
+    }
+
+    DebugOnly<bool> didIdleWork = state_->delegate->DoIdleWork();
+    MOZ_ASSERT(!didIdleWork);
+    CHECK_QUIT_STATE
+
+    SetInWait();
+    bool hasWork = NS_HasPendingEvents(thread);
+    if (didWork || hasWork) {
+      ClearInWait();
+      continue;
+    }
+    WaitForWork();  // Calls MsgWaitForMultipleObjectsEx(QS_ALLINPUT)
+    ClearInWait();
+  }
+
+  ClearInWait();
+
+  ti->SetObserver(nullptr);
+}
+
+NS_IMETHODIMP
+MessagePumpForNonMainUIThreads::OnDispatchedEvent() {
+  // If our thread is sleeping in DoRunLoop's call to WaitForWork() and an
+  // event posts to the nsIThread event queue - break our thread out of
+  // chromium's WaitForWork.
+  if (GetInWait()) {
+    ScheduleWork();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MessagePumpForNonMainUIThreads::OnProcessNextEvent(nsIThreadInternal* thread,
+                                                   bool mayWait) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MessagePumpForNonMainUIThreads::AfterProcessNextEvent(nsIThreadInternal* thread,
+                                                      bool eventWasProcessed) {
+  return NS_OK;
+}
diff --git a/ipc/glue/MiniTransceiver.cpp b/ipc/glue/MiniTransceiver.cpp
new file mode 100644
index 0000000000..933a727f62
--- /dev/null
+++ b/ipc/glue/MiniTransceiver.cpp
@@ -0,0 +1,251 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 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/ipc/MiniTransceiver.h"
+#include "chrome/common/ipc_message.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "base/eintr_wrapper.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/ScopeExit.h"
+#include "nsDebug.h"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <string.h>
+#include <errno.h>
+
+namespace mozilla::ipc {
+
+static const size_t kMaxIOVecSize = 64;
+static const size_t kMaxDataSize = 8 * 1024;
+static const size_t kMaxNumFds = 16;
+
+MiniTransceiver::MiniTransceiver(int aFd, DataBufferClear aDataBufClear)
+    : mFd(aFd),
+#ifdef DEBUG
+      mState(STATE_NONE),
+#endif
+      mDataBufClear(aDataBufClear) {
+}
+
+namespace {
+
+/**
+ * Initialize the IO vector for sending data and the control buffer for sending
+ * FDs.
+ */
+static void InitMsgHdr(msghdr* aHdr, int aIOVSize, size_t aMaxNumFds) {
+  aHdr->msg_name = nullptr;
+  aHdr->msg_namelen = 0;
+  aHdr->msg_flags = 0;
+
+  // Prepare the IO vector to receive the content of message.
+  auto* iov = new iovec[aIOVSize];
+  aHdr->msg_iov = iov;
+  aHdr->msg_iovlen = aIOVSize;
+
+  // Prepare the control buffer to receive file descriptors.
+  auto* cbuf = new char[CMSG_SPACE(sizeof(int) * aMaxNumFds)];
+  aHdr->msg_control = cbuf;
+  aHdr->msg_controllen = CMSG_SPACE(sizeof(int) * aMaxNumFds);
+}
+
+/**
+ * Delete resources allocated by InitMsgHdr().
+ */
+static void DeinitMsgHdr(msghdr* aHdr) {
+  delete aHdr->msg_iov;
+  delete static_cast<char*>(aHdr->msg_control);
+}
+
+}  // namespace
+
+void MiniTransceiver::PrepareFDs(msghdr* aHdr, IPC::Message& aMsg) {
+  // Set control buffer to send file descriptors of the Message.
+  size_t num_fds = aMsg.attached_handles_.Length();
+
+  cmsghdr* cmsg = CMSG_FIRSTHDR(aHdr);
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_RIGHTS;
+  cmsg->cmsg_len = CMSG_LEN(sizeof(int) * num_fds);
+  for (size_t i = 0; i < num_fds; ++i) {
+    reinterpret_cast<int*>(CMSG_DATA(cmsg))[i] =
+        aMsg.attached_handles_[i].get();
+  }
+
+  // This number will be sent in the header of the message. So, we
+  // can check it at the other side.
+  aMsg.header()->num_handles = num_fds;
+}
+
+size_t MiniTransceiver::PrepareBuffers(msghdr* aHdr, IPC::Message& aMsg) {
+  // Set iovec to send for all buffers of the Message.
+  iovec* iov = aHdr->msg_iov;
+  size_t iovlen = 0;
+  size_t bytes_to_send = 0;
+  for (Pickle::BufferList::IterImpl iter(aMsg.Buffers()); !iter.Done();
+       iter.Advance(aMsg.Buffers(), iter.RemainingInSegment())) {
+    char* data = iter.Data();
+    size_t size = iter.RemainingInSegment();
+    iov[iovlen].iov_base = data;
+    iov[iovlen].iov_len = size;
+    iovlen++;
+    MOZ_ASSERT(iovlen <= kMaxIOVecSize);
+    bytes_to_send += size;
+  }
+  MOZ_ASSERT(bytes_to_send <= kMaxDataSize);
+  aHdr->msg_iovlen = iovlen;
+
+  return bytes_to_send;
+}
+
+bool MiniTransceiver::Send(IPC::Message& aMsg) {
+#ifdef DEBUG
+  if (mState == STATE_SENDING) {
+    MOZ_CRASH(
+        "STATE_SENDING: It violates of request-response and no concurrent "
+        "rules");
+  }
+  mState = STATE_SENDING;
+#endif
+
+  auto clean_fdset = MakeScopeExit([&] { aMsg.attached_handles_.Clear(); });
+
+  size_t num_fds = aMsg.attached_handles_.Length();
+  msghdr hdr{};
+  InitMsgHdr(&hdr, kMaxIOVecSize, num_fds);
+
+  UniquePtr<msghdr, decltype(&DeinitMsgHdr)> uniq(&hdr, &DeinitMsgHdr);
+
+  PrepareFDs(&hdr, aMsg);
+  DebugOnly<size_t> bytes_to_send = PrepareBuffers(&hdr, aMsg);
+
+  ssize_t bytes_written = HANDLE_EINTR(sendmsg(mFd, &hdr, 0));
+
+  if (bytes_written < 0) {
+    char error[128];
+    SprintfLiteral(error, "sendmsg: %s", strerror(errno));
+    NS_WARNING(error);
+    return false;
+  }
+  MOZ_ASSERT(bytes_written == (ssize_t)bytes_to_send,
+             "The message is too big?!");
+
+  return true;
+}
+
+unsigned MiniTransceiver::RecvFDs(msghdr* aHdr, int* aAllFds,
+                                  unsigned aMaxFds) {
+  if (aHdr->msg_controllen == 0) {
+    return 0;
+  }
+
+  unsigned num_all_fds = 0;
+  for (cmsghdr* cmsg = CMSG_FIRSTHDR(aHdr); cmsg;
+       cmsg = CMSG_NXTHDR(aHdr, cmsg)) {
+    MOZ_ASSERT(cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS,
+               "Accept only SCM_RIGHTS to receive file descriptors");
+
+    unsigned payload_sz = cmsg->cmsg_len - CMSG_LEN(0);
+    MOZ_ASSERT(payload_sz % sizeof(int) == 0);
+
+    // Add fds to |aAllFds|
+    unsigned num_part_fds = payload_sz / sizeof(int);
+    int* part_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
+    MOZ_ASSERT(num_all_fds + num_part_fds <= aMaxFds);
+
+    memcpy(aAllFds + num_all_fds, part_fds, num_part_fds * sizeof(int));
+    num_all_fds += num_part_fds;
+  }
+  return num_all_fds;
+}
+
+bool MiniTransceiver::RecvData(char* aDataBuf, size_t aBufSize,
+                               uint32_t* aMsgSize, int* aFdsBuf,
+                               unsigned aMaxFds, unsigned* aNumFds) {
+  msghdr hdr;
+  InitMsgHdr(&hdr, 1, aMaxFds);
+
+  UniquePtr<msghdr, decltype(&DeinitMsgHdr)> uniq(&hdr, &DeinitMsgHdr);
+
+  // The buffer to collect all fds received from the socket.
+  int* all_fds = aFdsBuf;
+  unsigned num_all_fds = 0;
+
+  size_t total_readed = 0;
+  uint32_t msgsz = 0;
+  while (msgsz == 0 || total_readed < msgsz) {
+    // Set IO vector with the begin of the unused buffer.
+    hdr.msg_iov->iov_base = aDataBuf + total_readed;
+    hdr.msg_iov->iov_len = (msgsz == 0 ? aBufSize : msgsz) - total_readed;
+
+    // Read the socket
+    ssize_t bytes_readed = HANDLE_EINTR(recvmsg(mFd, &hdr, 0));
+    if (bytes_readed <= 0) {
+      // Closed or error!
+      return false;
+    }
+    total_readed += bytes_readed;
+    MOZ_ASSERT(total_readed <= aBufSize);
+
+    if (msgsz == 0) {
+      // Parse the size of the message.
+      // Get 0 if data in the buffer is no enough to get message size.
+      msgsz = IPC::Message::MessageSize(aDataBuf, aDataBuf + total_readed);
+    }
+
+    num_all_fds += RecvFDs(&hdr, all_fds + num_all_fds, aMaxFds - num_all_fds);
+  }
+
+  *aMsgSize = msgsz;
+  *aNumFds = num_all_fds;
+  return true;
+}
+
+bool MiniTransceiver::Recv(UniquePtr<IPC::Message>& aMsg) {
+#ifdef DEBUG
+  if (mState == STATE_RECEIVING) {
+    MOZ_CRASH(
+        "STATE_RECEIVING: It violates of request-response and no concurrent "
+        "rules");
+  }
+  mState = STATE_RECEIVING;
+#endif
+
+  UniquePtr<char[]> databuf = MakeUnique<char[]>(kMaxDataSize);
+  uint32_t msgsz = 0;
+  int all_fds[kMaxNumFds];
+  unsigned num_all_fds = 0;
+
+  if (!RecvData(databuf.get(), kMaxDataSize, &msgsz, all_fds, kMaxDataSize,
+                &num_all_fds)) {
+    return false;
+  }
+
+  // Create Message from databuf & all_fds.
+  UniquePtr<IPC::Message> msg = MakeUnique<IPC::Message>(databuf.get(), msgsz);
+  nsTArray<UniqueFileHandle> handles(num_all_fds);
+  for (unsigned i = 0; i < num_all_fds; ++i) {
+    handles.AppendElement(UniqueFileHandle(all_fds[i]));
+  }
+  msg->SetAttachedFileHandles(std::move(handles));
+
+  if (mDataBufClear == DataBufferClear::AfterReceiving) {
+    // Avoid content processes from reading the content of
+    // messages.
+    memset(databuf.get(), 0, msgsz);
+  }
+
+  MOZ_ASSERT(msg->header()->num_handles == msg->attached_handles_.Length(),
+             "The number of file descriptors in the header is different from"
+             " the number actually received");
+
+  aMsg = std::move(msg);
+  return true;
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/MiniTransceiver.h b/ipc/glue/MiniTransceiver.h
new file mode 100644
index 0000000000..9568dc2685
--- /dev/null
+++ b/ipc/glue/MiniTransceiver.h
@@ -0,0 +1,118 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 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 __MINITRANSCEIVER_H_
+#define __MINITRANSCEIVER_H_
+
+#include "chrome/common/ipc_message.h"
+#include "mozilla/Assertions.h"
+
+struct msghdr;
+
+namespace mozilla {
+namespace ipc {
+
+enum class DataBufferClear { None, AfterReceiving };
+
+/**
+ * This simple implementation handles the transmissions of IPC
+ * messages.
+ *
+ * It works according to a strict request-response paradigm, no
+ * concurrent messaging is allowed. Sending a message from A to B must
+ * be followed by another one from B to A. Because of this we don't
+ * need to handle data crossing the boundaries of a
+ * message. Transmission is done via blocking I/O to avoid the
+ * complexity of asynchronous I/O.
+ */
+class MiniTransceiver {
+ public:
+  /**
+   * \param aFd should be a blocking, no O_NONBLOCK, fd.
+   * \param aClearDataBuf is true to clear data buffers after
+   *                      receiving a message.
+   */
+  explicit MiniTransceiver(
+      int aFd, DataBufferClear aDataBufClear = DataBufferClear::None);
+
+  bool Send(IPC::Message& aMsg);
+  inline bool SendInfallible(IPC::Message& aMsg, const char* aCrashMessage) {
+    bool Ok = Send(aMsg);
+    if (!Ok) {
+      MOZ_CRASH_UNSAFE(aCrashMessage);
+    }
+    return Ok;
+  }
+
+  /**
+   * \param aMsg will hold the content of the received message.
+   * \return false if the fd is closed or with an error.
+   */
+  bool Recv(UniquePtr<IPC::Message>& aMsg);
+  inline bool RecvInfallible(UniquePtr<IPC::Message>& aMsg,
+                             const char* aCrashMessage) {
+    bool Ok = Recv(aMsg);
+    if (!Ok) {
+      MOZ_CRASH_UNSAFE(aCrashMessage);
+    }
+    return Ok;
+  }
+
+  int GetFD() { return mFd; }
+
+ private:
+  /**
+   * Set control buffer to make file descriptors ready to be sent
+   * through a socket.
+   */
+  void PrepareFDs(msghdr* aHdr, IPC::Message& aMsg);
+  /**
+   * Collect buffers of the message and make them ready to be sent.
+   *
+   * \param aHdr is the structure going to be passed to sendmsg().
+   * \param aMsg is the Message to send.
+   */
+  size_t PrepareBuffers(msghdr* aHdr, IPC::Message& aMsg);
+  /**
+   * Collect file descriptors received.
+   *
+   * \param aAllFds is where to store file descriptors.
+   * \param aMaxFds is how many file descriptors can be stored in aAllFds.
+   * \return the number of received file descriptors.
+   */
+  unsigned RecvFDs(msghdr* aHdr, int* aAllFds, unsigned aMaxFds);
+  /**
+   * Received data from the socket.
+   *
+   * \param aDataBuf is where to store the data from the socket.
+   * \param aBufSize is the size of the buffer.
+   * \param aMsgSize returns how many bytes were readed from the socket.
+   * \param aFdsBuf is the buffer to return file desriptors received.
+   * \param aMaxFds is the number of file descriptors that can be held.
+   * \param aNumFds returns the number of file descriptors received.
+   * \return true if sucess, or false for error.
+   */
+  bool RecvData(char* aDataBuf, size_t aBufSize, uint32_t* aMsgSize,
+                int* aFdsBuf, unsigned aMaxFds, unsigned* aNumFds);
+
+  int mFd;  // The file descriptor of the socket for IPC.
+
+#ifdef DEBUG
+  enum State {
+    STATE_NONE,
+    STATE_SENDING,
+    STATE_RECEIVING,
+  };
+  State mState;
+#endif
+
+  // Clear all received data in temp buffers to avoid data leaking.
+  DataBufferClear mDataBufClear;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // __MINITRANSCEIVER_H_
diff --git a/ipc/glue/Neutering.h b/ipc/glue/Neutering.h
new file mode 100644
index 0000000000..44cbe042ae
--- /dev/null
+++ b/ipc/glue/Neutering.h
@@ -0,0 +1,70 @@
+/* -*- 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_ipc_Neutering_h
+#define mozilla_ipc_Neutering_h
+
+/**
+ * This header declares RAII wrappers for Window neutering. See
+ * WindowsMessageLoop.cpp for more details.
+ */
+
+namespace mozilla {
+namespace ipc {
+
+/**
+ * This class is a RAII wrapper around Window neutering. As long as a
+ * NeuteredWindowRegion object is instantiated, Win32 windows belonging to the
+ * current thread will be neutered. It is safe to nest multiple instances of
+ * this class.
+ */
+class MOZ_RAII NeuteredWindowRegion {
+ public:
+  explicit NeuteredWindowRegion(bool aDoNeuter);
+  ~NeuteredWindowRegion();
+
+  /**
+   * This function clears any backlog of nonqueued messages that are pending for
+   * the current thread.
+   */
+  void PumpOnce();
+
+ private:
+  bool mNeuteredByThis;
+};
+
+/**
+ * This class is analagous to MutexAutoUnlock for Mutex; it is an RAII class
+ * that is to be instantiated within a NeuteredWindowRegion, thus temporarily
+ * disabling neutering for the remainder of its enclosing block.
+ * @see NeuteredWindowRegion
+ */
+class MOZ_RAII DeneuteredWindowRegion {
+ public:
+  explicit DeneuteredWindowRegion();
+  ~DeneuteredWindowRegion();
+
+ private:
+  bool mReneuter;
+};
+
+class MOZ_RAII SuppressedNeuteringRegion {
+ public:
+  explicit SuppressedNeuteringRegion();
+  ~SuppressedNeuteringRegion();
+
+  static inline bool IsNeuteringSuppressed() { return sSuppressNeutering; }
+
+ private:
+  bool mReenable;
+
+  static bool sSuppressNeutering;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_Neutering_h
diff --git a/ipc/glue/NodeChannel.cpp b/ipc/glue/NodeChannel.cpp
new file mode 100644
index 0000000000..587c6f9127
--- /dev/null
+++ b/ipc/glue/NodeChannel.cpp
@@ -0,0 +1,328 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/NodeChannel.h"
+#include "chrome/common/ipc_message.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "mojo/core/ports/name.h"
+#include "mozilla/ipc/BrowserProcessSubThread.h"
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+#ifdef FUZZING_SNAPSHOT
+#  include "mozilla/fuzzing/IPCFuzzController.h"
+#endif
+
+template <>
+struct IPC::ParamTraits<mozilla::ipc::NodeChannel::Introduction> {
+  using paramType = mozilla::ipc::NodeChannel::Introduction;
+  static void Write(MessageWriter* aWriter, paramType&& aParam) {
+    WriteParam(aWriter, aParam.mName);
+    WriteParam(aWriter, std::move(aParam.mHandle));
+    WriteParam(aWriter, aParam.mMode);
+    WriteParam(aWriter, aParam.mMyPid);
+    WriteParam(aWriter, aParam.mOtherPid);
+  }
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->mName) &&
+           ReadParam(aReader, &aResult->mHandle) &&
+           ReadParam(aReader, &aResult->mMode) &&
+           ReadParam(aReader, &aResult->mMyPid) &&
+           ReadParam(aReader, &aResult->mOtherPid);
+  }
+};
+
+namespace mozilla::ipc {
+
+NodeChannel::NodeChannel(const NodeName& aName,
+                         UniquePtr<IPC::Channel> aChannel, Listener* aListener,
+                         base::ProcessId aPid)
+    : mListener(aListener),
+      mName(aName),
+      mOtherPid(aPid),
+      mChannel(std::move(aChannel)) {}
+
+NodeChannel::~NodeChannel() { Close(); }
+
+// Called when the NodeChannel's refcount drops to `0`.
+void NodeChannel::Destroy() {
+  // Dispatch the `delete` operation to the IO thread. We need to do this even
+  // if we're already on the IO thread, as we could be in an `IPC::Channel`
+  // callback which unfortunately will not hold a strong reference to keep
+  // `this` alive.
+  MessageLoop* ioThread = XRE_GetIOMessageLoop();
+  if (ioThread->IsAcceptingTasks()) {
+    ioThread->PostTask(NewNonOwningRunnableMethod("NodeChannel::Destroy", this,
+                                                  &NodeChannel::FinalDestroy));
+    return;
+  }
+
+  // If the IOThread has already been destroyed, we must be shutting it down and
+  // need to synchronously invoke `FinalDestroy` to ensure we're cleaned up
+  // before the thread dies. This is safe as we can't be in a non-owning
+  // IPC::Channel callback at this point.
+  if (MessageLoop::current() == ioThread) {
+    FinalDestroy();
+    return;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("Leaking NodeChannel after IOThread destroyed!");
+}
+
+void NodeChannel::FinalDestroy() {
+  AssertIOThread();
+  delete this;
+}
+
+void NodeChannel::Start(bool aCallConnect) {
+  AssertIOThread();
+
+  mExistingListener = mChannel->set_listener(this);
+
+  std::queue<UniquePtr<IPC::Message>> pending;
+  if (mExistingListener) {
+    mExistingListener->GetQueuedMessages(pending);
+  }
+
+  if (aCallConnect) {
+    MOZ_ASSERT(pending.empty(), "unopened channel with pending messages?");
+    if (!mChannel->Connect()) {
+      OnChannelError();
+    }
+  } else {
+    // Check if our channel has already been connected, and knows the other PID.
+    base::ProcessId otherPid = mChannel->OtherPid();
+    if (otherPid != base::kInvalidProcessId) {
+      SetOtherPid(otherPid);
+    }
+
+    // Handle any events the previous listener had queued up. Make sure to stop
+    // if an error causes our channel to become closed.
+    while (!pending.empty() && mState != State::Closed) {
+      OnMessageReceived(std::move(pending.front()));
+      pending.pop();
+    }
+  }
+}
+
+void NodeChannel::Close() {
+  AssertIOThread();
+
+  if (mState.exchange(State::Closed) != State::Closed) {
+    mChannel->Close();
+    mChannel->set_listener(mExistingListener);
+  }
+}
+
+void NodeChannel::SetOtherPid(base::ProcessId aNewPid) {
+  AssertIOThread();
+  MOZ_ASSERT(aNewPid != base::kInvalidProcessId);
+
+  base::ProcessId previousPid = base::kInvalidProcessId;
+  if (!mOtherPid.compare_exchange_strong(previousPid, aNewPid)) {
+    // The PID was already set before this call, double-check that it's correct.
+    MOZ_RELEASE_ASSERT(previousPid == aNewPid,
+                       "Different sources disagree on the correct pid?");
+  }
+}
+
+#ifdef XP_MACOSX
+void NodeChannel::SetMachTaskPort(task_t aTask) {
+  AssertIOThread();
+
+  if (mState != State::Closed) {
+    mChannel->SetOtherMachTask(aTask);
+  }
+}
+#endif
+
+void NodeChannel::SendEventMessage(UniquePtr<IPC::Message> aMessage) {
+  // Make sure we're not sending a message with one of our special internal
+  // types ,as those should only be sent using the corresponding methods on
+  // NodeChannel.
+  MOZ_DIAGNOSTIC_ASSERT(aMessage->type() != BROADCAST_MESSAGE_TYPE &&
+                        aMessage->type() != INTRODUCE_MESSAGE_TYPE &&
+                        aMessage->type() != REQUEST_INTRODUCTION_MESSAGE_TYPE &&
+                        aMessage->type() != ACCEPT_INVITE_MESSAGE_TYPE);
+  SendMessage(std::move(aMessage));
+}
+
+void NodeChannel::RequestIntroduction(const NodeName& aPeerName) {
+  MOZ_ASSERT(aPeerName != mojo::core::ports::kInvalidNodeName);
+  auto message = MakeUnique<IPC::Message>(MSG_ROUTING_CONTROL,
+                                          REQUEST_INTRODUCTION_MESSAGE_TYPE);
+  IPC::MessageWriter writer(*message);
+  WriteParam(&writer, aPeerName);
+  SendMessage(std::move(message));
+}
+
+void NodeChannel::Introduce(Introduction aIntroduction) {
+  auto message =
+      MakeUnique<IPC::Message>(MSG_ROUTING_CONTROL, INTRODUCE_MESSAGE_TYPE);
+  IPC::MessageWriter writer(*message);
+  WriteParam(&writer, std::move(aIntroduction));
+  SendMessage(std::move(message));
+}
+
+void NodeChannel::Broadcast(UniquePtr<IPC::Message> aMessage) {
+  MOZ_DIAGNOSTIC_ASSERT(aMessage->type() == BROADCAST_MESSAGE_TYPE,
+                        "Can only broadcast messages with the correct type");
+  SendMessage(std::move(aMessage));
+}
+
+void NodeChannel::AcceptInvite(const NodeName& aRealName,
+                               const PortName& aInitialPort) {
+  MOZ_ASSERT(aRealName != mojo::core::ports::kInvalidNodeName);
+  MOZ_ASSERT(aInitialPort != mojo::core::ports::kInvalidPortName);
+  auto message =
+      MakeUnique<IPC::Message>(MSG_ROUTING_CONTROL, ACCEPT_INVITE_MESSAGE_TYPE);
+  IPC::MessageWriter writer(*message);
+  WriteParam(&writer, aRealName);
+  WriteParam(&writer, aInitialPort);
+  SendMessage(std::move(message));
+}
+
+void NodeChannel::SendMessage(UniquePtr<IPC::Message> aMessage) {
+  if (aMessage->size() > IPC::Channel::kMaximumMessageSize) {
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCMessageName,
+        nsDependentCString(aMessage->name()));
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCMessageSize,
+        static_cast<unsigned int>(aMessage->size()));
+    MOZ_CRASH("IPC message size is too large");
+  }
+  aMessage->AssertAsLargeAsHeader();
+
+#ifdef FUZZING_SNAPSHOT
+  if (mBlockSendRecv) {
+    return;
+  }
+#endif
+
+  if (mState != State::Active) {
+    NS_WARNING("Dropping message as channel has been closed");
+    return;
+  }
+
+  // NOTE: As this is not guaranteed to be running on the I/O thread, the
+  // channel may have become closed since we checked above. IPC::Channel will
+  // handle that and return `false` here, so we can re-check `mState`.
+  if (!mChannel->Send(std::move(aMessage))) {
+    NS_WARNING("Call to Send() failed");
+
+    // If we're still active, update `mState` to `State::Closing`, and dispatch
+    // a runnable to actually close our channel.
+    State expected = State::Active;
+    if (mState.compare_exchange_strong(expected, State::Closing)) {
+      XRE_GetIOMessageLoop()->PostTask(
+          NewRunnableMethod("NodeChannel::CloseForSendError", this,
+                            &NodeChannel::OnChannelError));
+    }
+  }
+}
+
+void NodeChannel::OnMessageReceived(UniquePtr<IPC::Message> aMessage) {
+  AssertIOThread();
+
+#ifdef FUZZING_SNAPSHOT
+  if (mBlockSendRecv && !aMessage->IsFuzzMsg()) {
+    return;
+  }
+#endif
+
+  IPC::MessageReader reader(*aMessage);
+  switch (aMessage->type()) {
+    case REQUEST_INTRODUCTION_MESSAGE_TYPE: {
+      NodeName name;
+      if (IPC::ReadParam(&reader, &name)) {
+        mListener->OnRequestIntroduction(mName, name);
+        return;
+      }
+      break;
+    }
+    case INTRODUCE_MESSAGE_TYPE: {
+      Introduction introduction;
+      if (IPC::ReadParam(&reader, &introduction)) {
+        mListener->OnIntroduce(mName, std::move(introduction));
+        return;
+      }
+      break;
+    }
+    case BROADCAST_MESSAGE_TYPE: {
+      mListener->OnBroadcast(mName, std::move(aMessage));
+      return;
+    }
+    case ACCEPT_INVITE_MESSAGE_TYPE: {
+      NodeName realName;
+      PortName initialPort;
+      if (IPC::ReadParam(&reader, &realName) &&
+          IPC::ReadParam(&reader, &initialPort)) {
+        mListener->OnAcceptInvite(mName, realName, initialPort);
+        return;
+      }
+      break;
+    }
+    // Assume all unrecognized types are intended as user event messages, and
+    // deliver them to our listener as such. This allows us to use the same type
+    // field for both internal messages and protocol messages.
+    //
+    // FIXME: Consider doing something cleaner in the future?
+    case EVENT_MESSAGE_TYPE:
+    default: {
+#ifdef FUZZING_SNAPSHOT
+      if (!fuzzing::IPCFuzzController::instance().ObserveIPCMessage(
+              this, *aMessage)) {
+        return;
+      }
+#endif
+
+      mListener->OnEventMessage(mName, std::move(aMessage));
+      return;
+    }
+  }
+
+  // If we got to this point without early returning the message was malformed
+  // in some way. Report an error.
+
+  NS_WARNING("NodeChannel received a malformed message");
+  OnChannelError();
+}
+
+void NodeChannel::OnChannelConnected(base::ProcessId aPeerPid) {
+  AssertIOThread();
+
+  SetOtherPid(aPeerPid);
+
+  // We may need to tell our original listener (which will be the process launch
+  // code) that the the channel has been connected to unblock completing the
+  // process launch.
+  // FIXME: This is super sketchy, but it's also what we were already doing. We
+  // should swap this out for something less sketchy.
+  if (mExistingListener) {
+    mExistingListener->OnChannelConnected(aPeerPid);
+  }
+}
+
+void NodeChannel::OnChannelError() {
+  AssertIOThread();
+
+  State prev = mState.exchange(State::Closed);
+  if (prev == State::Closed) {
+    return;
+  }
+
+  // Clean up the channel and make sure we're no longer the active listener.
+  mChannel->Close();
+  MOZ_ALWAYS_TRUE(this == mChannel->set_listener(mExistingListener));
+
+  // Tell our listener about the error.
+  mListener->OnChannelError(mName);
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/NodeChannel.h b/ipc/glue/NodeChannel.h
new file mode 100644
index 0000000000..eae6cb655e
--- /dev/null
+++ b/ipc/glue/NodeChannel.h
@@ -0,0 +1,175 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_NodeChannel_h
+#define mozilla_ipc_NodeChannel_h
+
+#include "mojo/core/ports/node.h"
+#include "mojo/core/ports/node_delegate.h"
+#include "base/process.h"
+#include "chrome/common/ipc_message.h"
+#include "chrome/common/ipc_channel.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "nsISupports.h"
+#include "nsTHashMap.h"
+#include "mozilla/Queue.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/UniquePtr.h"
+
+#ifdef FUZZING_SNAPSHOT
+#  include "mozilla/fuzzing/IPCFuzzController.h"
+#endif
+
+namespace mozilla::ipc {
+
+class NodeController;
+
+// Represents a live connection between our Node and a remote process. This
+// object acts as an IPC::Channel listener and performs basic processing on
+// messages as they're passed between processes.
+
+class NodeChannel final : public IPC::Channel::Listener {
+  using NodeName = mojo::core::ports::NodeName;
+  using PortName = mojo::core::ports::PortName;
+
+#ifdef FUZZING_SNAPSHOT
+  // Required because IPCFuzzController calls OnMessageReceived.
+  friend class mozilla::fuzzing::IPCFuzzController;
+#endif
+
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING_WITH_DESTROY(NodeChannel, Destroy())
+
+  struct Introduction {
+    NodeName mName;
+    IPC::Channel::ChannelHandle mHandle;
+    IPC::Channel::Mode mMode;
+    base::ProcessId mMyPid = base::kInvalidProcessId;
+    base::ProcessId mOtherPid = base::kInvalidProcessId;
+  };
+
+  class Listener {
+   public:
+    virtual ~Listener() = default;
+
+    NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+    virtual void OnEventMessage(const NodeName& aFromNode,
+                                UniquePtr<IPC::Message> aMessage) = 0;
+    virtual void OnBroadcast(const NodeName& aFromNode,
+                             UniquePtr<IPC::Message> aMessage) = 0;
+    virtual void OnIntroduce(const NodeName& aFromNode,
+                             Introduction aIntroduction) = 0;
+    virtual void OnRequestIntroduction(const NodeName& aFromNode,
+                                       const NodeName& aName) = 0;
+    virtual void OnAcceptInvite(const NodeName& aFromNode,
+                                const NodeName& aRealName,
+                                const PortName& aInitialPort) = 0;
+    virtual void OnChannelError(const NodeName& aFromNode) = 0;
+  };
+
+  NodeChannel(const NodeName& aName, UniquePtr<IPC::Channel> aChannel,
+              Listener* aListener,
+              base::ProcessId aPid = base::kInvalidProcessId);
+
+  // Send the given message over this peer channel link. May be called from any
+  // thread.
+  void SendEventMessage(UniquePtr<IPC::Message> aMessage);
+
+  // Ask the broker process to broadcast this message to every node. May be
+  // called from any thread.
+  void Broadcast(UniquePtr<IPC::Message> aMessage);
+
+  // Ask the broker process to introduce this node to another node with the
+  // given name. May be called from any thread.
+  void RequestIntroduction(const NodeName& aPeerName);
+
+  // Send an introduction to the target node. May be called from any thread.
+  void Introduce(Introduction aIntroduction);
+
+  void AcceptInvite(const NodeName& aRealName, const PortName& aInitialPort);
+
+  // The PID of the remote process, once known. May be called from any thread.
+  base::ProcessId OtherPid() const { return mOtherPid; }
+
+  // Start communicating with the remote process using this NodeChannel. MUST BE
+  // CALLED FROM THE IO THREAD.
+  void Start(bool aCallConnect = true);
+
+  // Stop communicating with the remote process using this NodeChannel, MUST BE
+  // CALLED FROM THE IO THREAD.
+  void Close();
+
+  // Only ever called by NodeController to update the name after an invite has
+  // completed. MUST BE CALLED FROM THE IO THREAD.
+  void SetName(const NodeName& aNewName) { mName = aNewName; }
+
+#ifdef FUZZING_SNAPSHOT
+  // MUST BE CALLED FROM THE IO THREAD.
+  const NodeName& GetName() { return mName; }
+#endif
+
+#ifdef XP_MACOSX
+  // Called by the GeckoChildProcessHost to provide the task_t for the peer
+  // process. MUST BE CALLED FROM THE IO THREAD.
+  void SetMachTaskPort(task_t aTask);
+#endif
+
+ private:
+  ~NodeChannel();
+
+  void Destroy();
+  void FinalDestroy();
+
+  // Update the known PID for the remote process. IO THREAD ONLY
+  void SetOtherPid(base::ProcessId aNewPid);
+
+  void SendMessage(UniquePtr<IPC::Message> aMessage);
+
+  // IPC::Channel::Listener implementation
+  void OnMessageReceived(UniquePtr<IPC::Message> aMessage) override;
+  void OnChannelConnected(base::ProcessId aPeerPid) override;
+  void OnChannelError() override;
+
+  // NOTE: This strong reference will create a reference cycle between the
+  // listener and the NodeChannel while it is in use. The Listener must clear
+  // its reference to the NodeChannel to avoid leaks before shutdown.
+  const RefPtr<Listener> mListener;
+
+  // The apparent name of this Node. This may change during the invite process
+  // while waiting for the remote node name to be communicated to us.
+
+  // WARNING: This must only be accessed on the IO thread.
+  NodeName mName;
+
+  // NOTE: This won't change once the connection has been established, but may
+  // be `-1` until then. This will only be written to on the IO thread, but may
+  // be read from other threads.
+  std::atomic<base::ProcessId> mOtherPid;
+
+  // WARNING: Most methods on the IPC::Channel are only safe to call on the IO
+  // thread, however it is safe to call `Send()` and `IsClosed()` from other
+  // threads. See IPC::Channel's documentation for details.
+  const mozilla::UniquePtr<IPC::Channel> mChannel;
+
+  // The state will start out as `State::Active`, and will only transition to
+  // `State::Closed` on the IO thread. If a Send fails, the state will
+  // transition to `State::Closing`, and a runnable will be dispatched to the
+  // I/O thread to notify callbacks.
+  enum class State { Active, Closing, Closed };
+  std::atomic<State> mState = State::Active;
+
+#ifdef FUZZING_SNAPSHOT
+  std::atomic<bool> mBlockSendRecv = false;
+#endif
+
+  // WARNING: Must only be accessed on the IO thread.
+  WeakPtr<IPC::Channel::Listener> mExistingListener;
+};
+
+}  // namespace mozilla::ipc
+
+#endif
diff --git a/ipc/glue/NodeController.cpp b/ipc/glue/NodeController.cpp
new file mode 100644
index 0000000000..72e9b9a8fe
--- /dev/null
+++ b/ipc/glue/NodeController.cpp
@@ -0,0 +1,856 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/NodeController.h"
+#include "MainThreadUtils.h"
+#include "base/process_util.h"
+#include "chrome/common/ipc_message.h"
+#include "mojo/core/ports/name.h"
+#include "mojo/core/ports/node.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/RandomNum.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ToString.h"
+#include "mozilla/ipc/BrowserProcessSubThread.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/mozalloc.h"
+#include "nsISerialEventTarget.h"
+#include "nsTArray.h"
+#include "nsXULAppAPI.h"
+#include "nsPrintfCString.h"
+
+#define PORTS_ALWAYS_OK(expr) MOZ_ALWAYS_TRUE(mojo::core::ports::OK == (expr))
+
+namespace mozilla::ipc {
+
+static StaticRefPtr<NodeController> gNodeController;
+
+static LazyLogModule gNodeControllerLog{"NodeController"};
+
+// Helper logger macro which includes the name of the `this` NodeController in
+// the logged messages.
+#define NODECONTROLLER_LOG(level_, fmt_, ...) \
+  MOZ_LOG(gNodeControllerLog, level_,         \
+          ("[%s]: " fmt_, ToString(mName).c_str(), ##__VA_ARGS__))
+
+// Helper warning macro which both does logger logging and emits NS_WARNING logs
+// under debug mode.
+#ifdef DEBUG
+#  define NODECONTROLLER_WARNING(fmt_, ...)                                \
+    do {                                                                   \
+      nsPrintfCString warning("[%s]: " fmt_, ToString(mName).c_str(),      \
+                              ##__VA_ARGS__);                              \
+      NS_WARNING(warning.get());                                           \
+      MOZ_LOG(gNodeControllerLog, LogLevel::Debug, ("%s", warning.get())); \
+    } while (0)
+#else
+#  define NODECONTROLLER_WARNING(fmt_, ...) \
+    NODECONTROLLER_LOG(LogLevel::Warning, fmt_, ##__VA_ARGS__)
+#endif
+
+NodeController::NodeController(const NodeName& aName)
+    : mName(aName), mNode(MakeUnique<Node>(aName, this)) {}
+
+NodeController::~NodeController() {
+  auto state = mState.Lock();
+  MOZ_RELEASE_ASSERT(state->mPeers.IsEmpty(),
+                     "Destroying NodeController before closing all peers");
+  MOZ_RELEASE_ASSERT(state->mInvites.IsEmpty(),
+                     "Destroying NodeController before closing all invites");
+};
+
+// FIXME: Actually provide some way to create the thing.
+/* static */ NodeController* NodeController::GetSingleton() {
+  MOZ_ASSERT(gNodeController);
+  return gNodeController;
+}
+
+std::pair<ScopedPort, ScopedPort> NodeController::CreatePortPair() {
+  PortRef port0, port1;
+  PORTS_ALWAYS_OK(mNode->CreatePortPair(&port0, &port1));
+  return {ScopedPort{std::move(port0), this},
+          ScopedPort{std::move(port1), this}};
+}
+
+auto NodeController::GetPort(const PortName& aName) -> PortRef {
+  PortRef port;
+  int rv = mNode->GetPort(aName, &port);
+  if (NS_WARN_IF(rv != mojo::core::ports::OK)) {
+    NODECONTROLLER_WARNING("Call to GetPort(%s) Failed",
+                           ToString(aName).c_str());
+    return {};
+  }
+  return port;
+}
+
+void NodeController::SetPortObserver(const PortRef& aPort,
+                                     PortObserver* aObserver) {
+  PORTS_ALWAYS_OK(mNode->SetUserData(aPort, aObserver));
+}
+
+auto NodeController::GetStatus(const PortRef& aPort) -> Maybe<PortStatus> {
+  PortStatus status{};
+  int rv = mNode->GetStatus(aPort, &status);
+  if (rv != mojo::core::ports::OK) {
+    return Nothing();
+  }
+  return Some(status);
+}
+
+void NodeController::ClosePort(const PortRef& aPort) {
+  PORTS_ALWAYS_OK(mNode->ClosePort(aPort));
+}
+
+bool NodeController::GetMessage(const PortRef& aPort,
+                                UniquePtr<IPC::Message>* aMessage) {
+  UniquePtr<UserMessageEvent> messageEvent;
+  int rv = mNode->GetMessage(aPort, &messageEvent, nullptr);
+  if (rv != mojo::core::ports::OK) {
+    if (rv == mojo::core::ports::ERROR_PORT_PEER_CLOSED) {
+      return false;
+    }
+    MOZ_CRASH("GetMessage on port in invalid state");
+  }
+
+  if (messageEvent) {
+    UniquePtr<IPC::Message> message = messageEvent->TakeMessage<IPC::Message>();
+
+    // If our UserMessageEvent has any ports directly attached to it, fetch them
+    // from our node and attach them to the IPC::Message we extracted.
+    //
+    // It's important to only do this if we have nonempty set of ports on the
+    // event, as we may have never serialized our IPC::Message's ports onto the
+    // event if it was routed in-process.
+    if (messageEvent->num_ports() > 0) {
+      nsTArray<ScopedPort> attachedPorts(messageEvent->num_ports());
+      for (size_t i = 0; i < messageEvent->num_ports(); ++i) {
+        attachedPorts.AppendElement(
+            ScopedPort{GetPort(messageEvent->ports()[i]), this});
+      }
+      message->SetAttachedPorts(std::move(attachedPorts));
+    }
+
+    *aMessage = std::move(message);
+  } else {
+    *aMessage = nullptr;
+  }
+  return true;
+}
+
+bool NodeController::SendUserMessage(const PortRef& aPort,
+                                     UniquePtr<IPC::Message> aMessage) {
+  auto messageEvent = MakeUnique<UserMessageEvent>(0);
+  messageEvent->AttachMessage(std::move(aMessage));
+
+  int rv = mNode->SendUserMessage(aPort, std::move(messageEvent));
+  if (rv == mojo::core::ports::OK) {
+    return true;
+  }
+  if (rv == mojo::core::ports::ERROR_PORT_PEER_CLOSED) {
+    NODECONTROLLER_LOG(LogLevel::Debug,
+                       "Ignoring message to port %s as peer was closed",
+                       ToString(aPort.name()).c_str());
+    return true;
+  }
+  NODECONTROLLER_WARNING("Failed to send message to port %s",
+                         ToString(aPort.name()).c_str());
+  return false;
+}
+
+auto NodeController::SerializeEventMessage(UniquePtr<Event> aEvent,
+                                           const NodeName* aRelayTarget,
+                                           uint32_t aType)
+    -> UniquePtr<IPC::Message> {
+  UniquePtr<IPC::Message> message;
+  if (aEvent->type() == Event::kUserMessage) {
+    MOZ_DIAGNOSTIC_ASSERT(
+        aType == EVENT_MESSAGE_TYPE,
+        "Can only send a UserMessage in an EVENT_MESSAGE_TYPE");
+    message = static_cast<UserMessageEvent*>(aEvent.get())
+                  ->TakeMessage<IPC::Message>();
+  } else {
+    message = MakeUnique<IPC::Message>(MSG_ROUTING_CONTROL, aType);
+  }
+
+  message->set_relay(aRelayTarget != nullptr);
+
+  size_t length = aEvent->GetSerializedSize();
+  if (aRelayTarget) {
+    length += sizeof(NodeName);
+  }
+
+  // Use an intermediate buffer to serialize to avoid potential issues with the
+  // segmented `IPC::Message` bufferlist. This should be fairly cheap, as the
+  // majority of events are fairly small.
+  Vector<char, 256, InfallibleAllocPolicy> buffer;
+  (void)buffer.initLengthUninitialized(length);
+  if (aRelayTarget) {
+    memcpy(buffer.begin(), aRelayTarget, sizeof(NodeName));
+    aEvent->Serialize(buffer.begin() + sizeof(NodeName));
+  } else {
+    aEvent->Serialize(buffer.begin());
+  }
+
+  message->WriteFooter(buffer.begin(), buffer.length());
+  message->set_event_footer_size(buffer.length());
+
+#ifdef DEBUG
+  // Debug-assert that we can read the same data back out of the buffer.
+  MOZ_ASSERT(message->event_footer_size() == length);
+  Vector<char, 256, InfallibleAllocPolicy> buffer2;
+  (void)buffer2.initLengthUninitialized(message->event_footer_size());
+  MOZ_ASSERT(message->ReadFooter(buffer2.begin(), buffer2.length(),
+                                 /* truncate */ false));
+  MOZ_ASSERT(!memcmp(buffer2.begin(), buffer.begin(), buffer.length()));
+#endif
+
+  return message;
+}
+
+auto NodeController::DeserializeEventMessage(UniquePtr<IPC::Message> aMessage,
+                                             NodeName* aRelayTarget)
+    -> UniquePtr<Event> {
+  if (aMessage->is_relay() && !aRelayTarget) {
+    NODECONTROLLER_WARNING("Unexpected relay message '%s'", aMessage->name());
+    return nullptr;
+  }
+
+  Vector<char, 256, InfallibleAllocPolicy> buffer;
+  (void)buffer.initLengthUninitialized(aMessage->event_footer_size());
+  // Truncate the message when reading the footer, so that the extra footer data
+  // is no longer present in the message. This allows future code to eventually
+  // send the same `IPC::Message` to another process.
+  if (!aMessage->ReadFooter(buffer.begin(), buffer.length(),
+                            /* truncate */ true)) {
+    NODECONTROLLER_WARNING("Call to ReadFooter for message '%s' Failed",
+                           aMessage->name());
+    return nullptr;
+  }
+  aMessage->set_event_footer_size(0);
+
+  UniquePtr<Event> event;
+  if (aRelayTarget) {
+    MOZ_ASSERT(aMessage->is_relay());
+    if (buffer.length() < sizeof(NodeName)) {
+      NODECONTROLLER_WARNING(
+          "Insufficient space in message footer for message '%s'",
+          aMessage->name());
+      return nullptr;
+    }
+    memcpy(aRelayTarget, buffer.begin(), sizeof(NodeName));
+    event = Event::Deserialize(buffer.begin() + sizeof(NodeName),
+                               buffer.length() - sizeof(NodeName));
+  } else {
+    event = Event::Deserialize(buffer.begin(), buffer.length());
+  }
+
+  if (!event) {
+    NODECONTROLLER_WARNING("Call to Event::Deserialize for message '%s' Failed",
+                           aMessage->name());
+    return nullptr;
+  }
+
+  if (event->type() == Event::kUserMessage) {
+    static_cast<UserMessageEvent*>(event.get())
+        ->AttachMessage(std::move(aMessage));
+  }
+  return event;
+}
+
+already_AddRefed<NodeChannel> NodeController::GetNodeChannel(
+    const NodeName& aName) {
+  auto state = mState.Lock();
+  return do_AddRef(state->mPeers.Get(aName));
+}
+
+void NodeController::DropPeer(NodeName aNodeName) {
+  AssertIOThread();
+
+#ifdef FUZZING_SNAPSHOT
+  MOZ_FUZZING_IPC_DROP_PEER("NodeController::DropPeer");
+#endif
+
+  Invite invite;
+  RefPtr<NodeChannel> channel;
+  nsTArray<PortRef> pendingMerges;
+  {
+    auto state = mState.Lock();
+    state->mPeers.Remove(aNodeName, &channel);
+    state->mPendingMessages.Remove(aNodeName);
+    state->mInvites.Remove(aNodeName, &invite);
+    state->mPendingMerges.Remove(aNodeName, &pendingMerges);
+  }
+
+  NODECONTROLLER_LOG(LogLevel::Info, "Dropping Peer %s (pid: %" PRIPID ")",
+                     ToString(aNodeName).c_str(),
+                     channel ? channel->OtherPid() : base::kInvalidProcessId);
+
+  if (channel) {
+    channel->Close();
+  }
+  if (invite.mChannel) {
+    invite.mChannel->Close();
+  }
+  if (invite.mToMerge.is_valid()) {
+    // Ignore any possible errors here.
+    (void)mNode->ClosePort(invite.mToMerge);
+  }
+  for (auto& port : pendingMerges) {
+    // Ignore any possible errors here.
+    (void)mNode->ClosePort(port);
+  }
+  mNode->LostConnectionToNode(aNodeName);
+}
+
+void NodeController::ForwardEvent(const NodeName& aNode,
+                                  UniquePtr<Event> aEvent) {
+  if (aNode == mName) {
+    (void)mNode->AcceptEvent(std::move(aEvent));
+  } else {
+    // On Windows and macOS, messages holding HANDLEs or mach ports must be
+    // relayed via the broker process so it can transfer ownership.
+    bool needsRelay = false;
+#if defined(XP_WIN) || defined(XP_MACOSX)
+    if (!IsBroker() && aNode != kBrokerNodeName &&
+        aEvent->type() == Event::kUserMessage) {
+      auto* userEvent = static_cast<UserMessageEvent*>(aEvent.get());
+      needsRelay =
+          userEvent->HasMessage() &&
+          userEvent->GetMessage<IPC::Message>()->num_relayed_attachments() > 0;
+    }
+#endif
+
+    UniquePtr<IPC::Message> message =
+        SerializeEventMessage(std::move(aEvent), needsRelay ? &aNode : nullptr);
+    MOZ_ASSERT(message->is_relay() == needsRelay,
+               "Message relay status set incorrectly");
+
+    RefPtr<NodeChannel> peer;
+    RefPtr<NodeChannel> broker;
+    bool needsIntroduction = false;
+    {
+      auto state = mState.Lock();
+
+      // Check if we know this peer. If we don't, we'll need to request an
+      // introduction.
+      peer = state->mPeers.Get(aNode);
+      if (!peer || needsRelay) {
+        if (IsBroker()) {
+          NODECONTROLLER_WARNING("Ignoring message '%s' to unknown peer %s",
+                                 message->name(), ToString(aNode).c_str());
+          return;
+        }
+
+        broker = state->mPeers.Get(kBrokerNodeName);
+        if (!broker) {
+          NODECONTROLLER_WARNING(
+              "Ignoring message '%s' to peer %s due to a missing broker",
+              message->name(), ToString(aNode).c_str());
+          return;
+        }
+
+        if (!needsRelay) {
+          auto& queue =
+              state->mPendingMessages.LookupOrInsertWith(aNode, [&]() {
+                needsIntroduction = true;
+                return Queue<UniquePtr<IPC::Message>, 64>{};
+              });
+          queue.Push(std::move(message));
+        }
+      }
+    }
+
+    MOZ_ASSERT(!needsIntroduction || !needsRelay,
+               "Only one of the two should ever be set");
+
+    if (needsRelay) {
+      NODECONTROLLER_LOG(LogLevel::Info,
+                         "Relaying message '%s' for peer %s due to %" PRIu32
+                         " attachments",
+                         message->name(), ToString(aNode).c_str(),
+                         message->num_relayed_attachments());
+      MOZ_ASSERT(message->num_relayed_attachments() > 0 && broker);
+      broker->SendEventMessage(std::move(message));
+    } else if (needsIntroduction) {
+      MOZ_ASSERT(broker);
+      broker->RequestIntroduction(aNode);
+    } else if (peer) {
+      peer->SendEventMessage(std::move(message));
+    }
+  }
+}
+
+void NodeController::BroadcastEvent(UniquePtr<Event> aEvent) {
+  UniquePtr<IPC::Message> message =
+      SerializeEventMessage(std::move(aEvent), nullptr, BROADCAST_MESSAGE_TYPE);
+
+  if (IsBroker()) {
+    OnBroadcast(mName, std::move(message));
+  } else if (RefPtr<NodeChannel> broker = GetNodeChannel(kBrokerNodeName)) {
+    broker->Broadcast(std::move(message));
+  } else {
+    NODECONTROLLER_WARNING(
+        "Trying to broadcast event, but no connection to broker");
+  }
+}
+
+void NodeController::PortStatusChanged(const PortRef& aPortRef) {
+  RefPtr<UserData> userData;
+  int rv = mNode->GetUserData(aPortRef, &userData);
+  if (rv != mojo::core::ports::OK) {
+    NODECONTROLLER_WARNING("GetUserData call for port '%s' failed",
+                           ToString(aPortRef.name()).c_str());
+    return;
+  }
+  if (userData) {
+    // All instances of `UserData` attached to ports in this node must be of
+    // type `PortObserver`, so we can call `OnPortStatusChanged` directly on
+    // them.
+    static_cast<PortObserver*>(userData.get())->OnPortStatusChanged();
+  }
+}
+
+void NodeController::OnEventMessage(const NodeName& aFromNode,
+                                    UniquePtr<IPC::Message> aMessage) {
+  AssertIOThread();
+
+  bool isRelay = aMessage->is_relay();
+  if (isRelay && aMessage->num_relayed_attachments() == 0) {
+    NODECONTROLLER_WARNING(
+        "Invalid relay message without relayed attachments from peer %s!",
+        ToString(aFromNode).c_str());
+    DropPeer(aFromNode);
+    return;
+  }
+
+  NodeName relayTarget;
+  UniquePtr<Event> event = DeserializeEventMessage(
+      std::move(aMessage), isRelay ? &relayTarget : nullptr);
+  if (!event) {
+    NODECONTROLLER_WARNING("Invalid EventMessage from peer %s!",
+                           ToString(aFromNode).c_str());
+    DropPeer(aFromNode);
+    return;
+  }
+
+  NodeName fromNode = aFromNode;
+#if defined(XP_WIN) || defined(XP_MACOSX)
+  if (isRelay) {
+    if (event->type() != Event::kUserMessage) {
+      NODECONTROLLER_WARNING(
+          "Unexpected relay of non-UserMessage event from peer %s!",
+          ToString(aFromNode).c_str());
+      DropPeer(aFromNode);
+      return;
+    }
+
+    // If we're the broker, then we'll need to forward this message on to the
+    // true recipient. To do this, we re-serialize the message, passing along
+    // the original source node, and send it to the final node.
+    if (IsBroker()) {
+      UniquePtr<IPC::Message> message =
+          SerializeEventMessage(std::move(event), &aFromNode);
+      if (!message) {
+        NODECONTROLLER_WARNING(
+            "Relaying EventMessage from peer %s failed to re-serialize!",
+            ToString(aFromNode).c_str());
+        DropPeer(aFromNode);
+        return;
+      }
+      MOZ_ASSERT(message->is_relay(), "Message stopped being a relay message?");
+      MOZ_ASSERT(message->num_relayed_attachments() > 0,
+                 "Message doesn't have relayed attachments?");
+
+      NODECONTROLLER_LOG(
+          LogLevel::Info,
+          "Relaying message '%s' from peer %s to peer %s (%" PRIu32
+          " attachments)",
+          message->name(), ToString(aFromNode).c_str(),
+          ToString(relayTarget).c_str(), message->num_relayed_attachments());
+
+      RefPtr<NodeChannel> peer;
+      {
+        auto state = mState.Lock();
+        peer = state->mPeers.Get(relayTarget);
+      }
+      if (!peer) {
+        NODECONTROLLER_WARNING(
+            "Dropping relayed message from %s to unknown peer %s",
+            ToString(aFromNode).c_str(), ToString(relayTarget).c_str());
+        return;
+      }
+
+      peer->SendEventMessage(std::move(message));
+      return;
+    }
+
+    // Otherwise, we're the final recipient, so we can continue & process the
+    // message as usual.
+    if (aFromNode != kBrokerNodeName) {
+      NODECONTROLLER_WARNING(
+          "Unexpected relayed EventMessage from non-broker peer %s!",
+          ToString(aFromNode).c_str());
+      DropPeer(aFromNode);
+      return;
+    }
+    fromNode = relayTarget;
+
+    NODECONTROLLER_LOG(LogLevel::Info, "Got relayed message from peer %s",
+                       ToString(fromNode).c_str());
+  }
+#endif
+
+  // If we're getting a requested port merge from another process, check to make
+  // sure that we're expecting the request, and record that the merge has
+  // arrived so we don't try to close the port on error.
+  if (event->type() == Event::kMergePort) {
+    // Check that the target port for the merge actually exists.
+    auto targetPort = GetPort(event->port_name());
+    if (!targetPort.is_valid()) {
+      NODECONTROLLER_WARNING(
+          "Unexpected MergePortEvent from peer %s for unknown port %s",
+          ToString(fromNode).c_str(), ToString(event->port_name()).c_str());
+      DropPeer(fromNode);
+      return;
+    }
+
+    // Check if `targetPort` is in our pending merges entry for the given source
+    // node. If this makes the `mPendingMerges` entry empty, remove it.
+    bool expectingMerge = [&] {
+      auto state = mState.Lock();
+      auto pendingMerges = state->mPendingMerges.Lookup(aFromNode);
+      if (!pendingMerges) {
+        return false;
+      }
+      size_t removed = pendingMerges->RemoveElementsBy(
+          [&](auto& port) { return port.name() == targetPort.name(); });
+      if (removed != 0 && pendingMerges->IsEmpty()) {
+        pendingMerges.Remove();
+      }
+      return removed != 0;
+    }();
+
+    if (!expectingMerge) {
+      NODECONTROLLER_WARNING(
+          "Unexpected MergePortEvent from peer %s for port %s",
+          ToString(fromNode).c_str(), ToString(event->port_name()).c_str());
+      DropPeer(fromNode);
+      return;
+    }
+  }
+
+  (void)mNode->AcceptEvent(std::move(event));
+}
+
+void NodeController::OnBroadcast(const NodeName& aFromNode,
+                                 UniquePtr<IPC::Message> aMessage) {
+  MOZ_DIAGNOSTIC_ASSERT(aMessage->type() == BROADCAST_MESSAGE_TYPE);
+
+  // NOTE: This method may be called off of the IO thread by the
+  // `BroadcastEvent` node callback.
+  if (!IsBroker()) {
+    NODECONTROLLER_WARNING("Broadcast request received by non-broker node");
+    return;
+  }
+
+  UniquePtr<Event> event = DeserializeEventMessage(std::move(aMessage));
+  if (!event) {
+    NODECONTROLLER_WARNING("Invalid broadcast message from peer");
+    return;
+  }
+
+  nsTArray<RefPtr<NodeChannel>> peers;
+  {
+    auto state = mState.Lock();
+    peers.SetCapacity(state->mPeers.Count());
+    for (const auto& peer : state->mPeers.Values()) {
+      peers.AppendElement(peer);
+    }
+  }
+  for (const auto& peer : peers) {
+    // NOTE: This `clone` operation is only supported for a limited number of
+    // message types by the ports API, which provides some extra security by
+    // only allowing those specific types of messages to be broadcasted.
+    // Messages which don't support `Clone` cannot be broadcast, and the ports
+    // library will not attempt to broadcast them.
+    auto clone = event->Clone();
+    if (!clone) {
+      NODECONTROLLER_WARNING("Attempt to broadcast unsupported message");
+      break;
+    }
+
+    peer->SendEventMessage(SerializeEventMessage(std::move(clone)));
+  }
+}
+
+void NodeController::OnIntroduce(const NodeName& aFromNode,
+                                 NodeChannel::Introduction aIntroduction) {
+  AssertIOThread();
+
+  if (aFromNode != kBrokerNodeName) {
+    NODECONTROLLER_WARNING("Introduction received from non-broker node");
+    DropPeer(aFromNode);
+    return;
+  }
+
+  MOZ_ASSERT(aIntroduction.mMyPid == base::GetCurrentProcId(),
+             "We're the wrong process to receive this?");
+
+  if (!aIntroduction.mHandle) {
+    NODECONTROLLER_WARNING("Could not be introduced to peer %s",
+                           ToString(aIntroduction.mName).c_str());
+    mNode->LostConnectionToNode(aIntroduction.mName);
+
+    auto state = mState.Lock();
+    state->mPendingMessages.Remove(aIntroduction.mName);
+    return;
+  }
+
+  auto channel = MakeUnique<IPC::Channel>(std::move(aIntroduction.mHandle),
+                                          aIntroduction.mMode, nullptr);
+  auto nodeChannel = MakeRefPtr<NodeChannel>(
+      aIntroduction.mName, std::move(channel), this, aIntroduction.mOtherPid);
+
+  {
+    auto state = mState.Lock();
+    bool isNew = false;
+    state->mPeers.LookupOrInsertWith(aIntroduction.mName, [&]() {
+      isNew = true;
+      return nodeChannel;
+    });
+    if (!isNew) {
+      // We got a duplicate introduction. This can happen during normal
+      // execution if both sides request an introduction at the same time. We
+      // can just ignore the second one, as they'll arrive in the same order in
+      // both processes.
+      nodeChannel->Close();
+      return;
+    }
+
+    // Deliver any pending messages, then remove the entry from our table. We do
+    // this while `mState` is still held to ensure that these messages are
+    // all sent before another thread can observe the newly created channel.
+    // As the channel hasn't been `Connect()`-ed yet, this will only queue the
+    // messages up to be sent, so is OK to do with the mutex held.  These
+    // messages will be processed to be sent during `Start()` below, which is
+    // performed outside of the lock.
+    if (auto pending = state->mPendingMessages.Lookup(aIntroduction.mName)) {
+      while (!pending->IsEmpty()) {
+        nodeChannel->SendEventMessage(pending->Pop());
+      }
+      pending.Remove();
+    }
+  }
+
+  // NodeChannel::Start must be called with the lock not held, as it may lead to
+  // callbacks being made into `OnChannelError` or `OnMessageReceived`, which
+  // will attempt to re-acquire our lock.
+  nodeChannel->Start();
+}
+
+void NodeController::OnRequestIntroduction(const NodeName& aFromNode,
+                                           const NodeName& aName) {
+  AssertIOThread();
+  if (NS_WARN_IF(!IsBroker())) {
+    return;
+  }
+
+  RefPtr<NodeChannel> peerA = GetNodeChannel(aFromNode);
+  if (!peerA || aName == mojo::core::ports::kInvalidNodeName) {
+    NODECONTROLLER_WARNING("Invalid OnRequestIntroduction message from node %s",
+                           ToString(aFromNode).c_str());
+    DropPeer(aFromNode);
+    return;
+  }
+
+  RefPtr<NodeChannel> peerB = GetNodeChannel(aName);
+  IPC::Channel::ChannelHandle handleA, handleB;
+  if (!peerB || !IPC::Channel::CreateRawPipe(&handleA, &handleB)) {
+    NODECONTROLLER_WARNING(
+        "Rejecting introduction request from '%s' for unknown peer '%s'",
+        ToString(aFromNode).c_str(), ToString(aName).c_str());
+
+    // We don't know this peer, or ran into issues creating the descriptor! Send
+    // an invalid introduction to content to clean up any pending outbound
+    // messages.
+    NodeChannel::Introduction intro{aName, nullptr, IPC::Channel::MODE_SERVER,
+                                    peerA->OtherPid(), base::kInvalidProcessId};
+    peerA->Introduce(std::move(intro));
+    return;
+  }
+
+  NodeChannel::Introduction introA{aName, std::move(handleA),
+                                   IPC::Channel::MODE_SERVER, peerA->OtherPid(),
+                                   peerB->OtherPid()};
+  NodeChannel::Introduction introB{aFromNode, std::move(handleB),
+                                   IPC::Channel::MODE_CLIENT, peerB->OtherPid(),
+                                   peerA->OtherPid()};
+  peerA->Introduce(std::move(introA));
+  peerB->Introduce(std::move(introB));
+}
+
+void NodeController::OnAcceptInvite(const NodeName& aFromNode,
+                                    const NodeName& aRealName,
+                                    const PortName& aInitialPort) {
+  AssertIOThread();
+  if (!IsBroker()) {
+    NODECONTROLLER_WARNING("Ignoring AcceptInvite message as non-broker");
+    return;
+  }
+
+  if (aRealName == mojo::core::ports::kInvalidNodeName ||
+      aInitialPort == mojo::core::ports::kInvalidPortName) {
+    NODECONTROLLER_WARNING("Invalid name in AcceptInvite message");
+    DropPeer(aFromNode);
+    return;
+  }
+
+  bool inserted = false;
+  Invite invite;
+  {
+    auto state = mState.Lock();
+    MOZ_ASSERT(state->mPendingMessages.IsEmpty(),
+               "Shouldn't have pending messages in broker");
+
+    // Try to remove the source node from our invites list and insert it into
+    // our peers map under the new name.
+    if (state->mInvites.Remove(aFromNode, &invite)) {
+      MOZ_ASSERT(invite.mChannel && invite.mToMerge.is_valid());
+      state->mPeers.LookupOrInsertWith(aRealName, [&]() {
+        inserted = true;
+        return invite.mChannel;
+      });
+    }
+  }
+  if (!inserted) {
+    NODECONTROLLER_WARNING("Invalid AcceptInvite message from node %s",
+                           ToString(aFromNode).c_str());
+    DropPeer(aFromNode);
+    return;
+  }
+
+  // Update the name of the node. This field is only accessed from the IO
+  // thread, so it's safe to update it without a lock held.
+  invite.mChannel->SetName(aRealName);
+
+  // Start the port merge to allow our existing initial port to begin
+  // communicating with the remote port.
+  PORTS_ALWAYS_OK(mNode->MergePorts(invite.mToMerge, aRealName, aInitialPort));
+}
+
+void NodeController::OnChannelError(const NodeName& aFromNode) {
+  AssertIOThread();
+  DropPeer(aFromNode);
+}
+
+static mojo::core::ports::NodeName RandomNodeName() {
+  return {RandomUint64OrDie(), RandomUint64OrDie()};
+}
+
+std::tuple<ScopedPort, RefPtr<NodeChannel>> NodeController::InviteChildProcess(
+    UniquePtr<IPC::Channel> aChannel) {
+  MOZ_ASSERT(IsBroker());
+  AssertIOThread();
+
+  // Create the peer with a randomly generated name, and store it in `mInvites`.
+  // This channel and name will be used for communication with the node until it
+  // sends us its' real name in an `AcceptInvite` message.
+  auto ports = CreatePortPair();
+  auto inviteName = RandomNodeName();
+  auto nodeChannel =
+      MakeRefPtr<NodeChannel>(inviteName, std::move(aChannel), this);
+  {
+    auto state = mState.Lock();
+    MOZ_DIAGNOSTIC_ASSERT(!state->mPeers.Contains(inviteName),
+                          "UUID conflict?");
+    MOZ_DIAGNOSTIC_ASSERT(!state->mInvites.Contains(inviteName),
+                          "UUID conflict?");
+    state->mInvites.InsertOrUpdate(inviteName,
+                                   Invite{nodeChannel, ports.second.Release()});
+  }
+
+  nodeChannel->Start(/* aCallConnect */ false);
+  return std::tuple{std::move(ports.first), std::move(nodeChannel)};
+}
+
+void NodeController::InitBrokerProcess() {
+  AssertIOThread();
+  MOZ_ASSERT(!gNodeController);
+  gNodeController = new NodeController(kBrokerNodeName);
+}
+
+ScopedPort NodeController::InitChildProcess(UniquePtr<IPC::Channel> aChannel,
+                                            int32_t aParentPid) {
+  AssertIOThread();
+  MOZ_ASSERT(!gNodeController);
+
+  auto nodeName = RandomNodeName();
+  gNodeController = new NodeController(nodeName);
+
+  auto ports = gNodeController->CreatePortPair();
+  PortRef toMerge = ports.second.Release();
+
+  auto nodeChannel = MakeRefPtr<NodeChannel>(
+      kBrokerNodeName, std::move(aChannel), gNodeController, aParentPid);
+  {
+    auto state = gNodeController->mState.Lock();
+    MOZ_DIAGNOSTIC_ASSERT(!state->mPeers.Contains(kBrokerNodeName));
+    state->mPeers.InsertOrUpdate(kBrokerNodeName, nodeChannel);
+    MOZ_DIAGNOSTIC_ASSERT(!state->mPendingMerges.Contains(kBrokerNodeName));
+    state->mPendingMerges.LookupOrInsert(kBrokerNodeName)
+        .AppendElement(toMerge);
+  }
+
+  nodeChannel->Start(/* aCallConnect */ true);
+  nodeChannel->AcceptInvite(nodeName, toMerge.name());
+  return std::move(ports.first);
+}
+
+void NodeController::CleanUp() {
+  AssertIOThread();
+  MOZ_ASSERT(gNodeController);
+
+  RefPtr<NodeController> nodeController = gNodeController;
+  gNodeController = nullptr;
+
+  // Collect all objects from our state which need to be cleaned up.
+  nsTArray<NodeName> lostConnections;
+  nsTArray<RefPtr<NodeChannel>> channelsToClose;
+  nsTArray<PortRef> portsToClose;
+  {
+    auto state = nodeController->mState.Lock();
+    for (const auto& chan : state->mPeers) {
+      lostConnections.AppendElement(chan.GetKey());
+      channelsToClose.AppendElement(chan.GetData());
+    }
+    for (const auto& invite : state->mInvites.Values()) {
+      channelsToClose.AppendElement(invite.mChannel);
+      portsToClose.AppendElement(invite.mToMerge);
+    }
+    for (const auto& pendingPorts : state->mPendingMerges.Values()) {
+      portsToClose.AppendElements(pendingPorts);
+    }
+    state->mPeers.Clear();
+    state->mPendingMessages.Clear();
+    state->mInvites.Clear();
+    state->mPendingMerges.Clear();
+  }
+  for (auto& nodeChannel : channelsToClose) {
+    nodeChannel->Close();
+  }
+  for (auto& port : portsToClose) {
+    nodeController->mNode->ClosePort(port);
+  }
+  for (auto& name : lostConnections) {
+    nodeController->mNode->LostConnectionToNode(name);
+  }
+}
+
+#undef NODECONTROLLER_LOG
+#undef NODECONTROLLER_WARNING
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/NodeController.h b/ipc/glue/NodeController.h
new file mode 100644
index 0000000000..4b0d305b72
--- /dev/null
+++ b/ipc/glue/NodeController.h
@@ -0,0 +1,173 @@
+/* -*- 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_ipc_NodeController_h
+#define mozilla_ipc_NodeController_h
+
+#include "mojo/core/ports/event.h"
+#include "mojo/core/ports/name.h"
+#include "mojo/core/ports/node.h"
+#include "mojo/core/ports/node_delegate.h"
+#include "chrome/common/ipc_message.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "nsTHashMap.h"
+#include "mozilla/Queue.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/ipc/NodeChannel.h"
+
+namespace mozilla::ipc {
+
+class NodeController final : public mojo::core::ports::NodeDelegate,
+                             public NodeChannel::Listener {
+  using NodeName = mojo::core::ports::NodeName;
+  using PortName = mojo::core::ports::PortName;
+  using PortRef = mojo::core::ports::PortRef;
+  using Event = mojo::core::ports::Event;
+  using Node = mojo::core::ports::Node;
+  using UserData = mojo::core::ports::UserData;
+  using PortStatus = mojo::core::ports::PortStatus;
+  using UserMessageEvent = mojo::core::ports::UserMessageEvent;
+  using UserMessage = mojo::core::ports::UserMessage;
+
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(NodeController, override)
+
+  // Return the global singleton instance. The returned value is only valid
+  // while the IO thread is alive.
+  static NodeController* GetSingleton();
+
+  class PortObserver : public UserData {
+   public:
+    virtual void OnPortStatusChanged() = 0;
+
+   protected:
+    ~PortObserver() override = default;
+  };
+
+  // NOTE: For now there will always be a single broker process, and all
+  // processes in the graph need to be able to talk to it (the parent process).
+  // Give it a fixed node name for now to simplify things.
+  //
+  // If we ever decide to have multiple node networks intercommunicating (e.g.
+  // multiple instances or background services), we may need to change this.
+  static constexpr NodeName kBrokerNodeName{0x1, 0x1};
+
+  bool IsBroker() const { return mName == kBrokerNodeName; }
+
+  // Mint a new connected pair of ports within the current process.
+  std::pair<ScopedPort, ScopedPort> CreatePortPair();
+
+  // Get a reference to the port with the given name. Returns an invalid
+  // `PortRef` if the name wasn't found.
+  PortRef GetPort(const PortName& aName);
+
+  // Set the observer for the given port. This observer will be notified when
+  // the status of the port changes.
+  void SetPortObserver(const PortRef& aPort, PortObserver* aObserver);
+
+  // See `mojo::core::ports::Node::GetStatus`
+  Maybe<PortStatus> GetStatus(const PortRef& aPort);
+
+  // See `mojo::core::ports::Node::ClosePort`
+  void ClosePort(const PortRef& aPort);
+
+  // Send a message to the the port's connected peer.
+  bool SendUserMessage(const PortRef& aPort, UniquePtr<IPC::Message> aMessage);
+
+  // Get the next message from the port's message queue.
+  // Will set `*aMessage` to the found message, or `nullptr`.
+  // Returns `false` and sets `*aMessage` to `nullptr` if no further messages
+  // will be delivered to this port as its peer has been closed.
+  bool GetMessage(const PortRef& aPort, UniquePtr<IPC::Message>* aMessage);
+
+  // Called in the broker process from GeckoChildProcessHost to introduce a new
+  // child process into the network. Returns a `PortRef` which can be used to
+  // communicate with the `PortRef` returned from `InitChildProcess`, and a
+  // reference to the `NodeChannel` created for the new process. The port can
+  // immediately have messages sent to it.
+  std::tuple<ScopedPort, RefPtr<NodeChannel>> InviteChildProcess(
+      UniquePtr<IPC::Channel> aChannel);
+
+  // Called as the IO thread is started in the parent process.
+  static void InitBrokerProcess();
+
+  // Called as the IO thread is started in a child process.
+  static ScopedPort InitChildProcess(UniquePtr<IPC::Channel> aChannel,
+                                     int32_t aParentPid = -1);
+
+  // Called when the IO thread is torn down.
+  static void CleanUp();
+
+ private:
+  explicit NodeController(const NodeName& aName);
+  ~NodeController();
+
+  UniquePtr<IPC::Message> SerializeEventMessage(
+      UniquePtr<Event> aEvent, const NodeName* aRelayTarget = nullptr,
+      uint32_t aType = EVENT_MESSAGE_TYPE);
+  UniquePtr<Event> DeserializeEventMessage(UniquePtr<IPC::Message> aMessage,
+                                           NodeName* aRelayTarget = nullptr);
+
+  // Get the `NodeChannel` for the named node.
+  already_AddRefed<NodeChannel> GetNodeChannel(const NodeName& aName);
+
+  // Stop communicating with this peer. Must be called on the IO thread.
+  void DropPeer(NodeName aNodeName);
+
+  // Message Handlers
+  void OnEventMessage(const NodeName& aFromNode,
+                      UniquePtr<IPC::Message> aMessage) override;
+  void OnBroadcast(const NodeName& aFromNode,
+                   UniquePtr<IPC::Message> aMessage) override;
+  void OnIntroduce(const NodeName& aFromNode,
+                   NodeChannel::Introduction aIntroduction) override;
+  void OnRequestIntroduction(const NodeName& aFromNode,
+                             const NodeName& aName) override;
+  void OnAcceptInvite(const NodeName& aFromNode, const NodeName& aRealName,
+                      const PortName& aInitialPort) override;
+  void OnChannelError(const NodeName& aFromNode) override;
+
+  // NodeDelegate Implementation
+  void ForwardEvent(const NodeName& aNode, UniquePtr<Event> aEvent) override;
+  void BroadcastEvent(UniquePtr<Event> aEvent) override;
+  void PortStatusChanged(const PortRef& aPortRef) override;
+
+  const NodeName mName;
+  const UniquePtr<Node> mNode;
+
+  template <class T>
+  using NodeMap = nsTHashMap<NodeNameHashKey, T>;
+
+  struct Invite {
+    // The channel which is being invited. This will have a temporary name until
+    // the invite is completed.
+    RefPtr<NodeChannel> mChannel;
+    // The port which will be merged with the port information from the new
+    // child process when recieved.
+    PortRef mToMerge;
+  };
+
+  struct State {
+    // Channels for connecting to all known peers.
+    NodeMap<RefPtr<NodeChannel>> mPeers;
+
+    // Messages which are queued for peers which we been introduced to yet.
+    NodeMap<Queue<UniquePtr<IPC::Message>, 64>> mPendingMessages;
+
+    // Connections for peers being invited to the network.
+    NodeMap<Invite> mInvites;
+
+    // Ports which are waiting to be merged by a particular peer node.
+    NodeMap<nsTArray<PortRef>> mPendingMerges;
+  };
+
+  DataMutex<State> mState{"NodeController::mState"};
+};
+
+}  // namespace mozilla::ipc
+
+#endif
diff --git a/ipc/glue/PBackground.ipdl b/ipc/glue/PBackground.ipdl
new file mode 100644
index 0000000000..b242bd13ea
--- /dev/null
+++ b/ipc/glue/PBackground.ipdl
@@ -0,0 +1,330 @@
+/* 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 PBackgroundDataBridge;
+include protocol PBackgroundIDBFactory;
+include protocol PBackgroundIndexedDBUtils;
+include protocol PBackgroundSDBConnection;
+include protocol PBackgroundLSDatabase;
+include protocol PBackgroundLSObserver;
+include protocol PBackgroundLSRequest;
+include protocol PBackgroundLSSimpleRequest;
+include protocol PBackgroundLocalStorageCache;
+include protocol PBackgroundSessionStorageManager;
+include protocol PBackgroundSessionStorageService;
+include protocol PBackgroundStorage;
+include protocol PBackgroundTest;
+include protocol PBroadcastChannel;
+include protocol PCache;
+include protocol PCacheStorage;
+include protocol PCacheStreamControl;
+include protocol PClientManager;
+include protocol PEndpointForReport;
+include protocol PFileSystemManager;
+include protocol PFileSystemRequest;
+include protocol PGamepadEventChannel;
+include protocol PGamepadTestChannel;
+include protocol PHttpBackgroundChannel;
+include protocol PIPCClientCerts;
+include protocol PIdleScheduler;
+include protocol PMediaTransport;
+include protocol PRemoteWorker;
+include protocol PRemoteWorkerController;
+include protocol PRemoteWorkerService;
+include protocol PSharedWorker;
+include protocol PTemporaryIPCBlob;
+include protocol PFileCreator;
+include protocol PMessagePort;
+include protocol PCameras;
+include protocol PLockManager;
+include protocol PMIDIManager;
+include protocol PMIDIPort;
+include protocol PQuota;
+include protocol PSelectTLSClientAuthCert;
+include protocol PServiceWorker;
+include protocol PServiceWorkerContainer;
+include protocol PServiceWorkerManager;
+include protocol PServiceWorkerRegistration;
+include protocol PWebAuthnTransaction;
+include protocol PUDPSocket;
+include protocol PVerifySSLServerCert;
+include protocol PVsync;
+include protocol PRemoteDecoderManager;
+include protocol PWebSocketConnection;
+include protocol PWebTransport;
+include protocol PFetch;
+
+include ClientIPCTypes;
+include DOMTypes;
+include IPCBlob;
+include IPCServiceWorkerDescriptor;
+include IPCServiceWorkerRegistrationDescriptor;
+include PBackgroundLSSharedTypes;
+include PBackgroundSharedTypes;
+include PBackgroundIDBSharedTypes;
+include PFileSystemParams;
+include ProtocolTypes;
+include PSMIPCTypes;
+include RemoteWorkerTypes;
+include MIDITypes;
+
+include "mozilla/dom/cache/IPCUtils.h";
+include "mozilla/dom/quota/SerializationHelpers.h";
+include "mozilla/dom/PermissionMessageUtils.h";
+include "mozilla/layers/LayersMessageUtils.h";
+
+using mozilla::dom::cache::Namespace
+  from "mozilla/dom/cache/Types.h";
+
+using class mozilla::dom::SSCacheCopy from "mozilla/dom/PBackgroundSessionStorageCache.h";
+
+using mozilla::RemoteDecodeIn from "mozilla/RemoteDecoderManagerChild.h";
+
+namespace mozilla {
+namespace ipc {
+
+[NeedsOtherPid, ChildImpl=virtual, ParentImpl=virtual]
+sync protocol PBackground
+{
+  manages PBackgroundDataBridge;
+  manages PBackgroundIDBFactory;
+  manages PBackgroundIndexedDBUtils;
+  manages PBackgroundSDBConnection;
+  manages PBackgroundLSDatabase;
+  manages PBackgroundLSObserver;
+  manages PBackgroundLSRequest;
+  manages PBackgroundLSSimpleRequest;
+  manages PBackgroundLocalStorageCache;
+  manages PBackgroundSessionStorageManager;
+  manages PBackgroundSessionStorageService;
+  manages PBackgroundStorage;
+  manages PBackgroundTest;
+  manages PBroadcastChannel;
+  manages PCache;
+  manages PCacheStorage;
+  manages PCacheStreamControl;
+  manages PClientManager;
+  manages PEndpointForReport;
+  manages PFileSystemRequest;
+  manages PGamepadEventChannel;
+  manages PGamepadTestChannel;
+  manages PHttpBackgroundChannel;
+  manages PIPCClientCerts;
+  manages PIdleScheduler;
+  manages PLockManager;
+  manages PMediaTransport;
+  manages PRemoteWorker;
+  manages PRemoteWorkerController;
+  manages PRemoteWorkerService;
+  manages PSharedWorker;
+  manages PTemporaryIPCBlob;
+  manages PFileCreator;
+  manages PMessagePort;
+  manages PCameras;
+  manages PQuota;
+  manages PSelectTLSClientAuthCert;
+  manages PServiceWorker;
+  manages PServiceWorkerContainer;
+  manages PServiceWorkerManager;
+  manages PServiceWorkerRegistration;
+  manages PWebAuthnTransaction;
+  manages PWebSocketConnection;
+  manages PUDPSocket;
+  manages PVerifySSLServerCert;
+  manages PVsync;
+  manages PFetch;
+
+parent:
+  // Only called at startup during mochitests to check the basic infrastructure.
+  async PBackgroundTest(nsCString testArg);
+
+  async PBackgroundDataBridge(uint64_t channelID);
+
+  async PBackgroundIDBFactory(LoggingInfo loggingInfo);
+
+  async PBackgroundIndexedDBUtils();
+
+  // Use only for testing!
+  async FlushPendingFileDeletions();
+
+  async PBackgroundSDBConnection(PersistenceType persistenceType,
+                                 PrincipalInfo principalInfo);
+
+  async PBackgroundLSDatabase(PrincipalInfo principalInfo,
+                              uint32_t privateBrowsingId,
+                              uint64_t datastoreId);
+
+  async PBackgroundLSObserver(uint64_t observerId);
+
+  /**
+   * Issue an asynchronous request that will be used in a synchronous fashion
+   * through complex machinations described in `PBackgroundLSRequest.ipdl` and
+   * `LSObject.h`.
+   */
+  async PBackgroundLSRequest(LSRequestParams params);
+
+  /**
+   * Issues a simple, non-cancelable asynchronous request that's used in an
+   * asynchronous fashion by callers.  (LSRequest is not simple because it used
+   * in a synchronous fashion which leads to complexities regarding cancelation,
+   * see `PBackgroundLSRequest.ipdl` for details.)
+   */
+  async PBackgroundLSSimpleRequest(LSSimpleRequestParams params);
+
+  async PBackgroundLocalStorageCache(PrincipalInfo principalInfo,
+                                     nsCString originKey,
+                                     uint32_t privateBrowsingId);
+
+  async PBackgroundSessionStorageManager(uint64_t aTopContextId);
+
+  async PBackgroundSessionStorageService();
+
+  async PBackgroundStorage(nsString profilePath, uint32_t privateBrowsingId);
+
+  /**
+   * Finish the setup of a new PFileSystemManager top level protocol.
+   */
+  async CreateFileSystemManagerParent(
+      PrincipalInfo principalInfo,
+      Endpoint<PFileSystemManagerParent> aParentEndpoint)
+      returns(nsresult rv);
+
+  /**
+   * Finish the setup of a new PWebTransport top level protocol.
+   */
+  async CreateWebTransportParent(
+      nsString aURL,
+      nullable nsIPrincipal aPrincipal,
+      IPCClientInfo?  aClientInfo,
+      bool aDedicated,
+      bool aRequireUnreliable,
+      uint32_t aCongestionControl,
+      /* Sequence<WebTransportHash>* aServerCertHashes, */
+      Endpoint<PWebTransportParent> aParentEndpoint)
+      returns(nsresult rv, uint8_t aReliability); // Actually WebTransportReliabityMode enum
+
+  async PVsync();
+
+  async PCameras();
+
+  async PUDPSocket(PrincipalInfo? pInfo, nsCString filter);
+  async PBroadcastChannel(PrincipalInfo pInfo, nsCString origin, nsString channel);
+
+  async PServiceWorkerManager();
+
+  async ShutdownServiceWorkerRegistrar();
+
+  async PCacheStorage(Namespace aNamespace, PrincipalInfo aPrincipalInfo);
+
+  async PMessagePort(nsID uuid, nsID destinationUuid, uint32_t sequenceId);
+
+  async MessagePortForceClose(nsID uuid, nsID destinationUuid, uint32_t sequenceId);
+
+  async PQuota();
+
+  async ShutdownQuotaManager();
+
+  async ShutdownBackgroundSessionStorageManagers();
+
+  async PropagateBackgroundSessionStorageManager(uint64_t currentTopContextId, uint64_t targetTopContextId);
+
+  async RemoveBackgroundSessionStorageManager(uint64_t topContextId);
+
+  async GetSessionStorageManagerData(
+      uint64_t aTopContextId, uint32_t aSizeLimit, bool aCancelSessionStoreTimer)
+      returns(SSCacheCopy[] aCacheCopy);
+
+  async LoadSessionStorageManagerData(uint64_t aTopContextId, SSCacheCopy[] aOriginCacheCopy);
+
+  async PFileSystemRequest(FileSystemParams params);
+
+  async PGamepadEventChannel();
+
+  async PGamepadTestChannel();
+
+  async PHttpBackgroundChannel(uint64_t channelId);
+
+  async PWebAuthnTransaction();
+
+  async PSharedWorker(RemoteWorkerData data,
+                      uint64_t windowID,
+                      MessagePortIdentifier portIdentifier);
+
+  async PTemporaryIPCBlob();
+
+  async PFileCreator(nsString aFullPath, nsString aType, nsString aName,
+                     int64_t? lastModified, bool aExistenceCheck,
+                     bool aIsFromNsIFile);
+
+  async PClientManager();
+
+  async CreateMIDIManager(Endpoint<PMIDIManagerParent> aEndpoint);
+  async CreateMIDIPort(Endpoint<PMIDIPortParent> aEndpoint,
+                       MIDIPortInfo portInfo, bool sysexEnabled);
+  async HasMIDIDevice() returns (bool hasDevice);
+
+  // This method is used to propagate storage activities from the child actor
+  // to the parent actor. See StorageActivityService.
+  async StorageActivity(PrincipalInfo principalInfo);
+
+  async PServiceWorker(IPCServiceWorkerDescriptor aDescriptor);
+
+  async PRemoteWorkerController(RemoteWorkerData aData);
+
+  async PRemoteWorkerService();
+
+  async PServiceWorkerContainer();
+
+  async PServiceWorkerRegistration(IPCServiceWorkerRegistrationDescriptor aDescriptor);
+
+  async PEndpointForReport(nsString aGroupName, PrincipalInfo aPrincipalInfo);
+
+  async RemoveEndpoint(nsString aGroupName, nsCString aEndpointURL,
+                       PrincipalInfo aPrincipalInfo);
+
+  async PIdleScheduler();
+
+  async PMediaTransport();
+
+  async PSelectTLSClientAuthCert(nsCString aHostName,
+                                 OriginAttributes aOriginAttributes,
+                                 int32_t aPort,
+                                 uint32_t aProviderFlags,
+                                 uint32_t aProviderTlsFlags,
+                                 ByteArray aServerCertBytes,
+                                 ByteArray[] aCANames);
+
+  async PVerifySSLServerCert(ByteArray[] aPeerCertChain,
+                             nsCString aHostName,
+                             int32_t aPort,
+                             OriginAttributes aOriginAttributes,
+                             ByteArray? aStapledOCSPResponse,
+                             ByteArray? aSctsFromTLSExtension,
+                             DelegatedCredentialInfoArg? aDcInfo,
+                             uint32_t aProviderFlags,
+                             uint32_t aCertVerifierFlags);
+
+  async EnsureRDDProcessAndCreateBridge()
+      returns (nsresult rv, Endpoint<PRemoteDecoderManagerChild> aEndpoint);
+
+  async EnsureUtilityProcessAndCreateBridge(RemoteDecodeIn aLocation)
+      returns (nsresult rv, Endpoint<PRemoteDecoderManagerChild> aEndpoint);
+
+  async PWebSocketConnection(uint32_t aListenerId);
+
+  async PLockManager(ContentPrincipalInfo aPrincipalInfo, nsID aClientId);
+
+  async PIPCClientCerts();
+
+  async PFetch();
+
+child:
+  async PCache();
+  async PCacheStreamControl();
+
+  async PRemoteWorker(RemoteWorkerData data);
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/PBackgroundSharedTypes.ipdlh b/ipc/glue/PBackgroundSharedTypes.ipdlh
new file mode 100644
index 0000000000..9013b36d94
--- /dev/null
+++ b/ipc/glue/PBackgroundSharedTypes.ipdlh
@@ -0,0 +1,73 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+using mozilla::OriginAttributes from "mozilla/ipc/BackgroundUtils.h";
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+
+namespace mozilla {
+namespace ipc {
+
+[Comparable] struct ContentSecurityPolicy
+{
+  nsString policy;
+  bool reportOnlyFlag;
+  bool deliveredViaMetaTagFlag;
+};
+
+[Comparable] struct ContentPrincipalInfo
+{
+  OriginAttributes attrs;
+
+  // Origin is not simply a part of the spec. Based on the scheme of the URI
+  // spec, we generate different kind of origins: for instance any file: URL
+  // shares the same origin, about: URLs have the full spec as origin and so
+  // on.
+  // Another important reason why we have this attribute is that
+  // ContentPrincipalInfo is used out of the main-thread. Having this value
+  // here allows us to retrive the origin without creating a full nsIPrincipal.
+  nsCString originNoSuffix;
+
+  nsCString spec;
+
+  nsCString? domain;
+
+  // Like originNoSuffix, baseDomain is used out of the main-thread.
+  nsCString baseDomain;
+};
+
+[Comparable] struct SystemPrincipalInfo
+{ };
+
+[Comparable] struct NullPrincipalInfo
+{
+  OriginAttributes attrs;
+  nsCString spec;
+};
+
+[Comparable] struct ExpandedPrincipalInfo
+{
+  OriginAttributes attrs;
+  PrincipalInfo[] allowlist;
+};
+
+[Comparable] union PrincipalInfo
+{
+  ContentPrincipalInfo;
+  SystemPrincipalInfo;
+  NullPrincipalInfo;
+  ExpandedPrincipalInfo;
+};
+
+[Comparable] struct CSPInfo
+{
+  ContentSecurityPolicy[] policyInfos;
+  PrincipalInfo requestPrincipalInfo;
+  nsCString selfURISpec;
+  nsString referrer;
+  uint64_t innerWindowID;
+  bool skipAllowInlineStyleCheck;
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/PBackgroundStarter.ipdl b/ipc/glue/PBackgroundStarter.ipdl
new file mode 100644
index 0000000000..c53f47cb75
--- /dev/null
+++ b/ipc/glue/PBackgroundStarter.ipdl
@@ -0,0 +1,18 @@
+/* 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 ipc {
+
+[NeedsOtherPid]
+async protocol PBackgroundStarter
+{
+parent:
+  async InitBackground(Endpoint<PBackgroundParent> aEndpoint);
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/PBackgroundTest.ipdl b/ipc/glue/PBackgroundTest.ipdl
new file mode 100644
index 0000000000..5027010994
--- /dev/null
+++ b/ipc/glue/PBackgroundTest.ipdl
@@ -0,0 +1,21 @@
+/* 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 ipc {
+
+// This is a very simple testing protocol that is only used during mochitests.
+[ManualDealloc, ChildImpl=virtual, ParentImpl=virtual]
+protocol PBackgroundTest
+{
+  manager PBackground;
+
+child:
+  async __delete__(nsCString testArg);
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/PIdleScheduler.ipdl b/ipc/glue/PIdleScheduler.ipdl
new file mode 100644
index 0000000000..1857c12eaf
--- /dev/null
+++ b/ipc/glue/PIdleScheduler.ipdl
@@ -0,0 +1,70 @@
+/* -*- 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 protocol PBackground;
+using mozilla::TimeDuration from "mozilla/TimeStamp.h";
+[MoveOnly] using base::SharedMemoryHandle from "base/shared_memory.h";
+namespace mozilla {
+namespace ipc {
+
+/**
+ * PIdleScheduler is the protocol for cross-process idle scheduling.
+ * Only child processes participate in the scheduling and parent process
+ * can run its idle tasks whenever it needs to.
+ *
+ * The scheduler keeps track of the following things.
+ * - Activity of the main thread of each child process. A process is active
+ *   when it is running tasks. Because of performance cross-process
+ *   counters in shared memory are used for the activity tracking. There is
+ *   one counter counting the activity state of all the processes and one
+ *   counter for each process. This way if a child process crashes, the global
+ *   counter can be updated by decrementing the per process counter from it.
+ * - Child processes running prioritized operation. Top level page loads is an
+ *   example of a prioritized operation. When such is ongoing, idle tasks are
+ *   less likely to run.
+ * - Idle requests. When a child process locally has idle tasks to run, it
+ *   requests idle time from the scheduler. Initially requests go to a wait list
+ *   and the scheduler runs and if there are free logical cores for the child
+ *   processes, idle time is given to the child process, and the process goes to
+ *   the idle list. Once idle time has been consumed or there are no tasks to
+ *   process, child process informs the scheduler and the process is moved back
+ *   to the default queue.
+ */
+async protocol PIdleScheduler
+{
+  manager PBackground;
+
+child:
+  async IdleTime(uint64_t id, TimeDuration budget);
+
+parent:
+  async InitForIdleUse() returns (SharedMemoryHandle? state, uint32_t childId);
+  async RequestIdleTime(uint64_t id, TimeDuration budget);
+  async IdleTimeUsed(uint64_t id);
+
+  // Child can send explicit Schedule message to parent if it thinks parent process
+  // might be able to let some other process to use idle time.
+  async Schedule();
+
+  // Note, these two messages can be sent even before InitForIdleUse.
+  async RunningPrioritizedOperation();
+  async PrioritizedOperationDone();
+
+  // Ask if now would be a good time to GC
+  async RequestGC() returns (bool may_gc);
+
+  // Let the parent know when we start a GC without asking first.
+  async StartedGC();
+
+  // Called for ending any kind of GC.
+  async DoneGC();
+
+  // This message is never sent. Each PIdleScheduler actor will stay alive as long as
+  // its PBackground manager.
+  async __delete__();
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/PUtilityAudioDecoder.ipdl b/ipc/glue/PUtilityAudioDecoder.ipdl
new file mode 100644
index 0000000000..cedbd64052
--- /dev/null
+++ b/ipc/glue/PUtilityAudioDecoder.ipdl
@@ -0,0 +1,46 @@
+/* -*- 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 GraphicsMessages;
+include protocol PRemoteDecoderManager;
+include protocol PVideoBridge;
+
+using mozilla::dom::ContentParentId from "mozilla/dom/ipc/IdType.h";
+using mozilla::media::MediaCodecsSupported from "MediaCodecsSupport.h";
+using mozilla::RemoteDecodeIn from "mozilla/RemoteDecoderManagerChild.h";
+
+namespace mozilla {
+
+namespace ipc {
+
+// This protocol allows to run media audio decoding infrastructure on top
+// of the Utility process
+protocol PUtilityAudioDecoder
+{
+parent:
+  async NewContentRemoteDecoderManager(
+            Endpoint<PRemoteDecoderManagerParent> endpoint, ContentParentId parentId);
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  async InitVideoBridge(Endpoint<PVideoBridgeChild> endpoint,
+                        GfxVarUpdate[] updates,
+                        ContentDeviceData contentDeviceData);
+
+  async UpdateVar(GfxVarUpdate var);
+#endif
+
+child:
+  async UpdateMediaCodecsSupported(RemoteDecodeIn aLocation,
+                                   MediaCodecsSupported aSupported);
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  async CompleteCreatedVideoBridge();
+#endif
+
+};
+
+} // namespace ipc
+
+} // namespace mozilla
diff --git a/ipc/glue/PUtilityProcess.ipdl b/ipc/glue/PUtilityProcess.ipdl
new file mode 100644
index 0000000000..29452ed61e
--- /dev/null
+++ b/ipc/glue/PUtilityProcess.ipdl
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include MemoryReportTypes;
+include PrefsTypes;
+
+include protocol PProfiler;
+include protocol PUtilityAudioDecoder;
+include protocol PJSOracle;
+
+#if defined(XP_WIN)
+include protocol PWindowsUtils;
+#endif
+
+#if defined(MOZ_SANDBOX) && defined(MOZ_DEBUG) && defined(ENABLE_TESTS)
+include protocol PSandboxTesting;
+#endif
+
+include "mozilla/ipc/ByteBufUtils.h";
+
+using mozilla::dom::NativeThreadId from "mozilla/dom/NativeThreadId.h";
+
+// Telemetry
+using mozilla::Telemetry::HistogramAccumulation from "mozilla/TelemetryComms.h";
+using mozilla::Telemetry::KeyedHistogramAccumulation from "mozilla/TelemetryComms.h";
+using mozilla::Telemetry::ScalarAction from "mozilla/TelemetryComms.h";
+using mozilla::Telemetry::KeyedScalarAction from "mozilla/TelemetryComms.h";
+using mozilla::Telemetry::ChildEventData from "mozilla/TelemetryComms.h";
+using mozilla::Telemetry::DiscardedData from "mozilla/TelemetryComms.h";
+
+#if defined(XP_WIN)
+[MoveOnly] using mozilla::UntrustedModulesData from "mozilla/UntrustedModulesData.h";
+[MoveOnly] using mozilla::ModulePaths from "mozilla/UntrustedModulesData.h";
+[MoveOnly] using mozilla::ModulesMapResult from "mozilla/UntrustedModulesData.h";
+#endif  // defined(XP_WIN)
+
+namespace mozilla {
+
+namespace ipc {
+
+// This protocol allows the UI process to talk to the Utility process. There is
+// one instance of this protocol, with the UtilityProcessParent living on the main thread
+// of the main process and the UtilityProcessChild living on the main thread of the Utility
+// process.
+[NeedsOtherPid] protocol PUtilityProcess
+{
+parent:
+  async InitCrashReporter(NativeThreadId threadId);
+
+  async AddMemoryReport(MemoryReport aReport);
+
+  // Sent from time-to-time to limit the amount of telemetry vulnerable to loss
+  // Buffer contains bincoded Rust structs.
+  // https://firefox-source-docs.mozilla.org/toolkit/components/glean/dev/ipc.html
+  async FOGData(ByteBuf buf);
+
+#if defined(XP_WIN)
+  async GetModulesTrust(ModulePaths aModPaths, bool aRunAtNormalPriority)
+      returns (ModulesMapResult? modMapResult);
+#endif  // defined(XP_WIN)
+
+  // Messages for sending telemetry to parent process.
+  async AccumulateChildHistograms(HistogramAccumulation[] accumulations);
+  async AccumulateChildKeyedHistograms(KeyedHistogramAccumulation[] accumulations);
+  async UpdateChildScalars(ScalarAction[] actions);
+  async UpdateChildKeyedScalars(KeyedScalarAction[] actions);
+  async RecordChildEvents(ChildEventData[] events);
+  async RecordDiscardedData(DiscardedData data);
+
+  async InitCompleted();
+
+child:
+  async Init(FileDescriptor? sandboxBroker, bool canRecordReleaseTelemetry, bool aIsReadyForBackgroundProcessing);
+
+  async InitProfiler(Endpoint<PProfilerChild> endpoint);
+
+  async RequestMemoryReport(uint32_t generation,
+                            bool anonymize,
+                            bool minimizeMemoryUsage,
+                            FileDescriptor? DMDFile)
+      returns (uint32_t aGeneration);
+
+  async PreferenceUpdate(Pref pref);
+
+  // Tells the Utility process to flush any pending telemetry.
+  // Used in tests and ping assembly. Buffer contains bincoded Rust structs.
+  // https://firefox-source-docs.mozilla.org/toolkit/components/glean/dev/ipc.html
+  async FlushFOGData() returns (ByteBuf buf);
+
+  // Test-only method.
+  // Asks the Utility process to trigger test-only instrumentation.
+  // The unused returned value is to have a promise we can await.
+  async TestTriggerMetrics() returns (bool unused);
+
+  async TestTelemetryProbes();
+
+  async StartUtilityAudioDecoderService(Endpoint<PUtilityAudioDecoderParent> aEndpoint);
+
+  async StartJSOracleService(Endpoint<PJSOracleChild> aEndpoint);
+
+#if defined(XP_WIN)
+  async StartWindowsUtilsService(Endpoint<PWindowsUtilsChild> aEndpoint);
+
+  async GetUntrustedModulesData() returns (UntrustedModulesData? data);
+
+  /**
+  * This method is used to notify a child process to start
+  * processing module loading events in UntrustedModulesProcessor.
+  * This should be called when the parent process has gone idle.
+  */
+  async UnblockUntrustedModulesThread();
+#endif  // defined(XP_WIN)
+
+#if defined(MOZ_SANDBOX) && defined(MOZ_DEBUG) && defined(ENABLE_TESTS)
+  async InitSandboxTesting(Endpoint<PSandboxTestingChild> aEndpoint);
+#endif
+};
+
+} // namespace ipc
+
+} // namespace mozilla
diff --git a/ipc/glue/ProcessChild.cpp b/ipc/glue/ProcessChild.cpp
new file mode 100644
index 0000000000..7a8a74cc1e
--- /dev/null
+++ b/ipc/glue/ProcessChild.cpp
@@ -0,0 +1,137 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/ProcessChild.h"
+
+#include "Endpoint.h"
+#include "nsDebug.h"
+
+#ifdef XP_WIN
+#  include <stdlib.h>  // for _exit()
+#  include <synchapi.h>
+#else
+#  include <unistd.h>  // for _exit()
+#  include <time.h>
+#  include "base/eintr_wrapper.h"
+#  include "prenv.h"
+#endif
+
+#include "nsAppRunner.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ipc/CrashReporterClient.h"
+#include "mozilla/ipc/IOThreadChild.h"
+#include "mozilla/GeckoArgs.h"
+
+namespace mozilla {
+namespace ipc {
+
+ProcessChild* ProcessChild::gProcessChild;
+
+static Atomic<bool> sExpectingShutdown(false);
+
+ProcessChild::ProcessChild(ProcessId aParentPid, const nsID& aMessageChannelId)
+    : ChildProcess(new IOThreadChild()),
+      mUILoop(MessageLoop::current()),
+      mParentPid(aParentPid),
+      mMessageChannelId(aMessageChannelId) {
+  MOZ_ASSERT(mUILoop, "UILoop should be created by now");
+  MOZ_ASSERT(!gProcessChild, "should only be one ProcessChild");
+  gProcessChild = this;
+}
+
+/* static */
+void ProcessChild::AddPlatformBuildID(std::vector<std::string>& aExtraArgs) {
+  nsCString parentBuildID(mozilla::PlatformBuildID());
+  geckoargs::sParentBuildID.Put(parentBuildID.get(), aExtraArgs);
+}
+
+/* static */
+bool ProcessChild::InitPrefs(int aArgc, char* aArgv[]) {
+  Maybe<uint64_t> prefsHandle = Some(0);
+  Maybe<uint64_t> prefMapHandle = Some(0);
+  Maybe<uint64_t> prefsLen = geckoargs::sPrefsLen.Get(aArgc, aArgv);
+  Maybe<uint64_t> prefMapSize = geckoargs::sPrefMapSize.Get(aArgc, aArgv);
+
+  if (prefsLen.isNothing() || prefMapSize.isNothing()) {
+    return false;
+  }
+
+#ifdef XP_WIN
+  prefsHandle = geckoargs::sPrefsHandle.Get(aArgc, aArgv);
+  prefMapHandle = geckoargs::sPrefMapHandle.Get(aArgc, aArgv);
+
+  if (prefsHandle.isNothing() || prefMapHandle.isNothing()) {
+    return false;
+  }
+#endif
+
+  SharedPreferenceDeserializer deserializer;
+  return deserializer.DeserializeFromSharedMemory(*prefsHandle, *prefMapHandle,
+                                                  *prefsLen, *prefMapSize);
+}
+
+#ifdef ENABLE_TESTS
+// Allow tests to cause a synthetic delay/"hang" during child process
+// shutdown by setting environment variables.
+#  ifdef XP_UNIX
+static void ReallySleep(int aSeconds) {
+  struct ::timespec snooze = {aSeconds, 0};
+  HANDLE_EINTR(nanosleep(&snooze, &snooze));
+}
+#  elif defined(XP_WIN)
+static void ReallySleep(int aSeconds) { ::Sleep(aSeconds * 1000); }
+#  endif  // Unix/Win
+static void SleepIfEnv(const char* aName) {
+  if (auto* value = PR_GetEnv(aName)) {
+    ReallySleep(atoi(value));
+  }
+}
+#else  // not tests
+static void SleepIfEnv(const char* aName) {}
+#endif
+
+ProcessChild::~ProcessChild() {
+#ifdef NS_FREE_PERMANENT_DATA
+  // In this case, we won't early-exit and we'll wait indefinitely for
+  // child processes to terminate.  This sleep is late enough that, in
+  // content processes, it won't block parent process shutdown, so
+  // we'll get into late IPC shutdown with processes still running.
+  SleepIfEnv("MOZ_TEST_CHILD_EXIT_HANG");
+#endif
+  gProcessChild = nullptr;
+}
+
+/* static */
+void ProcessChild::NotifiedImpendingShutdown() {
+  sExpectingShutdown = true;
+  CrashReporter::AppendToCrashReportAnnotation(
+      CrashReporter::Annotation::IPCShutdownState,
+      "NotifiedImpendingShutdown"_ns);
+}
+
+/* static */
+bool ProcessChild::ExpectingShutdown() { return sExpectingShutdown; }
+
+/* static */
+void ProcessChild::QuickExit() {
+#ifndef NS_FREE_PERMANENT_DATA
+  // In this case, we're going to terminate the child process before
+  // we get to ~ProcessChild above (and terminate the parent process
+  // before the shutdown hook in ProcessWatcher).  Instead, blocking
+  // earlier will let us exercise ProcessWatcher's kill timer.
+  SleepIfEnv("MOZ_TEST_CHILD_EXIT_HANG");
+#endif
+  AppShutdown::DoImmediateExit();
+}
+
+UntypedEndpoint ProcessChild::TakeInitialEndpoint() {
+  return UntypedEndpoint{PrivateIPDLInterface{},
+                         child_thread()->TakeInitialPort(), mMessageChannelId,
+                         base::GetCurrentProcId(), mParentPid};
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProcessChild.h b/ipc/glue/ProcessChild.h
new file mode 100644
index 0000000000..29948a9127
--- /dev/null
+++ b/ipc/glue/ProcessChild.h
@@ -0,0 +1,75 @@
+/* -*- 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_ipc_ProcessChild_h
+#define mozilla_ipc_ProcessChild_h
+
+#include "Endpoint.h"
+#include "base/message_loop.h"
+#include "base/process.h"
+
+#include "chrome/common/child_process.h"
+
+#include "mozilla/ipc/ProcessUtils.h"
+
+// ProcessChild is the base class for all subprocesses of the main
+// browser process.  Its code runs on the thread that started in
+// main().
+
+namespace mozilla {
+namespace ipc {
+
+class ProcessChild : public ChildProcess {
+ protected:
+  typedef base::ProcessId ProcessId;
+
+ public:
+  explicit ProcessChild(ProcessId aParentPid, const nsID& aMessageChannelId);
+
+  ProcessChild(const ProcessChild&) = delete;
+  ProcessChild& operator=(const ProcessChild&) = delete;
+
+  virtual ~ProcessChild();
+
+  virtual bool Init(int aArgc, char* aArgv[]) = 0;
+
+  static void AddPlatformBuildID(std::vector<std::string>& aExtraArgs);
+
+  static bool InitPrefs(int aArgc, char* aArgv[]);
+
+  virtual void CleanUp() {}
+
+  static MessageLoop* message_loop() { return gProcessChild->mUILoop; }
+
+  static void NotifiedImpendingShutdown();
+
+  static bool ExpectingShutdown();
+
+  /**
+   * Exit *now*.  Do not shut down XPCOM, do not pass Go, do not run
+   * static destructors, do not collect $200.
+   */
+  static void QuickExit();
+
+ protected:
+  static ProcessChild* current() { return gProcessChild; }
+
+  ProcessId ParentPid() { return mParentPid; }
+
+  UntypedEndpoint TakeInitialEndpoint();
+
+ private:
+  static ProcessChild* gProcessChild;
+
+  MessageLoop* mUILoop;
+  ProcessId mParentPid;
+  nsID mMessageChannelId;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_ProcessChild_h
diff --git a/ipc/glue/ProcessUtils.h b/ipc/glue/ProcessUtils.h
new file mode 100644
index 0000000000..b0f146ef6d
--- /dev/null
+++ b/ipc/glue/ProcessUtils.h
@@ -0,0 +1,93 @@
+/* -*- 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_ipc_ProcessUtils_h
+#define mozilla_ipc_ProcessUtils_h
+
+#include <functional>
+#include <vector>
+
+#include "mozilla/ipc/FileDescriptor.h"
+#include "base/shared_memory.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Preferences.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+namespace ipc {
+
+class GeckoChildProcessHost;
+
+// You probably should call ContentChild::SetProcessName instead of calling
+// this directly.
+void SetThisProcessName(const char* aName);
+
+class SharedPreferenceSerializer final {
+ public:
+  explicit SharedPreferenceSerializer();
+  SharedPreferenceSerializer(SharedPreferenceSerializer&& aOther);
+  ~SharedPreferenceSerializer();
+
+  bool SerializeToSharedMemory(const GeckoProcessType aDestinationProcessType,
+                               const nsACString& aDestinationRemoteType);
+
+  size_t GetPrefMapSize() const { return mPrefMapSize; }
+  size_t GetPrefsLength() const { return mPrefsLength; }
+
+  const UniqueFileHandle& GetPrefsHandle() const { return mPrefsHandle; }
+
+  const UniqueFileHandle& GetPrefMapHandle() const { return mPrefMapHandle; }
+
+  void AddSharedPrefCmdLineArgs(GeckoChildProcessHost& procHost,
+                                std::vector<std::string>& aExtraOpts) const;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SharedPreferenceSerializer);
+  size_t mPrefMapSize;
+  size_t mPrefsLength;
+  UniqueFileHandle mPrefMapHandle;
+  UniqueFileHandle mPrefsHandle;
+};
+
+class SharedPreferenceDeserializer final {
+ public:
+  SharedPreferenceDeserializer();
+  ~SharedPreferenceDeserializer();
+
+  bool DeserializeFromSharedMemory(uint64_t aPrefsHandle,
+                                   uint64_t aPrefMapHandle, uint64_t aPrefsLen,
+                                   uint64_t aPrefMapSize);
+
+  const FileDescriptor& GetPrefMapHandle() const;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SharedPreferenceDeserializer);
+  Maybe<FileDescriptor> mPrefMapHandle;
+  Maybe<size_t> mPrefsLen;
+  Maybe<size_t> mPrefMapSize;
+  base::SharedMemory mShmem;
+};
+
+#ifdef ANDROID
+// Android doesn't use -prefsHandle or -prefMapHandle. It gets those FDs
+// another way.
+void SetPrefsFd(int aFd);
+void SetPrefMapFd(int aFd);
+#endif
+
+// Generate command line argument to spawn a child process. If the shared memory
+// is not properly initialized, this would be a no-op.
+void ExportSharedJSInit(GeckoChildProcessHost& procHost,
+                        std::vector<std::string>& aExtraOpts);
+
+// Initialize the content used by the JS engine during the initialization of a
+// JS::Runtime.
+bool ImportSharedJSInit(uint64_t aJsInitHandle, uint64_t aJsInitLen);
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_ProcessUtils_h
diff --git a/ipc/glue/ProcessUtils_bsd.cpp b/ipc/glue/ProcessUtils_bsd.cpp
new file mode 100644
index 0000000000..fa113f2e58
--- /dev/null
+++ b/ipc/glue/ProcessUtils_bsd.cpp
@@ -0,0 +1,27 @@
+/* -*- 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 "ProcessUtils.h"
+
+#include <pthread.h>
+
+#if !defined(OS_NETBSD)
+#  include <pthread_np.h>
+#endif
+
+namespace mozilla {
+namespace ipc {
+
+void SetThisProcessName(const char* aName) {
+#if defined(OS_NETBSD)
+  pthread_setname_np(pthread_self(), "%s", (void*)aName);
+#else
+  pthread_set_name_np(pthread_self(), aName);
+#endif
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProcessUtils_common.cpp b/ipc/glue/ProcessUtils_common.cpp
new file mode 100644
index 0000000000..69eb4bdf28
--- /dev/null
+++ b/ipc/glue/ProcessUtils_common.cpp
@@ -0,0 +1,275 @@
+/* -*- 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 "ProcessUtils.h"
+
+#include "mozilla/Preferences.h"
+#include "mozilla/GeckoArgs.h"
+#include "mozilla/dom/RemoteType.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "nsPrintfCString.h"
+
+#include "XPCSelfHostedShmem.h"
+
+namespace mozilla {
+namespace ipc {
+
+SharedPreferenceSerializer::SharedPreferenceSerializer()
+    : mPrefMapSize(0), mPrefsLength(0) {
+  MOZ_COUNT_CTOR(SharedPreferenceSerializer);
+}
+
+SharedPreferenceSerializer::~SharedPreferenceSerializer() {
+  MOZ_COUNT_DTOR(SharedPreferenceSerializer);
+}
+
+SharedPreferenceSerializer::SharedPreferenceSerializer(
+    SharedPreferenceSerializer&& aOther)
+    : mPrefMapSize(aOther.mPrefMapSize),
+      mPrefsLength(aOther.mPrefsLength),
+      mPrefMapHandle(std::move(aOther.mPrefMapHandle)),
+      mPrefsHandle(std::move(aOther.mPrefsHandle)) {
+  MOZ_COUNT_CTOR(SharedPreferenceSerializer);
+}
+
+bool SharedPreferenceSerializer::SerializeToSharedMemory(
+    const GeckoProcessType aDestinationProcessType,
+    const nsACString& aDestinationRemoteType) {
+  mPrefMapHandle =
+      Preferences::EnsureSnapshot(&mPrefMapSize).TakePlatformHandle();
+
+  bool destIsWebContent =
+      aDestinationProcessType == GeckoProcessType_Content &&
+      (StringBeginsWith(aDestinationRemoteType, WEB_REMOTE_TYPE) ||
+       StringBeginsWith(aDestinationRemoteType, PREALLOC_REMOTE_TYPE));
+
+  // Serialize the early prefs.
+  nsAutoCStringN<1024> prefs;
+  Preferences::SerializePreferences(prefs, destIsWebContent);
+  mPrefsLength = prefs.Length();
+
+  base::SharedMemory shm;
+  // Set up the shared memory.
+  if (!shm.Create(prefs.Length())) {
+    NS_ERROR("failed to create shared memory in the parent");
+    return false;
+  }
+  if (!shm.Map(prefs.Length())) {
+    NS_ERROR("failed to map shared memory in the parent");
+    return false;
+  }
+
+  // Copy the serialized prefs into the shared memory.
+  memcpy(static_cast<char*>(shm.memory()), prefs.get(), mPrefsLength);
+
+  mPrefsHandle = shm.TakeHandle();
+  return true;
+}
+
+void SharedPreferenceSerializer::AddSharedPrefCmdLineArgs(
+    mozilla::ipc::GeckoChildProcessHost& procHost,
+    std::vector<std::string>& aExtraOpts) const {
+#if defined(XP_WIN)
+  // Record the handle as to-be-shared, and pass it via a command flag. This
+  // works because Windows handles are system-wide.
+  procHost.AddHandleToShare(GetPrefsHandle().get());
+  procHost.AddHandleToShare(GetPrefMapHandle().get());
+  geckoargs::sPrefsHandle.Put((uintptr_t)(GetPrefsHandle().get()), aExtraOpts);
+  geckoargs::sPrefMapHandle.Put((uintptr_t)(GetPrefMapHandle().get()),
+                                aExtraOpts);
+#else
+  // In contrast, Unix fds are per-process. So remap the fd to a fixed one that
+  // will be used in the child.
+  // XXX: bug 1440207 is about improving how fixed fds are used.
+  //
+  // Note: on Android, AddFdToRemap() sets up the fd to be passed via a Parcel,
+  // and the fixed fd isn't used. However, we still need to mark it for
+  // remapping so it doesn't get closed in the child.
+  procHost.AddFdToRemap(GetPrefsHandle().get(), kPrefsFileDescriptor);
+  procHost.AddFdToRemap(GetPrefMapHandle().get(), kPrefMapFileDescriptor);
+#endif
+
+  // Pass the lengths via command line flags.
+  geckoargs::sPrefsLen.Put((uintptr_t)(GetPrefsLength()), aExtraOpts);
+  geckoargs::sPrefMapSize.Put((uintptr_t)(GetPrefMapSize()), aExtraOpts);
+}
+
+#ifdef ANDROID
+static int gPrefsFd = -1;
+static int gPrefMapFd = -1;
+
+void SetPrefsFd(int aFd) { gPrefsFd = aFd; }
+
+void SetPrefMapFd(int aFd) { gPrefMapFd = aFd; }
+#endif
+
+SharedPreferenceDeserializer::SharedPreferenceDeserializer() {
+  MOZ_COUNT_CTOR(SharedPreferenceDeserializer);
+}
+
+SharedPreferenceDeserializer::~SharedPreferenceDeserializer() {
+  MOZ_COUNT_DTOR(SharedPreferenceDeserializer);
+}
+
+bool SharedPreferenceDeserializer::DeserializeFromSharedMemory(
+    uint64_t aPrefsHandle, uint64_t aPrefMapHandle, uint64_t aPrefsLen,
+    uint64_t aPrefMapSize) {
+  Maybe<base::SharedMemoryHandle> prefsHandle;
+
+#ifdef XP_WIN
+  prefsHandle = Some(UniqueFileHandle(HANDLE((uintptr_t)(aPrefsHandle))));
+  if (!aPrefsHandle) {
+    return false;
+  }
+
+  FileDescriptor::UniquePlatformHandle handle(
+      HANDLE((uintptr_t)(aPrefMapHandle)));
+  if (!aPrefMapHandle) {
+    return false;
+  }
+
+  mPrefMapHandle.emplace(std::move(handle));
+#endif
+
+  mPrefsLen = Some((uintptr_t)(aPrefsLen));
+  if (!aPrefsLen) {
+    return false;
+  }
+
+  mPrefMapSize = Some((uintptr_t)(aPrefMapSize));
+  if (!aPrefMapSize) {
+    return false;
+  }
+
+#ifdef ANDROID
+  // Android is different; get the FD via gPrefsFd instead of a fixed fd.
+  MOZ_RELEASE_ASSERT(gPrefsFd != -1);
+  prefsHandle = Some(UniqueFileHandle(gPrefsFd));
+
+  mPrefMapHandle.emplace(UniqueFileHandle(gPrefMapFd));
+#elif XP_UNIX
+  prefsHandle = Some(UniqueFileHandle(kPrefsFileDescriptor));
+
+  mPrefMapHandle.emplace(UniqueFileHandle(kPrefMapFileDescriptor));
+#endif
+
+  if (prefsHandle.isNothing() || mPrefsLen.isNothing() ||
+      mPrefMapHandle.isNothing() || mPrefMapSize.isNothing()) {
+    return false;
+  }
+
+  // Init the shared-memory base preference mapping first, so that only changed
+  // preferences wind up in heap memory.
+  Preferences::InitSnapshot(mPrefMapHandle.ref(), *mPrefMapSize);
+
+  // Set up early prefs from the shared memory.
+  if (!mShmem.SetHandle(std::move(*prefsHandle), /* read_only */ true)) {
+    NS_ERROR("failed to open shared memory in the child");
+    return false;
+  }
+  if (!mShmem.Map(*mPrefsLen)) {
+    NS_ERROR("failed to map shared memory in the child");
+    return false;
+  }
+  Preferences::DeserializePreferences(static_cast<char*>(mShmem.memory()),
+                                      *mPrefsLen);
+
+  return true;
+}
+
+const FileDescriptor& SharedPreferenceDeserializer::GetPrefMapHandle() const {
+  MOZ_ASSERT(mPrefMapHandle.isSome());
+
+  return mPrefMapHandle.ref();
+}
+
+#ifdef XP_UNIX
+// On Unix, file descriptors are per-process. This value is used when mapping
+// a parent process handle to a content process handle.
+static const int kJSInitFileDescriptor = 11;
+#endif
+
+void ExportSharedJSInit(mozilla::ipc::GeckoChildProcessHost& procHost,
+                        std::vector<std::string>& aExtraOpts) {
+#ifdef ANDROID
+  // The code to support Android is added in a follow-up patch.
+  return;
+#else
+  auto& shmem = xpc::SelfHostedShmem::GetSingleton();
+  const mozilla::UniqueFileHandle& uniqHandle = shmem.Handle();
+  size_t len = shmem.Content().Length();
+
+  // If the file is not found or the content is empty, then we would start the
+  // content process without this optimization.
+  if (!uniqHandle || !len) {
+    return;
+  }
+
+  mozilla::detail::FileHandleType handle = uniqHandle.get();
+  // command line: [-jsInitHandle handle] -jsInitLen length
+#  if defined(XP_WIN)
+  // Record the handle as to-be-shared, and pass it via a command flag.
+  procHost.AddHandleToShare(HANDLE(handle));
+  geckoargs::sJsInitHandle.Put((uintptr_t)(HANDLE(handle)), aExtraOpts);
+#  else
+  // In contrast, Unix fds are per-process. So remap the fd to a fixed one that
+  // will be used in the child.
+  // XXX: bug 1440207 is about improving how fixed fds are used.
+  //
+  // Note: on Android, AddFdToRemap() sets up the fd to be passed via a Parcel,
+  // and the fixed fd isn't used. However, we still need to mark it for
+  // remapping so it doesn't get closed in the child.
+  procHost.AddFdToRemap(handle, kJSInitFileDescriptor);
+#  endif
+
+  // Pass the lengths via command line flags.
+  geckoargs::sJsInitLen.Put((uintptr_t)(len), aExtraOpts);
+#endif
+}
+
+bool ImportSharedJSInit(uint64_t aJsInitHandle, uint64_t aJsInitLen) {
+  // This is an optimization, and as such we can safely recover if the command
+  // line argument are not provided.
+  if (!aJsInitLen) {
+    return true;
+  }
+
+#ifdef XP_WIN
+  if (!aJsInitHandle) {
+    return true;
+  }
+#endif
+
+#ifdef XP_WIN
+  base::SharedMemoryHandle handle(HANDLE((uintptr_t)(aJsInitHandle)));
+  if (!aJsInitHandle) {
+    return false;
+  }
+#endif
+
+  size_t len = (uintptr_t)(aJsInitLen);
+  if (!aJsInitLen) {
+    return false;
+  }
+
+#ifdef XP_UNIX
+  auto handle = UniqueFileHandle(kJSInitFileDescriptor);
+#endif
+
+  // Initialize the shared memory with the file handle and size of the content
+  // of the self-hosted Xdr.
+  auto& shmem = xpc::SelfHostedShmem::GetSingleton();
+  if (!shmem.InitFromChild(std::move(handle), len)) {
+    NS_ERROR("failed to open shared memory in the child");
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProcessUtils_linux.cpp b/ipc/glue/ProcessUtils_linux.cpp
new file mode 100644
index 0000000000..da15745753
--- /dev/null
+++ b/ipc/glue/ProcessUtils_linux.cpp
@@ -0,0 +1,22 @@
+/* -*- 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 "ProcessUtils.h"
+
+#include "nsString.h"
+
+#include <sys/prctl.h>
+
+namespace mozilla {
+
+namespace ipc {
+
+void SetThisProcessName(const char* aName) {
+  prctl(PR_SET_NAME, (unsigned long)aName, 0uL, 0uL, 0uL);
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProcessUtils_mac.mm b/ipc/glue/ProcessUtils_mac.mm
new file mode 100644
index 0000000000..0f1d8ecbba
--- /dev/null
+++ b/ipc/glue/ProcessUtils_mac.mm
@@ -0,0 +1,109 @@
+/* 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 "ProcessUtils.h"
+
+#include "nsObjCExceptions.h"
+#include "nsCocoaUtils.h"
+#include "nsString.h"
+#include "mozilla/Sprintf.h"
+
+#define UNDOCUMENTED_SESSION_CONSTANT ((int)-2)
+
+namespace mozilla {
+namespace ipc {
+
+static void* sApplicationASN = NULL;
+static void* sApplicationInfoItem = NULL;
+
+void SetThisProcessName(const char* aProcessName) {
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
+  nsAutoreleasePool localPool;
+
+  if (!aProcessName || strcmp(aProcessName, "") == 0) {
+    return;
+  }
+
+  NSString* currentName =
+      [[[NSBundle mainBundle] localizedInfoDictionary] objectForKey:(NSString*)kCFBundleNameKey];
+
+  char formattedName[1024];
+  SprintfLiteral(formattedName, "%s %s", [currentName UTF8String], aProcessName);
+
+  aProcessName = formattedName;
+
+  // This function is based on Chrome/Webkit's and relies on potentially dangerous SPI.
+  typedef CFTypeRef (*LSGetASNType)();
+  typedef OSStatus (*LSSetInformationItemType)(int, CFTypeRef, CFStringRef, CFStringRef,
+                                               CFDictionaryRef*);
+
+  CFBundleRef launchServices = ::CFBundleGetBundleWithIdentifier(CFSTR("com.apple.LaunchServices"));
+  if (!launchServices) {
+    NS_WARNING("Failed to set process name: Could not open LaunchServices bundle");
+    return;
+  }
+
+  if (!sApplicationASN) {
+    sApplicationASN =
+        ::CFBundleGetFunctionPointerForName(launchServices, CFSTR("_LSGetCurrentApplicationASN"));
+    if (!sApplicationASN) {
+      NS_WARNING("Failed to set process name: Could not get function pointer "
+                 "for LaunchServices");
+      return;
+    }
+  }
+
+  LSGetASNType getASNFunc = reinterpret_cast<LSGetASNType>(sApplicationASN);
+
+  if (!sApplicationInfoItem) {
+    sApplicationInfoItem = ::CFBundleGetFunctionPointerForName(
+        launchServices, CFSTR("_LSSetApplicationInformationItem"));
+  }
+
+  LSSetInformationItemType setInformationItemFunc =
+      reinterpret_cast<LSSetInformationItemType>(sApplicationInfoItem);
+
+  void* displayNameKeyAddr =
+      ::CFBundleGetDataPointerForName(launchServices, CFSTR("_kLSDisplayNameKey"));
+
+  CFStringRef displayNameKey = nil;
+  if (displayNameKeyAddr) {
+    displayNameKey = reinterpret_cast<CFStringRef>(*(CFStringRef*)displayNameKeyAddr);
+  }
+
+  // We need this to ensure we have a connection to the Process Manager, not
+  // doing so will silently fail and process name wont be updated.
+  ProcessSerialNumber psn;
+  if (::GetCurrentProcess(&psn) != noErr) {
+    return;
+  }
+
+  CFTypeRef currentAsn = getASNFunc ? getASNFunc() : nullptr;
+
+  if (!getASNFunc || !setInformationItemFunc || !displayNameKey || !currentAsn) {
+    NS_WARNING("Failed to set process name: Accessing launchServices failed");
+    return;
+  }
+
+  CFStringRef processName = ::CFStringCreateWithCString(nil, aProcessName, kCFStringEncodingASCII);
+  if (!processName) {
+    NS_WARNING("Failed to set process name: Could not create CFStringRef");
+    return;
+  }
+
+  OSErr err =
+      setInformationItemFunc(UNDOCUMENTED_SESSION_CONSTANT, currentAsn, displayNameKey, processName,
+                             nil);  // Optional out param
+  ::CFRelease(processName);
+  if (err != noErr) {
+    NS_WARNING("Failed to set process name: LSSetInformationItemType err");
+    return;
+  }
+
+  return;
+  NS_OBJC_END_TRY_ABORT_BLOCK;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProcessUtils_none.cpp b/ipc/glue/ProcessUtils_none.cpp
new file mode 100644
index 0000000000..49566a0720
--- /dev/null
+++ b/ipc/glue/ProcessUtils_none.cpp
@@ -0,0 +1,15 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ProcessUtils.h"
+
+namespace mozilla {
+namespace ipc {
+
+void SetThisProcessName(const char* aString) { (void)aString; }
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProtocolMessageUtils.h b/ipc/glue/ProtocolMessageUtils.h
new file mode 100644
index 0000000000..48485596ea
--- /dev/null
+++ b/ipc/glue/ProtocolMessageUtils.h
@@ -0,0 +1,121 @@
+/* -*- 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 https://mozilla.org/MPL/2.0/. */
+
+#ifndef IPC_GLUE_PROTOCOLMESSAGEUTILS_H
+#define IPC_GLUE_PROTOCOLMESSAGEUTILS_H
+
+#include <stdint.h>
+#include <string>
+#include "base/string_util.h"
+#include "chrome/common/ipc_channel.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "ipc/EnumSerializer.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+
+class PickleIterator;
+
+namespace mozilla::ipc {
+class FileDescriptor;
+template <class PFooSide>
+class Endpoint;
+template <class PFooSide>
+class ManagedEndpoint;
+template <typename P>
+struct IPDLParamTraits;
+}  // namespace mozilla::ipc
+
+namespace IPC {
+
+class Message;
+class MessageReader;
+class MessageWriter;
+
+template <>
+struct ParamTraits<Channel::Mode>
+    : ContiguousEnumSerializerInclusive<Channel::Mode, Channel::MODE_SERVER,
+                                        Channel::MODE_CLIENT> {};
+
+template <>
+struct ParamTraits<IPCMessageStart>
+    : ContiguousEnumSerializer<IPCMessageStart, IPCMessageStart(0),
+                               LastMsgIndex> {};
+
+template <>
+struct ParamTraits<mozilla::ipc::ActorHandle> {
+  typedef mozilla::ipc::ActorHandle paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    IPC::WriteParam(aWriter, aParam.mId);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    int id;
+    if (IPC::ReadParam(aReader, &id)) {
+      aResult->mId = id;
+      return true;
+    }
+    return false;
+  }
+};
+
+template <>
+struct ParamTraits<mozilla::ipc::UntypedEndpoint> {
+  using paramType = mozilla::ipc::UntypedEndpoint;
+
+  static void Write(MessageWriter* aWriter, paramType&& aParam);
+
+  static bool Read(MessageReader* aReader, paramType* aResult);
+};
+
+template <class PFooSide>
+struct ParamTraits<mozilla::ipc::Endpoint<PFooSide>>
+    : ParamTraits<mozilla::ipc::UntypedEndpoint> {};
+
+}  // namespace IPC
+
+namespace mozilla::ipc {
+
+template <>
+struct IPDLParamTraits<UntypedManagedEndpoint> {
+  using paramType = UntypedManagedEndpoint;
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    paramType&& aParam);
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   paramType* aResult);
+};
+
+template <class PFooSide>
+struct IPDLParamTraits<ManagedEndpoint<PFooSide>> {
+  using paramType = ManagedEndpoint<PFooSide>;
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    paramType&& aParam) {
+    IPDLParamTraits<UntypedManagedEndpoint>::Write(aWriter, aActor,
+                                                   std::move(aParam));
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   paramType* aResult) {
+    return IPDLParamTraits<UntypedManagedEndpoint>::Read(aReader, aActor,
+                                                         aResult);
+  }
+};
+
+template <>
+struct IPDLParamTraits<FileDescriptor> {
+  typedef FileDescriptor paramType;
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const paramType& aParam);
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   paramType* aResult);
+};
+}  // namespace mozilla::ipc
+
+#endif  // IPC_GLUE_PROTOCOLMESSAGEUTILS_H
diff --git a/ipc/glue/ProtocolTypes.ipdlh b/ipc/glue/ProtocolTypes.ipdlh
new file mode 100644
index 0000000000..b1d5316731
--- /dev/null
+++ b/ipc/glue/ProtocolTypes.ipdlh
@@ -0,0 +1,21 @@
+/* -*- Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 8 -*- */
+/* vim: set sw=4 ts=8 et tw=80 ft=cpp : */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+using struct nsID
+  from "nsID.h";
+
+namespace mozilla {
+namespace ipc {
+
+struct ProtocolFdMapping
+{
+    uint32_t protocolId;
+    FileDescriptor fd;
+};
+
+}
+}
+
diff --git a/ipc/glue/ProtocolUtils.cpp b/ipc/glue/ProtocolUtils.cpp
new file mode 100644
index 0000000000..51fb4d7e56
--- /dev/null
+++ b/ipc/glue/ProtocolUtils.cpp
@@ -0,0 +1,835 @@
+/* -*- 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 "base/process_util.h"
+#include "base/task.h"
+
+#ifdef OS_POSIX
+#  include <errno.h>
+#endif
+#include <type_traits>
+
+#include "mozilla/IntegerPrintfMacros.h"
+
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+
+#include "mozilla/ipc/MessageChannel.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "mozilla/StaticMutex.h"
+#if defined(DEBUG) || defined(FUZZING)
+#  include "mozilla/Tokenizer.h"
+#endif
+#include "mozilla/Unused.h"
+#include "nsPrintfCString.h"
+
+#if defined(MOZ_SANDBOX) && defined(XP_WIN)
+#  include "mozilla/sandboxTarget.h"
+#endif
+
+#if defined(XP_WIN)
+#  include "aclapi.h"
+#  include "sddl.h"
+#endif
+
+#ifdef FUZZING_SNAPSHOT
+#  include "mozilla/fuzzing/IPCFuzzController.h"
+#endif
+
+using namespace IPC;
+
+using base::GetCurrentProcId;
+using base::ProcessHandle;
+using base::ProcessId;
+
+namespace mozilla {
+
+#if defined(XP_WIN)
+// Generate RAII classes for LPTSTR and PSECURITY_DESCRIPTOR.
+MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedLPTStr,
+                                          std::remove_pointer_t<LPTSTR>,
+                                          ::LocalFree)
+MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(
+    ScopedPSecurityDescriptor, std::remove_pointer_t<PSECURITY_DESCRIPTOR>,
+    ::LocalFree)
+#endif
+
+namespace ipc {
+
+IPCResult IPCResult::Fail(NotNull<IProtocol*> actor, const char* where,
+                          const char* why) {
+  // Calls top-level protocol to handle the error.
+  nsPrintfCString errorMsg("%s %s\n", where, why);
+  actor->GetIPCChannel()->Listener()->ProcessingError(
+      HasResultCodes::MsgProcessingError, errorMsg.get());
+
+  MOZ_ASSERT_UNLESS_FUZZING(false,
+                            "Please ensure to IPC_FAIL only when in an "
+                            "unrecoverable, unexpected state.");
+
+  return IPCResult(false);
+}
+
+void AnnotateSystemError() {
+  int64_t error = 0;
+#if defined(XP_WIN)
+  error = ::GetLastError();
+#elif defined(OS_POSIX)
+  error = errno;
+#endif
+  if (error) {
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCSystemError,
+        nsPrintfCString("%" PRId64, error));
+  }
+}
+
+#if defined(XP_MACOSX)
+void AnnotateCrashReportWithErrno(CrashReporter::Annotation tag, int error) {
+  CrashReporter::AnnotateCrashReport(tag, error);
+}
+#endif  // defined(XP_MACOSX)
+
+#if defined(DEBUG) || defined(FUZZING)
+// This overload is for testability; application code should use the single-
+// argument version (defined in the ProtocolUtils.h) which takes the filter from
+// the environment.
+bool LoggingEnabledFor(const char* aTopLevelProtocol, const char* aFilter) {
+  if (!aFilter) {
+    return false;
+  }
+  if (strcmp(aFilter, "1") == 0) {
+    return true;
+  }
+
+  const char kDelimiters[] = ", ";
+  Tokenizer tokens(aFilter, kDelimiters);
+  Tokenizer::Token t;
+  while (tokens.Next(t)) {
+    if (t.Type() == Tokenizer::TOKEN_WORD &&
+        t.AsString() == aTopLevelProtocol) {
+      return true;
+    }
+  }
+
+  return false;
+}
+#endif  // defined(DEBUG) || defined(FUZZING)
+
+void LogMessageForProtocol(const char* aTopLevelProtocol,
+                           base::ProcessId aOtherPid,
+                           const char* aContextDescription, uint32_t aMessageId,
+                           MessageDirection aDirection) {
+  nsPrintfCString logMessage(
+      "[time: %" PRId64 "][%" PRIPID "%s%" PRIPID "] [%s] %s %s\n", PR_Now(),
+      base::GetCurrentProcId(),
+      aDirection == MessageDirection::eReceiving ? "<-" : "->", aOtherPid,
+      aTopLevelProtocol, aContextDescription,
+      StringFromIPCMessageType(aMessageId));
+#ifdef ANDROID
+  __android_log_write(ANDROID_LOG_INFO, "GeckoIPC", logMessage.get());
+#endif
+  fputs(logMessage.get(), stderr);
+}
+
+void ProtocolErrorBreakpoint(const char* aMsg) {
+  // Bugs that generate these error messages can be tough to
+  // reproduce.  Log always in the hope that someone finds the error
+  // message.
+  printf_stderr("IPDL protocol error: %s\n", aMsg);
+}
+
+void PickleFatalError(const char* aMsg, IProtocol* aActor) {
+  if (aActor) {
+    aActor->FatalError(aMsg);
+  } else {
+    FatalError(aMsg, false);
+  }
+}
+
+void FatalError(const char* aMsg, bool aIsParent) {
+#ifndef FUZZING
+  ProtocolErrorBreakpoint(aMsg);
+#endif
+
+  nsAutoCString formattedMessage("IPDL error: \"");
+  formattedMessage.AppendASCII(aMsg);
+  if (aIsParent) {
+    // We're going to crash the parent process because at this time
+    // there's no other really nice way of getting a minidump out of
+    // this process if we're off the main thread.
+    formattedMessage.AppendLiteral("\". Intentionally crashing.");
+    NS_ERROR(formattedMessage.get());
+    CrashReporter::AnnotateCrashReport(
+        CrashReporter::Annotation::IPCFatalErrorMsg, nsDependentCString(aMsg));
+    AnnotateSystemError();
+#ifndef FUZZING
+    MOZ_CRASH("IPC FatalError in the parent process!");
+#endif
+  } else {
+    formattedMessage.AppendLiteral("\". abort()ing as a result.");
+#ifndef FUZZING
+    MOZ_CRASH_UNSAFE(formattedMessage.get());
+#endif
+  }
+}
+
+void LogicError(const char* aMsg) { MOZ_CRASH_UNSAFE(aMsg); }
+
+void ActorIdReadError(const char* aActorDescription) {
+#ifndef FUZZING
+  MOZ_CRASH_UNSAFE_PRINTF("Error deserializing id for %s", aActorDescription);
+#endif
+}
+
+void BadActorIdError(const char* aActorDescription) {
+  nsPrintfCString message("bad id for %s", aActorDescription);
+  ProtocolErrorBreakpoint(message.get());
+}
+
+void ActorLookupError(const char* aActorDescription) {
+  nsPrintfCString message("could not lookup id for %s", aActorDescription);
+  ProtocolErrorBreakpoint(message.get());
+}
+
+void MismatchedActorTypeError(const char* aActorDescription) {
+  nsPrintfCString message("actor that should be of type %s has different type",
+                          aActorDescription);
+  ProtocolErrorBreakpoint(message.get());
+}
+
+void UnionTypeReadError(const char* aUnionName) {
+  MOZ_CRASH_UNSAFE_PRINTF("error deserializing type of union %s", aUnionName);
+}
+
+void ArrayLengthReadError(const char* aElementName) {
+  MOZ_CRASH_UNSAFE_PRINTF("error deserializing length of %s[]", aElementName);
+}
+
+void SentinelReadError(const char* aClassName) {
+  MOZ_CRASH_UNSAFE_PRINTF("incorrect sentinel when reading %s", aClassName);
+}
+
+ActorLifecycleProxy::ActorLifecycleProxy(IProtocol* aActor) : mActor(aActor) {
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mActor->CanSend(),
+             "Cannot create LifecycleProxy for non-connected actor!");
+
+  // Take a reference to our manager's lifecycle proxy to try to hold it &
+  // ensure it doesn't die before us.
+  if (mActor->mManager) {
+    mManager = mActor->mManager->mLifecycleProxy;
+  }
+
+  // Record that we've taken our first reference to our actor.
+  mActor->ActorAlloc();
+}
+
+WeakActorLifecycleProxy* ActorLifecycleProxy::GetWeakProxy() {
+  if (!mWeakProxy) {
+    mWeakProxy = new WeakActorLifecycleProxy(this);
+  }
+  return mWeakProxy;
+}
+
+ActorLifecycleProxy::~ActorLifecycleProxy() {
+  if (mWeakProxy) {
+    mWeakProxy->mProxy = nullptr;
+    mWeakProxy = nullptr;
+  }
+
+  // When the LifecycleProxy's lifetime has come to an end, it means that the
+  // actor should have its `Dealloc` method called on it. In a well-behaved
+  // actor, this will release the IPC-held reference to the actor.
+  //
+  // If the actor has already died before the `LifecycleProxy`, the `IProtocol`
+  // destructor below will clear our reference to it, preventing us from
+  // performing a use-after-free here.
+  if (!mActor) {
+    return;
+  }
+
+  // Clear our actor's state back to inactive, and then invoke ActorDealloc.
+  MOZ_ASSERT(mActor->mLinkStatus == LinkStatus::Destroyed,
+             "Deallocating non-destroyed actor!");
+  mActor->mLifecycleProxy = nullptr;
+  mActor->mLinkStatus = LinkStatus::Inactive;
+  mActor->ActorDealloc();
+  mActor = nullptr;
+}
+
+WeakActorLifecycleProxy::WeakActorLifecycleProxy(ActorLifecycleProxy* aProxy)
+    : mProxy(aProxy), mActorEventTarget(GetCurrentSerialEventTarget()) {}
+
+WeakActorLifecycleProxy::~WeakActorLifecycleProxy() {
+  MOZ_DIAGNOSTIC_ASSERT(!mProxy, "Destroyed before mProxy was cleared?");
+}
+
+IProtocol* WeakActorLifecycleProxy::Get() const {
+  MOZ_DIAGNOSTIC_ASSERT(mActorEventTarget->IsOnCurrentThread());
+  return mProxy ? mProxy->Get() : nullptr;
+}
+
+WeakActorLifecycleProxy* IProtocol::GetWeakLifecycleProxy() {
+  return mLifecycleProxy ? mLifecycleProxy->GetWeakProxy() : nullptr;
+}
+
+IProtocol::~IProtocol() {
+  // If the actor still has a lifecycle proxy when it is being torn down, it
+  // means that IPC was not given control over the lifecycle of the actor
+  // correctly. Usually this means that the actor was destroyed while IPC is
+  // calling a message handler for it, and the actor incorrectly frees itself
+  // during that operation.
+  //
+  // As this happens unfortunately frequently, due to many odd protocols in
+  // Gecko, simply emit a warning and clear the weak backreference from our
+  // LifecycleProxy back to us.
+  if (mLifecycleProxy) {
+    NS_WARNING(
+        nsPrintfCString("Actor destructor for '%s%s' called before IPC "
+                        "lifecycle complete!\n"
+                        "References to this actor may unexpectedly dangle!",
+                        GetProtocolName(),
+                        GetSide() == ChildSide ? "Child" : "Parent")
+            .get());
+
+    mLifecycleProxy->mActor = nullptr;
+
+    // If we are somehow being destroyed while active, make sure that the
+    // existing IPC reference has been freed. If the status of the actor is
+    // `Destroyed`, the reference has already been freed, and we shouldn't free
+    // it a second time.
+    MOZ_ASSERT(mLinkStatus != LinkStatus::Inactive);
+    if (mLinkStatus != LinkStatus::Destroyed) {
+      NS_IF_RELEASE(mLifecycleProxy);
+    }
+    mLifecycleProxy = nullptr;
+  }
+}
+
+// The following methods either directly forward to the toplevel protocol, or
+// almost directly do.
+int32_t IProtocol::Register(IProtocol* aRouted) {
+  return mToplevel->Register(aRouted);
+}
+int32_t IProtocol::RegisterID(IProtocol* aRouted, int32_t aId) {
+  return mToplevel->RegisterID(aRouted, aId);
+}
+IProtocol* IProtocol::Lookup(int32_t aId) { return mToplevel->Lookup(aId); }
+void IProtocol::Unregister(int32_t aId) {
+  if (aId == mId) {
+    mId = kFreedActorId;
+  }
+  return mToplevel->Unregister(aId);
+}
+
+Shmem::SharedMemory* IProtocol::CreateSharedMemory(size_t aSize, bool aUnsafe,
+                                                   int32_t* aId) {
+  return mToplevel->CreateSharedMemory(aSize, aUnsafe, aId);
+}
+Shmem::SharedMemory* IProtocol::LookupSharedMemory(int32_t aId) {
+  return mToplevel->LookupSharedMemory(aId);
+}
+bool IProtocol::IsTrackingSharedMemory(Shmem::SharedMemory* aSegment) {
+  return mToplevel->IsTrackingSharedMemory(aSegment);
+}
+bool IProtocol::DestroySharedMemory(Shmem& aShmem) {
+  return mToplevel->DestroySharedMemory(aShmem);
+}
+
+MessageChannel* IProtocol::GetIPCChannel() {
+  return mToplevel->GetIPCChannel();
+}
+const MessageChannel* IProtocol::GetIPCChannel() const {
+  return mToplevel->GetIPCChannel();
+}
+
+nsISerialEventTarget* IProtocol::GetActorEventTarget() {
+  return GetIPCChannel()->GetWorkerEventTarget();
+}
+
+void IProtocol::SetId(int32_t aId) {
+  MOZ_ASSERT(mId == aId || mLinkStatus == LinkStatus::Inactive);
+  mId = aId;
+}
+
+Maybe<IProtocol*> IProtocol::ReadActor(IPC::MessageReader* aReader,
+                                       bool aNullable,
+                                       const char* aActorDescription,
+                                       int32_t aProtocolTypeId) {
+  int32_t id;
+  if (!IPC::ReadParam(aReader, &id)) {
+    ActorIdReadError(aActorDescription);
+    return Nothing();
+  }
+
+  if (id == 1 || (id == 0 && !aNullable)) {
+    BadActorIdError(aActorDescription);
+    return Nothing();
+  }
+
+  if (id == 0) {
+    return Some(static_cast<IProtocol*>(nullptr));
+  }
+
+  IProtocol* listener = this->Lookup(id);
+  if (!listener) {
+    ActorLookupError(aActorDescription);
+    return Nothing();
+  }
+
+  if (listener->GetProtocolId() != aProtocolTypeId) {
+    MismatchedActorTypeError(aActorDescription);
+    return Nothing();
+  }
+
+  return Some(listener);
+}
+
+void IProtocol::FatalError(const char* const aErrorMsg) {
+  HandleFatalError(aErrorMsg);
+}
+
+void IProtocol::HandleFatalError(const char* aErrorMsg) {
+  if (IProtocol* manager = Manager()) {
+    manager->HandleFatalError(aErrorMsg);
+    return;
+  }
+
+  mozilla::ipc::FatalError(aErrorMsg, mSide == ParentSide);
+  if (CanSend()) {
+    GetIPCChannel()->CloseWithError();
+  }
+}
+
+bool IProtocol::AllocShmem(size_t aSize, Shmem* aOutMem) {
+  if (!CanSend()) {
+    NS_WARNING(
+        "Shmem not allocated.  Cannot communicate with the other actor.");
+    return false;
+  }
+
+  Shmem::id_t id;
+  Shmem::SharedMemory* rawmem(CreateSharedMemory(aSize, false, &id));
+  if (!rawmem) {
+    return false;
+  }
+
+  *aOutMem = Shmem(rawmem, id);
+  return true;
+}
+
+bool IProtocol::AllocUnsafeShmem(size_t aSize, Shmem* aOutMem) {
+  if (!CanSend()) {
+    NS_WARNING(
+        "Shmem not allocated.  Cannot communicate with the other actor.");
+    return false;
+  }
+
+  Shmem::id_t id;
+  Shmem::SharedMemory* rawmem(CreateSharedMemory(aSize, true, &id));
+  if (!rawmem) {
+    return false;
+  }
+
+  *aOutMem = Shmem(rawmem, id);
+  return true;
+}
+
+bool IProtocol::DeallocShmem(Shmem& aMem) {
+  bool ok = DestroySharedMemory(aMem);
+#ifdef DEBUG
+  if (!ok) {
+    if (mSide == ChildSide) {
+      FatalError("bad Shmem");
+    } else {
+      NS_WARNING("bad Shmem");
+    }
+    return false;
+  }
+#endif  // DEBUG
+  aMem.forget();
+  return ok;
+}
+
+void IProtocol::SetManager(IProtocol* aManager) {
+  MOZ_RELEASE_ASSERT(!mManager || mManager == aManager);
+  mManager = aManager;
+  mToplevel = aManager->mToplevel;
+}
+
+void IProtocol::SetManagerAndRegister(IProtocol* aManager) {
+  // Set the manager prior to registering so registering properly inherits
+  // the manager's event target.
+  SetManager(aManager);
+
+  aManager->Register(this);
+}
+
+void IProtocol::SetManagerAndRegister(IProtocol* aManager, int32_t aId) {
+  // Set the manager prior to registering so registering properly inherits
+  // the manager's event target.
+  SetManager(aManager);
+
+  aManager->RegisterID(this, aId);
+}
+
+bool IProtocol::ChannelSend(UniquePtr<IPC::Message> aMsg) {
+  if (CanSend()) {
+    // NOTE: This send call failing can only occur during toplevel channel
+    // teardown. As this is an async call, this isn't reasonable to predict or
+    // respond to, so just drop the message on the floor silently.
+    GetIPCChannel()->Send(std::move(aMsg));
+    return true;
+  }
+
+  WarnMessageDiscarded(aMsg.get());
+  return false;
+}
+
+bool IProtocol::ChannelSend(UniquePtr<IPC::Message> aMsg,
+                            UniquePtr<IPC::Message>* aReply) {
+  if (CanSend()) {
+    return GetIPCChannel()->Send(std::move(aMsg), aReply);
+  }
+
+  WarnMessageDiscarded(aMsg.get());
+  return false;
+}
+
+#ifdef DEBUG
+void IProtocol::WarnMessageDiscarded(IPC::Message* aMsg) {
+  NS_WARNING(nsPrintfCString("IPC message '%s' discarded: actor cannot send",
+                             aMsg->name())
+                 .get());
+}
+#endif
+
+void IProtocol::ActorConnected() {
+  if (mLinkStatus != LinkStatus::Inactive) {
+    return;
+  }
+
+#ifdef FUZZING_SNAPSHOT
+  fuzzing::IPCFuzzController::instance().OnActorConnected(this);
+#endif
+
+  mLinkStatus = LinkStatus::Connected;
+
+  MOZ_ASSERT(!mLifecycleProxy, "double-connecting live actor");
+  mLifecycleProxy = new ActorLifecycleProxy(this);
+  NS_ADDREF(mLifecycleProxy);  // Reference freed in DestroySubtree();
+}
+
+void IProtocol::DoomSubtree() {
+  MOZ_ASSERT(CanSend(), "dooming non-connected actor");
+  MOZ_ASSERT(mLifecycleProxy, "dooming zombie actor");
+
+  nsTArray<RefPtr<ActorLifecycleProxy>> managed;
+  AllManagedActors(managed);
+  for (ActorLifecycleProxy* proxy : managed) {
+    // Guard against actor being disconnected or destroyed during previous Doom
+    IProtocol* actor = proxy->Get();
+    if (actor && actor->CanSend()) {
+      actor->DoomSubtree();
+    }
+  }
+
+  // ActorDoom is called immediately before changing state, this allows messages
+  // to be sent during ActorDoom immediately before the channel is closed and
+  // sending messages is disabled.
+  ActorDoom();
+  mLinkStatus = LinkStatus::Doomed;
+}
+
+void IProtocol::DestroySubtree(ActorDestroyReason aWhy) {
+  MOZ_ASSERT(CanRecv(), "destroying non-connected actor");
+  MOZ_ASSERT(mLifecycleProxy, "destroying zombie actor");
+
+#ifdef FUZZING_SNAPSHOT
+  fuzzing::IPCFuzzController::instance().OnActorDestroyed(this);
+#endif
+
+  int32_t id = Id();
+
+  // If we're a managed actor, unregister from our manager
+  if (Manager()) {
+    Unregister(id);
+  }
+
+  // Destroy subtree
+  ActorDestroyReason subtreeWhy = aWhy;
+  if (aWhy == Deletion || aWhy == FailedConstructor) {
+    subtreeWhy = AncestorDeletion;
+  }
+
+  nsTArray<RefPtr<ActorLifecycleProxy>> managed;
+  AllManagedActors(managed);
+  for (ActorLifecycleProxy* proxy : managed) {
+    // Guard against actor being disconnected or destroyed during previous
+    // Destroy
+    IProtocol* actor = proxy->Get();
+    if (actor && actor->CanRecv()) {
+      actor->DestroySubtree(subtreeWhy);
+    }
+  }
+
+  // Ensure that we don't send any messages while we're calling `ActorDestroy`
+  // by setting our state to `Doomed`.
+  mLinkStatus = LinkStatus::Doomed;
+
+  // The actor is being destroyed, reject any pending responses, invoke
+  // `ActorDestroy` to destroy it, and then clear our status to
+  // `LinkStatus::Destroyed`.
+  GetIPCChannel()->RejectPendingResponsesForActor(id);
+  ActorDestroy(aWhy);
+  mLinkStatus = LinkStatus::Destroyed;
+}
+
+IToplevelProtocol::IToplevelProtocol(const char* aName, ProtocolId aProtoId,
+                                     Side aSide)
+    : IProtocol(aProtoId, aSide),
+      mOtherPid(base::kInvalidProcessId),
+      mLastLocalId(0),
+      mChannel(aName, this) {
+  mToplevel = this;
+}
+
+void IToplevelProtocol::SetOtherProcessId(base::ProcessId aOtherPid) {
+  mOtherPid = aOtherPid;
+}
+
+bool IToplevelProtocol::Open(ScopedPort aPort, const nsID& aMessageChannelId,
+                             base::ProcessId aOtherPid,
+                             nsISerialEventTarget* aEventTarget) {
+  SetOtherProcessId(aOtherPid);
+  return GetIPCChannel()->Open(std::move(aPort), mSide, aMessageChannelId,
+                               aEventTarget);
+}
+
+bool IToplevelProtocol::Open(IToplevelProtocol* aTarget,
+                             nsISerialEventTarget* aEventTarget,
+                             mozilla::ipc::Side aSide) {
+  SetOtherProcessId(base::GetCurrentProcId());
+  aTarget->SetOtherProcessId(base::GetCurrentProcId());
+  return GetIPCChannel()->Open(aTarget->GetIPCChannel(), aEventTarget, aSide);
+}
+
+bool IToplevelProtocol::OpenOnSameThread(IToplevelProtocol* aTarget,
+                                         Side aSide) {
+  SetOtherProcessId(base::GetCurrentProcId());
+  aTarget->SetOtherProcessId(base::GetCurrentProcId());
+  return GetIPCChannel()->OpenOnSameThread(aTarget->GetIPCChannel(), aSide);
+}
+
+void IToplevelProtocol::NotifyImpendingShutdown() {
+  if (CanRecv()) {
+    GetIPCChannel()->NotifyImpendingShutdown();
+  }
+}
+
+void IToplevelProtocol::Close() { GetIPCChannel()->Close(); }
+
+void IToplevelProtocol::CloseWithError() { GetIPCChannel()->CloseWithError(); }
+
+void IToplevelProtocol::SetReplyTimeoutMs(int32_t aTimeoutMs) {
+  GetIPCChannel()->SetReplyTimeoutMs(aTimeoutMs);
+}
+
+bool IToplevelProtocol::IsOnCxxStack() const {
+  return GetIPCChannel()->IsOnCxxStack();
+}
+
+int32_t IToplevelProtocol::NextId() {
+  // Generate the next ID to use for a shared memory or protocol. Parent and
+  // Child sides of the protocol use different pools.
+  int32_t tag = 0;
+  if (GetSide() == ParentSide) {
+    tag |= 1 << 1;
+  }
+
+  // Check any overflow
+  MOZ_RELEASE_ASSERT(mLastLocalId < (1 << 29));
+
+  // Compute the ID to use with the low two bits as our tag, and the remaining
+  // bits as a monotonic.
+  return (++mLastLocalId << 2) | tag;
+}
+
+int32_t IToplevelProtocol::Register(IProtocol* aRouted) {
+  if (aRouted->Id() != kNullActorId && aRouted->Id() != kFreedActorId) {
+    // If there's already an ID, just return that.
+    return aRouted->Id();
+  }
+  return RegisterID(aRouted, NextId());
+}
+
+int32_t IToplevelProtocol::RegisterID(IProtocol* aRouted, int32_t aId) {
+  aRouted->SetId(aId);
+  aRouted->ActorConnected();
+  MOZ_ASSERT(!mActorMap.Contains(aId), "Don't insert with an existing ID");
+  mActorMap.InsertOrUpdate(aId, aRouted);
+  return aId;
+}
+
+IProtocol* IToplevelProtocol::Lookup(int32_t aId) { return mActorMap.Get(aId); }
+
+void IToplevelProtocol::Unregister(int32_t aId) {
+  MOZ_ASSERT(mActorMap.Contains(aId),
+             "Attempting to remove an ID not in the actor map");
+  mActorMap.Remove(aId);
+}
+
+Shmem::SharedMemory* IToplevelProtocol::CreateSharedMemory(size_t aSize,
+                                                           bool aUnsafe,
+                                                           Shmem::id_t* aId) {
+  RefPtr<Shmem::SharedMemory> segment(Shmem::Alloc(aSize, aUnsafe));
+  if (!segment) {
+    return nullptr;
+  }
+  int32_t id = NextId();
+  Shmem shmem(segment.get(), id);
+
+  UniquePtr<Message> descriptor = shmem.MkCreatedMessage(MSG_ROUTING_CONTROL);
+  if (!descriptor) {
+    return nullptr;
+  }
+  Unused << GetIPCChannel()->Send(std::move(descriptor));
+
+  *aId = shmem.Id();
+  Shmem::SharedMemory* rawSegment = segment.get();
+  MOZ_ASSERT(!mShmemMap.Contains(*aId), "Don't insert with an existing ID");
+  mShmemMap.InsertOrUpdate(*aId, segment.forget().take());
+  return rawSegment;
+}
+
+Shmem::SharedMemory* IToplevelProtocol::LookupSharedMemory(Shmem::id_t aId) {
+  return mShmemMap.Get(aId);
+}
+
+bool IToplevelProtocol::IsTrackingSharedMemory(Shmem::SharedMemory* segment) {
+  for (const auto& shmem : mShmemMap.Values()) {
+    if (segment == shmem) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool IToplevelProtocol::DestroySharedMemory(Shmem& shmem) {
+  Shmem::id_t aId = shmem.Id();
+  Shmem::SharedMemory* segment = LookupSharedMemory(aId);
+  if (!segment) {
+    return false;
+  }
+
+  UniquePtr<Message> descriptor = shmem.MkDestroyedMessage(MSG_ROUTING_CONTROL);
+
+  MOZ_ASSERT(mShmemMap.Contains(aId),
+             "Attempting to remove an ID not in the shmem map");
+  mShmemMap.Remove(aId);
+  Shmem::Dealloc(segment);
+
+  MessageChannel* channel = GetIPCChannel();
+  if (!channel->CanSend()) {
+    return true;
+  }
+
+  return descriptor && channel->Send(std::move(descriptor));
+}
+
+void IToplevelProtocol::DeallocShmems() {
+  for (const auto& shmem : mShmemMap.Values()) {
+    Shmem::Dealloc(shmem);
+  }
+  mShmemMap.Clear();
+}
+
+bool IToplevelProtocol::ShmemCreated(const Message& aMsg) {
+  Shmem::id_t id;
+  RefPtr<Shmem::SharedMemory> rawmem(Shmem::OpenExisting(aMsg, &id, true));
+  if (!rawmem) {
+    return false;
+  }
+  MOZ_ASSERT(!mShmemMap.Contains(id), "Don't insert with an existing ID");
+  mShmemMap.InsertOrUpdate(id, rawmem.forget().take());
+  return true;
+}
+
+bool IToplevelProtocol::ShmemDestroyed(const Message& aMsg) {
+  Shmem::id_t id;
+  MessageReader reader(aMsg);
+  if (!IPC::ReadParam(&reader, &id)) {
+    return false;
+  }
+  reader.EndRead();
+
+  Shmem::SharedMemory* rawmem = LookupSharedMemory(id);
+  if (rawmem) {
+    MOZ_ASSERT(mShmemMap.Contains(id),
+               "Attempting to remove an ID not in the shmem map");
+    mShmemMap.Remove(id);
+    Shmem::Dealloc(rawmem);
+  }
+  return true;
+}
+
+IPDLResolverInner::IPDLResolverInner(UniquePtr<IPC::Message> aReply,
+                                     IProtocol* aActor)
+    : mReply(std::move(aReply)),
+      mWeakProxy(aActor->GetLifecycleProxy()->GetWeakProxy()) {}
+
+void IPDLResolverInner::ResolveOrReject(
+    bool aResolve, FunctionRef<void(IPC::Message*, IProtocol*)> aWrite) {
+  MOZ_ASSERT(mWeakProxy);
+  MOZ_ASSERT(mWeakProxy->ActorEventTarget()->IsOnCurrentThread());
+  MOZ_ASSERT(mReply);
+
+  UniquePtr<IPC::Message> reply = std::move(mReply);
+
+  IProtocol* actor = mWeakProxy->Get();
+  if (!actor) {
+    NS_WARNING(nsPrintfCString("Not resolving response '%s': actor is dead",
+                               reply->name())
+                   .get());
+    return;
+  }
+
+  IPC::MessageWriter writer(*reply, actor);
+  WriteIPDLParam(&writer, actor, aResolve);
+  aWrite(reply.get(), actor);
+
+  actor->ChannelSend(std::move(reply));
+}
+
+void IPDLResolverInner::Destroy() {
+  if (mReply) {
+    NS_PROXY_DELETE_TO_EVENT_TARGET(IPDLResolverInner,
+                                    mWeakProxy->ActorEventTarget());
+  } else {
+    // If we've already been consumed, just delete without proxying. This avoids
+    // leaking the resolver if the actor's thread is already dead.
+    delete this;
+  }
+}
+
+IPDLResolverInner::~IPDLResolverInner() {
+  if (mReply) {
+    NS_WARNING(
+        nsPrintfCString(
+            "Rejecting reply '%s': resolver dropped without being called",
+            mReply->name())
+            .get());
+    ResolveOrReject(false, [](IPC::Message* aMessage, IProtocol* aActor) {
+      IPC::MessageWriter writer(*aMessage, aActor);
+      ResponseRejectReason reason = ResponseRejectReason::ResolverDestroyed;
+      WriteIPDLParam(&writer, aActor, reason);
+    });
+  }
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/ProtocolUtils.h b/ipc/glue/ProtocolUtils.h
new file mode 100644
index 0000000000..aa398453ae
--- /dev/null
+++ b/ipc/glue/ProtocolUtils.h
@@ -0,0 +1,746 @@
+/* -*- 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 https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_ProtocolUtils_h
+#define mozilla_ipc_ProtocolUtils_h 1
+
+#include <cstddef>
+#include <cstdint>
+#include <utility>
+#include "IPCMessageStart.h"
+#include "base/basictypes.h"
+#include "base/process.h"
+#include "chrome/common/ipc_message.h"
+#include "mojo/core/ports/port_ref.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/FunctionRef.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Scoped.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/ipc/MessageChannel.h"
+#include "mozilla/ipc/MessageLink.h"
+#include "mozilla/ipc/SharedMemory.h"
+#include "mozilla/ipc/Shmem.h"
+#include "nsTHashMap.h"
+#include "nsDebug.h"
+#include "nsISupports.h"
+#include "nsTArrayForwardDeclare.h"
+#include "nsTHashSet.h"
+
+// XXX Things that could be moved to ProtocolUtils.cpp
+#include "base/process_util.h"  // for CloseProcessHandle
+#include "prenv.h"              // for PR_GetEnv
+
+#if defined(ANDROID) && defined(DEBUG)
+#  include <android/log.h>
+#endif
+
+template <typename T>
+class nsPtrHashKey;
+
+// WARNING: this takes into account the private, special-message-type
+// enum in ipc_channel.h.  They need to be kept in sync.
+namespace {
+// XXX the max message ID is actually kuint32max now ... when this
+// changed, the assumptions of the special message IDs changed in that
+// they're not carving out messages from likely-unallocated space, but
+// rather carving out messages from the end of space allocated to
+// protocol 0.  Oops!  We can get away with this until protocol 0
+// starts approaching its 65,536th message.
+enum {
+  // Message types used by DataPipe
+  DATA_PIPE_CLOSED_MESSAGE_TYPE = kuint16max - 18,
+  DATA_PIPE_BYTES_CONSUMED_MESSAGE_TYPE = kuint16max - 17,
+
+  // Message types used by NodeChannel
+  ACCEPT_INVITE_MESSAGE_TYPE = kuint16max - 16,
+  REQUEST_INTRODUCTION_MESSAGE_TYPE = kuint16max - 15,
+  INTRODUCE_MESSAGE_TYPE = kuint16max - 14,
+  BROADCAST_MESSAGE_TYPE = kuint16max - 13,
+  EVENT_MESSAGE_TYPE = kuint16max - 12,
+
+  // Message types used by MessageChannel
+  MANAGED_ENDPOINT_DROPPED_MESSAGE_TYPE = kuint16max - 11,
+  MANAGED_ENDPOINT_BOUND_MESSAGE_TYPE = kuint16max - 10,
+  IMPENDING_SHUTDOWN_MESSAGE_TYPE = kuint16max - 9,
+  BUILD_IDS_MATCH_MESSAGE_TYPE = kuint16max - 8,
+  BUILD_ID_MESSAGE_TYPE = kuint16max - 7,  // unused
+  CHANNEL_OPENED_MESSAGE_TYPE = kuint16max - 6,
+  SHMEM_DESTROYED_MESSAGE_TYPE = kuint16max - 5,
+  SHMEM_CREATED_MESSAGE_TYPE = kuint16max - 4,
+  GOODBYE_MESSAGE_TYPE = kuint16max - 3,
+  CANCEL_MESSAGE_TYPE = kuint16max - 2,
+
+  // kuint16max - 1 is used by ipc_channel.h.
+};
+
+}  // namespace
+
+class MessageLoop;
+class PickleIterator;
+class nsISerialEventTarget;
+
+namespace mozilla {
+class SchedulerGroup;
+
+namespace dom {
+class ContentParent;
+}  // namespace dom
+
+namespace net {
+class NeckoParent;
+}  // namespace net
+
+namespace ipc {
+
+// Scoped base::ProcessHandle to ensure base::CloseProcessHandle is called.
+struct ScopedProcessHandleTraits {
+  typedef base::ProcessHandle type;
+
+  static type empty() { return base::kInvalidProcessHandle; }
+
+  static void release(type aProcessHandle) {
+    if (aProcessHandle && aProcessHandle != base::kInvalidProcessHandle) {
+      base::CloseProcessHandle(aProcessHandle);
+    }
+  }
+};
+typedef mozilla::Scoped<ScopedProcessHandleTraits> ScopedProcessHandle;
+
+class ProtocolFdMapping;
+class ProtocolCloneContext;
+
+// Used to pass references to protocol actors across the wire.
+// Actors created on the parent-side have a positive ID, and actors
+// allocated on the child side have a negative ID.
+struct ActorHandle {
+  int mId;
+};
+
+// What happens if Interrupt calls race?
+enum RacyInterruptPolicy { RIPError, RIPChildWins, RIPParentWins };
+
+enum class LinkStatus : uint8_t {
+  // The actor has not established a link yet, or the actor is no longer in use
+  // by IPC, and its 'Dealloc' method has been called or is being called.
+  //
+  // NOTE: This state is used instead of an explicit `Freed` state when IPC no
+  // longer holds references to the current actor as we currently re-open
+  // existing actors. Once we fix these poorly behaved actors, this loopback
+  // state can be split to have the final state not be the same as the initial
+  // state.
+  Inactive,
+
+  // A live link is connected to the other side of this actor.
+  Connected,
+
+  // The link has begun being destroyed. Messages may still be received, but
+  // cannot be sent. (exception: sync/intr replies may be sent while Doomed).
+  Doomed,
+
+  // The link has been destroyed, and messages will no longer be sent or
+  // received.
+  Destroyed,
+};
+
+typedef IPCMessageStart ProtocolId;
+
+// Generated by IPDL compiler
+const char* ProtocolIdToName(IPCMessageStart aId);
+
+class IToplevelProtocol;
+class ActorLifecycleProxy;
+class WeakActorLifecycleProxy;
+class IPDLResolverInner;
+class UntypedManagedEndpoint;
+
+class IProtocol : public HasResultCodes {
+ public:
+  enum ActorDestroyReason {
+    FailedConstructor,
+    Deletion,
+    AncestorDeletion,
+    NormalShutdown,
+    AbnormalShutdown,
+    ManagedEndpointDropped
+  };
+
+  typedef base::ProcessId ProcessId;
+  typedef IPC::Message Message;
+
+  IProtocol(ProtocolId aProtoId, Side aSide)
+      : mId(0),
+        mProtocolId(aProtoId),
+        mSide(aSide),
+        mLinkStatus(LinkStatus::Inactive),
+        mLifecycleProxy(nullptr),
+        mManager(nullptr),
+        mToplevel(nullptr) {}
+
+  IToplevelProtocol* ToplevelProtocol() { return mToplevel; }
+  const IToplevelProtocol* ToplevelProtocol() const { return mToplevel; }
+
+  // The following methods either directly forward to the toplevel protocol, or
+  // almost directly do.
+  int32_t Register(IProtocol* aRouted);
+  int32_t RegisterID(IProtocol* aRouted, int32_t aId);
+  IProtocol* Lookup(int32_t aId);
+  void Unregister(int32_t aId);
+
+  Shmem::SharedMemory* CreateSharedMemory(size_t aSize, bool aUnsafe,
+                                          int32_t* aId);
+  Shmem::SharedMemory* LookupSharedMemory(int32_t aId);
+  bool IsTrackingSharedMemory(Shmem::SharedMemory* aSegment);
+  bool DestroySharedMemory(Shmem& aShmem);
+
+  MessageChannel* GetIPCChannel();
+  const MessageChannel* GetIPCChannel() const;
+
+  // Get the nsISerialEventTarget which all messages sent to this actor will be
+  // processed on. Unless stated otherwise, all operations on IProtocol which
+  // don't occur on this `nsISerialEventTarget` are unsafe.
+  nsISerialEventTarget* GetActorEventTarget();
+
+  // Actor lifecycle and other properties.
+  ProtocolId GetProtocolId() const { return mProtocolId; }
+  const char* GetProtocolName() const { return ProtocolIdToName(mProtocolId); }
+
+  int32_t Id() const { return mId; }
+  IProtocol* Manager() const { return mManager; }
+
+  ActorLifecycleProxy* GetLifecycleProxy() { return mLifecycleProxy; }
+  WeakActorLifecycleProxy* GetWeakLifecycleProxy();
+
+  Side GetSide() const { return mSide; }
+  bool CanSend() const { return mLinkStatus == LinkStatus::Connected; }
+  bool CanRecv() const {
+    return mLinkStatus == LinkStatus::Connected ||
+           mLinkStatus == LinkStatus::Doomed;
+  }
+
+  // Remove or deallocate a managee given its type.
+  virtual void RemoveManagee(int32_t, IProtocol*) = 0;
+  virtual void DeallocManagee(int32_t, IProtocol*) = 0;
+
+  Maybe<IProtocol*> ReadActor(IPC::MessageReader* aReader, bool aNullable,
+                              const char* aActorDescription,
+                              int32_t aProtocolTypeId);
+
+  virtual Result OnMessageReceived(const Message& aMessage) = 0;
+  virtual Result OnMessageReceived(const Message& aMessage,
+                                   UniquePtr<Message>& aReply) = 0;
+  virtual Result OnCallReceived(const Message& aMessage,
+                                UniquePtr<Message>& aReply) = 0;
+  bool AllocShmem(size_t aSize, Shmem* aOutMem);
+  bool AllocUnsafeShmem(size_t aSize, Shmem* aOutMem);
+  bool DeallocShmem(Shmem& aMem);
+
+  void FatalError(const char* const aErrorMsg);
+  virtual void HandleFatalError(const char* aErrorMsg);
+
+ protected:
+  virtual ~IProtocol();
+
+  friend class IToplevelProtocol;
+  friend class ActorLifecycleProxy;
+  friend class IPDLResolverInner;
+  friend class UntypedManagedEndpoint;
+
+  void SetId(int32_t aId);
+
+  // We have separate functions because the accessibility code manually
+  // calls SetManager.
+  void SetManager(IProtocol* aManager);
+
+  // Sets the manager for the protocol and registers the protocol with
+  // its manager, setting up channels for the protocol as well.  Not
+  // for use outside of IPDL.
+  void SetManagerAndRegister(IProtocol* aManager);
+  void SetManagerAndRegister(IProtocol* aManager, int32_t aId);
+
+  // Helpers for calling `Send` on our underlying IPC channel.
+  bool ChannelSend(UniquePtr<IPC::Message> aMsg);
+  bool ChannelSend(UniquePtr<IPC::Message> aMsg,
+                   UniquePtr<IPC::Message>* aReply);
+  template <typename Value>
+  void ChannelSend(UniquePtr<IPC::Message> aMsg,
+                   IPC::Message::msgid_t aReplyMsgId,
+                   ResolveCallback<Value>&& aResolve,
+                   RejectCallback&& aReject) {
+    if (CanSend()) {
+      GetIPCChannel()->Send(std::move(aMsg), Id(), aReplyMsgId,
+                            std::move(aResolve), std::move(aReject));
+    } else {
+      WarnMessageDiscarded(aMsg.get());
+      aReject(ResponseRejectReason::SendError);
+    }
+  }
+
+  // Collect all actors managed by this object in an array. To make this safer
+  // to iterate, `ActorLifecycleProxy` references are returned rather than raw
+  // actor pointers.
+  virtual void AllManagedActors(
+      nsTArray<RefPtr<ActorLifecycleProxy>>& aActors) const = 0;
+
+  // Internal method called when the actor becomes connected.
+  void ActorConnected();
+
+  // Called immediately before setting the actor state to doomed, and triggering
+  // async actor destruction. Messages may be sent from this callback, but no
+  // later.
+  // FIXME(nika): This is currently unused!
+  virtual void ActorDoom() {}
+  void DoomSubtree();
+
+  // Called when the actor has been destroyed due to an error, a __delete__
+  // message, or a __doom__ reply.
+  virtual void ActorDestroy(ActorDestroyReason aWhy) {}
+  void DestroySubtree(ActorDestroyReason aWhy);
+
+  // Called when IPC has acquired its first reference to the actor. This method
+  // may take references which will later be freed by `ActorDealloc`.
+  virtual void ActorAlloc() {}
+
+  // Called when IPC has released its final reference to the actor. It will call
+  // the dealloc method, causing the actor to be actually freed.
+  //
+  // The actor has been freed after this method returns.
+  virtual void ActorDealloc() {
+    if (Manager()) {
+      Manager()->DeallocManagee(mProtocolId, this);
+    }
+  }
+
+  static const int32_t kNullActorId = 0;
+  static const int32_t kFreedActorId = 1;
+
+ private:
+#ifdef DEBUG
+  void WarnMessageDiscarded(IPC::Message* aMsg);
+#else
+  void WarnMessageDiscarded(IPC::Message*) {}
+#endif
+
+  int32_t mId;
+  ProtocolId mProtocolId;
+  Side mSide;
+  LinkStatus mLinkStatus;
+  ActorLifecycleProxy* mLifecycleProxy;
+  IProtocol* mManager;
+  IToplevelProtocol* mToplevel;
+};
+
+#define IPC_OK() mozilla::ipc::IPCResult::Ok()
+#define IPC_FAIL(actor, why) \
+  mozilla::ipc::IPCResult::Fail(WrapNotNull(actor), __func__, (why))
+#define IPC_FAIL_NO_REASON(actor) \
+  mozilla::ipc::IPCResult::Fail(WrapNotNull(actor), __func__)
+
+/**
+ * All message deserializer and message handler should return this
+ * type via above macros. We use a less generic name here to avoid
+ * conflict with mozilla::Result because we have quite a few using
+ * namespace mozilla::ipc; in the code base.
+ */
+class IPCResult {
+ public:
+  static IPCResult Ok() { return IPCResult(true); }
+  static IPCResult Fail(NotNull<IProtocol*> aActor, const char* aWhere,
+                        const char* aWhy = "");
+  MOZ_IMPLICIT operator bool() const { return mSuccess; }
+
+ private:
+  explicit IPCResult(bool aResult) : mSuccess(aResult) {}
+  bool mSuccess;
+};
+
+class UntypedEndpoint;
+
+template <class PFooSide>
+class Endpoint;
+
+template <class PFooSide>
+class ManagedEndpoint;
+
+/**
+ * All top-level protocols should inherit this class.
+ *
+ * IToplevelProtocol tracks all top-level protocol actors created from
+ * this protocol actor.
+ */
+class IToplevelProtocol : public IProtocol {
+  template <class PFooSide>
+  friend class Endpoint;
+
+ protected:
+  explicit IToplevelProtocol(const char* aName, ProtocolId aProtoId,
+                             Side aSide);
+  ~IToplevelProtocol() = default;
+
+ public:
+  // All top-level protocols are refcounted.
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  // Shadow methods on IProtocol which are implemented directly on toplevel
+  // actors.
+  int32_t Register(IProtocol* aRouted);
+  int32_t RegisterID(IProtocol* aRouted, int32_t aId);
+  IProtocol* Lookup(int32_t aId);
+  void Unregister(int32_t aId);
+
+  Shmem::SharedMemory* CreateSharedMemory(size_t aSize, bool aUnsafe,
+                                          int32_t* aId);
+  Shmem::SharedMemory* LookupSharedMemory(int32_t aId);
+  bool IsTrackingSharedMemory(Shmem::SharedMemory* aSegment);
+  bool DestroySharedMemory(Shmem& aShmem);
+
+  MessageChannel* GetIPCChannel() { return &mChannel; }
+  const MessageChannel* GetIPCChannel() const { return &mChannel; }
+
+  void SetOtherProcessId(base::ProcessId aOtherPid);
+
+  virtual void OnChannelClose() = 0;
+  virtual void OnChannelError() = 0;
+  virtual void ProcessingError(Result aError, const char* aMsgName) {}
+
+  bool Open(ScopedPort aPort, const nsID& aMessageChannelId,
+            base::ProcessId aOtherPid,
+            nsISerialEventTarget* aEventTarget = nullptr);
+
+  bool Open(IToplevelProtocol* aTarget, nsISerialEventTarget* aEventTarget,
+            mozilla::ipc::Side aSide = mozilla::ipc::UnknownSide);
+
+  // Open a toplevel actor such that both ends of the actor's channel are on
+  // the same thread. This method should be called on the thread to perform
+  // the link.
+  //
+  // WARNING: Attempting to send a sync or intr message on the same thread
+  // will crash.
+  bool OpenOnSameThread(IToplevelProtocol* aTarget,
+                        mozilla::ipc::Side aSide = mozilla::ipc::UnknownSide);
+
+  /**
+   * This sends a special message that is processed on the IO thread, so that
+   * other actors can know that the process will soon shutdown.
+   */
+  void NotifyImpendingShutdown();
+
+  void Close();
+  void CloseWithError();
+
+  void SetReplyTimeoutMs(int32_t aTimeoutMs);
+
+  void DeallocShmems();
+  bool ShmemCreated(const Message& aMsg);
+  bool ShmemDestroyed(const Message& aMsg);
+
+  virtual bool ShouldContinueFromReplyTimeout() { return false; }
+
+  // WARNING: This function is called with the MessageChannel monitor held.
+  virtual void IntentionalCrash() { MOZ_CRASH("Intentional IPDL crash"); }
+
+  // The code here is only useful for fuzzing. It should not be used for any
+  // other purpose.
+#ifdef DEBUG
+  // Returns true if we should simulate a timeout.
+  // WARNING: This is a testing-only function that is called with the
+  // MessageChannel monitor held. Don't do anything fancy here or we could
+  // deadlock.
+  virtual bool ArtificialTimeout() { return false; }
+
+  // Returns true if we want to cause the worker thread to sleep with the
+  // monitor unlocked.
+  virtual bool NeedArtificialSleep() { return false; }
+
+  // This function should be implemented to sleep for some amount of time on
+  // the worker thread. Will only be called if NeedArtificialSleep() returns
+  // true.
+  virtual void ArtificialSleep() {}
+#else
+  bool ArtificialTimeout() { return false; }
+  bool NeedArtificialSleep() { return false; }
+  void ArtificialSleep() {}
+#endif
+
+  bool IsOnCxxStack() const;
+
+  virtual void ProcessRemoteNativeEventsInInterruptCall() {}
+
+  virtual void OnChannelReceivedMessage(const Message& aMsg) {}
+
+  void OnIPCChannelOpened() { ActorConnected(); }
+
+  base::ProcessId OtherPidMaybeInvalid() const { return mOtherPid; }
+
+ private:
+  int32_t NextId();
+
+  template <class T>
+  using IDMap = nsTHashMap<nsUint32HashKey, T>;
+
+  base::ProcessId mOtherPid;
+
+  // NOTE NOTE NOTE
+  // Used to be on mState
+  int32_t mLastLocalId;
+  IDMap<IProtocol*> mActorMap;
+  IDMap<Shmem::SharedMemory*> mShmemMap;
+
+  MessageChannel mChannel;
+};
+
+class IShmemAllocator {
+ public:
+  virtual bool AllocShmem(size_t aSize, mozilla::ipc::Shmem* aShmem) = 0;
+  virtual bool AllocUnsafeShmem(size_t aSize, mozilla::ipc::Shmem* aShmem) = 0;
+  virtual bool DeallocShmem(mozilla::ipc::Shmem& aShmem) = 0;
+};
+
+#define FORWARD_SHMEM_ALLOCATOR_TO(aImplClass)                             \
+  virtual bool AllocShmem(size_t aSize, mozilla::ipc::Shmem* aShmem)       \
+      override {                                                           \
+    return aImplClass::AllocShmem(aSize, aShmem);                          \
+  }                                                                        \
+  virtual bool AllocUnsafeShmem(size_t aSize, mozilla::ipc::Shmem* aShmem) \
+      override {                                                           \
+    return aImplClass::AllocUnsafeShmem(aSize, aShmem);                    \
+  }                                                                        \
+  virtual bool DeallocShmem(mozilla::ipc::Shmem& aShmem) override {        \
+    return aImplClass::DeallocShmem(aShmem);                               \
+  }
+
+inline bool LoggingEnabled() {
+#if defined(DEBUG) || defined(FUZZING)
+  return !!PR_GetEnv("MOZ_IPC_MESSAGE_LOG");
+#else
+  return false;
+#endif
+}
+
+#if defined(DEBUG) || defined(FUZZING)
+bool LoggingEnabledFor(const char* aTopLevelProtocol, const char* aFilter);
+#endif
+
+inline bool LoggingEnabledFor(const char* aTopLevelProtocol) {
+#if defined(DEBUG) || defined(FUZZING)
+  return LoggingEnabledFor(aTopLevelProtocol, PR_GetEnv("MOZ_IPC_MESSAGE_LOG"));
+#else
+  return false;
+#endif
+}
+
+MOZ_NEVER_INLINE void LogMessageForProtocol(const char* aTopLevelProtocol,
+                                            base::ProcessId aOtherPid,
+                                            const char* aContextDescription,
+                                            uint32_t aMessageId,
+                                            MessageDirection aDirection);
+
+MOZ_NEVER_INLINE void ProtocolErrorBreakpoint(const char* aMsg);
+
+// IPC::MessageReader and IPC::MessageWriter call this function for FatalError
+// calls which come from serialization/deserialization.
+MOZ_NEVER_INLINE void PickleFatalError(const char* aMsg, IProtocol* aActor);
+
+// The code generator calls this function for errors which come from the
+// methods of protocols.  Doing this saves codesize by making the error
+// cases significantly smaller.
+MOZ_NEVER_INLINE void FatalError(const char* aMsg, bool aIsParent);
+
+// The code generator calls this function for errors which are not
+// protocol-specific: errors in generated struct methods or errors in
+// transition functions, for instance.  Doing this saves codesize by
+// by making the error cases significantly smaller.
+MOZ_NEVER_INLINE void LogicError(const char* aMsg);
+
+MOZ_NEVER_INLINE void ActorIdReadError(const char* aActorDescription);
+
+MOZ_NEVER_INLINE void BadActorIdError(const char* aActorDescription);
+
+MOZ_NEVER_INLINE void ActorLookupError(const char* aActorDescription);
+
+MOZ_NEVER_INLINE void MismatchedActorTypeError(const char* aActorDescription);
+
+MOZ_NEVER_INLINE void UnionTypeReadError(const char* aUnionName);
+
+MOZ_NEVER_INLINE void ArrayLengthReadError(const char* aElementName);
+
+MOZ_NEVER_INLINE void SentinelReadError(const char* aElementName);
+
+/**
+ * Annotate the crash reporter with the error code from the most recent system
+ * call. Returns the system error.
+ */
+void AnnotateSystemError();
+
+// The ActorLifecycleProxy is a helper type used internally by IPC to maintain a
+// maybe-owning reference to an IProtocol object. For well-behaved actors
+// which are not freed until after their `Dealloc` method is called, a
+// reference to an actor's `ActorLifecycleProxy` object is an owning one, as the
+// `Dealloc` method will only be called when all references to the
+// `ActorLifecycleProxy` are released.
+//
+// Unfortunately, some actors may be destroyed before their `Dealloc` method
+// is called. For these actors, `ActorLifecycleProxy` acts as a weak pointer,
+// and will begin to return `nullptr` from its `Get()` method once the
+// corresponding actor object has been destroyed.
+//
+// When calling a `Recv` method, IPC will hold a `ActorLifecycleProxy` reference
+// to the target actor, meaning that well-behaved actors can behave as though a
+// strong reference is being held.
+//
+// Generic IPC code MUST treat ActorLifecycleProxy references as weak
+// references!
+class ActorLifecycleProxy {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_ONEVENTTARGET(ActorLifecycleProxy)
+
+  IProtocol* Get() { return mActor; }
+
+  WeakActorLifecycleProxy* GetWeakProxy();
+
+ private:
+  friend class IProtocol;
+
+  explicit ActorLifecycleProxy(IProtocol* aActor);
+  ~ActorLifecycleProxy();
+
+  ActorLifecycleProxy(const ActorLifecycleProxy&) = delete;
+  ActorLifecycleProxy& operator=(const ActorLifecycleProxy&) = delete;
+
+  IProtocol* MOZ_NON_OWNING_REF mActor;
+
+  // Hold a reference to the actor's manager's ActorLifecycleProxy to help
+  // prevent it from dying while we're still alive!
+  RefPtr<ActorLifecycleProxy> mManager;
+
+  // When requested, the current self-referencing weak reference for this
+  // ActorLifecycleProxy.
+  RefPtr<WeakActorLifecycleProxy> mWeakProxy;
+};
+
+// Unlike ActorLifecycleProxy, WeakActorLifecycleProxy only holds a weak
+// reference to both the proxy and the actual actor, meaning that holding this
+// type will not attempt to keep the actor object alive.
+//
+// This type is safe to hold on threads other than the actor's thread, but is
+// _NOT_ safe to access on other threads, as actors and ActorLifecycleProxy
+// objects are not threadsafe.
+class WeakActorLifecycleProxy final {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WeakActorLifecycleProxy)
+
+  // May only be called on the actor's event target.
+  // Will return `nullptr` if the actor has already been destroyed from IPC's
+  // point of view.
+  IProtocol* Get() const;
+
+  // Safe to call on any thread.
+  nsISerialEventTarget* ActorEventTarget() const { return mActorEventTarget; }
+
+ private:
+  friend class ActorLifecycleProxy;
+
+  explicit WeakActorLifecycleProxy(ActorLifecycleProxy* aProxy);
+  ~WeakActorLifecycleProxy();
+
+  WeakActorLifecycleProxy(const WeakActorLifecycleProxy&) = delete;
+  WeakActorLifecycleProxy& operator=(const WeakActorLifecycleProxy&) = delete;
+
+  // This field may only be accessed on the actor's thread, and will be
+  // automatically cleared when the ActorLifecycleProxy is destroyed.
+  ActorLifecycleProxy* MOZ_NON_OWNING_REF mProxy;
+
+  // The serial event target which owns the actor, and is the only thread where
+  // it is OK to access the ActorLifecycleProxy.
+  const nsCOMPtr<nsISerialEventTarget> mActorEventTarget;
+};
+
+class IPDLResolverInner final {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING_WITH_DESTROY(IPDLResolverInner,
+                                                     Destroy())
+
+  explicit IPDLResolverInner(UniquePtr<IPC::Message> aReply, IProtocol* aActor);
+
+  template <typename F>
+  void Resolve(F&& aWrite) {
+    ResolveOrReject(true, aWrite);
+  }
+
+ private:
+  void ResolveOrReject(bool aResolve,
+                       FunctionRef<void(IPC::Message*, IProtocol*)> aWrite);
+
+  void Destroy();
+  ~IPDLResolverInner();
+
+  UniquePtr<IPC::Message> mReply;
+  RefPtr<WeakActorLifecycleProxy> mWeakProxy;
+};
+
+}  // namespace ipc
+
+template <typename Protocol>
+class ManagedContainer {
+ public:
+  using iterator = typename nsTArray<Protocol*>::const_iterator;
+
+  iterator begin() const { return mArray.begin(); }
+  iterator end() const { return mArray.end(); }
+  iterator cbegin() const { return begin(); }
+  iterator cend() const { return end(); }
+
+  bool IsEmpty() const { return mArray.IsEmpty(); }
+  uint32_t Count() const { return mArray.Length(); }
+
+  void ToArray(nsTArray<Protocol*>& aArray) const {
+    aArray.AppendElements(mArray);
+  }
+
+  bool EnsureRemoved(Protocol* aElement) {
+    return mArray.RemoveElementSorted(aElement);
+  }
+
+  void Insert(Protocol* aElement) {
+    // Equivalent to `InsertElementSorted`, avoiding inserting a duplicate
+    // element.
+    size_t index = mArray.IndexOfFirstElementGt(aElement);
+    if (index == 0 || mArray[index - 1] != aElement) {
+      mArray.InsertElementAt(index, aElement);
+    }
+  }
+
+  void Clear() { mArray.Clear(); }
+
+ private:
+  nsTArray<Protocol*> mArray;
+};
+
+template <typename Protocol>
+Protocol* LoneManagedOrNullAsserts(
+    const ManagedContainer<Protocol>& aManagees) {
+  if (aManagees.IsEmpty()) {
+    return nullptr;
+  }
+  MOZ_ASSERT(aManagees.Count() == 1);
+  return *aManagees.cbegin();
+}
+
+template <typename Protocol>
+Protocol* SingleManagedOrNull(const ManagedContainer<Protocol>& aManagees) {
+  if (aManagees.Count() != 1) {
+    return nullptr;
+  }
+  return *aManagees.cbegin();
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_ProtocolUtils_h
diff --git a/ipc/glue/RandomAccessStreamParams.ipdlh b/ipc/glue/RandomAccessStreamParams.ipdlh
new file mode 100644
index 0000000000..8bcf528af2
--- /dev/null
+++ b/ipc/glue/RandomAccessStreamParams.ipdlh
@@ -0,0 +1,32 @@
+/* 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 IPCQuotaObject;
+
+namespace mozilla {
+namespace ipc {
+
+// Use RandomAccessStreamParams in your ipdl to represent serialized
+// nsIRandomAccessStreams. Then use SerializeRandomAccessStream from
+// RandomAccessStreamUtils.h to perform the serialization.
+struct FileRandomAccessStreamParams
+{
+  FileDescriptor fileDescriptor;
+  int32_t behaviorFlags;
+};
+
+struct LimitingFileRandomAccessStreamParams
+{
+  FileRandomAccessStreamParams fileRandomAccessStreamParams;
+  IPCQuotaObject quotaObject;
+};
+
+union RandomAccessStreamParams
+{
+  FileRandomAccessStreamParams;
+  LimitingFileRandomAccessStreamParams;
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/RandomAccessStreamUtils.cpp b/ipc/glue/RandomAccessStreamUtils.cpp
new file mode 100644
index 0000000000..d5e66daae6
--- /dev/null
+++ b/ipc/glue/RandomAccessStreamUtils.cpp
@@ -0,0 +1,88 @@
+/* -*- 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 "RandomAccessStreamUtils.h"
+
+#include "mozilla/NotNull.h"
+#include "mozilla/Result.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/dom/quota/FileStreams.h"
+#include "mozilla/ipc/RandomAccessStreamParams.h"
+#include "nsFileStreams.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIRandomAccessStream.h"
+
+namespace mozilla::ipc {
+
+RandomAccessStreamParams SerializeRandomAccessStream(
+    MovingNotNull<nsCOMPtr<nsIRandomAccessStream>> aStream,
+    nsIInterfaceRequestor* aCallbacks) {
+  NotNull<nsCOMPtr<nsIRandomAccessStream>> stream = std::move(aStream);
+
+  RandomAccessStreamParams streamParams = stream->Serialize(aCallbacks);
+
+  MOZ_ASSERT(streamParams.type() != RandomAccessStreamParams::T__None);
+
+  return streamParams;
+}
+
+Maybe<RandomAccessStreamParams> SerializeRandomAccessStream(
+    nsCOMPtr<nsIRandomAccessStream> aStream,
+    nsIInterfaceRequestor* aCallbacks) {
+  if (!aStream) {
+    return Nothing();
+  }
+
+  return Some(SerializeRandomAccessStream(
+      WrapMovingNotNullUnchecked(std::move(aStream)), aCallbacks));
+}
+
+Result<MovingNotNull<nsCOMPtr<nsIRandomAccessStream>>, bool>
+DeserializeRandomAccessStream(RandomAccessStreamParams& aStreamParams) {
+  nsCOMPtr<nsIRandomAccessStream> stream;
+
+  switch (aStreamParams.type()) {
+    case RandomAccessStreamParams::TFileRandomAccessStreamParams:
+      nsFileRandomAccessStream::Create(NS_GET_IID(nsIFileRandomAccessStream),
+                                       getter_AddRefs(stream));
+      break;
+
+    case RandomAccessStreamParams::TLimitingFileRandomAccessStreamParams:
+      stream = new dom::quota::FileRandomAccessStream();
+      break;
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unknown params!");
+      return Err(false);
+  }
+
+  MOZ_ASSERT(stream);
+
+  if (!stream->Deserialize(aStreamParams)) {
+    MOZ_ASSERT_UNREACHABLE("Deserialize failed!");
+    return Err(false);
+  }
+
+  return WrapMovingNotNullUnchecked(std::move(stream));
+}
+
+Result<nsCOMPtr<nsIRandomAccessStream>, bool> DeserializeRandomAccessStream(
+    Maybe<RandomAccessStreamParams>& aStreamParams) {
+  if (aStreamParams.isNothing()) {
+    return nsCOMPtr<nsIRandomAccessStream>();
+  }
+
+  auto res = DeserializeRandomAccessStream(aStreamParams.ref());
+  if (res.isErr()) {
+    return res.propagateErr();
+  }
+
+  MovingNotNull<nsCOMPtr<nsIRandomAccessStream>> stream = res.unwrap();
+
+  return std::move(stream).unwrapBasePtr();
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/RandomAccessStreamUtils.h b/ipc/glue/RandomAccessStreamUtils.h
new file mode 100644
index 0000000000..3ca79537eb
--- /dev/null
+++ b/ipc/glue/RandomAccessStreamUtils.h
@@ -0,0 +1,50 @@
+/* -*- 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_ipc_RandomAccessStreamUtils_h
+#define mozilla_ipc_RandomAccessStreamUtils_h
+
+template <class T>
+class nsCOMPtr;
+
+class nsIInterfaceRequestor;
+class nsIRandomAccessStream;
+
+namespace mozilla {
+
+template <class T>
+class Maybe;
+
+template <typename T>
+class MovingNotNull;
+
+template <typename V, typename E>
+class Result;
+
+namespace ipc {
+
+class RandomAccessStreamParams;
+
+// Serialize an nsIRandomAccessStream to be sent over IPC infallibly.
+RandomAccessStreamParams SerializeRandomAccessStream(
+    MovingNotNull<nsCOMPtr<nsIRandomAccessStream>> aStream,
+    nsIInterfaceRequestor* aCallbacks);
+
+Maybe<RandomAccessStreamParams> SerializeRandomAccessStream(
+    nsCOMPtr<nsIRandomAccessStream> aStream, nsIInterfaceRequestor* aCallbacks);
+
+// Deserialize an nsIRandomAccessStream received from an actor call.  These
+// methods work in both the child and parent.
+Result<MovingNotNull<nsCOMPtr<nsIRandomAccessStream>>, bool>
+DeserializeRandomAccessStream(RandomAccessStreamParams& aStreamParams);
+
+Result<nsCOMPtr<nsIRandomAccessStream>, bool> DeserializeRandomAccessStream(
+    Maybe<RandomAccessStreamParams>& aStreamParams);
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_RandomAccessStreamUtils_h
diff --git a/ipc/glue/RawShmem.cpp b/ipc/glue/RawShmem.cpp
new file mode 100644
index 0000000000..bfb47c0832
--- /dev/null
+++ b/ipc/glue/RawShmem.cpp
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RawShmem.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+
+namespace mozilla::ipc {
+
+UnsafeSharedMemoryHandle::UnsafeSharedMemoryHandle()
+    : mHandle(ipc::SharedMemoryBasic::NULLHandle()), mSize(0) {}
+
+UnsafeSharedMemoryHandle::UnsafeSharedMemoryHandle(
+    UnsafeSharedMemoryHandle&& aOther) noexcept
+    : mHandle(std::move(aOther.mHandle)), mSize(aOther.mSize) {
+  aOther.mHandle = ipc::SharedMemoryBasic::NULLHandle();
+  aOther.mSize = 0;
+}
+
+UnsafeSharedMemoryHandle& UnsafeSharedMemoryHandle::operator=(
+    UnsafeSharedMemoryHandle&& aOther) noexcept {
+  if (this == &aOther) {
+    return *this;
+  }
+
+  mHandle = std::move(aOther.mHandle);
+  mSize = aOther.mSize;
+  aOther.mHandle = ipc::SharedMemoryBasic::NULLHandle();
+  aOther.mSize = 0;
+  return *this;
+}
+
+Maybe<std::pair<UnsafeSharedMemoryHandle, WritableSharedMemoryMapping>>
+UnsafeSharedMemoryHandle::CreateAndMap(size_t aSize) {
+  if (aSize == 0) {
+    return Some(std::make_pair(UnsafeSharedMemoryHandle(),
+                               WritableSharedMemoryMapping()));
+  }
+
+  RefPtr<ipc::SharedMemoryBasic> shm = MakeAndAddRef<ipc::SharedMemoryBasic>();
+  if (NS_WARN_IF(!shm->Create(aSize)) || NS_WARN_IF(!shm->Map(aSize))) {
+    return Nothing();
+  }
+
+  // TODO(bug 1797039): At the moment the handle/mapping distinction is
+  // implemented on top of a single class SharedMemoryBasic. It leads to a few
+  // awkward or sub-optimal things such as how the following few lines clone
+  // then close the handle. It would be better to separate the underlying
+  // implementation or steal the handle to avoid cloning it.
+  auto handle = shm->CloneHandle();
+
+  shm->CloseHandle();
+  auto size = shm->Size();
+
+  return Some(std::make_pair(UnsafeSharedMemoryHandle(std::move(handle), size),
+                             WritableSharedMemoryMapping(std::move(shm))));
+}
+
+WritableSharedMemoryMapping::WritableSharedMemoryMapping(
+    RefPtr<ipc::SharedMemoryBasic>&& aRef)
+    : mRef(aRef) {}
+
+Maybe<WritableSharedMemoryMapping> WritableSharedMemoryMapping::Open(
+    UnsafeSharedMemoryHandle aHandle) {
+  if (aHandle.mSize == 0) {
+    return Some(WritableSharedMemoryMapping(nullptr));
+  }
+
+  RefPtr<ipc::SharedMemoryBasic> shm = MakeAndAddRef<ipc::SharedMemoryBasic>();
+  if (NS_WARN_IF(!shm->SetHandle(std::move(aHandle.mHandle),
+                                 ipc::SharedMemory::RightsReadWrite)) ||
+      NS_WARN_IF(!shm->Map(aHandle.mSize))) {
+    return Nothing();
+  }
+
+  shm->CloseHandle();
+
+  return Some(WritableSharedMemoryMapping(std::move(shm)));
+}
+
+size_t WritableSharedMemoryMapping::Size() const {
+  if (!mRef) {
+    return 0;
+  }
+
+  return mRef->Size();
+}
+
+Span<uint8_t> WritableSharedMemoryMapping::Bytes() {
+  if (!mRef) {
+    return Span<uint8_t>();
+  }
+
+  uint8_t* mem = static_cast<uint8_t*>(mRef->memory());
+  return Span(mem, mRef->Size());
+}
+
+}  // namespace mozilla::ipc
+
+namespace IPC {
+auto ParamTraits<mozilla::ipc::UnsafeSharedMemoryHandle>::Write(
+    IPC::MessageWriter* aWriter, paramType&& aVar) -> void {
+  IPC::WriteParam(aWriter, std::move(aVar.mHandle));
+  IPC::WriteParam(aWriter, aVar.mSize);
+}
+
+auto ParamTraits<mozilla::ipc::UnsafeSharedMemoryHandle>::Read(
+    IPC::MessageReader* aReader, paramType* aVar) -> bool {
+  return IPC::ReadParam(aReader, &aVar->mHandle) &&
+         IPC::ReadParam(aReader, &aVar->mSize);
+}
+
+}  // namespace IPC
diff --git a/ipc/glue/RawShmem.h b/ipc/glue/RawShmem.h
new file mode 100644
index 0000000000..cebc59e924
--- /dev/null
+++ b/ipc/glue/RawShmem.h
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_IPC_RAWSHMEM_H_
+#define MOZILLA_IPC_RAWSHMEM_H_
+
+#include "mozilla/ipc/SharedMemoryBasic.h"
+#include "mozilla/Span.h"
+#include <utility>
+
+namespace mozilla::ipc {
+
+class WritableSharedMemoryMapping;
+
+/// A handle to shared memory.
+///
+/// See the doc comment for `WritableSharedMemoryMapping` below.
+class UnsafeSharedMemoryHandle {
+  friend class WritableSharedMemoryMapping;
+  friend struct IPC::ParamTraits<UnsafeSharedMemoryHandle>;
+
+ public:
+  UnsafeSharedMemoryHandle();
+  UnsafeSharedMemoryHandle(UnsafeSharedMemoryHandle&& aOther) noexcept;
+  UnsafeSharedMemoryHandle& operator=(
+      UnsafeSharedMemoryHandle&& aOther) noexcept;
+
+  /// Attempts to allocate a shmem.
+  ///
+  /// Returns `Nothing()` if allocation fails.
+  /// If `aSize` is zero, a valid empty WritableSharedMemoryMapping is returned.
+  static Maybe<std::pair<UnsafeSharedMemoryHandle, WritableSharedMemoryMapping>>
+  CreateAndMap(size_t aSize);
+
+ private:
+  UnsafeSharedMemoryHandle(SharedMemoryBasic::Handle&& aHandle, uint64_t aSize)
+      : mHandle(std::move(aHandle)), mSize(aSize) {}
+
+  SharedMemoryBasic::Handle mHandle;
+  uint64_t mSize;
+};
+
+/// A Shared memory buffer mapping.
+///
+/// Unlike `ipc::Shmem`, the underlying shared memory buffer on each side of
+/// the process boundary is only deallocated with there respective
+/// `WritableSharedMemoryMapping`.
+///
+/// ## Usage
+///
+/// Typical usage goes as follows:
+/// - Allocate the memory using `UnsafeSharedMemoryHandle::Create`, returning a
+///   handle and a mapping.
+/// - Send the handle to the other process using an IPDL message.
+/// - On the other process, map the shared memory by creating
+///   WritableSharedMemoryMapping via `WritableSharedMemoryMapping::Open` and
+///   the received handle.
+///
+/// Do not send the shared memory handle again, it is only intended to establish
+/// the mapping on each side during initialization. The user of this class is
+/// responsible for managing the lifetime of the buffers on each side, as well
+/// as their identity, by for example storing them in hash map and referring to
+/// them via IDs in IPDL message if need be.
+///
+/// ## Empty shmems
+///
+/// An empty WritableSharedMemoryMapping is one that was created with size zero.
+/// It is analogous to a null RefPtr. It can be used like a non-empty shmem,
+/// including sending the handle and openning it on another process (resulting
+/// in an empty mapping on the other side).
+class WritableSharedMemoryMapping {
+  friend class UnsafeSharedMemoryHandle;
+
+ public:
+  WritableSharedMemoryMapping() = default;
+
+  WritableSharedMemoryMapping(WritableSharedMemoryMapping&& aMoved) = default;
+
+  WritableSharedMemoryMapping& operator=(WritableSharedMemoryMapping&& aMoved) =
+      default;
+
+  /// Open the shmem and immediately close the handle.
+  static Maybe<WritableSharedMemoryMapping> Open(
+      UnsafeSharedMemoryHandle aHandle);
+
+  // Returns the size in bytes.
+  size_t Size() const;
+
+  // Returns the shared memory as byte range.
+  Span<uint8_t> Bytes();
+
+ private:
+  explicit WritableSharedMemoryMapping(
+      RefPtr<mozilla::ipc::SharedMemoryBasic>&& aRef);
+
+  RefPtr<mozilla::ipc::SharedMemoryBasic> mRef;
+};
+
+}  // namespace mozilla::ipc
+
+namespace IPC {
+template <>
+struct ParamTraits<mozilla::ipc::UnsafeSharedMemoryHandle> {
+  typedef mozilla::ipc::UnsafeSharedMemoryHandle paramType;
+  static void Write(IPC::MessageWriter* aWriter, paramType&& aVar);
+  static bool Read(IPC::MessageReader* aReader, paramType* aVar);
+};
+
+}  // namespace IPC
+
+#endif
diff --git a/ipc/glue/ScopedPort.cpp b/ipc/glue/ScopedPort.cpp
new file mode 100644
index 0000000000..e874796fb2
--- /dev/null
+++ b/ipc/glue/ScopedPort.cpp
@@ -0,0 +1,77 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ipc/ScopedPort.h"
+#include "mozilla/ipc/NodeController.h"
+#include "chrome/common/ipc_message_utils.h"
+
+namespace mozilla::ipc {
+
+void ScopedPort::Reset() {
+  if (mValid) {
+    mController->ClosePort(mPort);
+  }
+  mValid = false;
+  mPort = {};
+  mController = nullptr;
+}
+
+auto ScopedPort::Release() -> PortRef {
+  if (!mValid) {
+    return {};
+  }
+  mValid = false;
+  mController = nullptr;
+  return std::exchange(mPort, PortRef{});
+}
+
+ScopedPort::ScopedPort() = default;
+
+ScopedPort::~ScopedPort() { Reset(); }
+
+ScopedPort::ScopedPort(PortRef aPort, NodeController* aController)
+    : mValid(true), mPort(std::move(aPort)), mController(aController) {
+  MOZ_ASSERT(mPort.is_valid() && mController);
+}
+
+ScopedPort::ScopedPort(ScopedPort&& aOther)
+    : mValid(std::exchange(aOther.mValid, false)),
+      mPort(std::move(aOther.mPort)),
+      mController(std::move(aOther.mController)) {}
+
+ScopedPort& ScopedPort::operator=(ScopedPort&& aOther) {
+  if (this != &aOther) {
+    Reset();
+    mValid = std::exchange(aOther.mValid, false);
+    mPort = std::move(aOther.mPort);
+    mController = std::move(aOther.mController);
+  }
+  return *this;
+}
+
+}  // namespace mozilla::ipc
+
+void IPC::ParamTraits<mozilla::ipc::ScopedPort>::Write(MessageWriter* aWriter,
+                                                       paramType&& aParam) {
+  aWriter->WriteBool(aParam.IsValid());
+  if (!aParam.IsValid()) {
+    return;
+  }
+  aWriter->WritePort(std::move(aParam));
+}
+
+bool IPC::ParamTraits<mozilla::ipc::ScopedPort>::Read(MessageReader* aReader,
+                                                      paramType* aResult) {
+  bool isValid = false;
+  if (!aReader->ReadBool(&isValid)) {
+    return false;
+  }
+  if (!isValid) {
+    *aResult = {};
+    return true;
+  }
+  return aReader->ConsumePort(aResult);
+}
diff --git a/ipc/glue/ScopedPort.h b/ipc/glue/ScopedPort.h
new file mode 100644
index 0000000000..e683ba894e
--- /dev/null
+++ b/ipc/glue/ScopedPort.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 https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_RawEndpoint_h
+#define mozilla_ipc_RawEndpoint_h
+
+#include "mojo/core/ports/port_ref.h"
+
+namespace mozilla::ipc {
+
+class NodeController;
+
+/// A uniquely owned raw IPC endpoint, connected to our peers over the node
+/// controller. This type can be sent over IPC channels to establish
+/// connections.
+///
+/// In general, prefer using Endpoint over ScopedPort for type safety reasons.
+class ScopedPort {
+  using PortName = mojo::core::ports::PortName;
+  using PortRef = mojo::core::ports::PortRef;
+
+ public:
+  ScopedPort();
+  ~ScopedPort();
+
+  ScopedPort(PortRef aPort, NodeController* aController);
+
+  ScopedPort(ScopedPort&& aOther);
+  ScopedPort(const ScopedPort&) = delete;
+
+  ScopedPort& operator=(ScopedPort&& aOther);
+  ScopedPort& operator=(const ScopedPort&) = delete;
+
+  // Allow checking if this `ScopedPort` is valid or not.
+  bool IsValid() const { return mValid; }
+  explicit operator bool() const { return IsValid(); }
+
+  // Underlying port and controller which are used by this ScopedPort.
+  const PortName& Name() const { return mPort.name(); }
+  const PortRef& Port() const { return mPort; }
+  NodeController* Controller() const { return mController; }
+
+  // Release ownership over the contained `ScopedPort`, meaning that it will
+  // not be closed when this ScopedPort is destroyed. This will make the
+  // endpoint invalid.
+  PortRef Release();
+
+ private:
+  void Reset();
+
+  bool mValid = false;
+  PortRef mPort;
+  RefPtr<NodeController> mController;
+
+  // NOTE: This type does not contain PID information about the other process,
+  // which will need to be sent separately if necessary.
+};
+
+}  // namespace mozilla::ipc
+
+namespace IPC {
+
+template <typename T>
+struct ParamTraits;
+
+template <>
+struct ParamTraits<mozilla::ipc::ScopedPort> {
+  using paramType = mozilla::ipc::ScopedPort;
+
+  static void Write(MessageWriter* aWriter, paramType&& aParam);
+  static bool Read(MessageReader* aReader, paramType* aResult);
+};
+
+}  // namespace IPC
+
+#endif
diff --git a/ipc/glue/SerializedStructuredCloneBuffer.cpp b/ipc/glue/SerializedStructuredCloneBuffer.cpp
new file mode 100644
index 0000000000..9cad1ed826
--- /dev/null
+++ b/ipc/glue/SerializedStructuredCloneBuffer.cpp
@@ -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/. */
+
+#include "mozilla/ipc/SerializedStructuredCloneBuffer.h"
+#include "js/StructuredClone.h"
+
+namespace IPC {
+
+void ParamTraits<JSStructuredCloneData>::Write(MessageWriter* aWriter,
+                                               const paramType& aParam) {
+  MOZ_ASSERT(!(aParam.Size() % sizeof(uint64_t)));
+
+  // We can only construct shared memory regions up to 4Gb in size, making that
+  // the maximum possible JSStructuredCloneData size.
+  mozilla::CheckedUint32 size = aParam.Size();
+  if (!size.isValid()) {
+    aWriter->FatalError("JSStructuredCloneData over 4Gb in size");
+    return;
+  }
+  WriteParam(aWriter, size.value());
+
+  MessageBufferWriter bufWriter(aWriter, size.value());
+  aParam.ForEachDataChunk([&](const char* aData, size_t aSize) {
+    return bufWriter.WriteBytes(aData, aSize);
+  });
+}
+
+bool ParamTraits<JSStructuredCloneData>::Read(MessageReader* aReader,
+                                              paramType* aResult) {
+  uint32_t length = 0;
+  if (!ReadParam(aReader, &length)) {
+    aReader->FatalError("JSStructuredCloneData length read failed");
+    return false;
+  }
+  MOZ_ASSERT(!(length % sizeof(uint64_t)));
+
+  // Borrowing is not suitable to use for IPC to hand out data because we often
+  // want to store the data somewhere for processing after IPC has released the
+  // underlying buffers.
+  //
+  // This deserializer previously used a mechanism to transfer ownership over
+  // the underlying buffers from IPC into the JSStructuredCloneData. This was
+  // removed when support for serializing over shared memory was added, as the
+  // benefit for avoiding copies was limited due to it only functioning for
+  // buffers under 64k in size (as larger buffers would be serialized using
+  // shared memory), and it added substantial complexity to the BufferList type
+  // and the IPC serialization layer due to things like buffer alignment. This
+  // can be revisited in the future if it turns out to be a noticable
+  // performance regression. (bug 1783242)
+
+  mozilla::BufferList<js::SystemAllocPolicy> buffers(0, 0, 4096);
+  MessageBufferReader bufReader(aReader, length);
+  uint32_t read = 0;
+  while (read < length) {
+    size_t bufLen;
+    char* buf = buffers.AllocateBytes(length - read, &bufLen);
+    if (!buf) {
+      // Would be nice to allow actor to control behaviour here (bug 1784307)
+      NS_ABORT_OOM(length - read);
+      return false;
+    }
+    if (!bufReader.ReadBytesInto(buf, bufLen)) {
+      aReader->FatalError("JSStructuredCloneData ReadBytesInto failed");
+      return false;
+    }
+    read += bufLen;
+  }
+
+  MOZ_ASSERT(read == length);
+  *aResult = JSStructuredCloneData(
+      std::move(buffers), JS::StructuredCloneScope::DifferentProcess,
+      OwnTransferablePolicy::IgnoreTransferablesIfAny);
+  return true;
+}
+
+}  // namespace IPC
diff --git a/ipc/glue/SerializedStructuredCloneBuffer.h b/ipc/glue/SerializedStructuredCloneBuffer.h
new file mode 100644
index 0000000000..ed4e404dbc
--- /dev/null
+++ b/ipc/glue/SerializedStructuredCloneBuffer.h
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __IPC_GLUE_SERIALIZEDSTRUCTUREDCLONEBUFFER_H__
+#define __IPC_GLUE_SERIALIZEDSTRUCTUREDCLONEBUFFER_H__
+
+#include <algorithm>
+#include <cstdint>
+#include <cstdlib>
+#include <string>
+#include <utility>
+#include "chrome/common/ipc_message.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "js/AllocPolicy.h"
+#include "js/StructuredClone.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/BufferList.h"
+#include "mozilla/Vector.h"
+#include "mozilla/mozalloc.h"
+class PickleIterator;
+
+namespace mozilla {
+template <typename...>
+class Variant;
+
+namespace detail {
+template <typename...>
+struct VariantTag;
+}
+}  // namespace mozilla
+
+namespace mozilla {
+
+struct SerializedStructuredCloneBuffer final {
+  SerializedStructuredCloneBuffer() = default;
+
+  SerializedStructuredCloneBuffer(SerializedStructuredCloneBuffer&&) = default;
+  SerializedStructuredCloneBuffer& operator=(
+      SerializedStructuredCloneBuffer&&) = default;
+
+  SerializedStructuredCloneBuffer(const SerializedStructuredCloneBuffer&) =
+      delete;
+  SerializedStructuredCloneBuffer& operator=(
+      const SerializedStructuredCloneBuffer& aOther) = delete;
+
+  bool operator==(const SerializedStructuredCloneBuffer& aOther) const {
+    // The copy assignment operator and the equality operator are
+    // needed by the IPDL generated code. We relied on the copy
+    // assignment operator at some places but we never use the
+    // equality operator.
+    return false;
+  }
+
+  JSStructuredCloneData data{JS::StructuredCloneScope::Unassigned};
+};
+
+}  // namespace mozilla
+
+namespace IPC {
+template <>
+struct ParamTraits<JSStructuredCloneData> {
+  typedef JSStructuredCloneData paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam);
+
+  static bool Read(MessageReader* aReader, paramType* aResult);
+};
+
+template <>
+struct ParamTraits<mozilla::SerializedStructuredCloneBuffer> {
+  typedef mozilla::SerializedStructuredCloneBuffer paramType;
+
+  static void Write(MessageWriter* aWriter, const paramType& aParam) {
+    WriteParam(aWriter, aParam.data);
+  }
+
+  static bool Read(MessageReader* aReader, paramType* aResult) {
+    return ReadParam(aReader, &aResult->data);
+  }
+};
+
+}  // namespace IPC
+
+#endif /* __IPC_GLUE_SERIALIZEDSTRUCTUREDCLONEBUFFER_H__ */
diff --git a/ipc/glue/SharedMemory.cpp b/ipc/glue/SharedMemory.cpp
new file mode 100644
index 0000000000..4761746658
--- /dev/null
+++ b/ipc/glue/SharedMemory.cpp
@@ -0,0 +1,84 @@
+/* -*- 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 <math.h>
+
+#include "nsString.h"
+#include "nsIMemoryReporter.h"
+#include "mozilla/ipc/SharedMemory.h"
+#include "mozilla/Atomics.h"
+
+namespace mozilla {
+namespace ipc {
+
+static Atomic<size_t> gShmemAllocated;
+static Atomic<size_t> gShmemMapped;
+
+class ShmemReporter final : public nsIMemoryReporter {
+  ~ShmemReporter() = default;
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  NS_IMETHOD
+  CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
+                 bool aAnonymize) override {
+    MOZ_COLLECT_REPORT(
+        "shmem-allocated", KIND_OTHER, UNITS_BYTES, gShmemAllocated,
+        "Memory shared with other processes that is accessible (but not "
+        "necessarily mapped).");
+
+    MOZ_COLLECT_REPORT(
+        "shmem-mapped", KIND_OTHER, UNITS_BYTES, gShmemMapped,
+        "Memory shared with other processes that is mapped into the address "
+        "space.");
+
+    return NS_OK;
+  }
+};
+
+NS_IMPL_ISUPPORTS(ShmemReporter, nsIMemoryReporter)
+
+SharedMemory::SharedMemory() : mAllocSize(0), mMappedSize(0) {
+  static Atomic<bool> registered;
+  if (registered.compareExchange(false, true)) {
+    RegisterStrongMemoryReporter(new ShmemReporter());
+  }
+}
+
+/*static*/
+size_t SharedMemory::PageAlignedSize(size_t aSize) {
+  size_t pageSize = SystemPageSize();
+  size_t nPagesNeeded = size_t(ceil(double(aSize) / double(pageSize)));
+  return pageSize * nPagesNeeded;
+}
+
+void SharedMemory::Created(size_t aNBytes) {
+  mAllocSize = aNBytes;
+  gShmemAllocated += mAllocSize;
+}
+
+void SharedMemory::Mapped(size_t aNBytes) {
+  mMappedSize = aNBytes;
+  gShmemMapped += mMappedSize;
+}
+
+void SharedMemory::Unmapped() {
+  MOZ_ASSERT(gShmemMapped >= mMappedSize, "Can't unmap more than mapped");
+  gShmemMapped -= mMappedSize;
+  mMappedSize = 0;
+}
+
+/*static*/
+void SharedMemory::Destroyed() {
+  MOZ_ASSERT(gShmemAllocated >= mAllocSize,
+             "Can't destroy more than allocated");
+  gShmemAllocated -= mAllocSize;
+  mAllocSize = 0;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/SharedMemory.h b/ipc/glue/SharedMemory.h
new file mode 100644
index 0000000000..820a1d8954
--- /dev/null
+++ b/ipc/glue/SharedMemory.h
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_SharedMemory_h
+#define mozilla_ipc_SharedMemory_h
+
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"  // NS_INLINE_DECL_REFCOUNTING
+#include "mozilla/Attributes.h"
+
+#include "base/process.h"
+#include "chrome/common/ipc_message_utils.h"
+
+//
+// This is a low-level wrapper around platform shared memory.  Don't
+// use it directly; use Shmem allocated through IPDL interfaces.
+//
+namespace {
+enum Rights { RightsNone = 0, RightsRead = 1 << 0, RightsWrite = 1 << 1 };
+}  // namespace
+
+namespace mozilla {
+
+namespace ipc {
+class SharedMemory;
+}  // namespace ipc
+
+namespace ipc {
+
+class SharedMemory {
+ protected:
+  virtual ~SharedMemory() {
+    Unmapped();
+    Destroyed();
+  }
+
+ public:
+  enum OpenRights {
+    RightsReadOnly = RightsRead,
+    RightsReadWrite = RightsRead | RightsWrite,
+  };
+
+  size_t Size() const { return mMappedSize; }
+
+  virtual void* memory() const = 0;
+
+  virtual bool Create(size_t size) = 0;
+  virtual bool Map(size_t nBytes, void* fixed_address = nullptr) = 0;
+  virtual void Unmap() = 0;
+
+  virtual void CloseHandle() = 0;
+
+  virtual bool WriteHandle(IPC::MessageWriter* aWriter) = 0;
+  virtual bool ReadHandle(IPC::MessageReader* aReader) = 0;
+
+  void Protect(char* aAddr, size_t aSize, int aRights) {
+    char* memStart = reinterpret_cast<char*>(memory());
+    if (!memStart) MOZ_CRASH("SharedMemory region points at NULL!");
+    char* memEnd = memStart + Size();
+
+    char* protStart = aAddr;
+    if (!protStart) MOZ_CRASH("trying to Protect() a NULL region!");
+    char* protEnd = protStart + aSize;
+
+    if (!(memStart <= protStart && protEnd <= memEnd))
+      MOZ_CRASH("attempt to Protect() a region outside this SharedMemory");
+
+    // checks alignment etc.
+    SystemProtect(aAddr, aSize, aRights);
+  }
+
+  // bug 1168843, compositor thread may create shared memory instances that are
+  // destroyed by main thread on shutdown, so this must use thread-safe RC to
+  // avoid hitting assertion
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedMemory)
+
+  static void SystemProtect(char* aAddr, size_t aSize, int aRights);
+  [[nodiscard]] static bool SystemProtectFallible(char* aAddr, size_t aSize,
+                                                  int aRights);
+  static size_t SystemPageSize();
+  static size_t PageAlignedSize(size_t aSize);
+
+ protected:
+  SharedMemory();
+
+  // Implementations should call these methods on shmem usage changes,
+  // but *only if* the OS-specific calls are known to have succeeded.
+  // The methods are expected to be called in the pattern
+  //
+  //   Created (Mapped Unmapped)* Destroy
+  //
+  // but this isn't checked.
+  void Created(size_t aNBytes);
+  void Mapped(size_t aNBytes);
+  void Unmapped();
+  void Destroyed();
+
+  // The size of the shmem region requested in Create(), if
+  // successful.  SharedMemory instances that are opened from a
+  // foreign handle have an alloc size of 0, even though they have
+  // access to the alloc-size information.
+  size_t mAllocSize;
+  // The size of the region mapped in Map(), if successful.  All
+  // SharedMemorys that are mapped have a non-zero mapped size.
+  size_t mMappedSize;
+};
+
+template <typename HandleImpl>
+class SharedMemoryCommon : public SharedMemory {
+ public:
+  typedef HandleImpl Handle;
+
+  virtual Handle CloneHandle() = 0;
+  virtual bool IsHandleValid(const Handle& aHandle) const = 0;
+  virtual bool SetHandle(Handle aHandle, OpenRights aRights) = 0;
+
+  virtual bool WriteHandle(IPC::MessageWriter* aWriter) override {
+    Handle handle = CloneHandle();
+    if (!handle) {
+      return false;
+    }
+    IPC::WriteParam(aWriter, std::move(handle));
+    return true;
+  }
+
+  virtual bool ReadHandle(IPC::MessageReader* aReader) override {
+    Handle handle;
+    return IPC::ReadParam(aReader, &handle) && IsHandleValid(handle) &&
+           SetHandle(std::move(handle), RightsReadWrite);
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_SharedMemory_h
diff --git a/ipc/glue/SharedMemoryBasic.h b/ipc/glue/SharedMemoryBasic.h
new file mode 100644
index 0000000000..13026be8b2
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic.h
@@ -0,0 +1,18 @@
+/* -*- 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_ipc_SharedMemoryBasic_h
+#define mozilla_ipc_SharedMemoryBasic_h
+
+#ifdef ANDROID
+#  include "mozilla/ipc/SharedMemoryBasic_android.h"
+#elif defined(XP_DARWIN)
+#  include "mozilla/ipc/SharedMemoryBasic_mach.h"
+#else
+#  include "mozilla/ipc/SharedMemoryBasic_chromium.h"
+#endif
+
+#endif  // ifndef mozilla_ipc_SharedMemoryBasic_h
diff --git a/ipc/glue/SharedMemoryBasic_android.cpp b/ipc/glue/SharedMemoryBasic_android.cpp
new file mode 100644
index 0000000000..5c8279da6d
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_android.cpp
@@ -0,0 +1,132 @@
+/* -*- 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 <android/log.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "base/process_util.h"
+
+#include "SharedMemoryBasic.h"
+
+#include "mozilla/Ashmem.h"
+
+namespace mozilla {
+namespace ipc {
+
+static void LogError(const char* what) {
+  __android_log_print(ANDROID_LOG_ERROR, "Gecko", "%s: %s (%d)", what,
+                      strerror(errno), errno);
+}
+
+SharedMemoryBasic::SharedMemoryBasic()
+    : mShmFd(-1), mMemory(nullptr), mOpenRights(RightsReadWrite) {}
+
+SharedMemoryBasic::~SharedMemoryBasic() {
+  Unmap();
+  CloseHandle();
+}
+
+bool SharedMemoryBasic::SetHandle(Handle aHandle, OpenRights aRights) {
+  MOZ_ASSERT(-1 == mShmFd, "Already Create()d");
+  mShmFd = aHandle.release();
+  mOpenRights = aRights;
+  return true;
+}
+
+bool SharedMemoryBasic::Create(size_t aNbytes) {
+  MOZ_ASSERT(-1 == mShmFd, "Already Create()d");
+
+  // Carve a new instance off of /dev/ashmem
+  int shmfd = mozilla::android::ashmem_create(nullptr, aNbytes);
+  if (-1 == shmfd) {
+    LogError("ShmemAndroid::Create():open");
+    return false;
+  }
+
+  mShmFd = shmfd;
+  Created(aNbytes);
+  return true;
+}
+
+bool SharedMemoryBasic::Map(size_t nBytes, void* fixed_address) {
+  MOZ_ASSERT(nullptr == mMemory, "Already Map()d");
+
+  int prot = PROT_READ;
+  if (mOpenRights == RightsReadWrite) {
+    prot |= PROT_WRITE;
+  }
+
+  // Don't use MAP_FIXED when a fixed_address was specified, since that can
+  // replace pages that are alread mapped at that address.
+  mMemory = mmap(fixed_address, nBytes, prot, MAP_SHARED, mShmFd, 0);
+
+  if (MAP_FAILED == mMemory) {
+    if (!fixed_address) {
+      LogError("ShmemAndroid::Map()");
+    }
+    mMemory = nullptr;
+    return false;
+  }
+
+  if (fixed_address && mMemory != fixed_address) {
+    if (munmap(mMemory, nBytes)) {
+      LogError("ShmemAndroid::Map():unmap");
+      mMemory = nullptr;
+      return false;
+    }
+  }
+
+  Mapped(nBytes);
+  return true;
+}
+
+void* SharedMemoryBasic::FindFreeAddressSpace(size_t size) {
+  void* memory =
+      mmap(NULL, size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  munmap(memory, size);
+  return memory != (void*)-1 ? memory : NULL;
+}
+
+auto SharedMemoryBasic::CloneHandle() -> Handle {
+  MOZ_ASSERT(mShmFd >= 0, "Should have been Create()d by now");
+
+  int shmfdDup = dup(mShmFd);
+  if (-1 == shmfdDup) {
+    LogError("ShmemAndroid::CloneHandle()");
+    return nullptr;
+  }
+
+  return mozilla::UniqueFileHandle(shmfdDup);
+}
+
+void SharedMemoryBasic::Unmap() {
+  if (!mMemory) {
+    return;
+  }
+
+  if (munmap(mMemory, Size())) {
+    LogError("ShmemAndroid::Unmap()");
+  }
+  mMemory = nullptr;
+}
+
+void SharedMemoryBasic::CloseHandle() {
+  if (mShmFd != -1) {
+    close(mShmFd);
+    mShmFd = -1;
+    mOpenRights = RightsReadWrite;
+  }
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/SharedMemoryBasic_android.h b/ipc/glue/SharedMemoryBasic_android.h
new file mode 100644
index 0000000000..0b9114e2ae
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_android.h
@@ -0,0 +1,72 @@
+/* -*- 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_ipc_SharedMemoryBasic_android_h
+#define mozilla_ipc_SharedMemoryBasic_android_h
+
+#include "mozilla/ipc/SharedMemory.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+#ifdef FUZZING
+#  include "mozilla/ipc/SharedMemoryFuzzer.h"
+#endif
+
+//
+// This is a low-level wrapper around platform shared memory.  Don't
+// use it directly; use Shmem allocated through IPDL interfaces.
+//
+
+namespace mozilla {
+namespace ipc {
+
+class SharedMemoryBasic final
+    : public SharedMemoryCommon<mozilla::UniqueFileHandle> {
+ public:
+  SharedMemoryBasic();
+
+  virtual bool SetHandle(Handle aHandle, OpenRights aRights) override;
+
+  virtual bool Create(size_t aNbytes) override;
+
+  virtual bool Map(size_t nBytes, void* fixed_address = nullptr) override;
+
+  virtual void Unmap() override;
+
+  virtual void CloseHandle() override;
+
+  virtual void* memory() const override {
+#ifdef FUZZING
+    return SharedMemoryFuzzer::MutateSharedMemory(mMemory, mAllocSize);
+#else
+    return mMemory;
+#endif
+  }
+
+  static Handle NULLHandle() { return Handle(); }
+
+  static void* FindFreeAddressSpace(size_t aSize);
+
+  virtual bool IsHandleValid(const Handle& aHandle) const override {
+    return aHandle != nullptr;
+  }
+
+  virtual Handle CloneHandle() override;
+
+ private:
+  ~SharedMemoryBasic();
+
+  // The /dev/ashmem fd we allocate.
+  int mShmFd;
+  // Pointer to mapped region, null if unmapped.
+  void* mMemory;
+  // Access rights to map an existing region with.
+  OpenRights mOpenRights;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_SharedMemoryBasic_android_h
diff --git a/ipc/glue/SharedMemoryBasic_chromium.h b/ipc/glue/SharedMemoryBasic_chromium.h
new file mode 100644
index 0000000000..c48898c47d
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_chromium.h
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_SharedMemoryBasic_chromium_h
+#define mozilla_ipc_SharedMemoryBasic_chromium_h
+
+#include "base/shared_memory.h"
+#include "mozilla/ipc/SharedMemory.h"
+
+#ifdef FUZZING
+#  include "mozilla/ipc/SharedMemoryFuzzer.h"
+#endif
+
+#include "nsDebug.h"
+
+//
+// This is a low-level wrapper around platform shared memory.  Don't
+// use it directly; use Shmem allocated through IPDL interfaces.
+//
+
+namespace mozilla {
+namespace ipc {
+
+class SharedMemoryBasic final
+    : public SharedMemoryCommon<base::SharedMemoryHandle> {
+ public:
+  SharedMemoryBasic() = default;
+
+  virtual bool SetHandle(Handle aHandle, OpenRights aRights) override {
+    return mSharedMemory.SetHandle(std::move(aHandle),
+                                   aRights == RightsReadOnly);
+  }
+
+  virtual bool Create(size_t aNbytes) override {
+    bool ok = mSharedMemory.Create(aNbytes);
+    if (ok) {
+      Created(aNbytes);
+    }
+    return ok;
+  }
+
+  virtual bool Map(size_t nBytes, void* fixed_address = nullptr) override {
+    bool ok = mSharedMemory.Map(nBytes, fixed_address);
+    if (ok) {
+      Mapped(nBytes);
+    }
+    return ok;
+  }
+
+  virtual void Unmap() override { mSharedMemory.Unmap(); }
+
+  virtual void CloseHandle() override { mSharedMemory.Close(false); }
+
+  virtual void* memory() const override {
+#ifdef FUZZING
+    return SharedMemoryFuzzer::MutateSharedMemory(mSharedMemory.memory(),
+                                                  mAllocSize);
+#else
+    return mSharedMemory.memory();
+#endif
+  }
+
+  static Handle NULLHandle() { return base::SharedMemory::NULLHandle(); }
+
+  virtual bool IsHandleValid(const Handle& aHandle) const override {
+    return base::SharedMemory::IsHandleValid(aHandle);
+  }
+
+  virtual Handle CloneHandle() override { return mSharedMemory.CloneHandle(); }
+
+  static void* FindFreeAddressSpace(size_t size) {
+    return base::SharedMemory::FindFreeAddressSpace(size);
+  }
+
+ private:
+  ~SharedMemoryBasic() = default;
+
+  base::SharedMemory mSharedMemory;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_SharedMemoryBasic_chromium_h
diff --git a/ipc/glue/SharedMemoryBasic_mach.h b/ipc/glue/SharedMemoryBasic_mach.h
new file mode 100644
index 0000000000..e487c99c84
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_mach.h
@@ -0,0 +1,75 @@
+/* -*- 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_ipc_SharedMemoryBasic_mach_h
+#define mozilla_ipc_SharedMemoryBasic_mach_h
+
+#include "base/process.h"
+
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/ipc/SharedMemory.h"
+#include <mach/port.h>
+
+#ifdef FUZZING
+#  include "mozilla/ipc/SharedMemoryFuzzer.h"
+#endif
+
+//
+// This is a low-level wrapper around platform shared memory.  Don't
+// use it directly; use Shmem allocated through IPDL interfaces.
+//
+
+class MachPortSender;
+class ReceivePort;
+
+namespace mozilla {
+namespace ipc {
+
+class SharedMemoryBasic final
+    : public SharedMemoryCommon<mozilla::UniqueMachSendRight> {
+ public:
+  SharedMemoryBasic();
+
+  virtual bool SetHandle(Handle aHandle, OpenRights aRights) override;
+
+  virtual bool Create(size_t aNbytes) override;
+
+  virtual bool Map(size_t nBytes, void* fixed_address = nullptr) override;
+
+  virtual void Unmap() override;
+
+  virtual void CloseHandle() override;
+
+  virtual void* memory() const override {
+#ifdef FUZZING
+    return SharedMemoryFuzzer::MutateSharedMemory(mMemory, mAllocSize);
+#else
+    return mMemory;
+#endif
+  }
+
+  static Handle NULLHandle() { return Handle(); }
+
+  static void* FindFreeAddressSpace(size_t aSize);
+
+  virtual bool IsHandleValid(const Handle& aHandle) const override;
+
+  virtual Handle CloneHandle() override;
+
+ private:
+  ~SharedMemoryBasic();
+
+  mozilla::UniqueMachSendRight mPort;
+  // Pointer to mapped region, null if unmapped.
+  void* mMemory;
+  // Access rights to map an existing region with.
+  OpenRights mOpenRights;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_SharedMemoryBasic_mach_h
diff --git a/ipc/glue/SharedMemoryBasic_mach.mm b/ipc/glue/SharedMemoryBasic_mach.mm
new file mode 100644
index 0000000000..af0d6e6245
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_mach.mm
@@ -0,0 +1,167 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=8 et :
+ */
+/* 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 <map>
+
+#include <mach/vm_map.h>
+#include <mach/mach_port.h>
+#if defined(XP_IOS)
+#  include <mach/vm_map.h>
+#  define mach_vm_address_t vm_address_t
+#  define mach_vm_map vm_map
+#  define mach_vm_read vm_read
+#  define mach_vm_region_recurse vm_region_recurse_64
+#  define mach_vm_size_t vm_size_t
+#else
+#  include <mach/mach_vm.h>
+#endif
+#include <pthread.h>
+#include <unistd.h>
+#include "SharedMemoryBasic.h"
+
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/Printf.h"
+#include "mozilla/StaticMutex.h"
+
+#ifdef DEBUG
+#  define LOG_ERROR(str, args...)                                  \
+    PR_BEGIN_MACRO                                                 \
+    mozilla::SmprintfPointer msg = mozilla::Smprintf(str, ##args); \
+    NS_WARNING(msg.get());                                         \
+    PR_END_MACRO
+#else
+#  define LOG_ERROR(str, args...) \
+    do { /* nothing */            \
+    } while (0)
+#endif
+
+namespace mozilla {
+namespace ipc {
+
+SharedMemoryBasic::SharedMemoryBasic()
+    : mPort(MACH_PORT_NULL), mMemory(nullptr), mOpenRights(RightsReadWrite) {}
+
+SharedMemoryBasic::~SharedMemoryBasic() {
+  Unmap();
+  CloseHandle();
+}
+
+bool SharedMemoryBasic::SetHandle(Handle aHandle, OpenRights aRights) {
+  MOZ_ASSERT(mPort == MACH_PORT_NULL, "already initialized");
+
+  mPort = std::move(aHandle);
+  mOpenRights = aRights;
+  return true;
+}
+
+static inline void* toPointer(mach_vm_address_t address) {
+  return reinterpret_cast<void*>(static_cast<uintptr_t>(address));
+}
+
+static inline mach_vm_address_t toVMAddress(void* pointer) {
+  return static_cast<mach_vm_address_t>(reinterpret_cast<uintptr_t>(pointer));
+}
+
+bool SharedMemoryBasic::Create(size_t size) {
+  MOZ_ASSERT(mPort == MACH_PORT_NULL, "already initialized");
+
+  memory_object_size_t memoryObjectSize = round_page(size);
+
+  kern_return_t kr = mach_make_memory_entry_64(mach_task_self(), &memoryObjectSize, 0,
+                                               MAP_MEM_NAMED_CREATE | VM_PROT_DEFAULT,
+                                               getter_Transfers(mPort), MACH_PORT_NULL);
+  if (kr != KERN_SUCCESS || memoryObjectSize < round_page(size)) {
+    LOG_ERROR("Failed to make memory entry (%zu bytes). %s (%x)\n", size, mach_error_string(kr),
+              kr);
+    CloseHandle();
+    return false;
+  }
+
+  Created(size);
+  return true;
+}
+
+bool SharedMemoryBasic::Map(size_t size, void* fixed_address) {
+  MOZ_ASSERT(mMemory == nullptr);
+
+  if (MACH_PORT_NULL == mPort) {
+    return false;
+  }
+
+  kern_return_t kr;
+  mach_vm_address_t address = toVMAddress(fixed_address);
+
+  vm_prot_t vmProtection = VM_PROT_READ;
+  if (mOpenRights == RightsReadWrite) {
+    vmProtection |= VM_PROT_WRITE;
+  }
+
+  kr = mach_vm_map(mach_task_self(), &address, round_page(size), 0,
+                   fixed_address ? VM_FLAGS_FIXED : VM_FLAGS_ANYWHERE, mPort.get(), 0, false,
+                   vmProtection, vmProtection, VM_INHERIT_NONE);
+  if (kr != KERN_SUCCESS) {
+    if (!fixed_address) {
+      LOG_ERROR("Failed to map shared memory (%zu bytes) into %x, port %x. %s (%x)\n", size,
+                mach_task_self(), mach_port_t(mPort.get()), mach_error_string(kr), kr);
+    }
+    return false;
+  }
+
+  if (fixed_address && fixed_address != toPointer(address)) {
+    kr = vm_deallocate(mach_task_self(), address, size);
+    if (kr != KERN_SUCCESS) {
+      LOG_ERROR("Failed to unmap shared memory at unsuitable address "
+                "(%zu bytes) from %x, port %x. %s (%x)\n",
+                size, mach_task_self(), mach_port_t(mPort.get()), mach_error_string(kr), kr);
+    }
+    return false;
+  }
+
+  mMemory = toPointer(address);
+  Mapped(size);
+  return true;
+}
+
+void* SharedMemoryBasic::FindFreeAddressSpace(size_t size) {
+  mach_vm_address_t address = 0;
+  size = round_page(size);
+  if (mach_vm_map(mach_task_self(), &address, size, 0, VM_FLAGS_ANYWHERE, MEMORY_OBJECT_NULL, 0,
+                  false, VM_PROT_NONE, VM_PROT_NONE, VM_INHERIT_NONE) != KERN_SUCCESS ||
+      vm_deallocate(mach_task_self(), address, size) != KERN_SUCCESS) {
+    return nullptr;
+  }
+  return toPointer(address);
+}
+
+auto SharedMemoryBasic::CloneHandle() -> Handle {
+  return mozilla::RetainMachSendRight(mPort.get());
+}
+
+void SharedMemoryBasic::Unmap() {
+  if (!mMemory) {
+    return;
+  }
+  vm_address_t address = toVMAddress(mMemory);
+  kern_return_t kr = vm_deallocate(mach_task_self(), address, round_page(mMappedSize));
+  if (kr != KERN_SUCCESS) {
+    LOG_ERROR("Failed to deallocate shared memory. %s (%x)\n", mach_error_string(kr), kr);
+    return;
+  }
+  mMemory = nullptr;
+}
+
+void SharedMemoryBasic::CloseHandle() {
+  if (mPort) {
+    mPort = nullptr;
+    mOpenRights = RightsReadWrite;
+  }
+}
+
+bool SharedMemoryBasic::IsHandleValid(const Handle& aHandle) const { return aHandle != nullptr; }
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/SharedMemory_posix.cpp b/ipc/glue/SharedMemory_posix.cpp
new file mode 100644
index 0000000000..b634058945
--- /dev/null
+++ b/ipc/glue/SharedMemory_posix.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 <sys/mman.h>  // mprotect
+#include <unistd.h>    // sysconf
+
+#include "mozilla/ipc/SharedMemory.h"
+
+#if defined(XP_MACOSX) && defined(__x86_64__)
+#  include "prenv.h"
+#endif
+
+namespace mozilla {
+namespace ipc {
+
+#if defined(XP_MACOSX) && defined(__x86_64__)
+std::atomic<size_t> sPageSizeOverride = 0;
+#endif
+
+void SharedMemory::SystemProtect(char* aAddr, size_t aSize, int aRights) {
+  if (!SystemProtectFallible(aAddr, aSize, aRights)) {
+    MOZ_CRASH("can't mprotect()");
+  }
+}
+
+bool SharedMemory::SystemProtectFallible(char* aAddr, size_t aSize,
+                                         int aRights) {
+  int flags = 0;
+  if (aRights & RightsRead) flags |= PROT_READ;
+  if (aRights & RightsWrite) flags |= PROT_WRITE;
+  if (RightsNone == aRights) flags = PROT_NONE;
+
+  return 0 == mprotect(aAddr, aSize, flags);
+}
+
+size_t SharedMemory::SystemPageSize() {
+#if defined(XP_MACOSX) && defined(__x86_64__)
+  if (sPageSizeOverride == 0) {
+    if (PR_GetEnv("MOZ_SHMEM_PAGESIZE_16K")) {
+      sPageSizeOverride = 16 * 1024;
+    } else {
+      sPageSizeOverride = sysconf(_SC_PAGESIZE);
+    }
+  }
+  return sPageSizeOverride;
+#else
+  return sysconf(_SC_PAGESIZE);
+#endif
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/SharedMemory_windows.cpp b/ipc/glue/SharedMemory_windows.cpp
new file mode 100644
index 0000000000..1cc93687af
--- /dev/null
+++ b/ipc/glue/SharedMemory_windows.cpp
@@ -0,0 +1,41 @@
+/* -*- 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 <windows.h>
+
+#include "mozilla/ipc/SharedMemory.h"
+
+namespace mozilla {
+namespace ipc {
+
+void SharedMemory::SystemProtect(char* aAddr, size_t aSize, int aRights) {
+  if (!SystemProtectFallible(aAddr, aSize, aRights)) {
+    MOZ_CRASH("can't VirtualProtect()");
+  }
+}
+
+bool SharedMemory::SystemProtectFallible(char* aAddr, size_t aSize,
+                                         int aRights) {
+  DWORD flags;
+  if ((aRights & RightsRead) && (aRights & RightsWrite))
+    flags = PAGE_READWRITE;
+  else if (aRights & RightsRead)
+    flags = PAGE_READONLY;
+  else
+    flags = PAGE_NOACCESS;
+
+  DWORD oldflags;
+  return VirtualProtect(aAddr, aSize, flags, &oldflags);
+}
+
+size_t SharedMemory::SystemPageSize() {
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/Shmem.cpp b/ipc/glue/Shmem.cpp
new file mode 100644
index 0000000000..775d852faa
--- /dev/null
+++ b/ipc/glue/Shmem.cpp
@@ -0,0 +1,458 @@
+/* -*- 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 "Shmem.h"
+
+#include "ProtocolUtils.h"
+#include "SharedMemoryBasic.h"
+#include "ShmemMessageUtils.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "mozilla/Unused.h"
+
+namespace mozilla {
+namespace ipc {
+
+class ShmemCreated : public IPC::Message {
+ private:
+  typedef Shmem::id_t id_t;
+
+ public:
+  ShmemCreated(int32_t routingId, id_t aIPDLId, size_t aSize)
+      : IPC::Message(
+            routingId, SHMEM_CREATED_MESSAGE_TYPE, 0,
+            HeaderFlags(NESTED_INSIDE_CPOW, CONTROL_PRIORITY, COMPRESSION_NONE,
+                        LAZY_SEND, NOT_CONSTRUCTOR, ASYNC, NOT_REPLY)) {
+    MOZ_RELEASE_ASSERT(aSize < std::numeric_limits<uint32_t>::max(),
+                       "Tried to create Shmem with size larger than 4GB");
+    IPC::MessageWriter writer(*this);
+    IPC::WriteParam(&writer, aIPDLId);
+    IPC::WriteParam(&writer, uint32_t(aSize));
+  }
+
+  static bool ReadInfo(IPC::MessageReader* aReader, id_t* aIPDLId,
+                       size_t* aSize) {
+    uint32_t size = 0;
+    if (!IPC::ReadParam(aReader, aIPDLId) || !IPC::ReadParam(aReader, &size)) {
+      return false;
+    }
+    *aSize = size;
+    return true;
+  }
+
+  void Log(const std::string& aPrefix, FILE* aOutf) const {
+    fputs("(special ShmemCreated msg)", aOutf);
+  }
+};
+
+class ShmemDestroyed : public IPC::Message {
+ private:
+  typedef Shmem::id_t id_t;
+
+ public:
+  ShmemDestroyed(int32_t routingId, id_t aIPDLId)
+      : IPC::Message(
+            routingId, SHMEM_DESTROYED_MESSAGE_TYPE, 0,
+            HeaderFlags(NOT_NESTED, NORMAL_PRIORITY, COMPRESSION_NONE,
+                        LAZY_SEND, NOT_CONSTRUCTOR, ASYNC, NOT_REPLY)) {
+    IPC::MessageWriter writer(*this);
+    IPC::WriteParam(&writer, aIPDLId);
+  }
+};
+
+static SharedMemory* NewSegment() { return new SharedMemoryBasic; }
+
+static already_AddRefed<SharedMemory> CreateSegment(size_t aNBytes,
+                                                    size_t aExtraSize) {
+  RefPtr<SharedMemory> segment = NewSegment();
+  if (!segment) {
+    return nullptr;
+  }
+  size_t size = SharedMemory::PageAlignedSize(aNBytes + aExtraSize);
+  if (!segment->Create(size) || !segment->Map(size)) {
+    return nullptr;
+  }
+  return segment.forget();
+}
+
+static already_AddRefed<SharedMemory> ReadSegment(
+    const IPC::Message& aDescriptor, Shmem::id_t* aId, size_t* aNBytes,
+    size_t aExtraSize) {
+  if (SHMEM_CREATED_MESSAGE_TYPE != aDescriptor.type()) {
+    NS_ERROR("expected 'shmem created' message");
+    return nullptr;
+  }
+  IPC::MessageReader reader(aDescriptor);
+  if (!ShmemCreated::ReadInfo(&reader, aId, aNBytes)) {
+    return nullptr;
+  }
+  RefPtr<SharedMemory> segment = NewSegment();
+  if (!segment) {
+    return nullptr;
+  }
+  if (!segment->ReadHandle(&reader)) {
+    NS_ERROR("trying to open invalid handle");
+    return nullptr;
+  }
+  reader.EndRead();
+  size_t size = SharedMemory::PageAlignedSize(*aNBytes + aExtraSize);
+  if (!segment->Map(size)) {
+    return nullptr;
+  }
+  // close the handle to the segment after it is mapped
+  segment->CloseHandle();
+  return segment.forget();
+}
+
+static void DestroySegment(SharedMemory* aSegment) {
+  // the SharedMemory dtor closes and unmaps the actual OS shmem segment
+  if (aSegment) {
+    aSegment->Release();
+  }
+}
+
+#if defined(DEBUG)
+
+static const char sMagic[] =
+    "This little piggy went to market.\n"
+    "This little piggy stayed at home.\n"
+    "This little piggy has roast beef,\n"
+    "This little piggy had none.\n"
+    "And this little piggy cried \"Wee! Wee! Wee!\" all the way home";
+
+struct Header {
+  // Don't use size_t or bool here because their size depends on the
+  // architecture.
+  uint32_t mSize;
+  uint32_t mUnsafe;
+  char mMagic[sizeof(sMagic)];
+};
+
+static void GetSections(Shmem::SharedMemory* aSegment, Header** aHeader,
+                        char** aFrontSentinel, char** aData,
+                        char** aBackSentinel) {
+  MOZ_ASSERT(aSegment && aFrontSentinel && aData && aBackSentinel,
+             "null param(s)");
+
+  *aFrontSentinel = reinterpret_cast<char*>(aSegment->memory());
+  MOZ_ASSERT(*aFrontSentinel, "null memory()");
+
+  *aHeader = reinterpret_cast<Header*>(*aFrontSentinel);
+
+  size_t pageSize = Shmem::SharedMemory::SystemPageSize();
+  *aData = *aFrontSentinel + pageSize;
+
+  *aBackSentinel = *aFrontSentinel + aSegment->Size() - pageSize;
+}
+
+static Header* GetHeader(Shmem::SharedMemory* aSegment) {
+  Header* header;
+  char* dontcare;
+  GetSections(aSegment, &header, &dontcare, &dontcare, &dontcare);
+  return header;
+}
+
+static void Protect(SharedMemory* aSegment) {
+  MOZ_ASSERT(aSegment, "null segment");
+  aSegment->Protect(reinterpret_cast<char*>(aSegment->memory()),
+                    aSegment->Size(), RightsNone);
+}
+
+static void Unprotect(SharedMemory* aSegment) {
+  MOZ_ASSERT(aSegment, "null segment");
+  aSegment->Protect(reinterpret_cast<char*>(aSegment->memory()),
+                    aSegment->Size(), RightsRead | RightsWrite);
+}
+
+//
+// In debug builds, we specially allocate shmem segments.  The layout
+// is as follows
+//
+//   Page 0: "front sentinel"
+//     size of mapping
+//     magic bytes
+//   Page 1 through n-1:
+//     user data
+//   Page n: "back sentinel"
+//     [nothing]
+//
+// The mapping can be in one of the following states, wrt to the
+// current process.
+//
+//   State "unmapped": all pages are mapped with no access rights.
+//
+//   State "mapping": all pages are mapped with read/write access.
+//
+//   State "mapped": the front and back sentinels are mapped with no
+//     access rights, and all the other pages are mapped with
+//     read/write access.
+//
+// When a SharedMemory segment is first allocated, it starts out in
+// the "mapping" state for the process that allocates the segment, and
+// in the "unmapped" state for the other process.  The allocating
+// process will then create a Shmem, which takes the segment into the
+// "mapped" state, where it can be accessed by clients.
+//
+// When a Shmem is sent to another process in an IPDL message, the
+// segment transitions into the "unmapped" state for the sending
+// process, and into the "mapping" state for the receiving process.
+// The receiving process will then create a Shmem from the underlying
+// segment, and take the segment into the "mapped" state.
+//
+// In the "mapping" state, we use the front sentinel to verify the
+// integrity of the shmem segment.  If valid, it has a size_t
+// containing the number of bytes the user allocated followed by the
+// magic bytes above.
+//
+// In the "mapped" state, the front and back sentinels have no access
+// rights.  They act as guards against buffer overflows and underflows
+// in client code; if clients touch a sentinel, they die with SIGSEGV.
+//
+// The "unmapped" state is used to enforce single-owner semantics of
+// the shmem segment.  If a process other than the current owner tries
+// to touch the segment, it dies with SIGSEGV.
+//
+
+Shmem::Shmem(SharedMemory* aSegment, id_t aId)
+    : mSegment(aSegment), mData(nullptr), mSize(0) {
+  MOZ_ASSERT(mSegment, "null segment");
+  MOZ_ASSERT(aId != 0, "invalid ID");
+
+  Unprotect(mSegment);
+
+  Header* header;
+  char* frontSentinel;
+  char* data;
+  char* backSentinel;
+  GetSections(aSegment, &header, &frontSentinel, &data, &backSentinel);
+
+  // do a quick validity check to avoid weird-looking crashes in libc
+  char check = *frontSentinel;
+  (void)check;
+
+  MOZ_ASSERT(!strncmp(header->mMagic, sMagic, sizeof(sMagic)),
+             "invalid segment");
+  mSize = static_cast<size_t>(header->mSize);
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  MOZ_ASSERT(mSegment->Size() - (2 * pageSize) >= mSize,
+             "illegal size in shared memory segment");
+
+  // transition into the "mapped" state by protecting the front and
+  // back sentinels (which guard against buffer under/overflows)
+  mSegment->Protect(frontSentinel, pageSize, RightsNone);
+  mSegment->Protect(backSentinel, pageSize, RightsNone);
+
+  // don't set these until we know they're valid
+  mData = data;
+  mId = aId;
+}
+
+void Shmem::AssertInvariants() const {
+  MOZ_ASSERT(mSegment, "null segment");
+  MOZ_ASSERT(mData, "null data pointer");
+  MOZ_ASSERT(mSize > 0, "invalid size");
+  // if the segment isn't owned by the current process, these will
+  // trigger SIGSEGV
+  char checkMappingFront = *reinterpret_cast<char*>(mData);
+  char checkMappingBack = *(reinterpret_cast<char*>(mData) + mSize - 1);
+
+  // avoid "unused" warnings for these variables:
+  Unused << checkMappingFront;
+  Unused << checkMappingBack;
+}
+
+void Shmem::RevokeRights() {
+  AssertInvariants();
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  Header* header = GetHeader(mSegment);
+
+  // Open this up for reading temporarily
+  mSegment->Protect(reinterpret_cast<char*>(header), pageSize, RightsRead);
+
+  if (!header->mUnsafe) {
+    Protect(mSegment);
+  } else {
+    mSegment->Protect(reinterpret_cast<char*>(header), pageSize, RightsNone);
+  }
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory> Shmem::Alloc(size_t aNBytes, bool aUnsafe,
+                                                   bool aProtect) {
+  NS_ASSERTION(aNBytes <= UINT32_MAX, "Will truncate shmem segment size!");
+  MOZ_ASSERT(!aProtect || !aUnsafe, "protect => !unsafe");
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  // |2*pageSize| is for the front and back sentinel
+  RefPtr<SharedMemory> segment = CreateSegment(aNBytes, 2 * pageSize);
+  if (!segment) {
+    return nullptr;
+  }
+
+  Header* header;
+  char* frontSentinel;
+  char* data;
+  char* backSentinel;
+  GetSections(segment, &header, &frontSentinel, &data, &backSentinel);
+
+  // initialize the segment with Shmem-internal information
+
+  // NB: this can't be a static assert because technically pageSize
+  // isn't known at compile time, event though in practice it's always
+  // going to be 4KiB
+  MOZ_ASSERT(sizeof(Header) <= pageSize, "Shmem::Header has gotten too big");
+  memcpy(header->mMagic, sMagic, sizeof(sMagic));
+  header->mSize = static_cast<uint32_t>(aNBytes);
+  header->mUnsafe = aUnsafe;
+
+  if (aProtect) Protect(segment);
+
+  return segment.forget();
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory> Shmem::OpenExisting(
+    const IPC::Message& aDescriptor, id_t* aId, bool aProtect) {
+  size_t size;
+  size_t pageSize = SharedMemory::SystemPageSize();
+  // |2*pageSize| is for the front and back sentinels
+  RefPtr<SharedMemory> segment =
+      ReadSegment(aDescriptor, aId, &size, 2 * pageSize);
+  if (!segment) {
+    return nullptr;
+  }
+
+  Header* header = GetHeader(segment);
+
+  if (size != header->mSize) {
+    // Deallocation should zero out the header, so check for that.
+    if (header->mSize || header->mUnsafe || header->mMagic[0] ||
+        memcmp(header->mMagic, &header->mMagic[1],
+               sizeof(header->mMagic) - 1)) {
+      NS_ERROR("Wrong size for this Shmem!");
+    } else {
+      NS_WARNING("Shmem was deallocated");
+    }
+    return nullptr;
+  }
+
+  // The caller of this function may not know whether the segment is
+  // unsafe or not
+  if (!header->mUnsafe && aProtect) Protect(segment);
+
+  return segment.forget();
+}
+
+// static
+void Shmem::Dealloc(SharedMemory* aSegment) {
+  if (!aSegment) return;
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  Header* header;
+  char* frontSentinel;
+  char* data;
+  char* backSentinel;
+  GetSections(aSegment, &header, &frontSentinel, &data, &backSentinel);
+
+  aSegment->Protect(frontSentinel, pageSize, RightsWrite | RightsRead);
+  memset(header->mMagic, 0, sizeof(sMagic));
+  header->mSize = 0;
+  header->mUnsafe = false;  // make it "safe" so as to catch errors
+
+  DestroySegment(aSegment);
+}
+
+#else  // !defined(DEBUG)
+
+Shmem::Shmem(SharedMemory* aSegment, id_t aId)
+    : mSegment(aSegment), mData(aSegment->memory()), mSize(0), mId(aId) {
+  mSize = static_cast<size_t>(*PtrToSize(mSegment));
+  MOZ_RELEASE_ASSERT(mSegment->Size() - sizeof(uint32_t) >= mSize,
+                     "illegal size in shared memory segment");
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory> Shmem::Alloc(size_t aNBytes,
+                                                   bool /*unused*/,
+                                                   bool /*unused*/) {
+  RefPtr<SharedMemory> segment = CreateSegment(aNBytes, sizeof(uint32_t));
+  if (!segment) {
+    return nullptr;
+  }
+
+  *PtrToSize(segment) = static_cast<uint32_t>(aNBytes);
+
+  return segment.forget();
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory> Shmem::OpenExisting(
+    const IPC::Message& aDescriptor, id_t* aId, bool /*unused*/) {
+  size_t size;
+  RefPtr<SharedMemory> segment =
+      ReadSegment(aDescriptor, aId, &size, sizeof(uint32_t));
+  if (!segment) {
+    return nullptr;
+  }
+
+  // this is the only validity check done in non-DEBUG builds
+  if (size != static_cast<size_t>(*PtrToSize(segment))) {
+    return nullptr;
+  }
+
+  return segment.forget();
+}
+
+// static
+void Shmem::Dealloc(SharedMemory* aSegment) { DestroySegment(aSegment); }
+
+#endif  // if defined(DEBUG)
+
+UniquePtr<IPC::Message> Shmem::MkCreatedMessage(int32_t routingId) {
+  AssertInvariants();
+
+  auto msg = MakeUnique<ShmemCreated>(routingId, mId, mSize);
+  IPC::MessageWriter writer(*msg);
+  if (!mSegment->WriteHandle(&writer)) {
+    return nullptr;
+  }
+  // close the handle to the segment after it is shared
+  mSegment->CloseHandle();
+  return msg;
+}
+
+UniquePtr<IPC::Message> Shmem::MkDestroyedMessage(int32_t routingId) {
+  AssertInvariants();
+  return MakeUnique<ShmemDestroyed>(routingId, mId);
+}
+
+void IPDLParamTraits<Shmem>::Write(IPC::MessageWriter* aWriter,
+                                   IProtocol* aActor, Shmem&& aParam) {
+  WriteIPDLParam(aWriter, aActor, aParam.mId);
+
+  aParam.RevokeRights();
+  aParam.forget();
+}
+
+bool IPDLParamTraits<Shmem>::Read(IPC::MessageReader* aReader,
+                                  IProtocol* aActor, paramType* aResult) {
+  paramType::id_t id;
+  if (!ReadIPDLParam(aReader, aActor, &id)) {
+    return false;
+  }
+
+  Shmem::SharedMemory* rawmem = aActor->LookupSharedMemory(id);
+  if (rawmem) {
+    *aResult = Shmem(rawmem, id);
+    return true;
+  }
+  *aResult = Shmem();
+  return true;
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/Shmem.h b/ipc/glue/Shmem.h
new file mode 100644
index 0000000000..3b726f66d9
--- /dev/null
+++ b/ipc/glue/Shmem.h
@@ -0,0 +1,205 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_Shmem_h
+#define mozilla_ipc_Shmem_h
+
+#include "mozilla/Attributes.h"
+
+#include "base/basictypes.h"
+#include "base/process.h"
+
+#include "nscore.h"
+#include "nsDebug.h"
+
+#include "mozilla/ipc/SharedMemory.h"
+#include "mozilla/Range.h"
+#include "mozilla/UniquePtr.h"
+
+/**
+ * |Shmem| is one agent in the IPDL shared memory scheme.  The way it
+    works is essentially
+ *
+ *  (1) C++ code calls, say, |parentActor->AllocShmem(size)|
+
+ *  (2) IPDL-generated code creates a |mozilla::ipc::SharedMemory|
+ *  wrapping the bare OS shmem primitives.  The code then adds the new
+ *  SharedMemory to the set of shmem segments being managed by IPDL.
+ *
+ *  (3) IPDL-generated code "shares" the new SharedMemory to the child
+ *  process, and then sends a special asynchronous IPC message to the
+ *  child notifying it of the creation of the segment.  (What this
+ *  means is OS specific.)
+ *
+ *  (4a) The child receives the special IPC message, and using the
+ *  |SharedMemory{Basic}::Handle| it was passed, creates a
+ *  |mozilla::ipc::SharedMemory| in the child
+ *  process.
+ *
+ *  (4b) After sending the "shmem-created" IPC message, IPDL-generated
+ *  code in the parent returns a |mozilla::ipc::Shmem| back to the C++
+ *  caller of |parentActor->AllocShmem()|.  The |Shmem| is a "weak
+ *  reference" to the underlying |SharedMemory|, which is managed by
+ *  IPDL-generated code.  C++ consumers of |Shmem| can't get at the
+ *  underlying |SharedMemory|.
+ *
+ * If parent code wants to give access rights to the Shmem to the
+ * child, it does so by sending its |Shmem| to the child, in an IPDL
+ * message.  The parent's |Shmem| then "dies", i.e. becomes
+ * inaccessible.  This process could be compared to passing a
+ * "shmem-access baton" between parent and child.
+ */
+
+namespace mozilla {
+namespace layers {
+class ShadowLayerForwarder;
+}  // namespace layers
+
+namespace ipc {
+
+class IProtocol;
+class IToplevelProtocol;
+
+template <typename P>
+struct IPDLParamTraits;
+
+class Shmem final {
+  friend struct IPDLParamTraits<mozilla::ipc::Shmem>;
+  friend class mozilla::ipc::IProtocol;
+  friend class mozilla::ipc::IToplevelProtocol;
+#ifdef DEBUG
+  // For ShadowLayerForwarder::CheckSurfaceDescriptor
+  friend class mozilla::layers::ShadowLayerForwarder;
+#endif
+
+ public:
+  typedef int32_t id_t;
+  // Low-level wrapper around platform shmem primitives.
+  typedef mozilla::ipc::SharedMemory SharedMemory;
+
+  Shmem() : mSegment(nullptr), mData(nullptr), mSize(0), mId(0) {}
+
+  Shmem(const Shmem& aOther) = default;
+
+  ~Shmem() {
+    // Shmem only holds a "weak ref" to the actual segment, which is
+    // owned by IPDL. So there's nothing interesting to be done here
+    forget();
+  }
+
+  Shmem& operator=(const Shmem& aRhs) = default;
+
+  bool operator==(const Shmem& aRhs) const { return mSegment == aRhs.mSegment; }
+
+  // Returns whether this Shmem is writable by you, and thus whether you can
+  // transfer writability to another actor.
+  bool IsWritable() const { return mSegment != nullptr; }
+
+  // Returns whether this Shmem is readable by you, and thus whether you can
+  // transfer readability to another actor.
+  bool IsReadable() const { return mSegment != nullptr; }
+
+  // Return a pointer to the user-visible data segment.
+  template <typename T>
+  T* get() const {
+    AssertInvariants();
+    AssertAligned<T>();
+
+    return reinterpret_cast<T*>(mData);
+  }
+
+  // Return the size of the segment as requested when this shmem
+  // segment was allocated, in units of T.  The underlying mapping may
+  // actually be larger because of page alignment and private data,
+  // but this isn't exposed to clients.
+  template <typename T>
+  size_t Size() const {
+    AssertInvariants();
+    AssertAligned<T>();
+
+    return mSize / sizeof(T);
+  }
+
+  template <typename T>
+  Range<T> Range() const {
+    return {get<T>(), Size<T>()};
+  }
+
+ private:
+  // These shouldn't be used directly, use the IPDL interface instead.
+
+  Shmem(SharedMemory* aSegment, id_t aId);
+
+  id_t Id() const { return mId; }
+
+  SharedMemory* Segment() const { return mSegment; }
+
+#ifndef DEBUG
+  void RevokeRights() {}
+#else
+  void RevokeRights();
+#endif
+
+  void forget() {
+    mSegment = nullptr;
+    mData = nullptr;
+    mSize = 0;
+    mId = 0;
+  }
+
+  static already_AddRefed<Shmem::SharedMemory> Alloc(size_t aNBytes,
+                                                     bool aUnsafe,
+                                                     bool aProtect = false);
+
+  // Prepare this to be shared with another process. Return an IPC message that
+  // contains enough information for the other process to map this segment in
+  // OpenExisting() below.  Return a new message if successful (owned by the
+  // caller), nullptr if not.
+  UniquePtr<IPC::Message> MkCreatedMessage(int32_t routingId);
+
+  // Stop sharing this with another process. Return an IPC message that
+  // contains enough information for the other process to unmap this
+  // segment.  Return a new message if successful (owned by the
+  // caller), nullptr if not.
+  UniquePtr<IPC::Message> MkDestroyedMessage(int32_t routingId);
+
+  // Return a SharedMemory instance in this process using the descriptor shared
+  // to us by the process that created the underlying OS shmem resource.  The
+  // contents of the descriptor depend on the type of SharedMemory that was
+  // passed to us.
+  static already_AddRefed<SharedMemory> OpenExisting(
+      const IPC::Message& aDescriptor, id_t* aId, bool aProtect = false);
+
+  static void Dealloc(SharedMemory* aSegment);
+
+  template <typename T>
+  void AssertAligned() const {
+    if (0 != (mSize % sizeof(T))) MOZ_CRASH("shmem is not T-aligned");
+  }
+
+#if !defined(DEBUG)
+  void AssertInvariants() const {}
+
+  static uint32_t* PtrToSize(SharedMemory* aSegment) {
+    char* endOfSegment =
+        reinterpret_cast<char*>(aSegment->memory()) + aSegment->Size();
+    return reinterpret_cast<uint32_t*>(endOfSegment - sizeof(uint32_t));
+  }
+
+#else
+  void AssertInvariants() const;
+#endif
+
+  RefPtr<SharedMemory> mSegment;
+  void* mData;
+  size_t mSize;
+  id_t mId;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_Shmem_h
diff --git a/ipc/glue/ShmemMessageUtils.h b/ipc/glue/ShmemMessageUtils.h
new file mode 100644
index 0000000000..c0f8c40215
--- /dev/null
+++ b/ipc/glue/ShmemMessageUtils.h
@@ -0,0 +1,30 @@
+/* -*- 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_ipc_ShmemMessageUtils_h
+#define mozilla_ipc_ShmemMessageUtils_h
+
+#include "ipc/IPCMessageUtils.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "mozilla/ipc/Shmem.h"
+
+namespace mozilla {
+namespace ipc {
+
+template <>
+struct IPDLParamTraits<Shmem> {
+  typedef Shmem paramType;
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    paramType&& aParam);
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   paramType* aResult);
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_ShmemMessageUtils_h
diff --git a/ipc/glue/SideVariant.h b/ipc/glue/SideVariant.h
new file mode 100644
index 0000000000..3082feebde
--- /dev/null
+++ b/ipc/glue/SideVariant.h
@@ -0,0 +1,187 @@
+/* -*- 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_ipc_SidedVariant_h
+#define mozilla_ipc_SidedVariant_h
+
+#include <variant>
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "ipc/IPCMessageUtils.h"
+
+namespace mozilla {
+namespace ipc {
+
+/**
+ * Helper type used by IPDL structs and unions to hold actor pointers with a
+ * dynamic side.
+ *
+ * When sent over IPC, ParentSide will be used for send/recv on parent actors,
+ * and ChildSide will be used for send/recv on child actors.
+ */
+template <typename ParentSide, typename ChildSide>
+struct SideVariant {
+ public:
+  SideVariant() = default;
+  template <typename U,
+            std::enable_if_t<std::is_convertible_v<U&&, ParentSide>, int> = 0>
+  MOZ_IMPLICIT SideVariant(U&& aParent) : mParent(std::forward<U>(aParent)) {}
+  template <typename U,
+            std::enable_if_t<std::is_convertible_v<U&&, ChildSide>, int> = 0>
+  MOZ_IMPLICIT SideVariant(U&& aChild) : mChild(std::forward<U>(aChild)) {}
+  MOZ_IMPLICIT SideVariant(std::nullptr_t) {}
+
+  MOZ_IMPLICIT SideVariant& operator=(ParentSide aParent) {
+    mParent = aParent;
+    mChild = nullptr;
+    return *this;
+  }
+  MOZ_IMPLICIT SideVariant& operator=(ChildSide aChild) {
+    mChild = aChild;
+    mParent = nullptr;
+    return *this;
+  }
+  MOZ_IMPLICIT SideVariant& operator=(std::nullptr_t) {
+    mChild = nullptr;
+    mParent = nullptr;
+    return *this;
+  }
+
+  MOZ_IMPLICIT operator bool() const { return mParent || mChild; }
+
+  bool IsNull() const { return !operator bool(); }
+  bool IsParent() const { return mParent; }
+  bool IsChild() const { return mChild; }
+
+  ParentSide AsParent() const {
+    MOZ_ASSERT(IsNull() || IsParent());
+    return mParent;
+  }
+  ChildSide AsChild() const {
+    MOZ_ASSERT(IsNull() || IsChild());
+    return mChild;
+  }
+
+ private:
+  // As the values are both pointers, this is the same size as a variant would
+  // be, but has less risk of type confusion, and supports an overall `nullptr`
+  // value which is neither parent nor child.
+  ParentSide mParent = nullptr;
+  ChildSide mChild = nullptr;
+};
+
+}  // namespace ipc
+
+// NotNull specialization to expose AsChild and AsParent on the NotNull itself
+// avoiding unnecessary unwrapping.
+template <typename ParentSide, typename ChildSide>
+class NotNull<mozilla::ipc::SideVariant<ParentSide, ChildSide>> {
+  template <typename U>
+  friend constexpr NotNull<U> WrapNotNull(U aBasePtr);
+  template <typename U>
+  friend constexpr NotNull<U> WrapNotNullUnchecked(U aBasePtr);
+  template <typename U>
+  friend class NotNull;
+
+  using BasePtr = mozilla::ipc::SideVariant<ParentSide, ChildSide>;
+
+  BasePtr mBasePtr;
+
+  // This constructor is only used by WrapNotNull() and MakeNotNull<U>().
+  template <typename U>
+  constexpr explicit NotNull(U aBasePtr) : mBasePtr(aBasePtr) {}
+
+ public:
+  // Disallow default construction.
+  NotNull() = delete;
+
+  // Construct/assign from another NotNull with a compatible base pointer type.
+  template <typename U, typename = std::enable_if_t<
+                            std::is_convertible_v<const U&, BasePtr>>>
+  constexpr MOZ_IMPLICIT NotNull(const NotNull<U>& aOther)
+      : mBasePtr(aOther.get()) {
+    static_assert(sizeof(BasePtr) == sizeof(NotNull<BasePtr>),
+                  "NotNull must have zero space overhead.");
+    static_assert(offsetof(NotNull<BasePtr>, mBasePtr) == 0,
+                  "mBasePtr must have zero offset.");
+  }
+
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible_v<U&&, BasePtr>>>
+  constexpr MOZ_IMPLICIT NotNull(MovingNotNull<U>&& aOther)
+      : mBasePtr(NotNull{std::move(aOther)}) {}
+
+  // Disallow null checks, which are unnecessary for this type.
+  explicit operator bool() const = delete;
+
+  // Explicit conversion to a base pointer. Use only to resolve ambiguity or to
+  // get a castable pointer.
+  constexpr const BasePtr& get() const { return mBasePtr; }
+
+  // Implicit conversion to a base pointer. Preferable to get().
+  constexpr operator const BasePtr&() const { return get(); }
+
+  bool IsParent() const { return get().IsParent(); }
+  bool IsChild() const { return get().IsChild(); }
+
+  NotNull<ParentSide> AsParent() const { return WrapNotNull(get().AsParent()); }
+  NotNull<ChildSide> AsChild() const { return WrapNotNull(get().AsChild()); }
+};
+
+}  // namespace mozilla
+
+namespace IPC {
+
+template <typename ParentSide, typename ChildSide>
+struct ParamTraits<mozilla::ipc::SideVariant<ParentSide, ChildSide>> {
+  typedef mozilla::ipc::SideVariant<ParentSide, ChildSide> paramType;
+
+  static void Write(IPC::MessageWriter* aWriter, const paramType& aParam) {
+    if (!aWriter->GetActor()) {
+      aWriter->FatalError("actor required to serialize this type");
+      return;
+    }
+
+    if (aWriter->GetActor()->GetSide() == mozilla::ipc::ParentSide) {
+      if (aParam && !aParam.IsParent()) {
+        aWriter->FatalError("invalid side");
+        return;
+      }
+      WriteParam(aWriter, aParam.AsParent());
+    } else {
+      if (aParam && !aParam.IsChild()) {
+        aWriter->FatalError("invalid side");
+        return;
+      }
+      WriteParam(aWriter, aParam.AsChild());
+    }
+  }
+
+  static ReadResult<paramType> Read(IPC::MessageReader* aReader) {
+    if (!aReader->GetActor()) {
+      aReader->FatalError("actor required to deserialize this type");
+      return {};
+    }
+
+    if (aReader->GetActor()->GetSide() == mozilla::ipc::ParentSide) {
+      auto parentSide = ReadParam<ParentSide>(aReader);
+      if (!parentSide) {
+        return {};
+      }
+      return std::move(*parentSide);
+    }
+    auto childSide = ReadParam<ChildSide>(aReader);
+    if (!childSide) {
+      return {};
+    }
+    return std::move(*childSide);
+  }
+};
+
+}  // namespace IPC
+
+#endif  // mozilla_ipc_SidedVariant_h
diff --git a/ipc/glue/StringUtil.cpp b/ipc/glue/StringUtil.cpp
new file mode 100644
index 0000000000..2eae9a1282
--- /dev/null
+++ b/ipc/glue/StringUtil.cpp
@@ -0,0 +1,88 @@
+/* -*- 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 "base/string_util.h"
+
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/sys_string_conversions.h"
+
+#include "base/string_piece.h"
+#include "base/string_util.h"
+
+#include "build/build_config.h"
+
+// FIXME/cjones: these really only pertain to the linux sys string
+// converters.
+#ifdef WCHAR_T_IS_UTF16
+#  define ICONV_WCHAR_T_ENCODING "UTF-16"
+#else
+#  define ICONV_WCHAR_T_ENCODING "WCHAR_T"
+#endif
+
+// FIXME/cjones: BIG assumption here that std::string is a good
+// container of UTF8-encoded strings.  this is probably wrong, as its
+// API doesn't really make sense for UTF8.
+
+namespace base {
+
+// FIXME/cjones: as its name implies, this function is a hack.
+template <typename FromType, typename ToType>
+ToType GhettoStringConvert(const FromType& in) {
+  // FIXME/cjones: assumes no non-ASCII characters in |in|
+  ToType out;
+  out.resize(in.length());
+  for (int i = 0; i < static_cast<int>(in.length()); ++i)
+    out[i] = static_cast<typename ToType::value_type>(in[i]);
+  return out;
+}
+
+}  // namespace base
+
+// Implement functions that were in the chromium ICU library, which
+// we're not taking.
+
+std::string WideToUTF8(const std::wstring& wide) {
+  return base::SysWideToUTF8(wide);
+}
+
+std::wstring UTF8ToWide(const StringPiece& utf8) {
+  return base::SysUTF8ToWide(utf8);
+}
+
+namespace base {
+
+// FIXME/cjones: here we're entirely replacing the linux string
+// converters, and implementing the one that doesn't exist for OS X
+// and Windows.
+
+#if !defined(OS_MACOSX) && !defined(OS_WIN)
+std::string SysWideToUTF8(const std::wstring& wide) {
+  // FIXME/cjones: do this with iconv
+  return GhettoStringConvert<std::wstring, std::string>(wide);
+}
+#endif
+
+#if !defined(OS_MACOSX) && !defined(OS_WIN)
+std::wstring SysUTF8ToWide(const StringPiece& utf8) {
+  // FIXME/cjones: do this with iconv
+  return GhettoStringConvert<StringPiece, std::wstring>(utf8);
+}
+
+std::string SysWideToNativeMB(const std::wstring& wide) {
+  // TODO(evanm): we can't assume Linux is UTF-8.
+  return SysWideToUTF8(wide);
+}
+
+std::wstring SysNativeMBToWide(const StringPiece& native_mb) {
+  // TODO(evanm): we can't assume Linux is UTF-8.
+  return SysUTF8ToWide(native_mb);
+}
+#endif
+
+}  // namespace base
diff --git a/ipc/glue/TaintingIPCUtils.h b/ipc/glue/TaintingIPCUtils.h
new file mode 100644
index 0000000000..d4f61d95b5
--- /dev/null
+++ b/ipc/glue/TaintingIPCUtils.h
@@ -0,0 +1,41 @@
+/* -*- 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_ipc_Tainting_h
+#define mozilla_ipc_Tainting_h
+
+#include "mozilla/Tainting.h"
+
+#include "base/basictypes.h"
+#include "base/process.h"
+
+#include "mozilla/ipc/IPDLParamTraits.h"
+
+namespace mozilla {
+namespace ipc {
+
+template <typename T>
+struct IPDLParamTraits<mozilla::Tainted<T>> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    const mozilla::Tainted<T>& aParam) {
+    WriteIPDLParam(aWriter, aActor, aParam.mValue);
+  }
+
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    mozilla::Tainted<T>&& aParam) {
+    WriteIPDLParam(aWriter, aActor, std::move(aParam.mValue));
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   mozilla::Tainted<T>* aResult) {
+    return ReadIPDLParam(aReader, aActor, &(aResult->mValue));
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_Tainting_h
diff --git a/ipc/glue/TaskFactory.h b/ipc/glue/TaskFactory.h
new file mode 100644
index 0000000000..af63244cf0
--- /dev/null
+++ b/ipc/glue/TaskFactory.h
@@ -0,0 +1,97 @@
+/* -*- 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_plugins_TaskFactory_h
+#define mozilla_plugins_TaskFactory_h
+
+#include <base/task.h>
+
+#include <utility>
+
+/*
+ * This is based on the ScopedRunnableMethodFactory from
+ * ipc/chromium/src/base/task.h Chromium's factories assert if tasks are created
+ * and run on different threads, which is something we need to do in
+ * PluginModuleParent (hang UI vs. main thread). TaskFactory just provides
+ * cancellable tasks that don't assert this. This version also allows both
+ * ScopedMethod and regular Tasks to be generated by the same Factory object.
+ */
+
+namespace mozilla {
+namespace ipc {
+
+template <class T>
+class TaskFactory : public RevocableStore {
+ private:
+  template <class TaskType>
+  class TaskWrapper : public TaskType {
+   public:
+    template <typename... Args>
+    explicit TaskWrapper(RevocableStore* store, Args&&... args)
+        : TaskType(std::forward<Args>(args)...), revocable_(store) {}
+
+    NS_IMETHOD Run() override {
+      if (!revocable_.revoked()) TaskType::Run();
+      return NS_OK;
+    }
+
+   private:
+    Revocable revocable_;
+  };
+
+ public:
+  explicit TaskFactory(T* object) : object_(object) {}
+
+  template <typename TaskParamType, typename... Args>
+  inline already_AddRefed<TaskParamType> NewTask(Args&&... args) {
+    typedef TaskWrapper<TaskParamType> TaskWrapper;
+    RefPtr<TaskWrapper> task =
+        new TaskWrapper(this, std::forward<Args>(args)...);
+    return task.forget();
+  }
+
+  template <class Method, typename... Args>
+  inline already_AddRefed<Runnable> NewRunnableMethod(Method method,
+                                                      Args&&... args) {
+    typedef decltype(base::MakeTuple(std::forward<Args>(args)...)) ArgTuple;
+    typedef RunnableMethod<Method, ArgTuple> RunnableMethod;
+    typedef TaskWrapper<RunnableMethod> TaskWrapper;
+
+    RefPtr<TaskWrapper> task = new TaskWrapper(
+        this, object_, method, base::MakeTuple(std::forward<Args>(args)...));
+
+    return task.forget();
+  }
+
+ protected:
+  template <class Method, class Params>
+  class RunnableMethod : public Runnable {
+   public:
+    RunnableMethod(T* obj, Method meth, const Params& params)
+        : Runnable("ipc::TaskFactory::RunnableMethod"),
+          obj_(obj),
+          meth_(meth),
+          params_(params) {}
+
+    NS_IMETHOD Run() override {
+      DispatchToMethod(obj_, meth_, params_);
+      return NS_OK;
+    }
+
+   private:
+    T* obj_;
+    Method meth_;
+    Params params_;
+  };
+
+ private:
+  T* object_;
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_plugins_TaskFactory_h
diff --git a/ipc/glue/ToplevelActorHolder.h b/ipc/glue/ToplevelActorHolder.h
new file mode 100644
index 0000000000..6e95ef8565
--- /dev/null
+++ b/ipc/glue/ToplevelActorHolder.h
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_IPC_TOPLEVELACTORHOLDER_H
+#define MOZILLA_IPC_TOPLEVELACTORHOLDER_H
+
+#include "nsISupports.h"
+
+namespace mozilla::ipc {
+
+// Class to let us close the actor when we're not using it anymore.  You
+// should create a single instance of this, and when you have no more
+// references it will be destroyed and will Close() the underlying
+// top-level channel.
+// When you want to send something, you use something like
+// aActor->Actor()->SendFoo()
+
+// You can avoid calling Close() on an un-connected Actor (for example if
+// Bind() fails) by calling RemoveActor();
+template <typename T>
+class ToplevelActorHolder final {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_ONEVENTTARGET(ToplevelActorHolder)
+
+  explicit ToplevelActorHolder(T* aActor) : mActor(aActor) {}
+
+  constexpr T* Actor() const { return mActor; }
+  inline void RemoveActor() { mActor = nullptr; }
+
+ private:
+  inline ~ToplevelActorHolder() {
+    if (mActor) {
+      mActor->Close();
+    }
+  }
+
+  RefPtr<T> mActor;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // MOZILLA_IPC_TOPLEVELACTORHOLDER_H
diff --git a/ipc/glue/TransportSecurityInfoUtils.cpp b/ipc/glue/TransportSecurityInfoUtils.cpp
new file mode 100644
index 0000000000..9898e2b579
--- /dev/null
+++ b/ipc/glue/TransportSecurityInfoUtils.cpp
@@ -0,0 +1,78 @@
+/* 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 "TransportSecurityInfoUtils.h"
+
+#include "ipc/IPCMessageUtils.h"
+#include "mozilla/psm/TransportSecurityInfo.h"
+#include "nsNSSCertificate.h"
+
+namespace IPC {
+
+void ParamTraits<nsITransportSecurityInfo*>::Write(
+    MessageWriter* aWriter, nsITransportSecurityInfo* aParam) {
+  bool nonNull = !!aParam;
+  WriteParam(aWriter, nonNull);
+  if (!nonNull) {
+    return;
+  }
+
+  aParam->SerializeToIPC(aWriter);
+}
+
+bool ParamTraits<nsITransportSecurityInfo*>::Read(
+    MessageReader* aReader, RefPtr<nsITransportSecurityInfo>* aResult) {
+  *aResult = nullptr;
+
+  bool nonNull = false;
+  if (!ReadParam(aReader, &nonNull)) {
+    return false;
+  }
+
+  if (!nonNull) {
+    return true;
+  }
+
+  if (!mozilla::psm::TransportSecurityInfo::DeserializeFromIPC(aReader,
+                                                               aResult)) {
+    return false;
+  }
+
+  return true;
+}
+
+void ParamTraits<nsIX509Cert*>::Write(MessageWriter* aWriter,
+                                      nsIX509Cert* aParam) {
+  bool nonNull = !!aParam;
+  WriteParam(aWriter, nonNull);
+  if (!nonNull) {
+    return;
+  }
+
+  aParam->SerializeToIPC(aWriter);
+}
+
+bool ParamTraits<nsIX509Cert*>::Read(MessageReader* aReader,
+                                     RefPtr<nsIX509Cert>* aResult) {
+  *aResult = nullptr;
+
+  bool nonNull = false;
+  if (!ReadParam(aReader, &nonNull)) {
+    return false;
+  }
+
+  if (!nonNull) {
+    return true;
+  }
+
+  RefPtr<nsIX509Cert> cert = new nsNSSCertificate();
+  if (!cert->DeserializeFromIPC(aReader)) {
+    return false;
+  }
+
+  *aResult = std::move(cert);
+  return true;
+}
+
+}  // namespace IPC
diff --git a/ipc/glue/TransportSecurityInfoUtils.h b/ipc/glue/TransportSecurityInfoUtils.h
new file mode 100644
index 0000000000..009db8e162
--- /dev/null
+++ b/ipc/glue/TransportSecurityInfoUtils.h
@@ -0,0 +1,43 @@
+/* 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_ipc_TransportSecurityInfoUtils_h
+#define mozilla_ipc_TransportSecurityInfoUtils_h
+
+#include "ipc/EnumSerializer.h"
+#include "mozilla/RefPtr.h"
+#include "nsITransportSecurityInfo.h"
+#include "nsIX509Cert.h"
+
+class MessageReader;
+class MessageWriter;
+
+namespace IPC {
+
+template <typename>
+struct ParamTraits;
+
+template <>
+struct ParamTraits<nsITransportSecurityInfo*> {
+  static void Write(MessageWriter* aWriter, nsITransportSecurityInfo* aParam);
+  static bool Read(MessageReader* aReader,
+                   RefPtr<nsITransportSecurityInfo>* aResult);
+};
+
+template <>
+struct ParamTraits<nsIX509Cert*> {
+  static void Write(MessageWriter* aWriter, nsIX509Cert* aCert);
+  static bool Read(MessageReader* aReader, RefPtr<nsIX509Cert>* aResult);
+};
+
+template <>
+struct ParamTraits<nsITransportSecurityInfo::OverridableErrorCategory>
+    : public ContiguousEnumSerializerInclusive<
+          nsITransportSecurityInfo::OverridableErrorCategory,
+          nsITransportSecurityInfo::OverridableErrorCategory::ERROR_UNSET,
+          nsITransportSecurityInfo::OverridableErrorCategory::ERROR_TIME> {};
+
+}  // namespace IPC
+
+#endif  // mozilla_ipc_TransportSecurityInfoUtils_h
diff --git a/ipc/glue/URIParams.ipdlh b/ipc/glue/URIParams.ipdlh
new file mode 100644
index 0000000000..99b18afd0f
--- /dev/null
+++ b/ipc/glue/URIParams.ipdlh
@@ -0,0 +1,117 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+
+include PBackgroundSharedTypes;
+
+namespace mozilla {
+namespace ipc {
+
+struct SimpleURIParams
+{
+  nsCString scheme;
+  nsCString path;
+  nsCString ref;
+  nsCString query;
+};
+
+struct DefaultURIParams
+{
+  nsCString spec;
+};
+
+struct StandardURLSegment
+{
+  uint32_t position;
+  int32_t length;
+};
+
+struct StandardURLParams
+{
+  uint32_t urlType;
+  int32_t port;
+  int32_t defaultPort;
+  nsCString spec;
+  StandardURLSegment scheme;
+  StandardURLSegment authority;
+  StandardURLSegment username;
+  StandardURLSegment password;
+  StandardURLSegment host;
+  StandardURLSegment path;
+  StandardURLSegment filePath;
+  StandardURLSegment directory;
+  StandardURLSegment baseName;
+  StandardURLSegment extension;
+  StandardURLSegment query;
+  StandardURLSegment ref;
+  bool supportsFileURL;
+  bool isSubstituting;
+};
+
+struct JARURIParams
+{
+  URIParams jarFile;
+  URIParams jarEntry;
+  nsCString charset;
+};
+
+struct IconURIParams
+{
+  URIParams? uri;
+  uint32_t size;
+  nsCString contentType;
+  nsCString fileName;
+  nsCString stockIcon;
+  int32_t iconSize;
+  int32_t iconState;
+};
+
+struct HostObjectURIParams
+{
+  SimpleURIParams simpleParams;
+  bool revoked;
+};
+
+union URIParams
+{
+  SimpleURIParams;
+  StandardURLParams;
+  JARURIParams;
+  IconURIParams;
+  JSURIParams;
+  SimpleNestedURIParams;
+  HostObjectURIParams;
+  DefaultURIParams;
+  NestedAboutURIParams;
+  SubstitutingJARURIParams;
+};
+
+struct JSURIParams
+{
+  SimpleURIParams simpleParams;
+  URIParams? baseURI;
+};
+
+struct SimpleNestedURIParams
+{
+  SimpleURIParams simpleParams;
+  URIParams innerURI;
+};
+
+struct NestedAboutURIParams
+{
+  SimpleNestedURIParams nestedParams;
+  URIParams? baseURI;
+};
+
+struct SubstitutingJARURIParams
+{
+  URIParams source;
+  JARURIParams resolved;
+};
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/URIUtils.cpp b/ipc/glue/URIUtils.cpp
new file mode 100644
index 0000000000..690509cecc
--- /dev/null
+++ b/ipc/glue/URIUtils.cpp
@@ -0,0 +1,140 @@
+/* -*- 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 "URIUtils.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/dom/BlobURL.h"
+#include "mozilla/net/DefaultURI.h"
+#include "mozilla/net/SubstitutingJARURI.h"
+#include "mozilla/net/SubstitutingURL.h"
+#include "nsAboutProtocolHandler.h"
+#include "nsComponentManagerUtils.h"
+#include "nsDebug.h"
+#include "nsID.h"
+#include "nsJARURI.h"
+#include "nsIIconURI.h"
+#include "nsJSProtocolHandler.h"
+#include "nsNetCID.h"
+#include "nsSimpleNestedURI.h"
+#include "nsThreadUtils.h"
+#include "nsIURIMutator.h"
+
+using namespace mozilla::ipc;
+using mozilla::ArrayLength;
+
+namespace {
+
+NS_DEFINE_CID(kSimpleURIMutatorCID, NS_SIMPLEURIMUTATOR_CID);
+NS_DEFINE_CID(kStandardURLMutatorCID, NS_STANDARDURLMUTATOR_CID);
+NS_DEFINE_CID(kJARURIMutatorCID, NS_JARURIMUTATOR_CID);
+NS_DEFINE_CID(kIconURIMutatorCID, NS_MOZICONURIMUTATOR_CID);
+
+}  // namespace
+
+namespace mozilla {
+namespace ipc {
+
+void SerializeURI(nsIURI* aURI, URIParams& aParams) {
+  MOZ_ASSERT(aURI);
+
+  aURI->Serialize(aParams);
+  if (aParams.type() == URIParams::T__None) {
+    MOZ_CRASH("Serialize failed!");
+  }
+}
+
+void SerializeURI(nsIURI* aURI, Maybe<URIParams>& aParams) {
+  if (aURI) {
+    URIParams params;
+    SerializeURI(aURI, params);
+    aParams = Some(std::move(params));
+  } else {
+    aParams = Nothing();
+  }
+}
+
+already_AddRefed<nsIURI> DeserializeURI(const URIParams& aParams) {
+  nsCOMPtr<nsIURIMutator> mutator;
+
+  switch (aParams.type()) {
+    case URIParams::TSimpleURIParams:
+      mutator = do_CreateInstance(kSimpleURIMutatorCID);
+      break;
+
+    case URIParams::TStandardURLParams:
+      if (aParams.get_StandardURLParams().isSubstituting()) {
+        mutator = new net::SubstitutingURL::Mutator();
+      } else {
+        mutator = do_CreateInstance(kStandardURLMutatorCID);
+      }
+      break;
+
+    case URIParams::TJARURIParams:
+      mutator = do_CreateInstance(kJARURIMutatorCID);
+      break;
+
+    case URIParams::TJSURIParams:
+      mutator = new nsJSURI::Mutator();
+      break;
+
+    case URIParams::TIconURIParams:
+      mutator = do_CreateInstance(kIconURIMutatorCID);
+      break;
+
+    case URIParams::TSimpleNestedURIParams:
+      mutator = new net::nsSimpleNestedURI::Mutator();
+      break;
+
+    case URIParams::THostObjectURIParams:
+      mutator = new mozilla::dom::BlobURL::Mutator();
+      break;
+
+    case URIParams::TDefaultURIParams:
+      mutator = new mozilla::net::DefaultURI::Mutator();
+      break;
+
+    case URIParams::TNestedAboutURIParams:
+      mutator = new net::nsNestedAboutURI::Mutator();
+      break;
+
+    case URIParams::TSubstitutingJARURIParams:
+      mutator = new net::SubstitutingJARURI::Mutator();
+      break;
+
+    default:
+      MOZ_CRASH("Unknown params!");
+  }
+
+  MOZ_ASSERT(mutator);
+
+  nsresult rv = mutator->Deserialize(aParams);
+  if (NS_FAILED(rv)) {
+    MOZ_ASSERT(false, "Deserialize failed!");
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  DebugOnly<nsresult> rv2 = mutator->Finalize(getter_AddRefs(uri));
+  MOZ_ASSERT(uri);
+  MOZ_ASSERT(NS_SUCCEEDED(rv2));
+
+  return uri.forget();
+}
+
+already_AddRefed<nsIURI> DeserializeURI(const Maybe<URIParams>& aParams) {
+  nsCOMPtr<nsIURI> uri;
+
+  if (aParams.isSome()) {
+    uri = DeserializeURI(aParams.ref());
+  }
+
+  return uri.forget();
+}
+
+}  // namespace ipc
+}  // namespace mozilla
diff --git a/ipc/glue/URIUtils.h b/ipc/glue/URIUtils.h
new file mode 100644
index 0000000000..7cb8687bbe
--- /dev/null
+++ b/ipc/glue/URIUtils.h
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_URIUtils_h
+#define mozilla_ipc_URIUtils_h
+
+#include "mozilla/ipc/URIParams.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+#include "nsCOMPtr.h"
+#include "nsIURI.h"
+
+namespace mozilla {
+namespace ipc {
+
+void SerializeURI(nsIURI* aURI, URIParams& aParams);
+
+void SerializeURI(nsIURI* aURI, Maybe<URIParams>& aParams);
+
+already_AddRefed<nsIURI> DeserializeURI(const URIParams& aParams);
+
+already_AddRefed<nsIURI> DeserializeURI(const Maybe<URIParams>& aParams);
+
+template <>
+struct IPDLParamTraits<nsIURI*> {
+  static void Write(IPC::MessageWriter* aWriter, IProtocol* aActor,
+                    nsIURI* aParam) {
+    Maybe<URIParams> params;
+    SerializeURI(aParam, params);
+    WriteIPDLParam(aWriter, aActor, params);
+  }
+
+  static bool Read(IPC::MessageReader* aReader, IProtocol* aActor,
+                   RefPtr<nsIURI>* aResult) {
+    Maybe<URIParams> params;
+    if (!ReadIPDLParam(aReader, aActor, &params)) {
+      return false;
+    }
+    *aResult = DeserializeURI(params);
+    return true;
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // mozilla_ipc_URIUtils_h
diff --git a/ipc/glue/UtilityAudioDecoder.cpp b/ipc/glue/UtilityAudioDecoder.cpp
new file mode 100644
index 0000000000..0b28fd601e
--- /dev/null
+++ b/ipc/glue/UtilityAudioDecoder.cpp
@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 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/ProcInfo.h"
+#include "mozilla/ipc/UtilityAudioDecoder.h"
+#include "mozilla/ipc/UtilityProcessChild.h"
+
+namespace mozilla::ipc {
+
+UtilityActorName GetAudioActorName(const SandboxingKind aSandbox) {
+  switch (aSandbox) {
+    case GENERIC_UTILITY:
+      return UtilityActorName::AudioDecoder_Generic;
+#ifdef MOZ_APPLEMEDIA
+    case UTILITY_AUDIO_DECODING_APPLE_MEDIA:
+      return UtilityActorName::AudioDecoder_AppleMedia;
+#endif
+#ifdef XP_WIN
+    case UTILITY_AUDIO_DECODING_WMF:
+      return UtilityActorName::AudioDecoder_WMF;
+#endif
+#ifdef MOZ_WMF_MEDIA_ENGINE
+    case MF_MEDIA_ENGINE_CDM:
+      return UtilityActorName::MfMediaEngineCDM;
+#endif
+    default:
+      MOZ_CRASH("Unexpected mSandbox for GetActorName()");
+  }
+}
+
+nsCString GetChildAudioActorName() {
+  RefPtr<ipc::UtilityProcessChild> s = ipc::UtilityProcessChild::Get();
+  MOZ_ASSERT(s, "Has UtilityProcessChild");
+  return nsCString(dom::WebIDLUtilityActorNameValues::GetString(
+      GetAudioActorName(s->mSandbox)));
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityAudioDecoder.h b/ipc/glue/UtilityAudioDecoder.h
new file mode 100644
index 0000000000..4fed9aab64
--- /dev/null
+++ b/ipc/glue/UtilityAudioDecoder.h
@@ -0,0 +1,21 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 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 _include_ipc_glue_UtilityAudioDecoder_h__
+#define _include_ipc_glue_UtilityAudioDecoder_h__
+
+#include "mozilla/dom/ChromeUtilsBinding.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+
+namespace mozilla::ipc {
+
+using UtilityActorName = mozilla::dom::WebIDLUtilityActorName;
+
+UtilityActorName GetAudioActorName(const SandboxingKind aSandbox);
+nsCString GetChildAudioActorName();
+
+}  // namespace mozilla::ipc
+
+#endif  // _include_ipc_glue_UtilityAudioDecoder_h__
diff --git a/ipc/glue/UtilityAudioDecoderChild.cpp b/ipc/glue/UtilityAudioDecoderChild.cpp
new file mode 100644
index 0000000000..a63775390d
--- /dev/null
+++ b/ipc/glue/UtilityAudioDecoderChild.cpp
@@ -0,0 +1,176 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 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 "UtilityAudioDecoderChild.h"
+
+#include "base/basictypes.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/dom/ContentParent.h"
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+#  include "mozilla/StaticPrefs_media.h"
+#  include "mozilla/gfx/GPUProcessManager.h"
+#  include "mozilla/gfx/gfxVars.h"
+#  include "mozilla/ipc/UtilityProcessManager.h"
+#  include "mozilla/layers/PVideoBridge.h"
+#  include "mozilla/layers/VideoBridgeUtils.h"
+#endif
+
+namespace mozilla::ipc {
+
+NS_IMETHODIMP UtilityAudioDecoderChildShutdownObserver::Observe(
+    nsISupports* aSubject, const char* aTopic, const char16_t* aData) {
+  MOZ_ASSERT(strcmp(aTopic, "ipc:utility-shutdown") == 0);
+
+  nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
+  if (observerService) {
+    observerService->RemoveObserver(this, "ipc:utility-shutdown");
+  }
+
+  UtilityAudioDecoderChild::Shutdown(mSandbox);
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(UtilityAudioDecoderChildShutdownObserver, nsIObserver);
+
+static EnumeratedArray<SandboxingKind, SandboxingKind::COUNT,
+                       StaticRefPtr<UtilityAudioDecoderChild>>
+    sAudioDecoderChilds;
+
+UtilityAudioDecoderChild::UtilityAudioDecoderChild(SandboxingKind aKind)
+    : mSandbox(aKind), mAudioDecoderChildStart(TimeStamp::Now()) {
+  MOZ_ASSERT(NS_IsMainThread());
+  nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
+  if (observerService) {
+    auto* obs = new UtilityAudioDecoderChildShutdownObserver(aKind);
+    observerService->AddObserver(obs, "ipc:utility-shutdown", false);
+  }
+}
+
+void UtilityAudioDecoderChild::ActorDestroy(ActorDestroyReason aReason) {
+  MOZ_ASSERT(NS_IsMainThread());
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  if (mSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM) {
+    gfx::gfxVars::RemoveReceiver(this);
+  }
+#endif
+  Shutdown(mSandbox);
+}
+
+void UtilityAudioDecoderChild::Bind(
+    Endpoint<PUtilityAudioDecoderChild>&& aEndpoint) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (NS_WARN_IF(!aEndpoint.Bind(this))) {
+    MOZ_ASSERT_UNREACHABLE("Failed to bind UtilityAudioDecoderChild!");
+    return;
+  }
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  if (mSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM) {
+    gfx::gfxVars::AddReceiver(this);
+  }
+#endif
+}
+
+/* static */
+void UtilityAudioDecoderChild::Shutdown(SandboxingKind aKind) {
+  sAudioDecoderChilds[aKind] = nullptr;
+}
+
+/* static */
+RefPtr<UtilityAudioDecoderChild> UtilityAudioDecoderChild::GetSingleton(
+    SandboxingKind aKind) {
+  MOZ_ASSERT(NS_IsMainThread());
+  bool shutdown = AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown);
+  if (!sAudioDecoderChilds[aKind] && !shutdown) {
+    sAudioDecoderChilds[aKind] = new UtilityAudioDecoderChild(aKind);
+  }
+  return sAudioDecoderChilds[aKind];
+}
+
+mozilla::ipc::IPCResult
+UtilityAudioDecoderChild::RecvUpdateMediaCodecsSupported(
+    const RemoteDecodeIn& aLocation,
+    const media::MediaCodecsSupported& aSupported) {
+  dom::ContentParent::BroadcastMediaCodecsSupportedUpdate(aLocation,
+                                                          aSupported);
+  return IPC_OK();
+}
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+mozilla::ipc::IPCResult
+UtilityAudioDecoderChild::RecvCompleteCreatedVideoBridge() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM);
+  mHasCreatedVideoBridge = true;
+  return IPC_OK();
+}
+
+bool UtilityAudioDecoderChild::HasCreatedVideoBridge() const {
+  MOZ_ASSERT(NS_IsMainThread());
+  return mHasCreatedVideoBridge;
+}
+
+void UtilityAudioDecoderChild::OnVarChanged(const gfx::GfxVarUpdate& aVar) {
+  MOZ_ASSERT(mSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM);
+  SendUpdateVar(aVar);
+}
+
+void UtilityAudioDecoderChild::OnCompositorUnexpectedShutdown() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM);
+  mHasCreatedVideoBridge = false;
+  CreateVideoBridge();
+}
+
+bool UtilityAudioDecoderChild::CreateVideoBridge() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM);
+
+  if (HasCreatedVideoBridge()) {
+    return true;
+  }
+
+  // Build content device data first; this ensure that the GPU process is fully
+  // ready.
+  gfx::ContentDeviceData contentDeviceData;
+  gfxPlatform::GetPlatform()->BuildContentDeviceData(&contentDeviceData);
+
+  gfx::GPUProcessManager* gpuManager = gfx::GPUProcessManager::Get();
+  if (!gpuManager) {
+    NS_WARNING("Failed to get a gpu mananger!");
+    return false;
+  }
+
+  // The child end is the producer of video frames; the parent end is the
+  // consumer.
+  base::ProcessId childPid = UtilityProcessManager::GetSingleton()
+                                 ->GetProcessParent(mSandbox)
+                                 ->OtherPid();
+  base::ProcessId parentPid = gpuManager->GPUProcessPid();
+  if (parentPid == base::kInvalidProcessId) {
+    NS_WARNING("GPU process Id is invald!");
+    return false;
+  }
+
+  ipc::Endpoint<layers::PVideoBridgeParent> parentPipe;
+  ipc::Endpoint<layers::PVideoBridgeChild> childPipe;
+  nsresult rv = layers::PVideoBridge::CreateEndpoints(parentPid, childPid,
+                                                      &parentPipe, &childPipe);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to create endpoints for video bridge!");
+    return false;
+  }
+
+  nsTArray<gfx::GfxVarUpdate> updates = gfx::gfxVars::FetchNonDefaultVars();
+  gpuManager->InitVideoBridge(
+      std::move(parentPipe),
+      layers::VideoBridgeSource::MFMediaEngineCDMProcess);
+  SendInitVideoBridge(std::move(childPipe), updates, contentDeviceData);
+  return true;
+}
+#endif
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityAudioDecoderChild.h b/ipc/glue/UtilityAudioDecoderChild.h
new file mode 100644
index 0000000000..360a7cb6be
--- /dev/null
+++ b/ipc/glue/UtilityAudioDecoderChild.h
@@ -0,0 +1,127 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 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 _include_ipc_glue_UtilityAudioDecoderChild_h__
+#define _include_ipc_glue_UtilityAudioDecoderChild_h__
+
+#include "mozilla/ProcInfo.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "mozilla/RefPtr.h"
+
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "mozilla/ipc/UtilityAudioDecoder.h"
+#include "mozilla/ipc/PUtilityAudioDecoderChild.h"
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+#  include "mozilla/gfx/GPUProcessListener.h"
+#  include "mozilla/gfx/gfxVarReceiver.h"
+#endif
+
+#include "PDMFactory.h"
+
+namespace mozilla::ipc {
+
+class UtilityAudioDecoderChildShutdownObserver : public nsIObserver {
+ public:
+  explicit UtilityAudioDecoderChildShutdownObserver(SandboxingKind aKind)
+      : mSandbox(aKind){};
+
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHOD Observe(nsISupports* aSubject, const char* aTopic,
+                     const char16_t* aData) override;
+
+ private:
+  virtual ~UtilityAudioDecoderChildShutdownObserver() = default;
+
+  const SandboxingKind mSandbox;
+};
+
+// This controls performing audio decoding on the utility process and it is
+// intended to live on the main process side
+class UtilityAudioDecoderChild final : public PUtilityAudioDecoderChild
+#ifdef MOZ_WMF_MEDIA_ENGINE
+    ,
+                                       public gfx::gfxVarReceiver,
+                                       public gfx::GPUProcessListener
+#endif
+{
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(UtilityAudioDecoderChild, override);
+  mozilla::ipc::IPCResult RecvUpdateMediaCodecsSupported(
+      const RemoteDecodeIn& aLocation,
+      const media::MediaCodecsSupported& aSupported);
+
+  UtilityActorName GetActorName() { return GetAudioActorName(mSandbox); }
+
+  nsresult BindToUtilityProcess(RefPtr<UtilityProcessParent> aUtilityParent) {
+    Endpoint<PUtilityAudioDecoderChild> utilityAudioDecoderChildEnd;
+    Endpoint<PUtilityAudioDecoderParent> utilityAudioDecoderParentEnd;
+    nsresult rv = PUtilityAudioDecoder::CreateEndpoints(
+        aUtilityParent->OtherPid(), base::GetCurrentProcId(),
+        &utilityAudioDecoderParentEnd, &utilityAudioDecoderChildEnd);
+
+    if (NS_FAILED(rv)) {
+      MOZ_ASSERT(false, "Protocol endpoints failure");
+      return NS_ERROR_FAILURE;
+    }
+
+    if (!aUtilityParent->SendStartUtilityAudioDecoderService(
+            std::move(utilityAudioDecoderParentEnd))) {
+      MOZ_ASSERT(false, "StartUtilityAudioDecoder service failure");
+      return NS_ERROR_FAILURE;
+    }
+
+    Bind(std::move(utilityAudioDecoderChildEnd));
+
+    PROFILER_MARKER_UNTYPED(
+        "UtilityAudioDecoderChild::BindToUtilityProcess", IPC,
+        MarkerOptions(
+            MarkerTiming::IntervalUntilNowFrom(mAudioDecoderChildStart)));
+    return NS_OK;
+  }
+
+  void ActorDestroy(ActorDestroyReason aReason) override;
+
+  void Bind(Endpoint<PUtilityAudioDecoderChild>&& aEndpoint);
+
+  static void Shutdown(SandboxingKind aKind);
+
+  static RefPtr<UtilityAudioDecoderChild> GetSingleton(SandboxingKind aKind);
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  mozilla::ipc::IPCResult RecvCompleteCreatedVideoBridge();
+
+  bool HasCreatedVideoBridge() const;
+
+  void OnVarChanged(const gfx::GfxVarUpdate& aVar) override;
+
+  void OnCompositorUnexpectedShutdown() override;
+
+  // True if creating a video bridge sucessfully. Currently only used for media
+  // engine cdm.
+  bool CreateVideoBridge();
+#endif
+
+ private:
+  explicit UtilityAudioDecoderChild(SandboxingKind aKind);
+  ~UtilityAudioDecoderChild() = default;
+
+  const SandboxingKind mSandbox;
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  // True if the utility process has created a video bridge with the GPU prcess.
+  // Currently only used for media egine cdm. Main thread only.
+  bool mHasCreatedVideoBridge = false;
+#endif
+
+  TimeStamp mAudioDecoderChildStart;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // _include_ipc_glue_UtilityAudioDecoderChild_h__
diff --git a/ipc/glue/UtilityAudioDecoderParent.cpp b/ipc/glue/UtilityAudioDecoderParent.cpp
new file mode 100644
index 0000000000..edec21c5ee
--- /dev/null
+++ b/ipc/glue/UtilityAudioDecoderParent.cpp
@@ -0,0 +1,173 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 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 "UtilityAudioDecoderParent.h"
+
+#include "GeckoProfiler.h"
+#include "nsDebugImpl.h"
+
+#include "mozilla/RemoteDecoderManagerParent.h"
+#include "PDMFactory.h"
+
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+#  include "WMF.h"
+#  include "WMFDecoderModule.h"
+#  include "WMFUtils.h"
+
+#  include "mozilla/sandboxTarget.h"
+#  include "mozilla/ipc/UtilityProcessImpl.h"
+#endif  // defined(XP_WIN) && defined(MOZ_SANDBOX)
+
+#ifdef MOZ_WIDGET_ANDROID
+#  include "mozilla/StaticPrefs_media.h"
+#  include "AndroidDecoderModule.h"
+#endif
+
+#include "mozilla/ipc/UtilityProcessChild.h"
+#include "mozilla/RemoteDecodeUtils.h"
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+#  include "mozilla/gfx/DeviceManagerDx.h"
+#  include "mozilla/gfx/gfxVars.h"
+#  include "gfxConfig.h"
+#endif
+
+namespace mozilla::ipc {
+
+UtilityAudioDecoderParent::UtilityAudioDecoderParent()
+    : mKind(GetCurrentSandboxingKind()),
+      mAudioDecoderParentStart(TimeStamp::Now()) {
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  if (mKind == SandboxingKind::MF_MEDIA_ENGINE_CDM) {
+    nsDebugImpl::SetMultiprocessMode("MF Media Engine CDM");
+    profiler_set_process_name(nsCString("MF Media Engine CDM"));
+    gfx::gfxConfig::Init();
+    gfx::gfxVars::Initialize();
+    gfx::DeviceManagerDx::Init();
+    return;
+  }
+#endif
+  if (GetCurrentSandboxingKind() != SandboxingKind::GENERIC_UTILITY) {
+    nsDebugImpl::SetMultiprocessMode("Utility AudioDecoder");
+    profiler_set_process_name(nsCString("Utility AudioDecoder"));
+  }
+}
+
+UtilityAudioDecoderParent::~UtilityAudioDecoderParent() {
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  if (mKind == SandboxingKind::MF_MEDIA_ENGINE_CDM) {
+    gfx::gfxConfig::Shutdown();
+    gfx::gfxVars::Shutdown();
+    gfx::DeviceManagerDx::Shutdown();
+  }
+#endif
+}
+
+/* static */
+void UtilityAudioDecoderParent::GenericPreloadForSandbox() {
+#if defined(MOZ_SANDBOX) && defined(XP_WIN) && defined(MOZ_FFVPX)
+  // Preload AV dlls so we can enable Binary Signature Policy
+  // to restrict further dll loads.
+  UtilityProcessImpl::LoadLibraryOrCrash(L"mozavcodec.dll");
+  UtilityProcessImpl::LoadLibraryOrCrash(L"mozavutil.dll");
+#endif  // defined(MOZ_SANDBOX) && defined(XP_WIN) && defined(MOZ_FFVPX)
+}
+
+/* static */
+void UtilityAudioDecoderParent::WMFPreloadForSandbox() {
+#if defined(MOZ_SANDBOX) && defined(OS_WIN)
+  // mfplat.dll and mf.dll will be preloaded by
+  // wmf::MediaFoundationInitializer::HasInitialized()
+#  if defined(DEBUG)
+  // WMF Shutdown on debug build somehow requires this
+  UtilityProcessImpl::LoadLibraryOrCrash(L"ole32.dll");
+#  endif  // defined(DEBUG)
+
+  auto rv = wmf::MediaFoundationInitializer::HasInitialized();
+  if (!rv) {
+    NS_WARNING("Failed to init Media Foundation in the Utility process");
+    return;
+  }
+#endif  // defined(MOZ_SANDBOX) && defined(OS_WIN)
+}
+
+void UtilityAudioDecoderParent::Start(
+    Endpoint<PUtilityAudioDecoderParent>&& aEndpoint) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  DebugOnly<bool> ok = std::move(aEndpoint).Bind(this);
+  MOZ_ASSERT(ok);
+
+#ifdef MOZ_WIDGET_ANDROID
+  if (StaticPrefs::media_utility_android_media_codec_enabled()) {
+    AndroidDecoderModule::SetSupportedMimeTypes(
+        AndroidDecoderModule::GetSupportedMimeTypes());
+  }
+#endif
+
+  auto supported = PDMFactory::Supported();
+  Unused << SendUpdateMediaCodecsSupported(GetRemoteDecodeInFromKind(mKind),
+                                           supported);
+  PROFILER_MARKER_UNTYPED("UtilityAudioDecoderParent::Start", IPC,
+                          MarkerOptions(MarkerTiming::IntervalUntilNowFrom(
+                              mAudioDecoderParentStart)));
+}
+
+mozilla::ipc::IPCResult
+UtilityAudioDecoderParent::RecvNewContentRemoteDecoderManager(
+    Endpoint<PRemoteDecoderManagerParent>&& aEndpoint,
+    const ContentParentId& aParentId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!RemoteDecoderManagerParent::CreateForContent(std::move(aEndpoint),
+                                                    aParentId)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+mozilla::ipc::IPCResult UtilityAudioDecoderParent::RecvInitVideoBridge(
+    Endpoint<PVideoBridgeChild>&& aEndpoint,
+    nsTArray<gfx::GfxVarUpdate>&& aUpdates,
+    const ContentDeviceData& aContentDeviceData) {
+  MOZ_ASSERT(mKind == SandboxingKind::MF_MEDIA_ENGINE_CDM);
+  if (!RemoteDecoderManagerParent::CreateVideoBridgeToOtherProcess(
+          std::move(aEndpoint))) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  for (const auto& update : aUpdates) {
+    gfx::gfxVars::ApplyUpdate(update);
+  }
+
+  gfx::gfxConfig::Inherit(
+      {
+          gfx::Feature::HW_COMPOSITING,
+          gfx::Feature::D3D11_COMPOSITING,
+          gfx::Feature::OPENGL_COMPOSITING,
+          gfx::Feature::DIRECT2D,
+      },
+      aContentDeviceData.prefs());
+
+  if (gfx::gfxConfig::IsEnabled(gfx::Feature::D3D11_COMPOSITING)) {
+    if (auto* devmgr = gfx::DeviceManagerDx::Get()) {
+      devmgr->ImportDeviceInfo(aContentDeviceData.d3d11());
+    }
+  }
+
+  Unused << SendCompleteCreatedVideoBridge();
+  return IPC_OK();
+}
+
+IPCResult UtilityAudioDecoderParent::RecvUpdateVar(
+    const GfxVarUpdate& aUpdate) {
+  MOZ_ASSERT(mKind == SandboxingKind::MF_MEDIA_ENGINE_CDM);
+  gfx::gfxVars::ApplyUpdate(aUpdate);
+  return IPC_OK();
+}
+#endif
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityAudioDecoderParent.h b/ipc/glue/UtilityAudioDecoderParent.h
new file mode 100644
index 0000000000..37c9c12433
--- /dev/null
+++ b/ipc/glue/UtilityAudioDecoderParent.h
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 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 _include_ipc_glue_UtilityAudioDecoderParent_h_
+#define _include_ipc_glue_UtilityAudioDecoderParent_h_
+
+#include "mozilla/PRemoteDecoderManagerParent.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "mozilla/UniquePtr.h"
+
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/PUtilityAudioDecoderParent.h"
+
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+
+#include "nsThreadManager.h"
+
+namespace mozilla::ipc {
+
+// This is in charge of handling the utility child process side to perform
+// audio decoding
+class UtilityAudioDecoderParent final : public PUtilityAudioDecoderParent {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(UtilityAudioDecoderParent, override);
+
+  UtilityAudioDecoderParent();
+
+  static void GenericPreloadForSandbox();
+  static void WMFPreloadForSandbox();
+
+  void Start(Endpoint<PUtilityAudioDecoderParent>&& aEndpoint);
+
+  mozilla::ipc::IPCResult RecvNewContentRemoteDecoderManager(
+      Endpoint<PRemoteDecoderManagerParent>&& aEndpoint,
+      const ContentParentId& aParentId);
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  mozilla::ipc::IPCResult RecvInitVideoBridge(
+      Endpoint<PVideoBridgeChild>&& aEndpoint,
+      nsTArray<mozilla::gfx::GfxVarUpdate>&& aUpdates,
+      const ContentDeviceData& aContentDeviceData);
+
+  IPCResult RecvUpdateVar(const mozilla::gfx::GfxVarUpdate& aUpdate);
+#endif
+
+ private:
+  ~UtilityAudioDecoderParent();
+
+  const SandboxingKind mKind;
+  TimeStamp mAudioDecoderParentStart;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // _include_ipc_glue_UtilityAudioDecoderParent_h_
diff --git a/ipc/glue/UtilityProcessChild.cpp b/ipc/glue/UtilityProcessChild.cpp
new file mode 100644
index 0000000000..b64c20705b
--- /dev/null
+++ b/ipc/glue/UtilityProcessChild.cpp
@@ -0,0 +1,381 @@
+/* -*- 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 "UtilityProcessChild.h"
+
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/JSOracleChild.h"
+#include "mozilla/dom/MemoryReportRequest.h"
+#include "mozilla/ipc/CrashReporterClient.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/RemoteDecoderManagerParent.h"
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+#  include "mozilla/Sandbox.h"
+#endif
+
+#if defined(XP_OPENBSD) && defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxSettings.h"
+#endif
+
+#if defined(MOZ_SANDBOX) && defined(MOZ_DEBUG) && defined(ENABLE_TESTS)
+#  include "mozilla/SandboxTestingChild.h"
+#endif
+
+#include "mozilla/Telemetry.h"
+
+#if defined(XP_WIN)
+#  include "mozilla/WinDllServices.h"
+#  include "mozilla/dom/WindowsUtilsChild.h"
+#endif
+
+#include "nsDebugImpl.h"
+#include "nsIXULRuntime.h"
+#include "nsThreadManager.h"
+#include "GeckoProfiler.h"
+
+#include "mozilla/ipc/ProcessChild.h"
+#include "mozilla/FOGIPC.h"
+#include "mozilla/glean/GleanMetrics.h"
+
+#include "mozilla/Services.h"
+
+namespace mozilla::ipc {
+
+using namespace layers;
+
+static StaticMutex sUtilityProcessChildMutex;
+static StaticRefPtr<UtilityProcessChild> sUtilityProcessChild
+    MOZ_GUARDED_BY(sUtilityProcessChildMutex);
+
+UtilityProcessChild::UtilityProcessChild() : mChildStartTime(TimeStamp::Now()) {
+  nsDebugImpl::SetMultiprocessMode("Utility");
+}
+
+UtilityProcessChild::~UtilityProcessChild() = default;
+
+/* static */
+RefPtr<UtilityProcessChild> UtilityProcessChild::GetSingleton() {
+  MOZ_ASSERT(XRE_IsUtilityProcess());
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownFinal)) {
+    return nullptr;
+  }
+  StaticMutexAutoLock lock(sUtilityProcessChildMutex);
+  if (!sUtilityProcessChild) {
+    sUtilityProcessChild = new UtilityProcessChild();
+  }
+  return sUtilityProcessChild;
+}
+
+/* static */
+RefPtr<UtilityProcessChild> UtilityProcessChild::Get() {
+  StaticMutexAutoLock lock(sUtilityProcessChildMutex);
+  return sUtilityProcessChild;
+}
+
+bool UtilityProcessChild::Init(mozilla::ipc::UntypedEndpoint&& aEndpoint,
+                               const nsCString& aParentBuildID,
+                               uint64_t aSandboxingKind) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Initialize the thread manager before starting IPC. Otherwise, messages
+  // may be posted to the main thread and we won't be able to process them.
+  if (NS_WARN_IF(NS_FAILED(nsThreadManager::get().Init()))) {
+    return false;
+  }
+
+  // Now it's safe to start IPC.
+  if (NS_WARN_IF(!aEndpoint.Bind(this))) {
+    return false;
+  }
+
+  // This must be checked before any IPDL message, which may hit sentinel
+  // errors due to parent and content processes having different
+  // versions.
+  MessageChannel* channel = GetIPCChannel();
+  if (channel && !channel->SendBuildIDsMatchMessage(aParentBuildID.get())) {
+    // We need to quit this process if the buildID doesn't match the parent's.
+    // This can occur when an update occurred in the background.
+    ipc::ProcessChild::QuickExit();
+  }
+
+  // Init crash reporter support.
+  ipc::CrashReporterClient::InitSingleton(this);
+
+  if (NS_FAILED(NS_InitMinimalXPCOM())) {
+    return false;
+  }
+
+  mSandbox = (SandboxingKind)aSandboxingKind;
+
+  // At the moment, only ORB uses JSContext in the
+  // Utility Process and ORB uses GENERIC_UTILITY
+  if (mSandbox == SandboxingKind::GENERIC_UTILITY) {
+    JS::DisableJitBackend();
+    if (!JS_Init()) {
+      return false;
+    }
+#if defined(__OpenBSD__) && defined(MOZ_SANDBOX)
+    // Bug 1823458: delay pledge initialization, otherwise
+    // JS_Init triggers sysctl(KERN_PROC_ID) which isnt
+    // permitted with the current pledge.utility config
+    StartOpenBSDSandbox(GeckoProcessType_Utility, mSandbox);
+#endif
+  }
+
+  profiler_set_process_name(nsCString("Utility Process"));
+
+  // Notify the parent process that we have finished our init and that it can
+  // now resolve the pending promise of process startup
+  SendInitCompleted();
+
+  PROFILER_MARKER_UNTYPED(
+      "UtilityProcessChild::SendInitCompleted", IPC,
+      MarkerOptions(MarkerTiming::IntervalUntilNowFrom(mChildStartTime)));
+
+  RunOnShutdown(
+      [sandboxKind = mSandbox] {
+        StaticMutexAutoLock lock(sUtilityProcessChildMutex);
+        sUtilityProcessChild = nullptr;
+        if (sandboxKind == SandboxingKind::GENERIC_UTILITY) {
+          JS_ShutDown();
+        }
+      },
+      ShutdownPhase::XPCOMShutdownFinal);
+
+  return true;
+}
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+extern "C" {
+void CGSShutdownServerConnections();
+};
+#endif
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvInit(
+    const Maybe<FileDescriptor>& aBrokerFd,
+    const bool& aCanRecordReleaseTelemetry,
+    const bool& aIsReadyForBackgroundProcessing) {
+  // Do this now (before closing WindowServer on macOS) to avoid risking
+  // blocking in GetCurrentProcess() called on that platform
+  mozilla::ipc::SetThisProcessName("Utility Process");
+
+#if defined(MOZ_SANDBOX)
+#  if defined(XP_MACOSX)
+  // Close all current connections to the WindowServer. This ensures that the
+  // Activity Monitor will not label the content process as "Not responding"
+  // because it's not running a native event loop. See bug 1384336.
+  CGSShutdownServerConnections();
+
+#  elif defined(XP_LINUX)
+  int fd = -1;
+  if (aBrokerFd.isSome()) {
+    fd = aBrokerFd.value().ClonePlatformHandle().release();
+  }
+
+  SetUtilitySandbox(fd, mSandbox);
+
+#  endif  // XP_MACOSX/XP_LINUX
+#endif    // MOZ_SANDBOX
+
+#if defined(XP_WIN)
+  if (aCanRecordReleaseTelemetry) {
+    RefPtr<DllServices> dllSvc(DllServices::Get());
+    dllSvc->StartUntrustedModulesProcessor(aIsReadyForBackgroundProcessing);
+  }
+#endif  // defined(XP_WIN)
+
+  PROFILER_MARKER_UNTYPED(
+      "UtilityProcessChild::RecvInit", IPC,
+      MarkerOptions(MarkerTiming::IntervalUntilNowFrom(mChildStartTime)));
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvPreferenceUpdate(
+    const Pref& aPref) {
+  Preferences::SetPreference(aPref);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvInitProfiler(
+    Endpoint<PProfilerChild>&& aEndpoint) {
+  mProfilerController = ChildProfilerController::Create(std::move(aEndpoint));
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvRequestMemoryReport(
+    const uint32_t& aGeneration, const bool& aAnonymize,
+    const bool& aMinimizeMemoryUsage, const Maybe<FileDescriptor>& aDMDFile,
+    const RequestMemoryReportResolver& aResolver) {
+  nsPrintfCString processName("Utility (pid %" PRIPID
+                              ", sandboxingKind %" PRIu64 ")",
+                              base::GetCurrentProcId(), mSandbox);
+
+  mozilla::dom::MemoryReportRequestClient::Start(
+      aGeneration, aAnonymize, aMinimizeMemoryUsage, aDMDFile, processName,
+      [&](const MemoryReport& aReport) {
+        Unused << GetSingleton()->SendAddMemoryReport(aReport);
+      },
+      aResolver);
+  return IPC_OK();
+}
+
+#if defined(MOZ_SANDBOX) && defined(MOZ_DEBUG) && defined(ENABLE_TESTS)
+mozilla::ipc::IPCResult UtilityProcessChild::RecvInitSandboxTesting(
+    Endpoint<PSandboxTestingChild>&& aEndpoint) {
+  if (!SandboxTestingChild::Initialize(std::move(aEndpoint))) {
+    return IPC_FAIL(
+        this, "InitSandboxTesting failed to initialise the child process.");
+  }
+  return IPC_OK();
+}
+#endif
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvFlushFOGData(
+    FlushFOGDataResolver&& aResolver) {
+  glean::FlushFOGData(std::move(aResolver));
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvTestTriggerMetrics(
+    TestTriggerMetricsResolver&& aResolve) {
+  mozilla::glean::test_only_ipc::a_counter.Add(
+      nsIXULRuntime::PROCESS_TYPE_UTILITY);
+  aResolve(true);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvTestTelemetryProbes() {
+  const uint32_t kExpectedUintValue = 42;
+  Telemetry::ScalarSet(Telemetry::ScalarID::TELEMETRY_TEST_UTILITY_ONLY_UINT,
+                       kExpectedUintValue);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+UtilityProcessChild::RecvStartUtilityAudioDecoderService(
+    Endpoint<PUtilityAudioDecoderParent>&& aEndpoint) {
+  PROFILER_MARKER_UNTYPED(
+      "UtilityProcessChild::RecvStartUtilityAudioDecoderService", MEDIA,
+      MarkerOptions(MarkerTiming::IntervalUntilNowFrom(mChildStartTime)));
+  mUtilityAudioDecoderInstance = new UtilityAudioDecoderParent();
+  if (!mUtilityAudioDecoderInstance) {
+    return IPC_FAIL(this, "Failing to create UtilityAudioDecoderParent");
+  }
+
+  mUtilityAudioDecoderInstance->Start(std::move(aEndpoint));
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvStartJSOracleService(
+    Endpoint<PJSOracleChild>&& aEndpoint) {
+  PROFILER_MARKER_UNTYPED(
+      "UtilityProcessChild::RecvStartJSOracleService", JS,
+      MarkerOptions(MarkerTiming::IntervalUntilNowFrom(mChildStartTime)));
+  mJSOracleInstance = new mozilla::dom::JSOracleChild();
+  if (!mJSOracleInstance) {
+    return IPC_FAIL(this, "Failing to create JSOracleParent");
+  }
+
+  mJSOracleInstance->Start(std::move(aEndpoint));
+  return IPC_OK();
+}
+
+#if defined(XP_WIN)
+mozilla::ipc::IPCResult UtilityProcessChild::RecvStartWindowsUtilsService(
+    Endpoint<dom::PWindowsUtilsChild>&& aEndpoint) {
+  PROFILER_MARKER_UNTYPED(
+      "UtilityProcessChild::RecvStartWindowsUtilsService", OTHER,
+      MarkerOptions(MarkerTiming::IntervalUntilNowFrom(mChildStartTime)));
+  mWindowsUtilsInstance = new dom::WindowsUtilsChild();
+  if (!mWindowsUtilsInstance) {
+    return IPC_FAIL(this, "Failed to create WindowsUtilsChild");
+  }
+
+  [[maybe_unused]] bool ok = std::move(aEndpoint).Bind(mWindowsUtilsInstance);
+  MOZ_ASSERT(ok);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessChild::RecvGetUntrustedModulesData(
+    GetUntrustedModulesDataResolver&& aResolver) {
+  RefPtr<DllServices> dllSvc(DllServices::Get());
+  dllSvc->GetUntrustedModulesData()->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [aResolver](Maybe<UntrustedModulesData>&& aData) {
+        aResolver(std::move(aData));
+      },
+      [aResolver](nsresult aReason) { aResolver(Nothing()); });
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+UtilityProcessChild::RecvUnblockUntrustedModulesThread() {
+  if (nsCOMPtr<nsIObserverService> obs =
+          mozilla::services::GetObserverService()) {
+    obs->NotifyObservers(nullptr, "unblock-untrusted-modules-thread", nullptr);
+  }
+  return IPC_OK();
+}
+#endif  // defined(XP_WIN)
+
+void UtilityProcessChild::ActorDestroy(ActorDestroyReason aWhy) {
+  if (AbnormalShutdown == aWhy) {
+    NS_WARNING("Shutting down Utility process early due to a crash!");
+    ipc::ProcessChild::QuickExit();
+  }
+
+  // Send the last bits of Glean data over to the main process.
+  glean::FlushFOGData(
+      [](ByteBuf&& aBuf) { glean::SendFOGData(std::move(aBuf)); });
+
+#ifndef NS_FREE_PERMANENT_DATA
+  ProcessChild::QuickExit();
+#else
+
+  if (mProfilerController) {
+    mProfilerController->Shutdown();
+    mProfilerController = nullptr;
+  }
+
+  uint32_t timeout = 0;
+  if (mUtilityAudioDecoderInstance) {
+    mUtilityAudioDecoderInstance = nullptr;
+    timeout = 10 * 1000;
+  }
+
+  mJSOracleInstance = nullptr;
+
+#  ifdef XP_WIN
+  mWindowsUtilsInstance = nullptr;
+#  endif
+
+  // Wait until all RemoteDecoderManagerParent have closed.
+  // It is still possible some may not have clean up yet, and we might hit
+  // timeout. Our xpcom-shutdown listener should take care of cleaning the
+  // reference of our singleton.
+  //
+  // FIXME: Should move from using AsyncBlockers to proper
+  // nsIAsyncShutdownService once it is not JS, see bug 1760855
+  mShutdownBlockers.WaitUntilClear(timeout)->Then(
+      GetCurrentSerialEventTarget(), __func__, [&]() {
+#  ifdef XP_WIN
+        {
+          RefPtr<DllServices> dllSvc(DllServices::Get());
+          dllSvc->DisableFull();
+        }
+#  endif  // defined(XP_WIN)
+
+        ipc::CrashReporterClient::DestroySingleton();
+        XRE_ShutdownChildProcess();
+      });
+#endif    // NS_FREE_PERMANENT_DATA
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityProcessChild.h b/ipc/glue/UtilityProcessChild.h
new file mode 100644
index 0000000000..423922cafc
--- /dev/null
+++ b/ipc/glue/UtilityProcessChild.h
@@ -0,0 +1,104 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessChild_h_
+#define _include_ipc_glue_UtilityProcessChild_h_
+#include "mozilla/ipc/PUtilityProcessChild.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "mozilla/ipc/UtilityAudioDecoderParent.h"
+#include "mozilla/UniquePtr.h"
+#include "ChildProfilerController.h"
+
+#include "mozilla/PRemoteDecoderManagerParent.h"
+#include "mozilla/ipc/AsyncBlockers.h"
+#include "mozilla/dom/JSOracleChild.h"
+#include "mozilla/ProfilerMarkers.h"
+
+namespace mozilla::dom {
+class PJSOracleChild;
+}  // namespace mozilla::dom
+
+namespace mozilla::ipc {
+
+class UtilityProcessHost;
+
+class UtilityProcessChild final : public PUtilityProcessChild {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(UtilityProcessChild, override);
+
+  UtilityProcessChild();
+
+  static RefPtr<UtilityProcessChild> GetSingleton();
+  static RefPtr<UtilityProcessChild> Get();
+
+  SandboxingKind mSandbox{};
+
+  bool Init(mozilla::ipc::UntypedEndpoint&& aEndpoint,
+            const nsCString& aParentBuildID, uint64_t aSandboxingKind);
+
+  mozilla::ipc::IPCResult RecvInit(const Maybe<ipc::FileDescriptor>& aBrokerFd,
+                                   const bool& aCanRecordReleaseTelemetry,
+                                   const bool& aIsReadyForBackgroundProcessing);
+  mozilla::ipc::IPCResult RecvInitProfiler(
+      Endpoint<PProfilerChild>&& aEndpoint);
+
+  mozilla::ipc::IPCResult RecvPreferenceUpdate(const Pref& pref);
+
+  mozilla::ipc::IPCResult RecvRequestMemoryReport(
+      const uint32_t& generation, const bool& anonymize,
+      const bool& minimizeMemoryUsage,
+      const Maybe<ipc::FileDescriptor>& DMDFile,
+      const RequestMemoryReportResolver& aResolver);
+
+  mozilla::ipc::IPCResult RecvFlushFOGData(FlushFOGDataResolver&& aResolver);
+
+  mozilla::ipc::IPCResult RecvTestTriggerMetrics(
+      TestTriggerMetricsResolver&& aResolve);
+
+  mozilla::ipc::IPCResult RecvTestTelemetryProbes();
+
+  mozilla::ipc::IPCResult RecvStartUtilityAudioDecoderService(
+      Endpoint<PUtilityAudioDecoderParent>&& aEndpoint);
+
+  mozilla::ipc::IPCResult RecvStartJSOracleService(
+      Endpoint<dom::PJSOracleChild>&& aEndpoint);
+
+#if defined(XP_WIN)
+  mozilla::ipc::IPCResult RecvStartWindowsUtilsService(
+      Endpoint<PWindowsUtilsChild>&& aEndpoint);
+
+  mozilla::ipc::IPCResult RecvGetUntrustedModulesData(
+      GetUntrustedModulesDataResolver&& aResolver);
+  mozilla::ipc::IPCResult RecvUnblockUntrustedModulesThread();
+#endif  // defined(XP_WIN)
+
+  AsyncBlockers& AsyncShutdownService() { return mShutdownBlockers; }
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+#if defined(MOZ_SANDBOX) && defined(MOZ_DEBUG) && defined(ENABLE_TESTS)
+  mozilla::ipc::IPCResult RecvInitSandboxTesting(
+      Endpoint<PSandboxTestingChild>&& aEndpoint);
+#endif
+
+ protected:
+  friend class UtilityProcessImpl;
+  ~UtilityProcessChild();
+
+ private:
+  TimeStamp mChildStartTime;
+  RefPtr<ChildProfilerController> mProfilerController;
+  RefPtr<UtilityAudioDecoderParent> mUtilityAudioDecoderInstance{};
+  RefPtr<dom::JSOracleChild> mJSOracleInstance{};
+#ifdef XP_WIN
+  RefPtr<PWindowsUtilsChild> mWindowsUtilsInstance;
+#endif
+
+  AsyncBlockers mShutdownBlockers;
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // _include_ipc_glue_UtilityProcessChild_h_
diff --git a/ipc/glue/UtilityProcessHost.cpp b/ipc/glue/UtilityProcessHost.cpp
new file mode 100644
index 0000000000..b5a9c229c5
--- /dev/null
+++ b/ipc/glue/UtilityProcessHost.cpp
@@ -0,0 +1,353 @@
+/* -*- 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 "UtilityProcessHost.h"
+
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "mozilla/Telemetry.h"
+
+#include "chrome/common/process_watcher.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_general.h"
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+#  include "mozilla/Sandbox.h"
+#endif
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxBrokerPolicyFactory.h"
+#endif
+
+#if defined(XP_WIN)
+#  include "mozilla/WinDllServices.h"
+#endif  // defined(XP_WIN)
+
+#include "ProfilerParent.h"
+#include "mozilla/PProfilerChild.h"
+
+namespace mozilla::ipc {
+
+LazyLogModule gUtilityProcessLog("utilityproc");
+#define LOGD(...) MOZ_LOG(gUtilityProcessLog, LogLevel::Debug, (__VA_ARGS__))
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+bool UtilityProcessHost::sLaunchWithMacSandbox = false;
+#endif
+
+UtilityProcessHost::UtilityProcessHost(SandboxingKind aSandbox,
+                                       RefPtr<Listener> aListener)
+    : GeckoChildProcessHost(GeckoProcessType_Utility),
+      mListener(std::move(aListener)),
+      mLiveToken(new media::Refcountable<bool>(true)),
+      mLaunchPromise(
+          MakeRefPtr<GenericNonExclusivePromise::Private>(__func__)) {
+  MOZ_COUNT_CTOR(UtilityProcessHost);
+  LOGD("[%p] UtilityProcessHost::UtilityProcessHost sandboxingKind=%" PRIu64,
+       this, aSandbox);
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  if (!sLaunchWithMacSandbox) {
+    sLaunchWithMacSandbox =
+        (PR_GetEnv("MOZ_DISABLE_UTILITY_SANDBOX") == nullptr);
+  }
+  mDisableOSActivityMode = sLaunchWithMacSandbox;
+#endif
+#if defined(MOZ_SANDBOX)
+  mSandbox = aSandbox;
+#endif
+}
+
+UtilityProcessHost::~UtilityProcessHost() {
+  MOZ_COUNT_DTOR(UtilityProcessHost);
+#if defined(MOZ_SANDBOX)
+  LOGD("[%p] UtilityProcessHost::~UtilityProcessHost sandboxingKind=%" PRIu64,
+       this, mSandbox);
+#else
+  LOGD("[%p] UtilityProcessHost::~UtilityProcessHost", this);
+#endif
+}
+
+bool UtilityProcessHost::Launch(StringVector aExtraOpts) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  MOZ_ASSERT(mLaunchPhase == LaunchPhase::Unlaunched);
+  MOZ_ASSERT(!mUtilityProcessParent);
+
+  LOGD("[%p] UtilityProcessHost::Launch", this);
+
+  mPrefSerializer = MakeUnique<ipc::SharedPreferenceSerializer>();
+  if (!mPrefSerializer->SerializeToSharedMemory(GeckoProcessType_Utility,
+                                                /* remoteType */ ""_ns)) {
+    return false;
+  }
+  mPrefSerializer->AddSharedPrefCmdLineArgs(*this, aExtraOpts);
+
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+  mSandboxLevel = Preferences::GetInt("security.sandbox.utility.level");
+#endif
+
+  mLaunchPhase = LaunchPhase::Waiting;
+
+  if (!GeckoChildProcessHost::AsyncLaunch(aExtraOpts)) {
+    NS_WARNING("UtilityProcess AsyncLaunch failed, aborting.");
+    mLaunchPhase = LaunchPhase::Complete;
+    mPrefSerializer = nullptr;
+    return false;
+  }
+  LOGD("[%p] UtilityProcessHost::Launch launching async", this);
+  return true;
+}
+
+RefPtr<GenericNonExclusivePromise> UtilityProcessHost::LaunchPromise() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (mLaunchPromiseLaunched) {
+    return mLaunchPromise;
+  }
+
+  WhenProcessHandleReady()->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [this, liveToken = mLiveToken](
+          const ipc::ProcessHandlePromise::ResolveOrRejectValue& aResult) {
+        if (!*liveToken) {
+          // The UtilityProcessHost got deleted. Abort. The promise would have
+          // already been rejected.
+          return;
+        }
+        if (mLaunchCompleted) {
+          return;
+        }
+        mLaunchCompleted = true;
+        if (aResult.IsReject()) {
+          RejectPromise();
+        }
+        // If aResult.IsResolve() then we have succeeded in launching the
+        // Utility process. The promise will be resolved once the channel has
+        // connected (or failed to) later.
+      });
+
+  mLaunchPromiseLaunched = true;
+  return mLaunchPromise;
+}
+
+void UtilityProcessHost::OnChannelConnected(base::ProcessId peer_pid) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost::OnChannelConnected", this);
+
+  GeckoChildProcessHost::OnChannelConnected(peer_pid);
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "UtilityProcessHost::OnChannelConnected",
+      [this, liveToken = mLiveToken]() {
+        if (*liveToken && mLaunchPhase == LaunchPhase::Waiting) {
+          InitAfterConnect(true);
+        }
+      }));
+}
+
+void UtilityProcessHost::OnChannelError() {
+  MOZ_ASSERT(!NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost::OnChannelError", this);
+
+  GeckoChildProcessHost::OnChannelError();
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "UtilityProcessHost::OnChannelError", [this, liveToken = mLiveToken]() {
+        if (*liveToken && mLaunchPhase == LaunchPhase::Waiting) {
+          InitAfterConnect(false);
+        }
+      }));
+}
+
+void UtilityProcessHost::InitAfterConnect(bool aSucceeded) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  MOZ_ASSERT(mLaunchPhase == LaunchPhase::Waiting);
+  MOZ_ASSERT(!mUtilityProcessParent);
+
+  mLaunchPhase = LaunchPhase::Complete;
+
+  if (!aSucceeded) {
+    RejectPromise();
+    return;
+  }
+
+  mUtilityProcessParent = MakeRefPtr<UtilityProcessParent>(this);
+  DebugOnly<bool> rv = TakeInitialEndpoint().Bind(mUtilityProcessParent.get());
+  MOZ_ASSERT(rv);
+
+  // Only clear mPrefSerializer in the success case to avoid a
+  // possible race in the case case of a timeout on Windows launch.
+  // See Bug 1555076 comment 7:
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=1555076#c7
+  mPrefSerializer = nullptr;
+
+  Maybe<FileDescriptor> brokerFd;
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+  UniquePtr<SandboxBroker::Policy> policy;
+  switch (mSandbox) {
+    case SandboxingKind::GENERIC_UTILITY:
+      policy = SandboxBrokerPolicyFactory::GetUtilityProcessPolicy(
+          GetActor()->OtherPid());
+      break;
+
+    default:
+      MOZ_ASSERT(false, "Invalid SandboxingKind");
+      break;
+  }
+  if (policy != nullptr) {
+    brokerFd = Some(FileDescriptor());
+    mSandboxBroker = SandboxBroker::Create(
+        std::move(policy), GetActor()->OtherPid(), brokerFd.ref());
+    // This is unlikely to fail and probably indicates OS resource
+    // exhaustion, but we can at least try to recover.
+    Unused << NS_WARN_IF(mSandboxBroker == nullptr);
+    MOZ_ASSERT(brokerFd.ref().IsValid());
+  }
+#endif  // XP_LINUX && MOZ_SANDBOX
+
+  bool isReadyForBackgroundProcessing = false;
+#if defined(XP_WIN)
+  RefPtr<DllServices> dllSvc(DllServices::Get());
+  isReadyForBackgroundProcessing = dllSvc->IsReadyForBackgroundProcessing();
+#endif
+
+  Unused << GetActor()->SendInit(brokerFd, Telemetry::CanRecordReleaseData(),
+                                 isReadyForBackgroundProcessing);
+
+  Unused << GetActor()->SendInitProfiler(
+      ProfilerParent::CreateForProcess(GetActor()->OtherPid()));
+
+  LOGD("[%p] UtilityProcessHost::InitAfterConnect succeeded", this);
+
+  // Promise will be resolved later, from UtilityProcessParent when the child
+  // will send the InitCompleted message.
+}
+
+void UtilityProcessHost::Shutdown() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(!mShutdownRequested);
+  LOGD("[%p] UtilityProcessHost::Shutdown", this);
+
+  RejectPromise();
+
+  if (mUtilityProcessParent) {
+    LOGD("[%p] UtilityProcessHost::Shutdown not destroying utility process.",
+         this);
+
+    // OnChannelClosed uses this to check if the shutdown was expected or
+    // unexpected.
+    mShutdownRequested = true;
+
+    // The channel might already be closed if we got here unexpectedly.
+    if (mUtilityProcessParent->CanSend()) {
+      mUtilityProcessParent->Close();
+    }
+
+#ifndef NS_FREE_PERMANENT_DATA
+    // No need to communicate shutdown, the Utility process doesn't need to
+    // communicate anything back.
+    KillHard("NormalShutdown");
+#endif
+
+    // If we're shutting down unexpectedly, we're in the middle of handling an
+    // ActorDestroy for PUtilityProcessParent, which is still on the stack.
+    // We'll return back to OnChannelClosed.
+    //
+    // Otherwise, we'll wait for OnChannelClose to be called whenever
+    // PUtilityProcessParent acknowledges shutdown.
+    return;
+  }
+
+  DestroyProcess();
+}
+
+void UtilityProcessHost::OnChannelClosed() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost::OnChannelClosed", this);
+
+  RejectPromise();
+
+  if (!mShutdownRequested && mListener) {
+    // This is an unclean shutdown. Notify our listener that we're going away.
+    mListener->OnProcessUnexpectedShutdown(this);
+  }
+
+  DestroyProcess();
+
+  // Release the actor.
+  UtilityProcessParent::Destroy(std::move(mUtilityProcessParent));
+}
+
+void UtilityProcessHost::KillHard(const char* aReason) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost::KillHard", this);
+
+  ProcessHandle handle = GetChildProcessHandle();
+  if (!base::KillProcess(handle, base::PROCESS_END_KILLED_BY_USER)) {
+    NS_WARNING("failed to kill subprocess!");
+  }
+
+  SetAlreadyDead();
+}
+
+void UtilityProcessHost::DestroyProcess() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost::DestroyProcess", this);
+
+  RejectPromise();
+
+  // Any pending tasks will be cancelled from now on.
+  *mLiveToken = false;
+
+  NS_DispatchToMainThread(
+      NS_NewRunnableFunction("DestroyProcessRunnable", [this] { Destroy(); }));
+}
+
+void UtilityProcessHost::ResolvePromise() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost connected - resolving launch promise", this);
+
+  if (!mLaunchPromiseSettled) {
+    mLaunchPromise->Resolve(true, __func__);
+    mLaunchPromiseSettled = true;
+  }
+
+  mLaunchCompleted = true;
+}
+
+void UtilityProcessHost::RejectPromise() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOGD("[%p] UtilityProcessHost connection failed - rejecting launch promise",
+       this);
+
+  if (!mLaunchPromiseSettled) {
+    mLaunchPromise->Reject(NS_ERROR_FAILURE, __func__);
+    mLaunchPromiseSettled = true;
+  }
+
+  mLaunchCompleted = true;
+}
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+bool UtilityProcessHost::FillMacSandboxInfo(MacSandboxInfo& aInfo) {
+  GeckoChildProcessHost::FillMacSandboxInfo(aInfo);
+  if (!aInfo.shouldLog && PR_GetEnv("MOZ_SANDBOX_UTILITY_LOGGING")) {
+    aInfo.shouldLog = true;
+  }
+  return true;
+}
+
+/* static */
+MacSandboxType UtilityProcessHost::GetMacSandboxType() {
+  return MacSandboxType_Utility;
+}
+#endif
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityProcessHost.h b/ipc/glue/UtilityProcessHost.h
new file mode 100644
index 0000000000..6949470155
--- /dev/null
+++ b/ipc/glue/UtilityProcessHost.h
@@ -0,0 +1,158 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessHost_h_
+#define _include_ipc_glue_UtilityProcessHost_h_
+
+#include "mozilla/UniquePtr.h"
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/media/MediaUtils.h"
+#include "mozilla/ipc/ProcessUtils.h"
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxBroker.h"
+#endif
+
+namespace mozilla::ipc {
+
+class UtilityProcessParent;
+
+// UtilityProcessHost is the "parent process" container for a subprocess handle
+// and IPC connection. It owns the parent process IPDL actor, which in this
+// case, is a UtilityChild.
+//
+// UtilityProcessHosts are allocated and managed by UtilityProcessManager.
+class UtilityProcessHost final : public mozilla::ipc::GeckoChildProcessHost {
+  friend class UtilityProcessParent;
+
+ public:
+  class Listener {
+   protected:
+    virtual ~Listener() = default;
+
+   public:
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(UtilityProcessHost::Listener);
+
+    // The UtilityProcessHost has unexpectedly shutdown or had its connection
+    // severed. This is not called if an error occurs after calling
+    // Shutdown().
+    virtual void OnProcessUnexpectedShutdown(UtilityProcessHost* aHost) {}
+  };
+
+  explicit UtilityProcessHost(SandboxingKind aSandbox,
+                              RefPtr<Listener> listener);
+
+  // Launch the subprocess asynchronously. On failure, false is returned.
+  // Otherwise, true is returned. If succeeded, a follow-up call should be made
+  // to LaunchPromise() which will return a promise that will be resolved once
+  // the Utility process has launched and a channel has been established.
+  //
+  // @param aExtraOpts (StringVector)
+  //        Extra options to pass to the subprocess.
+  bool Launch(StringVector aExtraOpts);
+
+  // Return a promise that will be resolved once the process has completed its
+  // launch. The promise will be immediately resolved if the launch has already
+  // succeeded.
+  RefPtr<GenericNonExclusivePromise> LaunchPromise();
+
+  // Inform the process that it should clean up its resources and shut
+  // down. This initiates an asynchronous shutdown sequence. After this
+  // method returns, it is safe for the caller to forget its pointer to
+  // the UtilityProcessHost.
+  //
+  // After this returns, the attached Listener is no longer used.
+  void Shutdown();
+
+  // Return the actor for the top-level actor of the process. If the process
+  // has not connected yet, this returns null.
+  RefPtr<UtilityProcessParent> GetActor() const {
+    MOZ_ASSERT(NS_IsMainThread());
+    return mUtilityProcessParent;
+  }
+
+  bool IsConnected() const {
+    MOZ_ASSERT(NS_IsMainThread());
+    return bool(mUtilityProcessParent);
+  }
+
+  // Called on the IO thread.
+  void OnChannelConnected(base::ProcessId peer_pid) override;
+  void OnChannelError() override;
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  // Return the sandbox type to be used with this process type.
+  static MacSandboxType GetMacSandboxType();
+#endif
+
+ private:
+  ~UtilityProcessHost();
+
+  // Called on the main thread with true after a connection has been established
+  // or false if it failed (including if it failed before the timeout kicked in)
+  void InitAfterConnect(bool aSucceeded);
+
+  // Called on the main thread when the mUtilityProcessParent actor is shutting
+  // down.
+  void OnChannelClosed();
+
+  // Kill the remote process, triggering IPC shutdown.
+  void KillHard(const char* aReason);
+
+  void DestroyProcess();
+
+#if defined(XP_MACOSX) && defined(MOZ_SANDBOX)
+  static bool sLaunchWithMacSandbox;
+
+  // Sandbox the Utility process at launch for all instances
+  bool IsMacSandboxLaunchEnabled() override { return sLaunchWithMacSandbox; }
+
+  // Override so we can turn on Utility process-specific sandbox logging
+  bool FillMacSandboxInfo(MacSandboxInfo& aInfo) override;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(UtilityProcessHost);
+
+  RefPtr<Listener> mListener;
+
+  // All members below are only ever accessed on the main thread.
+  enum class LaunchPhase { Unlaunched, Waiting, Complete };
+  LaunchPhase mLaunchPhase = LaunchPhase::Unlaunched;
+
+  RefPtr<UtilityProcessParent> mUtilityProcessParent;
+
+  UniquePtr<ipc::SharedPreferenceSerializer> mPrefSerializer{};
+
+  bool mShutdownRequested = false;
+
+  void RejectPromise();
+  void ResolvePromise();
+
+  // Set to true on construction and to false just prior deletion.
+  // The UtilityProcessHost isn't refcounted; so we can capture this by value in
+  // lambdas along with a strong reference to mLiveToken and check if that value
+  // is true before accessing "this".
+  // While a reference to mLiveToken can be taken on any thread; its value can
+  // only be read or written on the main thread.
+  const RefPtr<media::Refcountable<bool>> mLiveToken;
+
+  RefPtr<GenericNonExclusivePromise::Private> mLaunchPromise{};
+  bool mLaunchPromiseSettled = false;
+  bool mLaunchPromiseLaunched = false;
+  // Will be set to true if the Utility process as successfully started.
+  bool mLaunchCompleted = false;
+
+#if defined(XP_LINUX) && defined(MOZ_SANDBOX)
+  UniquePtr<SandboxBroker> mSandboxBroker{};
+#endif
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // _include_ipc_glue_UtilityProcessHost_h_
diff --git a/ipc/glue/UtilityProcessImpl.cpp b/ipc/glue/UtilityProcessImpl.cpp
new file mode 100644
index 0000000000..0edfbfdc0b
--- /dev/null
+++ b/ipc/glue/UtilityProcessImpl.cpp
@@ -0,0 +1,127 @@
+/* -*- 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 "UtilityProcessImpl.h"
+
+#include "mozilla/ipc/IOThreadChild.h"
+#include "mozilla/GeckoArgs.h"
+
+#if defined(OS_WIN)
+#  include "nsExceptionHandler.h"
+#endif
+
+#if defined(OS_WIN) && defined(MOZ_SANDBOX)
+#  include "mozilla/sandboxTarget.h"
+#  include "WMF.h"
+#  include "WMFDecoderModule.h"
+#endif
+
+#if defined(XP_OPENBSD) && defined(MOZ_SANDBOX)
+#  include "mozilla/SandboxSettings.h"
+#endif
+
+namespace mozilla::ipc {
+
+UtilityProcessImpl::~UtilityProcessImpl() = default;
+
+#if defined(XP_WIN)
+/* static */
+void UtilityProcessImpl::LoadLibraryOrCrash(LPCWSTR aLib) {
+  // re-try a few times depending on the error we get ; inspired by both our
+  // results on content process allocations as well as msys2:
+  // https://github.com/git-for-windows/msys2-runtime/blob/b4fed42af089ab955286343835a97e287496b3f8/winsup/cygwin/autoload.cc#L323-L339
+
+  const int kMaxRetries = 10;
+  DWORD err;
+
+  for (int i = 0; i < kMaxRetries; i++) {
+    HMODULE module = ::LoadLibraryW(aLib);
+    if (module) {
+      return;
+    }
+
+    err = ::GetLastError();
+
+    if (err != ERROR_NOACCESS && err != ERROR_DLL_INIT_FAILED) {
+      break;
+    }
+
+    PR_Sleep(0);
+  }
+
+  switch (err) {
+    /* case ERROR_ACCESS_DENIED: */
+    /* case ERROR_BAD_EXE_FORMAT: */
+    /* case ERROR_SHARING_VIOLATION: */
+    case ERROR_MOD_NOT_FOUND:
+    case ERROR_COMMITMENT_LIMIT:
+      // We want to make it explicit in telemetry that this was in fact an
+      // OOM condition, even though we could not detect it on our own
+      CrashReporter::AnnotateOOMAllocationSize(1);
+      break;
+
+    default:
+      break;
+  }
+
+  MOZ_CRASH_UNSAFE_PRINTF("Unable to preload module: 0x%lx", err);
+}
+#endif  // defined(XP_WIN)
+
+bool UtilityProcessImpl::Init(int aArgc, char* aArgv[]) {
+  Maybe<uint64_t> sandboxingKind = geckoargs::sSandboxingKind.Get(aArgc, aArgv);
+  if (sandboxingKind.isNothing()) {
+    return false;
+  }
+
+  if (*sandboxingKind >= SandboxingKind::COUNT) {
+    return false;
+  }
+
+#if defined(MOZ_SANDBOX) && defined(OS_WIN)
+  // We delay load winmm.dll so that its dependencies don't interfere with COM
+  // initialization when win32k is locked down. We need to load it before we
+  // lower the sandbox in processes where the policy will prevent loading.
+  LoadLibraryOrCrash(L"winmm.dll");
+
+  if (*sandboxingKind == SandboxingKind::GENERIC_UTILITY) {
+    // Preload audio generic libraries required for ffmpeg only
+    UtilityAudioDecoderParent::GenericPreloadForSandbox();
+  }
+
+  if (*sandboxingKind == SandboxingKind::UTILITY_AUDIO_DECODING_WMF
+#  ifdef MOZ_WMF_MEDIA_ENGINE
+      || *sandboxingKind == SandboxingKind::MF_MEDIA_ENGINE_CDM
+#  endif
+  ) {
+    UtilityAudioDecoderParent::WMFPreloadForSandbox();
+  }
+
+  // Go for it
+  mozilla::SandboxTarget::Instance()->StartSandbox();
+#elif defined(__OpenBSD__) && defined(MOZ_SANDBOX)
+  if (*sandboxingKind != SandboxingKind::GENERIC_UTILITY) {
+    StartOpenBSDSandbox(GeckoProcessType_Utility,
+                        (SandboxingKind)*sandboxingKind);
+  }
+#endif
+
+  Maybe<const char*> parentBuildID =
+      geckoargs::sParentBuildID.Get(aArgc, aArgv);
+  if (parentBuildID.isNothing()) {
+    return false;
+  }
+
+  if (!ProcessChild::InitPrefs(aArgc, aArgv)) {
+    return false;
+  }
+
+  return mUtility->Init(TakeInitialEndpoint(), nsCString(*parentBuildID),
+                        *sandboxingKind);
+}
+
+void UtilityProcessImpl::CleanUp() { NS_ShutdownXPCOM(nullptr); }
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityProcessImpl.h b/ipc/glue/UtilityProcessImpl.h
new file mode 100644
index 0000000000..9b42cd5f74
--- /dev/null
+++ b/ipc/glue/UtilityProcessImpl.h
@@ -0,0 +1,43 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessImpl_h__
+#define _include_ipc_glue_UtilityProcessImpl_h__
+#include "mozilla/ipc/ProcessChild.h"
+
+#if defined(XP_WIN)
+#  include "mozilla/mscom/ProcessRuntime.h"
+#endif
+
+#include "mozilla/ipc/UtilityProcessChild.h"
+
+namespace mozilla::ipc {
+
+// This class owns the subprocess instance of a PUtilityProcess - which in this
+// case, is a UtilityProcessParent. It is instantiated as a singleton in
+// XRE_InitChildProcess.
+class UtilityProcessImpl final : public ipc::ProcessChild {
+ public:
+  using ipc::ProcessChild::ProcessChild;
+  ~UtilityProcessImpl();
+
+  bool Init(int aArgc, char* aArgv[]) override;
+  void CleanUp() override;
+
+#if defined(XP_WIN)
+  static void LoadLibraryOrCrash(LPCWSTR aLib);
+#endif  // defined(XP_WIN)
+
+ private:
+  RefPtr<UtilityProcessChild> mUtility = UtilityProcessChild::GetSingleton();
+
+#if defined(XP_WIN)
+  mozilla::mscom::ProcessRuntime mCOMRuntime;
+#endif
+};
+
+}  // namespace mozilla::ipc
+
+#endif  // _include_ipc_glue_UtilityProcessImpl_h__
diff --git a/ipc/glue/UtilityProcessManager.cpp b/ipc/glue/UtilityProcessManager.cpp
new file mode 100644
index 0000000000..59946cd3d3
--- /dev/null
+++ b/ipc/glue/UtilityProcessManager.cpp
@@ -0,0 +1,617 @@
+/* -*- 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 "UtilityProcessManager.h"
+
+#include "JSOracleParent.h"
+#include "mozilla/ipc/UtilityProcessHost.h"
+#include "mozilla/MemoryReportingProcess.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "mozilla/StaticPrefs_media.h"
+#include "mozilla/SyncRunnable.h"  // for LaunchUtilityProcess
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/ipc/UtilityAudioDecoderChild.h"
+#include "mozilla/ipc/UtilityAudioDecoderParent.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "mozilla/ipc/ProcessChild.h"
+#include "nsAppRunner.h"
+#include "nsContentUtils.h"
+
+#ifdef XP_WIN
+#  include "mozilla/dom/WindowsUtilsParent.h"
+#endif
+
+#include "mozilla/GeckoArgs.h"
+
+namespace mozilla::ipc {
+
+extern LazyLogModule gUtilityProcessLog;
+#define LOGD(...) MOZ_LOG(gUtilityProcessLog, LogLevel::Debug, (__VA_ARGS__))
+
+static StaticRefPtr<UtilityProcessManager> sSingleton;
+
+static bool sXPCOMShutdown = false;
+
+bool UtilityProcessManager::IsShutdown() const {
+  MOZ_ASSERT(NS_IsMainThread());
+  return sXPCOMShutdown || !sSingleton;
+}
+
+RefPtr<UtilityProcessManager> UtilityProcessManager::GetSingleton() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!sXPCOMShutdown && sSingleton == nullptr) {
+    sSingleton = new UtilityProcessManager();
+  }
+  return sSingleton;
+}
+
+RefPtr<UtilityProcessManager> UtilityProcessManager::GetIfExists() {
+  MOZ_ASSERT(NS_IsMainThread());
+  return sSingleton;
+}
+
+UtilityProcessManager::UtilityProcessManager() : mObserver(new Observer(this)) {
+  LOGD("[%p] UtilityProcessManager::UtilityProcessManager", this);
+
+  // Start listening for pref changes so we can
+  // forward them to the process once it is running.
+  nsContentUtils::RegisterShutdownObserver(mObserver);
+  Preferences::AddStrongObserver(mObserver, "");
+}
+
+UtilityProcessManager::~UtilityProcessManager() {
+  LOGD("[%p] UtilityProcessManager::~UtilityProcessManager", this);
+
+  // The Utility process should ALL have already been shut down.
+  MOZ_ASSERT(NoMoreProcesses());
+}
+
+NS_IMPL_ISUPPORTS(UtilityProcessManager::Observer, nsIObserver);
+
+UtilityProcessManager::Observer::Observer(
+    RefPtr<UtilityProcessManager> aManager)
+    : mManager(std::move(aManager)) {}
+
+NS_IMETHODIMP
+UtilityProcessManager::Observer::Observe(nsISupports* aSubject,
+                                         const char* aTopic,
+                                         const char16_t* aData) {
+  if (!strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID)) {
+    mManager->OnXPCOMShutdown();
+  } else if (!strcmp(aTopic, "nsPref:changed")) {
+    mManager->OnPreferenceChange(aData);
+  }
+  return NS_OK;
+}
+
+void UtilityProcessManager::OnXPCOMShutdown() {
+  LOGD("[%p] UtilityProcessManager::OnXPCOMShutdown", this);
+
+  MOZ_ASSERT(NS_IsMainThread());
+  sXPCOMShutdown = true;
+  nsContentUtils::UnregisterShutdownObserver(mObserver);
+  CleanShutdownAllProcesses();
+}
+
+void UtilityProcessManager::OnPreferenceChange(const char16_t* aData) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (NoMoreProcesses()) {
+    // Process hasn't been launched yet
+    return;
+  }
+  // We know prefs are ASCII here.
+  NS_LossyConvertUTF16toASCII strData(aData);
+
+  mozilla::dom::Pref pref(strData, /* isLocked */ false,
+                          /* isSanitized */ false, Nothing(), Nothing());
+  Preferences::GetPreference(&pref, GeckoProcessType_Utility,
+                             /* remoteType */ ""_ns);
+
+  for (auto& p : mProcesses) {
+    if (!p) {
+      continue;
+    }
+
+    if (p->mProcessParent) {
+      Unused << p->mProcessParent->SendPreferenceUpdate(pref);
+    } else if (IsProcessLaunching(p->mSandbox)) {
+      p->mQueuedPrefs.AppendElement(pref);
+    }
+  }
+}
+
+RefPtr<UtilityProcessManager::ProcessFields> UtilityProcessManager::GetProcess(
+    SandboxingKind aSandbox) {
+  if (!mProcesses[aSandbox]) {
+    return nullptr;
+  }
+
+  return mProcesses[aSandbox];
+}
+
+RefPtr<GenericNonExclusivePromise> UtilityProcessManager::LaunchProcess(
+    SandboxingKind aSandbox) {
+  LOGD("[%p] UtilityProcessManager::LaunchProcess SandboxingKind=%" PRIu64,
+       this, aSandbox);
+
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (IsShutdown()) {
+    NS_WARNING("Reject early LaunchProcess() for Shutdown");
+    return GenericNonExclusivePromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE,
+                                                       __func__);
+  }
+
+  RefPtr<ProcessFields> p = GetProcess(aSandbox);
+  if (p && p->mNumProcessAttempts) {
+    // We failed to start the Utility process earlier, abort now.
+    NS_WARNING("Reject LaunchProcess() for earlier mNumProcessAttempts");
+    return GenericNonExclusivePromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE,
+                                                       __func__);
+  }
+
+  if (p && p->mLaunchPromise && p->mProcess) {
+    return p->mLaunchPromise;
+  }
+
+  if (!p) {
+    p = new ProcessFields(aSandbox);
+    mProcesses[aSandbox] = p;
+  }
+
+  std::vector<std::string> extraArgs;
+  ProcessChild::AddPlatformBuildID(extraArgs);
+  geckoargs::sSandboxingKind.Put(aSandbox, extraArgs);
+
+  // The subprocess is launched asynchronously, so we
+  // wait for the promise to be resolved to acquire the IPDL actor.
+  p->mProcess = new UtilityProcessHost(aSandbox, this);
+  if (!p->mProcess->Launch(extraArgs)) {
+    p->mNumProcessAttempts++;
+    DestroyProcess(aSandbox);
+    NS_WARNING("Reject LaunchProcess() for mNumProcessAttempts++");
+    return GenericNonExclusivePromise::CreateAndReject(NS_ERROR_NOT_AVAILABLE,
+                                                       __func__);
+  }
+
+  RefPtr<UtilityProcessManager> self = this;
+  p->mLaunchPromise = p->mProcess->LaunchPromise()->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [self, p, aSandbox](bool) {
+        if (self->IsShutdown()) {
+          NS_WARNING(
+              "Reject LaunchProcess() after LaunchPromise() for Shutdown");
+          return GenericNonExclusivePromise::CreateAndReject(
+              NS_ERROR_NOT_AVAILABLE, __func__);
+        }
+
+        if (self->IsProcessDestroyed(aSandbox)) {
+          NS_WARNING(
+              "Reject LaunchProcess() after LaunchPromise() for destroyed "
+              "process");
+          return GenericNonExclusivePromise::CreateAndReject(
+              NS_ERROR_NOT_AVAILABLE, __func__);
+        }
+
+        p->mProcessParent = p->mProcess->GetActor();
+
+        // Flush any pref updates that happened during
+        // launch and weren't included in the blobs set
+        // up in LaunchUtilityProcess.
+        for (const mozilla::dom::Pref& pref : p->mQueuedPrefs) {
+          Unused << NS_WARN_IF(!p->mProcessParent->SendPreferenceUpdate(pref));
+        }
+        p->mQueuedPrefs.Clear();
+
+        CrashReporter::AnnotateCrashReport(
+            CrashReporter::Annotation::UtilityProcessStatus, "Running"_ns);
+
+        return GenericNonExclusivePromise::CreateAndResolve(true, __func__);
+      },
+      [self, p, aSandbox](nsresult aError) {
+        if (GetSingleton()) {
+          p->mNumProcessAttempts++;
+          self->DestroyProcess(aSandbox);
+        }
+        NS_WARNING("Reject LaunchProcess() for LaunchPromise() rejection");
+        return GenericNonExclusivePromise::CreateAndReject(aError, __func__);
+      });
+
+  return p->mLaunchPromise;
+}
+
+template <typename Actor>
+RefPtr<GenericNonExclusivePromise> UtilityProcessManager::StartUtility(
+    RefPtr<Actor> aActor, SandboxingKind aSandbox) {
+  LOGD(
+      "[%p] UtilityProcessManager::StartUtility actor=%p "
+      "SandboxingKind=%" PRIu64,
+      this, aActor.get(), aSandbox);
+
+  TimeStamp utilityStart = TimeStamp::Now();
+
+  if (!aActor) {
+    MOZ_ASSERT(false, "Actor singleton failure");
+    return GenericNonExclusivePromise::CreateAndReject(NS_ERROR_FAILURE,
+                                                       __func__);
+  }
+
+  if (aActor->CanSend()) {
+    // Actor has already been setup, so we:
+    //   - know the process has been launched
+    //   - the ipc actors are ready
+    PROFILER_MARKER_TEXT(
+        "UtilityProcessManager::StartUtility", IPC,
+        MarkerOptions(MarkerTiming::InstantNow()),
+        nsPrintfCString("SandboxingKind=%" PRIu64 " aActor->CanSend()",
+                        aSandbox));
+    return GenericNonExclusivePromise::CreateAndResolve(true, __func__);
+  }
+
+  RefPtr<UtilityProcessManager> self = this;
+  return LaunchProcess(aSandbox)->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [self, aActor, aSandbox, utilityStart]() {
+        RefPtr<UtilityProcessParent> utilityParent =
+            self->GetProcessParent(aSandbox);
+        if (!utilityParent) {
+          NS_WARNING("Missing parent in StartUtility");
+          return GenericNonExclusivePromise::CreateAndReject(NS_ERROR_FAILURE,
+                                                             __func__);
+        }
+
+        // It is possible if multiple processes concurrently request a utility
+        // actor that the previous CanSend() check returned false for both but
+        // that by the time we have started our process for real, one of them
+        // has already been able to establish the IPC connection and thus we
+        // would perform more than one Open() call.
+        //
+        // The tests within browser_utility_multipleAudio.js should be able to
+        // catch that behavior.
+        if (!aActor->CanSend()) {
+          nsresult rv = aActor->BindToUtilityProcess(utilityParent);
+          if (NS_FAILED(rv)) {
+            MOZ_ASSERT(false, "Protocol endpoints failure");
+            return GenericNonExclusivePromise::CreateAndReject(rv, __func__);
+          }
+
+          MOZ_DIAGNOSTIC_ASSERT(aActor->CanSend(), "IPC established for actor");
+          self->RegisterActor(utilityParent, aActor->GetActorName());
+        }
+
+        PROFILER_MARKER_TEXT(
+            "UtilityProcessManager::StartUtility", IPC,
+            MarkerOptions(MarkerTiming::IntervalUntilNowFrom(utilityStart)),
+            nsPrintfCString("SandboxingKind=%" PRIu64 " Resolve", aSandbox));
+        return GenericNonExclusivePromise::CreateAndResolve(true, __func__);
+      },
+      [self, aSandbox, utilityStart](nsresult aError) {
+        NS_WARNING("Reject StartUtility() for LaunchProcess() rejection");
+        if (!self->IsShutdown()) {
+          NS_WARNING("Reject StartUtility() when !IsShutdown()");
+        }
+        PROFILER_MARKER_TEXT(
+            "UtilityProcessManager::StartUtility", IPC,
+            MarkerOptions(MarkerTiming::IntervalUntilNowFrom(utilityStart)),
+            nsPrintfCString("SandboxingKind=%" PRIu64 " Reject", aSandbox));
+        return GenericNonExclusivePromise::CreateAndReject(aError, __func__);
+      });
+}
+
+RefPtr<UtilityProcessManager::StartRemoteDecodingUtilityPromise>
+UtilityProcessManager::StartProcessForRemoteMediaDecoding(
+    base::ProcessId aOtherProcess, dom::ContentParentId aChildId,
+    SandboxingKind aSandbox) {
+  // Not supported kinds.
+  if (aSandbox != SandboxingKind::GENERIC_UTILITY
+#ifdef MOZ_APPLEMEDIA
+      && aSandbox != SandboxingKind::UTILITY_AUDIO_DECODING_APPLE_MEDIA
+#endif
+#ifdef XP_WIN
+      && aSandbox != SandboxingKind::UTILITY_AUDIO_DECODING_WMF
+#endif
+#ifdef MOZ_WMF_MEDIA_ENGINE
+      && aSandbox != SandboxingKind::MF_MEDIA_ENGINE_CDM
+#endif
+  ) {
+    return StartRemoteDecodingUtilityPromise::CreateAndReject(NS_ERROR_FAILURE,
+                                                              __func__);
+  }
+  TimeStamp remoteDecodingStart = TimeStamp::Now();
+
+  RefPtr<UtilityProcessManager> self = this;
+  RefPtr<UtilityAudioDecoderChild> uadc =
+      UtilityAudioDecoderChild::GetSingleton(aSandbox);
+  MOZ_ASSERT(uadc, "Unable to get a singleton for UtilityAudioDecoderChild");
+  return StartUtility(uadc, aSandbox)
+      ->Then(
+          GetMainThreadSerialEventTarget(), __func__,
+          [self, uadc, aOtherProcess, aChildId, aSandbox,
+           remoteDecodingStart]() {
+            RefPtr<UtilityProcessParent> parent =
+                self->GetProcessParent(aSandbox);
+            if (!parent) {
+              NS_WARNING("UtilityAudioDecoderParent lost in the middle");
+              return StartRemoteDecodingUtilityPromise::CreateAndReject(
+                  NS_ERROR_FAILURE, __func__);
+            }
+
+            if (!uadc->CanSend()) {
+              NS_WARNING("UtilityAudioDecoderChild lost in the middle");
+              return StartRemoteDecodingUtilityPromise::CreateAndReject(
+                  NS_ERROR_FAILURE, __func__);
+            }
+
+            base::ProcessId process = parent->OtherPid();
+
+            Endpoint<PRemoteDecoderManagerChild> childPipe;
+            Endpoint<PRemoteDecoderManagerParent> parentPipe;
+            nsresult rv = PRemoteDecoderManager::CreateEndpoints(
+                process, aOtherProcess, &parentPipe, &childPipe);
+            if (NS_FAILED(rv)) {
+              MOZ_ASSERT(false, "Could not create content remote decoder");
+              return StartRemoteDecodingUtilityPromise::CreateAndReject(
+                  rv, __func__);
+            }
+
+            if (!uadc->SendNewContentRemoteDecoderManager(std::move(parentPipe),
+                                                          aChildId)) {
+              MOZ_ASSERT(false, "SendNewContentRemoteDecoderManager failure");
+              return StartRemoteDecodingUtilityPromise::CreateAndReject(
+                  NS_ERROR_FAILURE, __func__);
+            }
+
+#ifdef MOZ_WMF_MEDIA_ENGINE
+            if (aSandbox == SandboxingKind::MF_MEDIA_ENGINE_CDM &&
+                !uadc->CreateVideoBridge()) {
+              MOZ_ASSERT(false, "Failed to create video bridge");
+              return StartRemoteDecodingUtilityPromise::CreateAndReject(
+                  NS_ERROR_FAILURE, __func__);
+            }
+#endif
+            PROFILER_MARKER_TEXT(
+                "UtilityProcessManager::StartProcessForRemoteMediaDecoding",
+                MEDIA,
+                MarkerOptions(
+                    MarkerTiming::IntervalUntilNowFrom(remoteDecodingStart)),
+                "Resolve"_ns);
+            return StartRemoteDecodingUtilityPromise::CreateAndResolve(
+                std::move(childPipe), __func__);
+          },
+          [self, remoteDecodingStart](nsresult aError) {
+            NS_WARNING(
+                "Reject StartProcessForRemoteMediaDecoding() for "
+                "StartUtility() rejection");
+            PROFILER_MARKER_TEXT(
+                "UtilityProcessManager::StartProcessForRemoteMediaDecoding",
+                MEDIA,
+                MarkerOptions(
+                    MarkerTiming::IntervalUntilNowFrom(remoteDecodingStart)),
+                "Reject"_ns);
+            return StartRemoteDecodingUtilityPromise::CreateAndReject(aError,
+                                                                      __func__);
+          });
+}
+
+RefPtr<UtilityProcessManager::JSOraclePromise>
+UtilityProcessManager::StartJSOracle(dom::JSOracleParent* aParent) {
+  return StartUtility(RefPtr{aParent}, SandboxingKind::GENERIC_UTILITY);
+}
+
+#ifdef XP_WIN
+
+// Windows Utils
+
+RefPtr<UtilityProcessManager::WindowsUtilsPromise>
+UtilityProcessManager::GetWindowsUtilsPromise() {
+  TimeStamp windowsUtilsStart = TimeStamp::Now();
+  RefPtr<UtilityProcessManager> self = this;
+  if (!mWindowsUtils) {
+    mWindowsUtils = new dom::WindowsUtilsParent();
+  }
+
+  RefPtr<dom::WindowsUtilsParent> wup = mWindowsUtils;
+  MOZ_ASSERT(wup, "Unable to get a singleton for WindowsUtils");
+  return StartUtility(wup, SandboxingKind::WINDOWS_UTILS)
+      ->Then(
+          GetMainThreadSerialEventTarget(), __func__,
+          [self, wup, windowsUtilsStart]() {
+            if (!wup->CanSend()) {
+              MOZ_ASSERT(false, "WindowsUtilsParent can't send");
+              return WindowsUtilsPromise::CreateAndReject(NS_ERROR_FAILURE,
+                                                          __func__);
+            }
+            PROFILER_MARKER_TEXT(
+                "UtilityProcessManager::GetWindowsUtilsPromise", OTHER,
+                MarkerOptions(
+                    MarkerTiming::IntervalUntilNowFrom(windowsUtilsStart)),
+                "Resolve"_ns);
+            return WindowsUtilsPromise::CreateAndResolve(wup, __func__);
+          },
+          [self, windowsUtilsStart](nsresult aError) {
+            NS_WARNING("StartUtility rejected promise for PWindowsUtils");
+            PROFILER_MARKER_TEXT(
+                "UtilityProcessManager::GetWindowsUtilsPromise", OTHER,
+                MarkerOptions(
+                    MarkerTiming::IntervalUntilNowFrom(windowsUtilsStart)),
+                "Reject"_ns);
+            return WindowsUtilsPromise::CreateAndReject(aError, __func__);
+          });
+}
+
+void UtilityProcessManager::ReleaseWindowsUtils() { mWindowsUtils = nullptr; }
+
+#endif  // XP_WIN
+
+bool UtilityProcessManager::IsProcessLaunching(SandboxingKind aSandbox) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  RefPtr<ProcessFields> p = GetProcess(aSandbox);
+  if (!p) {
+    MOZ_CRASH("Cannot check process launching with no process");
+    return false;
+  }
+
+  return p->mProcess && !(p->mProcessParent);
+}
+
+bool UtilityProcessManager::IsProcessDestroyed(SandboxingKind aSandbox) {
+  MOZ_ASSERT(NS_IsMainThread());
+  RefPtr<ProcessFields> p = GetProcess(aSandbox);
+  if (!p) {
+    MOZ_CRASH("Cannot check process destroyed with no process");
+    return false;
+  }
+  return !p->mProcess && !p->mProcessParent;
+}
+
+void UtilityProcessManager::OnProcessUnexpectedShutdown(
+    UtilityProcessHost* aHost) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  for (auto& it : mProcesses) {
+    if (it && it->mProcess && it->mProcess == aHost) {
+      it->mNumUnexpectedCrashes++;
+      DestroyProcess(it->mSandbox);
+      return;
+    }
+  }
+
+  MOZ_CRASH(
+      "Called UtilityProcessManager::OnProcessUnexpectedShutdown with invalid "
+      "aHost");
+}
+
+void UtilityProcessManager::CleanShutdownAllProcesses() {
+  LOGD("[%p] UtilityProcessManager::CleanShutdownAllProcesses", this);
+
+  for (auto& it : mProcesses) {
+    if (it) {
+      DestroyProcess(it->mSandbox);
+    }
+  }
+}
+
+void UtilityProcessManager::CleanShutdown(SandboxingKind aSandbox) {
+  LOGD("[%p] UtilityProcessManager::CleanShutdown SandboxingKind=%" PRIu64,
+       this, aSandbox);
+
+  DestroyProcess(aSandbox);
+}
+
+uint16_t UtilityProcessManager::AliveProcesses() {
+  uint16_t alive = 0;
+  for (auto& p : mProcesses) {
+    if (p != nullptr) {
+      alive++;
+    }
+  }
+  return alive;
+}
+
+bool UtilityProcessManager::NoMoreProcesses() { return AliveProcesses() == 0; }
+
+void UtilityProcessManager::DestroyProcess(SandboxingKind aSandbox) {
+  LOGD("[%p] UtilityProcessManager::DestroyProcess SandboxingKind=%" PRIu64,
+       this, aSandbox);
+
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+
+  if (AliveProcesses() <= 1) {
+    if (mObserver) {
+      Preferences::RemoveObserver(mObserver, "");
+    }
+
+    mObserver = nullptr;
+  }
+
+  RefPtr<ProcessFields> p = GetProcess(aSandbox);
+  if (!p) {
+    return;
+  }
+
+  p->mQueuedPrefs.Clear();
+  p->mProcessParent = nullptr;
+
+  if (!p->mProcess) {
+    return;
+  }
+
+  p->mProcess->Shutdown();
+  p->mProcess = nullptr;
+
+  mProcesses[aSandbox] = nullptr;
+
+  CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::UtilityProcessStatus, "Destroyed"_ns);
+
+  if (NoMoreProcesses()) {
+    sSingleton = nullptr;
+  }
+}
+
+Maybe<base::ProcessId> UtilityProcessManager::ProcessPid(
+    SandboxingKind aSandbox) {
+  MOZ_ASSERT(NS_IsMainThread());
+  RefPtr<ProcessFields> p = GetProcess(aSandbox);
+  if (!p) {
+    return Nothing();
+  }
+  if (p->mProcessParent) {
+    return Some(p->mProcessParent->OtherPid());
+  }
+  return Nothing();
+}
+
+class UtilityMemoryReporter : public MemoryReportingProcess {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(UtilityMemoryReporter, override)
+
+  explicit UtilityMemoryReporter(UtilityProcessParent* aParent) {
+    mParent = aParent;
+  }
+
+  bool IsAlive() const override { return bool(GetParent()); }
+
+  bool SendRequestMemoryReport(
+      const uint32_t& aGeneration, const bool& aAnonymize,
+      const bool& aMinimizeMemoryUsage,
+      const Maybe<ipc::FileDescriptor>& aDMDFile) override {
+    RefPtr<UtilityProcessParent> parent = GetParent();
+    if (!parent) {
+      return false;
+    }
+
+    return parent->SendRequestMemoryReport(aGeneration, aAnonymize,
+                                           aMinimizeMemoryUsage, aDMDFile);
+  }
+
+  int32_t Pid() const override {
+    if (RefPtr<UtilityProcessParent> parent = GetParent()) {
+      return (int32_t)parent->OtherPid();
+    }
+    return 0;
+  }
+
+ private:
+  RefPtr<UtilityProcessParent> GetParent() const { return mParent; }
+
+  RefPtr<UtilityProcessParent> mParent = nullptr;
+
+ protected:
+  ~UtilityMemoryReporter() = default;
+};
+
+RefPtr<MemoryReportingProcess> UtilityProcessManager::GetProcessMemoryReporter(
+    UtilityProcessParent* parent) {
+  return new UtilityMemoryReporter(parent);
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityProcessManager.h b/ipc/glue/UtilityProcessManager.h
new file mode 100644
index 0000000000..2ad3f5041c
--- /dev/null
+++ b/ipc/glue/UtilityProcessManager.h
@@ -0,0 +1,234 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessManager_h_
+#define _include_ipc_glue_UtilityProcessManager_h_
+#include "mozilla/MozPromise.h"
+#include "mozilla/dom/ipc/IdType.h"
+#include "mozilla/ipc/UtilityProcessHost.h"
+#include "mozilla/EnumeratedArray.h"
+#include "mozilla/ProcInfo.h"
+#include "nsIObserver.h"
+#include "nsTArray.h"
+
+#include "mozilla/PRemoteDecoderManagerChild.h"
+
+namespace mozilla {
+
+class MemoryReportingProcess;
+
+namespace dom {
+class JSOracleParent;
+class WindowsUtilsParent;
+}  // namespace dom
+
+namespace ipc {
+
+class UtilityProcessParent;
+
+// The UtilityProcessManager is a singleton responsible for creating
+// Utility-bound objects that may live in another process. Currently, it
+// provides access to the Utility process via ContentParent.
+class UtilityProcessManager final : public UtilityProcessHost::Listener {
+  friend class UtilityProcessParent;
+
+ public:
+  using StartRemoteDecodingUtilityPromise =
+      MozPromise<Endpoint<PRemoteDecoderManagerChild>, nsresult, true>;
+  using JSOraclePromise = GenericNonExclusivePromise;
+
+  using WindowsUtilsPromise =
+      MozPromise<RefPtr<dom::WindowsUtilsParent>, nsresult, true>;
+
+  static void Initialize();
+  static void Shutdown();
+
+  static RefPtr<UtilityProcessManager> GetSingleton();
+
+  static RefPtr<UtilityProcessManager> GetIfExists();
+
+  // Launch a new Utility process asynchronously
+  RefPtr<GenericNonExclusivePromise> LaunchProcess(SandboxingKind aSandbox);
+
+  template <typename Actor>
+  RefPtr<GenericNonExclusivePromise> StartUtility(RefPtr<Actor> aActor,
+                                                  SandboxingKind aSandbox);
+
+  RefPtr<StartRemoteDecodingUtilityPromise> StartProcessForRemoteMediaDecoding(
+      base::ProcessId aOtherProcess, dom::ContentParentId aChildId,
+      SandboxingKind aSandbox);
+
+  RefPtr<JSOraclePromise> StartJSOracle(mozilla::dom::JSOracleParent* aParent);
+
+#ifdef XP_WIN
+  // Get the (possibly already resolved) promise for the Windows utility
+  // process actor.  Creates the process if it is not running.
+  RefPtr<WindowsUtilsPromise> GetWindowsUtilsPromise();
+  // Releases the WindowsUtils actor so that it can be destroyed.
+  // Subsequent attempts to use WindowsUtils will create a new process.
+  void ReleaseWindowsUtils();
+#endif
+
+  void OnProcessUnexpectedShutdown(UtilityProcessHost* aHost);
+
+  // Returns the platform pid for this utility sandbox process.
+  Maybe<base::ProcessId> ProcessPid(SandboxingKind aSandbox);
+
+  // Create a MemoryReportingProcess object for this utility process
+  RefPtr<MemoryReportingProcess> GetProcessMemoryReporter(
+      UtilityProcessParent* parent);
+
+  // Returns access to the PUtility protocol if a Utility process for that
+  // sandbox is present.
+  RefPtr<UtilityProcessParent> GetProcessParent(SandboxingKind aSandbox) {
+    RefPtr<ProcessFields> p = GetProcess(aSandbox);
+    if (!p) {
+      return nullptr;
+    }
+    return p->mProcessParent;
+  }
+
+  // Get a list of all valid utility process parent references
+  nsTArray<RefPtr<UtilityProcessParent>> GetAllProcessesProcessParent() {
+    nsTArray<RefPtr<UtilityProcessParent>> rv;
+    for (auto& p : mProcesses) {
+      if (p && p->mProcessParent) {
+        rv.AppendElement(p->mProcessParent);
+      }
+    }
+    return rv;
+  }
+
+  // Returns the Utility Process for that sandbox
+  UtilityProcessHost* Process(SandboxingKind aSandbox) {
+    RefPtr<ProcessFields> p = GetProcess(aSandbox);
+    if (!p) {
+      return nullptr;
+    }
+    return p->mProcess;
+  }
+
+  void RegisterActor(const RefPtr<UtilityProcessParent>& aParent,
+                     UtilityActorName aActorName) {
+    for (auto& p : mProcesses) {
+      if (p && p->mProcessParent && p->mProcessParent == aParent) {
+        p->mActors.AppendElement(aActorName);
+        return;
+      }
+    }
+  }
+
+  Span<const UtilityActorName> GetActors(
+      const RefPtr<UtilityProcessParent>& aParent) {
+    for (auto& p : mProcesses) {
+      if (p && p->mProcessParent && p->mProcessParent == aParent) {
+        return p->mActors;
+      }
+    }
+    return {};
+  }
+
+  Span<const UtilityActorName> GetActors(GeckoChildProcessHost* aHost) {
+    for (auto& p : mProcesses) {
+      if (p && p->mProcess == aHost) {
+        return p->mActors;
+      }
+    }
+    return {};
+  }
+
+  Span<const UtilityActorName> GetActors(SandboxingKind aSbKind) {
+    auto proc = GetProcess(aSbKind);
+    if (!proc) {
+      return {};
+    }
+    return proc->mActors;
+  }
+
+  // Shutdown the Utility process for that sandbox.
+  void CleanShutdown(SandboxingKind aSandbox);
+
+  // Shutdown all utility processes
+  void CleanShutdownAllProcesses();
+
+  uint16_t AliveProcesses();
+
+ private:
+  ~UtilityProcessManager();
+
+  bool IsProcessLaunching(SandboxingKind aSandbox);
+  bool IsProcessDestroyed(SandboxingKind aSandbox);
+
+  // Called from our xpcom-shutdown observer.
+  void OnXPCOMShutdown();
+  void OnPreferenceChange(const char16_t* aData);
+
+  UtilityProcessManager();
+
+  void DestroyProcess(SandboxingKind aSandbox);
+
+  bool IsShutdown() const;
+
+  class Observer final : public nsIObserver {
+   public:
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSIOBSERVER
+    explicit Observer(RefPtr<UtilityProcessManager> aManager);
+
+   protected:
+    ~Observer() = default;
+
+    RefPtr<UtilityProcessManager> mManager;
+  };
+  friend class Observer;
+
+  RefPtr<Observer> mObserver;
+
+  class ProcessFields final {
+   public:
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ProcessFields);
+
+    explicit ProcessFields(SandboxingKind aSandbox) : mSandbox(aSandbox){};
+
+    // Promise will be resolved when this Utility process has been fully started
+    // and configured. Only accessed on the main thread.
+    RefPtr<GenericNonExclusivePromise> mLaunchPromise;
+
+    uint32_t mNumProcessAttempts = 0;
+    uint32_t mNumUnexpectedCrashes = 0;
+
+    // Fields that are associated with the current Utility process.
+    UtilityProcessHost* mProcess = nullptr;
+    RefPtr<UtilityProcessParent> mProcessParent = nullptr;
+
+    // Collects any pref changes that occur during process launch (after
+    // the initial map is passed in command-line arguments) to be sent
+    // when the process can receive IPC messages.
+    nsTArray<dom::Pref> mQueuedPrefs;
+
+    nsTArray<UtilityActorName> mActors;
+
+    SandboxingKind mSandbox = SandboxingKind::COUNT;
+
+   protected:
+    ~ProcessFields() = default;
+  };
+
+  EnumeratedArray<SandboxingKind, SandboxingKind::COUNT, RefPtr<ProcessFields>>
+      mProcesses;
+
+  RefPtr<ProcessFields> GetProcess(SandboxingKind);
+  bool NoMoreProcesses();
+
+#ifdef XP_WIN
+  RefPtr<dom::WindowsUtilsParent> mWindowsUtils;
+#endif  // XP_WIN
+};
+
+}  // namespace ipc
+
+}  // namespace mozilla
+
+#endif  // _include_ipc_glue_UtilityProcessManager_h_
diff --git a/ipc/glue/UtilityProcessParent.cpp b/ipc/glue/UtilityProcessParent.cpp
new file mode 100644
index 0000000000..4a98b5deb1
--- /dev/null
+++ b/ipc/glue/UtilityProcessParent.cpp
@@ -0,0 +1,201 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+
+#if defined(XP_WIN)
+#  include <dwrite.h>
+#  include <process.h>
+#  include "mozilla/WinDllServices.h"
+#endif
+
+#include "mozilla/ipc/ProcessChild.h"
+#include "mozilla/FOGIPC.h"
+
+#include "mozilla/Telemetry.h"
+#include "mozilla/TelemetryIPC.h"
+
+#include "nsHashPropertyBag.h"
+#include "mozilla/Services.h"
+#include "nsIObserverService.h"
+
+namespace mozilla::ipc {
+
+UtilityProcessParent::UtilityProcessParent(UtilityProcessHost* aHost)
+    : mHost(aHost) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mHost);
+}
+
+UtilityProcessParent::~UtilityProcessParent() = default;
+
+bool UtilityProcessParent::SendRequestMemoryReport(
+    const uint32_t& aGeneration, const bool& aAnonymize,
+    const bool& aMinimizeMemoryUsage, const Maybe<FileDescriptor>& aDMDFile) {
+  mMemoryReportRequest = MakeUnique<MemoryReportRequestHost>(aGeneration);
+
+  PUtilityProcessParent::SendRequestMemoryReport(
+      aGeneration, aAnonymize, aMinimizeMemoryUsage, aDMDFile,
+      [self = RefPtr{this}](const uint32_t& aGeneration2) {
+        if (self->mMemoryReportRequest) {
+          self->mMemoryReportRequest->Finish(aGeneration2);
+          self->mMemoryReportRequest = nullptr;
+        }
+      },
+      [self = RefPtr{this}](mozilla::ipc::ResponseRejectReason) {
+        self->mMemoryReportRequest = nullptr;
+      });
+
+  return true;
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvAddMemoryReport(
+    const MemoryReport& aReport) {
+  if (mMemoryReportRequest) {
+    mMemoryReportRequest->RecvReport(aReport);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvFOGData(ByteBuf&& aBuf) {
+  glean::FOGData(std::move(aBuf));
+  return IPC_OK();
+}
+
+#if defined(XP_WIN)
+mozilla::ipc::IPCResult UtilityProcessParent::RecvGetModulesTrust(
+    ModulePaths&& aModPaths, bool aRunAtNormalPriority,
+    GetModulesTrustResolver&& aResolver) {
+  RefPtr<DllServices> dllSvc(DllServices::Get());
+  dllSvc->GetModulesTrust(std::move(aModPaths), aRunAtNormalPriority)
+      ->Then(
+          GetMainThreadSerialEventTarget(), __func__,
+          [aResolver](ModulesMapResult&& aResult) {
+            aResolver(Some(ModulesMapResult(std::move(aResult))));
+          },
+          [aResolver](nsresult aRv) { aResolver(Nothing()); });
+  return IPC_OK();
+}
+#endif  // defined(XP_WIN)
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvAccumulateChildHistograms(
+    nsTArray<HistogramAccumulation>&& aAccumulations) {
+  TelemetryIPC::AccumulateChildHistograms(Telemetry::ProcessID::Utility,
+                                          aAccumulations);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult
+UtilityProcessParent::RecvAccumulateChildKeyedHistograms(
+    nsTArray<KeyedHistogramAccumulation>&& aAccumulations) {
+  TelemetryIPC::AccumulateChildKeyedHistograms(Telemetry::ProcessID::Utility,
+                                               aAccumulations);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvUpdateChildScalars(
+    nsTArray<ScalarAction>&& aScalarActions) {
+  TelemetryIPC::UpdateChildScalars(Telemetry::ProcessID::Utility,
+                                   aScalarActions);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvUpdateChildKeyedScalars(
+    nsTArray<KeyedScalarAction>&& aScalarActions) {
+  TelemetryIPC::UpdateChildKeyedScalars(Telemetry::ProcessID::Utility,
+                                        aScalarActions);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvRecordChildEvents(
+    nsTArray<mozilla::Telemetry::ChildEventData>&& aEvents) {
+  TelemetryIPC::RecordChildEvents(Telemetry::ProcessID::Utility, aEvents);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvRecordDiscardedData(
+    const mozilla::Telemetry::DiscardedData& aDiscardedData) {
+  TelemetryIPC::RecordDiscardedData(Telemetry::ProcessID::Utility,
+                                    aDiscardedData);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult UtilityProcessParent::RecvInitCompleted() {
+  MOZ_ASSERT(mHost);
+  mHost->ResolvePromise();
+  return IPC_OK();
+}
+
+void UtilityProcessParent::ActorDestroy(ActorDestroyReason aWhy) {
+  RefPtr<nsHashPropertyBag> props = new nsHashPropertyBag();
+
+  if (aWhy == AbnormalShutdown) {
+    nsAutoString dumpID;
+
+    if (mCrashReporter) {
+#if defined(MOZ_SANDBOX)
+      RefPtr<mozilla::ipc::UtilityProcessManager> upm =
+          mozilla::ipc::UtilityProcessManager::GetSingleton();
+      if (upm) {
+        Span<const UtilityActorName> actors = upm->GetActors(this);
+        nsAutoCString actorsName;
+        if (!actors.IsEmpty()) {
+          actorsName += GetUtilityActorName(actors.First<1>()[0]);
+          for (const auto& actor : actors.From(1)) {
+            actorsName += ", "_ns + GetUtilityActorName(actor);
+          }
+        }
+        mCrashReporter->AddAnnotation(
+            CrashReporter::Annotation::UtilityActorsName, actorsName);
+      }
+#endif
+    }
+
+    GenerateCrashReport(OtherPid(), &dumpID);
+
+    // It's okay for dumpID to be empty if there was no minidump generated
+    // tests like ipc/glue/test/browser/browser_utility_crashReporter.js are
+    // there to verify this
+    if (!dumpID.IsEmpty()) {
+      props->SetPropertyAsAString(u"dumpID"_ns, dumpID);
+    }
+  }
+
+  nsAutoString pid;
+  pid.AppendInt(static_cast<uint64_t>(OtherPid()));
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (obs) {
+    obs->NotifyObservers((nsIPropertyBag2*)props, "ipc:utility-shutdown",
+                         pid.get());
+  } else {
+    NS_WARNING("Could not get a nsIObserverService, ipc:utility-shutdown skip");
+  }
+
+  mHost->OnChannelClosed();
+}
+
+// To ensure that IPDL is finished before UtilityParent gets deleted.
+class DeferredDeleteUtilityProcessParent : public Runnable {
+ public:
+  explicit DeferredDeleteUtilityProcessParent(
+      RefPtr<UtilityProcessParent> aParent)
+      : Runnable("ipc::glue::DeferredDeleteUtilityProcessParent"),
+        mParent(std::move(aParent)) {}
+
+  NS_IMETHODIMP Run() override { return NS_OK; }
+
+ private:
+  RefPtr<UtilityProcessParent> mParent;
+};
+
+/* static */
+void UtilityProcessParent::Destroy(RefPtr<UtilityProcessParent> aParent) {
+  NS_DispatchToMainThread(
+      new DeferredDeleteUtilityProcessParent(std::move(aParent)));
+}
+
+}  // namespace mozilla::ipc
diff --git a/ipc/glue/UtilityProcessParent.h b/ipc/glue/UtilityProcessParent.h
new file mode 100644
index 0000000000..6ff907583f
--- /dev/null
+++ b/ipc/glue/UtilityProcessParent.h
@@ -0,0 +1,77 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessParent_h__
+#define _include_ipc_glue_UtilityProcessParent_h__
+#include "mozilla/ipc/PUtilityProcessParent.h"
+#include "mozilla/ipc/CrashReporterHelper.h"
+#include "mozilla/ipc/UtilityProcessHost.h"
+#include "mozilla/dom/MemoryReportRequest.h"
+
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+
+namespace ipc {
+
+class UtilityProcessHost;
+
+class UtilityProcessParent final
+    : public PUtilityProcessParent,
+      public ipc::CrashReporterHelper<GeckoProcessType_Utility> {
+  typedef mozilla::dom::MemoryReportRequestHost MemoryReportRequestHost;
+
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(UtilityProcessParent, override);
+  friend class UtilityProcessHost;
+
+  explicit UtilityProcessParent(UtilityProcessHost* aHost);
+
+  mozilla::ipc::IPCResult RecvAddMemoryReport(const MemoryReport& aReport);
+
+  bool SendRequestMemoryReport(const uint32_t& aGeneration,
+                               const bool& aAnonymize,
+                               const bool& aMinimizeMemoryUsage,
+                               const Maybe<ipc::FileDescriptor>& aDMDFile);
+
+  mozilla::ipc::IPCResult RecvFOGData(ByteBuf&& aBuf);
+
+#if defined(XP_WIN)
+  mozilla::ipc::IPCResult RecvGetModulesTrust(
+      ModulePaths&& aModPaths, bool aRunAtNormalPriority,
+      GetModulesTrustResolver&& aResolver);
+#endif  // defined(XP_WIN)
+
+  mozilla::ipc::IPCResult RecvAccumulateChildHistograms(
+      nsTArray<HistogramAccumulation>&& aAccumulations);
+  mozilla::ipc::IPCResult RecvAccumulateChildKeyedHistograms(
+      nsTArray<KeyedHistogramAccumulation>&& aAccumulations);
+  mozilla::ipc::IPCResult RecvUpdateChildScalars(
+      nsTArray<ScalarAction>&& aScalarActions);
+  mozilla::ipc::IPCResult RecvUpdateChildKeyedScalars(
+      nsTArray<KeyedScalarAction>&& aScalarActions);
+  mozilla::ipc::IPCResult RecvRecordChildEvents(
+      nsTArray<ChildEventData>&& events);
+  mozilla::ipc::IPCResult RecvRecordDiscardedData(
+      const DiscardedData& aDiscardedData);
+
+  mozilla::ipc::IPCResult RecvInitCompleted();
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+ private:
+  UtilityProcessHost* mHost;
+  UniquePtr<MemoryReportRequestHost> mMemoryReportRequest{};
+
+  ~UtilityProcessParent();
+
+  static void Destroy(RefPtr<UtilityProcessParent> aParent);
+};
+
+}  // namespace ipc
+
+}  // namespace mozilla
+
+#endif  // _include_ipc_glue_UtilityProcessParent_h__
diff --git a/ipc/glue/UtilityProcessSandboxing.h b/ipc/glue/UtilityProcessSandboxing.h
new file mode 100644
index 0000000000..7aac77e0e9
--- /dev/null
+++ b/ipc/glue/UtilityProcessSandboxing.h
@@ -0,0 +1,42 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessSandboxing_h_
+#define _include_ipc_glue_UtilityProcessSandboxing_h_
+
+#include <stdint.h>
+
+namespace mozilla {
+
+namespace ipc {
+
+// When adding a new value, the checks within UtilityProcessImpl::Init() needs
+// to be updated as well.
+enum SandboxingKind : uint64_t {
+
+  GENERIC_UTILITY,
+
+#ifdef MOZ_APPLEMEDIA
+  UTILITY_AUDIO_DECODING_APPLE_MEDIA,
+#endif
+#ifdef XP_WIN
+  UTILITY_AUDIO_DECODING_WMF,
+#endif
+#ifdef MOZ_WMF_MEDIA_ENGINE
+  MF_MEDIA_ENGINE_CDM,
+#endif
+#ifdef XP_WIN
+  WINDOWS_UTILS,
+#endif
+
+  COUNT,
+
+};
+
+}  // namespace ipc
+
+}  // namespace mozilla
+
+#endif  // _include_ipc_glue_UtilityProcessSandboxing_h_
diff --git a/ipc/glue/WindowsMessageLoop.cpp b/ipc/glue/WindowsMessageLoop.cpp
new file mode 100644
index 0000000000..51bb7c8531
--- /dev/null
+++ b/ipc/glue/WindowsMessageLoop.cpp
@@ -0,0 +1,1205 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/DebugOnly.h"
+
+#include "WindowsMessageLoop.h"
+#include "Neutering.h"
+#include "MessageChannel.h"
+
+#include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "WinUtils.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/dom/JSExecutionManager.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/PaintTracker.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WindowsProcessMitigations.h"
+
+using namespace mozilla;
+using namespace mozilla::ipc;
+using namespace mozilla::ipc::windows;
+
+/**
+ * The Windows-only code below exists to solve a general problem with deadlocks
+ * that we experience when sending synchronous IPC messages to processes that
+ * contain native windows (i.e. HWNDs). Windows (the OS) sends synchronous
+ * messages between parent and child HWNDs in multiple circumstances (e.g.
+ * WM_PARENTNOTIFY, WM_NCACTIVATE, etc.), even when those HWNDs are controlled
+ * by different threads or different processes. Thus we can very easily end up
+ * in a deadlock by a call stack like the following:
+ *
+ * Process A:
+ *   - CreateWindow(...) creates a "parent" HWND.
+ *   - SendCreateChildWidget(HWND) is a sync IPC message that sends the "parent"
+ *         HWND over to Process B. Process A blocks until a response is received
+ *         from Process B.
+ *
+ * Process B:
+ *   - RecvCreateWidget(HWND) gets the "parent" HWND from Process A.
+ *   - CreateWindow(..., HWND) creates a "child" HWND with the parent from
+ *         process A.
+ *   - Windows (the OS) generates a WM_PARENTNOTIFY message that is sent
+ *         synchronously to Process A. Process B blocks until a response is
+ *         received from Process A. Process A, however, is blocked and cannot
+ *         process the message. Both processes are deadlocked.
+ *
+ * The example above has a few different workarounds (e.g. setting the
+ * WS_EX_NOPARENTNOTIFY style on the child window) but the general problem is
+ * persists. Once two HWNDs are parented we must not block their owning
+ * threads when manipulating either HWND.
+ *
+ * Windows requires any application that hosts native HWNDs to always process
+ * messages or risk deadlock. Given our architecture the only way to meet
+ * Windows' requirement and allow for synchronous IPC messages is to pump a
+ * miniature message loop during a sync IPC call. We avoid processing any
+ * queued messages during the loop (with one exception, see below), but
+ * "nonqueued" messages (see
+ * http://msdn.microsoft.com/en-us/library/ms644927(VS.85).aspx under the
+ * section "Nonqueued messages") cannot be avoided. Those messages are trapped
+ * in a special window procedure where we can either ignore the message or
+ * process it in some fashion.
+ *
+ * Queued and "non-queued" messages will be processed during Interrupt calls if
+ * modal UI related api calls block an Interrupt in-call in the child. To
+ * prevent windows from freezing, and to allow concurrent processing of critical
+ * events (such as painting), we spin a native event dispatch loop while
+ * these in-calls are blocked.
+ */
+
+#if defined(ACCESSIBILITY)
+// pulled from accessibility's win utils
+extern const wchar_t* kPropNameTabContent;
+#endif
+
+// widget related message id constants we need to defer, see nsAppShell.
+extern UINT sAppShellGeckoMsgId;
+
+namespace {
+
+const wchar_t kOldWndProcProp[] = L"MozillaIPCOldWndProc";
+const wchar_t k3rdPartyWindowProp[] = L"Mozilla3rdPartyWindow";
+
+// This isn't defined before Windows XP.
+enum { WM_XP_THEMECHANGED = 0x031A };
+
+nsTArray<HWND>* gNeuteredWindows = nullptr;
+
+typedef nsTArray<UniquePtr<DeferredMessage>> DeferredMessageArray;
+DeferredMessageArray* gDeferredMessages = nullptr;
+
+HHOOK gDeferredGetMsgHook = nullptr;
+HHOOK gDeferredCallWndProcHook = nullptr;
+
+DWORD gUIThreadId = 0;
+HWND gCOMWindow = 0;
+// Once initialized, gWinEventHook is never unhooked. We save the handle so
+// that we can check whether or not the hook is initialized.
+HWINEVENTHOOK gWinEventHook = nullptr;
+const wchar_t kCOMWindowClassName[] = L"OleMainThreadWndClass";
+
+// WM_GETOBJECT id pulled from uia headers
+#define MOZOBJID_UIAROOT -25
+
+HWND FindCOMWindow() {
+  MOZ_ASSERT(gUIThreadId);
+
+  HWND last = 0;
+  while (
+      (last = FindWindowExW(HWND_MESSAGE, last, kCOMWindowClassName, NULL))) {
+    if (GetWindowThreadProcessId(last, NULL) == gUIThreadId) {
+      return last;
+    }
+  }
+
+  return (HWND)0;
+}
+
+void CALLBACK WinEventHook(HWINEVENTHOOK aWinEventHook, DWORD aEvent,
+                           HWND aHwnd, LONG aIdObject, LONG aIdChild,
+                           DWORD aEventThread, DWORD aMsEventTime) {
+  MOZ_ASSERT(aWinEventHook == gWinEventHook);
+  MOZ_ASSERT(gUIThreadId == aEventThread);
+  switch (aEvent) {
+    case EVENT_OBJECT_CREATE: {
+      if (aIdObject != OBJID_WINDOW || aIdChild != CHILDID_SELF) {
+        // Not an event we're interested in
+        return;
+      }
+      wchar_t classBuf[256] = {0};
+      int result = ::GetClassNameW(aHwnd, classBuf, MOZ_ARRAY_LENGTH(classBuf));
+      if (result != (MOZ_ARRAY_LENGTH(kCOMWindowClassName) - 1) ||
+          wcsncmp(kCOMWindowClassName, classBuf, result)) {
+        // Not a class we're interested in
+        return;
+      }
+      MOZ_ASSERT(FindCOMWindow() == aHwnd);
+      gCOMWindow = aHwnd;
+      break;
+    }
+    case EVENT_OBJECT_DESTROY: {
+      if (aHwnd == gCOMWindow && aIdObject == OBJID_WINDOW) {
+        MOZ_ASSERT(aIdChild == CHILDID_SELF);
+        gCOMWindow = 0;
+      }
+      break;
+    }
+    default: {
+      return;
+    }
+  }
+}
+
+LRESULT CALLBACK DeferredMessageHook(int nCode, WPARAM wParam, LPARAM lParam) {
+  // XXX This function is called for *both* the WH_CALLWNDPROC hook and the
+  //     WH_GETMESSAGE hook, but they have different parameters. We don't
+  //     use any of them except nCode which has the same meaning.
+
+  // Only run deferred messages if all of these conditions are met:
+  //   1. The |nCode| indicates that this hook should do something.
+  //   2. We have deferred messages to run.
+  //   3. We're not being called from the PeekMessage within the WaitFor*Notify
+  //      function (indicated with MessageChannel::IsPumpingMessages). We really
+  //      only want to run after returning to the main event loop.
+  if (nCode >= 0 && gDeferredMessages && !MessageChannel::IsPumpingMessages()) {
+    NS_ASSERTION(gDeferredGetMsgHook && gDeferredCallWndProcHook,
+                 "These hooks must be set if we're being called!");
+    NS_ASSERTION(gDeferredMessages->Length(), "No deferred messages?!");
+
+    // Unset hooks first, in case we reenter below.
+    UnhookWindowsHookEx(gDeferredGetMsgHook);
+    UnhookWindowsHookEx(gDeferredCallWndProcHook);
+    gDeferredGetMsgHook = 0;
+    gDeferredCallWndProcHook = 0;
+
+    // Unset the global and make sure we delete it when we're done here.
+    auto messages = WrapUnique(gDeferredMessages);
+    gDeferredMessages = nullptr;
+
+    // Run all the deferred messages in order.
+    uint32_t count = messages->Length();
+    for (uint32_t index = 0; index < count; index++) {
+      messages->ElementAt(index)->Run();
+    }
+  }
+
+  // Always call the next hook.
+  return CallNextHookEx(nullptr, nCode, wParam, lParam);
+}
+
+void ScheduleDeferredMessageRun() {
+  if (gDeferredMessages && !(gDeferredGetMsgHook && gDeferredCallWndProcHook)) {
+    NS_ASSERTION(gDeferredMessages->Length(), "No deferred messages?!");
+
+    gDeferredGetMsgHook = ::SetWindowsHookEx(WH_GETMESSAGE, DeferredMessageHook,
+                                             nullptr, gUIThreadId);
+    gDeferredCallWndProcHook = ::SetWindowsHookEx(
+        WH_CALLWNDPROC, DeferredMessageHook, nullptr, gUIThreadId);
+    NS_ASSERTION(gDeferredGetMsgHook && gDeferredCallWndProcHook,
+                 "Failed to set hooks!");
+  }
+}
+
+static void DumpNeuteredMessage(HWND hwnd, UINT uMsg) {
+#ifdef DEBUG
+  nsAutoCString log("Received \"nonqueued\" ");
+  // classify messages
+  if (uMsg < WM_USER) {
+    const char* msgText = mozilla::widget::WinUtils::WinEventToEventName(uMsg);
+    if (msgText) {
+      log.AppendPrintf("ui message \"%s\"", msgText);
+    } else {
+      log.AppendPrintf("ui message (0x%X)", uMsg);
+    }
+  } else if (uMsg >= WM_USER && uMsg < WM_APP) {
+    log.AppendPrintf("WM_USER message (0x%X)", uMsg);
+  } else if (uMsg >= WM_APP && uMsg < 0xC000) {
+    log.AppendPrintf("WM_APP message (0x%X)", uMsg);
+  } else if (uMsg >= 0xC000 && uMsg < 0x10000) {
+    log.AppendPrintf("registered windows message (0x%X)", uMsg);
+  } else {
+    log.AppendPrintf("system message (0x%X)", uMsg);
+  }
+
+  log.AppendLiteral(" during a synchronous IPC message for window ");
+  log.AppendPrintf("0x%p", hwnd);
+
+  wchar_t className[256] = {0};
+  if (GetClassNameW(hwnd, className, sizeof(className) - 1) > 0) {
+    log.AppendLiteral(" (\"");
+    log.Append(NS_ConvertUTF16toUTF8((char16_t*)className));
+    log.AppendLiteral("\")");
+  }
+
+  log.AppendLiteral(
+      ", sending it to DefWindowProc instead of the normal "
+      "window procedure.");
+  NS_ERROR(log.get());
+#endif
+}
+
+LRESULT
+ProcessOrDeferMessage(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
+  UniquePtr<DeferredMessage> deferred;
+
+  // Most messages ask for 0 to be returned if the message is processed.
+  LRESULT res = 0;
+
+  switch (uMsg) {
+    // Messages that can be deferred as-is. These must not contain pointers in
+    // their wParam or lParam arguments!
+    case WM_ACTIVATE:
+    case WM_ACTIVATEAPP:
+    case WM_CANCELMODE:
+    case WM_CAPTURECHANGED:
+    case WM_CHILDACTIVATE:
+    case WM_DESTROY:
+    case WM_ENABLE:
+    case WM_IME_NOTIFY:
+    case WM_IME_SETCONTEXT:
+    case WM_KILLFOCUS:
+    case WM_MOUSEWHEEL:
+    case WM_NCDESTROY:
+    case WM_PARENTNOTIFY:
+    case WM_SETFOCUS:
+    case WM_SYSCOMMAND:
+    case WM_DISPLAYCHANGE:
+    case WM_SHOWWINDOW:  // Intentional fall-through.
+    case WM_XP_THEMECHANGED: {
+      deferred = MakeUnique<DeferredSendMessage>(hwnd, uMsg, wParam, lParam);
+      break;
+    }
+
+    case WM_DEVICECHANGE:
+    case WM_POWERBROADCAST:
+    case WM_NCACTIVATE:  // Intentional fall-through.
+    case WM_SETCURSOR: {
+      // Friggin unconventional return value...
+      res = TRUE;
+      deferred = MakeUnique<DeferredSendMessage>(hwnd, uMsg, wParam, lParam);
+      break;
+    }
+
+    case WM_MOUSEACTIVATE: {
+      res = MA_NOACTIVATE;
+      deferred = MakeUnique<DeferredSendMessage>(hwnd, uMsg, wParam, lParam);
+      break;
+    }
+
+    // These messages need to use the RedrawWindow function to generate the
+    // right kind of message. We can't simply fake them as the MSDN docs say
+    // explicitly that paint messages should not be sent by an application.
+    case WM_ERASEBKGND: {
+      UINT flags = RDW_INVALIDATE | RDW_ERASE | RDW_NOINTERNALPAINT |
+                   RDW_NOFRAME | RDW_NOCHILDREN | RDW_ERASENOW;
+      deferred = MakeUnique<DeferredRedrawMessage>(hwnd, flags);
+      break;
+    }
+
+    // This message will generate a WM_PAINT message if there are invalid
+    // areas.
+    case WM_PAINT: {
+      deferred = MakeUnique<DeferredUpdateMessage>(hwnd);
+      break;
+    }
+
+    // This message holds a string in its lParam that we must copy.
+    case WM_SETTINGCHANGE: {
+      deferred =
+          MakeUnique<DeferredSettingChangeMessage>(hwnd, uMsg, wParam, lParam);
+      break;
+    }
+
+    // These messages are faked via a call to SetWindowPos.
+    case WM_WINDOWPOSCHANGED: {
+      deferred = MakeUnique<DeferredWindowPosMessage>(hwnd, lParam);
+      break;
+    }
+    case WM_NCCALCSIZE: {
+      deferred =
+          MakeUnique<DeferredWindowPosMessage>(hwnd, lParam, true, wParam);
+      break;
+    }
+
+    case WM_COPYDATA: {
+      deferred =
+          MakeUnique<DeferredCopyDataMessage>(hwnd, uMsg, wParam, lParam);
+      res = TRUE;
+      break;
+    }
+
+    case WM_STYLECHANGED: {
+      deferred = MakeUnique<DeferredStyleChangeMessage>(hwnd, wParam, lParam);
+      break;
+    }
+
+    case WM_SETICON: {
+      deferred = MakeUnique<DeferredSetIconMessage>(hwnd, uMsg, wParam, lParam);
+      break;
+    }
+
+    // Messages that are safe to pass to DefWindowProc go here.
+    case WM_ENTERIDLE:
+    case WM_GETICON:
+    case WM_NCPAINT:  // (never trap nc paint events)
+    case WM_GETMINMAXINFO:
+    case WM_GETTEXT:
+    case WM_NCHITTEST:
+    case WM_STYLECHANGING:  // Intentional fall-through.
+    case WM_WINDOWPOSCHANGING:
+    case WM_GETTEXTLENGTH: {
+      return DefWindowProc(hwnd, uMsg, wParam, lParam);
+    }
+
+    // Just return, prevents DefWindowProc from messaging the window
+    // syncronously with other events, which may be deferred. Prevents
+    // random shutdown of aero composition on the window.
+    case WM_SYNCPAINT:
+      return 0;
+
+    // This message causes QuickTime to make re-entrant calls.
+    // Simply discarding it doesn't seem to hurt anything.
+    case WM_APP - 1:
+      return 0;
+
+      // We only support a query for our IAccessible or UIA pointers.
+      // This should be safe, and needs to be sync.
+#if defined(ACCESSIBILITY)
+    case WM_GETOBJECT: {
+      if (!::GetPropW(hwnd, k3rdPartyWindowProp)) {
+        LONG objId = static_cast<LONG>(lParam);
+        if (objId == OBJID_CLIENT || objId == MOZOBJID_UIAROOT) {
+          WNDPROC oldWndProc = (WNDPROC)GetProp(hwnd, kOldWndProcProp);
+          if (oldWndProc) {
+            return CallWindowProcW(oldWndProc, hwnd, uMsg, wParam, lParam);
+          }
+        }
+      }
+      return DefWindowProc(hwnd, uMsg, wParam, lParam);
+    }
+#endif  // ACCESSIBILITY
+
+    default: {
+      // Unknown messages only are logged in debug builds and sent to
+      // DefWindowProc.
+      if (uMsg && uMsg == sAppShellGeckoMsgId) {
+        // Widget's registered native event callback
+        deferred = MakeUnique<DeferredSendMessage>(hwnd, uMsg, wParam, lParam);
+      }
+    }
+  }
+
+  // No deferred message was created and we land here, this is an
+  // unhandled message.
+  if (!deferred) {
+    DumpNeuteredMessage(hwnd, uMsg);
+    return DefWindowProc(hwnd, uMsg, wParam, lParam);
+  }
+
+  // Create the deferred message array if it doesn't exist already.
+  if (!gDeferredMessages) {
+    gDeferredMessages = new DeferredMessageArray(20);
+  }
+
+  // Save for later. The array takes ownership of |deferred|.
+  gDeferredMessages->AppendElement(std::move(deferred));
+  return res;
+}
+
+}  // namespace
+
+LRESULT CALLBACK NeuteredWindowProc(HWND hwnd, UINT uMsg, WPARAM wParam,
+                                    LPARAM lParam) {
+  WNDPROC oldWndProc = (WNDPROC)GetProp(hwnd, kOldWndProcProp);
+  if (!oldWndProc) {
+    // We should really never ever get here.
+    NS_ERROR("No old wndproc!");
+    return DefWindowProc(hwnd, uMsg, wParam, lParam);
+  }
+
+  // See if we care about this message. We may either ignore it, send it to
+  // DefWindowProc, or defer it for later.
+  return ProcessOrDeferMessage(hwnd, uMsg, wParam, lParam);
+}
+
+namespace {
+
+static bool WindowIsDeferredWindow(HWND hWnd) {
+  if (!IsWindow(hWnd)) {
+    NS_WARNING("Window has died!");
+    return false;
+  }
+
+  char16_t buffer[256] = {0};
+  int length = GetClassNameW(hWnd, (wchar_t*)buffer, sizeof(buffer) - 1);
+  if (length <= 0) {
+    NS_WARNING("Failed to get class name!");
+    return false;
+  }
+
+#if defined(ACCESSIBILITY)
+  // Tab content creates a window that responds to accessible WM_GETOBJECT
+  // calls. This window can safely be ignored.
+  if (::GetPropW(hWnd, kPropNameTabContent)) {
+    return false;
+  }
+#endif
+
+  // Common mozilla windows we must defer messages to.
+  nsDependentString className(buffer, length);
+  if (StringBeginsWith(className, u"Mozilla"_ns) ||
+      StringBeginsWith(className, u"Gecko"_ns) ||
+      className.EqualsLiteral("nsToolkitClass") ||
+      className.EqualsLiteral("nsAppShell:EventWindowClass")) {
+    return true;
+  }
+
+  // Plugin windows that can trigger ipc calls in child:
+  // 'ShockwaveFlashFullScreen' - flash fullscreen window
+  if (className.EqualsLiteral("ShockwaveFlashFullScreen")) {
+    SetPropW(hWnd, k3rdPartyWindowProp, (HANDLE)1);
+    return true;
+  }
+
+  return false;
+}
+
+bool NeuterWindowProcedure(HWND hWnd) {
+  if (!WindowIsDeferredWindow(hWnd)) {
+    // Some other kind of window, skip.
+    return false;
+  }
+
+  NS_ASSERTION(!GetProp(hWnd, kOldWndProcProp), "This should always be null!");
+
+  // It's possible to get nullptr out of SetWindowLongPtr, and the only way to
+  // know if that's a valid old value is to use GetLastError. Clear the error
+  // here so we can tell.
+  SetLastError(ERROR_SUCCESS);
+
+  LONG_PTR currentWndProc =
+      SetWindowLongPtr(hWnd, GWLP_WNDPROC, (LONG_PTR)NeuteredWindowProc);
+  if (!currentWndProc) {
+    if (ERROR_SUCCESS == GetLastError()) {
+      // No error, so we set something and must therefore reset it.
+      SetWindowLongPtr(hWnd, GWLP_WNDPROC, currentWndProc);
+    }
+    return false;
+  }
+
+  NS_ASSERTION(currentWndProc != (LONG_PTR)NeuteredWindowProc,
+               "This shouldn't be possible!");
+
+  if (!SetProp(hWnd, kOldWndProcProp, (HANDLE)currentWndProc)) {
+    // Cleanup
+    NS_WARNING("SetProp failed!");
+    SetWindowLongPtr(hWnd, GWLP_WNDPROC, currentWndProc);
+    RemovePropW(hWnd, kOldWndProcProp);
+    RemovePropW(hWnd, k3rdPartyWindowProp);
+    return false;
+  }
+
+  return true;
+}
+
+void RestoreWindowProcedure(HWND hWnd) {
+  NS_ASSERTION(WindowIsDeferredWindow(hWnd),
+               "Not a deferred window, this shouldn't be in our list!");
+  LONG_PTR oldWndProc = (LONG_PTR)GetProp(hWnd, kOldWndProcProp);
+  if (oldWndProc) {
+    NS_ASSERTION(oldWndProc != (LONG_PTR)NeuteredWindowProc,
+                 "This shouldn't be possible!");
+
+    DebugOnly<LONG_PTR> currentWndProc =
+        SetWindowLongPtr(hWnd, GWLP_WNDPROC, oldWndProc);
+    NS_ASSERTION(currentWndProc == (LONG_PTR)NeuteredWindowProc,
+                 "This should never be switched out from under us!");
+  }
+  RemovePropW(hWnd, kOldWndProcProp);
+  RemovePropW(hWnd, k3rdPartyWindowProp);
+}
+
+LRESULT CALLBACK CallWindowProcedureHook(int nCode, WPARAM wParam,
+                                         LPARAM lParam) {
+  if (nCode >= 0) {
+    NS_ASSERTION(gNeuteredWindows, "This should never be null!");
+
+    HWND hWnd = reinterpret_cast<CWPSTRUCT*>(lParam)->hwnd;
+
+    if (!gNeuteredWindows->Contains(hWnd) &&
+        !SuppressedNeuteringRegion::IsNeuteringSuppressed() &&
+        NeuterWindowProcedure(hWnd)) {
+      // XXX(Bug 1631371) Check if this should use a fallible operation as it
+      // pretended earlier.
+      gNeuteredWindows->AppendElement(hWnd);
+    }
+  }
+  return CallNextHookEx(nullptr, nCode, wParam, lParam);
+}
+
+inline void AssertWindowIsNotNeutered(HWND hWnd) {
+#ifdef DEBUG
+  // Make sure our neutered window hook isn't still in place.
+  LONG_PTR wndproc = GetWindowLongPtr(hWnd, GWLP_WNDPROC);
+  NS_ASSERTION(wndproc != (LONG_PTR)NeuteredWindowProc, "Window is neutered!");
+#endif
+}
+
+void UnhookNeuteredWindows() {
+  if (!gNeuteredWindows) return;
+  uint32_t count = gNeuteredWindows->Length();
+  for (uint32_t index = 0; index < count; index++) {
+    RestoreWindowProcedure(gNeuteredWindows->ElementAt(index));
+  }
+  gNeuteredWindows->Clear();
+}
+
+// This timeout stuff assumes a sane value of mTimeoutMs (less than the overflow
+// value for GetTickCount(), which is something like 50 days). It uses the
+// cheapest (and least accurate) method supported by Windows 2000.
+
+struct TimeoutData {
+  DWORD startTicks;
+  DWORD targetTicks;
+};
+
+void InitTimeoutData(TimeoutData* aData, int32_t aTimeoutMs) {
+  aData->startTicks = GetTickCount();
+  if (!aData->startTicks) {
+    // How unlikely is this!
+    aData->startTicks++;
+  }
+  aData->targetTicks = aData->startTicks + aTimeoutMs;
+}
+
+bool TimeoutHasExpired(const TimeoutData& aData) {
+  if (!aData.startTicks) {
+    return false;
+  }
+
+  DWORD now = GetTickCount();
+
+  if (aData.targetTicks < aData.startTicks) {
+    // Overflow
+    return now < aData.startTicks && now >= aData.targetTicks;
+  }
+  return now >= aData.targetTicks;
+}
+
+}  // namespace
+
+namespace mozilla {
+namespace ipc {
+namespace windows {
+
+void InitUIThread() {
+  if (!XRE_UseNativeEventProcessing()) {
+    return;
+  }
+  // If we aren't setup before a call to NotifyWorkerThread, we'll hang
+  // on startup.
+  if (!gUIThreadId) {
+    gUIThreadId = GetCurrentThreadId();
+  }
+
+  MOZ_ASSERT(gUIThreadId);
+  MOZ_ASSERT(gUIThreadId == GetCurrentThreadId(),
+             "Called InitUIThread multiple times on different threads!");
+
+  if (!gWinEventHook && !mscom::IsCurrentThreadMTA()) {
+    gWinEventHook = SetWinEventHook(EVENT_OBJECT_CREATE, EVENT_OBJECT_DESTROY,
+                                    NULL, &WinEventHook, GetCurrentProcessId(),
+                                    gUIThreadId, WINEVENT_OUTOFCONTEXT);
+    MOZ_ASSERT(gWinEventHook);
+
+    // We need to execute this after setting the hook in case the OLE window
+    // already existed.
+    gCOMWindow = FindCOMWindow();
+  }
+}
+
+}  // namespace windows
+}  // namespace ipc
+}  // namespace mozilla
+
+// See SpinInternalEventLoop below
+MessageChannel::SyncStackFrame::SyncStackFrame(MessageChannel* channel)
+    : mSpinNestedEvents(false),
+      mListenerNotified(false),
+      mChannel(channel),
+      mPrev(mChannel->mTopFrame),
+      mStaticPrev(sStaticTopFrame) {
+  // Only track stack frames when Windows message deferral behavior
+  // is request for the channel.
+  if (!(mChannel->GetChannelFlags() & REQUIRE_DEFERRED_MESSAGE_PROTECTION)) {
+    return;
+  }
+
+  mChannel->mTopFrame = this;
+  sStaticTopFrame = this;
+
+  if (!mStaticPrev) {
+    NS_ASSERTION(!gNeuteredWindows, "Should only set this once!");
+    gNeuteredWindows = new AutoTArray<HWND, 20>();
+    NS_ASSERTION(gNeuteredWindows, "Out of memory!");
+  }
+}
+
+MessageChannel::SyncStackFrame::~SyncStackFrame() {
+  if (!(mChannel->GetChannelFlags() & REQUIRE_DEFERRED_MESSAGE_PROTECTION)) {
+    return;
+  }
+
+  NS_ASSERTION(this == mChannel->mTopFrame,
+               "Mismatched interrupt stack frames");
+  NS_ASSERTION(this == sStaticTopFrame,
+               "Mismatched static Interrupt stack frames");
+
+  mChannel->mTopFrame = mPrev;
+  sStaticTopFrame = mStaticPrev;
+
+  if (!mStaticPrev) {
+    NS_ASSERTION(gNeuteredWindows, "Bad pointer!");
+    delete gNeuteredWindows;
+    gNeuteredWindows = nullptr;
+  }
+}
+
+MessageChannel::SyncStackFrame* MessageChannel::sStaticTopFrame;
+
+// nsAppShell's notification that gecko events are being processed.
+// If we are here and there is an Interrupt Incall active, we are spinning
+// a nested gecko event loop. In which case the remote process needs
+// to know about it.
+void /* static */
+MessageChannel::NotifyGeckoEventDispatch() {
+  // sStaticTopFrame is only valid for Interrupt channels
+  if (!sStaticTopFrame || sStaticTopFrame->mListenerNotified) return;
+
+  sStaticTopFrame->mListenerNotified = true;
+  MessageChannel* channel =
+      static_cast<MessageChannel*>(sStaticTopFrame->mChannel);
+  channel->Listener()->ProcessRemoteNativeEventsInInterruptCall();
+}
+
+// invoked by the module that receives the spin event loop
+// message.
+void MessageChannel::ProcessNativeEventsInInterruptCall() {
+  NS_ASSERTION(GetCurrentThreadId() == gUIThreadId,
+               "Shouldn't be on a non-main thread in here!");
+  if (!mTopFrame) {
+    NS_ERROR("Spin logic error: no Interrupt frame");
+    return;
+  }
+
+  mTopFrame->mSpinNestedEvents = true;
+}
+
+// Spin loop is called in place of WaitFor*Notify when modal ui is being shown
+// in a child. There are some intricacies in using it however. Spin loop is
+// enabled for a particular Interrupt frame by the client calling
+// MessageChannel::ProcessNativeEventsInInterrupt().
+// This call can be nested for multiple Interrupt frames in a single plugin or
+// multiple unrelated plugins.
+void MessageChannel::SpinInternalEventLoop() {
+  if (mozilla::PaintTracker::IsPainting()) {
+    MOZ_CRASH("Don't spin an event loop while painting.");
+  }
+
+  NS_ASSERTION(mTopFrame && mTopFrame->mSpinNestedEvents,
+               "Spinning incorrectly");
+
+  // Nested windows event loop we trigger when the child enters into modal
+  // event loops.
+
+  // Note, when we return, we always reset the notify worker event. So there's
+  // no need to reset it on return here.
+
+  do {
+    MSG msg = {0};
+
+    // Don't get wrapped up in here if the child connection dies.
+    {
+      MonitorAutoLock lock(*mMonitor);
+      if (!Connected()) {
+        return;
+      }
+    }
+
+    // Retrieve window or thread messages
+    if (PeekMessageW(&msg, nullptr, 0, 0, PM_REMOVE)) {
+      // The child UI should have been destroyed before the app is closed, in
+      // which case, we should never get this here.
+      if (msg.message == WM_QUIT) {
+        NS_ERROR("WM_QUIT received in SpinInternalEventLoop!");
+      } else {
+        TranslateMessage(&msg);
+        ::DispatchMessageW(&msg);
+        return;
+      }
+    }
+
+    // Note, give dispatching windows events priority over checking if
+    // mEvent is signaled, otherwise heavy ipc traffic can cause jittery
+    // playback of video. We'll exit out on each disaptch above, so ipc
+    // won't get starved.
+
+    // Wait for UI events or a signal from the io thread.
+    DWORD result =
+        MsgWaitForMultipleObjects(1, &mEvent, FALSE, INFINITE, QS_ALLINPUT);
+    if (result == WAIT_OBJECT_0) {
+      // Our NotifyWorkerThread event was signaled
+      return;
+    }
+  } while (true);
+}
+
+static HHOOK gWindowHook;
+
+static inline void StartNeutering() {
+  if (!gUIThreadId) {
+    mozilla::ipc::windows::InitUIThread();
+  }
+  MOZ_ASSERT(gUIThreadId);
+  MOZ_ASSERT(!gWindowHook);
+  NS_ASSERTION(!MessageChannel::IsPumpingMessages(),
+               "Shouldn't be pumping already!");
+  MessageChannel::SetIsPumpingMessages(true);
+  gWindowHook = ::SetWindowsHookEx(WH_CALLWNDPROC, CallWindowProcedureHook,
+                                   nullptr, gUIThreadId);
+  NS_ASSERTION(gWindowHook, "Failed to set hook!");
+}
+
+static void StopNeutering() {
+  MOZ_ASSERT(MessageChannel::IsPumpingMessages());
+  ::UnhookWindowsHookEx(gWindowHook);
+  gWindowHook = NULL;
+  ::UnhookNeuteredWindows();
+  // Before returning we need to set a hook to run any deferred messages that
+  // we received during the IPC call. The hook will unset itself as soon as
+  // someone else calls GetMessage, PeekMessage, or runs code that generates
+  // a "nonqueued" message.
+  ::ScheduleDeferredMessageRun();
+  MessageChannel::SetIsPumpingMessages(false);
+}
+
+NeuteredWindowRegion::NeuteredWindowRegion(bool aDoNeuter)
+    : mNeuteredByThis(!gWindowHook && aDoNeuter &&
+                      XRE_UseNativeEventProcessing()) {
+  if (mNeuteredByThis) {
+    StartNeutering();
+  }
+}
+
+NeuteredWindowRegion::~NeuteredWindowRegion() {
+  if (gWindowHook && mNeuteredByThis) {
+    StopNeutering();
+  }
+}
+
+void NeuteredWindowRegion::PumpOnce() {
+  if (!gWindowHook) {
+    // This should be a no-op if nothing has been neutered.
+    return;
+  }
+
+  MSG msg = {0};
+  // Pump any COM messages so that we don't hang due to STA marshaling.
+  if (gCOMWindow && ::PeekMessageW(&msg, gCOMWindow, 0, 0, PM_REMOVE)) {
+    ::TranslateMessage(&msg);
+    ::DispatchMessageW(&msg);
+  }
+  // Expunge any nonqueued messages on the current thread.
+  ::PeekMessageW(&msg, nullptr, 0, 0, PM_NOREMOVE);
+}
+
+DeneuteredWindowRegion::DeneuteredWindowRegion()
+    : mReneuter(gWindowHook != NULL) {
+  if (mReneuter) {
+    StopNeutering();
+  }
+}
+
+DeneuteredWindowRegion::~DeneuteredWindowRegion() {
+  if (mReneuter) {
+    StartNeutering();
+  }
+}
+
+SuppressedNeuteringRegion::SuppressedNeuteringRegion()
+    : mReenable(::gUIThreadId == ::GetCurrentThreadId() && ::gWindowHook) {
+  if (mReenable) {
+    MOZ_ASSERT(!sSuppressNeutering);
+    sSuppressNeutering = true;
+  }
+}
+
+SuppressedNeuteringRegion::~SuppressedNeuteringRegion() {
+  if (mReenable) {
+    MOZ_ASSERT(sSuppressNeutering);
+    sSuppressNeutering = false;
+  }
+}
+
+bool SuppressedNeuteringRegion::sSuppressNeutering = false;
+
+bool MessageChannel::WaitForSyncNotify() {
+  mMonitor->AssertCurrentThreadOwns();
+
+  if (!gUIThreadId) {
+    mozilla::ipc::windows::InitUIThread();
+  }
+
+  // Use a blocking wait if this channel does not require
+  // Windows message deferral behavior.
+  if (!(mFlags & REQUIRE_DEFERRED_MESSAGE_PROTECTION)) {
+    TimeDuration timeout = (kNoTimeout == mTimeoutMs)
+                               ? TimeDuration::Forever()
+                               : TimeDuration::FromMilliseconds(mTimeoutMs);
+
+    MOZ_ASSERT(!mIsSyncWaitingOnNonMainThread);
+    mIsSyncWaitingOnNonMainThread = true;
+
+    CVStatus status = mMonitor->Wait(timeout);
+
+    MOZ_ASSERT(mIsSyncWaitingOnNonMainThread);
+    mIsSyncWaitingOnNonMainThread = false;
+
+    // If the timeout didn't expire, we know we received an event. The
+    // converse is not true.
+    return WaitResponse(status == CVStatus::Timeout);
+  }
+
+  NS_ASSERTION(
+      mFlags & REQUIRE_DEFERRED_MESSAGE_PROTECTION,
+      "Shouldn't be here for channels that don't use message deferral!");
+  NS_ASSERTION(mTopFrame, "No top frame!");
+
+  MonitorAutoUnlock unlock(*mMonitor);
+
+  bool timedout = false;
+
+  UINT_PTR timerId = 0;
+  TimeoutData timeoutData = {0};
+
+  if (mTimeoutMs != kNoTimeout) {
+    InitTimeoutData(&timeoutData, mTimeoutMs);
+
+    // We only do this to ensure that we won't get stuck in
+    // MsgWaitForMultipleObjects below.
+    timerId = SetTimer(nullptr, 0, mTimeoutMs, nullptr);
+    NS_ASSERTION(timerId, "SetTimer failed!");
+  }
+
+  NeuteredWindowRegion neuteredRgn(true);
+
+  {
+    while (1) {
+      MSG msg = {0};
+      // Don't get wrapped up in here if the child connection dies.
+      {
+        MonitorAutoLock lock(*mMonitor);
+        if (!Connected()) {
+          break;
+        }
+      }
+
+      // Wait until we have a message in the queue. MSDN docs are a bit unclear
+      // but it seems that windows from two different threads (and it should be
+      // noted that a thread in another process counts as a "different thread")
+      // will implicitly have their message queues attached if they are parented
+      // to one another. This wait call, then, will return for a message
+      // delivered to *either* thread.
+      DWORD result =
+          MsgWaitForMultipleObjects(1, &mEvent, FALSE, INFINITE, QS_ALLINPUT);
+      if (result == WAIT_OBJECT_0) {
+        // Our NotifyWorkerThread event was signaled
+        BOOL success = ResetEvent(mEvent);
+        if (!success) {
+          gfxDevCrash(mozilla::gfx::LogReason::MessageChannelInvalidHandle)
+              << "WindowsMessageChannel::WaitForSyncNotify failed to reset "
+                 "event. GetLastError: "
+              << GetLastError();
+        }
+        break;
+      } else if (result != (WAIT_OBJECT_0 + 1)) {
+        NS_ERROR("Wait failed!");
+        break;
+      }
+
+      if (TimeoutHasExpired(timeoutData)) {
+        // A timeout was specified and we've passed it. Break out.
+        timedout = true;
+        break;
+      }
+
+      // The only way to know on which thread the message was delivered is to
+      // use some logic on the return values of GetQueueStatus and PeekMessage.
+      // PeekMessage will return false if there are no "queued" messages, but it
+      // will run all "nonqueued" messages before returning. So if PeekMessage
+      // returns false and there are no "nonqueued" messages that were run then
+      // we know that the message we woke for was intended for a window on
+      // another thread.
+      bool haveSentMessagesPending =
+          (HIWORD(GetQueueStatus(QS_SENDMESSAGE)) & QS_SENDMESSAGE) != 0;
+
+      // Either of the PeekMessage calls below will actually process all
+      // "nonqueued" messages that are pending before returning. If we have
+      // "nonqueued" messages pending then we should have switched out all the
+      // window procedures above. In that case this PeekMessage call won't
+      // actually cause any mozilla code (or plugin code) to run.
+
+      // We have to manually pump all COM messages *after* looking at the queue
+      // queue status but before yielding our thread below.
+      if (gCOMWindow) {
+        if (PeekMessageW(&msg, gCOMWindow, 0, 0, PM_REMOVE)) {
+          TranslateMessage(&msg);
+          ::DispatchMessageW(&msg);
+        }
+      }
+
+      // If the following PeekMessage call fails to return a message for us (and
+      // returns false) and we didn't run any "nonqueued" messages then we must
+      // have woken up for a message designated for a window in another thread.
+      // If we loop immediately then we could enter a tight loop, so we'll give
+      // up our time slice here to let the child process its message.
+      if (!PeekMessageW(&msg, nullptr, 0, 0, PM_NOREMOVE) &&
+          !haveSentMessagesPending) {
+        // Message was for child, we should wait a bit.
+        SwitchToThread();
+      }
+    }
+  }
+
+  if (timerId) {
+    KillTimer(nullptr, timerId);
+    timerId = 0;
+  }
+
+  return WaitResponse(timedout);
+}
+
+void MessageChannel::NotifyWorkerThread() {
+  mMonitor->AssertCurrentThreadOwns();
+
+  if (mIsSyncWaitingOnNonMainThread) {
+    mMonitor->Notify();
+    return;
+  }
+
+  MOZ_RELEASE_ASSERT(mEvent, "No signal event to set, this is really bad!");
+  if (!SetEvent(mEvent)) {
+    NS_WARNING("Failed to set NotifyWorkerThread event!");
+    gfxDevCrash(mozilla::gfx::LogReason::MessageChannelInvalidHandle)
+        << "WindowsMessageChannel failed to SetEvent. GetLastError: "
+        << GetLastError();
+  }
+}
+
+void DeferredSendMessage::Run() {
+  AssertWindowIsNotNeutered(hWnd);
+  if (!IsWindow(hWnd)) {
+    NS_ERROR("Invalid window!");
+    return;
+  }
+
+  WNDPROC wndproc =
+      reinterpret_cast<WNDPROC>(GetWindowLongPtr(hWnd, GWLP_WNDPROC));
+  if (!wndproc) {
+    NS_ERROR("Invalid window procedure!");
+    return;
+  }
+
+  CallWindowProc(wndproc, hWnd, message, wParam, lParam);
+}
+
+void DeferredRedrawMessage::Run() {
+  AssertWindowIsNotNeutered(hWnd);
+  if (!IsWindow(hWnd)) {
+    NS_ERROR("Invalid window!");
+    return;
+  }
+
+#ifdef DEBUG
+  BOOL ret =
+#endif
+      RedrawWindow(hWnd, nullptr, nullptr, flags);
+  NS_ASSERTION(ret, "RedrawWindow failed!");
+}
+
+DeferredUpdateMessage::DeferredUpdateMessage(HWND aHWnd) {
+  mWnd = aHWnd;
+  if (!GetUpdateRect(mWnd, &mUpdateRect, FALSE)) {
+    memset(&mUpdateRect, 0, sizeof(RECT));
+    return;
+  }
+  ValidateRect(mWnd, &mUpdateRect);
+}
+
+void DeferredUpdateMessage::Run() {
+  AssertWindowIsNotNeutered(mWnd);
+  if (!IsWindow(mWnd)) {
+    NS_ERROR("Invalid window!");
+    return;
+  }
+
+  InvalidateRect(mWnd, &mUpdateRect, FALSE);
+#ifdef DEBUG
+  BOOL ret =
+#endif
+      UpdateWindow(mWnd);
+  NS_ASSERTION(ret, "UpdateWindow failed!");
+}
+
+DeferredSettingChangeMessage::DeferredSettingChangeMessage(HWND aHWnd,
+                                                           UINT aMessage,
+                                                           WPARAM aWParam,
+                                                           LPARAM aLParam)
+    : DeferredSendMessage(aHWnd, aMessage, aWParam, aLParam) {
+  NS_ASSERTION(aMessage == WM_SETTINGCHANGE, "Wrong message type!");
+  if (aLParam) {
+    lParamString = _wcsdup(reinterpret_cast<const wchar_t*>(aLParam));
+    lParam = reinterpret_cast<LPARAM>(lParamString);
+  } else {
+    lParamString = nullptr;
+    lParam = 0;
+  }
+}
+
+DeferredSettingChangeMessage::~DeferredSettingChangeMessage() {
+  free(lParamString);
+}
+
+DeferredWindowPosMessage::DeferredWindowPosMessage(HWND aHWnd, LPARAM aLParam,
+                                                   bool aForCalcSize,
+                                                   WPARAM aWParam) {
+  if (aForCalcSize) {
+    if (aWParam) {
+      NCCALCSIZE_PARAMS* arg = reinterpret_cast<NCCALCSIZE_PARAMS*>(aLParam);
+      memcpy(&windowPos, arg->lppos, sizeof(windowPos));
+
+      NS_ASSERTION(aHWnd == windowPos.hwnd, "Mismatched hwnds!");
+    } else {
+      RECT* arg = reinterpret_cast<RECT*>(aLParam);
+      windowPos.hwnd = aHWnd;
+      windowPos.hwndInsertAfter = nullptr;
+      windowPos.x = arg->left;
+      windowPos.y = arg->top;
+      windowPos.cx = arg->right - arg->left;
+      windowPos.cy = arg->bottom - arg->top;
+
+      NS_ASSERTION(arg->right >= arg->left && arg->bottom >= arg->top,
+                   "Negative width or height!");
+    }
+    windowPos.flags = SWP_FRAMECHANGED | SWP_NOACTIVATE | SWP_NOOWNERZORDER |
+                      SWP_NOZORDER | SWP_DEFERERASE | SWP_NOSENDCHANGING;
+  } else {
+    // Not for WM_NCCALCSIZE
+    WINDOWPOS* arg = reinterpret_cast<WINDOWPOS*>(aLParam);
+    memcpy(&windowPos, arg, sizeof(windowPos));
+
+    NS_ASSERTION(aHWnd == windowPos.hwnd, "Mismatched hwnds!");
+
+    // Windows sends in some private flags sometimes that we can't simply copy.
+    // Filter here.
+    UINT mask = SWP_ASYNCWINDOWPOS | SWP_DEFERERASE | SWP_DRAWFRAME |
+                SWP_FRAMECHANGED | SWP_HIDEWINDOW | SWP_NOACTIVATE |
+                SWP_NOCOPYBITS | SWP_NOMOVE | SWP_NOOWNERZORDER | SWP_NOREDRAW |
+                SWP_NOREPOSITION | SWP_NOSENDCHANGING | SWP_NOSIZE |
+                SWP_NOZORDER | SWP_SHOWWINDOW;
+    windowPos.flags &= mask;
+  }
+}
+
+void DeferredWindowPosMessage::Run() {
+  AssertWindowIsNotNeutered(windowPos.hwnd);
+  if (!IsWindow(windowPos.hwnd)) {
+    NS_ERROR("Invalid window!");
+    return;
+  }
+
+  if (!IsWindow(windowPos.hwndInsertAfter)) {
+    NS_WARNING("ZOrder change cannot be honored");
+    windowPos.hwndInsertAfter = 0;
+    windowPos.flags |= SWP_NOZORDER;
+  }
+
+#ifdef DEBUG
+  BOOL ret =
+#endif
+      SetWindowPos(windowPos.hwnd, windowPos.hwndInsertAfter, windowPos.x,
+                   windowPos.y, windowPos.cx, windowPos.cy, windowPos.flags);
+  NS_ASSERTION(ret, "SetWindowPos failed!");
+}
+
+DeferredCopyDataMessage::DeferredCopyDataMessage(HWND aHWnd, UINT aMessage,
+                                                 WPARAM aWParam, LPARAM aLParam)
+    : DeferredSendMessage(aHWnd, aMessage, aWParam, aLParam) {
+  NS_ASSERTION(IsWindow(reinterpret_cast<HWND>(aWParam)), "Bad window!");
+
+  COPYDATASTRUCT* source = reinterpret_cast<COPYDATASTRUCT*>(aLParam);
+  NS_ASSERTION(source, "Should never be null!");
+
+  copyData.dwData = source->dwData;
+  copyData.cbData = source->cbData;
+
+  if (source->cbData) {
+    copyData.lpData = malloc(source->cbData);
+    if (copyData.lpData) {
+      memcpy(copyData.lpData, source->lpData, source->cbData);
+    } else {
+      NS_ERROR("Out of memory?!");
+      copyData.cbData = 0;
+    }
+  } else {
+    copyData.lpData = nullptr;
+  }
+
+  lParam = reinterpret_cast<LPARAM>(&copyData);
+}
+
+DeferredCopyDataMessage::~DeferredCopyDataMessage() { free(copyData.lpData); }
+
+DeferredStyleChangeMessage::DeferredStyleChangeMessage(HWND aHWnd,
+                                                       WPARAM aWParam,
+                                                       LPARAM aLParam)
+    : hWnd(aHWnd) {
+  index = static_cast<int>(aWParam);
+  style = reinterpret_cast<STYLESTRUCT*>(aLParam)->styleNew;
+}
+
+void DeferredStyleChangeMessage::Run() { SetWindowLongPtr(hWnd, index, style); }
+
+DeferredSetIconMessage::DeferredSetIconMessage(HWND aHWnd, UINT aMessage,
+                                               WPARAM aWParam, LPARAM aLParam)
+    : DeferredSendMessage(aHWnd, aMessage, aWParam, aLParam) {
+  NS_ASSERTION(aMessage == WM_SETICON, "Wrong message type!");
+}
+
+void DeferredSetIconMessage::Run() {
+  AssertWindowIsNotNeutered(hWnd);
+  if (!IsWindow(hWnd)) {
+    NS_ERROR("Invalid window!");
+    return;
+  }
+
+  WNDPROC wndproc =
+      reinterpret_cast<WNDPROC>(GetWindowLongPtr(hWnd, GWLP_WNDPROC));
+  if (!wndproc) {
+    NS_ERROR("Invalid window procedure!");
+    return;
+  }
+
+  HICON hOld = reinterpret_cast<HICON>(
+      CallWindowProc(wndproc, hWnd, message, wParam, lParam));
+  if (hOld) {
+    DestroyIcon(hOld);
+  }
+}
diff --git a/ipc/glue/WindowsMessageLoop.h b/ipc/glue/WindowsMessageLoop.h
new file mode 100644
index 0000000000..7fa614279b
--- /dev/null
+++ b/ipc/glue/WindowsMessageLoop.h
@@ -0,0 +1,134 @@
+/* -*- 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 IPC_GLUE_WINDOWSMESSAGELOOP_H
+#define IPC_GLUE_WINDOWSMESSAGELOOP_H
+
+// This file is only meant to compile on windows
+#include <windows.h>
+
+#include "nsISupportsImpl.h"
+
+namespace mozilla {
+namespace ipc {
+namespace windows {
+
+void InitUIThread();
+
+class DeferredMessage {
+ public:
+  MOZ_COUNTED_DEFAULT_CTOR(DeferredMessage)
+
+  MOZ_COUNTED_DTOR_VIRTUAL(DeferredMessage)
+
+  virtual void Run() = 0;
+};
+
+// Uses CallWndProc to deliver a message at a later time. Messages faked with
+// this class must not have pointers in their wParam or lParam members as they
+// may be invalid by the time the message actually runs.
+class DeferredSendMessage : public DeferredMessage {
+ public:
+  DeferredSendMessage(HWND aHWnd, UINT aMessage, WPARAM aWParam, LPARAM aLParam)
+      : hWnd(aHWnd), message(aMessage), wParam(aWParam), lParam(aLParam) {}
+
+  virtual void Run();
+
+ protected:
+  HWND hWnd;
+  UINT message;
+  WPARAM wParam;
+  LPARAM lParam;
+};
+
+// Uses RedrawWindow to fake several painting-related messages. Flags passed
+// to the constructor go directly to RedrawWindow.
+class DeferredRedrawMessage : public DeferredMessage {
+ public:
+  DeferredRedrawMessage(HWND aHWnd, UINT aFlags) : hWnd(aHWnd), flags(aFlags) {}
+
+  virtual void Run();
+
+ private:
+  HWND hWnd;
+  UINT flags;
+};
+
+// Uses UpdateWindow to generate a WM_PAINT message if needed.
+class DeferredUpdateMessage : public DeferredMessage {
+ public:
+  explicit DeferredUpdateMessage(HWND aHWnd);
+
+  virtual void Run();
+
+ private:
+  HWND mWnd;
+  RECT mUpdateRect;
+};
+
+// This class duplicates a string that may exist in the lParam member of the
+// message.
+class DeferredSettingChangeMessage : public DeferredSendMessage {
+ public:
+  DeferredSettingChangeMessage(HWND aHWnd, UINT aMessage, WPARAM aWParam,
+                               LPARAM aLParam);
+
+  ~DeferredSettingChangeMessage();
+
+ private:
+  wchar_t* lParamString;
+};
+
+// This class uses SetWindowPos to fake various size-related messages. Flags
+// passed to the constructor go straight through to SetWindowPos.
+class DeferredWindowPosMessage : public DeferredMessage {
+ public:
+  DeferredWindowPosMessage(HWND aHWnd, LPARAM aLParam,
+                           bool aForCalcSize = false, WPARAM aWParam = 0);
+
+  virtual void Run();
+
+ private:
+  WINDOWPOS windowPos;
+};
+
+// This class duplicates a data buffer for a WM_COPYDATA message.
+class DeferredCopyDataMessage : public DeferredSendMessage {
+ public:
+  DeferredCopyDataMessage(HWND aHWnd, UINT aMessage, WPARAM aWParam,
+                          LPARAM aLParam);
+
+  ~DeferredCopyDataMessage();
+
+ private:
+  COPYDATASTRUCT copyData;
+};
+
+class DeferredStyleChangeMessage : public DeferredMessage {
+ public:
+  DeferredStyleChangeMessage(HWND aHWnd, WPARAM aWParam, LPARAM aLParam);
+
+  virtual void Run();
+
+ private:
+  HWND hWnd;
+  int index;
+  LONG_PTR style;
+};
+
+class DeferredSetIconMessage : public DeferredSendMessage {
+ public:
+  DeferredSetIconMessage(HWND aHWnd, UINT aMessage, WPARAM aWParam,
+                         LPARAM aLParam);
+
+  virtual void Run();
+};
+
+} /* namespace windows */
+} /* namespace ipc */
+} /* namespace mozilla */
+
+#endif /* IPC_GLUE_WINDOWSMESSAGELOOP_H */
diff --git a/ipc/glue/components.conf b/ipc/glue/components.conf
new file mode 100644
index 0000000000..34048dbbfa
--- /dev/null
+++ b/ipc/glue/components.conf
@@ -0,0 +1,22 @@
+# -*- 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/.
+
+Headers = [
+    'mozilla/ipc/ForkServer.h',
+]
+
+Classes = [
+    {
+        'cid': '{cdb4757f-f51b-40c0-8b38-66d12c3bff7b}',
+        'contract_ids': ['@mozilla.org/fork-server-launcher;1'],
+        'singleton': True,
+        'type': 'mozilla::ipc::ForkServerLauncher',
+        'headers': ['mozilla/ipc/ForkServiceChild.h'],
+        'constructor': 'mozilla::ipc::ForkServerLauncher::Create',
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        'categories': {'xpcom-startup': 'Fork Server Launcher'},
+    },
+]
diff --git a/ipc/glue/moz.build b/ipc/glue/moz.build
new file mode 100644
index 0000000000..3651a9794e
--- /dev/null
+++ b/ipc/glue/moz.build
@@ -0,0 +1,307 @@
+# -*- 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/.
+include("/dom/media/webrtc/third_party_build/webrtc.mozbuild")
+
+EXPORTS += [
+    "nsIIPCSerializableInputStream.h",
+]
+
+EXPORTS.mozilla.ipc += [
+    "AsyncBlockers.h",
+    "BackgroundChild.h",
+    "BackgroundParent.h",
+    "BackgroundStarterChild.h",
+    "BackgroundStarterParent.h",
+    "BackgroundUtils.h",
+    "BigBuffer.h",
+    "BrowserProcessSubThread.h",
+    "ByteBuf.h",
+    "ByteBufUtils.h",
+    "CrashReporterClient.h",
+    "CrashReporterHelper.h",
+    "CrashReporterHost.h",
+    "CrossProcessMutex.h",
+    "CrossProcessSemaphore.h",
+    "DataPipe.h",
+    "Endpoint.h",
+    "EnvironmentMap.h",
+    "FileDescriptor.h",
+    "FileDescriptorUtils.h",
+    "GeckoChildProcessHost.h",
+    "IdleSchedulerChild.h",
+    "IdleSchedulerParent.h",
+    "InputStreamUtils.h",
+    "IOThreadChild.h",
+    "IPCCore.h",
+    "IPCForwards.h",
+    "IPCStreamUtils.h",
+    "IPCTypes.h",
+    "IPDLParamTraits.h",
+    "IPDLStructMember.h",
+    "LaunchError.h",
+    "LibrarySandboxPreload.h",
+    "MessageChannel.h",
+    "MessageLink.h",
+    "MessagePump.h",
+    "Neutering.h",
+    "NodeChannel.h",
+    "NodeController.h",
+    "ProcessChild.h",
+    "ProcessUtils.h",
+    "ProtocolMessageUtils.h",
+    "ProtocolUtils.h",
+    "RandomAccessStreamUtils.h",
+    "RawShmem.h",
+    "ScopedPort.h",
+    "SerializedStructuredCloneBuffer.h",
+    "SharedMemory.h",
+    "SharedMemoryBasic.h",
+    "Shmem.h",
+    "ShmemMessageUtils.h",
+    "SideVariant.h",
+    "TaintingIPCUtils.h",
+    "TaskFactory.h",
+    "ToplevelActorHolder.h",
+    "TransportSecurityInfoUtils.h",
+    "URIUtils.h",
+    "UtilityAudioDecoder.h",
+    "UtilityAudioDecoderChild.h",
+    "UtilityAudioDecoderParent.h",
+    "UtilityProcessChild.h",
+    "UtilityProcessHost.h",
+    "UtilityProcessImpl.h",
+    "UtilityProcessManager.h",
+    "UtilityProcessParent.h",
+    "UtilityProcessSandboxing.h",
+    "WindowsMessageLoop.h",
+]
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    SOURCES += [
+        "SharedMemory_windows.cpp",
+        "WindowsMessageLoop.cpp",
+    ]
+else:
+    UNIFIED_SOURCES += [
+        "SharedMemory_posix.cpp",
+    ]
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    SOURCES += [
+        "CrossProcessMutex_windows.cpp",
+    ]
+elif not CONFIG["OS_ARCH"] in ("NetBSD", "OpenBSD"):
+    UNIFIED_SOURCES += [
+        "CrossProcessMutex_posix.cpp",
+    ]
+else:
+    UNIFIED_SOURCES += [
+        "CrossProcessMutex_unimplemented.cpp",
+    ]
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    SOURCES += [
+        "CrossProcessSemaphore_windows.cpp",
+    ]
+elif CONFIG["OS_ARCH"] != "Darwin":
+    UNIFIED_SOURCES += [
+        "CrossProcessSemaphore_posix.cpp",
+    ]
+else:
+    UNIFIED_SOURCES += [
+        "CrossProcessSemaphore_unimplemented.cpp",
+    ]
+
+# Android has its own,
+# almost-but-not-quite-compatible-with-POSIX-or-/dev/shm shared memory
+# impl.
+if CONFIG["OS_TARGET"] == "Android":
+    EXPORTS.mozilla.ipc += ["SharedMemoryBasic_android.h"]
+    UNIFIED_SOURCES += [
+        "SharedMemoryBasic_android.cpp",
+    ]
+elif CONFIG["OS_ARCH"] == "Darwin":
+    EXPORTS.mozilla.ipc += ["SharedMemoryBasic_mach.h"]
+    SOURCES += [
+        "SharedMemoryBasic_mach.mm",
+    ]
+else:
+    EXPORTS.mozilla.ipc += ["SharedMemoryBasic_chromium.h"]
+
+if CONFIG["OS_ARCH"] == "Linux":
+    UNIFIED_SOURCES += [
+        "ProcessUtils_linux.cpp",
+    ]
+elif CONFIG["OS_ARCH"] in ("DragonFly", "FreeBSD", "NetBSD", "OpenBSD"):
+    UNIFIED_SOURCES += ["ProcessUtils_bsd.cpp"]
+elif CONFIG["OS_ARCH"] == "Darwin":
+    UNIFIED_SOURCES += ["ProcessUtils_mac.mm"]
+else:
+    UNIFIED_SOURCES += [
+        "ProcessUtils_none.cpp",
+    ]
+
+if CONFIG["OS_ARCH"] != "WINNT":
+    EXPORTS.mozilla.ipc += [
+        "FileDescriptorShuffle.h",
+    ]
+    UNIFIED_SOURCES += [
+        "FileDescriptorShuffle.cpp",
+    ]
+
+EXPORTS.ipc += [
+    "EnumSerializer.h",
+    "IPCMessageUtils.h",
+    "IPCMessageUtilsSpecializations.h",
+]
+
+UNIFIED_SOURCES += [
+    "BackgroundImpl.cpp",
+    "BackgroundUtils.cpp",
+    "BigBuffer.cpp",
+    "BrowserProcessSubThread.cpp",
+    "CrashReporterClient.cpp",
+    "CrashReporterHost.cpp",
+    "DataPipe.cpp",
+    "Endpoint.cpp",
+    "FileDescriptor.cpp",
+    "FileDescriptorUtils.cpp",
+    "IdleSchedulerChild.cpp",
+    "IdleSchedulerParent.cpp",
+    "InputStreamUtils.cpp",
+    "IPCMessageUtilsSpecializations.cpp",
+    "IPCStreamUtils.cpp",
+    "LaunchError.cpp",
+    "LibrarySandboxPreload.cpp",
+    "MessageChannel.cpp",
+    "MessageLink.cpp",
+    "MessagePump.cpp",
+    "NodeChannel.cpp",
+    "NodeController.cpp",
+    "ProcessChild.cpp",
+    "ProcessUtils_common.cpp",
+    "ProtocolUtils.cpp",
+    "RandomAccessStreamUtils.cpp",
+    "RawShmem.cpp",
+    "ScopedPort.cpp",
+    "SerializedStructuredCloneBuffer.cpp",
+    "SharedMemory.cpp",
+    "Shmem.cpp",
+    "StringUtil.cpp",
+    "TransportSecurityInfoUtils.cpp",
+    "URIUtils.cpp",
+    "UtilityAudioDecoder.cpp",
+    "UtilityAudioDecoderChild.cpp",
+    "UtilityAudioDecoderParent.cpp",
+    "UtilityProcessChild.cpp",
+    "UtilityProcessHost.cpp",
+    "UtilityProcessImpl.cpp",
+    "UtilityProcessManager.cpp",
+    "UtilityProcessParent.cpp",
+]
+
+SOURCES += [
+    "BackgroundChildImpl.cpp",
+    "BackgroundParentImpl.cpp",
+]
+
+if CONFIG["OS_ARCH"] == "Darwin":
+    # GeckoChildProcessHost.cpp cannot be built unified due to OSX header
+    # clashes with TextRange.
+    SOURCES += [
+        "GeckoChildProcessHost.cpp",
+    ]
+else:
+    UNIFIED_SOURCES += [
+        "GeckoChildProcessHost.cpp",
+    ]
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    UNIFIED_SOURCES += ["MessagePump_windows.cpp"]
+elif CONFIG["OS_ARCH"] == "Darwin":
+    UNIFIED_SOURCES += ["MessagePump_mac.mm"]
+elif CONFIG["OS_TARGET"] == "Android":
+    UNIFIED_SOURCES += ["MessagePump_android.cpp"]
+
+LOCAL_INCLUDES += [
+    "/caps",
+    "/dom/broadcastchannel",
+    "/dom/indexedDB",
+    "/dom/storage",
+    "/netwerk/base",
+    "/third_party/libwebrtc",
+    "/third_party/libwebrtc/third_party/abseil-cpp",
+    "/tools/fuzzing/ipc",
+    "/xpcom/build",
+]
+
+PREPROCESSED_IPDL_SOURCES = [
+    "PUtilityAudioDecoder.ipdl",
+    "PUtilityProcess.ipdl",
+]
+
+IPDL_SOURCES = [
+    "InputStreamParams.ipdlh",
+    "IPCStream.ipdlh",
+    "PBackground.ipdl",
+    "PBackgroundSharedTypes.ipdlh",
+    "PBackgroundStarter.ipdl",
+    "PBackgroundTest.ipdl",
+    "PIdleScheduler.ipdl",
+    "ProtocolTypes.ipdlh",
+    "RandomAccessStreamParams.ipdlh",
+    "URIParams.ipdlh",
+]
+
+if CONFIG["MOZ_ENABLE_FORKSERVER"]:
+    EXPORTS.mozilla.ipc += [
+        "ForkServer.h",
+        "ForkServiceChild.h",
+        "MiniTransceiver.h",
+    ]
+    UNIFIED_SOURCES += [
+        "ForkServer.cpp",
+        "ForkServiceChild.cpp",
+        "MiniTransceiver.cpp",
+    ]
+    XPCOM_MANIFESTS += [
+        "components.conf",
+    ]
+
+LOCAL_INCLUDES += [
+    "/dom/ipc",
+    "/toolkit/crashreporter",
+    "/toolkit/xre",
+    "/xpcom/base",
+    "/xpcom/threads",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+if CONFIG["OS_ARCH"] == "Darwin":
+    OS_LIBS += ["bsm"]  # for audit_token_to_pid
+
+for var in ("MOZ_CHILD_PROCESS_NAME", "MOZ_CHILD_PROCESS_BUNDLE"):
+    DEFINES[var] = '"%s"' % CONFIG[var]
+
+if CONFIG["MOZ_SANDBOX"] and CONFIG["OS_ARCH"] == "WINNT":
+    LOCAL_INCLUDES += [
+        "/security/sandbox/chromium",
+        "/security/sandbox/chromium-shim",
+        "/security/sandbox/win/src/sandboxbroker",
+    ]
+
+if CONFIG["ENABLE_TESTS"]:
+    DIRS += [
+        "test/gtest",
+        "test/utility_process_xpcom",
+        "test/browser",
+    ]
+
+# Add libFuzzer configuration directives
+include("/tools/fuzzing/libfuzzer-config.mozbuild")
diff --git a/ipc/glue/nsIIPCSerializableInputStream.h b/ipc/glue/nsIIPCSerializableInputStream.h
new file mode 100644
index 0000000000..acc7594f66
--- /dev/null
+++ b/ipc/glue/nsIIPCSerializableInputStream.h
@@ -0,0 +1,104 @@
+/* -*- 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_ipc_nsIIPCSerializableInputStream_h
+#define mozilla_ipc_nsIIPCSerializableInputStream_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "nsISupports.h"
+#include "nsTArrayForwardDeclare.h"
+
+namespace mozilla {
+namespace ipc {
+
+class FileDescriptor;
+class InputStreamParams;
+
+}  // namespace ipc
+
+}  // namespace mozilla
+
+#define NS_IIPCSERIALIZABLEINPUTSTREAM_IID           \
+  {                                                  \
+    0xb0211b14, 0xea6d, 0x40d4, {                    \
+      0x87, 0xb5, 0x7b, 0xe3, 0xdf, 0xac, 0x09, 0xd1 \
+    }                                                \
+  }
+
+class NS_NO_VTABLE nsIIPCSerializableInputStream : public nsISupports {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_IIPCSERIALIZABLEINPUTSTREAM_IID)
+
+  // Determine the serialized complexity of this input stream, initializing
+  // `*aSizeUsed`, `*aPipes` and `*aTransferables` to the number of inline
+  // bytes/pipes/transferable resources which would be used. This will be used
+  // by other `Serialize` implementations to potentially simplify the resulting
+  // stream, reducing the number of pipes or file descriptors required.
+  //
+  // Each outparameter corresponds to a type of resource which will be included
+  // in the serialized message, as follows:
+  //
+  // *aSizeUsed:
+  //    Raw bytes to be included inline in the message's payload, usually in the
+  //    form of a nsCString for a StringInputStreamParams. This must be less
+  //    than or equal to `aMaxSize`. Larger payloads should instead be
+  //    serialized using SerializeInputStreamAsPipe.
+  // *aPipes:
+  //    New pipes, created using SerializeInputStreamAsPipe, which will be used
+  //    to asynchronously transfer part of the pipe over IPC. Callers such as
+  //    nsMultiplexInputStream may choose to serialize themselves as a DataPipe
+  //    if they contain DataPipes themselves, so existing DataPipe instances
+  //    which are cheaply transferred should be counted as transferrables.
+  // *aTransferables:
+  //    Existing objects which can be more cheaply transferred over IPC than by
+  //    serializing them inline in a payload or transferring them through a new
+  //    DataPipe. This includes RemoteLazyInputStreams, FileDescriptors, and
+  //    existing DataPipeReceiver instances.
+  //
+  // Callers of this method must have initialized all of `*aSizeUsed`,
+  // `*aPipes`, and `*aTransferables` to 0, so implementations are not required
+  // to initialize all outparameters. The outparameters must not be null.
+  virtual void SerializedComplexity(uint32_t aMaxSize, uint32_t* aSizeUsed,
+                                    uint32_t* aPipes,
+                                    uint32_t* aTransferables) = 0;
+
+  virtual void Serialize(mozilla::ipc::InputStreamParams& aParams,
+                         uint32_t aMaxSize, uint32_t* aSizeUsed) = 0;
+
+  virtual bool Deserialize(const mozilla::ipc::InputStreamParams& aParams) = 0;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsIIPCSerializableInputStream,
+                              NS_IIPCSERIALIZABLEINPUTSTREAM_IID)
+
+#define NS_DECL_NSIIPCSERIALIZABLEINPUTSTREAM                               \
+  virtual void SerializedComplexity(uint32_t aMaxSize, uint32_t* aSizeUsed, \
+                                    uint32_t* aPipes,                       \
+                                    uint32_t* aTransferrables) override;    \
+  virtual void Serialize(mozilla::ipc::InputStreamParams&, uint32_t,        \
+                         uint32_t*) override;                               \
+                                                                            \
+  virtual bool Deserialize(const mozilla::ipc::InputStreamParams&) override;
+
+#define NS_FORWARD_NSIIPCSERIALIZABLEINPUTSTREAM(_to)                       \
+  virtual void SerializedComplexity(uint32_t aMaxSize, uint32_t* aSizeUsed, \
+                                    uint32_t* aPipes,                       \
+                                    uint32_t* aTransferables) override {    \
+    _to SerializedComplexity(aMaxSize, aSizeUsed, aPipes, aTransferables);  \
+  };                                                                        \
+                                                                            \
+  virtual void Serialize(mozilla::ipc::InputStreamParams& aParams,          \
+                         uint32_t aMaxSize, uint32_t* aSizeUsed) override { \
+    _to Serialize(aParams, aMaxSize, aSizeUsed);                            \
+  }                                                                         \
+                                                                            \
+  virtual bool Deserialize(const mozilla::ipc::InputStreamParams& aParams)  \
+      override {                                                            \
+    return _to Deserialize(aParams);                                        \
+  }
+
+#endif  // mozilla_ipc_nsIIPCSerializableInputStream_h
diff --git a/ipc/glue/test/browser/browser.ini b/ipc/glue/test/browser/browser.ini
new file mode 100644
index 0000000000..9dc84c3914
--- /dev/null
+++ b/ipc/glue/test/browser/browser.ini
@@ -0,0 +1,59 @@
+[DEFAULT]
+support-files = head.js
+
+[browser_audio_telemetry_content.js]
+skip-if =
+  (os == 'win') # gfx blocks us because media.rdd-process.enabled=false disables PDMFactory::AllDecodersAreRemote()
+support-files =
+  head-telemetry.js
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+[browser_audio_telemetry_rdd.js]
+support-files =
+  head-telemetry.js
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+[browser_audio_telemetry_utility.js]
+support-files =
+  head-telemetry.js
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+[browser_utility_audioDecodeCrash.js]
+support-files =
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+skip-if =
+  !crashreporter
+  ccov
+[browser_utility_crashReporter.js]
+skip-if =
+  !crashreporter
+  ccov
+[browser_utility_geolocation_crashed.js]
+skip-if =
+  !(os == 'win' && os_version == '10.0')     # Geolocation is remoted only on Windows 8+
+  !crashreporter
+  ccov
+[browser_utility_hard_kill.js]
+[browser_utility_hard_kill_delayed.js] # bug 1754572: we really want hard_kill to be rust before hard_kill_delayed
+[browser_utility_memoryReport.js]
+skip-if = tsan # bug 1754554
+[browser_utility_multipleAudio.js]
+support-files =
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+[browser_utility_profiler.js]
+support-files =
+  ../../../../tools/profiler/tests/shared-head.js
+skip-if = tsan # from tools/profiler/tests/browser/browser.ini, timing out on profiler tests?
+[browser_utility_start_clean_shutdown.js]
diff --git a/ipc/glue/test/browser/browser_audio_shutdown.ini b/ipc/glue/test/browser/browser_audio_shutdown.ini
new file mode 100644
index 0000000000..a0ce9796f0
--- /dev/null
+++ b/ipc/glue/test/browser/browser_audio_shutdown.ini
@@ -0,0 +1,6 @@
+[DEFAULT]
+support-files = head.js
+
+[browser_utility_audio_shutdown.js]
+support-files =
+  ../../../../dom/media/test/small-shot.ogg
diff --git a/ipc/glue/test/browser/browser_audio_telemetry_content.js b/ipc/glue/test/browser/browser_audio_telemetry_content.js
new file mode 100644
index 0000000000..5d69175d5c
--- /dev/null
+++ b/ipc/glue/test/browser/browser_audio_telemetry_content.js
@@ -0,0 +1,32 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* import-globals-from head-telemetry.js */
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/ipc/glue/test/browser/head-telemetry.js",
+  this
+);
+
+add_setup(async function testNoTelemetry() {
+  await Telemetry.clearScalars();
+});
+
+add_task(async function testAudioDecodingInContent() {
+  await runTest({ expectUtility: false, expectRDD: false });
+});
+
+add_task(async function testUtilityTelemetry() {
+  const codecs = ["vorbis", "mp3", "aac", "flac"];
+  const extraKey = ",rdd-disabled,utility-disabled";
+  await verifyTelemetryForProcess("tab", codecs, extraKey);
+
+  const platform = Services.appinfo.OS;
+  for (let exp of utilityPerCodecs[platform]) {
+    await verifyNoTelemetryForProcess(exp.process, exp.codecs, extraKey);
+  }
+
+  await verifyNoTelemetryForProcess("rdd", codecs, extraKey);
+});
diff --git a/ipc/glue/test/browser/browser_audio_telemetry_rdd.js b/ipc/glue/test/browser/browser_audio_telemetry_rdd.js
new file mode 100644
index 0000000000..b4e41b562e
--- /dev/null
+++ b/ipc/glue/test/browser/browser_audio_telemetry_rdd.js
@@ -0,0 +1,29 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* import-globals-from head-telemetry.js */
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/ipc/glue/test/browser/head-telemetry.js",
+  this
+);
+
+add_setup(async function testNoTelemetry() {
+  await Telemetry.clearScalars();
+});
+
+add_task(async function testAudioDecodingInRDD() {
+  await runTest({ expectUtility: false, expectRDD: true });
+});
+
+add_task(async function testRDDTelemetry() {
+  const extraKey = ",utility-disabled";
+  const platform = Services.appinfo.OS;
+  for (let exp of utilityPerCodecs[platform]) {
+    await verifyNoTelemetryForProcess(exp.process, exp.codecs, extraKey);
+  }
+  const codecs = ["vorbis", "mp3", "aac", "flac"];
+  await verifyTelemetryForProcess("rdd", codecs, extraKey);
+});
diff --git a/ipc/glue/test/browser/browser_audio_telemetry_utility.js b/ipc/glue/test/browser/browser_audio_telemetry_utility.js
new file mode 100644
index 0000000000..07b492cc12
--- /dev/null
+++ b/ipc/glue/test/browser/browser_audio_telemetry_utility.js
@@ -0,0 +1,27 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* import-globals-from head-telemetry.js */
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/ipc/glue/test/browser/head-telemetry.js",
+  this
+);
+
+add_setup(async function testNoTelemetry() {
+  await Telemetry.clearScalars();
+});
+
+add_task(async function testAudioDecodingInUtility() {
+  await runTest({ expectUtility: true, expectRDD: true });
+});
+
+add_task(async function testUtilityTelemetry() {
+  const platform = Services.appinfo.OS;
+  for (let exp of utilityPerCodecs[platform]) {
+    await verifyTelemetryForProcess(exp.process, exp.codecs);
+  }
+  await verifyNoTelemetryForProcess("rdd", ["vorbis", "mp3", "aac", "flac"]);
+});
diff --git a/ipc/glue/test/browser/browser_child_hang.ini b/ipc/glue/test/browser/browser_child_hang.ini
new file mode 100644
index 0000000000..94931561b0
--- /dev/null
+++ b/ipc/glue/test/browser/browser_child_hang.ini
@@ -0,0 +1,7 @@
+# Any copyright is dedicated to the Public Domain.
+# http://creativecommons.org/publicdomain/zero/1.0/
+[DEFAULT]
+tags = ipc
+environment = MOZ_TEST_CHILD_EXIT_HANG=3
+
+[browser_child_hang.js]
diff --git a/ipc/glue/test/browser/browser_child_hang.js b/ipc/glue/test/browser/browser_child_hang.js
new file mode 100644
index 0000000000..cf890a6c61
--- /dev/null
+++ b/ipc/glue/test/browser/browser_child_hang.js
@@ -0,0 +1,37 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+//
+// Try to open a tab.  This provides code coverage for a few things,
+// although currently there's no automated functional test of correctness:
+//
+// * On opt builds, when the tab is closed and the process exits, it
+//   will hang for 3s and the parent will kill it after 2s.
+//
+// * On debug[*] builds, the parent process will wait until the
+//   process exits normally; but also, on browser shutdown, the
+//   preallocated content processes will block parent shutdown in
+//   WillDestroyCurrentMessageLoop.
+//
+// [*] Also sanitizer and code coverage builds.
+//
+
+add_task(async function () {
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: "https://example.com/",
+      forceNewProcess: true,
+    },
+    async function (browser) {
+      // browser.frameLoader.remoteTab.osPid is the child pid; once we
+      // have a way to get notifications about child process termination
+      // events, that could be useful.
+      ok(true, "Browser isn't broken");
+    }
+  );
+  // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+  await new Promise(resolve => setTimeout(resolve, 4000));
+  ok(true, "Still running after child process (hopefully) exited");
+});
diff --git a/ipc/glue/test/browser/browser_utility_audioDecodeCrash.js b/ipc/glue/test/browser/browser_utility_audioDecodeCrash.js
new file mode 100644
index 0000000000..1c7551c623
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_audioDecodeCrash.js
@@ -0,0 +1,95 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+async function getAudioDecoderPid(expectation) {
+  info("Finding a running AudioDecoder");
+
+  const actor = expectation.replace("Utility ", "");
+
+  let audioDecoderProcess = (await ChromeUtils.requestProcInfo()).children.find(
+    p =>
+      p.type === "utility" &&
+      p.utilityActors.find(a => a.actorName === `audioDecoder_${actor}`)
+  );
+  ok(
+    audioDecoderProcess,
+    `Found the AudioDecoder ${actor} process at ${audioDecoderProcess.pid}`
+  );
+  return audioDecoderProcess.pid;
+}
+
+async function crashDecoder(expectation) {
+  const audioPid = await getAudioDecoderPid(expectation);
+  ok(audioPid > 0, `Found an audio decoder ${audioPid}`);
+  const actorIsAudioDecoder = actorNames => {
+    return actorNames
+      .split(",")
+      .some(actorName => actorName.trim().startsWith("audio-decoder-"));
+  };
+  info(`Crashing audio decoder ${audioPid}`);
+  await crashSomeUtility(audioPid, actorIsAudioDecoder);
+}
+
+async function runTest(src, withClose, expectation) {
+  info(`Add media tabs: ${src}`);
+  let tab = await addMediaTab(src);
+
+  info("Play tab");
+  await play(tab, expectation.process, expectation.decoder);
+
+  info("Crash decoder");
+  await crashDecoder(expectation.process);
+
+  if (withClose) {
+    info("Stop tab");
+    await stop(tab);
+
+    info("Remove tab");
+    await BrowserTestUtils.removeTab(tab);
+
+    info("Create tab again");
+    tab = await addMediaTab(src);
+  }
+
+  info("Play tab again");
+  await play(tab, expectation.process, expectation.decoder);
+
+  info("Stop tab");
+  await stop(tab);
+
+  info("Remove tab");
+  await BrowserTestUtils.removeTab(tab);
+}
+
+add_setup(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["media.utility-process.enabled", true]],
+  });
+});
+
+async function testAudioCrash(withClose) {
+  info(`Running tests for audio decoder process crashing: ${withClose}`);
+
+  SimpleTest.expectChildProcessCrash();
+
+  const platform = Services.appinfo.OS;
+
+  for (let { src, expectations } of audioTestData()) {
+    if (!(platform in expectations)) {
+      info(`Skipping ${src} for ${platform}`);
+      continue;
+    }
+
+    await runTest(src, withClose, expectations[platform]);
+  }
+}
+
+add_task(async function testAudioCrashSimple() {
+  await testAudioCrash(false);
+});
+
+add_task(async function testAudioCrashClose() {
+  await testAudioCrash(true);
+});
diff --git a/ipc/glue/test/browser/browser_utility_audio_shutdown.js b/ipc/glue/test/browser/browser_utility_audio_shutdown.js
new file mode 100644
index 0000000000..31811cfd55
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_audio_shutdown.js
@@ -0,0 +1,76 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// The purpose of that test is to reproduce edge case behaviors that one can
+// have while running whole ipc/glue/test/browser/ suite but that could this
+// way be intermittent and hard to diagnose. By having such a test we make sure
+// it is cleanly reproduced and wont regress somewhat silently.
+
+"use strict";
+
+async function runTest(src, process, decoder) {
+  info(`Add media tabs: ${src}`);
+  let tab = await addMediaTab(src);
+
+  info("Play tab");
+  await play(tab, process, decoder);
+
+  info("Stop tab");
+  await stop(tab);
+
+  info("Remove tab");
+  await BrowserTestUtils.removeTab(tab);
+}
+
+async function findGenericAudioDecoder() {
+  const audioDecoders = (await ChromeUtils.requestProcInfo()).children.filter(
+    p => {
+      return (
+        p.type === "utility" &&
+        p.utilityActors.find(a => a.actorName === "audioDecoder_Generic")
+      );
+    }
+  );
+  ok(audioDecoders.length === 1, "Only one audio decoder present");
+  return audioDecoders[0].pid;
+}
+
+add_setup(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["media.utility-process.enabled", true]],
+  });
+});
+
+add_task(async function testKill() {
+  await runTest("small-shot.ogg", "Utility Generic", "vorbis audio decoder");
+
+  await cleanUtilityProcessShutdown(
+    "audioDecoder_Generic",
+    true /* preferKill */
+  );
+
+  info("Waiting 15s to trigger mShutdownBlockers assertions");
+  await new Promise((resolve, reject) => {
+    /* eslint-disable mozilla/no-arbitrary-setTimeout */
+    setTimeout(resolve, 15 * 1000);
+  });
+
+  ok(true, "Waited 15s to trigger mShutdownBlockers assertions: over");
+});
+
+add_task(async function testShutdown() {
+  await runTest("small-shot.ogg", "Utility Generic", "vorbis audio decoder");
+
+  const audioDecoderPid = await findGenericAudioDecoder();
+  ok(audioDecoderPid > 0, `Valid PID found: ${audioDecoderPid}`);
+
+  await cleanUtilityProcessShutdown("audioDecoder_Generic");
+
+  info("Waiting 15s to trigger mShutdownBlockers assertions");
+  await new Promise((resolve, reject) => {
+    /* eslint-disable mozilla/no-arbitrary-setTimeout */
+    setTimeout(resolve, 15 * 1000);
+  });
+
+  ok(true, "Waited 15s to trigger mShutdownBlockers assertions: over");
+});
diff --git a/ipc/glue/test/browser/browser_utility_crashReporter.js b/ipc/glue/test/browser/browser_utility_crashReporter.js
new file mode 100644
index 0000000000..73e6c6355a
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_crashReporter.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+async function startAndCrashUtility(numUnknownActors, actorsCheck) {
+  const actors = Array(numUnknownActors).fill("unknown");
+  const utilityPid = await startUtilityProcess(actors);
+  await crashSomeUtility(utilityPid, actorsCheck);
+}
+
+// When running full suite, previous tests may have left some utility
+// processes running and this might interfere with our testing.
+add_setup(async function ensureNoExistingProcess() {
+  await killUtilityProcesses();
+});
+
+add_task(async function utilityNoActor() {
+  await startAndCrashUtility(0, actorNames => {
+    return actorNames === undefined;
+  });
+});
+
+add_task(async function utilityOneActor() {
+  await startAndCrashUtility(1, actorNames => {
+    return actorNames === kGenericUtilityActor;
+  });
+});
+
+add_task(async function utilityManyActors() {
+  await startAndCrashUtility(42, actorNames => {
+    return actorNames === Array(42).fill("unknown").join(", ");
+  });
+});
diff --git a/ipc/glue/test/browser/browser_utility_geolocation_crashed.js b/ipc/glue/test/browser/browser_utility_geolocation_crashed.js
new file mode 100644
index 0000000000..b0c341b69f
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_geolocation_crashed.js
@@ -0,0 +1,70 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+async function getGeolocation() {
+  info("Requesting geolocation");
+
+  let resolve;
+  let promise = new Promise((_resolve, _reject) => {
+    resolve = _resolve;
+  });
+
+  navigator.geolocation.getCurrentPosition(
+    () => {
+      ok(true, "geolocation succeeded");
+      resolve(undefined);
+    },
+    () => {
+      ok(false, "geolocation failed");
+      resolve(undefined);
+    }
+  );
+
+  return promise;
+}
+
+add_setup(async function () {
+  // Avoid the permission doorhanger and cache that would trigger instead
+  // of re-requesting location. Setting geo.timeout to 0 causes it to
+  // retry the system geolocation (incl. recreating the utility process)
+  // instead of reusing the MLS geolocation fallback it found the first time.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["geo.prompt.testing", true],
+      ["geo.prompt.testing.allow", true],
+      ["geo.provider.network.debug.requestCache.enabled", false],
+      ["geo.provider.testing", false],
+      ["geo.timeout", 0],
+    ],
+  });
+});
+
+add_task(async function testGeolocationProcessCrash() {
+  info("Start the Windows utility process");
+  await getGeolocation();
+
+  info("Crash the utility process");
+  await crashSomeUtilityActor("windowsUtils");
+
+  info("Restart the Windows utility process");
+  await getGeolocation();
+
+  info("Confirm the restarted process");
+  await checkUtilityExists("windowsUtils");
+
+  info("Kill the utility process");
+  await cleanUtilityProcessShutdown("windowsUtils", true);
+
+  info("Restart the Windows utility process again");
+  await getGeolocation();
+
+  info("Confirm the restarted process");
+  await checkUtilityExists("windowsUtils");
+});
+
+add_task(async function testCleanup() {
+  info("Clean up to avoid confusing future tests");
+  await cleanUtilityProcessShutdown("windowsUtils", true);
+});
diff --git a/ipc/glue/test/browser/browser_utility_hard_kill.js b/ipc/glue/test/browser/browser_utility_hard_kill.js
new file mode 100644
index 0000000000..516ef64045
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_hard_kill.js
@@ -0,0 +1,13 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  await startUtilityProcess(["unknown"]);
+
+  SimpleTest.expectChildProcessCrash();
+
+  info("Hard kill Utility Process");
+  await cleanUtilityProcessShutdown("unknown", true /* preferKill */);
+});
diff --git a/ipc/glue/test/browser/browser_utility_hard_kill_delayed.js b/ipc/glue/test/browser/browser_utility_hard_kill_delayed.js
new file mode 100644
index 0000000000..ffda4d3988
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_hard_kill_delayed.js
@@ -0,0 +1,57 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  const utilityPid = await startUtilityProcess();
+
+  SimpleTest.expectChildProcessCrash();
+
+  const utilityProcessGone = TestUtils.topicObserved("ipc:utility-shutdown");
+
+  info("Hard kill Utility Process");
+  const ProcessTools = Cc["@mozilla.org/processtools-service;1"].getService(
+    Ci.nsIProcessToolsService
+  );
+
+  // Here we really want to exercise the fact that kill() might not be done
+  // right now but a bit later, and we should wait for the process to be dead
+  // before considering the test is finished.
+  //
+  // Without this, we get into bug 1754572 (where there was no setTimeout nor
+  // the wait) where the kill() operation ends up really killing the child a
+  // bit after the current test has been finished ; unfortunately, this happened
+  // right after the next test, browser_utility_memoryReport.js did start and
+  // even worse, after it thought it had started a new utility process. We were
+  // in fact re-using the one we started here, and when we wanted to query its
+  // pid in the browser_utility_memoryReport.js then the kill() happened, so
+  // no more process and the test intermittently failed.
+  //
+  // The timeout value of 50ms should be long enough to allow the test to finish
+  // and the next one to start and get a reference on the process we launched,
+  // and yet allow us to kill the process in the middle of the next test. Higher
+  // values would allow browser_utility_memoryReport.js to complete without
+  // reproducing the issue (both locally and on try).
+  //
+  // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+  setTimeout(() => {
+    ProcessTools.kill(utilityPid);
+  }, 50);
+
+  info(`Waiting for utility process ${utilityPid} to go away.`);
+  let [subject, data] = await utilityProcessGone;
+  ok(
+    subject instanceof Ci.nsIPropertyBag2,
+    "Subject needs to be a nsIPropertyBag2 to clean up properly"
+  );
+  is(
+    parseInt(data, 10),
+    utilityPid,
+    `Should match the crashed PID ${utilityPid} with ${data}`
+  );
+
+  // Make sure the process is dead, otherwise there is a risk of race for
+  // writing leak logs
+  utilityProcessTest().noteIntentionalCrash(utilityPid);
+});
diff --git a/ipc/glue/test/browser/browser_utility_memoryReport.js b/ipc/glue/test/browser/browser_utility_memoryReport.js
new file mode 100644
index 0000000000..8cec61b8be
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_memoryReport.js
@@ -0,0 +1,76 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// When running full suite, previous audio decoding tests might have left some
+// running and this might interfere with our testing
+add_setup(async function ensureNoExistingProcess() {
+  await killUtilityProcesses();
+});
+
+add_task(async () => {
+  const utilityPid = await startUtilityProcess();
+
+  const gMgr = Cc["@mozilla.org/memory-reporter-manager;1"].getService(
+    Ci.nsIMemoryReporterManager
+  );
+  ok(utilityPid !== undefined, `Utility process is running as ${utilityPid}`);
+
+  var utilityReports = [];
+
+  const performCollection = new Promise((resolve, reject) => {
+    // Record the reports from the live memory reporters then process them.
+    let handleReport = function (
+      aProcess,
+      aUnsafePath,
+      aKind,
+      aUnits,
+      aAmount,
+      aDescription
+    ) {
+      const expectedProcess = `Utility (pid ${utilityPid}, sandboxingKind ${kGenericUtilitySandbox})`;
+      if (aProcess !== expectedProcess) {
+        return;
+      }
+
+      let report = {
+        process: aProcess,
+        path: aUnsafePath,
+        kind: aKind,
+        units: aUnits,
+        amount: aAmount,
+        description: aDescription,
+      };
+
+      utilityReports.push(report);
+    };
+
+    info("Memory report: Perform the call");
+    gMgr.getReports(handleReport, null, resolve, null, false);
+  });
+
+  await performCollection;
+
+  info(
+    `Collected ${utilityReports.length} reports from utility process ${utilityPid}`
+  );
+  ok(!!utilityReports.length, "Collected some reports");
+  ok(
+    utilityReports.filter(r => r.path === "vsize" && r.amount > 0).length === 1,
+    "Collected vsize report"
+  );
+  ok(
+    utilityReports.filter(r => r.path === "resident" && r.amount > 0).length ===
+      1,
+    "Collected resident report"
+  );
+  ok(
+    !!utilityReports.filter(
+      r => r.path.search(/^explicit\/.*/) >= 0 && r.amount > 0
+    ).length,
+    "Collected some explicit/ report"
+  );
+
+  await cleanUtilityProcessShutdown();
+});
diff --git a/ipc/glue/test/browser/browser_utility_multipleAudio.js b/ipc/glue/test/browser/browser_utility_multipleAudio.js
new file mode 100644
index 0000000000..d88ee014e2
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_multipleAudio.js
@@ -0,0 +1,73 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+async function runTest(expectUtility) {
+  info(
+    `Running tests with decoding from Utility or RDD: expectUtility=${expectUtility}`
+  );
+
+  // Utility should now be the default, so dont toggle the pref unless we test
+  // RDD
+  if (!expectUtility) {
+    await SpecialPowers.pushPrefEnv({
+      set: [["media.utility-process.enabled", expectUtility]],
+    });
+  }
+
+  const platform = Services.appinfo.OS;
+
+  for (let { src, expectations } of audioTestData()) {
+    if (!(platform in expectations)) {
+      info(`Skipping ${src} for ${platform}`);
+      continue;
+    }
+
+    const expectation = expectations[platform];
+
+    info(`Add media tabs: ${src}`);
+    let tabs = [await addMediaTab(src), await addMediaTab(src)];
+    let playback = [];
+
+    info("Play tabs");
+    for (let tab of tabs) {
+      playback.push(
+        play(
+          tab,
+          expectUtility ? expectation.process : "RDD",
+          expectation.decoder
+        )
+      );
+    }
+
+    info("Wait all playback");
+    await Promise.all(playback);
+
+    let allstop = [];
+    info("Stop tabs");
+    for (let tab of tabs) {
+      allstop.push(stop(tab));
+    }
+
+    info("Wait all stop");
+    await Promise.all(allstop);
+
+    let remove = [];
+    info("Remove tabs");
+    for (let tab of tabs) {
+      remove.push(BrowserTestUtils.removeTab(tab));
+    }
+
+    info("Wait all tabs to be removed");
+    await Promise.all(remove);
+  }
+}
+
+add_task(async function testAudioDecodingInUtility() {
+  await runTest(true);
+});
+
+add_task(async function testAudioDecodingInRDD() {
+  await runTest(false);
+});
diff --git a/ipc/glue/test/browser/browser_utility_profiler.js b/ipc/glue/test/browser/browser_utility_profiler.js
new file mode 100644
index 0000000000..084cd67747
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_profiler.js
@@ -0,0 +1,76 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* import-globals-from /tools/profiler/tests/shared-head.js */
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochitests/content/browser/tools/profiler/tests/browser/shared-head.js",
+  this
+);
+
+// When running full suite, previous tests may have left some utility
+// processes running and this might interfere with our testing.
+add_setup(async function ensureNoExistingProcess() {
+  await killUtilityProcesses();
+});
+
+add_task(async () => {
+  const utilityPid = await startUtilityProcess();
+
+  info("Start the profiler");
+  await startProfiler();
+
+  let profile;
+  await TestUtils.waitForCondition(async () => {
+    profile = await Services.profiler.getProfileDataAsync();
+    return (
+      // Search for process name to not be disturbed by other types of utility
+      // e.g. Utility AudioDecoder
+      profile.processes.filter(
+        ps => ps.threads[0].processName === "Utility Process"
+      ).length === 1
+    );
+  }, "Give time for the profiler to start and collect some samples");
+
+  info(`Check that the utility process ${utilityPid} is present.`);
+  let utilityProcessIndex = profile.processes.findIndex(
+    p => p.threads[0].pid == utilityPid
+  );
+  Assert.notEqual(utilityProcessIndex, -1, "Could find index of utility");
+
+  Assert.equal(
+    profile.processes[utilityProcessIndex].threads[0].processType,
+    "utility",
+    "Profile has processType utility"
+  );
+
+  Assert.equal(
+    profile.processes[utilityProcessIndex].threads[0].name,
+    "GeckoMain",
+    "Profile has correct main thread name"
+  );
+
+  Assert.equal(
+    profile.processes[utilityProcessIndex].threads[0].processName,
+    "Utility Process",
+    "Profile has correct process name"
+  );
+
+  Assert.greater(
+    profile.processes[utilityProcessIndex].threads.length,
+    0,
+    "The utility process should have threads"
+  );
+
+  Assert.equal(
+    profile.threads.length,
+    1,
+    "The parent process should have only one thread"
+  );
+
+  Services.profiler.StopProfiler();
+
+  await cleanUtilityProcessShutdown();
+});
diff --git a/ipc/glue/test/browser/browser_utility_start_clean_shutdown.js b/ipc/glue/test/browser/browser_utility_start_clean_shutdown.js
new file mode 100644
index 0000000000..62a9e4065b
--- /dev/null
+++ b/ipc/glue/test/browser/browser_utility_start_clean_shutdown.js
@@ -0,0 +1,9 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  await startUtilityProcess();
+  await cleanUtilityProcessShutdown();
+});
diff --git a/ipc/glue/test/browser/head-telemetry.js b/ipc/glue/test/browser/head-telemetry.js
new file mode 100644
index 0000000000..64a6aee1c4
--- /dev/null
+++ b/ipc/glue/test/browser/head-telemetry.js
@@ -0,0 +1,205 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* import-globals-from head.js */
+
+const Telemetry = Services.telemetry;
+
+const { TelemetryController } = ChromeUtils.importESModule(
+  "resource://gre/modules/TelemetryController.sys.mjs"
+);
+
+/* eslint-disable mozilla/no-redeclare-with-import-autofix */
+const { ContentTaskUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/ContentTaskUtils.sys.mjs"
+);
+
+const MEDIA_AUDIO_PROCESS = "media.audio_process_per_codec_name";
+
+const utilityPerCodecs = {
+  Linux: [
+    {
+      process: "utility+audioDecoder_Generic",
+      codecs: ["vorbis", "mp3", "aac", "flac"],
+    },
+  ],
+  WINNT: [
+    {
+      process: "utility+audioDecoder_Generic",
+      codecs: ["vorbis", "mp3", "flac"],
+    },
+    {
+      process: "utility+audioDecoder_WMF",
+      codecs: ["aac"],
+    },
+  ],
+  Darwin: [
+    {
+      process: "utility+audioDecoder_Generic",
+      codecs: ["vorbis", "mp3", "flac"],
+    },
+    {
+      process: "utility+audioDecoder_AppleMedia",
+      codecs: ["aac"],
+    },
+  ],
+};
+
+const kInterval = 300; /* ms */
+const kRetries = 5;
+
+/**
+ * This function waits until utility scalars are reported into the
+ * scalar snapshot.
+ */
+async function waitForKeyedScalars(process) {
+  await ContentTaskUtils.waitForCondition(
+    () => {
+      const scalars = Telemetry.getSnapshotForKeyedScalars("main", false);
+      return Object.keys(scalars).includes("content");
+    },
+    `Waiting for ${process} scalars to have been set`,
+    kInterval,
+    kRetries
+  );
+}
+
+async function waitForValue(process, codecNames, extra = "") {
+  await ContentTaskUtils.waitForCondition(
+    () => {
+      const telemetry = Telemetry.getSnapshotForKeyedScalars(
+        "main",
+        false
+      ).content;
+      if (telemetry && MEDIA_AUDIO_PROCESS in telemetry) {
+        const keyProcMimeTypes = Object.keys(telemetry[MEDIA_AUDIO_PROCESS]);
+        const found = codecNames.every(item =>
+          keyProcMimeTypes.includes(`${process},${item}${extra}`)
+        );
+        return found;
+      }
+      return false;
+    },
+    `Waiting for ${MEDIA_AUDIO_PROCESS}`,
+    kInterval,
+    kRetries
+  );
+}
+
+async function runTest({ expectUtility = false, expectRDD = false }) {
+  info(
+    `Running tests with decoding from Utility or RDD: expectUtility=${expectUtility} expectRDD=${expectRDD}`
+  );
+
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["media.utility-process.enabled", expectUtility],
+      ["media.rdd-process.enabled", expectRDD],
+      ["toolkit.telemetry.ipcBatchTimeout", 0],
+    ],
+  });
+
+  const platform = Services.appinfo.OS;
+
+  for (let { src, expectations } of audioTestData()) {
+    if (!(platform in expectations)) {
+      info(`Skipping ${src} for ${platform}`);
+      continue;
+    }
+
+    const expectation = expectations[platform];
+
+    info(`Add media tab: ${src}`);
+    let tab = await addMediaTab(src);
+
+    info("Play tab");
+    await play(
+      tab,
+      expectUtility ? expectation.process : "RDD",
+      expectation.decoder,
+      !expectUtility && !expectRDD
+    );
+
+    info("Stop tab");
+    await stop(tab);
+
+    info("Remove tab");
+    await BrowserTestUtils.removeTab(tab);
+  }
+}
+
+function getTelemetry() {
+  const telemetry = Telemetry.getSnapshotForKeyedScalars("main", false).content;
+  return telemetry;
+}
+
+async function verifyTelemetryForProcess(process, codecNames, extraKey = "") {
+  // Once scalars are set by the utility process, they don't immediately get
+  // sent to the parent process. Wait for the Telemetry IPC Timer to trigger
+  // and batch send the data back to the parent process.
+  await waitForKeyedScalars(process);
+  await waitForValue(process, codecNames, extraKey);
+
+  const telemetry = getTelemetry();
+
+  // The amount here depends on how many times RemoteAudioDecoderParent::RemoteAudioDecoderParent
+  // gets called, which might be more than actual audio files being playback, e.g., we would get one for metadata loading, then one for playback etc.
+  // But we dont care really we just want to ensure 0 on RDD, Content and others
+  // in the wild.[${codecName}]
+  codecNames.forEach(codecName => {
+    Assert.equal(
+      telemetry[MEDIA_AUDIO_PROCESS][`${process},${codecName}${extraKey}`],
+      1,
+      `${MEDIA_AUDIO_PROCESS} must have the correct value (${process}, ${codecName}).`
+    );
+  });
+}
+
+async function verifyNoTelemetryForProcess(process, codecNames, extraKey = "") {
+  try {
+    await waitForKeyedScalars(process);
+    await waitForValue(process, codecNames, extraKey);
+  } catch (ex) {
+    if (ex.indexOf("timed out after") > 0) {
+      Assert.ok(
+        true,
+        `Expected timeout ${process}[${MEDIA_AUDIO_PROCESS}] for ${codecNames}`
+      );
+    } else {
+      Assert.ok(
+        false,
+        `Unexpected exception on ${process}[${MEDIA_AUDIO_PROCESS}] for ${codecNames}: ${ex}`
+      );
+    }
+  }
+
+  const telemetry = getTelemetry();
+
+  // There could be races with telemetry for power usage coming up
+  codecNames.forEach(codecName => {
+    if (telemetry) {
+      if (telemetry && MEDIA_AUDIO_PROCESS in telemetry) {
+        Assert.ok(
+          !(
+            `${process},${codecName}${extraKey}` in
+            telemetry[MEDIA_AUDIO_PROCESS]
+          ),
+          `Some telemetry but no ${process}[${MEDIA_AUDIO_PROCESS}][${codecName}]`
+        );
+      } else {
+        Assert.ok(
+          !(MEDIA_AUDIO_PROCESS in telemetry),
+          `No telemetry for ${process}[${MEDIA_AUDIO_PROCESS}][${codecName}]`
+        );
+      }
+    } else {
+      Assert.equal(
+        undefined,
+        telemetry,
+        `No telemetry for ${process}[${MEDIA_AUDIO_PROCESS}][${codecName}]`
+      );
+    }
+  });
+}
diff --git a/ipc/glue/test/browser/head.js b/ipc/glue/test/browser/head.js
new file mode 100644
index 0000000000..14c0859eb3
--- /dev/null
+++ b/ipc/glue/test/browser/head.js
@@ -0,0 +1,424 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const utilityProcessTest = () => {
+  return Cc["@mozilla.org/utility-process-test;1"].createInstance(
+    Ci.nsIUtilityProcessTest
+  );
+};
+
+const kGenericUtilitySandbox = 0;
+const kGenericUtilityActor = "unknown";
+
+// Start a generic utility process with the given array of utility actor names
+// registered.
+async function startUtilityProcess(actors = []) {
+  info("Start a UtilityProcess");
+  return utilityProcessTest().startProcess(actors);
+}
+
+// Returns an array of process infos for utility processes of the given type
+// or all utility processes if actor is not defined.
+async function getUtilityProcesses(actor = undefined) {
+  let procInfos = (await ChromeUtils.requestProcInfo()).children.filter(p => {
+    return (
+      p.type === "utility" &&
+      (actor == undefined ||
+        p.utilityActors.find(a => a.actorName.startsWith(actor)))
+    );
+  });
+
+  info(`Utility process infos = ${JSON.stringify(procInfos)}`);
+  return procInfos;
+}
+
+async function getUtilityPid(actor) {
+  let process = await getUtilityProcesses(actor);
+  is(process.length, 1, `exactly one ${actor} process exists`);
+  return process[0].pid;
+}
+
+async function checkUtilityExists(actor) {
+  info(`Looking for a running ${actor} utility process`);
+  const utilityPid = await getUtilityPid(actor);
+  ok(utilityPid > 0, `Found ${actor} utility process ${utilityPid}`);
+  return utilityPid;
+}
+
+// "Cleanly stop" a utility process.  This will never leave a crash dump file.
+// preferKill will "kill" the process (e.g. SIGABRT) instead of using the
+// UtilityProcessManager.
+// To "crash" -- i.e. shutdown and generate a crash dump -- use
+// crashSomeUtility().
+async function cleanUtilityProcessShutdown(actor, preferKill = false) {
+  info(`${preferKill ? "Kill" : "Clean shutdown"} Utility Process ${actor}`);
+
+  const utilityPid = await getUtilityPid(actor);
+  ok(utilityPid !== undefined, `Must have PID for ${actor} utility process`);
+
+  const utilityProcessGone = TestUtils.topicObserved(
+    "ipc:utility-shutdown",
+    (subject, data) => parseInt(data, 10) === utilityPid
+  );
+
+  if (preferKill) {
+    SimpleTest.expectChildProcessCrash();
+    info(`Kill Utility Process ${utilityPid}`);
+    const ProcessTools = Cc["@mozilla.org/processtools-service;1"].getService(
+      Ci.nsIProcessToolsService
+    );
+    ProcessTools.kill(utilityPid);
+  } else {
+    info(`Stopping Utility Process ${utilityPid}`);
+    await utilityProcessTest().stopProcess(actor);
+  }
+
+  let [subject, data] = await utilityProcessGone;
+  ok(
+    subject instanceof Ci.nsIPropertyBag2,
+    "Subject needs to be a nsIPropertyBag2 to clean up properly"
+  );
+  is(
+    parseInt(data, 10),
+    utilityPid,
+    `Should match the crashed PID ${utilityPid} with ${data}`
+  );
+
+  // Make sure the process is dead, otherwise there is a risk of race for
+  // writing leak logs
+  utilityProcessTest().noteIntentionalCrash(utilityPid);
+
+  ok(!subject.hasKey("dumpID"), "There should be no dumpID");
+}
+
+async function killUtilityProcesses() {
+  let utilityProcesses = await getUtilityProcesses();
+  for (const utilityProcess of utilityProcesses) {
+    for (const actor of utilityProcess.utilityActors) {
+      info(`Stopping ${actor.actorName} utility process`);
+      await cleanUtilityProcessShutdown(actor.actorName, /* preferKill */ true);
+    }
+  }
+}
+
+function audioTestData() {
+  return [
+    {
+      src: "small-shot.ogg",
+      expectations: {
+        Android: {
+          process: "Utility Generic",
+          decoder: "vorbis audio decoder",
+        },
+        Linux: {
+          process: "Utility Generic",
+          decoder: "vorbis audio decoder",
+        },
+        WINNT: {
+          process: "Utility Generic",
+          decoder: "vorbis audio decoder",
+        },
+        Darwin: {
+          process: "Utility Generic",
+          decoder: "vorbis audio decoder",
+        },
+      },
+    },
+    {
+      src: "small-shot.mp3",
+      expectations: {
+        Android: { process: "Utility Generic", decoder: "ffvpx audio decoder" },
+        Linux: {
+          process: "Utility Generic",
+          decoder: "ffvpx audio decoder",
+        },
+        WINNT: {
+          process: SpecialPowers.getBoolPref("media.ffvpx.mp3.enabled")
+            ? "Utility Generic"
+            : "Utility WMF",
+          decoder: SpecialPowers.getBoolPref("media.ffvpx.mp3.enabled")
+            ? "ffvpx audio decoder"
+            : "wmf audio decoder",
+        },
+        Darwin: {
+          process: SpecialPowers.getBoolPref("media.ffvpx.mp3.enabled")
+            ? "Utility Generic"
+            : "Utility AppleMedia",
+          decoder: SpecialPowers.getBoolPref("media.ffvpx.mp3.enabled")
+            ? "ffvpx audio decoder"
+            : "apple coremedia decoder",
+        },
+      },
+    },
+    {
+      src: "small-shot.m4a",
+      expectations: {
+        // Add Android after Bug 1771196
+        Linux: {
+          process: "Utility Generic",
+          decoder: "ffmpeg audio decoder",
+        },
+        WINNT: {
+          process: "Utility WMF",
+          decoder: "wmf audio decoder",
+        },
+        Darwin: {
+          process: "Utility AppleMedia",
+          decoder: "apple coremedia decoder",
+        },
+      },
+    },
+    {
+      src: "small-shot.flac",
+      expectations: {
+        Android: { process: "Utility Generic", decoder: "ffvpx audio decoder" },
+        Linux: {
+          process: "Utility Generic",
+          decoder: "ffvpx audio decoder",
+        },
+        WINNT: {
+          process: "Utility Generic",
+          decoder: "ffvpx audio decoder",
+        },
+        Darwin: {
+          process: "Utility Generic",
+          decoder: "ffvpx audio decoder",
+        },
+      },
+    },
+  ];
+}
+
+async function addMediaTab(src) {
+  const tab = BrowserTestUtils.addTab(gBrowser, "about:blank", {
+    forceNewProcess: true,
+  });
+  const browser = gBrowser.getBrowserForTab(tab);
+  await BrowserTestUtils.browserLoaded(browser);
+  await SpecialPowers.spawn(browser, [src], createAudioElement);
+  return tab;
+}
+
+async function play(
+  tab,
+  expectUtility,
+  expectDecoder,
+  expectContent = false,
+  expectJava = false
+) {
+  let browser = tab.linkedBrowser;
+  return SpecialPowers.spawn(
+    browser,
+    [expectUtility, expectDecoder, expectContent, expectJava],
+    checkAudioDecoder
+  );
+}
+
+async function stop(tab) {
+  let browser = tab.linkedBrowser;
+  await SpecialPowers.spawn(browser, [], async function () {
+    let audio = content.document.querySelector("audio");
+    audio.pause();
+  });
+}
+
+async function createAudioElement(src) {
+  const doc = typeof content !== "undefined" ? content.document : document;
+  const ROOT = "https://example.com/browser/ipc/glue/test/browser";
+  let audio = doc.createElement("audio");
+  audio.setAttribute("controls", "true");
+  audio.setAttribute("loop", true);
+  audio.src = `${ROOT}/${src}`;
+  doc.body.appendChild(audio);
+}
+
+async function checkAudioDecoder(
+  expectedProcess,
+  expectedDecoder,
+  expectContent = false,
+  expectJava = false
+) {
+  const doc = typeof content !== "undefined" ? content.document : document;
+  let audio = doc.querySelector("audio");
+  const checkPromise = new Promise((resolve, reject) => {
+    const timeUpdateHandler = async ev => {
+      const debugInfo = await SpecialPowers.wrap(audio).mozRequestDebugInfo();
+      const audioDecoderName = debugInfo.decoder.reader.audioDecoderName;
+
+      const isExpectedDecoder =
+        audioDecoderName.indexOf(`${expectedDecoder}`) == 0;
+      ok(
+        isExpectedDecoder,
+        `playback ${audio.src} was from decoder '${audioDecoderName}', expected '${expectedDecoder}'`
+      );
+
+      const isExpectedProcess =
+        audioDecoderName.indexOf(`(${expectedProcess} remote)`) > 0;
+      const isJavaRemote = audioDecoderName.indexOf("(remote)") > 0;
+      const isOk =
+        (isExpectedProcess && !isJavaRemote && !expectContent && !expectJava) || // Running in Utility/RDD
+        (expectJava && !isExpectedProcess && isJavaRemote) || // Running in Java remote
+        (expectContent && !isExpectedProcess && !isJavaRemote); // Running in Content
+
+      ok(
+        isOk,
+        `playback ${audio.src} was from process '${audioDecoderName}', expected '${expectedProcess}'`
+      );
+
+      if (isOk) {
+        resolve();
+      } else {
+        reject();
+      }
+    };
+
+    const startPlaybackHandler = async ev => {
+      ok(
+        await audio.play().then(
+          _ => true,
+          _ => false
+        ),
+        "audio started playing"
+      );
+
+      audio.addEventListener("timeupdate", timeUpdateHandler, { once: true });
+    };
+
+    audio.addEventListener("canplaythrough", startPlaybackHandler, {
+      once: true,
+    });
+  });
+
+  // We need to make sure the decoder is ready before play()ing otherwise we
+  // could get into bad situations
+  audio.load();
+  return checkPromise;
+}
+
+async function runMochitestUtilityAudio(
+  src,
+  {
+    expectUtility,
+    expectDecoder,
+    expectContent = false,
+    expectJava = false,
+  } = {}
+) {
+  info(`Add media: ${src}`);
+  await createAudioElement(src);
+  let audio = document.querySelector("audio");
+  ok(audio, "Found an audio element created");
+
+  info(`Play media: ${src}`);
+  await checkAudioDecoder(
+    expectUtility,
+    expectDecoder,
+    expectContent,
+    expectJava
+  );
+
+  info(`Pause media: ${src}`);
+  await audio.pause();
+
+  info(`Remove media: ${src}`);
+  document.body.removeChild(audio);
+}
+
+async function crashSomeUtility(utilityPid, actorsCheck) {
+  SimpleTest.expectChildProcessCrash();
+
+  const crashMan = Services.crashmanager;
+  const utilityProcessGone = TestUtils.topicObserved(
+    "ipc:utility-shutdown",
+    (subject, data) => {
+      info(`ipc:utility-shutdown: data=${data} subject=${subject}`);
+      return parseInt(data, 10) === utilityPid;
+    }
+  );
+
+  info("prune any previous crashes");
+  const future = new Date(Date.now() + 1000 * 60 * 60 * 24);
+  await crashMan.pruneOldCrashes(future);
+
+  info("crash Utility Process");
+  const ProcessTools = Cc["@mozilla.org/processtools-service;1"].getService(
+    Ci.nsIProcessToolsService
+  );
+
+  info(`Crash Utility Process ${utilityPid}`);
+  ProcessTools.crash(utilityPid);
+
+  info(`Waiting for utility process ${utilityPid} to go away.`);
+  let [subject, data] = await utilityProcessGone;
+  ok(
+    parseInt(data, 10) === utilityPid,
+    `Should match the crashed PID ${utilityPid} with ${data}`
+  );
+  ok(
+    subject instanceof Ci.nsIPropertyBag2,
+    "Subject needs to be a nsIPropertyBag2 to clean up properly"
+  );
+
+  // Make sure the process is dead, otherwise there is a risk of race for
+  // writing leak logs
+  utilityProcessTest().noteIntentionalCrash(utilityPid);
+
+  const dumpID = subject.getPropertyAsAString("dumpID");
+  ok(dumpID, "There should be a dumpID");
+
+  await crashMan.ensureCrashIsPresent(dumpID);
+  await crashMan.getCrashes().then(crashes => {
+    is(crashes.length, 1, "There should be only one record");
+    const crash = crashes[0];
+    ok(
+      crash.isOfType(
+        crashMan.processTypes[Ci.nsIXULRuntime.PROCESS_TYPE_UTILITY],
+        crashMan.CRASH_TYPE_CRASH
+      ),
+      "Record should be a utility process crash"
+    );
+    ok(crash.id === dumpID, "Record should have an ID");
+    ok(
+      actorsCheck(crash.metadata.UtilityActorsName),
+      `Record should have the correct actors name for: ${crash.metadata.UtilityActorsName}`
+    );
+  });
+
+  let minidumpDirectory = Services.dirsvc.get("ProfD", Ci.nsIFile);
+  minidumpDirectory.append("minidumps");
+
+  let dumpfile = minidumpDirectory.clone();
+  dumpfile.append(dumpID + ".dmp");
+  if (dumpfile.exists()) {
+    info(`Removal of ${dumpfile.path}`);
+    dumpfile.remove(false);
+  }
+
+  let extrafile = minidumpDirectory.clone();
+  extrafile.append(dumpID + ".extra");
+  info(`Removal of ${extrafile.path}`);
+  if (extrafile.exists()) {
+    extrafile.remove(false);
+  }
+}
+
+// Crash a utility process and generate a crash dump.  To close a utility
+// process (forcefully or not) without a generating a crash, use
+// cleanUtilityProcessShutdown.
+async function crashSomeUtilityActor(
+  actor,
+  actorsCheck = () => {
+    return true;
+  }
+) {
+  // Get PID for utility type
+  const procInfos = await getUtilityProcesses(actor);
+  ok(
+    procInfos.length == 1,
+    `exactly one ${actor} utility process should be found`
+  );
+  const utilityPid = procInfos[0].pid;
+  return crashSomeUtility(utilityPid, actorsCheck);
+}
diff --git a/ipc/glue/test/browser/mochitest_audio_off.ini b/ipc/glue/test/browser/mochitest_audio_off.ini
new file mode 100644
index 0000000000..1e105c5f87
--- /dev/null
+++ b/ipc/glue/test/browser/mochitest_audio_off.ini
@@ -0,0 +1,12 @@
+[DEFAULT]
+run-if = toolkit == 'android' && !isolated_process # Bug 1771452
+support-files =
+  head.js
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+prefs =
+  media.utility-process.enabled=false
+
+[test_utility_audio_off.html]
diff --git a/ipc/glue/test/browser/mochitest_audio_on.ini b/ipc/glue/test/browser/mochitest_audio_on.ini
new file mode 100644
index 0000000000..8d74572341
--- /dev/null
+++ b/ipc/glue/test/browser/mochitest_audio_on.ini
@@ -0,0 +1,12 @@
+[DEFAULT]
+run-if = toolkit == 'android' && !isolated_process # Bug 1771452
+support-files =
+  head.js
+  ../../../../dom/media/test/small-shot.ogg
+  ../../../../dom/media/test/small-shot.mp3
+  ../../../../dom/media/test/small-shot.m4a
+  ../../../../dom/media/test/small-shot.flac
+prefs =
+  media.utility-process.enabled=true
+
+[test_utility_audio_on.html]
diff --git a/ipc/glue/test/browser/moz.build b/ipc/glue/test/browser/moz.build
new file mode 100644
index 0000000000..d0a85bebcd
--- /dev/null
+++ b/ipc/glue/test/browser/moz.build
@@ -0,0 +1,12 @@
+# -*- 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/.
+
+BROWSER_CHROME_MANIFESTS += [
+    "browser.ini",
+    "browser_audio_shutdown.ini",
+    "browser_child_hang.ini",
+]
+MOCHITEST_MANIFESTS += ["mochitest_audio_off.ini", "mochitest_audio_on.ini"]
diff --git a/ipc/glue/test/browser/test_utility_audio_off.html b/ipc/glue/test/browser/test_utility_audio_off.html
new file mode 100644
index 0000000000..7df18ed383
--- /dev/null
+++ b/ipc/glue/test/browser/test_utility_audio_off.html
@@ -0,0 +1,44 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Audio decoder not in Utility process</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<pre id="test">
+<script type="text/javascript">
+SimpleTest.waitForExplicitFinish();
+
+(async function() {
+  const platform = SpecialPowers.Services.appinfo.OS;
+  for (let {src, expectations} of audioTestData()) {
+    if (!(platform in expectations)) {
+      info(`Skipping ${src} for ${platform}`);
+      continue;
+    }
+
+    try {
+      await runMochitestUtilityAudio(src, { expectUtility: "", expectDecoder: expectations[platform].decoder, expectContent: true, expectJava: false });
+    } catch (ex) {
+      ok(false, "Failure");
+    }
+  }
+
+  for (let src of [
+    "small-shot.m4a",
+  ]) {
+    try {
+      await runMochitestUtilityAudio(src, { expectUtility: "", expectDecoder: "android decoder", expectContent: false, expectJava: true });
+    } catch (ex) {
+      ok(false, `Failure ${ex}`);
+    }
+  }
+
+  SimpleTest.finish();
+})();
+</script>
+</pre>
+</body>
+</html>
diff --git a/ipc/glue/test/browser/test_utility_audio_on.html b/ipc/glue/test/browser/test_utility_audio_on.html
new file mode 100644
index 0000000000..f473527520
--- /dev/null
+++ b/ipc/glue/test/browser/test_utility_audio_on.html
@@ -0,0 +1,45 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Audio decoder in Utility process</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<pre id="test">
+<script type="text/javascript">
+SimpleTest.waitForExplicitFinish();
+
+(async function() {
+  const platform = SpecialPowers.Services.appinfo.OS;
+  for (let {src, expectations} of audioTestData()) {
+    if (!(platform in expectations)) {
+      info(`Skipping ${src} for ${platform}`);
+      continue;
+    }
+
+    try {
+      await runMochitestUtilityAudio(src, { expectUtility: expectations[platform].process, expectDecoder: expectations[platform].decoder, expectContent: false, expectJava: false });
+    } catch (ex) {
+      ok(false, "Failure");
+    }
+  }
+
+  // Remove all after Bug 1771196
+  for (let src of [
+    "small-shot.m4a",
+  ]) {
+    try {
+      await runMochitestUtilityAudio(src, { expectUtility: "", expectDecoder: "android decoder", expectContent: false, expectJava: true });
+    } catch (ex) {
+      ok(false, `Failure ${ex}`);
+    }
+  }
+
+  SimpleTest.finish();
+})();
+</script>
+</pre>
+</body>
+</html>
diff --git a/ipc/glue/test/gtest/TestAsyncBlockers.cpp b/ipc/glue/test/gtest/TestAsyncBlockers.cpp
new file mode 100644
index 0000000000..6f8d298621
--- /dev/null
+++ b/ipc/glue/test/gtest/TestAsyncBlockers.cpp
@@ -0,0 +1,166 @@
+/* -*- 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 "gtest/gtest.h"
+
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/ipc/AsyncBlockers.h"
+#include "mozilla/gtest/MozHelpers.h"
+
+#include "nsCOMPtr.h"
+#include "nsITimer.h"
+#include "nsINamed.h"
+
+using namespace mozilla;
+using namespace mozilla::ipc;
+
+#define PROCESS_EVENTS_UNTIL(_done) \
+  SpinEventLoopUntil("TestAsyncBlockers"_ns, [&]() { return _done; });
+
+class TestAsyncBlockers : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    SAVE_GDB_SLEEP(mOldSleepDuration);
+    return;
+  }
+
+  void TearDown() final { RESTORE_GDB_SLEEP(mOldSleepDuration); }
+
+ private:
+#if defined(HAS_GDB_SLEEP_DURATION)
+  unsigned int mOldSleepDuration = 0;
+#endif  // defined(HAS_GDB_SLEEP_DURATION)
+};
+
+class Blocker {};
+
+TEST_F(TestAsyncBlockers, Register) {
+  AsyncBlockers blockers;
+  Blocker* blocker = new Blocker();
+  blockers.Register(blocker);
+  EXPECT_TRUE(true);
+}
+
+TEST_F(TestAsyncBlockers, Register_Deregister) {
+  AsyncBlockers blockers;
+  Blocker* blocker = new Blocker();
+  blockers.Register(blocker);
+  blockers.Deregister(blocker);
+  EXPECT_TRUE(true);
+}
+
+TEST_F(TestAsyncBlockers, Register_WaitUntilClear) {
+  AsyncBlockers blockers;
+  bool done = false;
+
+  Blocker* blocker = new Blocker();
+  blockers.Register(blocker);
+
+  blockers.WaitUntilClear(5 * 1000)->Then(GetCurrentSerialEventTarget(),
+                                          __func__, [&]() {
+                                            EXPECT_TRUE(true);
+                                            done = true;
+                                          });
+
+  NS_ProcessPendingEvents(nullptr);
+
+  blockers.Deregister(blocker);
+
+  PROCESS_EVENTS_UNTIL(done);
+}
+
+class AsyncBlockerTimerCallback : public nsITimerCallback, public nsINamed {
+ protected:
+  virtual ~AsyncBlockerTimerCallback();
+
+ public:
+  explicit AsyncBlockerTimerCallback() {}
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSITIMERCALLBACK
+  NS_DECL_NSINAMED
+};
+
+NS_IMPL_ISUPPORTS(AsyncBlockerTimerCallback, nsITimerCallback, nsINamed)
+
+AsyncBlockerTimerCallback::~AsyncBlockerTimerCallback() = default;
+
+NS_IMETHODIMP
+AsyncBlockerTimerCallback::Notify(nsITimer* timer) {
+  // If we resolve through this, it means
+  // blockers.WaitUntilClear() started to wait for
+  // the completion of the timeout which is not
+  // good.
+  EXPECT_TRUE(false);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+AsyncBlockerTimerCallback::GetName(nsACString& aName) {
+  aName.AssignLiteral("AsyncBlockerTimerCallback");
+  return NS_OK;
+}
+
+TEST_F(TestAsyncBlockers, NoRegister_WaitUntilClear) {
+  AsyncBlockers blockers;
+  bool done = false;
+
+  nsCOMPtr<nsITimer> timer = NS_NewTimer();
+  ASSERT_TRUE(timer);
+
+  RefPtr<AsyncBlockerTimerCallback> timerCb = new AsyncBlockerTimerCallback();
+  timer->InitWithCallback(timerCb, 1 * 1000, nsITimer::TYPE_ONE_SHOT);
+
+  blockers.WaitUntilClear(10 * 1000)->Then(GetCurrentSerialEventTarget(),
+                                           __func__, [&]() {
+                                             // If we resolve through this
+                                             // before the nsITimer it means we
+                                             // have been resolved before the 5s
+                                             // timeout
+                                             EXPECT_TRUE(true);
+                                             timer->Cancel();
+                                             done = true;
+                                           });
+
+  PROCESS_EVENTS_UNTIL(done);
+}
+
+TEST_F(TestAsyncBlockers, Register_WaitUntilClear_0s) {
+  AsyncBlockers blockers;
+  bool done = false;
+
+  Blocker* blocker = new Blocker();
+  blockers.Register(blocker);
+
+  blockers.WaitUntilClear(0)->Then(GetCurrentSerialEventTarget(), __func__,
+                                   [&]() {
+                                     EXPECT_TRUE(true);
+                                     done = true;
+                                   });
+
+  NS_ProcessPendingEvents(nullptr);
+
+  blockers.Deregister(blocker);
+
+  PROCESS_EVENTS_UNTIL(done);
+}
+
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED) && !defined(ANDROID) && \
+    !(defined(XP_DARWIN) && !defined(MOZ_DEBUG))
+static void DeregisterEmpty_Test() {
+  mozilla::gtest::DisableCrashReporter();
+
+  AsyncBlockers blockers;
+  Blocker* blocker = new Blocker();
+  blockers.Deregister(blocker);
+}
+
+TEST_F(TestAsyncBlockers, DeregisterEmpty) {
+  ASSERT_DEATH_IF_SUPPORTED(DeregisterEmpty_Test(), "");
+}
+#endif  // defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED) && !defined(ANDROID) &&
+        // !(defined(XP_DARWIN) && !defined(MOZ_DEBUG))
+
+#undef PROCESS_EVENTS_UNTIL
diff --git a/ipc/glue/test/gtest/TestUtilityProcess.cpp b/ipc/glue/test/gtest/TestUtilityProcess.cpp
new file mode 100644
index 0000000000..c5d19c992f
--- /dev/null
+++ b/ipc/glue/test/gtest/TestUtilityProcess.cpp
@@ -0,0 +1,155 @@
+/* -*- 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 "gtest/gtest.h"
+#include "mozilla/SpinEventLoopUntil.h"
+
+#include "mozilla/ipc/UtilityProcessManager.h"
+
+#if defined(MOZ_WIDGET_ANDROID) || defined(XP_MACOSX)
+#  include "nsIAppShellService.h"
+#  include "nsServiceManagerUtils.h"
+#endif  // defined(MOZ_WIDGET_ANDROID) || defined(XP_MACOSX)
+
+#if defined(XP_WIN)
+#  include "mozilla/gtest/MozHelpers.h"
+#  include "mozilla/ipc/UtilityProcessImpl.h"
+#endif  // defined(XP_WIN)
+
+#ifdef MOZ_WIDGET_ANDROID
+#  define NS_APPSHELLSERVICE_CONTRACTID "@mozilla.org/widget/appshell/android;1"
+#endif  // MOZ_WIDGET_ANDROID
+
+#ifdef XP_MACOSX
+#  define NS_APPSHELLSERVICE_CONTRACTID "@mozilla.org/widget/appshell/mac;1"
+#endif  // XP_MACOSX
+
+using namespace mozilla;
+using namespace mozilla::ipc;
+
+#define WAIT_FOR_EVENTS \
+  SpinEventLoopUntil("UtilityProcess::emptyUtil"_ns, [&]() { return done; });
+
+bool setupDone = false;
+
+class UtilityProcess : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    if (setupDone) {
+      return;
+    }
+
+#if defined(MOZ_WIDGET_ANDROID) || defined(XP_MACOSX)
+    appShell = do_GetService(NS_APPSHELLSERVICE_CONTRACTID);
+#endif  // defined(MOZ_WIDGET_ANDROID) || defined(XP_MACOSX)
+
+#if defined(XP_WIN) && defined(MOZ_SANDBOX)
+    mozilla::SandboxBroker::GeckoDependentInitialize();
+#endif  // defined(XP_WIN) && defined(MOZ_SANDBOX)
+
+    setupDone = true;
+  }
+
+#if defined(MOZ_WIDGET_ANDROID) || defined(XP_MACOSX)
+  nsCOMPtr<nsIAppShellService> appShell;
+#endif  // defined(MOZ_WIDGET_ANDROID) || defined(XP_MACOSX)
+};
+
+TEST_F(UtilityProcess, ProcessManager) {
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  ASSERT_NE(utilityProc, nullptr);
+}
+
+TEST_F(UtilityProcess, NoProcess) {
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  EXPECT_NE(utilityProc, nullptr);
+
+  Maybe<int32_t> noPid =
+      utilityProc->ProcessPid(SandboxingKind::GENERIC_UTILITY);
+  ASSERT_TRUE(noPid.isNothing());
+}
+
+TEST_F(UtilityProcess, LaunchProcess) {
+  bool done = false;
+
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  EXPECT_NE(utilityProc, nullptr);
+
+  int32_t thisPid = base::GetCurrentProcId();
+  EXPECT_GE(thisPid, 1);
+
+  utilityProc->LaunchProcess(SandboxingKind::GENERIC_UTILITY)
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [&]() mutable {
+            EXPECT_TRUE(true);
+
+            Maybe<int32_t> utilityPid =
+                utilityProc->ProcessPid(SandboxingKind::GENERIC_UTILITY);
+            EXPECT_TRUE(utilityPid.isSome());
+            EXPECT_GE(*utilityPid, 1);
+            EXPECT_NE(*utilityPid, thisPid);
+
+            printf_stderr("UtilityProcess running as %d\n", *utilityPid);
+
+            done = true;
+          },
+          [&](nsresult aError) mutable {
+            EXPECT_TRUE(false);
+            done = true;
+          });
+
+  WAIT_FOR_EVENTS;
+}
+
+TEST_F(UtilityProcess, DestroyProcess) {
+  bool done = false;
+
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+
+  utilityProc->LaunchProcess(SandboxingKind::GENERIC_UTILITY)
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [&]() {
+            Maybe<int32_t> utilityPid =
+                utilityProc->ProcessPid(SandboxingKind::GENERIC_UTILITY);
+            EXPECT_TRUE(utilityPid.isSome());
+            EXPECT_GE(*utilityPid, 1);
+
+            utilityProc->CleanShutdown(SandboxingKind::GENERIC_UTILITY);
+
+            utilityPid =
+                utilityProc->ProcessPid(SandboxingKind::GENERIC_UTILITY);
+            EXPECT_TRUE(utilityPid.isNothing());
+
+            EXPECT_TRUE(true);
+            done = true;
+          },
+          [&](nsresult aError) {
+            EXPECT_TRUE(false);
+            done = true;
+          });
+
+  WAIT_FOR_EVENTS;
+}
+
+#if defined(XP_WIN)
+static void LoadLibraryCrash_Test() {
+  mozilla::gtest::DisableCrashReporter();
+  // Just a uuidgen name to have something random
+  UtilityProcessImpl::LoadLibraryOrCrash(
+      L"2b49036e-6ba3-400c-a297-38fa1f6c5255.dll");
+}
+
+TEST_F(UtilityProcess, LoadLibraryCrash) {
+  ASSERT_DEATH_IF_SUPPORTED(LoadLibraryCrash_Test(), "");
+}
+#endif  // defined(XP_WIN)
+
+#undef WAIT_FOR_EVENTS
diff --git a/ipc/glue/test/gtest/moz.build b/ipc/glue/test/gtest/moz.build
new file mode 100644
index 0000000000..7b72cc7fe1
--- /dev/null
+++ b/ipc/glue/test/gtest/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; c-basic-offset: 4; 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/.
+
+Library("ipcgluetest")
+
+UNIFIED_SOURCES = [
+    "TestAsyncBlockers.cpp",
+    "TestUtilityProcess.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/widget",
+    "/widget/android",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/ipc/glue/test/utility_process_xpcom/UtilityProcessTest.cpp b/ipc/glue/test/utility_process_xpcom/UtilityProcessTest.cpp
new file mode 100644
index 0000000000..3828c6971b
--- /dev/null
+++ b/ipc/glue/test/utility_process_xpcom/UtilityProcessTest.cpp
@@ -0,0 +1,164 @@
+/* -*- 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/. */
+
+#if defined(ENABLE_TESTS)
+#  include "mozilla/ipc/UtilityProcessTest.h"
+#  include "mozilla/ipc/UtilityProcessManager.h"
+#  include "mozilla/dom/Promise.h"
+#  include "mozilla/ProcInfo.h"
+#  include "mozilla/IntentionalCrash.h"
+
+namespace mozilla::ipc {
+
+static UtilityActorName UtilityActorNameFromString(
+    const nsACString& aStringName) {
+  using namespace mozilla::dom;
+
+  // We use WebIDLUtilityActorNames because UtilityActorNames is not designed
+  // for iteration.
+  for (size_t i = 0; i < WebIDLUtilityActorNameValues::Count; ++i) {
+    auto idlName = static_cast<UtilityActorName>(i);
+    const nsDependentCSubstring idlNameString(
+        WebIDLUtilityActorNameValues::GetString(idlName));
+    if (idlNameString.Equals(aStringName)) {
+      return idlName;
+    }
+  }
+  MOZ_CRASH("Unknown utility actor name");
+}
+
+// Find the utility process with the given actor or any utility process if
+// the actor is UtilityActorName::EndGuard_.
+static SandboxingKind FindUtilityProcessWithActor(UtilityActorName aActorName) {
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  MOZ_ASSERT(utilityProc, "No UtilityprocessManager?");
+
+  for (size_t i = 0; i < SandboxingKind::COUNT; ++i) {
+    auto sbKind = static_cast<SandboxingKind>(i);
+    if (!utilityProc->Process(sbKind)) {
+      continue;
+    }
+    if (aActorName == UtilityActorName::EndGuard_) {
+      return sbKind;
+    }
+    for (auto actor : utilityProc->GetActors(sbKind)) {
+      if (actor == aActorName) {
+        return sbKind;
+      }
+    }
+  }
+
+  return SandboxingKind::COUNT;
+}
+
+NS_IMETHODIMP
+UtilityProcessTest::StartProcess(const nsTArray<nsCString>& aActorsToRegister,
+                                 JSContext* aCx,
+                                 mozilla::dom::Promise** aOutPromise) {
+  NS_ENSURE_ARG(aOutPromise);
+  *aOutPromise = nullptr;
+  nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
+  if (NS_WARN_IF(!global)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  ErrorResult erv;
+  RefPtr<dom::Promise> promise = dom::Promise::Create(global, erv);
+  if (NS_WARN_IF(erv.Failed())) {
+    return erv.StealNSResult();
+  }
+
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  MOZ_ASSERT(utilityProc, "No UtilityprocessManager?");
+
+  auto actors = aActorsToRegister.Clone();
+
+  utilityProc->LaunchProcess(SandboxingKind::GENERIC_UTILITY)
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [promise, utilityProc, actors = std::move(actors)] {
+            RefPtr<UtilityProcessParent> utilityParent =
+                utilityProc->GetProcessParent(SandboxingKind::GENERIC_UTILITY);
+            Maybe<int32_t> utilityPid =
+                utilityProc->ProcessPid(SandboxingKind::GENERIC_UTILITY);
+            for (size_t i = 0; i < actors.Length(); ++i) {
+              auto uan = UtilityActorNameFromString(actors[i]);
+              utilityProc->RegisterActor(utilityParent, uan);
+            }
+            if (utilityPid.isSome()) {
+              promise->MaybeResolve(*utilityPid);
+            } else {
+              promise->MaybeReject(NS_ERROR_NOT_AVAILABLE);
+            }
+          },
+          [promise](nsresult aError) {
+            MOZ_ASSERT_UNREACHABLE(
+                "UtilityProcessTest; failure to get Utility process");
+            promise->MaybeReject(aError);
+          });
+
+  promise.forget(aOutPromise);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+UtilityProcessTest::NoteIntentionalCrash(uint32_t aPid) {
+  mozilla::NoteIntentionalCrash("utility", aPid);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+UtilityProcessTest::StopProcess(const char* aActorName) {
+  using namespace mozilla::dom;
+
+  SandboxingKind sbKind;
+  if (aActorName) {
+    const nsDependentCString actorStringName(aActorName);
+    UtilityActorName actorName = UtilityActorNameFromString(actorStringName);
+    sbKind = FindUtilityProcessWithActor(actorName);
+  } else {
+    sbKind = FindUtilityProcessWithActor(UtilityActorName::EndGuard_);
+  }
+
+  if (sbKind == SandboxingKind::COUNT) {
+    MOZ_ASSERT_UNREACHABLE(
+        "Attempted to stop process for actor when no "
+        "such process exists");
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  MOZ_ASSERT(utilityProc, "No UtilityprocessManager?");
+
+  utilityProc->CleanShutdown(sbKind);
+  Maybe<int32_t> utilityPid = utilityProc->ProcessPid(sbKind);
+  MOZ_RELEASE_ASSERT(utilityPid.isNothing(),
+                     "Should not have a utility process PID anymore");
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+UtilityProcessTest::TestTelemetryProbes() {
+  RefPtr<UtilityProcessManager> utilityProc =
+      UtilityProcessManager::GetSingleton();
+  MOZ_ASSERT(utilityProc, "No UtilityprocessManager?");
+
+  for (RefPtr<UtilityProcessParent>& parent :
+       utilityProc->GetAllProcessesProcessParent()) {
+    Unused << parent->SendTestTelemetryProbes();
+  }
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(UtilityProcessTest, nsIUtilityProcessTest)
+
+}  // namespace mozilla::ipc
+#endif  // defined(ENABLE_TESTS)
diff --git a/ipc/glue/test/utility_process_xpcom/UtilityProcessTest.h b/ipc/glue/test/utility_process_xpcom/UtilityProcessTest.h
new file mode 100644
index 0000000000..6c80fce71b
--- /dev/null
+++ b/ipc/glue/test/utility_process_xpcom/UtilityProcessTest.h
@@ -0,0 +1,29 @@
+/* -*- 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 _include_ipc_glue_UtilityProcessTest_h_
+#define _include_ipc_glue_UtilityProcessTest_h_
+
+#if defined(ENABLE_TESTS)
+#  include "nsServiceManagerUtils.h"
+#  include "nsIUtilityProcessTest.h"
+
+namespace mozilla::ipc {
+
+class UtilityProcessTest final : public nsIUtilityProcessTest {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIUTILITYPROCESSTEST
+
+  UtilityProcessTest() = default;
+
+ private:
+  ~UtilityProcessTest() = default;
+};
+
+}  // namespace mozilla::ipc
+#endif  // defined(ENABLE_TESTS)
+
+#endif  // _include_ipc_glue_UtilityProcessTest_h_
diff --git a/ipc/glue/test/utility_process_xpcom/components.conf b/ipc/glue/test/utility_process_xpcom/components.conf
new file mode 100644
index 0000000000..25208ba7fc
--- /dev/null
+++ b/ipc/glue/test/utility_process_xpcom/components.conf
@@ -0,0 +1,15 @@
+# -*- 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': '{0a4478f4-c5ae-4fb1-8686-d5b09fb99afb}',
+        'contract_ids': ['@mozilla.org/utility-process-test;1'],
+        'type': 'mozilla::ipc::UtilityProcessTest',
+        'headers': ['mozilla/ipc/UtilityProcessTest.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+]
diff --git a/ipc/glue/test/utility_process_xpcom/moz.build b/ipc/glue/test/utility_process_xpcom/moz.build
new file mode 100644
index 0000000000..f04b436cbe
--- /dev/null
+++ b/ipc/glue/test/utility_process_xpcom/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.ipc += ["UtilityProcessTest.h"]
+
+UNIFIED_SOURCES += ["UtilityProcessTest.cpp"]
+
+XPCOM_MANIFESTS += ["components.conf"]
+
+XPIDL_MODULE = "utility_process_xpcom_test"
+
+XPIDL_SOURCES += [
+    "nsIUtilityProcessTest.idl",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
diff --git a/ipc/glue/test/utility_process_xpcom/nsIUtilityProcessTest.idl b/ipc/glue/test/utility_process_xpcom/nsIUtilityProcessTest.idl
new file mode 100644
index 0000000000..839c4f3673
--- /dev/null
+++ b/ipc/glue/test/utility_process_xpcom/nsIUtilityProcessTest.idl
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 8 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+[scriptable, uuid(0a4478f4-c5ae-4fb1-8686-d5b09fb99afb)]
+interface nsIUtilityProcessTest : nsISupports
+{
+  /**
+   * ** Test-only Method **
+   *
+   * Allowing to start Utility Process from JS code.
+   *
+   * actorsToAdd: An array of actor names, taken from WebIDLUtilityActorName.
+   * Unlike normal utility processes, test processes launched this way do not
+   * have any associated actor names unless specified here.  Empty by default.
+   */
+  [implicit_jscontext]
+  Promise startProcess([optional] in Array<ACString> actorsToAdd);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Note that we are going to manually crash a process
+   */
+  void noteIntentionalCrash(in unsigned long pid);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Allowing to stop Utility Process from JS code.
+   * Default behavior is to stop any utility process.
+   */
+  void stopProcess([optional] in string utilityActorName);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Sending Telemetry probes
+   */
+  void testTelemetryProbes();
+};