Add m-esr52 at 52.6.0

1 files changed, 777 insertions, 0 deletions

diff --git a/dom/workers/WorkerRunnable.cpp b/dom/workers/WorkerRunnable.cpp
new file mode 100644
index 000000000..1e16d7254
--- /dev/null
+++ b/dom/workers/WorkerRunnable.cpp
@@ -0,0 +1,777 @@
+/* -*- 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 "WorkerRunnable.h"
+
+#include "nsGlobalWindow.h"
+#include "nsIEventTarget.h"
+#include "nsIGlobalObject.h"
+#include "nsIRunnable.h"
+#include "nsThreadUtils.h"
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/Telemetry.h"
+
+#include "js/RootingAPI.h"
+#include "js/Value.h"
+
+#include "WorkerPrivate.h"
+#include "WorkerScope.h"
+
+USING_WORKERS_NAMESPACE
+
+namespace {
+
+const nsIID kWorkerRunnableIID = {
+  0x320cc0b5, 0xef12, 0x4084, { 0x88, 0x6e, 0xca, 0x6a, 0x81, 0xe4, 0x1d, 0x68 }
+};
+
+} // namespace
+
+#ifdef DEBUG
+WorkerRunnable::WorkerRunnable(WorkerPrivate* aWorkerPrivate,
+                               TargetAndBusyBehavior aBehavior)
+: mWorkerPrivate(aWorkerPrivate), mBehavior(aBehavior), mCanceled(0),
+  mCallingCancelWithinRun(false)
+{
+  MOZ_ASSERT(aWorkerPrivate);
+}
+#endif
+
+bool
+WorkerRunnable::IsDebuggerRunnable() const
+{
+  return false;
+}
+
+nsIGlobalObject*
+WorkerRunnable::DefaultGlobalObject() const
+{
+  if (IsDebuggerRunnable()) {
+    return mWorkerPrivate->DebuggerGlobalScope();
+  } else {
+    return mWorkerPrivate->GlobalScope();
+  }
+}
+
+bool
+WorkerRunnable::PreDispatch(WorkerPrivate* aWorkerPrivate)
+{
+#ifdef DEBUG
+  MOZ_ASSERT(aWorkerPrivate);
+
+  switch (mBehavior) {
+    case ParentThreadUnchangedBusyCount:
+      aWorkerPrivate->AssertIsOnWorkerThread();
+      break;
+
+    case WorkerThreadModifyBusyCount:
+    case WorkerThreadUnchangedBusyCount:
+      aWorkerPrivate->AssertIsOnParentThread();
+      break;
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unknown behavior!");
+  }
+#endif
+
+  if (mBehavior == WorkerThreadModifyBusyCount) {
+    return aWorkerPrivate->ModifyBusyCount(true);
+  }
+
+  return true;
+}
+
+bool
+WorkerRunnable::Dispatch()
+{
+  bool ok = PreDispatch(mWorkerPrivate);
+  if (ok) {
+    ok = DispatchInternal();
+  }
+  PostDispatch(mWorkerPrivate, ok);
+  return ok;
+}
+
+bool
+WorkerRunnable::DispatchInternal()
+{
+  RefPtr<WorkerRunnable> runnable(this);
+
+  if (mBehavior == WorkerThreadModifyBusyCount ||
+      mBehavior == WorkerThreadUnchangedBusyCount) {
+    if (IsDebuggerRunnable()) {
+      return NS_SUCCEEDED(mWorkerPrivate->DispatchDebuggerRunnable(runnable.forget()));
+    } else {
+      return NS_SUCCEEDED(mWorkerPrivate->Dispatch(runnable.forget()));
+    }
+  }
+
+  MOZ_ASSERT(mBehavior == ParentThreadUnchangedBusyCount);
+
+  if (WorkerPrivate* parent = mWorkerPrivate->GetParent()) {
+    return NS_SUCCEEDED(parent->Dispatch(runnable.forget()));
+  }
+
+  return NS_SUCCEEDED(mWorkerPrivate->DispatchToMainThread(runnable.forget()));
+}
+
+void
+WorkerRunnable::PostDispatch(WorkerPrivate* aWorkerPrivate,
+                             bool aDispatchResult)
+{
+  MOZ_ASSERT(aWorkerPrivate);
+
+#ifdef DEBUG
+  switch (mBehavior) {
+    case ParentThreadUnchangedBusyCount:
+      aWorkerPrivate->AssertIsOnWorkerThread();
+      break;
+
+    case WorkerThreadModifyBusyCount:
+      aWorkerPrivate->AssertIsOnParentThread();
+      break;
+
+    case WorkerThreadUnchangedBusyCount:
+      aWorkerPrivate->AssertIsOnParentThread();
+      break;
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unknown behavior!");
+  }
+#endif
+
+  if (!aDispatchResult) {
+    if (mBehavior == WorkerThreadModifyBusyCount) {
+      aWorkerPrivate->ModifyBusyCount(false);
+    }
+  }
+}
+
+bool
+WorkerRunnable::PreRun(WorkerPrivate* aWorkerPrivate)
+{
+  return true;
+}
+
+void
+WorkerRunnable::PostRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate,
+                        bool aRunResult)
+{
+  MOZ_ASSERT(aCx);
+  MOZ_ASSERT(aWorkerPrivate);
+
+#ifdef DEBUG
+  switch (mBehavior) {
+    case ParentThreadUnchangedBusyCount:
+      aWorkerPrivate->AssertIsOnParentThread();
+      break;
+
+    case WorkerThreadModifyBusyCount:
+      aWorkerPrivate->AssertIsOnWorkerThread();
+      break;
+
+    case WorkerThreadUnchangedBusyCount:
+      aWorkerPrivate->AssertIsOnWorkerThread();
+      break;
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unknown behavior!");
+  }
+#endif
+
+  if (mBehavior == WorkerThreadModifyBusyCount) {
+    aWorkerPrivate->ModifyBusyCountFromWorker(false);
+  }
+}
+
+// static
+WorkerRunnable*
+WorkerRunnable::FromRunnable(nsIRunnable* aRunnable)
+{
+  MOZ_ASSERT(aRunnable);
+
+  WorkerRunnable* runnable;
+  nsresult rv = aRunnable->QueryInterface(kWorkerRunnableIID,
+                                          reinterpret_cast<void**>(&runnable));
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(runnable);
+  return runnable;
+}
+
+NS_IMPL_ADDREF(WorkerRunnable)
+NS_IMPL_RELEASE(WorkerRunnable)
+
+NS_INTERFACE_MAP_BEGIN(WorkerRunnable)
+  NS_INTERFACE_MAP_ENTRY(nsIRunnable)
+  NS_INTERFACE_MAP_ENTRY(nsICancelableRunnable)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIRunnable)
+  // kWorkerRunnableIID is special in that it does not AddRef its result.
+  if (aIID.Equals(kWorkerRunnableIID)) {
+    *aInstancePtr = this;
+    return NS_OK;
+  }
+  else
+NS_INTERFACE_MAP_END
+
+NS_IMETHODIMP
+WorkerRunnable::Run()
+{
+  bool targetIsWorkerThread = mBehavior == WorkerThreadModifyBusyCount ||
+                              mBehavior == WorkerThreadUnchangedBusyCount;
+
+#ifdef DEBUG
+  MOZ_ASSERT_IF(mCallingCancelWithinRun, targetIsWorkerThread);
+  if (targetIsWorkerThread) {
+    mWorkerPrivate->AssertIsOnWorkerThread();
+  }
+  else {
+    MOZ_ASSERT(mBehavior == ParentThreadUnchangedBusyCount);
+    mWorkerPrivate->AssertIsOnParentThread();
+  }
+#endif
+
+  if (IsCanceled() && !mCallingCancelWithinRun) {
+    return NS_OK;
+  }
+
+  if (targetIsWorkerThread &&
+      mWorkerPrivate->AllPendingRunnablesShouldBeCanceled() &&
+      !IsCanceled() && !mCallingCancelWithinRun) {
+
+    // Prevent recursion.
+    mCallingCancelWithinRun = true;
+
+    Cancel();
+
+    MOZ_ASSERT(mCallingCancelWithinRun);
+    mCallingCancelWithinRun = false;
+
+    MOZ_ASSERT(IsCanceled(), "Subclass Cancel() didn't set IsCanceled()!");
+
+    if (mBehavior == WorkerThreadModifyBusyCount) {
+      mWorkerPrivate->ModifyBusyCountFromWorker(false);
+    }
+
+    return NS_OK;
+  }
+
+  bool result = PreRun(mWorkerPrivate);
+  if (!result) {
+    MOZ_ASSERT(targetIsWorkerThread,
+               "The only PreRun implementation that can fail is "
+               "ScriptExecutorRunnable");
+    mWorkerPrivate->AssertIsOnWorkerThread();
+    MOZ_ASSERT(!JS_IsExceptionPending(mWorkerPrivate->GetJSContext()));
+    // We can't enter a useful compartment on the JSContext here; just pass it
+    // in as-is.
+    PostRun(mWorkerPrivate->GetJSContext(), mWorkerPrivate, false);
+    return NS_ERROR_FAILURE;
+  }
+
+  // Track down the appropriate global, if any, to use for the AutoEntryScript.
+  nsCOMPtr<nsIGlobalObject> globalObject;
+  bool isMainThread = !targetIsWorkerThread && !mWorkerPrivate->GetParent();
+  MOZ_ASSERT(isMainThread == NS_IsMainThread());
+  RefPtr<WorkerPrivate> kungFuDeathGrip;
+  if (targetIsWorkerThread) {
+    JSContext* cx = GetCurrentThreadJSContext();
+    if (NS_WARN_IF(!cx)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    JSObject* global = JS::CurrentGlobalOrNull(cx);
+    if (global) {
+      globalObject = xpc::NativeGlobal(global);
+    } else {
+      globalObject = DefaultGlobalObject();
+    }
+
+    // We may still not have a globalObject here: in the case of
+    // CompileScriptRunnable, we don't actually create the global object until
+    // we have the script data, which happens in a syncloop under
+    // CompileScriptRunnable::WorkerRun, so we can't assert that it got created
+    // in the PreRun call above.
+  } else {
+    kungFuDeathGrip = mWorkerPrivate;
+    if (isMainThread) {
+      globalObject = nsGlobalWindow::Cast(mWorkerPrivate->GetWindow());
+    } else {
+      globalObject = mWorkerPrivate->GetParent()->GlobalScope();
+    }
+  }
+
+  // We might run script as part of WorkerRun, so we need an AutoEntryScript.
+  // This is part of the HTML spec for workers at:
+  // http://www.whatwg.org/specs/web-apps/current-work/#run-a-worker
+  // If we don't have a globalObject we have to use an AutoJSAPI instead, but
+  // this is OK as we won't be running script in these circumstances.
+  Maybe<mozilla::dom::AutoJSAPI> maybeJSAPI;
+  Maybe<mozilla::dom::AutoEntryScript> aes;
+  JSContext* cx;
+  AutoJSAPI* jsapi;
+  if (globalObject) {
+    aes.emplace(globalObject, "Worker runnable", isMainThread);
+    jsapi = aes.ptr();
+    cx = aes->cx();
+  } else {
+    maybeJSAPI.emplace();
+    maybeJSAPI->Init();
+    jsapi = maybeJSAPI.ptr();
+    cx = jsapi->cx();
+  }
+
+  // Note that we can't assert anything about mWorkerPrivate->GetWrapper()
+  // existing, since it may in fact have been GCed (and we may be one of the
+  // runnables cleaning up the worker as a result).
+
+  // If we are on the parent thread and that thread is not the main thread,
+  // then we must be a dedicated worker (because there are no
+  // Shared/ServiceWorkers whose parent is itself a worker) and then we
+  // definitely have a globalObject.  If it _is_ the main thread, globalObject
+  // can be null for workers started from JSMs or other non-window contexts,
+  // sadly.
+  MOZ_ASSERT_IF(!targetIsWorkerThread && !isMainThread,
+                mWorkerPrivate->IsDedicatedWorker() && globalObject);
+
+  // If we're on the parent thread we might be in a null compartment in the
+  // situation described above when globalObject is null.  Make sure to enter
+  // the compartment of the worker's reflector if there is one.  There might
+  // not be one if we're just starting to compile the script for this worker.
+  Maybe<JSAutoCompartment> ac;
+  if (!targetIsWorkerThread && mWorkerPrivate->GetWrapper()) {
+    // If we're on the parent thread and have a reflector and a globalObject,
+    // then the compartments of cx, globalObject, and the worker's reflector
+    // should all match.
+    MOZ_ASSERT_IF(globalObject,
+                  js::GetObjectCompartment(mWorkerPrivate->GetWrapper()) ==
+                    js::GetContextCompartment(cx));
+    MOZ_ASSERT_IF(globalObject,
+                  js::GetObjectCompartment(mWorkerPrivate->GetWrapper()) ==
+                    js::GetObjectCompartment(globalObject->GetGlobalJSObject()));
+
+    // If we're on the parent thread and have a reflector, then our
+    // JSContext had better be either in the null compartment (and hence
+    // have no globalObject) or in the compartment of our reflector.
+    MOZ_ASSERT(!js::GetContextCompartment(cx) ||
+               js::GetObjectCompartment(mWorkerPrivate->GetWrapper()) ==
+                 js::GetContextCompartment(cx),
+               "Must either be in the null compartment or in our reflector "
+               "compartment");
+
+    ac.emplace(cx, mWorkerPrivate->GetWrapper());
+  }
+
+  MOZ_ASSERT(!jsapi->HasException());
+  result = WorkerRun(cx, mWorkerPrivate);
+  MOZ_ASSERT_IF(result, !jsapi->HasException());
+  jsapi->ReportException();
+
+  // We can't even assert that this didn't create our global, since in the case
+  // of CompileScriptRunnable it _does_.
+
+  // It would be nice to avoid passing a JSContext to PostRun, but in the case
+  // of ScriptExecutorRunnable we need to know the current compartment on the
+  // JSContext (the one we set up based on the global returned from PreRun) so
+  // that we can sanely do exception reporting.  In particular, we want to make
+  // sure that we do our JS_SetPendingException while still in that compartment,
+  // because otherwise we might end up trying to create a cross-compartment
+  // wrapper when we try to move the JS exception from our runnable's
+  // ErrorResult to the JSContext, and that's not desirable in this case.
+  //
+  // We _could_ skip passing a JSContext here and then in
+  // ScriptExecutorRunnable::PostRun end up grabbing it from the WorkerPrivate
+  // and looking at its current compartment.  But that seems like slightly weird
+  // action-at-a-distance...
+  //
+  // In any case, we do NOT try to change the compartment on the JSContext at
+  // this point; in the one case in which we could do that
+  // (CompileScriptRunnable) it actually doesn't matter which compartment we're
+  // in for PostRun.
+  PostRun(cx, mWorkerPrivate, result);
+  MOZ_ASSERT(!jsapi->HasException());
+
+  return result ? NS_OK : NS_ERROR_FAILURE;
+}
+
+nsresult
+WorkerRunnable::Cancel()
+{
+  uint32_t canceledCount = ++mCanceled;
+
+  MOZ_ASSERT(canceledCount, "Cancel() overflow!");
+
+  // The docs say that Cancel() should not be called more than once and that we
+  // should throw NS_ERROR_UNEXPECTED if it is.
+  return (canceledCount == 1) ? NS_OK : NS_ERROR_UNEXPECTED;
+}
+
+void
+WorkerDebuggerRunnable::PostDispatch(WorkerPrivate* aWorkerPrivate,
+                                     bool aDispatchResult)
+{
+}
+
+WorkerSyncRunnable::WorkerSyncRunnable(WorkerPrivate* aWorkerPrivate,
+                                       nsIEventTarget* aSyncLoopTarget)
+: WorkerRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount),
+  mSyncLoopTarget(aSyncLoopTarget)
+{
+#ifdef DEBUG
+  if (mSyncLoopTarget) {
+    mWorkerPrivate->AssertValidSyncLoop(mSyncLoopTarget);
+  }
+#endif
+}
+
+WorkerSyncRunnable::WorkerSyncRunnable(
+                               WorkerPrivate* aWorkerPrivate,
+                               already_AddRefed<nsIEventTarget>&& aSyncLoopTarget)
+: WorkerRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount),
+  mSyncLoopTarget(aSyncLoopTarget)
+{
+#ifdef DEBUG
+  if (mSyncLoopTarget) {
+    mWorkerPrivate->AssertValidSyncLoop(mSyncLoopTarget);
+  }
+#endif
+}
+
+WorkerSyncRunnable::~WorkerSyncRunnable()
+{
+}
+
+bool
+WorkerSyncRunnable::DispatchInternal()
+{
+  if (mSyncLoopTarget) {
+    RefPtr<WorkerSyncRunnable> runnable(this);
+    return NS_SUCCEEDED(mSyncLoopTarget->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL));
+  }
+
+  return WorkerRunnable::DispatchInternal();
+}
+
+void
+MainThreadWorkerSyncRunnable::PostDispatch(WorkerPrivate* aWorkerPrivate,
+                                           bool aDispatchResult)
+{
+}
+
+MainThreadStopSyncLoopRunnable::MainThreadStopSyncLoopRunnable(
+                               WorkerPrivate* aWorkerPrivate,
+                               already_AddRefed<nsIEventTarget>&& aSyncLoopTarget,
+                               bool aResult)
+: WorkerSyncRunnable(aWorkerPrivate, Move(aSyncLoopTarget)), mResult(aResult)
+{
+  AssertIsOnMainThread();
+#ifdef DEBUG
+  mWorkerPrivate->AssertValidSyncLoop(mSyncLoopTarget);
+#endif
+}
+
+nsresult
+MainThreadStopSyncLoopRunnable::Cancel()
+{
+  nsresult rv = Run();
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "Run() failed");
+
+  nsresult rv2 = WorkerSyncRunnable::Cancel();
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv2), "Cancel() failed");
+
+  return NS_FAILED(rv) ? rv : rv2;
+}
+
+bool
+MainThreadStopSyncLoopRunnable::WorkerRun(JSContext* aCx,
+                                          WorkerPrivate* aWorkerPrivate)
+{
+  aWorkerPrivate->AssertIsOnWorkerThread();
+  MOZ_ASSERT(mSyncLoopTarget);
+
+  nsCOMPtr<nsIEventTarget> syncLoopTarget;
+  mSyncLoopTarget.swap(syncLoopTarget);
+
+  aWorkerPrivate->StopSyncLoop(syncLoopTarget, mResult);
+  return true;
+}
+
+bool
+MainThreadStopSyncLoopRunnable::DispatchInternal()
+{
+  MOZ_ASSERT(mSyncLoopTarget);
+
+  RefPtr<MainThreadStopSyncLoopRunnable> runnable(this);
+  return NS_SUCCEEDED(mSyncLoopTarget->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL));
+}
+
+void
+MainThreadStopSyncLoopRunnable::PostDispatch(WorkerPrivate* aWorkerPrivate,
+                                             bool aDispatchResult)
+{
+}
+
+#ifdef DEBUG
+WorkerControlRunnable::WorkerControlRunnable(WorkerPrivate* aWorkerPrivate,
+                                             TargetAndBusyBehavior aBehavior)
+: WorkerRunnable(aWorkerPrivate, aBehavior)
+{
+  MOZ_ASSERT(aWorkerPrivate);
+  MOZ_ASSERT(aBehavior == ParentThreadUnchangedBusyCount ||
+             aBehavior == WorkerThreadUnchangedBusyCount,
+             "WorkerControlRunnables should not modify the busy count");
+}
+#endif
+
+nsresult
+WorkerControlRunnable::Cancel()
+{
+  if (NS_FAILED(Run())) {
+    NS_WARNING("WorkerControlRunnable::Run() failed.");
+  }
+
+  return WorkerRunnable::Cancel();
+}
+
+bool
+WorkerControlRunnable::DispatchInternal()
+{
+  RefPtr<WorkerControlRunnable> runnable(this);
+
+  if (mBehavior == WorkerThreadUnchangedBusyCount) {
+    return NS_SUCCEEDED(mWorkerPrivate->DispatchControlRunnable(runnable.forget()));
+  }
+
+  if (WorkerPrivate* parent = mWorkerPrivate->GetParent()) {
+    return NS_SUCCEEDED(parent->DispatchControlRunnable(runnable.forget()));
+  }
+
+  return NS_SUCCEEDED(mWorkerPrivate->DispatchToMainThread(runnable.forget()));
+}
+
+NS_IMPL_ISUPPORTS_INHERITED0(WorkerControlRunnable, WorkerRunnable)
+
+WorkerMainThreadRunnable::WorkerMainThreadRunnable(WorkerPrivate* aWorkerPrivate,
+                                                   const nsACString& aTelemetryKey)
+: mWorkerPrivate(aWorkerPrivate)
+, mTelemetryKey(aTelemetryKey)
+{
+  mWorkerPrivate->AssertIsOnWorkerThread();
+}
+
+void
+WorkerMainThreadRunnable::Dispatch(ErrorResult& aRv)
+{
+  mWorkerPrivate->AssertIsOnWorkerThread();
+
+  TimeStamp startTime = TimeStamp::NowLoRes();
+
+  AutoSyncLoopHolder syncLoop(mWorkerPrivate);
+
+  mSyncLoopTarget = syncLoop.EventTarget();
+
+  DebugOnly<nsresult> rv = mWorkerPrivate->DispatchToMainThread(this);
+  MOZ_ASSERT(NS_SUCCEEDED(rv),
+             "Should only fail after xpcom-shutdown-threads and we're gone by then");
+
+  if (!syncLoop.Run()) {
+    aRv.ThrowUncatchableException();
+  }
+
+  Telemetry::Accumulate(Telemetry::SYNC_WORKER_OPERATION, mTelemetryKey,
+                        static_cast<uint32_t>((TimeStamp::NowLoRes() - startTime)
+                                                .ToMilliseconds()));
+  Unused << startTime; // Shut the compiler up.
+}
+
+NS_IMETHODIMP
+WorkerMainThreadRunnable::Run()
+{
+  AssertIsOnMainThread();
+
+  bool runResult = MainThreadRun();
+
+  RefPtr<MainThreadStopSyncLoopRunnable> response =
+    new MainThreadStopSyncLoopRunnable(mWorkerPrivate,
+                                       mSyncLoopTarget.forget(),
+                                       runResult);
+
+  MOZ_ALWAYS_TRUE(response->Dispatch());
+
+  return NS_OK;
+}
+
+WorkerCheckAPIExposureOnMainThreadRunnable::WorkerCheckAPIExposureOnMainThreadRunnable(WorkerPrivate* aWorkerPrivate):
+  WorkerMainThreadRunnable(aWorkerPrivate,
+                           NS_LITERAL_CSTRING("WorkerCheckAPIExposureOnMainThread"))
+{}
+
+WorkerCheckAPIExposureOnMainThreadRunnable::~WorkerCheckAPIExposureOnMainThreadRunnable()
+{}
+
+bool
+WorkerCheckAPIExposureOnMainThreadRunnable::Dispatch()
+{
+  ErrorResult rv;
+  WorkerMainThreadRunnable::Dispatch(rv);
+  bool ok = !rv.Failed();
+  rv.SuppressException();
+  return ok;
+}
+
+bool
+WorkerSameThreadRunnable::PreDispatch(WorkerPrivate* aWorkerPrivate)
+{
+  // We don't call WorkerRunnable::PreDispatch, because we're using
+  // WorkerThreadModifyBusyCount for mBehavior, and WorkerRunnable will assert
+  // that PreDispatch is on the parent thread in that case.
+  aWorkerPrivate->AssertIsOnWorkerThread();
+  return true;
+}
+
+void
+WorkerSameThreadRunnable::PostDispatch(WorkerPrivate* aWorkerPrivate,
+                                       bool aDispatchResult)
+{
+  // We don't call WorkerRunnable::PostDispatch, because we're using
+  // WorkerThreadModifyBusyCount for mBehavior, and WorkerRunnable will assert
+  // that PostDispatch is on the parent thread in that case.
+  aWorkerPrivate->AssertIsOnWorkerThread();
+  if (aDispatchResult) {
+    DebugOnly<bool> willIncrement = aWorkerPrivate->ModifyBusyCountFromWorker(true);
+    // Should never fail since if this thread is still running, so should the
+    // parent and it should be able to process a control runnable.
+    MOZ_ASSERT(willIncrement);
+  }
+}
+
+WorkerProxyToMainThreadRunnable::WorkerProxyToMainThreadRunnable(WorkerPrivate* aWorkerPrivate)
+  : mWorkerPrivate(aWorkerPrivate)
+{
+  MOZ_ASSERT(mWorkerPrivate);
+  mWorkerPrivate->AssertIsOnWorkerThread();
+}
+
+WorkerProxyToMainThreadRunnable::~WorkerProxyToMainThreadRunnable()
+{}
+
+bool
+WorkerProxyToMainThreadRunnable::Dispatch()
+{
+  mWorkerPrivate->AssertIsOnWorkerThread();
+
+  if (NS_WARN_IF(!HoldWorker())) {
+    RunBackOnWorkerThread();
+    return false;
+  }
+
+  if (NS_WARN_IF(NS_FAILED(mWorkerPrivate->DispatchToMainThread(this)))) {
+    ReleaseWorker();
+    RunBackOnWorkerThread();
+    return false;
+  }
+
+  return true;
+}
+
+NS_IMETHODIMP
+WorkerProxyToMainThreadRunnable::Run()
+{
+  AssertIsOnMainThread();
+  RunOnMainThread();
+  PostDispatchOnMainThread();
+  return NS_OK;
+}
+
+void
+WorkerProxyToMainThreadRunnable::PostDispatchOnMainThread()
+{
+  class ReleaseRunnable final : public MainThreadWorkerControlRunnable
+  {
+    RefPtr<WorkerProxyToMainThreadRunnable> mRunnable;
+
+  public:
+    ReleaseRunnable(WorkerPrivate* aWorkerPrivate,
+                    WorkerProxyToMainThreadRunnable* aRunnable)
+      : MainThreadWorkerControlRunnable(aWorkerPrivate)
+      , mRunnable(aRunnable)
+    {
+      MOZ_ASSERT(aRunnable);
+    }
+
+    // We must call RunBackOnWorkerThread() also if the runnable is canceled.
+    nsresult
+    Cancel() override
+    {
+      WorkerRun(nullptr, mWorkerPrivate);
+      return MainThreadWorkerControlRunnable::Cancel();
+    }
+
+    virtual bool
+    WorkerRun(JSContext* aCx, workers::WorkerPrivate* aWorkerPrivate) override
+    {
+      MOZ_ASSERT(aWorkerPrivate);
+      aWorkerPrivate->AssertIsOnWorkerThread();
+
+      if (mRunnable) {
+        mRunnable->RunBackOnWorkerThread();
+
+        // Let's release the worker thread.
+        mRunnable->ReleaseWorker();
+        mRunnable = nullptr;
+      }
+
+      return true;
+    }
+
+  private:
+    ~ReleaseRunnable()
+    {}
+  };
+
+  RefPtr<WorkerControlRunnable> runnable =
+    new ReleaseRunnable(mWorkerPrivate, this);
+  Unused << NS_WARN_IF(!runnable->Dispatch());
+}
+
+bool
+WorkerProxyToMainThreadRunnable::HoldWorker()
+{
+  mWorkerPrivate->AssertIsOnWorkerThread();
+  MOZ_ASSERT(!mWorkerHolder);
+
+  class SimpleWorkerHolder final : public WorkerHolder
+  {
+  public:
+    bool Notify(Status aStatus) override
+    {
+      // We don't care about the notification. We just want to keep the
+      // mWorkerPrivate alive.
+      return true;
+    }
+  };
+
+  UniquePtr<WorkerHolder> workerHolder(new SimpleWorkerHolder());
+  if (NS_WARN_IF(!workerHolder->HoldWorker(mWorkerPrivate, Canceling))) {
+    return false;
+  }
+
+  mWorkerHolder = Move(workerHolder);
+  return true;
+}
+
+void
+WorkerProxyToMainThreadRunnable::ReleaseWorker()
+{
+  mWorkerPrivate->AssertIsOnWorkerThread();
+  MOZ_ASSERT(mWorkerHolder);
+  mWorkerHolder = nullptr;
+}