Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

23 files changed, 4700 insertions, 0 deletions

diff --git a/dom/workers/remoteworkers/PRemoteWorker.ipdl b/dom/workers/remoteworkers/PRemoteWorker.ipdl
new file mode 100644
index 0000000000..4da11c4840
--- /dev/null
+++ b/dom/workers/remoteworkers/PRemoteWorker.ipdl
@@ -0,0 +1,90 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. 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;
+include protocol PFetchEventOpProxy;
+
+include DOMTypes;
+include ServiceWorkerOpArgs;
+include RemoteWorkerTypes;
+
+namespace mozilla {
+namespace dom {
+
+struct RemoteWorkerSuspendOp
+{};
+
+struct RemoteWorkerResumeOp
+{};
+
+struct RemoteWorkerFreezeOp
+{};
+
+struct RemoteWorkerThawOp
+{};
+
+struct RemoteWorkerTerminateOp
+{};
+
+struct RemoteWorkerPortIdentifierOp
+{
+  MessagePortIdentifier portIdentifier;
+};
+
+struct RemoteWorkerAddWindowIDOp
+{
+  uint64_t windowID;
+};
+
+struct RemoteWorkerRemoveWindowIDOp
+{
+  uint64_t windowID;
+};
+
+union RemoteWorkerOp {
+  RemoteWorkerSuspendOp;
+  RemoteWorkerResumeOp;
+  RemoteWorkerFreezeOp;
+  RemoteWorkerThawOp;
+  RemoteWorkerTerminateOp;
+  RemoteWorkerPortIdentifierOp;
+  RemoteWorkerAddWindowIDOp;
+  RemoteWorkerRemoveWindowIDOp;
+};
+
+// This protocol is used to make a remote worker controllable from the parent
+// process. The parent process will receive operations from the
+// PRemoteWorkerController protocol.
+protocol PRemoteWorker
+{
+  manager PBackground;
+
+  manages PFetchEventOpProxy;
+
+parent:
+  async Created(bool aStatus);
+
+  async Error(ErrorValue aValue);
+
+  async NotifyLock(bool aCreated);
+
+  async NotifyWebTransport(bool aCreated);
+
+  async Close();
+
+  async SetServiceWorkerSkipWaitingFlag() returns (bool aOk);
+
+child:
+  async PFetchEventOpProxy(ParentToChildServiceWorkerFetchEventOpArgs aArgs);
+
+  async __delete__();
+
+  async ExecOp(RemoteWorkerOp op);
+
+  async ExecServiceWorkerOp(ServiceWorkerOpArgs aArgs)
+      returns (ServiceWorkerOpResult aResult);
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/workers/remoteworkers/PRemoteWorkerController.ipdl b/dom/workers/remoteworkers/PRemoteWorkerController.ipdl
new file mode 100644
index 0000000000..5c3818a27d
--- /dev/null
+++ b/dom/workers/remoteworkers/PRemoteWorkerController.ipdl
@@ -0,0 +1,49 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. 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;
+include protocol PFetchEventOp;
+
+include RemoteWorkerTypes;
+include ServiceWorkerOpArgs;
+
+namespace mozilla {
+namespace dom {
+
+/**
+ * Proxy protocol used by ServiceWorkerManager whose canonical state exists on
+ * the main thread to control/receive feedback from RemoteWorkers which are
+ * canonically controlled from the PBackground thread.  Exclusively for use from
+ * the parent process main thread to the parent process PBackground thread.
+ */
+[ManualDealloc]
+protocol PRemoteWorkerController {
+  manager PBackground;
+
+  manages PFetchEventOp;
+
+ child:
+  async CreationFailed();
+
+  async CreationSucceeded();
+
+  async ErrorReceived(ErrorValue aError);
+
+  async Terminated();
+
+  async SetServiceWorkerSkipWaitingFlag() returns (bool aOk);
+
+ parent:
+  async PFetchEventOp(ParentToParentServiceWorkerFetchEventOpArgs aArgs);
+
+  async __delete__();
+
+  async Shutdown() returns (bool aOk);
+
+  async ExecServiceWorkerOp(ServiceWorkerOpArgs aArgs)
+      returns (ServiceWorkerOpResult aResult);
+};
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/PRemoteWorkerService.ipdl b/dom/workers/remoteworkers/PRemoteWorkerService.ipdl
new file mode 100644
index 0000000000..6287bb56a1
--- /dev/null
+++ b/dom/workers/remoteworkers/PRemoteWorkerService.ipdl
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. 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;
+
+include ProtocolTypes;
+include RemoteWorkerTypes;
+
+namespace mozilla {
+namespace dom {
+
+// Simple protocol to register any active RemoteWorkerService running on any
+// process.  Initialization/registration is delayed for preallocated processes
+// until the process takes on its final remoteType.
+protocol PRemoteWorkerService
+{
+  manager PBackground;
+
+parent:
+  async __delete__();
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerChild.cpp b/dom/workers/remoteworkers/RemoteWorkerChild.cpp
new file mode 100644
index 0000000000..163fd00fec
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerChild.cpp
@@ -0,0 +1,1011 @@
+/* -*- 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 "RemoteWorkerChild.h"
+
+#include <utility>
+
+#include "MainThreadUtils.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsIConsoleReportCollector.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIPrincipal.h"
+#include "nsNetUtil.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+#include "RemoteWorkerService.h"
+#include "mozilla/ArrayAlgorithm.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/Services.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/FetchEventOpProxyChild.h"
+#include "mozilla/dom/IndexedDatabaseManager.h"
+#include "mozilla/dom/MessagePort.h"
+#include "mozilla/dom/RemoteWorkerManager.h"  // RemoteWorkerManager::IsRemoteTypeAllowed
+#include "mozilla/dom/RemoteWorkerTypes.h"
+#include "mozilla/dom/ServiceWorkerDescriptor.h"
+#include "mozilla/dom/ServiceWorkerInterceptController.h"
+#include "mozilla/dom/ServiceWorkerOp.h"
+#include "mozilla/dom/ServiceWorkerRegistrationDescriptor.h"
+#include "mozilla/dom/ServiceWorkerShutdownState.h"
+#include "mozilla/dom/ServiceWorkerUtils.h"
+#include "mozilla/dom/workerinternals/ScriptLoader.h"
+#include "mozilla/dom/WorkerError.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/dom/WorkerRef.h"
+#include "mozilla/dom/WorkerRunnable.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "mozilla/net/CookieJarSettings.h"
+#include "mozilla/PermissionManager.h"
+
+mozilla::LazyLogModule gRemoteWorkerChildLog("RemoteWorkerChild");
+
+#ifdef LOG
+#  undef LOG
+#endif
+#define LOG(fmt) MOZ_LOG(gRemoteWorkerChildLog, mozilla::LogLevel::Verbose, fmt)
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+using workerinternals::ChannelFromScriptURLMainThread;
+
+namespace {
+
+class SharedWorkerInterfaceRequestor final : public nsIInterfaceRequestor {
+ public:
+  NS_DECL_ISUPPORTS
+
+  SharedWorkerInterfaceRequestor() {
+    // This check must match the code nsDocShell::Create.
+    if (XRE_IsParentProcess()) {
+      mSWController = new ServiceWorkerInterceptController();
+    }
+  }
+
+  NS_IMETHOD
+  GetInterface(const nsIID& aIID, void** aSink) override {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    if (mSWController &&
+        aIID.Equals(NS_GET_IID(nsINetworkInterceptController))) {
+      // If asked for the network intercept controller, ask the outer requestor,
+      // which could be the docshell.
+      RefPtr<ServiceWorkerInterceptController> swController = mSWController;
+      swController.forget(aSink);
+      return NS_OK;
+    }
+
+    return NS_NOINTERFACE;
+  }
+
+ private:
+  ~SharedWorkerInterfaceRequestor() = default;
+
+  RefPtr<ServiceWorkerInterceptController> mSWController;
+};
+
+NS_IMPL_ADDREF(SharedWorkerInterfaceRequestor)
+NS_IMPL_RELEASE(SharedWorkerInterfaceRequestor)
+NS_IMPL_QUERY_INTERFACE(SharedWorkerInterfaceRequestor, nsIInterfaceRequestor)
+
+// Normal runnable because AddPortIdentifier() is going to exec JS code.
+class MessagePortIdentifierRunnable final : public WorkerRunnable {
+ public:
+  MessagePortIdentifierRunnable(WorkerPrivate* aWorkerPrivate,
+                                RemoteWorkerChild* aActor,
+                                const MessagePortIdentifier& aPortIdentifier)
+      : WorkerRunnable(aWorkerPrivate),
+        mActor(aActor),
+        mPortIdentifier(aPortIdentifier) {}
+
+ private:
+  bool WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) override {
+    mActor->AddPortIdentifier(aCx, aWorkerPrivate, mPortIdentifier);
+    return true;
+  }
+
+  RefPtr<RemoteWorkerChild> mActor;
+  UniqueMessagePortId mPortIdentifier;
+};
+
+}  // anonymous namespace
+
+RemoteWorkerChild::RemoteWorkerChild(const RemoteWorkerData& aData)
+    : mState(VariantType<Pending>(), "RemoteWorkerChild::mState"),
+      mServiceKeepAlive(RemoteWorkerService::MaybeGetKeepAlive()),
+      mIsServiceWorker(aData.serviceWorkerData().type() ==
+                       OptionalServiceWorkerData::TServiceWorkerData) {
+  MOZ_ASSERT(RemoteWorkerService::Thread()->IsOnCurrentThread());
+}
+
+RemoteWorkerChild::~RemoteWorkerChild() {
+#ifdef DEBUG
+  auto lock = mState.Lock();
+  MOZ_ASSERT(lock->is<Killed>());
+#endif
+}
+
+void RemoteWorkerChild::ActorDestroy(ActorDestroyReason) {
+  auto launcherData = mLauncherData.Access();
+
+  Unused << NS_WARN_IF(!launcherData->mTerminationPromise.IsEmpty());
+  launcherData->mTerminationPromise.RejectIfExists(NS_ERROR_DOM_ABORT_ERR,
+                                                   __func__);
+
+  auto lock = mState.Lock();
+
+  // If the worker hasn't shutdown or begun shutdown, we need to ensure it gets
+  // canceled.
+  if (NS_WARN_IF(!lock->is<Killed>() && !lock->is<Canceled>())) {
+    // In terms of strong references to this RemoteWorkerChild, at this moment:
+    // - IPC is holding a strong reference that will be dropped in the near
+    //   future after this method returns.
+    // - If the worker has been started by ExecWorkerOnMainThread, then
+    //   WorkerPrivate::mRemoteWorkerController is a strong reference to us.
+    //   If the worker has not been started, ExecWorker's runnable lambda will
+    //   have a strong reference that will cover the call to
+    //   ExecWorkerOnMainThread.
+    //   - The WorkerPrivate cancellation and termination callbacks will also
+    //     hold strong references, but those callbacks will not outlive the
+    //     WorkerPrivate and are not exposed to callers like
+    //     mRemoteWorkerController is.
+    //
+    // Note that this call to RequestWorkerCancellation can still race worker
+    // cancellation, in which case the strong reference obtained by
+    // NewRunnableMethod can end up being the last strong reference.
+    // (RequestWorkerCancellation handles the case that the Worker is already
+    // canceled if this happens.)
+    RefPtr<nsIRunnable> runnable =
+        NewRunnableMethod("RequestWorkerCancellation", this,
+                          &RemoteWorkerChild::RequestWorkerCancellation);
+    MOZ_ALWAYS_SUCCEEDS(
+        SchedulerGroup::Dispatch(TaskCategory::Other, runnable.forget()));
+  }
+}
+
+void RemoteWorkerChild::ExecWorker(const RemoteWorkerData& aData) {
+#ifdef DEBUG
+  MOZ_ASSERT(GetActorEventTarget()->IsOnCurrentThread());
+  auto launcherData = mLauncherData.Access();
+  MOZ_ASSERT(CanSend());
+#endif
+
+  RefPtr<RemoteWorkerChild> self = this;
+
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      __func__, [self = std::move(self), data = aData]() mutable {
+        nsresult rv = self->ExecWorkerOnMainThread(std::move(data));
+
+        // Creation failure will already have been reported via the method
+        // above internally using ScopeExit.
+        Unused << NS_WARN_IF(NS_FAILED(rv));
+      });
+
+  MOZ_ALWAYS_SUCCEEDS(
+      SchedulerGroup::Dispatch(TaskCategory::Other, r.forget()));
+}
+
+nsresult RemoteWorkerChild::ExecWorkerOnMainThread(RemoteWorkerData&& aData) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Ensure that the IndexedDatabaseManager is initialized so that if any
+  // workers do any IndexedDB calls that all of IDB's prefs/etc. are
+  // initialized.
+  Unused << NS_WARN_IF(!IndexedDatabaseManager::GetOrCreate());
+
+  auto scopeExit =
+      MakeScopeExit([&] { ExceptionalErrorTransitionDuringExecWorker(); });
+
+  // Verify the the RemoteWorker should be really allowed to run in this
+  // process, and fail if it shouldn't (This shouldn't normally happen,
+  // unless the RemoteWorkerData has been tempered in the process it was
+  // sent from).
+  if (!RemoteWorkerManager::IsRemoteTypeAllowed(aData)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  auto principalOrErr = PrincipalInfoToPrincipal(aData.principalInfo());
+  if (NS_WARN_IF(principalOrErr.isErr())) {
+    return principalOrErr.unwrapErr();
+  }
+
+  nsCOMPtr<nsIPrincipal> principal = principalOrErr.unwrap();
+
+  auto loadingPrincipalOrErr =
+      PrincipalInfoToPrincipal(aData.loadingPrincipalInfo());
+  if (NS_WARN_IF(loadingPrincipalOrErr.isErr())) {
+    return loadingPrincipalOrErr.unwrapErr();
+  }
+
+  auto partitionedPrincipalOrErr =
+      PrincipalInfoToPrincipal(aData.partitionedPrincipalInfo());
+  if (NS_WARN_IF(partitionedPrincipalOrErr.isErr())) {
+    return partitionedPrincipalOrErr.unwrapErr();
+  }
+
+  WorkerLoadInfo info;
+  info.mBaseURI = DeserializeURI(aData.baseScriptURL());
+  info.mResolvedScriptURI = DeserializeURI(aData.resolvedScriptURL());
+
+  info.mPrincipalInfo = MakeUnique<PrincipalInfo>(aData.principalInfo());
+  info.mPartitionedPrincipalInfo =
+      MakeUnique<PrincipalInfo>(aData.partitionedPrincipalInfo());
+
+  info.mReferrerInfo = aData.referrerInfo();
+  info.mDomain = aData.domain();
+  info.mTrials = aData.originTrials();
+  info.mPrincipal = principal;
+  info.mPartitionedPrincipal = partitionedPrincipalOrErr.unwrap();
+  info.mLoadingPrincipal = loadingPrincipalOrErr.unwrap();
+  info.mStorageAccess = aData.storageAccess();
+  info.mUseRegularPrincipal = aData.useRegularPrincipal();
+  info.mHasStorageAccessPermissionGranted =
+      aData.hasStorageAccessPermissionGranted();
+  info.mIsThirdPartyContextToTopWindow = aData.isThirdPartyContextToTopWindow();
+  info.mOriginAttributes =
+      BasePrincipal::Cast(principal)->OriginAttributesRef();
+  info.mShouldResistFingerprinting = aData.shouldResistFingerprinting();
+  net::CookieJarSettings::Deserialize(aData.cookieJarSettings(),
+                                      getter_AddRefs(info.mCookieJarSettings));
+  info.mCookieJarSettingsArgs = aData.cookieJarSettings();
+
+  // Default CSP permissions for now.  These will be overrided if necessary
+  // based on the script CSP headers during load in ScriptLoader.
+  info.mEvalAllowed = true;
+  info.mReportEvalCSPViolations = false;
+  info.mWasmEvalAllowed = true;
+  info.mReportWasmEvalCSPViolations = false;
+  info.mSecureContext = aData.isSecureContext()
+                            ? WorkerLoadInfo::eSecureContext
+                            : WorkerLoadInfo::eInsecureContext;
+
+  WorkerPrivate::OverrideLoadInfoLoadGroup(info, info.mLoadingPrincipal);
+
+  RefPtr<SharedWorkerInterfaceRequestor> requestor =
+      new SharedWorkerInterfaceRequestor();
+  info.mInterfaceRequestor->SetOuterRequestor(requestor);
+
+  Maybe<ClientInfo> clientInfo;
+  if (aData.clientInfo().isSome()) {
+    clientInfo.emplace(ClientInfo(aData.clientInfo().ref()));
+  }
+
+  nsresult rv = NS_OK;
+
+  if (clientInfo.isSome()) {
+    Maybe<mozilla::ipc::CSPInfo> cspInfo = clientInfo.ref().GetCspInfo();
+    if (cspInfo.isSome()) {
+      info.mCSP = CSPInfoToCSP(cspInfo.ref(), nullptr);
+      info.mCSPInfo = MakeUnique<CSPInfo>();
+      rv = CSPToCSPInfo(info.mCSP, info.mCSPInfo.get());
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    }
+  }
+
+  rv = info.SetPrincipalsAndCSPOnMainThread(
+      info.mPrincipal, info.mPartitionedPrincipal, info.mLoadGroup, info.mCSP);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsString workerPrivateId;
+
+  if (mIsServiceWorker) {
+    ServiceWorkerData& data = aData.serviceWorkerData().get_ServiceWorkerData();
+
+    MOZ_ASSERT(!data.id().IsEmpty());
+    workerPrivateId = std::move(data.id());
+
+    info.mServiceWorkerCacheName = data.cacheName();
+    info.mServiceWorkerDescriptor.emplace(data.descriptor());
+    info.mServiceWorkerRegistrationDescriptor.emplace(
+        data.registrationDescriptor());
+    info.mLoadFlags = static_cast<nsLoadFlags>(data.loadFlags());
+  } else {
+    // Top level workers' main script use the document charset for the script
+    // uri encoding.
+    rv = ChannelFromScriptURLMainThread(
+        info.mLoadingPrincipal, nullptr /* parent document */, info.mLoadGroup,
+        info.mResolvedScriptURI, aData.type(), aData.credentials(), clientInfo,
+        nsIContentPolicy::TYPE_INTERNAL_SHARED_WORKER, info.mCookieJarSettings,
+        info.mReferrerInfo, getter_AddRefs(info.mChannel));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  info.mAgentClusterId = aData.agentClusterId();
+
+  AutoJSAPI jsapi;
+  jsapi.Init();
+
+  ErrorResult error;
+  RefPtr<RemoteWorkerChild> self = this;
+  RefPtr<WorkerPrivate> workerPrivate = WorkerPrivate::Constructor(
+      jsapi.cx(), aData.originalScriptURL(), false,
+      mIsServiceWorker ? WorkerKindService : WorkerKindShared,
+      aData.credentials(), aData.type(), aData.name(), VoidCString(), &info,
+      error, std::move(workerPrivateId),
+      [self](bool aEverRan) {
+        self->OnWorkerCancellationTransitionStateFromPendingOrRunningToCanceled();
+      },
+      // This will be invoked here on the main thread when the worker is already
+      // fully shutdown.  This replaces a prior approach where we would
+      // begin to transition when the worker thread would reach the Canceling
+      // state.  This lambda ensures that we not only wait for the Killing state
+      // to be reached but that the global shutdown has already occurred.
+      [self]() { self->TransitionStateFromCanceledToKilled(); });
+
+  if (NS_WARN_IF(error.Failed())) {
+    MOZ_ASSERT(!workerPrivate);
+
+    rv = error.StealNSResult();
+    return rv;
+  }
+
+  workerPrivate->SetRemoteWorkerController(this);
+
+  // This wants to run as a normal task sequentially after the top level script
+  // evaluation, so the hybrid target is the correct choice between hybrid and
+  // `ControlEventTarget`.
+  nsCOMPtr<nsISerialEventTarget> workerTarget =
+      workerPrivate->HybridEventTarget();
+
+  nsCOMPtr<nsIRunnable> runnable = NewCancelableRunnableMethod(
+      "InitialzeOnWorker", this, &RemoteWorkerChild::InitializeOnWorker);
+
+  {
+    MOZ_ASSERT(workerPrivate);
+    auto lock = mState.Lock();
+    // We MUST be pending here, so direct access is ok.
+    lock->as<Pending>().mWorkerPrivate = std::move(workerPrivate);
+  }
+
+  if (mIsServiceWorker) {
+    nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+        __func__, [workerTarget,
+                   initializeWorkerRunnable = std::move(runnable)]() mutable {
+          Unused << NS_WARN_IF(NS_FAILED(
+              workerTarget->Dispatch(initializeWorkerRunnable.forget())));
+        });
+
+    RefPtr<PermissionManager> permissionManager =
+        PermissionManager::GetInstance();
+    if (!permissionManager) {
+      return NS_ERROR_FAILURE;
+    }
+    permissionManager->WhenPermissionsAvailable(principal, r);
+  } else {
+    if (NS_WARN_IF(NS_FAILED(workerTarget->Dispatch(runnable.forget())))) {
+      rv = NS_ERROR_FAILURE;
+      return rv;
+    }
+  }
+
+  scopeExit.release();
+
+  return NS_OK;
+}
+
+void RemoteWorkerChild::RequestWorkerCancellation() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  LOG(("RequestWorkerCancellation[this=%p]", this));
+
+  // We want to ensure that we've requested the worker be canceled.  So if the
+  // worker is running, cancel it.  We can't do this with the lock held,
+  // however, because our lambdas will want to manipulate the state.
+  RefPtr<WorkerPrivate> cancelWith;
+  {
+    auto lock = mState.Lock();
+    if (lock->is<Pending>()) {
+      cancelWith = lock->as<Pending>().mWorkerPrivate;
+    } else if (lock->is<Running>()) {
+      cancelWith = lock->as<Running>().mWorkerPrivate;
+    }
+  }
+
+  if (cancelWith) {
+    cancelWith->Cancel();
+  }
+}
+
+// This method will be invoked on the worker after the top-level
+// CompileScriptRunnable task has succeeded and as long as the worker has not
+// been closed/canceled.  There are edge-cases related to cancellation, but we
+// have our caller ensure that we are only called as long as the worker's state
+// is Running.
+//
+// (https://bugzilla.mozilla.org/show_bug.cgi?id=1800659 will eliminate
+// cancellation, and the documentation around that bug / in design documents
+// helps provide more context about this.)
+void RemoteWorkerChild::InitializeOnWorker() {
+  nsCOMPtr<nsIRunnable> r =
+      NewRunnableMethod("TransitionStateToRunning", this,
+                        &RemoteWorkerChild::TransitionStateToRunning);
+  MOZ_ALWAYS_SUCCEEDS(
+      SchedulerGroup::Dispatch(TaskCategory::Other, r.forget()));
+}
+
+RefPtr<GenericNonExclusivePromise> RemoteWorkerChild::GetTerminationPromise() {
+  auto launcherData = mLauncherData.Access();
+  return launcherData->mTerminationPromise.Ensure(__func__);
+}
+
+void RemoteWorkerChild::CreationSucceededOnAnyThread() {
+  CreationSucceededOrFailedOnAnyThread(true);
+}
+
+void RemoteWorkerChild::CreationFailedOnAnyThread() {
+  CreationSucceededOrFailedOnAnyThread(false);
+}
+
+void RemoteWorkerChild::CreationSucceededOrFailedOnAnyThread(
+    bool aDidCreationSucceed) {
+#ifdef DEBUG
+  {
+    auto lock = mState.Lock();
+    MOZ_ASSERT_IF(aDidCreationSucceed, lock->is<Running>());
+    MOZ_ASSERT_IF(!aDidCreationSucceed, lock->is<Killed>());
+  }
+#endif
+
+  RefPtr<RemoteWorkerChild> self = this;
+
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      __func__,
+      [self = std::move(self), didCreationSucceed = aDidCreationSucceed] {
+        auto launcherData = self->mLauncherData.Access();
+
+        if (!self->CanSend() || launcherData->mDidSendCreated) {
+          return;
+        }
+
+        Unused << self->SendCreated(didCreationSucceed);
+        launcherData->mDidSendCreated = true;
+      });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+}
+
+void RemoteWorkerChild::CloseWorkerOnMainThread() {
+  AssertIsOnMainThread();
+
+  LOG(("CloseWorkerOnMainThread[this=%p]", this));
+
+  // We can't hold the state lock while calling WorkerPrivate::Cancel because
+  // the lambda callback will want to touch the state, so save off the
+  // WorkerPrivate so we can cancel it (if we need to cancel it).
+  RefPtr<WorkerPrivate> cancelWith;
+  {
+    auto lock = mState.Lock();
+
+    if (lock->is<Pending>()) {
+      cancelWith = lock->as<Pending>().mWorkerPrivate;
+      // There should be no way for this code to run before we
+      // ExecWorkerOnMainThread runs, which means that either it should have
+      // set a WorkerPrivate on Pending, or its error handling should already
+      // have transitioned us to Canceled and Killing in that order.  (It's
+      // also possible that it assigned a WorkerPrivate and subsequently we
+      // transitioned to Running, which would put us in the next branch.)
+      MOZ_DIAGNOSTIC_ASSERT(cancelWith);
+    } else if (lock->is<Running>()) {
+      cancelWith = lock->as<Running>().mWorkerPrivate;
+    }
+  }
+
+  // It's very okay for us to not have a WorkerPrivate here if we've already
+  // canceled the worker or if errors happened.
+  if (cancelWith) {
+    cancelWith->Cancel();
+  }
+}
+
+/**
+ * Error reporting method
+ */
+void RemoteWorkerChild::ErrorPropagation(const ErrorValue& aValue) {
+  MOZ_ASSERT(GetActorEventTarget()->IsOnCurrentThread());
+
+  if (!CanSend()) {
+    return;
+  }
+
+  Unused << SendError(aValue);
+}
+
+void RemoteWorkerChild::ErrorPropagationDispatch(nsresult aError) {
+  MOZ_ASSERT(NS_FAILED(aError));
+
+  RefPtr<RemoteWorkerChild> self = this;
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      "RemoteWorkerChild::ErrorPropagationDispatch",
+      [self = std::move(self), aError]() { self->ErrorPropagation(aError); });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+}
+
+void RemoteWorkerChild::ErrorPropagationOnMainThread(
+    const WorkerErrorReport* aReport, bool aIsErrorEvent) {
+  AssertIsOnMainThread();
+
+  ErrorValue value;
+  if (aIsErrorEvent) {
+    ErrorData data(
+        aReport->mIsWarning, aReport->mLineNumber, aReport->mColumnNumber,
+        aReport->mMessage, aReport->mFilename, aReport->mLine,
+        TransformIntoNewArray(aReport->mNotes, [](const WorkerErrorNote& note) {
+          return ErrorDataNote(note.mLineNumber, note.mColumnNumber,
+                               note.mMessage, note.mFilename);
+        }));
+    value = data;
+  } else {
+    value = void_t();
+  }
+
+  RefPtr<RemoteWorkerChild> self = this;
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      "RemoteWorkerChild::ErrorPropagationOnMainThread",
+      [self = std::move(self), value]() { self->ErrorPropagation(value); });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+}
+
+void RemoteWorkerChild::NotifyLock(bool aCreated) {
+  nsCOMPtr<nsIRunnable> r =
+      NS_NewRunnableFunction(__func__, [self = RefPtr(this), aCreated] {
+        if (!self->CanSend()) {
+          return;
+        }
+
+        Unused << self->SendNotifyLock(aCreated);
+      });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+}
+
+void RemoteWorkerChild::NotifyWebTransport(bool aCreated) {
+  nsCOMPtr<nsIRunnable> r =
+      NS_NewRunnableFunction(__func__, [self = RefPtr(this), aCreated] {
+        if (!self->CanSend()) {
+          return;
+        }
+
+        Unused << self->SendNotifyWebTransport(aCreated);
+      });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+}
+
+void RemoteWorkerChild::FlushReportsOnMainThread(
+    nsIConsoleReportCollector* aReporter) {
+  AssertIsOnMainThread();
+
+  bool reportErrorToBrowserConsole = true;
+
+  // Flush the reports.
+  for (uint32_t i = 0, len = mWindowIDs.Length(); i < len; ++i) {
+    aReporter->FlushReportsToConsole(
+        mWindowIDs[i], nsIConsoleReportCollector::ReportAction::Save);
+    reportErrorToBrowserConsole = false;
+  }
+
+  // Finally report to browser console if there is no any window.
+  if (reportErrorToBrowserConsole) {
+    aReporter->FlushReportsToConsole(0);
+    return;
+  }
+
+  aReporter->ClearConsoleReports();
+}
+
+/**
+ * Worker state transition methods
+ */
+RemoteWorkerChild::WorkerPrivateAccessibleState::
+    ~WorkerPrivateAccessibleState() {
+  // We should now only be performing state transitions on the main thread, so
+  // we should assert we're only releasing on the main thread.
+  MOZ_ASSERT(!mWorkerPrivate || NS_IsMainThread());
+  // mWorkerPrivate can be safely released on the main thread.
+  if (!mWorkerPrivate || NS_IsMainThread()) {
+    return;
+  }
+
+  // But as a backstop, do proxy the release to the main thread.
+  NS_ReleaseOnMainThread(
+      "RemoteWorkerChild::WorkerPrivateAccessibleState::mWorkerPrivate",
+      mWorkerPrivate.forget());
+}
+
+void RemoteWorkerChild::
+    OnWorkerCancellationTransitionStateFromPendingOrRunningToCanceled() {
+  auto lock = mState.Lock();
+
+  LOG(("TransitionStateFromPendingOrRunningToCanceled[this=%p]", this));
+
+  if (lock->is<Pending>()) {
+    TransitionStateFromPendingToCanceled(lock.ref());
+  } else if (lock->is<Running>()) {
+    *lock = VariantType<Canceled>();
+  } else {
+    MOZ_ASSERT(false, "State should have been Pending or Running");
+  }
+}
+
+void RemoteWorkerChild::TransitionStateFromPendingToCanceled(State& aState) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(aState.is<Pending>());
+  LOG(("TransitionStateFromPendingToCanceled[this=%p]", this));
+
+  CancelAllPendingOps(aState);
+
+  aState = VariantType<Canceled>();
+}
+
+void RemoteWorkerChild::TransitionStateFromCanceledToKilled() {
+  AssertIsOnMainThread();
+
+  LOG(("TransitionStateFromCanceledToKilled[this=%p]", this));
+
+  auto lock = mState.Lock();
+  MOZ_ASSERT(lock->is<Canceled>());
+
+  *lock = VariantType<Killed>();
+
+  RefPtr<RemoteWorkerChild> self = this;
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(__func__, [self]() {
+    auto launcherData = self->mLauncherData.Access();
+
+    // (We maintain the historical ordering of resolving this promise prior to
+    // calling SendClose, however the previous code used 2 separate dispatches
+    // to this thread for the resolve and SendClose, and there inherently
+    // would be a race between the runnables resulting from the resolved
+    // promise and the promise containing the call to SendClose.  Now it's
+    // entirely clear that our call to SendClose will effectively run before
+    // any of the resolved promises are able to do anything.)
+    launcherData->mTerminationPromise.ResolveIfExists(true, __func__);
+
+    if (self->CanSend()) {
+      Unused << self->SendClose();
+    }
+  });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+}
+
+void RemoteWorkerChild::TransitionStateToRunning() {
+  AssertIsOnMainThread();
+
+  LOG(("TransitionStateToRunning[this=%p]", this));
+
+  nsTArray<RefPtr<Op>> pendingOps;
+
+  {
+    auto lock = mState.Lock();
+
+    // Because this is an async notification sent from the worker to the main
+    // thread, it's very possible that we've already decided on the main thread
+    // to transition to the Canceled state, in which case there is nothing for
+    // us to do here.
+    if (!lock->is<Pending>()) {
+      LOG(("State is already not pending in TransitionStateToRunning[this=%p]!",
+           this));
+      return;
+    }
+
+    RefPtr<WorkerPrivate> workerPrivate =
+        std::move(lock->as<Pending>().mWorkerPrivate);
+    pendingOps = std::move(lock->as<Pending>().mPendingOps);
+
+    // Move the worker private into place to avoid gratuitous ref churn; prior
+    // comments here suggest the Variant can't accept a move.
+    *lock = VariantType<Running>();
+    lock->as<Running>().mWorkerPrivate = std::move(workerPrivate);
+  }
+
+  CreationSucceededOnAnyThread();
+
+  RefPtr<RemoteWorkerChild> self = this;
+  for (auto& op : pendingOps) {
+    op->StartOnMainThread(self);
+  }
+}
+
+void RemoteWorkerChild::ExceptionalErrorTransitionDuringExecWorker() {
+  AssertIsOnMainThread();
+
+  LOG(("ExceptionalErrorTransitionDuringExecWorker[this=%p]", this));
+
+  // This method is called synchronously by ExecWorkerOnMainThread in the event
+  // of any error.  Because we only transition to Running on the main thread
+  // as the result of a notification from the worker, we know our state will be
+  // Pending, but mWorkerPrivate may or may not be null, as we may not have
+  // gotten to spawning the worker.
+  //
+  // In the event the worker exists, we need to Cancel() it.  We must do this
+  // without the lock held because our call to Cancel() will invoke the
+  // cancellation callback we created which will call TransitionStateToCanceled,
+  // and we can't be holding the lock when that happens.
+
+  RefPtr<WorkerPrivate> cancelWith;
+
+  {
+    auto lock = mState.Lock();
+
+    MOZ_ASSERT(lock->is<Pending>());
+    if (lock->is<Pending>()) {
+      cancelWith = lock->as<Pending>().mWorkerPrivate;
+      if (!cancelWith) {
+        // The worker wasn't actually created, so we should synthetically
+        // transition to canceled and onward.  Since we have the lock,
+        // perform the transition now for clarity, but we'll handle the rest of
+        // this case after dropping the lock.
+        TransitionStateFromPendingToCanceled(lock.ref());
+      }
+    }
+  }
+
+  if (cancelWith) {
+    cancelWith->Cancel();
+  } else {
+    TransitionStateFromCanceledToKilled();
+    CreationFailedOnAnyThread();
+  }
+}
+
+/**
+ * Operation execution classes/methods
+ */
+class RemoteWorkerChild::SharedWorkerOp : public RemoteWorkerChild::Op {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedWorkerOp, override)
+
+  explicit SharedWorkerOp(RemoteWorkerOp&& aOp) : mOp(std::move(aOp)) {}
+
+  bool MaybeStart(RemoteWorkerChild* aOwner,
+                  RemoteWorkerChild::State& aState) override {
+    MOZ_ASSERT(!mStarted);
+    MOZ_ASSERT(aOwner);
+    // Thread: We are on the Worker Launcher thread.
+
+    // Return false, indicating we should queue this op if our current state is
+    // pending and this isn't a termination op (which should skip the line).
+    if (aState.is<Pending>() && !IsTerminationOp()) {
+      return false;
+    }
+
+    // If the worker is already shutting down (which should be unexpected
+    // because we should be told new operations after a termination op), just
+    // return true to indicate the op should be discarded.
+    if (aState.is<Canceled>() || aState.is<Killed>()) {
+#ifdef DEBUG
+      mStarted = true;
+#endif
+
+      return true;
+    }
+
+    MOZ_ASSERT(aState.is<Running>() || IsTerminationOp());
+
+    RefPtr<SharedWorkerOp> self = this;
+    RefPtr<RemoteWorkerChild> owner = aOwner;
+
+    nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+        __func__, [self = std::move(self), owner = std::move(owner)]() mutable {
+          {
+            auto lock = owner->mState.Lock();
+
+            if (NS_WARN_IF(lock->is<Canceled>() || lock->is<Killed>())) {
+              self->Cancel();
+              return;
+            }
+          }
+
+          self->StartOnMainThread(owner);
+        });
+
+    MOZ_ALWAYS_SUCCEEDS(
+        SchedulerGroup::Dispatch(TaskCategory::Other, r.forget()));
+
+#ifdef DEBUG
+    mStarted = true;
+#endif
+
+    return true;
+  }
+
+  void StartOnMainThread(RefPtr<RemoteWorkerChild>& aOwner) final {
+    using Running = RemoteWorkerChild::Running;
+
+    AssertIsOnMainThread();
+
+    if (IsTerminationOp()) {
+      aOwner->CloseWorkerOnMainThread();
+      return;
+    }
+
+    auto lock = aOwner->mState.Lock();
+    MOZ_ASSERT(lock->is<Running>());
+    if (!lock->is<Running>()) {
+      aOwner->ErrorPropagationDispatch(NS_ERROR_DOM_INVALID_STATE_ERR);
+      return;
+    }
+
+    RefPtr<WorkerPrivate> workerPrivate = lock->as<Running>().mWorkerPrivate;
+
+    MOZ_ASSERT(workerPrivate);
+
+    if (mOp.type() == RemoteWorkerOp::TRemoteWorkerSuspendOp) {
+      workerPrivate->ParentWindowPaused();
+    } else if (mOp.type() == RemoteWorkerOp::TRemoteWorkerResumeOp) {
+      workerPrivate->ParentWindowResumed();
+    } else if (mOp.type() == RemoteWorkerOp::TRemoteWorkerFreezeOp) {
+      workerPrivate->Freeze(nullptr);
+    } else if (mOp.type() == RemoteWorkerOp::TRemoteWorkerThawOp) {
+      workerPrivate->Thaw(nullptr);
+    } else if (mOp.type() == RemoteWorkerOp::TRemoteWorkerPortIdentifierOp) {
+      RefPtr<MessagePortIdentifierRunnable> r =
+          new MessagePortIdentifierRunnable(
+              workerPrivate, aOwner,
+              mOp.get_RemoteWorkerPortIdentifierOp().portIdentifier());
+
+      if (NS_WARN_IF(!r->Dispatch())) {
+        aOwner->ErrorPropagationDispatch(NS_ERROR_FAILURE);
+      }
+    } else if (mOp.type() == RemoteWorkerOp::TRemoteWorkerAddWindowIDOp) {
+      aOwner->mWindowIDs.AppendElement(
+          mOp.get_RemoteWorkerAddWindowIDOp().windowID());
+    } else if (mOp.type() == RemoteWorkerOp::TRemoteWorkerRemoveWindowIDOp) {
+      aOwner->mWindowIDs.RemoveElement(
+          mOp.get_RemoteWorkerRemoveWindowIDOp().windowID());
+    } else {
+      MOZ_CRASH("Unknown RemoteWorkerOp type!");
+    }
+  }
+
+  void Cancel() override {
+#ifdef DEBUG
+    mStarted = true;
+#endif
+  }
+
+ private:
+  ~SharedWorkerOp() { MOZ_ASSERT(mStarted); }
+
+  bool IsTerminationOp() const {
+    return mOp.type() == RemoteWorkerOp::TRemoteWorkerTerminateOp;
+  }
+
+  RemoteWorkerOp mOp;
+
+#ifdef DEBUG
+  bool mStarted = false;
+#endif
+};
+
+void RemoteWorkerChild::AddPortIdentifier(
+    JSContext* aCx, WorkerPrivate* aWorkerPrivate,
+    UniqueMessagePortId& aPortIdentifier) {
+  if (NS_WARN_IF(!aWorkerPrivate->ConnectMessagePort(aCx, aPortIdentifier))) {
+    ErrorPropagationDispatch(NS_ERROR_FAILURE);
+  }
+}
+
+void RemoteWorkerChild::CancelAllPendingOps(State& aState) {
+  MOZ_ASSERT(aState.is<Pending>());
+
+  auto pendingOps = std::move(aState.as<Pending>().mPendingOps);
+
+  for (auto& op : pendingOps) {
+    op->Cancel();
+  }
+}
+
+void RemoteWorkerChild::MaybeStartOp(RefPtr<Op>&& aOp) {
+  MOZ_ASSERT(aOp);
+
+  auto lock = mState.Lock();
+
+  if (!aOp->MaybeStart(this, lock.ref())) {
+    // Maybestart returns false only if we are <Pending>.
+    lock->as<Pending>().mPendingOps.AppendElement(std::move(aOp));
+  }
+}
+
+IPCResult RemoteWorkerChild::RecvExecOp(RemoteWorkerOp&& aOp) {
+  MOZ_ASSERT(!mIsServiceWorker);
+
+  MaybeStartOp(new SharedWorkerOp(std::move(aOp)));
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerChild::RecvExecServiceWorkerOp(
+    ServiceWorkerOpArgs&& aArgs, ExecServiceWorkerOpResolver&& aResolve) {
+  MOZ_ASSERT(mIsServiceWorker);
+  MOZ_ASSERT(
+      aArgs.type() !=
+          ServiceWorkerOpArgs::TParentToChildServiceWorkerFetchEventOpArgs,
+      "FetchEvent operations should be sent via PFetchEventOp(Proxy) actors!");
+
+  MaybeReportServiceWorkerShutdownProgress(aArgs);
+
+  MaybeStartOp(ServiceWorkerOp::Create(std::move(aArgs), std::move(aResolve)));
+
+  return IPC_OK();
+}
+
+RefPtr<GenericPromise>
+RemoteWorkerChild::MaybeSendSetServiceWorkerSkipWaitingFlag() {
+  RefPtr<GenericPromise::Private> promise =
+      new GenericPromise::Private(__func__);
+
+  RefPtr<RemoteWorkerChild> self = this;
+
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(__func__, [self = std::move(
+                                                                  self),
+                                                              promise] {
+    if (!self->CanSend()) {
+      promise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+      return;
+    }
+
+    self->SendSetServiceWorkerSkipWaitingFlag()->Then(
+        GetCurrentSerialEventTarget(), __func__,
+        [promise](
+            const SetServiceWorkerSkipWaitingFlagPromise::ResolveOrRejectValue&
+                aResult) {
+          if (NS_WARN_IF(aResult.IsReject())) {
+            promise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+            return;
+          }
+
+          promise->Resolve(aResult.ResolveValue(), __func__);
+        });
+  });
+
+  GetActorEventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+
+  return promise;
+}
+
+/**
+ * PFetchEventOpProxy methods
+ */
+already_AddRefed<PFetchEventOpProxyChild>
+RemoteWorkerChild::AllocPFetchEventOpProxyChild(
+    const ParentToChildServiceWorkerFetchEventOpArgs& aArgs) {
+  return RefPtr{new FetchEventOpProxyChild()}.forget();
+}
+
+IPCResult RemoteWorkerChild::RecvPFetchEventOpProxyConstructor(
+    PFetchEventOpProxyChild* aActor,
+    const ParentToChildServiceWorkerFetchEventOpArgs& aArgs) {
+  MOZ_ASSERT(aActor);
+
+  (static_cast<FetchEventOpProxyChild*>(aActor))->Initialize(aArgs);
+
+  return IPC_OK();
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerChild.h b/dom/workers/remoteworkers/RemoteWorkerChild.h
new file mode 100644
index 0000000000..78fc43246e
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerChild.h
@@ -0,0 +1,237 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_RemoteWorkerChild_h
+#define mozilla_dom_RemoteWorkerChild_h
+
+#include "nsCOMPtr.h"
+#include "nsISupportsImpl.h"
+#include "nsTArray.h"
+
+#include "mozilla/DataMutex.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ThreadBound.h"
+#include "mozilla/dom/PRemoteWorkerChild.h"
+#include "mozilla/dom/ServiceWorkerOpArgs.h"
+
+class nsISerialEventTarget;
+class nsIConsoleReportCollector;
+
+namespace mozilla::dom {
+
+class ErrorValue;
+class FetchEventOpProxyChild;
+class RemoteWorkerData;
+class RemoteWorkerServiceKeepAlive;
+class ServiceWorkerOp;
+class UniqueMessagePortId;
+class WeakWorkerRef;
+class WorkerErrorReport;
+class WorkerPrivate;
+
+/**
+ * Background-managed "Worker Launcher"-thread-resident created via the
+ * RemoteWorkerManager to actually spawn the worker. Currently, the worker will
+ * be spawned from the main thread due to nsIPrincipal not being able to be
+ * created on background threads and other ownership invariants, most of which
+ * can be relaxed in the future.
+ */
+class RemoteWorkerChild final : public PRemoteWorkerChild {
+  friend class FetchEventOpProxyChild;
+  friend class PRemoteWorkerChild;
+  friend class ServiceWorkerOp;
+
+  ~RemoteWorkerChild();
+
+ public:
+  // Note that all IPC-using methods must only be invoked on the
+  // RemoteWorkerService thread which the inherited
+  // IProtocol::GetActorEventTarget() will return for us.
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RemoteWorkerChild, final)
+
+  explicit RemoteWorkerChild(const RemoteWorkerData& aData);
+
+  void ExecWorker(const RemoteWorkerData& aData);
+
+  void ErrorPropagationOnMainThread(const WorkerErrorReport* aReport,
+                                    bool aIsErrorEvent);
+
+  void NotifyLock(bool aCreated);
+
+  void NotifyWebTransport(bool aCreated);
+
+  void FlushReportsOnMainThread(nsIConsoleReportCollector* aReporter);
+
+  void AddPortIdentifier(JSContext* aCx, WorkerPrivate* aWorkerPrivate,
+                         UniqueMessagePortId& aPortIdentifier);
+
+  RefPtr<GenericNonExclusivePromise> GetTerminationPromise();
+
+  RefPtr<GenericPromise> MaybeSendSetServiceWorkerSkipWaitingFlag();
+
+  const nsTArray<uint64_t>& WindowIDs() const { return mWindowIDs; }
+
+ private:
+  class InitializeWorkerRunnable;
+
+  class Op;
+  class SharedWorkerOp;
+
+  struct WorkerPrivateAccessibleState {
+    ~WorkerPrivateAccessibleState();
+    RefPtr<WorkerPrivate> mWorkerPrivate;
+  };
+
+  // Initial state, mWorkerPrivate is initially null but will be initialized on
+  // the main thread by ExecWorkerOnMainThread when the WorkerPrivate is
+  // created.  The state will transition to Running or Canceled, also from the
+  // main thread.
+  struct Pending : WorkerPrivateAccessibleState {
+    nsTArray<RefPtr<Op>> mPendingOps;
+  };
+
+  // Running, with the state transition happening on the main thread as a result
+  // of the worker successfully processing our initialization runnable,
+  // indicating that top-level script execution successfully completed.  Because
+  // all of our state transitions happen on the main thread and are posed in
+  // terms of the main thread's perspective of the worker's state, it's very
+  // possible for us to skip directly from Pending to Canceled because we decide
+  // to cancel/terminate the worker prior to it finishing script loading or
+  // reporting back to us.
+  struct Running : WorkerPrivateAccessibleState {};
+
+  // Cancel() has been called on the WorkerPrivate on the main thread by a
+  // TerminationOp, top-level script evaluation has failed and canceled the
+  // worker, or in the case of a SharedWorker, close() has been called on
+  // the global scope by content code and the worker has advanced to the
+  // Canceling state.  (Dedicated Workers can also self close, but they will
+  // never be RemoteWorkers.  Although a SharedWorker can own DedicatedWorkers.)
+  // Browser shutdown will result in a TerminationOp thanks to use of a shutdown
+  // blocker in the parent, so the RuntimeService shouldn't get involved, but we
+  // would also handle that case acceptably too.
+  //
+  // Because worker self-closing is still handled by dispatching a runnable to
+  // the main thread to effectively call WorkerPrivate::Cancel(), there isn't
+  // a race between a worker deciding to self-close and our termination ops.
+  //
+  // In this state, we have dropped the reference to the WorkerPrivate and will
+  // no longer be dispatching runnables to the worker.  We wait in this state
+  // until the termination lambda is invoked letting us know that the worker has
+  // entirely shutdown and we can advanced to the Killed state.
+  struct Canceled {};
+
+  // The worker termination lambda has been invoked and we know the Worker is
+  // entirely shutdown.  (Inherently it is possible for us to advance to this
+  // state while the nsThread for the worker is still in the process of
+  // shutting down, but no more worker code will run on it.)
+  //
+  // This name is chosen to match the Worker's own state model.
+  struct Killed {};
+
+  using State = Variant<Pending, Running, Canceled, Killed>;
+
+  // The state of the WorkerPrivate as perceived by the owner on the main
+  // thread.  All state transitions now happen on the main thread, but the
+  // Worker Launcher thread will consult the state and will directly append ops
+  // to the Pending queue
+  DataMutex<State> mState;
+
+  const RefPtr<RemoteWorkerServiceKeepAlive> mServiceKeepAlive;
+
+  class Op {
+   public:
+    NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+    virtual ~Op() = default;
+
+    virtual bool MaybeStart(RemoteWorkerChild* aOwner, State& aState) = 0;
+
+    virtual void StartOnMainThread(RefPtr<RemoteWorkerChild>& aOwner) = 0;
+
+    virtual void Cancel() = 0;
+  };
+
+  void ActorDestroy(ActorDestroyReason) override;
+
+  mozilla::ipc::IPCResult RecvExecOp(RemoteWorkerOp&& aOp);
+
+  mozilla::ipc::IPCResult RecvExecServiceWorkerOp(
+      ServiceWorkerOpArgs&& aArgs, ExecServiceWorkerOpResolver&& aResolve);
+
+  already_AddRefed<PFetchEventOpProxyChild> AllocPFetchEventOpProxyChild(
+      const ParentToChildServiceWorkerFetchEventOpArgs& aArgs);
+
+  mozilla::ipc::IPCResult RecvPFetchEventOpProxyConstructor(
+      PFetchEventOpProxyChild* aActor,
+      const ParentToChildServiceWorkerFetchEventOpArgs& aArgs) override;
+
+  nsresult ExecWorkerOnMainThread(RemoteWorkerData&& aData);
+
+  void ExceptionalErrorTransitionDuringExecWorker();
+
+  void RequestWorkerCancellation();
+
+  void InitializeOnWorker();
+
+  void CreationSucceededOnAnyThread();
+
+  void CreationFailedOnAnyThread();
+
+  void CreationSucceededOrFailedOnAnyThread(bool aDidCreationSucceed);
+
+  // Cancels the worker if it has been started and ensures that we transition
+  // to the Terminated state once the worker has been terminated or we have
+  // ensured that it will never start.
+  void CloseWorkerOnMainThread();
+
+  void ErrorPropagation(const ErrorValue& aValue);
+
+  void ErrorPropagationDispatch(nsresult aError);
+
+  // When the WorkerPrivate Cancellation lambda is invoked, it's possible that
+  // we have not yet advanced to running from pending, so we could be in either
+  // state.  This method is expected to be called by the Workers' cancellation
+  // lambda and will obtain the lock and call the
+  // TransitionStateFromPendingToCanceled if appropriate.  Otherwise it will
+  // directly move from the running state to the canceled state which does not
+  // require additional cleanup.
+  void OnWorkerCancellationTransitionStateFromPendingOrRunningToCanceled();
+  // A helper used by the above method by the worker cancellation lambda if the
+  // the worker hasn't started running, or in exceptional cases where we bail
+  // out of the ExecWorker method early.  The caller must be holding the lock
+  // (in order to pass in the state).
+  void TransitionStateFromPendingToCanceled(State& aState);
+  void TransitionStateFromCanceledToKilled();
+
+  void TransitionStateToRunning();
+
+  void TransitionStateToTerminated();
+
+  void TransitionStateToTerminated(State& aState);
+
+  void CancelAllPendingOps(State& aState);
+
+  void MaybeStartOp(RefPtr<Op>&& aOp);
+
+  const bool mIsServiceWorker;
+
+  // Touched on main-thread only.
+  nsTArray<uint64_t> mWindowIDs;
+
+  struct LauncherBoundData {
+    MozPromiseHolder<GenericNonExclusivePromise> mTerminationPromise;
+    // Flag to ensure we report creation at most once.  This could be cleaned up
+    // further.
+    bool mDidSendCreated = false;
+  };
+
+  ThreadBound<LauncherBoundData> mLauncherData;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerChild_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerController.cpp b/dom/workers/remoteworkers/RemoteWorkerController.cpp
new file mode 100644
index 0000000000..b0d56aa33d
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerController.cpp
@@ -0,0 +1,573 @@
+/* -*- 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 "RemoteWorkerController.h"
+
+#include <utility>
+
+#include "nsDebug.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RemoteLazyInputStreamStorage.h"
+#include "mozilla/dom/FetchEventOpParent.h"
+#include "mozilla/dom/FetchEventOpProxyParent.h"
+#include "mozilla/dom/MessagePortParent.h"
+#include "mozilla/dom/RemoteWorkerTypes.h"
+#include "mozilla/dom/ServiceWorkerCloneData.h"
+#include "mozilla/dom/ServiceWorkerShutdownState.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "RemoteWorkerControllerParent.h"
+#include "RemoteWorkerManager.h"
+#include "RemoteWorkerParent.h"
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+/* static */
+already_AddRefed<RemoteWorkerController> RemoteWorkerController::Create(
+    const RemoteWorkerData& aData, RemoteWorkerObserver* aObserver,
+    base::ProcessId aProcessId) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aObserver);
+
+  RefPtr<RemoteWorkerController> controller =
+      new RemoteWorkerController(aData, aObserver);
+
+  RefPtr<RemoteWorkerManager> manager = RemoteWorkerManager::GetOrCreate();
+  MOZ_ASSERT(manager);
+
+  // XXX: We do not check for failure here, should we?
+  manager->Launch(controller, aData, aProcessId);
+
+  return controller.forget();
+}
+
+RemoteWorkerController::RemoteWorkerController(const RemoteWorkerData& aData,
+                                               RemoteWorkerObserver* aObserver)
+    : mObserver(aObserver),
+      mState(ePending),
+      mIsServiceWorker(aData.serviceWorkerData().type() ==
+                       OptionalServiceWorkerData::TServiceWorkerData) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+}
+
+RemoteWorkerController::~RemoteWorkerController() {
+  AssertIsOnBackgroundThread();
+  MOZ_DIAGNOSTIC_ASSERT(mPendingOps.IsEmpty());
+}
+
+void RemoteWorkerController::SetWorkerActor(RemoteWorkerParent* aActor) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mActor);
+  MOZ_ASSERT(aActor);
+
+  mActor = aActor;
+}
+
+void RemoteWorkerController::NoteDeadWorkerActor() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mActor);
+
+  // The actor has been destroyed without a proper close() notification. Let's
+  // inform the observer.
+  if (mState == eReady) {
+    mObserver->Terminated();
+  }
+
+  mActor = nullptr;
+
+  Shutdown();
+}
+
+void RemoteWorkerController::CreationFailed() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+  MOZ_ASSERT(mState == ePending || mState == eTerminated);
+
+  if (mState == eTerminated) {
+    MOZ_ASSERT(!mActor);
+    MOZ_ASSERT(mPendingOps.IsEmpty());
+    // Nothing to do.
+    return;
+  }
+
+  NoteDeadWorker();
+
+  mObserver->CreationFailed();
+}
+
+void RemoteWorkerController::CreationSucceeded() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mState == ePending || mState == eTerminated);
+
+  if (mState == eTerminated) {
+    MOZ_ASSERT(!mActor);
+    MOZ_ASSERT(mPendingOps.IsEmpty());
+    // Nothing to do.
+    return;
+  }
+
+  MOZ_ASSERT(mActor);
+  mState = eReady;
+
+  mObserver->CreationSucceeded();
+
+  auto pendingOps = std::move(mPendingOps);
+
+  for (auto& op : pendingOps) {
+    DebugOnly<bool> started = op->MaybeStart(this);
+    MOZ_ASSERT(started);
+  }
+}
+
+void RemoteWorkerController::ErrorPropagation(const ErrorValue& aValue) {
+  AssertIsOnBackgroundThread();
+
+  mObserver->ErrorReceived(aValue);
+}
+
+void RemoteWorkerController::NotifyLock(bool aCreated) {
+  AssertIsOnBackgroundThread();
+
+  mObserver->LockNotified(aCreated);
+}
+
+void RemoteWorkerController::NotifyWebTransport(bool aCreated) {
+  AssertIsOnBackgroundThread();
+
+  mObserver->WebTransportNotified(aCreated);
+}
+
+void RemoteWorkerController::WorkerTerminated() {
+  AssertIsOnBackgroundThread();
+
+  NoteDeadWorker();
+
+  mObserver->Terminated();
+}
+
+void RemoteWorkerController::CancelAllPendingOps() {
+  AssertIsOnBackgroundThread();
+
+  auto pendingOps = std::move(mPendingOps);
+
+  for (auto& op : pendingOps) {
+    op->Cancel();
+  }
+}
+
+void RemoteWorkerController::Shutdown() {
+  AssertIsOnBackgroundThread();
+  Unused << NS_WARN_IF(mIsServiceWorker && !mPendingOps.IsEmpty());
+
+  if (mState == eTerminated) {
+    MOZ_ASSERT(mPendingOps.IsEmpty());
+    return;
+  }
+
+  mState = eTerminated;
+
+  CancelAllPendingOps();
+
+  if (!mActor) {
+    return;
+  }
+
+  mActor->SetController(nullptr);
+
+  /**
+   * The "non-remote-side" of the Service Worker will have ensured that the
+   * remote worker is terminated before calling `Shutdown().`
+   */
+  if (mIsServiceWorker) {
+    mActor->MaybeSendDelete();
+  } else {
+    Unused << mActor->SendExecOp(RemoteWorkerTerminateOp());
+  }
+
+  mActor = nullptr;
+}
+
+void RemoteWorkerController::NoteDeadWorker() {
+  AssertIsOnBackgroundThread();
+
+  CancelAllPendingOps();
+
+  /**
+   * The "non-remote-side" of the Service Worker will initiate `Shutdown()`
+   * once it's notified that all dispatched operations have either completed
+   * or canceled. That is, it'll explicitly call `Shutdown()` later.
+   */
+  if (!mIsServiceWorker) {
+    Shutdown();
+  }
+}
+
+template <typename... Args>
+void RemoteWorkerController::MaybeStartSharedWorkerOp(Args&&... aArgs) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mIsServiceWorker);
+
+  UniquePtr<PendingSharedWorkerOp> op =
+      MakeUnique<PendingSharedWorkerOp>(std::forward<Args>(aArgs)...);
+
+  if (!op->MaybeStart(this)) {
+    mPendingOps.AppendElement(std::move(op));
+  }
+}
+
+void RemoteWorkerController::AddWindowID(uint64_t aWindowID) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aWindowID);
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eAddWindowID, aWindowID);
+}
+
+void RemoteWorkerController::RemoveWindowID(uint64_t aWindowID) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aWindowID);
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eRemoveWindowID, aWindowID);
+}
+
+void RemoteWorkerController::AddPortIdentifier(
+    const MessagePortIdentifier& aPortIdentifier) {
+  AssertIsOnBackgroundThread();
+
+  MaybeStartSharedWorkerOp(aPortIdentifier);
+}
+
+void RemoteWorkerController::Terminate() {
+  AssertIsOnBackgroundThread();
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eTerminate);
+}
+
+void RemoteWorkerController::Suspend() {
+  AssertIsOnBackgroundThread();
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eSuspend);
+}
+
+void RemoteWorkerController::Resume() {
+  AssertIsOnBackgroundThread();
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eResume);
+}
+
+void RemoteWorkerController::Freeze() {
+  AssertIsOnBackgroundThread();
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eFreeze);
+}
+
+void RemoteWorkerController::Thaw() {
+  AssertIsOnBackgroundThread();
+
+  MaybeStartSharedWorkerOp(PendingSharedWorkerOp::eThaw);
+}
+
+RefPtr<ServiceWorkerOpPromise> RemoteWorkerController::ExecServiceWorkerOp(
+    ServiceWorkerOpArgs&& aArgs) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mIsServiceWorker);
+
+  RefPtr<ServiceWorkerOpPromise::Private> promise =
+      new ServiceWorkerOpPromise::Private(__func__);
+
+  UniquePtr<PendingServiceWorkerOp> op =
+      MakeUnique<PendingServiceWorkerOp>(std::move(aArgs), promise);
+
+  if (!op->MaybeStart(this)) {
+    mPendingOps.AppendElement(std::move(op));
+  }
+
+  return promise;
+}
+
+RefPtr<ServiceWorkerFetchEventOpPromise>
+RemoteWorkerController::ExecServiceWorkerFetchEventOp(
+    const ParentToParentServiceWorkerFetchEventOpArgs& aArgs,
+    RefPtr<FetchEventOpParent> aReal) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mIsServiceWorker);
+
+  RefPtr<ServiceWorkerFetchEventOpPromise::Private> promise =
+      new ServiceWorkerFetchEventOpPromise::Private(__func__);
+
+  UniquePtr<PendingSWFetchEventOp> op =
+      MakeUnique<PendingSWFetchEventOp>(aArgs, promise, std::move(aReal));
+
+  if (!op->MaybeStart(this)) {
+    mPendingOps.AppendElement(std::move(op));
+  }
+
+  return promise;
+}
+
+RefPtr<GenericPromise> RemoteWorkerController::SetServiceWorkerSkipWaitingFlag()
+    const {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mObserver);
+
+  RefPtr<GenericPromise::Private> promise =
+      new GenericPromise::Private(__func__);
+
+  static_cast<RemoteWorkerControllerParent*>(mObserver.get())
+      ->MaybeSendSetServiceWorkerSkipWaitingFlag(
+          [promise](bool aOk) { promise->Resolve(aOk, __func__); });
+
+  return promise;
+}
+
+bool RemoteWorkerController::IsTerminated() const {
+  return mState == eTerminated;
+}
+
+RemoteWorkerController::PendingSharedWorkerOp::PendingSharedWorkerOp(
+    Type aType, uint64_t aWindowID)
+    : mType(aType), mWindowID(aWindowID) {
+  AssertIsOnBackgroundThread();
+}
+
+RemoteWorkerController::PendingSharedWorkerOp::PendingSharedWorkerOp(
+    const MessagePortIdentifier& aPortIdentifier)
+    : mType(ePortIdentifier), mPortIdentifier(aPortIdentifier) {
+  AssertIsOnBackgroundThread();
+}
+
+RemoteWorkerController::PendingSharedWorkerOp::~PendingSharedWorkerOp() {
+  AssertIsOnBackgroundThread();
+  MOZ_DIAGNOSTIC_ASSERT(mCompleted);
+}
+
+bool RemoteWorkerController::PendingSharedWorkerOp::MaybeStart(
+    RemoteWorkerController* const aOwner) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mCompleted);
+  MOZ_ASSERT(aOwner);
+
+  if (aOwner->mState == RemoteWorkerController::eTerminated) {
+    Cancel();
+    return true;
+  }
+
+  if (aOwner->mState == RemoteWorkerController::ePending &&
+      mType != eTerminate) {
+    return false;
+  }
+
+  switch (mType) {
+    case eTerminate:
+      aOwner->Shutdown();
+      break;
+    case eSuspend:
+      Unused << aOwner->mActor->SendExecOp(RemoteWorkerSuspendOp());
+      break;
+    case eResume:
+      Unused << aOwner->mActor->SendExecOp(RemoteWorkerResumeOp());
+      break;
+    case eFreeze:
+      Unused << aOwner->mActor->SendExecOp(RemoteWorkerFreezeOp());
+      break;
+    case eThaw:
+      Unused << aOwner->mActor->SendExecOp(RemoteWorkerThawOp());
+      break;
+    case ePortIdentifier:
+      Unused << aOwner->mActor->SendExecOp(
+          RemoteWorkerPortIdentifierOp(mPortIdentifier));
+      break;
+    case eAddWindowID:
+      Unused << aOwner->mActor->SendExecOp(
+          RemoteWorkerAddWindowIDOp(mWindowID));
+      break;
+    case eRemoveWindowID:
+      Unused << aOwner->mActor->SendExecOp(
+          RemoteWorkerRemoveWindowIDOp(mWindowID));
+      break;
+    default:
+      MOZ_CRASH("Unknown op.");
+  }
+
+  mCompleted = true;
+
+  return true;
+}
+
+void RemoteWorkerController::PendingSharedWorkerOp::Cancel() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mCompleted);
+
+  // We don't want to leak the port if the operation has not been processed.
+  if (mType == ePortIdentifier) {
+    MessagePortParent::ForceClose(mPortIdentifier.uuid(),
+                                  mPortIdentifier.destinationUuid(),
+                                  mPortIdentifier.sequenceId());
+  }
+
+  mCompleted = true;
+}
+
+RemoteWorkerController::PendingServiceWorkerOp::PendingServiceWorkerOp(
+    ServiceWorkerOpArgs&& aArgs,
+    RefPtr<ServiceWorkerOpPromise::Private> aPromise)
+    : mArgs(std::move(aArgs)), mPromise(std::move(aPromise)) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mPromise);
+}
+
+RemoteWorkerController::PendingServiceWorkerOp::~PendingServiceWorkerOp() {
+  AssertIsOnBackgroundThread();
+  MOZ_DIAGNOSTIC_ASSERT(!mPromise);
+}
+
+bool RemoteWorkerController::PendingServiceWorkerOp::MaybeStart(
+    RemoteWorkerController* const aOwner) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mPromise);
+  MOZ_ASSERT(aOwner);
+
+  if (NS_WARN_IF(aOwner->mState == RemoteWorkerController::eTerminated)) {
+    mPromise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+    mPromise = nullptr;
+    return true;
+  }
+
+  // The target content process must still be starting up.
+  if (!aOwner->mActor) {
+    // We can avoid starting the worker at all if we know it should be
+    // terminated.
+    MOZ_ASSERT(aOwner->mState == RemoteWorkerController::ePending);
+    if (mArgs.type() ==
+        ServiceWorkerOpArgs::TServiceWorkerTerminateWorkerOpArgs) {
+      aOwner->CancelAllPendingOps();
+      Cancel();
+
+      aOwner->mState = RemoteWorkerController::eTerminated;
+
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * Allow termination operations to pass through while pending because the
+   * remote Service Worker can be terminated while still starting up.
+   */
+  if (aOwner->mState == RemoteWorkerController::ePending &&
+      mArgs.type() !=
+          ServiceWorkerOpArgs::TServiceWorkerTerminateWorkerOpArgs) {
+    return false;
+  }
+
+  MaybeReportServiceWorkerShutdownProgress(mArgs);
+
+  aOwner->mActor->SendExecServiceWorkerOp(mArgs)->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [promise = std::move(mPromise)](
+          PRemoteWorkerParent::ExecServiceWorkerOpPromise::
+              ResolveOrRejectValue&& aResult) {
+        if (NS_WARN_IF(aResult.IsReject())) {
+          promise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+          return;
+        }
+
+        promise->Resolve(std::move(aResult.ResolveValue()), __func__);
+      });
+
+  return true;
+}
+
+void RemoteWorkerController::PendingServiceWorkerOp::Cancel() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mPromise);
+
+  mPromise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+  mPromise = nullptr;
+}
+
+RemoteWorkerController::PendingSWFetchEventOp::PendingSWFetchEventOp(
+    const ParentToParentServiceWorkerFetchEventOpArgs& aArgs,
+    RefPtr<ServiceWorkerFetchEventOpPromise::Private> aPromise,
+    RefPtr<FetchEventOpParent>&& aReal)
+    : mArgs(aArgs), mPromise(std::move(aPromise)), mReal(aReal) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mPromise);
+
+  // If there is a TParentToParentStream in the request body, we need to
+  // save it to our stream.
+  IPCInternalRequest& req = mArgs.common().internalRequest();
+  if (req.body().isSome() &&
+      req.body().ref().type() == BodyStreamVariant::TParentToParentStream) {
+    nsCOMPtr<nsIInputStream> stream;
+    auto streamLength = req.bodySize();
+    const auto& uuid = req.body().ref().get_ParentToParentStream().uuid();
+
+    auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+    MOZ_DIAGNOSTIC_ASSERT(storage);
+    storage->GetStream(uuid, 0, streamLength, getter_AddRefs(mBodyStream));
+    storage->ForgetStream(uuid);
+
+    MOZ_DIAGNOSTIC_ASSERT(mBodyStream);
+
+    req.body() = Nothing();
+  }
+}
+
+RemoteWorkerController::PendingSWFetchEventOp::~PendingSWFetchEventOp() {
+  AssertIsOnBackgroundThread();
+  MOZ_DIAGNOSTIC_ASSERT(!mPromise);
+}
+
+bool RemoteWorkerController::PendingSWFetchEventOp::MaybeStart(
+    RemoteWorkerController* const aOwner) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mPromise);
+  MOZ_ASSERT(aOwner);
+
+  if (NS_WARN_IF(aOwner->mState == RemoteWorkerController::eTerminated)) {
+    mPromise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+    mPromise = nullptr;
+    // Because the worker has transitioned to terminated, this operation is moot
+    // and so we should return true because there's no need to queue it.
+    return true;
+  }
+
+  // The target content process must still be starting up.
+  if (!aOwner->mActor) {
+    MOZ_ASSERT(aOwner->mState == RemoteWorkerController::ePending);
+    return false;
+  }
+
+  // At this point we are handing off responsibility for the promise to the
+  // actor.
+  FetchEventOpProxyParent::Create(aOwner->mActor.get(), std::move(mPromise),
+                                  mArgs, std::move(mReal),
+                                  std::move(mBodyStream));
+
+  return true;
+}
+
+void RemoteWorkerController::PendingSWFetchEventOp::Cancel() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mPromise);
+
+  if (mPromise) {
+    mPromise->Reject(NS_ERROR_DOM_ABORT_ERR, __func__);
+    mPromise = nullptr;
+  }
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerController.h b/dom/workers/remoteworkers/RemoteWorkerController.h
new file mode 100644
index 0000000000..af53634abd
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerController.h
@@ -0,0 +1,323 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_RemoteWorkerController_h
+#define mozilla_dom_RemoteWorkerController_h
+
+#include "nsISupportsImpl.h"
+#include "nsTArray.h"
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/dom/DOMTypes.h"
+#include "mozilla/dom/ServiceWorkerOpArgs.h"
+#include "mozilla/dom/ServiceWorkerOpPromise.h"
+
+namespace mozilla::dom {
+
+/* Here's a graph about this remote workers are spawned.
+ *
+ *  _________________________________    |   ________________________________
+ * |                                 |   |  |                                |
+ * |              Parent process     |  IPC |          Creation of Process X |
+ * |              PBackground thread |   |  |                                |
+ * |                                 |   |  | [RemoteWorkerService::Init()]  |
+ * |                                 |   |  |               |                |
+ * |                                 |   |  |               | (1)            |
+ * | [RemoteWorkerManager::  (2)     |   |  |               V                |
+ * |                RegisterActor()]<-------- [new RemoteWorkerServiceChild] |
+ * |                                 |   |  |                                |
+ * |  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~   |   |  |________________________________|
+ * |                                 |   |
+ * |  new SharedWorker/ServiceWorker |   |
+ * |      |     ^                    |  IPC
+ * |  (3) |  (4)|                    |
+ * |      V     |                    |   |
+ * | [RemoteWorkerController::       |   |
+ * |         |         Create(data)] |   |
+ * |         | (5)                   |   |
+ * |         V                       |   |
+ * | [RemoteWorkerManager::Launch()] |   |
+ * |         |                       |  IPC   _____________________________
+ * |         | (6)                   |   |   |                             |
+ * |         |                       |       | Selected content process    |
+ * |         V                       |  (7)  |                             |
+ * | [SendPRemoteWorkerConstructor()]--------->[new RemoteWorkerChild()]   |
+ * |         |                       |   |   |             |               |
+ * |         | (8)                   |   |   |             |               |
+ * |         V                       |   |   |             V               |
+ * | [RemoteWorkerController->       |   |   | RemoteWorkerChild->Exec()   |
+ * |         | SetControllerActor()] |   |   |_____________________________|
+ * |     (9) |                       |  IPC
+ * |         V                       |   |
+ * | [RemoteWorkerObserver->         |   |
+ * |           CreationCompleted()]  |   |
+ * |_________________________________|   |
+ *                                       |
+ *
+ * 1. When a new process starts, it creates a RemoteWorkerService singleton.
+ *    This service creates a new thread (Worker Launcher) and from there, it
+ *    starts a PBackground RemoteWorkerServiceChild actor.
+ * 2. On the parent process, PBackground thread, RemoteWorkerServiceParent
+ *    actors are registered into the RemoteWorkerManager service.
+ *
+ * 3. At some point, a SharedWorker or a ServiceWorker must be executed.
+ *    RemoteWorkerController::Create() is used to start the launching. This
+ *    method must be called on the parent process, on the PBackground thread.
+ * 4. RemoteWorkerController object is immediately returned to the caller. Any
+ *    operation done with this controller object will be stored in a queue,
+ *    until the launching is correctly executed.
+ * 5. RemoteWorkerManager has the list of active RemoteWorkerServiceParent
+ *    actors. From them, it picks one.
+ *    In case we don't have any content process to select, a new one is
+ *    spawned. If this happens, the operation is suspended until a new
+ *    RemoteWorkerServiceParent is registered.
+ * 6. RemoteWorkerServiceParent is used to create a RemoteWorkerParent.
+ * 7. RemoteWorkerChild is created on a selected process and it executes the
+ *    WorkerPrivate.
+ * 8. The RemoteWorkerParent actor is passed to the RemoteWorkerController.
+ * 9. RemoteWorkerController now is ready to continue and it called
+ *    RemoteWorkerObserver to inform that the operation is completed.
+ *    In case there were pending operations, they are now executed.
+ */
+
+class ErrorValue;
+class FetchEventOpParent;
+class RemoteWorkerControllerParent;
+class RemoteWorkerData;
+class RemoteWorkerManager;
+class RemoteWorkerParent;
+
+class RemoteWorkerObserver {
+ public:
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  virtual void CreationFailed() = 0;
+
+  virtual void CreationSucceeded() = 0;
+
+  virtual void ErrorReceived(const ErrorValue& aValue) = 0;
+
+  virtual void LockNotified(bool aCreated) = 0;
+
+  virtual void WebTransportNotified(bool aCreated) = 0;
+
+  virtual void Terminated() = 0;
+};
+
+/**
+ * PBackground instance created by static RemoteWorkerController::Create that
+ * builds on RemoteWorkerManager. Interface to control the remote worker as well
+ * as receive events via the RemoteWorkerObserver interface that the owner
+ * (SharedWorkerManager in this case) must implement to hear about errors,
+ * termination, and whether the initial spawning succeeded/failed.
+ *
+ * Its methods may be called immediately after creation even though the worker
+ * is created asynchronously; an internal operation queue makes this work.
+ * Communicates with the remote worker via owned RemoteWorkerParent over
+ * PRemoteWorker protocol.
+ */
+class RemoteWorkerController final {
+  friend class RemoteWorkerControllerParent;
+  friend class RemoteWorkerManager;
+  friend class RemoteWorkerParent;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerController)
+
+  static already_AddRefed<RemoteWorkerController> Create(
+      const RemoteWorkerData& aData, RemoteWorkerObserver* aObserver,
+      base::ProcessId = 0);
+
+  void AddWindowID(uint64_t aWindowID);
+
+  void RemoveWindowID(uint64_t aWindowID);
+
+  void AddPortIdentifier(const MessagePortIdentifier& aPortIdentifier);
+
+  void Terminate();
+
+  void Suspend();
+
+  void Resume();
+
+  void Freeze();
+
+  void Thaw();
+
+  RefPtr<ServiceWorkerOpPromise> ExecServiceWorkerOp(
+      ServiceWorkerOpArgs&& aArgs);
+
+  RefPtr<ServiceWorkerFetchEventOpPromise> ExecServiceWorkerFetchEventOp(
+      const ParentToParentServiceWorkerFetchEventOpArgs& aArgs,
+      RefPtr<FetchEventOpParent> aReal);
+
+  RefPtr<GenericPromise> SetServiceWorkerSkipWaitingFlag() const;
+
+  bool IsTerminated() const;
+
+  void NotifyWebTransport(bool aCreated);
+
+ private:
+  RemoteWorkerController(const RemoteWorkerData& aData,
+                         RemoteWorkerObserver* aObserver);
+
+  ~RemoteWorkerController();
+
+  void SetWorkerActor(RemoteWorkerParent* aActor);
+
+  void NoteDeadWorkerActor();
+
+  void ErrorPropagation(const ErrorValue& aValue);
+
+  void NotifyLock(bool aCreated);
+
+  void WorkerTerminated();
+
+  void Shutdown();
+
+  void CreationFailed();
+
+  void CreationSucceeded();
+
+  void CancelAllPendingOps();
+
+  template <typename... Args>
+  void MaybeStartSharedWorkerOp(Args&&... aArgs);
+
+  void NoteDeadWorker();
+
+  RefPtr<RemoteWorkerObserver> mObserver;
+  RefPtr<RemoteWorkerParent> mActor;
+
+  enum {
+    ePending,
+    eReady,
+    eTerminated,
+  } mState;
+
+  const bool mIsServiceWorker;
+
+  /**
+   * `PendingOp` is responsible for encapsulating logic for starting and
+   * canceling pending remote worker operations, as this logic may vary
+   * depending on the type of the remote worker and the type of the operation.
+   */
+  class PendingOp {
+   public:
+    PendingOp() = default;
+
+    PendingOp(const PendingOp&) = delete;
+
+    PendingOp& operator=(const PendingOp&) = delete;
+
+    virtual ~PendingOp() = default;
+
+    /**
+     * Returns `true` if execution has started or the operation is moot and
+     * doesn't need to be queued, `false` if execution hasn't started and the
+     * operation should be queued.  In general, operations should only return
+     * false when a remote worker is first starting up.  Operations may also
+     * somewhat non-intuitively return true without doing anything if the worker
+     * has already been told to shutdown.
+     *
+     * Starting execution may depend the state of `aOwner.`
+     */
+    virtual bool MaybeStart(RemoteWorkerController* const aOwner) = 0;
+
+    /**
+     * Invoked if the operation will never have MaybeStart() called again
+     * because the RemoteWorkerController has terminated (or will never start).
+     * This should be used by PendingOps to clean up any resources they own and
+     * may also be called internally by their MaybeStart() methods if they
+     * determine the worker has been terminated.  This should be idempotent.
+     */
+    virtual void Cancel() = 0;
+  };
+
+  class PendingSharedWorkerOp final : public PendingOp {
+   public:
+    enum Type {
+      eTerminate,
+      eSuspend,
+      eResume,
+      eFreeze,
+      eThaw,
+      ePortIdentifier,
+      eAddWindowID,
+      eRemoveWindowID,
+    };
+
+    explicit PendingSharedWorkerOp(Type aType, uint64_t aWindowID = 0);
+
+    explicit PendingSharedWorkerOp(
+        const MessagePortIdentifier& aPortIdentifier);
+
+    ~PendingSharedWorkerOp();
+
+    bool MaybeStart(RemoteWorkerController* const aOwner) override;
+
+    void Cancel() override;
+
+   private:
+    const Type mType;
+    const MessagePortIdentifier mPortIdentifier;
+    const uint64_t mWindowID = 0;
+    bool mCompleted = false;
+  };
+
+  class PendingServiceWorkerOp final : public PendingOp {
+   public:
+    PendingServiceWorkerOp(ServiceWorkerOpArgs&& aArgs,
+                           RefPtr<ServiceWorkerOpPromise::Private> aPromise);
+
+    ~PendingServiceWorkerOp();
+
+    bool MaybeStart(RemoteWorkerController* const aOwner) override;
+
+    void Cancel() override;
+
+   private:
+    ServiceWorkerOpArgs mArgs;
+    RefPtr<ServiceWorkerOpPromise::Private> mPromise;
+  };
+
+  /**
+   * Custom pending op type to deal with the complexities of FetchEvents having
+   * their own actor.
+   *
+   * FetchEvent Ops have their own actor type because their lifecycle is more
+   * complex than IPDL's async return value mechanism allows.  Additionally,
+   * its IPC struct potentially has to serialize RemoteLazyStreams which
+   * requires us to hold an nsIInputStream when at rest and serialize it when
+   * eventually sending.
+   */
+  class PendingSWFetchEventOp final : public PendingOp {
+   public:
+    PendingSWFetchEventOp(
+        const ParentToParentServiceWorkerFetchEventOpArgs& aArgs,
+        RefPtr<ServiceWorkerFetchEventOpPromise::Private> aPromise,
+        RefPtr<FetchEventOpParent>&& aReal);
+
+    ~PendingSWFetchEventOp();
+
+    bool MaybeStart(RemoteWorkerController* const aOwner) override;
+
+    void Cancel() override;
+
+   private:
+    ParentToParentServiceWorkerFetchEventOpArgs mArgs;
+    RefPtr<ServiceWorkerFetchEventOpPromise::Private> mPromise;
+    RefPtr<FetchEventOpParent> mReal;
+    nsCOMPtr<nsIInputStream> mBodyStream;
+  };
+
+  nsTArray<UniquePtr<PendingOp>> mPendingOps;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerController_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerControllerChild.cpp b/dom/workers/remoteworkers/RemoteWorkerControllerChild.cpp
new file mode 100644
index 0000000000..1b7f159fa5
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerControllerChild.cpp
@@ -0,0 +1,149 @@
+/* -*- 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 "RemoteWorkerControllerChild.h"
+
+#include <utility>
+
+#include "MainThreadUtils.h"
+#include "nsError.h"
+#include "nsThreadUtils.h"
+
+#include "ServiceWorkerPrivate.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/PFetchEventOpChild.h"
+
+namespace mozilla {
+
+using ipc::IPCResult;
+
+namespace dom {
+
+RemoteWorkerControllerChild::RemoteWorkerControllerChild(
+    RefPtr<RemoteWorkerObserver> aObserver)
+    : mObserver(std::move(aObserver)) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(mObserver);
+}
+
+PFetchEventOpChild* RemoteWorkerControllerChild::AllocPFetchEventOpChild(
+    const ParentToParentServiceWorkerFetchEventOpArgs& aArgs) {
+  MOZ_CRASH("PFetchEventOpChild actors must be manually constructed!");
+  return nullptr;
+}
+
+bool RemoteWorkerControllerChild::DeallocPFetchEventOpChild(
+    PFetchEventOpChild* aActor) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(aActor);
+
+  delete aActor;
+  return true;
+}
+
+void RemoteWorkerControllerChild::ActorDestroy(ActorDestroyReason aReason) {
+  AssertIsOnMainThread();
+
+  mIPCActive = false;
+
+  if (NS_WARN_IF(mObserver)) {
+    mObserver->ErrorReceived(NS_ERROR_DOM_ABORT_ERR);
+  }
+}
+
+IPCResult RemoteWorkerControllerChild::RecvCreationFailed() {
+  AssertIsOnMainThread();
+
+  if (mObserver) {
+    mObserver->CreationFailed();
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerControllerChild::RecvCreationSucceeded() {
+  AssertIsOnMainThread();
+
+  if (mObserver) {
+    mObserver->CreationSucceeded();
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerControllerChild::RecvErrorReceived(
+    const ErrorValue& aError) {
+  AssertIsOnMainThread();
+
+  if (mObserver) {
+    mObserver->ErrorReceived(aError);
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerControllerChild::RecvTerminated() {
+  AssertIsOnMainThread();
+
+  if (mObserver) {
+    mObserver->Terminated();
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerControllerChild::RecvSetServiceWorkerSkipWaitingFlag(
+    SetServiceWorkerSkipWaitingFlagResolver&& aResolve) {
+  AssertIsOnMainThread();
+
+  if (mObserver) {
+    static_cast<ServiceWorkerPrivate*>(mObserver.get())
+        ->SetSkipWaitingFlag()
+        ->Then(GetCurrentSerialEventTarget(), __func__,
+               [resolve = std::move(aResolve)](
+                   const GenericPromise::ResolveOrRejectValue& aResult) {
+                 resolve(aResult.IsResolve() ? aResult.ResolveValue() : false);
+               });
+
+    return IPC_OK();
+  }
+
+  aResolve(false);
+
+  return IPC_OK();
+}
+
+void RemoteWorkerControllerChild::RevokeObserver(
+    RemoteWorkerObserver* aObserver) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(aObserver);
+  MOZ_ASSERT(aObserver == mObserver);
+
+  mObserver = nullptr;
+}
+
+void RemoteWorkerControllerChild::MaybeSendDelete() {
+  AssertIsOnMainThread();
+
+  if (!mIPCActive) {
+    return;
+  }
+
+  RefPtr<RemoteWorkerControllerChild> self = this;
+
+  SendShutdown()->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [self = std::move(self)](const ShutdownPromise::ResolveOrRejectValue&) {
+        if (self->mIPCActive) {
+          Unused << self->Send__delete__(self);
+        }
+      });
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerControllerChild.h b/dom/workers/remoteworkers/RemoteWorkerControllerChild.h
new file mode 100644
index 0000000000..049d67ad56
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerControllerChild.h
@@ -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/. */
+
+#ifndef mozilla_dom_remoteworkercontrollerchild_h__
+#define mozilla_dom_remoteworkercontrollerchild_h__
+
+#include "nsISupportsImpl.h"
+
+#include "RemoteWorkerController.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/PRemoteWorkerControllerChild.h"
+
+namespace mozilla::dom {
+
+/**
+ * Parent-process main-thread proxy used by ServiceWorkerManager to control
+ * RemoteWorkerController instances on the parent-process PBackground thread.
+ */
+class RemoteWorkerControllerChild final : public PRemoteWorkerControllerChild {
+  friend class PRemoteWorkerControllerChild;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerControllerChild)
+
+  explicit RemoteWorkerControllerChild(RefPtr<RemoteWorkerObserver> aObserver);
+
+  void Initialize();
+
+  void RevokeObserver(RemoteWorkerObserver* aObserver);
+
+  void MaybeSendDelete();
+
+ private:
+  ~RemoteWorkerControllerChild() = default;
+
+  PFetchEventOpChild* AllocPFetchEventOpChild(
+      const ParentToParentServiceWorkerFetchEventOpArgs& aArgs);
+
+  bool DeallocPFetchEventOpChild(PFetchEventOpChild* aActor);
+
+  void ActorDestroy(ActorDestroyReason aReason) override;
+
+  mozilla::ipc::IPCResult RecvCreationFailed();
+
+  mozilla::ipc::IPCResult RecvCreationSucceeded();
+
+  mozilla::ipc::IPCResult RecvErrorReceived(const ErrorValue& aError);
+
+  mozilla::ipc::IPCResult RecvTerminated();
+
+  mozilla::ipc::IPCResult RecvSetServiceWorkerSkipWaitingFlag(
+      SetServiceWorkerSkipWaitingFlagResolver&& aResolve);
+
+  RefPtr<RemoteWorkerObserver> mObserver;
+
+  bool mIPCActive = true;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_remoteworkercontrollerchild_h__
diff --git a/dom/workers/remoteworkers/RemoteWorkerControllerParent.cpp b/dom/workers/remoteworkers/RemoteWorkerControllerParent.cpp
new file mode 100644
index 0000000000..7ac901f655
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerControllerParent.cpp
@@ -0,0 +1,215 @@
+/* -*- 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 "RemoteWorkerControllerParent.h"
+
+#include <utility>
+
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsThreadUtils.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/FetchEventOpParent.h"
+#include "mozilla/dom/RemoteWorkerParent.h"
+#include "mozilla/dom/ServiceWorkerOpPromise.h"
+#include "mozilla/ipc/BackgroundParent.h"
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+RemoteWorkerControllerParent::RemoteWorkerControllerParent(
+    const RemoteWorkerData& aRemoteWorkerData)
+    : mRemoteWorkerController(RemoteWorkerController::Create(
+          aRemoteWorkerData, this, 0 /* random process ID */)) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mRemoteWorkerController);
+}
+
+RefPtr<RemoteWorkerParent> RemoteWorkerControllerParent::GetRemoteWorkerParent()
+    const {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mRemoteWorkerController);
+
+  return mRemoteWorkerController->mActor;
+}
+
+void RemoteWorkerControllerParent::MaybeSendSetServiceWorkerSkipWaitingFlag(
+    std::function<void(bool)>&& aCallback) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aCallback);
+
+  if (!mIPCActive) {
+    aCallback(false);
+    return;
+  }
+
+  SendSetServiceWorkerSkipWaitingFlag()->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [callback = std::move(aCallback)](
+          const SetServiceWorkerSkipWaitingFlagPromise::ResolveOrRejectValue&
+              aResult) {
+        callback(aResult.IsResolve() ? aResult.ResolveValue() : false);
+      });
+}
+
+RemoteWorkerControllerParent::~RemoteWorkerControllerParent() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mIPCActive);
+  MOZ_ASSERT(!mRemoteWorkerController);
+}
+
+PFetchEventOpParent* RemoteWorkerControllerParent::AllocPFetchEventOpParent(
+    const ParentToParentServiceWorkerFetchEventOpArgs& aArgs) {
+  AssertIsOnBackgroundThread();
+
+  RefPtr<FetchEventOpParent> actor = new FetchEventOpParent();
+  return actor.forget().take();
+}
+
+IPCResult RemoteWorkerControllerParent::RecvPFetchEventOpConstructor(
+    PFetchEventOpParent* aActor,
+    const ParentToParentServiceWorkerFetchEventOpArgs& aArgs) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  RefPtr<FetchEventOpParent> realFetchOp =
+      static_cast<FetchEventOpParent*>(aActor);
+  mRemoteWorkerController->ExecServiceWorkerFetchEventOp(aArgs, realFetchOp)
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [fetchOp = std::move(realFetchOp)](
+              ServiceWorkerFetchEventOpPromise::ResolveOrRejectValue&&
+                  aResult) {
+            if (NS_WARN_IF(aResult.IsReject())) {
+              MOZ_ASSERT(NS_FAILED(aResult.RejectValue()));
+              Unused << fetchOp->Send__delete__(fetchOp, aResult.RejectValue());
+              return;
+            }
+
+            Unused << fetchOp->Send__delete__(fetchOp, aResult.ResolveValue());
+          });
+
+  return IPC_OK();
+}
+
+bool RemoteWorkerControllerParent::DeallocPFetchEventOpParent(
+    PFetchEventOpParent* aActor) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  RefPtr<FetchEventOpParent> actor =
+      dont_AddRef(static_cast<FetchEventOpParent*>(aActor));
+  return true;
+}
+
+IPCResult RemoteWorkerControllerParent::RecvExecServiceWorkerOp(
+    ServiceWorkerOpArgs&& aArgs, ExecServiceWorkerOpResolver&& aResolve) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mIPCActive);
+  MOZ_ASSERT(mRemoteWorkerController);
+
+  mRemoteWorkerController->ExecServiceWorkerOp(std::move(aArgs))
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [resolve = std::move(aResolve)](
+                 ServiceWorkerOpPromise::ResolveOrRejectValue&& aResult) {
+               if (NS_WARN_IF(aResult.IsReject())) {
+                 MOZ_ASSERT(NS_FAILED(aResult.RejectValue()));
+                 resolve(aResult.RejectValue());
+                 return;
+               }
+
+               resolve(aResult.ResolveValue());
+             });
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerControllerParent::RecvShutdown(
+    ShutdownResolver&& aResolve) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mIPCActive);
+  MOZ_ASSERT(mRemoteWorkerController);
+
+  mIPCActive = false;
+
+  mRemoteWorkerController->Shutdown();
+  mRemoteWorkerController = nullptr;
+
+  aResolve(true);
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerControllerParent::Recv__delete__() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mIPCActive);
+  MOZ_ASSERT(!mRemoteWorkerController);
+
+  return IPC_OK();
+}
+
+void RemoteWorkerControllerParent::ActorDestroy(ActorDestroyReason aReason) {
+  AssertIsOnBackgroundThread();
+
+  if (NS_WARN_IF(mIPCActive)) {
+    mIPCActive = false;
+  }
+
+  if (NS_WARN_IF(mRemoteWorkerController)) {
+    mRemoteWorkerController->Shutdown();
+    mRemoteWorkerController = nullptr;
+  }
+}
+
+void RemoteWorkerControllerParent::CreationFailed() {
+  AssertIsOnBackgroundThread();
+
+  if (!mIPCActive) {
+    return;
+  }
+
+  Unused << SendCreationFailed();
+}
+
+void RemoteWorkerControllerParent::CreationSucceeded() {
+  AssertIsOnBackgroundThread();
+
+  if (!mIPCActive) {
+    return;
+  }
+
+  Unused << SendCreationSucceeded();
+}
+
+void RemoteWorkerControllerParent::ErrorReceived(const ErrorValue& aValue) {
+  AssertIsOnBackgroundThread();
+
+  if (!mIPCActive) {
+    return;
+  }
+
+  Unused << SendErrorReceived(aValue);
+}
+
+void RemoteWorkerControllerParent::Terminated() {
+  AssertIsOnBackgroundThread();
+
+  if (!mIPCActive) {
+    return;
+  }
+
+  Unused << SendTerminated();
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerControllerParent.h b/dom/workers/remoteworkers/RemoteWorkerControllerParent.h
new file mode 100644
index 0000000000..618fbf9506
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerControllerParent.h
@@ -0,0 +1,86 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_remoteworkercontrollerparent_h__
+#define mozilla_dom_remoteworkercontrollerparent_h__
+
+#include <functional>
+
+#include "nsISupportsImpl.h"
+
+#include "RemoteWorkerController.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/PRemoteWorkerControllerParent.h"
+
+namespace mozilla::dom {
+
+/**
+ * PBackground-resident proxy used by ServiceWorkerManager because canonical
+ * ServiceWorkerManager state exists on the parent process main thread but the
+ * RemoteWorkerController API is used from the parent process PBackground
+ * thread.
+ */
+class RemoteWorkerControllerParent final : public PRemoteWorkerControllerParent,
+                                           public RemoteWorkerObserver {
+  friend class PRemoteWorkerControllerParent;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerControllerParent, override)
+
+  explicit RemoteWorkerControllerParent(
+      const RemoteWorkerData& aRemoteWorkerData);
+
+  // Returns the corresponding RemoteWorkerParent (if any).
+  RefPtr<RemoteWorkerParent> GetRemoteWorkerParent() const;
+
+  void MaybeSendSetServiceWorkerSkipWaitingFlag(
+      std::function<void(bool)>&& aCallback);
+
+ private:
+  ~RemoteWorkerControllerParent();
+
+  PFetchEventOpParent* AllocPFetchEventOpParent(
+      const ParentToParentServiceWorkerFetchEventOpArgs& aArgs);
+
+  mozilla::ipc::IPCResult RecvPFetchEventOpConstructor(
+      PFetchEventOpParent* aActor,
+      const ParentToParentServiceWorkerFetchEventOpArgs& aArgs) override;
+
+  bool DeallocPFetchEventOpParent(PFetchEventOpParent* aActor);
+
+  mozilla::ipc::IPCResult RecvExecServiceWorkerOp(
+      ServiceWorkerOpArgs&& aArgs, ExecServiceWorkerOpResolver&& aResolve);
+
+  mozilla::ipc::IPCResult RecvShutdown(ShutdownResolver&& aResolve);
+
+  mozilla::ipc::IPCResult Recv__delete__() override;
+
+  void ActorDestroy(ActorDestroyReason aReason) override;
+
+  void CreationFailed() override;
+
+  void CreationSucceeded() override;
+
+  void ErrorReceived(const ErrorValue& aValue) override;
+
+  void LockNotified(bool aCreated) final {
+    // no-op for service workers
+  }
+
+  void WebTransportNotified(bool aCreated) final {
+    // no-op for service workers
+  }
+
+  void Terminated() override;
+
+  RefPtr<RemoteWorkerController> mRemoteWorkerController;
+
+  bool mIPCActive = true;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_remoteworkercontrollerparent_h__
diff --git a/dom/workers/remoteworkers/RemoteWorkerManager.cpp b/dom/workers/remoteworkers/RemoteWorkerManager.cpp
new file mode 100644
index 0000000000..9d9189b38f
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerManager.cpp
@@ -0,0 +1,735 @@
+/* -*- 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 "RemoteWorkerManager.h"
+
+#include <utility>
+
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/dom/ContentChild.h"  // ContentChild::GetSingleton
+#include "mozilla/dom/RemoteWorkerController.h"
+#include "mozilla/dom/RemoteWorkerParent.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/PBackgroundParent.h"
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+#  include "mozilla/dom/DOMException.h"
+#  include "mozilla/CycleCollectedJSContext.h"
+#  include "mozilla/Sprintf.h"  // SprintfLiteral
+#  include "nsIXPConnect.h"     // nsIXPConnectWrappedJS
+#endif
+#include "mozilla/StaticPrefs_extensions.h"
+#include "nsCOMPtr.h"
+#include "nsIE10SUtils.h"
+#include "nsImportModule.h"
+#include "nsIXULRuntime.h"
+#include "nsTArray.h"
+#include "nsThreadUtils.h"
+#include "RemoteWorkerServiceParent.h"
+
+mozilla::LazyLogModule gRemoteWorkerManagerLog("RemoteWorkerManager");
+
+#ifdef LOG
+#  undef LOG
+#endif
+#define LOG(fmt) \
+  MOZ_LOG(gRemoteWorkerManagerLog, mozilla::LogLevel::Verbose, fmt)
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+namespace {
+
+// Raw pointer because this object is kept alive by RemoteWorkerServiceParent
+// actors.
+RemoteWorkerManager* sRemoteWorkerManager;
+
+bool IsServiceWorker(const RemoteWorkerData& aData) {
+  return aData.serviceWorkerData().type() ==
+         OptionalServiceWorkerData::TServiceWorkerData;
+}
+
+void TransmitPermissionsAndBlobURLsForPrincipalInfo(
+    ContentParent* aContentParent, const PrincipalInfo& aPrincipalInfo) {
+  AssertIsOnMainThread();
+  MOZ_ASSERT(aContentParent);
+
+  auto principalOrErr = PrincipalInfoToPrincipal(aPrincipalInfo);
+
+  if (NS_WARN_IF(principalOrErr.isErr())) {
+    return;
+  }
+
+  nsCOMPtr<nsIPrincipal> principal = principalOrErr.unwrap();
+
+  aContentParent->TransmitBlobURLsForPrincipal(principal);
+
+  MOZ_ALWAYS_SUCCEEDS(
+      aContentParent->TransmitPermissionsForPrincipal(principal));
+}
+
+}  // namespace
+
+// static
+bool RemoteWorkerManager::MatchRemoteType(const nsACString& processRemoteType,
+                                          const nsACString& workerRemoteType) {
+  LOG(("MatchRemoteType [processRemoteType=%s, workerRemoteType=%s]",
+       PromiseFlatCString(processRemoteType).get(),
+       PromiseFlatCString(workerRemoteType).get()));
+
+  // Respecting COOP and COEP requires processing headers in the parent
+  // process in order to choose an appropriate content process, but the
+  // workers' ScriptLoader processes headers in content processes. An
+  // intermediary step that provides security guarantees is to simply never
+  // allow SharedWorkers and ServiceWorkers to exist in a COOP+COEP process.
+  // The ultimate goal is to allow these worker types to be put in such
+  // processes based on their script response headers.
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=1595206
+  //
+  // RemoteWorkerManager::GetRemoteType should not select this remoteType
+  // and so workerRemoteType is not expected to be set to a coop+coep
+  // remoteType and here we can just assert that it is not happening.
+  MOZ_ASSERT(!IsWebCoopCoepRemoteType(workerRemoteType));
+
+  return processRemoteType.Equals(workerRemoteType);
+}
+
+// static
+Result<nsCString, nsresult> RemoteWorkerManager::GetRemoteType(
+    const nsCOMPtr<nsIPrincipal>& aPrincipal, WorkerKind aWorkerKind) {
+  AssertIsOnMainThread();
+
+  MOZ_ASSERT_IF(aWorkerKind == WorkerKind::WorkerKindService,
+                aPrincipal->GetIsContentPrincipal());
+
+  nsCOMPtr<nsIE10SUtils> e10sUtils = do_ImportESModule(
+      "resource://gre/modules/E10SUtils.sys.mjs", "E10SUtils", fallible);
+  if (NS_WARN_IF(!e10sUtils)) {
+    LOG(("GetRemoteType Abort: could not import E10SUtils"));
+    return Err(NS_ERROR_DOM_ABORT_ERR);
+  }
+
+  nsCString preferredRemoteType = DEFAULT_REMOTE_TYPE;
+  if (aWorkerKind == WorkerKind::WorkerKindShared) {
+    if (auto* contentChild = ContentChild::GetSingleton()) {
+      // For a shared worker set the preferred remote type to the content
+      // child process remote type.
+      preferredRemoteType = contentChild->GetRemoteType();
+    } else if (aPrincipal->IsSystemPrincipal()) {
+      preferredRemoteType = NOT_REMOTE_TYPE;
+    }
+  }
+
+  nsIE10SUtils::RemoteWorkerType workerType;
+
+  switch (aWorkerKind) {
+    case WorkerKind::WorkerKindService:
+      workerType = nsIE10SUtils::REMOTE_WORKER_TYPE_SERVICE;
+      break;
+    case WorkerKind::WorkerKindShared:
+      workerType = nsIE10SUtils::REMOTE_WORKER_TYPE_SHARED;
+      break;
+    default:
+      // This method isn't expected to be called for worker types that
+      // aren't remote workers (currently Service and Shared workers).
+      LOG(("GetRemoteType Error on unexpected worker type"));
+      MOZ_DIAGNOSTIC_ASSERT(false, "Unexpected worker type");
+      return Err(NS_ERROR_DOM_ABORT_ERR);
+  }
+
+  // Here we do not have access to the window and so we can't use its
+  // useRemoteTabs and useRemoteSubframes flags (for the service
+  // worker there may not even be a window associated to the worker
+  // yet), and so we have to use the prefs instead.
+  bool isMultiprocess = BrowserTabsRemoteAutostart();
+  bool isFission = FissionAutostart();
+
+  nsCString remoteType = NOT_REMOTE_TYPE;
+
+  nsresult rv = e10sUtils->GetRemoteTypeForWorkerPrincipal(
+      aPrincipal, workerType, isMultiprocess, isFission, preferredRemoteType,
+      remoteType);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    LOG(
+        ("GetRemoteType Abort: E10SUtils.getRemoteTypeForWorkerPrincipal "
+         "exception"));
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+    nsCString principalTypeOrScheme;
+    if (aPrincipal->IsSystemPrincipal()) {
+      principalTypeOrScheme = "system"_ns;
+    } else if (aPrincipal->GetIsExpandedPrincipal()) {
+      principalTypeOrScheme = "expanded"_ns;
+    } else if (aPrincipal->GetIsNullPrincipal()) {
+      principalTypeOrScheme = "null"_ns;
+    } else {
+      nsCOMPtr<nsIURI> uri = aPrincipal->GetURI();
+      nsresult rv2 = uri->GetScheme(principalTypeOrScheme);
+      if (NS_FAILED(rv2)) {
+        principalTypeOrScheme = "content"_ns;
+      }
+    }
+
+    nsCString processRemoteType = "parent"_ns;
+    if (auto* contentChild = ContentChild::GetSingleton()) {
+      // RemoteTypePrefix make sure that we are not going to include
+      // the full origin that may be part of the current remote type.
+      processRemoteType = RemoteTypePrefix(contentChild->GetRemoteType());
+    }
+
+    // Convert the error code into an error name.
+    nsAutoCString errorName;
+    GetErrorName(rv, errorName);
+
+    // Try to retrieve the line number from the exception.
+    nsAutoCString errorFilename("(unknown)"_ns);
+    uint32_t jsmErrorLineNumber = 0;
+
+    if (auto* context = CycleCollectedJSContext::Get()) {
+      if (RefPtr<Exception> exn = context->GetPendingException()) {
+        nsAutoString filename(u"(unknown)"_ns);
+
+        if (rv == NS_ERROR_XPC_JAVASCRIPT_ERROR_WITH_DETAILS) {
+          // When the failure is a Javascript Error, the line number retrieved
+          // from the Exception instance isn't going to be the E10SUtils.sys.mjs
+          // line that originated the failure, and so we fallback to retrieve it
+          // from the nsIScriptError.
+          nsCOMPtr<nsIScriptError> scriptError =
+              do_QueryInterface(exn->GetData());
+          if (scriptError) {
+            scriptError->GetLineNumber(&jsmErrorLineNumber);
+            scriptError->GetSourceName(filename);
+          }
+        } else {
+          nsCOMPtr<nsIXPConnectWrappedJS> wrapped =
+              do_QueryInterface(e10sUtils);
+          dom::AutoJSAPI jsapi;
+          if (jsapi.Init(wrapped->GetJSObjectGlobal())) {
+            auto* cx = jsapi.cx();
+            jsmErrorLineNumber = exn->LineNumber(cx);
+            exn->GetFilename(cx, filename);
+          }
+        }
+
+        errorFilename = NS_ConvertUTF16toUTF8(filename);
+      }
+    }
+
+    char buf[1024];
+    SprintfLiteral(
+        buf,
+        "workerType=%s, principal=%s, preferredRemoteType=%s, "
+        "processRemoteType=%s, errorName=%s, errorLocation=%s:%d",
+        aWorkerKind == WorkerKind::WorkerKindService ? "service" : "shared",
+        principalTypeOrScheme.get(),
+        PromiseFlatCString(RemoteTypePrefix(preferredRemoteType)).get(),
+        processRemoteType.get(), errorName.get(), errorFilename.get(),
+        jsmErrorLineNumber);
+    MOZ_CRASH_UNSAFE_PRINTF(
+        "E10SUtils.getRemoteTypeForWorkerPrincipal did throw: %s", buf);
+#endif
+    return Err(NS_ERROR_DOM_ABORT_ERR);
+  }
+
+  if (MOZ_LOG_TEST(gRemoteWorkerManagerLog, LogLevel::Verbose)) {
+    nsCString principalOrigin;
+    aPrincipal->GetOrigin(principalOrigin);
+
+    LOG(
+        ("GetRemoteType workerType=%s, principal=%s, "
+         "preferredRemoteType=%s, selectedRemoteType=%s",
+         aWorkerKind == WorkerKind::WorkerKindService ? "service" : "shared",
+         principalOrigin.get(), preferredRemoteType.get(), remoteType.get()));
+  }
+
+  return remoteType;
+}
+
+// static
+bool RemoteWorkerManager::HasExtensionPrincipal(const RemoteWorkerData& aData) {
+  auto principalInfo = aData.principalInfo();
+  return principalInfo.type() == PrincipalInfo::TContentPrincipalInfo &&
+         // This helper method is also called from the background thread and so
+         // we can't check if the principal does have an addonPolicy object
+         // associated and we have to resort to check the url scheme instead.
+         StringBeginsWith(principalInfo.get_ContentPrincipalInfo().spec(),
+                          "moz-extension://"_ns);
+}
+
+// static
+bool RemoteWorkerManager::IsRemoteTypeAllowed(const RemoteWorkerData& aData) {
+  AssertIsOnMainThread();
+
+  // If Gecko is running in single process mode, there is no child process
+  // to select and we have to just consider it valid (if it should haven't
+  // been launched it should have been already prevented before reaching
+  // a RemoteWorkerChild instance).
+  if (!BrowserTabsRemoteAutostart()) {
+    return true;
+  }
+
+  const auto& principalInfo = aData.principalInfo();
+
+  auto* contentChild = ContentChild::GetSingleton();
+  if (!contentChild) {
+    // If e10s isn't disabled, only workers related to the system principal
+    // should be allowed to run in the parent process, and extension principals
+    // if extensions.webextensions.remote is false.
+    return principalInfo.type() == PrincipalInfo::TSystemPrincipalInfo ||
+           (!StaticPrefs::extensions_webextensions_remote() &&
+            aData.remoteType().Equals(NOT_REMOTE_TYPE) &&
+            HasExtensionPrincipal(aData));
+  }
+
+  auto principalOrErr = PrincipalInfoToPrincipal(principalInfo);
+  if (NS_WARN_IF(principalOrErr.isErr())) {
+    return false;
+  }
+  nsCOMPtr<nsIPrincipal> principal = principalOrErr.unwrap();
+
+  // Recompute the remoteType based on the principal, to double-check that it
+  // has not been tempered to select a different child process than the one
+  // expected.
+  bool isServiceWorker = aData.serviceWorkerData().type() ==
+                         OptionalServiceWorkerData::TServiceWorkerData;
+  auto remoteType = GetRemoteType(
+      principal, isServiceWorker ? WorkerKindService : WorkerKindShared);
+  if (NS_WARN_IF(remoteType.isErr())) {
+    LOG(("IsRemoteTypeAllowed: Error to retrieve remote type"));
+    return false;
+  }
+
+  return MatchRemoteType(remoteType.unwrap(), contentChild->GetRemoteType());
+}
+
+/* static */
+already_AddRefed<RemoteWorkerManager> RemoteWorkerManager::GetOrCreate() {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  if (!sRemoteWorkerManager) {
+    sRemoteWorkerManager = new RemoteWorkerManager();
+  }
+
+  RefPtr<RemoteWorkerManager> rwm = sRemoteWorkerManager;
+  return rwm.forget();
+}
+
+RemoteWorkerManager::RemoteWorkerManager() : mParentActor(nullptr) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!sRemoteWorkerManager);
+}
+
+RemoteWorkerManager::~RemoteWorkerManager() {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(sRemoteWorkerManager == this);
+  sRemoteWorkerManager = nullptr;
+}
+
+void RemoteWorkerManager::RegisterActor(RemoteWorkerServiceParent* aActor) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (!BackgroundParent::IsOtherProcessActor(aActor->Manager())) {
+    MOZ_ASSERT(!mParentActor);
+    mParentActor = aActor;
+    MOZ_ASSERT(mPendings.IsEmpty());
+    return;
+  }
+
+  MOZ_ASSERT(!mChildActors.Contains(aActor));
+  mChildActors.AppendElement(aActor);
+
+  if (!mPendings.IsEmpty()) {
+    const auto& processRemoteType = aActor->GetRemoteType();
+    nsTArray<Pending> unlaunched;
+
+    // Flush pending launching.
+    for (Pending& p : mPendings) {
+      if (p.mController->IsTerminated()) {
+        continue;
+      }
+
+      const auto& workerRemoteType = p.mData.remoteType();
+
+      if (MatchRemoteType(processRemoteType, workerRemoteType)) {
+        LOG(("RegisterActor - Launch Pending, workerRemoteType=%s",
+             workerRemoteType.get()));
+        LaunchInternal(p.mController, aActor, p.mData);
+      } else {
+        unlaunched.AppendElement(std::move(p));
+        continue;
+      }
+    }
+
+    std::swap(mPendings, unlaunched);
+
+    // AddRef is called when the first Pending object is added to mPendings, so
+    // the balancing Release is called when the last Pending object is removed.
+    // RemoteWorkerServiceParents will hold strong references to
+    // RemoteWorkerManager.
+    if (mPendings.IsEmpty()) {
+      Release();
+    }
+
+    LOG(("RegisterActor - mPendings length: %zu", mPendings.Length()));
+  }
+}
+
+void RemoteWorkerManager::UnregisterActor(RemoteWorkerServiceParent* aActor) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  if (aActor == mParentActor) {
+    mParentActor = nullptr;
+  } else {
+    MOZ_ASSERT(mChildActors.Contains(aActor));
+    mChildActors.RemoveElement(aActor);
+  }
+}
+
+void RemoteWorkerManager::Launch(RemoteWorkerController* aController,
+                                 const RemoteWorkerData& aData,
+                                 base::ProcessId aProcessId) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  RemoteWorkerServiceParent* targetActor = SelectTargetActor(aData, aProcessId);
+
+  // If there is not an available actor, let's store the data, and let's spawn a
+  // new process.
+  if (!targetActor) {
+    // If this is the first time we have a pending launching, we must keep alive
+    // the manager.
+    if (mPendings.IsEmpty()) {
+      AddRef();
+    }
+
+    Pending* pending = mPendings.AppendElement();
+    pending->mController = aController;
+    pending->mData = aData;
+
+    // Launching is async, so we cannot check for failures right here.
+    LaunchNewContentProcess(aData);
+    return;
+  }
+
+  /**
+   * If a target actor for the remote worker has been selected, the actor has
+   * already been registered with the corresponding `ContentParent` and we
+   * should not increment the `mRemoteWorkerActorData`'s `mCount` again (see
+   * `SelectTargetActorForServiceWorker()` /
+   * `SelectTargetActorForSharedWorker()`).
+   */
+  LaunchInternal(aController, targetActor, aData, true);
+}
+
+void RemoteWorkerManager::LaunchInternal(
+    RemoteWorkerController* aController,
+    RemoteWorkerServiceParent* aTargetActor, const RemoteWorkerData& aData,
+    bool aRemoteWorkerAlreadyRegistered) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aController);
+  MOZ_ASSERT(aTargetActor);
+  MOZ_ASSERT(aTargetActor == mParentActor ||
+             mChildActors.Contains(aTargetActor));
+
+  // We need to send permissions to content processes, but not if we're spawning
+  // the worker here in the parent process.
+  if (aTargetActor != mParentActor) {
+    RefPtr<ThreadsafeContentParentHandle> contentHandle =
+        BackgroundParent::GetContentParentHandle(aTargetActor->Manager());
+
+    // This won't cause any race conditions because the content process
+    // should wait for the permissions to be received before executing the
+    // Service Worker.
+    nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+        __func__, [contentHandle = std::move(contentHandle),
+                   principalInfo = aData.principalInfo()] {
+          AssertIsOnMainThread();
+          if (RefPtr<ContentParent> contentParent =
+                  contentHandle->GetContentParent()) {
+            TransmitPermissionsAndBlobURLsForPrincipalInfo(contentParent,
+                                                           principalInfo);
+          }
+        });
+
+    MOZ_ALWAYS_SUCCEEDS(
+        SchedulerGroup::Dispatch(TaskCategory::Other, r.forget()));
+  }
+
+  RefPtr<RemoteWorkerParent> workerActor = MakeAndAddRef<RemoteWorkerParent>();
+  if (!aTargetActor->Manager()->SendPRemoteWorkerConstructor(workerActor,
+                                                             aData)) {
+    AsyncCreationFailed(aController);
+    return;
+  }
+
+  workerActor->Initialize(aRemoteWorkerAlreadyRegistered);
+
+  // This makes the link better the 2 actors.
+  aController->SetWorkerActor(workerActor);
+  workerActor->SetController(aController);
+}
+
+void RemoteWorkerManager::AsyncCreationFailed(
+    RemoteWorkerController* aController) {
+  RefPtr<RemoteWorkerController> controller = aController;
+  nsCOMPtr<nsIRunnable> r =
+      NS_NewRunnableFunction("RemoteWorkerManager::AsyncCreationFailed",
+                             [controller]() { controller->CreationFailed(); });
+
+  NS_DispatchToCurrentThread(r.forget());
+}
+
+template <typename Callback>
+void RemoteWorkerManager::ForEachActor(
+    Callback&& aCallback, const nsACString& aRemoteType,
+    Maybe<base::ProcessId> aProcessId) const {
+  AssertIsOnBackgroundThread();
+
+  const auto length = mChildActors.Length();
+
+  auto end = static_cast<uint32_t>(rand()) % length;
+  if (aProcessId) {
+    // Start from the actor with the given processId instead of starting from
+    // a random index.
+    for (auto j = length - 1; j > 0; j--) {
+      if (mChildActors[j]->OtherPid() == *aProcessId) {
+        end = j;
+        break;
+      }
+    }
+  }
+
+  uint32_t i = end;
+
+  do {
+    MOZ_ASSERT(i < mChildActors.Length());
+    RemoteWorkerServiceParent* actor = mChildActors[i];
+
+    if (MatchRemoteType(actor->GetRemoteType(), aRemoteType)) {
+      ThreadsafeContentParentHandle* contentHandle =
+          BackgroundParent::GetContentParentHandle(actor->Manager());
+
+      if (!aCallback(actor, contentHandle)) {
+        break;
+      }
+    }
+
+    i = (i + 1) % length;
+  } while (i != end);
+}
+
+/**
+ * When selecting a target actor for a given remote worker, we have to consider
+ * that:
+ *
+ * - Service Workers can spawn even when their registering page/script isn't
+ *   active (e.g. push notifications), so we don't attempt to spawn the worker
+ *   in its registering script's process. We search linearly and choose the
+ *   search's starting position randomly.
+ *
+ * - When Fission is enabled, Shared Workers may have to be spawned into
+ * different child process from the one where it has been registered from, and
+ * that child process may be going to be marked as dead and shutdown.
+ *
+ * Spawning the workers in a random process makes the process selection criteria
+ * a little tricky, as a candidate process may imminently shutdown due to a
+ * remove worker actor unregistering
+ * (see `ContentParent::UnregisterRemoveWorkerActor`).
+ *
+ * In `ContentParent::MaybeAsyncSendShutDownMessage` we only dispatch a runnable
+ * to call `ContentParent::ShutDownProcess` if there are no registered remote
+ * worker actors, and we ensure that the check for the number of registered
+ * actors and the dispatching of the runnable are atomic. That happens on the
+ * main thread, so here on the background thread,  while
+ * `ContentParent::mRemoteWorkerActorData` is locked, if `mCount` > 0, we can
+ * register a remote worker actor "early" and guarantee that the corresponding
+ * content process will not shutdown.
+ */
+RemoteWorkerServiceParent* RemoteWorkerManager::SelectTargetActorInternal(
+    const RemoteWorkerData& aData, base::ProcessId aProcessId) const {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mChildActors.IsEmpty());
+
+  RemoteWorkerServiceParent* actor = nullptr;
+
+  const auto& workerRemoteType = aData.remoteType();
+
+  ForEachActor(
+      [&](RemoteWorkerServiceParent* aActor,
+          ThreadsafeContentParentHandle* aContentHandle) {
+        // Make sure to choose an actor related to a child process that is not
+        // going to shutdown while we are still in the process of launching the
+        // remote worker.
+        //
+        // ForEachActor will start from the child actor coming from the child
+        // process with a pid equal to aProcessId if any, otherwise it would
+        // start from a random actor in the mChildActors array, this guarantees
+        // that we will choose that actor if it does also match the remote type.
+        if (aContentHandle->MaybeRegisterRemoteWorkerActor(
+                [&](uint32_t count, bool shutdownStarted) -> bool {
+                  return (count || !shutdownStarted) &&
+                         (aActor->OtherPid() == aProcessId || !actor);
+                })) {
+          actor = aActor;
+          return false;
+        }
+        MOZ_ASSERT(!actor);
+        return true;
+      },
+      workerRemoteType, IsServiceWorker(aData) ? Nothing() : Some(aProcessId));
+
+  return actor;
+}
+
+RemoteWorkerServiceParent* RemoteWorkerManager::SelectTargetActor(
+    const RemoteWorkerData& aData, base::ProcessId aProcessId) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  // System principal workers should run on the parent process.
+  if (aData.principalInfo().type() == PrincipalInfo::TSystemPrincipalInfo) {
+    MOZ_ASSERT(mParentActor);
+    return mParentActor;
+  }
+
+  // Extension principal workers are allowed to run on the parent process
+  // when "extension.webextensions.remote" pref is false.
+  if (aProcessId == base::GetCurrentProcId() &&
+      aData.remoteType().Equals(NOT_REMOTE_TYPE) &&
+      !StaticPrefs::extensions_webextensions_remote() &&
+      HasExtensionPrincipal(aData)) {
+    MOZ_ASSERT(mParentActor);
+    return mParentActor;
+  }
+
+  // If e10s is off, use the parent process.
+  if (!BrowserTabsRemoteAutostart()) {
+    MOZ_ASSERT(mParentActor);
+    return mParentActor;
+  }
+
+  // We shouldn't have to worry about content-principal parent-process workers.
+  MOZ_ASSERT(aProcessId != base::GetCurrentProcId());
+
+  if (mChildActors.IsEmpty()) {
+    return nullptr;
+  }
+
+  return SelectTargetActorInternal(aData, aProcessId);
+}
+
+void RemoteWorkerManager::LaunchNewContentProcess(
+    const RemoteWorkerData& aData) {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  nsCOMPtr<nsISerialEventTarget> bgEventTarget = GetCurrentSerialEventTarget();
+
+  using LaunchPromiseType = ContentParent::LaunchPromise;
+  using CallbackParamType = LaunchPromiseType::ResolveOrRejectValue;
+
+  // A new content process must be requested on the main thread. On success,
+  // the success callback will also run on the main thread. On failure, however,
+  // the failure callback must be run on the background thread - it uses
+  // RemoteWorkerManager, and RemoteWorkerManager isn't threadsafe, so the
+  // promise callback will just dispatch the "real" failure callback to the
+  // background thread.
+  auto processLaunchCallback = [principalInfo = aData.principalInfo(),
+                                bgEventTarget = std::move(bgEventTarget),
+                                self = RefPtr<RemoteWorkerManager>(this)](
+                                   const CallbackParamType& aValue,
+                                   const nsCString& remoteType) mutable {
+    if (aValue.IsResolve()) {
+      LOG(("LaunchNewContentProcess: successfully got child process"));
+
+      // The failure callback won't run, and we're on the main thread, so
+      // we need to properly release the thread-unsafe RemoteWorkerManager.
+      NS_ProxyRelease(__func__, bgEventTarget, self.forget());
+    } else {
+      // The "real" failure callback.
+      nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+          __func__, [self = std::move(self), remoteType] {
+            nsTArray<Pending> uncancelled;
+            auto pendings = std::move(self->mPendings);
+
+            for (const auto& pending : pendings) {
+              const auto& workerRemoteType = pending.mData.remoteType();
+              if (self->MatchRemoteType(remoteType, workerRemoteType)) {
+                LOG(
+                    ("LaunchNewContentProcess: Cancel pending with "
+                     "workerRemoteType=%s",
+                     workerRemoteType.get()));
+                pending.mController->CreationFailed();
+              } else {
+                uncancelled.AppendElement(pending);
+              }
+            }
+
+            std::swap(self->mPendings, uncancelled);
+          });
+
+      bgEventTarget->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+    }
+  };
+
+  LOG(("LaunchNewContentProcess: remoteType=%s", aData.remoteType().get()));
+
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      __func__, [callback = std::move(processLaunchCallback),
+                 workerRemoteType = aData.remoteType()]() mutable {
+        auto remoteType =
+            workerRemoteType.IsEmpty() ? DEFAULT_REMOTE_TYPE : workerRemoteType;
+
+        RefPtr<LaunchPromiseType> onFinished;
+        if (!AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+          // Request a process making sure to specify aPreferUsed=true.  For a
+          // given remoteType there's a pool size limit.  If we pass aPreferUsed
+          // here, then if there's any process in the pool already, we will use
+          // that.  If we pass false (which is the default if omitted), then
+          // this call will spawn a new process if the pool isn't at its limit
+          // yet.
+          //
+          // (Our intent is never to grow the pool size here.  Our logic gets
+          // here because our current logic on PBackground is only aware of
+          // RemoteWorkerServiceParent actors that have registered themselves,
+          // which is fundamentally unaware of processes that will match in the
+          // future when they register.  So we absolutely are fine with and want
+          // any existing processes.)
+          onFinished = ContentParent::GetNewOrUsedBrowserProcessAsync(
+              /* aRemoteType = */ remoteType,
+              /* aGroup */ nullptr,
+              hal::ProcessPriority::PROCESS_PRIORITY_FOREGROUND,
+              /* aPreferUsed */ true);
+        } else {
+          // We can find this event still in flight after having been asked to
+          // shutdown. Let's fake a failure to ensure our callback is called
+          // such that we clean up everything properly.
+          onFinished = LaunchPromiseType::CreateAndReject(
+              NS_ERROR_ILLEGAL_DURING_SHUTDOWN, __func__);
+        }
+        onFinished->Then(GetCurrentSerialEventTarget(), __func__,
+                         [callback = std::move(callback),
+                          remoteType](const CallbackParamType& aValue) mutable {
+                           callback(aValue, remoteType);
+                         });
+      });
+
+  SchedulerGroup::Dispatch(TaskCategory::Other, r.forget());
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerManager.h b/dom/workers/remoteworkers/RemoteWorkerManager.h
new file mode 100644
index 0000000000..5ff11ee6e6
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerManager.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_dom_RemoteWorkerManager_h
+#define mozilla_dom_RemoteWorkerManager_h
+
+#include "base/process.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/RemoteWorkerTypes.h"
+#include "mozilla/dom/WorkerPrivate.h"  // WorkerKind enum
+#include "nsISupportsImpl.h"
+#include "nsTArray.h"
+
+namespace mozilla::dom {
+
+class RemoteWorkerController;
+class RemoteWorkerServiceParent;
+
+/**
+ * PBackground instance that keeps tracks of RemoteWorkerServiceParent actors
+ * (1 per process, including the main process) and pending
+ * RemoteWorkerController requests to spawn remote workers if the spawn request
+ * can't be immediately fulfilled. Decides which RemoteWorkerServerParent to use
+ * internally via SelectTargetActor in order to select a BackgroundParent
+ * manager on which to create a RemoteWorkerParent.
+ */
+class RemoteWorkerManager final {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerManager)
+
+  static already_AddRefed<RemoteWorkerManager> GetOrCreate();
+
+  void RegisterActor(RemoteWorkerServiceParent* aActor);
+
+  void UnregisterActor(RemoteWorkerServiceParent* aActor);
+
+  void Launch(RemoteWorkerController* aController,
+              const RemoteWorkerData& aData, base::ProcessId aProcessId);
+
+  static bool MatchRemoteType(const nsACString& processRemoteType,
+                              const nsACString& workerRemoteType);
+
+  /**
+   * Get the child process RemoteType where a RemoteWorker should be
+   * launched.
+   */
+  static Result<nsCString, nsresult> GetRemoteType(
+      const nsCOMPtr<nsIPrincipal>& aPrincipal, WorkerKind aWorkerKind);
+
+  /**
+   * Verify if a remote worker should be allowed to run in the current
+   * child process remoteType.
+   */
+  static bool IsRemoteTypeAllowed(const RemoteWorkerData& aData);
+
+  static bool HasExtensionPrincipal(const RemoteWorkerData& aData);
+
+ private:
+  RemoteWorkerManager();
+  ~RemoteWorkerManager();
+
+  RemoteWorkerServiceParent* SelectTargetActor(const RemoteWorkerData& aData,
+                                               base::ProcessId aProcessId);
+
+  RemoteWorkerServiceParent* SelectTargetActorInternal(
+      const RemoteWorkerData& aData, base::ProcessId aProcessId) const;
+
+  void LaunchInternal(RemoteWorkerController* aController,
+                      RemoteWorkerServiceParent* aTargetActor,
+                      const RemoteWorkerData& aData,
+                      bool aRemoteWorkerAlreadyRegistered = false);
+
+  void LaunchNewContentProcess(const RemoteWorkerData& aData);
+
+  void AsyncCreationFailed(RemoteWorkerController* aController);
+
+  // Iterate through all RemoteWorkerServiceParent actors with the given
+  // remoteType, starting from the actor related to a child process with pid
+  // aProcessId if needed and available or from a random index otherwise (as if
+  // iterating through a circular array).
+  //
+  // aCallback should be a invokable object with a function signature of
+  //   bool (RemoteWorkerServiceParent*, RefPtr<ContentParent>&&)
+  //
+  // aCallback is called with the actor and corresponding ContentParent, should
+  // return false to abort iteration before all actors have been traversed (e.g.
+  // if the desired actor is found), and must not mutate mChildActors (which
+  // shouldn't be an issue because this function is const). aCallback also
+  // doesn't need to worry about proxy-releasing the ContentParent if it isn't
+  // moved out of the parameter.
+  template <typename Callback>
+  void ForEachActor(Callback&& aCallback, const nsACString& aRemoteType,
+                    Maybe<base::ProcessId> aProcessId = Nothing()) const;
+
+  // The list of existing RemoteWorkerServiceParent actors for child processes.
+  // Raw pointers because RemoteWorkerServiceParent actors unregister themselves
+  // when destroyed.
+  // XXX For Fission, where we could have a lot of child actors, should we maybe
+  // instead keep either a hash table (PID->actor) or perhaps store the actors
+  // in order, sorted by PID, to avoid linear lookup times?
+  nsTArray<RemoteWorkerServiceParent*> mChildActors;
+  RemoteWorkerServiceParent* mParentActor;
+
+  struct Pending {
+    RefPtr<RemoteWorkerController> mController;
+    RemoteWorkerData mData;
+  };
+
+  nsTArray<Pending> mPendings;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerManager_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerParent.cpp b/dom/workers/remoteworkers/RemoteWorkerParent.cpp
new file mode 100644
index 0000000000..ee6c8b436e
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerParent.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 "RemoteWorkerParent.h"
+#include "RemoteWorkerController.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/PFetchEventOpProxyParent.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/Unused.h"
+#include "nsProxyRelease.h"
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+namespace {
+
+class UnregisterActorRunnable final : public Runnable {
+ public:
+  explicit UnregisterActorRunnable(
+      already_AddRefed<ThreadsafeContentParentHandle> aParent)
+      : Runnable("UnregisterActorRunnable"), mContentHandle(aParent) {
+    AssertIsOnBackgroundThread();
+  }
+
+  NS_IMETHOD
+  Run() override {
+    AssertIsOnMainThread();
+    if (RefPtr<ContentParent> contentParent =
+            mContentHandle->GetContentParent()) {
+      contentParent->UnregisterRemoveWorkerActor();
+    }
+
+    return NS_OK;
+  }
+
+ private:
+  RefPtr<ThreadsafeContentParentHandle> mContentHandle;
+};
+
+}  // namespace
+
+RemoteWorkerParent::RemoteWorkerParent() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+}
+
+RemoteWorkerParent::~RemoteWorkerParent() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+}
+
+void RemoteWorkerParent::Initialize(bool aAlreadyRegistered) {
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(Manager());
+
+  // Parent is null if the child actor runs on the parent process.
+  if (parent) {
+    if (!aAlreadyRegistered) {
+      parent->RegisterRemoteWorkerActor();
+    }
+
+    NS_ReleaseOnMainThread("RemoteWorkerParent::Initialize ContentParent",
+                           parent.forget());
+  }
+}
+
+already_AddRefed<PFetchEventOpProxyParent>
+RemoteWorkerParent::AllocPFetchEventOpProxyParent(
+    const ParentToChildServiceWorkerFetchEventOpArgs& aArgs) {
+  MOZ_CRASH("PFetchEventOpProxyParent actors must be manually constructed!");
+  return nullptr;
+}
+
+void RemoteWorkerParent::ActorDestroy(IProtocol::ActorDestroyReason) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(Manager());
+
+  // Parent is null if the child actor runs on the parent process.
+  if (parent) {
+    RefPtr<UnregisterActorRunnable> r =
+        new UnregisterActorRunnable(parent.forget());
+
+    SchedulerGroup::Dispatch(TaskCategory::Other, r.forget());
+  }
+
+  if (mController) {
+    mController->NoteDeadWorkerActor();
+    mController = nullptr;
+  }
+}
+
+IPCResult RemoteWorkerParent::RecvCreated(const bool& aStatus) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (!mController) {
+    return IPC_OK();
+  }
+
+  if (aStatus) {
+    mController->CreationSucceeded();
+  } else {
+    mController->CreationFailed();
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerParent::RecvError(const ErrorValue& aValue) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (mController) {
+    mController->ErrorPropagation(aValue);
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerParent::RecvNotifyLock(const bool& aCreated) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (mController) {
+    mController->NotifyLock(aCreated);
+  }
+
+  return IPC_OK();
+}
+
+IPCResult RemoteWorkerParent::RecvNotifyWebTransport(const bool& aCreated) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (mController) {
+    mController->NotifyWebTransport(aCreated);
+  }
+
+  return IPC_OK();
+}
+
+void RemoteWorkerParent::MaybeSendDelete() {
+  if (mDeleteSent) {
+    return;
+  }
+
+  // For some reason, if the following two lines are swapped, ASan says there's
+  // a UAF...
+  mDeleteSent = true;
+  Unused << Send__delete__(this);
+}
+
+IPCResult RemoteWorkerParent::RecvClose() {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (mController) {
+    mController->WorkerTerminated();
+  }
+
+  MaybeSendDelete();
+
+  return IPC_OK();
+}
+
+void RemoteWorkerParent::SetController(RemoteWorkerController* aController) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  mController = aController;
+}
+
+IPCResult RemoteWorkerParent::RecvSetServiceWorkerSkipWaitingFlag(
+    SetServiceWorkerSkipWaitingFlagResolver&& aResolve) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  if (mController) {
+    mController->SetServiceWorkerSkipWaitingFlag()->Then(
+        GetCurrentSerialEventTarget(), __func__,
+        [resolve = aResolve](bool /* unused */) { resolve(true); },
+        [resolve = aResolve](nsresult /* unused */) { resolve(false); });
+  } else {
+    aResolve(false);
+  }
+
+  return IPC_OK();
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerParent.h b/dom/workers/remoteworkers/RemoteWorkerParent.h
new file mode 100644
index 0000000000..811206eb91
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerParent.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: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_RemoteWorkerParent_h
+#define mozilla_dom_RemoteWorkerParent_h
+
+#include "mozilla/dom/PRemoteWorkerParent.h"
+
+namespace mozilla::dom {
+
+class RemoteWorkerController;
+
+/**
+ * PBackground-managed parent actor that is mutually associated with a single
+ * RemoteWorkerController.  Relays error/close events to the controller and in
+ * turns is told life-cycle events.
+ */
+class RemoteWorkerParent final : public PRemoteWorkerParent {
+  friend class PRemoteWorkerParent;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerParent, override);
+
+  RemoteWorkerParent();
+
+  void Initialize(bool aAlreadyRegistered = false);
+
+  void SetController(RemoteWorkerController* aController);
+
+  void MaybeSendDelete();
+
+ private:
+  ~RemoteWorkerParent();
+
+  already_AddRefed<PFetchEventOpProxyParent> AllocPFetchEventOpProxyParent(
+      const ParentToChildServiceWorkerFetchEventOpArgs& aArgs);
+
+  void ActorDestroy(mozilla::ipc::IProtocol::ActorDestroyReason) override;
+
+  mozilla::ipc::IPCResult RecvError(const ErrorValue& aValue);
+
+  mozilla::ipc::IPCResult RecvNotifyLock(const bool& aCreated);
+
+  mozilla::ipc::IPCResult RecvNotifyWebTransport(const bool& aCreated);
+
+  mozilla::ipc::IPCResult RecvClose();
+
+  mozilla::ipc::IPCResult RecvCreated(const bool& aStatus);
+
+  mozilla::ipc::IPCResult RecvSetServiceWorkerSkipWaitingFlag(
+      SetServiceWorkerSkipWaitingFlagResolver&& aResolve);
+
+  bool mDeleteSent = false;
+  RefPtr<RemoteWorkerController> mController;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerParent_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerService.cpp b/dom/workers/remoteworkers/RemoteWorkerService.cpp
new file mode 100644
index 0000000000..b62c551c22
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerService.cpp
@@ -0,0 +1,346 @@
+/* -*- 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 "RemoteWorkerService.h"
+
+#include "mozilla/dom/PRemoteWorkerParent.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/ipc/PBackgroundParent.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "nsIObserverService.h"
+#include "nsIThread.h"
+#include "nsThreadUtils.h"
+#include "nsXPCOMPrivate.h"
+#include "RemoteWorkerController.h"
+#include "RemoteWorkerServiceChild.h"
+#include "RemoteWorkerServiceParent.h"
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+namespace {
+
+StaticMutex sRemoteWorkerServiceMutex;
+StaticRefPtr<RemoteWorkerService> sRemoteWorkerService;
+
+}  // namespace
+
+/**
+ * Block shutdown until the RemoteWorkers have shutdown so that we do not try
+ * and shutdown the RemoteWorkerService "Worker Launcher" thread until they have
+ * cleanly shutdown.
+ *
+ * Note that this shutdown blocker is not used to initiate shutdown of any of
+ * the workers directly; their shutdown is initiated from PBackground in the
+ * parent process.  The shutdown blocker just exists to avoid races around
+ * shutting down the worker launcher thread after all of the workers have
+ * shutdown and torn down their actors.
+ *
+ * Currently, it should be the case that the ContentParent should want to keep
+ * the content processes alive until the RemoteWorkers have all reported their
+ * shutdown over IPC (on the "Worker Launcher" thread).  So for an orderly
+ * content process shutdown that is waiting for there to no longer be a reason
+ * to keep the content process alive, this blocker should only hang around for
+ * a brief period of time, helping smooth out lifecycle edge cases.
+ *
+ * In the event the content process is trying to shutdown while the
+ * RemoteWorkers think they should still be alive, it's possible that this
+ * blocker could expose the relevant logic error in the parent process if no
+ * attempt is made to shutdown the RemoteWorker.
+ *
+ * ## Major Implementation Note: This is not actually an nsIAsyncShutdownClient
+ *
+ * Until https://bugzilla.mozilla.org/show_bug.cgi?id=1760855 provides us with a
+ * non-JS implementation of nsIAsyncShutdownService, this implementation
+ * actually uses event loop spinning.  The patch on
+ * https://bugzilla.mozilla.org/show_bug.cgi?id=1775784 that changed us to use
+ * this hack can be reverted when the time is right.
+ *
+ * Event loop spinning is handled by `RemoteWorkerService::Observe` and it calls
+ * our exposed `ShouldBlockShutdown()` to know when to stop spinning.
+ */
+class RemoteWorkerServiceShutdownBlocker final {
+  ~RemoteWorkerServiceShutdownBlocker() = default;
+
+ public:
+  explicit RemoteWorkerServiceShutdownBlocker(RemoteWorkerService* aService)
+      : mService(aService), mBlockShutdown(true) {}
+
+  void RemoteWorkersAllGoneAllowShutdown() {
+    mService->FinishShutdown();
+    mService = nullptr;
+
+    mBlockShutdown = false;
+  }
+
+  bool ShouldBlockShutdown() { return mBlockShutdown; }
+
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerServiceShutdownBlocker);
+
+  RefPtr<RemoteWorkerService> mService;
+  bool mBlockShutdown;
+};
+
+RemoteWorkerServiceKeepAlive::RemoteWorkerServiceKeepAlive(
+    RemoteWorkerServiceShutdownBlocker* aBlocker)
+    : mBlocker(aBlocker) {
+  MOZ_ASSERT(NS_IsMainThread());
+}
+
+RemoteWorkerServiceKeepAlive::~RemoteWorkerServiceKeepAlive() {
+  // Dispatch a runnable to the main thread to tell the Shutdown Blocker to
+  // remove itself and notify the RemoteWorkerService it can finish its
+  // shutdown.  We dispatch this to the main thread even if we are already on
+  // the main thread.
+  nsCOMPtr<nsIRunnable> r =
+      NS_NewRunnableFunction(__func__, [blocker = std::move(mBlocker)] {
+        blocker->RemoteWorkersAllGoneAllowShutdown();
+      });
+  MOZ_ALWAYS_SUCCEEDS(
+      SchedulerGroup::Dispatch(TaskCategory::Other, r.forget()));
+}
+
+/* static */
+void RemoteWorkerService::Initialize() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  StaticMutexAutoLock lock(sRemoteWorkerServiceMutex);
+  MOZ_ASSERT(!sRemoteWorkerService);
+
+  RefPtr<RemoteWorkerService> service = new RemoteWorkerService();
+
+  // ## Content Process Initialization Case
+  //
+  // We are being told to initialize now that we know what our remote type is.
+  // Now is a fine time to call InitializeOnMainThread.
+  if (!XRE_IsParentProcess()) {
+    nsresult rv = service->InitializeOnMainThread();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return;
+    }
+
+    sRemoteWorkerService = service;
+    return;
+  }
+  // ## Parent Process Initialization Case
+  //
+  // Otherwise we are in the parent process and were invoked by
+  // nsLayoutStatics::Initialize.  We wait until profile-after-change to kick
+  // off the Worker Launcher thread and have it connect to PBackground.  This is
+  // an appropriate time for remote worker APIs to come online, especially
+  // because the PRemoteWorkerService mechanism needs processes to eagerly
+  // register themselves with PBackground since the design explicitly intends to
+  // avoid blocking on the main threads.  (Disclaimer: Currently, things block
+  // on the main thread.)
+
+  nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+  if (NS_WARN_IF(!obs)) {
+    return;
+  }
+
+  nsresult rv = obs->AddObserver(service, "profile-after-change", false);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  sRemoteWorkerService = service;
+}
+
+/* static */
+nsIThread* RemoteWorkerService::Thread() {
+  StaticMutexAutoLock lock(sRemoteWorkerServiceMutex);
+  MOZ_ASSERT(sRemoteWorkerService);
+  MOZ_ASSERT(sRemoteWorkerService->mThread);
+  return sRemoteWorkerService->mThread;
+}
+
+/* static */
+already_AddRefed<RemoteWorkerServiceKeepAlive>
+RemoteWorkerService::MaybeGetKeepAlive() {
+  StaticMutexAutoLock lock(sRemoteWorkerServiceMutex);
+  // In normal operation no one should be calling this without a service
+  // existing, so assert, but we'll also handle this being null as it is a
+  // plausible shutdown race.
+  MOZ_ASSERT(sRemoteWorkerService);
+  if (!sRemoteWorkerService) {
+    return nullptr;
+  }
+
+  // Note that this value can be null, but this all handles that.
+  auto lockedKeepAlive = sRemoteWorkerService->mKeepAlive.Lock();
+  RefPtr<RemoteWorkerServiceKeepAlive> extraRef = *lockedKeepAlive;
+  return extraRef.forget();
+}
+
+nsresult RemoteWorkerService::InitializeOnMainThread() {
+  // I would like to call this thread "DOM Remote Worker Launcher", but the max
+  // length is 16 chars.
+  nsresult rv = NS_NewNamedThread("Worker Launcher", getter_AddRefs(mThread));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+  if (NS_WARN_IF(!obs)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  rv = obs->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  mShutdownBlocker = new RemoteWorkerServiceShutdownBlocker(this);
+
+  {
+    RefPtr<RemoteWorkerServiceKeepAlive> keepAlive =
+        new RemoteWorkerServiceKeepAlive(mShutdownBlocker);
+
+    auto lockedKeepAlive = mKeepAlive.Lock();
+    *lockedKeepAlive = std::move(keepAlive);
+  }
+
+  RefPtr<RemoteWorkerService> self = this;
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      "InitializeThread", [self]() { self->InitializeOnTargetThread(); });
+
+  rv = mThread->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+RemoteWorkerService::RemoteWorkerService()
+    : mKeepAlive(nullptr, "RemoteWorkerService::mKeepAlive") {
+  MOZ_ASSERT(NS_IsMainThread());
+}
+
+RemoteWorkerService::~RemoteWorkerService() = default;
+
+void RemoteWorkerService::InitializeOnTargetThread() {
+  MOZ_ASSERT(mThread);
+  MOZ_ASSERT(mThread->IsOnCurrentThread());
+
+  PBackgroundChild* backgroundActor =
+      BackgroundChild::GetOrCreateForCurrentThread();
+  if (NS_WARN_IF(!backgroundActor)) {
+    return;
+  }
+
+  RefPtr<RemoteWorkerServiceChild> serviceActor =
+      MakeAndAddRef<RemoteWorkerServiceChild>();
+  if (NS_WARN_IF(!backgroundActor->SendPRemoteWorkerServiceConstructor(
+          serviceActor))) {
+    return;
+  }
+
+  // Now we are ready!
+  mActor = serviceActor;
+}
+
+void RemoteWorkerService::CloseActorOnTargetThread() {
+  MOZ_ASSERT(mThread);
+  MOZ_ASSERT(mThread->IsOnCurrentThread());
+
+  // If mActor is nullptr it means that initialization failed.
+  if (mActor) {
+    // Here we need to shutdown the IPC protocol.
+    mActor->Send__delete__(mActor);
+    mActor = nullptr;
+  }
+}
+
+NS_IMETHODIMP
+RemoteWorkerService::Observe(nsISupports* aSubject, const char* aTopic,
+                             const char16_t* aData) {
+  if (!strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID)) {
+    MOZ_ASSERT(mThread);
+
+    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+    if (obs) {
+      obs->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
+    }
+
+    // Note that nsObserverList::NotifyObservers will hold a strong reference to
+    // our instance throughout the entire duration of this call, so it is not
+    // necessary for us to hold a kungFuDeathGrip here.
+
+    // Drop our keep-alive.  This could immediately result in our blocker saying
+    // it's okay for us to shutdown.  SpinEventLoopUntil checks the predicate
+    // before spinning, so in the ideal case we will not spin the loop at all.
+    BeginShutdown();
+
+    MOZ_ALWAYS_TRUE(SpinEventLoopUntil(
+        "RemoteWorkerService::Observe"_ns,
+        [&]() { return !mShutdownBlocker->ShouldBlockShutdown(); }));
+
+    mShutdownBlocker = nullptr;
+
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(!strcmp(aTopic, "profile-after-change"));
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+  if (obs) {
+    obs->RemoveObserver(this, "profile-after-change");
+  }
+
+  return InitializeOnMainThread();
+}
+
+void RemoteWorkerService::BeginShutdown() {
+  // Drop our keepalive reference which may allow near-immediate removal of the
+  // blocker.
+  auto lockedKeepAlive = mKeepAlive.Lock();
+  *lockedKeepAlive = nullptr;
+}
+
+void RemoteWorkerService::FinishShutdown() {
+  // Clear the singleton before spinning the event loop when shutting down the
+  // thread so that MaybeGetKeepAlive() can assert if there are any late calls
+  // and to better reflect the actual state.
+  //
+  // Our caller, the RemoteWorkerServiceShutdownBlocker, will continue to hold a
+  // strong reference to us until we return from this call, so there are no
+  // lifecycle implications to dropping this reference.
+  {
+    StaticMutexAutoLock lock(sRemoteWorkerServiceMutex);
+    sRemoteWorkerService = nullptr;
+  }
+
+  RefPtr<RemoteWorkerService> self = this;
+  nsCOMPtr<nsIRunnable> r =
+      NS_NewRunnableFunction("RemoteWorkerService::CloseActorOnTargetThread",
+                             [self]() { self->CloseActorOnTargetThread(); });
+
+  mThread->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+
+  // We've posted a shutdown message; now shutdown the thread.  This will spin
+  // a nested event loop waiting for the thread to process all pending events
+  // (including the just dispatched CloseActorOnTargetThread which will close
+  // the actor), ensuring to block main thread shutdown long enough to avoid
+  // races.
+  mThread->Shutdown();
+  mThread = nullptr;
+}
+
+NS_IMPL_ISUPPORTS(RemoteWorkerService, nsIObserver)
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerService.h b/dom/workers/remoteworkers/RemoteWorkerService.h
new file mode 100644
index 0000000000..9e05e3958b
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerService.h
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_RemoteWorkerService_h
+#define mozilla_dom_RemoteWorkerService_h
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/DataMutex.h"
+#include "nsCOMPtr.h"
+#include "nsIObserver.h"
+#include "nsISupportsImpl.h"
+
+class nsIThread;
+
+namespace mozilla::dom {
+
+class RemoteWorkerService;
+class RemoteWorkerServiceChild;
+class RemoteWorkerServiceShutdownBlocker;
+
+/**
+ * Refcounted lifecycle helper; when its refcount goes to zero its destructor
+ * will call RemoteWorkerService::Shutdown() which will remove the shutdown
+ * blocker and shutdown the "Worker Launcher" thread.
+ *
+ * The RemoteWorkerService itself will hold a reference to this singleton which
+ * it will use to hand out additional refcounts to RemoteWorkerChild instances.
+ * When the shutdown blocker is notified that it's time to shutdown, the
+ * RemoteWorkerService's reference will be dropped.
+ */
+class RemoteWorkerServiceKeepAlive {
+ public:
+  explicit RemoteWorkerServiceKeepAlive(
+      RemoteWorkerServiceShutdownBlocker* aBlocker);
+
+ private:
+  ~RemoteWorkerServiceKeepAlive();
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RemoteWorkerServiceKeepAlive);
+
+  RefPtr<RemoteWorkerServiceShutdownBlocker> mBlocker;
+};
+
+/**
+ * Every process has a RemoteWorkerService which does the actual spawning of
+ * RemoteWorkerChild instances. The RemoteWorkerService creates a "Worker
+ * Launcher" thread at initialization on which it creates a
+ * RemoteWorkerServiceChild to service spawn requests. The thread is exposed as
+ * RemoteWorkerService::Thread(). A new/distinct thread is used because we
+ * (eventually) don't want to deal with main-thread contention, content
+ * processes have no equivalent of a PBackground thread, and actors are bound to
+ * specific threads.
+ *
+ * (Disclaimer: currently most RemoteWorkerOps need to happen on the main thread
+ * because the main-thread ends up as the owner of the worker and all
+ * manipulation of the worker must happen from the owning thread.)
+ */
+class RemoteWorkerService final : public nsIObserver {
+  friend class RemoteWorkerServiceShutdownBlocker;
+  friend class RemoteWorkerServiceKeepAlive;
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  // To be called when a process is initialized on main-thread.
+  static void Initialize();
+
+  static nsIThread* Thread();
+
+  // Called by RemoteWorkerChild instances on the "Worker Launcher" thread at
+  // their creation to assist in tracking when it's safe to shutdown the
+  // RemoteWorkerService and "Worker Launcher" thread.  This method will return
+  // a null pointer if the RemoteWorkerService has already begun shutdown.
+  //
+  // This is somewhat awkwardly a static method because the RemoteWorkerChild
+  // instances are not managed by RemoteWorkerServiceChild, but instead are
+  // managed by PBackground(Child).  So we either need to find the
+  // RemoteWorkerService via the hidden singleton or by having the
+  // RemoteWorkerChild use PBackgroundChild::ManagedPRemoteWorkerServiceChild()
+  // to locate the instance.  We are choosing to use the singleton because we
+  // already need to acquire a mutex in the call regardless and the upcoming
+  // refactorings may want to start using new toplevel protocols and this will
+  // avoid requiring a change when that happens.
+  static already_AddRefed<RemoteWorkerServiceKeepAlive> MaybeGetKeepAlive();
+
+ private:
+  RemoteWorkerService();
+  ~RemoteWorkerService();
+
+  nsresult InitializeOnMainThread();
+
+  void InitializeOnTargetThread();
+
+  void CloseActorOnTargetThread();
+
+  // Called by RemoteWorkerServiceShutdownBlocker when it's time to drop the
+  // RemoteWorkerServiceKeepAlive reference.
+  void BeginShutdown();
+
+  // Called by RemoteWorkerServiceShutdownBlocker when the blocker has been
+  // removed and it's safe to shutdown the "Worker Launcher" thread.
+  void FinishShutdown();
+
+  nsCOMPtr<nsIThread> mThread;
+  RefPtr<RemoteWorkerServiceChild> mActor;
+  // The keep-alive is set and cleared on the main thread but we will hand out
+  // additional references to it from the "Worker Launcher" thread, so it's
+  // appropriate to use a mutex.  (Alternately we could have used a ThreadBound
+  // and set and cleared on the "Worker Launcher" thread, but that would
+  // involve more moving parts and could have complicated edge cases.)
+  DataMutex<RefPtr<RemoteWorkerServiceKeepAlive>> mKeepAlive;
+  // In order to poll the blocker to know when we can stop spinning the event
+  // loop at shutdown, we retain a reference to the blocker.
+  RefPtr<RemoteWorkerServiceShutdownBlocker> mShutdownBlocker;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerService_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerServiceChild.cpp b/dom/workers/remoteworkers/RemoteWorkerServiceChild.cpp
new file mode 100644
index 0000000000..100908064e
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerServiceChild.cpp
@@ -0,0 +1,16 @@
+/* -*- 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 "RemoteWorkerServiceChild.h"
+#include "RemoteWorkerController.h"
+
+namespace mozilla::dom {
+
+RemoteWorkerServiceChild::RemoteWorkerServiceChild() = default;
+
+RemoteWorkerServiceChild::~RemoteWorkerServiceChild() = default;
+
+}  // namespace mozilla::dom
diff --git a/dom/workers/remoteworkers/RemoteWorkerServiceChild.h b/dom/workers/remoteworkers/RemoteWorkerServiceChild.h
new file mode 100644
index 0000000000..41ae879b29
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerServiceChild.h
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_RemoteWorkerServiceChild_h
+#define mozilla_dom_RemoteWorkerServiceChild_h
+
+#include "mozilla/dom/PRemoteWorkerServiceChild.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla::dom {
+
+class RemoteWorkerController;
+class RemoteWorkerData;
+
+/**
+ * "Worker Launcher"-thread child actor created by the RemoteWorkerService to
+ * register itself with the PBackground RemoteWorkerManager in the parent.
+ */
+class RemoteWorkerServiceChild final : public PRemoteWorkerServiceChild {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerServiceChild, final)
+
+  RemoteWorkerServiceChild();
+
+ private:
+  ~RemoteWorkerServiceChild();
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerServiceChild_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerServiceParent.cpp b/dom/workers/remoteworkers/RemoteWorkerServiceParent.cpp
new file mode 100644
index 0000000000..c7fd5ea6c8
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerServiceParent.cpp
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RemoteWorkerServiceParent.h"
+#include "RemoteWorkerManager.h"
+#include "mozilla/ipc/BackgroundParent.h"
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+RemoteWorkerServiceParent::RemoteWorkerServiceParent()
+    : mManager(RemoteWorkerManager::GetOrCreate()) {}
+
+RemoteWorkerServiceParent::~RemoteWorkerServiceParent() = default;
+
+void RemoteWorkerServiceParent::Initialize(const nsACString& aRemoteType) {
+  AssertIsOnBackgroundThread();
+  mRemoteType = aRemoteType;
+  mManager->RegisterActor(this);
+}
+
+void RemoteWorkerServiceParent::ActorDestroy(IProtocol::ActorDestroyReason) {
+  AssertIsOnBackgroundThread();
+  mManager->UnregisterActor(this);
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/dom/workers/remoteworkers/RemoteWorkerServiceParent.h b/dom/workers/remoteworkers/RemoteWorkerServiceParent.h
new file mode 100644
index 0000000000..31ed29a78c
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerServiceParent.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_dom_RemoteWorkerServiceParent_h
+#define mozilla_dom_RemoteWorkerServiceParent_h
+
+#include "mozilla/dom/PRemoteWorkerServiceParent.h"
+#include "mozilla/dom/RemoteType.h"
+
+namespace mozilla::dom {
+
+class RemoteWorkerManager;
+
+/**
+ * PBackground parent actor that registers with the PBackground
+ * RemoteWorkerManager and used to relay spawn requests.
+ */
+class RemoteWorkerServiceParent final : public PRemoteWorkerServiceParent {
+ public:
+  RemoteWorkerServiceParent();
+  NS_INLINE_DECL_REFCOUNTING(RemoteWorkerServiceParent, override);
+
+  void ActorDestroy(mozilla::ipc::IProtocol::ActorDestroyReason) override;
+
+  void Initialize(const nsACString& aRemoteType);
+
+  nsCString GetRemoteType() const { return mRemoteType; }
+
+ private:
+  ~RemoteWorkerServiceParent();
+
+  RefPtr<RemoteWorkerManager> mManager;
+  nsCString mRemoteType = NOT_REMOTE_TYPE;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_RemoteWorkerServiceParent_h
diff --git a/dom/workers/remoteworkers/RemoteWorkerTypes.ipdlh b/dom/workers/remoteworkers/RemoteWorkerTypes.ipdlh
new file mode 100644
index 0000000000..67a23e9aae
--- /dev/null
+++ b/dom/workers/remoteworkers/RemoteWorkerTypes.ipdlh
@@ -0,0 +1,123 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include ClientIPCTypes;
+include IPCServiceWorkerDescriptor;
+include IPCServiceWorkerRegistrationDescriptor;
+include PBackgroundSharedTypes;
+include URIParams;
+include DOMTypes;
+include NeckoChannelParams;
+include ProtocolTypes;
+
+include "mozilla/dom/ClientIPCUtils.h";
+include "mozilla/dom/ReferrerInfoUtils.h";
+include "mozilla/dom/WorkerIPCUtils.h";
+
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+using mozilla::dom::RequestCredentials from "mozilla/dom/RequestBinding.h";
+using mozilla::StorageAccess from "mozilla/StorageAccess.h";
+using mozilla::OriginTrials from "mozilla/OriginTrialsIPCUtils.h";
+using mozilla::dom::WorkerType from "mozilla/dom/WorkerBinding.h";
+
+namespace mozilla {
+namespace dom {
+
+struct ServiceWorkerData {
+  IPCServiceWorkerDescriptor descriptor;
+  IPCServiceWorkerRegistrationDescriptor registrationDescriptor;
+  nsString cacheName;
+  uint32_t loadFlags;
+  nsString id;
+};
+
+union OptionalServiceWorkerData {
+  void_t;
+  ServiceWorkerData;
+};
+
+struct RemoteWorkerData
+{
+  // This should only be used for devtools.
+  nsString originalScriptURL;
+
+  // It is important to pass these as URIParams instead of strings for blob
+  // URLs: they carry an additional bit of state with them (mIsRevoked) that
+  // gives us a chance to use them, even after they've been revoked. Because
+  // we're asynchronously calling into the parent process before potentially
+  // loading the worker, it is important to keep this state. Note that this
+  // isn't a panacea: once the URL has been revoked, it'll give the worker 5
+  // seconds to actually load it; so it's possible to still fail to load the
+  // blob URL if it takes too long to do the round trip.
+  URIParams baseScriptURL;
+  URIParams resolvedScriptURL;
+
+  nsString name;
+  WorkerType type;
+  RequestCredentials credentials;
+
+  PrincipalInfo loadingPrincipalInfo;
+  PrincipalInfo principalInfo;
+  PrincipalInfo partitionedPrincipalInfo;
+
+  bool useRegularPrincipal;
+  bool hasStorageAccessPermissionGranted;
+
+  CookieJarSettingsArgs cookieJarSettings;
+
+  nsCString domain;
+
+  bool isSecureContext;
+
+  IPCClientInfo? clientInfo;
+
+  nullable nsIReferrerInfo referrerInfo;
+
+  StorageAccess storageAccess;
+
+  bool isThirdPartyContextToTopWindow;
+
+  bool shouldResistFingerprinting;
+
+  OriginTrials originTrials;
+
+  OptionalServiceWorkerData serviceWorkerData;
+
+  nsID agentClusterId;
+
+  // Child process remote type where the worker should only run on.
+  nsCString remoteType;
+};
+
+// ErrorData/ErrorDataNote correspond to WorkerErrorReport/WorkerErrorNote
+// which in turn correspond to JSErrorReport/JSErrorNotes which allows JS to
+// report complicated errors such as redeclarations that involve multiple
+// distinct lines.  For more generic error-propagation IPC structures, see bug
+// 1357463 on making ErrorResult usable over IPC.
+
+struct ErrorDataNote {
+  uint32_t lineNumber;
+  uint32_t columnNumber;
+  nsString message;
+  nsString filename;
+};
+
+struct ErrorData {
+  bool isWarning;
+  uint32_t lineNumber;
+  uint32_t columnNumber;
+  nsString message;
+  nsString filename;
+  nsString line;
+  ErrorDataNote[] notes;
+};
+
+union ErrorValue {
+  nsresult;
+  ErrorData;
+  void_t;
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/workers/remoteworkers/moz.build b/dom/workers/remoteworkers/moz.build
new file mode 100644
index 0000000000..9983b7dd10
--- /dev/null
+++ b/dom/workers/remoteworkers/moz.build
@@ -0,0 +1,45 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.dom += [
+    "RemoteWorkerChild.h",
+    "RemoteWorkerController.h",
+    "RemoteWorkerControllerChild.h",
+    "RemoteWorkerControllerParent.h",
+    "RemoteWorkerManager.h",
+    "RemoteWorkerParent.h",
+    "RemoteWorkerService.h",
+    "RemoteWorkerServiceChild.h",
+    "RemoteWorkerServiceParent.h",
+]
+
+UNIFIED_SOURCES += [
+    "RemoteWorkerChild.cpp",
+    "RemoteWorkerController.cpp",
+    "RemoteWorkerControllerChild.cpp",
+    "RemoteWorkerControllerParent.cpp",
+    "RemoteWorkerManager.cpp",
+    "RemoteWorkerParent.cpp",
+    "RemoteWorkerService.cpp",
+    "RemoteWorkerServiceChild.cpp",
+    "RemoteWorkerServiceParent.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/dom/serviceworkers",
+    "/xpcom/build",
+]
+
+IPDL_SOURCES += [
+    "PRemoteWorker.ipdl",
+    "PRemoteWorkerController.ipdl",
+    "PRemoteWorkerService.ipdl",
+    "RemoteWorkerTypes.ipdlh",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"