Issue #2240 - Align Microtasks and promises scheduling with spec

Microtasks, resolved Promises and Observers are handled after the sync
task that caused them, in the order they were generated.
Also simplifies reentrancy handling.

Based-on: m-c 1193394

dom/animation/Animation.cpp

@@ -11,7 +11,6 @@
 #include "mozilla/AnimationTarget.h"
 #include "mozilla/AutoRestore.h"
 #include "mozilla/AsyncEventDispatcher.h" // For AsyncEventDispatcher
-#include "mozilla/CycleCollectedJSContext.h"
 #include "mozilla/Maybe.h" // For Maybe
 #include "nsAnimationManager.h" // For CSSAnimation
 #include "nsDOMMutationObserver.h" // For nsAutoAnimationMutationBatch
@@ -1384,6 +1383,30 @@ Animation::GetRenderedDocument() const
   return mEffect->AsKeyframeEffect()->GetRenderedDocument();
 }
 
+class AsyncFinishNotification : public MicroTaskRunnable
+{
+public:
+  explicit AsyncFinishNotification(Animation* aAnimation)
+  : MicroTaskRunnable()
+  , mAnimation(aAnimation)
+  {}
+
+  virtual void Run(AutoSlowOperation& aAso) override
+  {
+    mAnimation->DoFinishNotificationImmediately(this);
+    mAnimation = nullptr;
+  }
+
+  virtual bool Suppressed() override
+  {
+    nsIGlobalObject* global = mAnimation->GetOwnerGlobal();
+    return global && global->IsInSyncOperation();
+  }
+
+private:
+  RefPtr<Animation> mAnimation;
+};
+
 void
 Animation::DoFinishNotification(SyncNotifyFlag aSyncNotifyFlag)
 {
@@ -1391,9 +1414,8 @@ Animation::DoFinishNotification(SyncNotifyFlag aSyncNotifyFlag)
 
   if (aSyncNotifyFlag == SyncNotifyFlag::Sync) {
     DoFinishNotificationImmediately();
-  } else if (!mFinishNotificationTask.IsPending()) {
+  } else if (!mFinishNotificationTask) {
-    RefPtr<nsRunnableMethod<Animation>> runnable =
+    RefPtr<MicroTaskRunnable> runnable = new AsyncFinishNotification(this);
-      NewRunnableMethod(this, &Animation::DoFinishNotificationImmediately);
     context->DispatchToMicroTask(do_AddRef(runnable));
     mFinishNotificationTask = runnable.forget();
   }
@@ -1416,9 +1438,13 @@ Animation::MaybeResolveFinishedPromise()
 }
 
 void
-Animation::DoFinishNotificationImmediately()
+Animation::DoFinishNotificationImmediately(MicroTaskRunnable* aAsync)
 {
-  mFinishNotificationTask.Revoke();
+  if (aAsync && aAsync != mFinishNotificationTask) {
+    return;
+  }
+
+  mFinishNotificationTask = nullptr;
 
   if (PlayState() != AnimationPlayState::Finished) {
     return;

dom/animation/Animation.h

@@ -9,6 +9,7 @@
 #include "nsWrapperCache.h"
 #include "nsCycleCollectionParticipant.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/CycleCollectedJSContext.h"
 #include "mozilla/DOMEventTargetHelper.h"
 #include "mozilla/EffectCompositor.h" // For EffectCompositor::CascadeLevel
 #include "mozilla/LinkedList.h"
@@ -42,6 +43,7 @@ class AnimValuesStyleRule;
 
 namespace dom {
 
+class AsyncFinishNotification;
 class CSSAnimation;
 class CSSTransition;
 
@@ -378,7 +380,8 @@ protected:
   void ResetFinishedPromise();
   void MaybeResolveFinishedPromise();
   void DoFinishNotification(SyncNotifyFlag aSyncNotifyFlag);
-  void DoFinishNotificationImmediately();
+  friend class AsyncFinishNotification;
+  void DoFinishNotificationImmediately(MicroTaskRunnable* aAsync = nullptr);
   void DispatchPlaybackEvent(const nsAString& aName);
 
   /**
@@ -446,7 +449,7 @@ protected:
   // getAnimations() list.
   bool mIsRelevant;
 
-  nsRevocableEventPtr<nsRunnableMethod<Animation>> mFinishNotificationTask;
+  RefPtr<MicroTaskRunnable> mFinishNotificationTask;
   // True if mFinished is resolved or would be resolved if mFinished has
   // yet to be created. This is not set when mFinished is rejected since
   // in that case mFinished is immediately reset to represent a new current

dom/animation/DocumentTimeline.cpp

@@ -155,6 +155,13 @@ DocumentTimeline::WillRefresh(mozilla::TimeStamp aTime)
   bool needsTicks = false;
   nsTArray<Animation*> animationsToRemove(mAnimations.Count());
 
+  // https://drafts.csswg.org/web-animations-1/#update-animations-and-send-events,
+  // step2.
+  // Note that this should be done before nsAutoAnimationMutationBatch.  If
+  // PerformMicroTaskCheckpoint was called before nsAutoAnimationMutationBatch
+  // is destroyed, some mutation records might not be delivered in this
+  // checkpoint.
+  nsAutoMicroTask mt;
   nsAutoAnimationMutationBatch mb(mDocument);
 
   for (Animation* animation = mAnimationOrder.getFirst(); animation;

dom/base/CustomElementRegistry.cpp

@@ -1152,7 +1152,7 @@ CustomElementReactionsStack::Enqueue(Element* aElement,
 
   CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
   RefPtr<BackupQueueMicroTask> bqmt = new BackupQueueMicroTask(this);
-  context->DispatchMicroTaskRunnable(bqmt.forget());
+  context->DispatchToMicroTask(bqmt.forget());
 }
 
 void

dom/base/nsContentUtils.cpp

@@ -5418,10 +5418,10 @@ nsContentUtils::RunInStableState(already_AddRefed<nsIRunnable> aRunnable)
 
 /* static */
 void
-nsContentUtils::RunInMetastableState(already_AddRefed<nsIRunnable> aRunnable)
+nsContentUtils::AddPendingIDBTransaction(already_AddRefed<nsIRunnable> aTransaction)
 {
   MOZ_ASSERT(CycleCollectedJSContext::Get(), "Must be on a script thread!");
-  CycleCollectedJSContext::Get()->RunInMetastableState(Move(aRunnable));
+  CycleCollectedJSContext::Get()->AddPendingIDBTransaction(Move(aTransaction));
 }
 
 /*
@@ -6472,9 +6472,16 @@ nsContentUtils::IsSubDocumentTabbable(nsIContent* aContent)
   contentViewer->GetPreviousViewer(getter_AddRefs(zombieViewer));
 
   // If there are 2 viewers for the current docshell, that
-  // means the current document is a zombie document.
+  // means the current document may be a zombie document.
-  // Only navigate into the subdocument if it's not a zombie.
+  // While load and pageshow events are dispatched, zombie viewer is the old,
-  return !zombieViewer;
+  // to be hidden document.
+  if (zombieViewer) {
+    bool inOnLoad = false;
+    docShell->GetIsExecutingOnLoadHandler(&inOnLoad);
+    return inOnLoad;
+  }
+
+  return true;
 }
 
 bool

dom/base/nsContentUtils.h

@@ -1766,17 +1766,12 @@ public:
    */
   static void RunInStableState(already_AddRefed<nsIRunnable> aRunnable);
 
-  /* Add a "synchronous section", in the form of an nsIRunnable run once the
+  /* Add a pending IDBTransaction to be cleaned up at the end of performing a
-   * event loop has reached a "metastable state". |aRunnable| must not cause any
+   * microtask checkpoint.
-   * queued events to be processed (i.e. must not spin the event loop).
+   * See the step of "Cleanup Indexed Database Transactions" in
-   * We've reached a metastable state when the currently executing task or
+   * https://html.spec.whatwg.org/multipage/webappapis.html#perform-a-microtask-checkpoint
-   * microtask has finished.  This is not specced at this time.
-   * In practice this runs aRunnable once the currently executing task or
-   * microtask finishes.  If called multiple times per microtask, all the
-   * runnables will be executed, in the order in which RunInMetastableState()
-   * was called
    */
-  static void RunInMetastableState(already_AddRefed<nsIRunnable> aRunnable);
+  static void AddPendingIDBTransaction(already_AddRefed<nsIRunnable> aTransaction);
 
   /* Process viewport META data. This gives us information for the scale
    * and zoom of a page on mobile devices. We stick the information in

dom/base/nsDOMMutationObserver.cpp

@@ -623,7 +623,7 @@ nsDOMMutationObserver::QueueMutationObserverMicroTask()
 
   RefPtr<MutationObserverMicroTask> momt =
     new MutationObserverMicroTask();
-  ccjs->DispatchMicroTaskRunnable(momt.forget());
+  ccjs->DispatchToMicroTask(momt.forget());
 }
 
 void
@@ -644,9 +644,8 @@ nsDOMMutationObserver::RescheduleForRun()
       return;
     }
 
-    RefPtr<MutationObserverMicroTask> momt =
+    RefPtr<MutationObserverMicroTask> momt = new MutationObserverMicroTask();
-      new MutationObserverMicroTask();
+    ccjs->DispatchToMicroTask(momt.forget());
-    ccjs->DispatchMicroTaskRunnable(momt.forget());
     sScheduledMutationObservers = new AutoTArray<RefPtr<nsDOMMutationObserver>, 4>;
   }
 

dom/base/nsGlobalWindow.cpp

@@ -12999,12 +12999,6 @@ nsGlobalWindow::RunTimeoutHandler(Timeout* aTimeout,
   // point anyway, and the script context should have already reported
   // the script error in the usual way - so we just drop it.
 
-  // Since we might be processing more timeouts, go ahead and flush the promise
-  // queue now before we do that.  We need to do that while we're still in our
-  // "running JS is safe" state (e.g. mRunningTimeout is set, timeout->mRunning
-  // is false).
-  Promise::PerformMicroTaskCheckpoint();
-
   if (trackNestingLevel) {
     sNestingLevel = nestingLevel;
   }

dom/base/nsIGlobalObject.cpp

@@ -145,6 +145,6 @@ void nsIGlobalObject::QueueMicrotask(VoidFunction& aCallback) {
   CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
   if (context) {
     RefPtr<MicroTaskRunnable> mt = new QueuedMicrotask(this, aCallback);
-    context->DispatchMicroTaskRunnable(mt.forget());
+    context->DispatchToMicroTask(mt.forget());
   }
 }

dom/bindings/CallbackObject.cpp

@@ -78,11 +78,9 @@ CallbackObject::CallSetup::CallSetup(CallbackObject* aCallback,
   , mExceptionHandling(aExceptionHandling)
   , mIsMainThread(NS_IsMainThread())
 {
-  if (mIsMainThread) {
+  CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
-    CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
+  if (ccjs) {
-    if (ccjs) {
+    ccjs->EnterMicroTask();
-      ccjs->EnterMicroTask();
-    }
   }
 
   // Compute the caller's subject principal (if necessary) early, before we
@@ -290,11 +288,9 @@ CallbackObject::CallSetup::~CallSetup()
 
   // It is important that this is the last thing we do, after leaving the
   // compartment and undoing all our entry/incumbent script changes
-  if (mIsMainThread) {
+  CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
-    CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
+  if (ccjs) {
-    if (ccjs) {
+    ccjs->LeaveMicroTask();
-      ccjs->LeaveMicroTask();
-    }
   }
 }
 

dom/events/EventListenerManager.cpp

@@ -1064,12 +1064,8 @@ EventListenerManager::HandleEventSubType(Listener* aListener,
   }
 
   if (NS_SUCCEEDED(result)) {
-    if (mIsMainThreadELM) {
+    nsAutoMicroTask mt;
-      CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
+
-      if (ccjs) {
-        ccjs->EnterMicroTask();
-      }
-    }
     // nsIDOMEvent::currentTarget is set in EventDispatcher.
     if (listenerHolder.HasWebIDLCallback()) {
       ErrorResult rv;
@@ -1079,12 +1075,6 @@ EventListenerManager::HandleEventSubType(Listener* aListener,
     } else {
       result = listenerHolder.GetXPCOMCallback()->HandleEvent(aDOMEvent);
     }
-    if (mIsMainThreadELM) {
-      CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
-      if (ccjs) {
-        ccjs->LeaveMicroTask();
-      }
-    }
   }
 
   return result;

dom/indexedDB/ActorsChild.cpp

@@ -871,22 +871,26 @@ DispatchSuccessEvent(ResultHelper* aResultHelper,
                  IDB_LOG_STRINGIFY(aEvent, kSuccessEventType));
   }
 
+  MOZ_ASSERT_IF(transaction,
+                transaction->IsOpen() && !transaction->IsAborted());
+
   bool dummy;
   nsresult rv = request->DispatchEvent(aEvent, &dummy);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return;
   }
 
-  MOZ_ASSERT_IF(transaction,
-                transaction->IsOpen() || transaction->IsAborted());
-
   WidgetEvent* internalEvent = aEvent->WidgetEventPtr();
   MOZ_ASSERT(internalEvent);
 
   if (transaction &&
-      transaction->IsOpen() &&
+      transaction->IsOpen()) {
-      internalEvent->mFlags.mExceptionWasRaised) {
+    if (internalEvent->mFlags.mExceptionWasRaised) {
-    transaction->Abort(NS_ERROR_DOM_INDEXEDDB_ABORT_ERR);
+      transaction->Abort(NS_ERROR_DOM_INDEXEDDB_ABORT_ERR);
+    } else {
+      // To handle upgrade transaction.
+      transaction->Run();
+    }
   }
 }
 

dom/indexedDB/IDBFileHandle.cpp

@@ -55,7 +55,7 @@ IDBFileHandle::Create(IDBMutableFile* aMutableFile,
   MOZ_ASSERT(NS_IsMainThread(), "This won't work on non-main threads!");
 
   nsCOMPtr<nsIRunnable> runnable = do_QueryObject(fileHandle);
-  nsContentUtils::RunInMetastableState(runnable.forget());
+  nsContentUtils::AddPendingIDBTransaction(runnable.forget());
 
   fileHandle->SetCreating();
 

dom/indexedDB/IDBTransaction.cpp

@@ -190,13 +190,9 @@ IDBTransaction::CreateVersionChange(
 
   transaction->SetScriptOwner(aDatabase->GetScriptOwner());
 
-  nsCOMPtr<nsIRunnable> runnable = do_QueryObject(transaction);
-  nsContentUtils::RunInMetastableState(runnable.forget());
-
   transaction->mBackgroundActor.mVersionChangeBackgroundActor = aActor;
   transaction->mNextObjectStoreId = aNextObjectStoreId;
   transaction->mNextIndexId = aNextIndexId;
-  transaction->mCreating = true;
 
   aDatabase->RegisterTransaction(transaction);
   transaction->mRegistered = true;
@@ -226,7 +222,7 @@ IDBTransaction::Create(JSContext* aCx, IDBDatabase* aDatabase,
   transaction->SetScriptOwner(aDatabase->GetScriptOwner());
 
   nsCOMPtr<nsIRunnable> runnable = do_QueryObject(transaction);
-  nsContentUtils::RunInMetastableState(runnable.forget());
+  nsContentUtils::AddPendingIDBTransaction(runnable.forget());
 
   transaction->mCreating = true;
 

dom/promise/Promise.cpp

@@ -508,110 +508,6 @@ Promise::ReportRejectedPromise(JSContext* aCx, JS::HandleObject aPromise)
   NS_DispatchToMainThread(new AsyncErrorReporter(xpcReport));
 }
 
-bool
-Promise::PerformMicroTaskCheckpoint()
-{
-  MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
-
-  CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
-
-  // On the main thread, we always use the main promise micro task queue.
-  std::queue<nsCOMPtr<nsIRunnable>>& microtaskQueue =
-    context->GetPromiseMicroTaskQueue();
-
-  if (microtaskQueue.empty()) {
-    return false;
-  }
-
-  AutoSlowOperation aso;
-
-  do {
-    nsCOMPtr<nsIRunnable> runnable = microtaskQueue.front().forget();
-    MOZ_ASSERT(runnable);
-
-    // This function can re-enter, so we remove the element before calling.
-    microtaskQueue.pop();
-    nsresult rv = runnable->Run();
-    if (NS_WARN_IF(NS_FAILED(rv))) {
-      return false;
-    }
-    aso.CheckForInterrupt();
-    context->AfterProcessMicrotask();
-  } while (!microtaskQueue.empty());
-
-  return true;
-}
-
-void
-Promise::PerformWorkerMicroTaskCheckpoint()
-{
-  MOZ_ASSERT(!NS_IsMainThread(), "Wrong thread!");
-
-  CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
-  if (!context) {
-    return;
-  }
-
-  for (;;) {
-    // For a normal microtask checkpoint, we try to use the debugger microtask
-    // queue first. If the debugger queue is empty, we use the normal microtask
-    // queue instead.
-    std::queue<nsCOMPtr<nsIRunnable>>* microtaskQueue =
-      &context->GetDebuggerPromiseMicroTaskQueue();
-
-    if (microtaskQueue->empty()) {
-      microtaskQueue = &context->GetPromiseMicroTaskQueue();
-      if (microtaskQueue->empty()) {
-        break;
-      }
-    }
-
-    nsCOMPtr<nsIRunnable> runnable = microtaskQueue->front().forget();
-    MOZ_ASSERT(runnable);
-
-    // This function can re-enter, so we remove the element before calling.
-    microtaskQueue->pop();
-    nsresult rv = runnable->Run();
-    if (NS_WARN_IF(NS_FAILED(rv))) {
-      return;
-    }
-    context->AfterProcessMicrotask();
-  }
-}
-
-void
-Promise::PerformWorkerDebuggerMicroTaskCheckpoint()
-{
-  MOZ_ASSERT(!NS_IsMainThread(), "Wrong thread!");
-
-  CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
-  if (!context) {
-    return;
-  }
-
-  for (;;) {
-    // For a debugger microtask checkpoint, we always use the debugger microtask
-    // queue.
-    std::queue<nsCOMPtr<nsIRunnable>>* microtaskQueue =
-      &context->GetDebuggerPromiseMicroTaskQueue();
-
-    if (microtaskQueue->empty()) {
-      break;
-    }
-
-    nsCOMPtr<nsIRunnable> runnable = microtaskQueue->front().forget();
-    MOZ_ASSERT(runnable);
-
-    // This function can re-enter, so we remove the element before calling.
-    microtaskQueue->pop();
-    nsresult rv = runnable->Run();
-    if (NS_WARN_IF(NS_FAILED(rv))) {
-      return;
-    }
-    context->AfterProcessMicrotask();
-  }
-}
-
 JSObject*
 Promise::GlobalJSObject() const
 {

dom/promise/Promise.h

@@ -104,14 +104,6 @@ public:
                                            // specializations in the .cpp for
                                            // the T values we support.
 
-  // Called by DOM to let us execute our callbacks.  May be called recursively.
-  // Returns true if at least one microtask was processed.
-  static bool PerformMicroTaskCheckpoint();
-
-  static void PerformWorkerMicroTaskCheckpoint();
-
-  static void PerformWorkerDebuggerMicroTaskCheckpoint();
-
   // WebIDL
 
   nsIGlobalObject* GetParentObject() const

dom/script/ScriptSettings.cpp

@@ -828,8 +828,6 @@ AutoSafeJSContext::AutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMP
 AutoSlowOperation::AutoSlowOperation(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)
   : AutoJSAPI()
 {
-  MOZ_ASSERT(NS_IsMainThread());
-
   MOZ_GUARD_OBJECT_NOTIFIER_INIT;
 
   Init();
@@ -838,9 +836,12 @@ AutoSlowOperation::AutoSlowOperation(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMP
 void
 AutoSlowOperation::CheckForInterrupt()
 {
-  // JS_CheckForInterrupt expects us to be in a compartment.
+  // For now we support only main thread!
-  JSAutoCompartment ac(cx(), xpc::UnprivilegedJunkScope());
+  if (mIsMainThread) {
-  JS_CheckForInterrupt(cx());
+    // JS_CheckForInterrupt expects us to be in a compartment.
+    JSAutoCompartment ac(cx(), xpc::UnprivilegedJunkScope());
+    JS_CheckForInterrupt(cx());
+  }
 }
 
 } // namespace mozilla

dom/script/ScriptSettings.h

@@ -298,7 +298,6 @@ protected:
   // AutoJSAPI, so Init must NOT be called on subclasses that use this.
   AutoJSAPI(nsIGlobalObject* aGlobalObject, bool aIsMainThread, Type aType);
 
-private:
   mozilla::Maybe<JSAutoRequest> mAutoRequest;
   mozilla::Maybe<JSAutoNullableCompartment> mAutoNullableCompartment;
   JSContext *mCx;
@@ -307,6 +306,7 @@ private:
   bool mIsMainThread;
   Maybe<JS::WarningReporter> mOldWarningReporter;
 
+private:
   void InitInternal(nsIGlobalObject* aGlobalObject, JSObject* aGlobal,
                     JSContext* aCx, bool aIsMainThread);
 

dom/workers/RuntimeService.cpp

@@ -1007,6 +1007,10 @@ public:
     : mWorkerPrivate(aWorkerPrivate)
   {
     MOZ_ASSERT(aWorkerPrivate);
+    // Magical number 2. Workers have the base recursion depth 1, and normal
+    // runnables run at level 2, and we don't want to process microtasks
+    // at any other level.
+    SetTargetedMicroTaskRecursionDepth(2);
   }
 
   ~WorkerJSContext()
@@ -1092,26 +1096,14 @@ public:
     }
   }
 
-  virtual void AfterProcessTask(uint32_t aRecursionDepth) override
+  virtual void DispatchToMicroTask(already_AddRefed<MicroTaskRunnable> aRunnable) override
   {
-    // Only perform the Promise microtask checkpoint on the outermost event
+    RefPtr<MicroTaskRunnable> runnable(aRunnable);
-    // loop.  Don't run it, for example, during sync XHR or importScripts.
-    if (aRecursionDepth == 2) {
-      CycleCollectedJSContext::AfterProcessTask(aRecursionDepth);
-    } else if (aRecursionDepth > 2) {
-      AutoDisableMicroTaskCheckpoint disableMicroTaskCheckpoint;
-      CycleCollectedJSContext::AfterProcessTask(aRecursionDepth);
-    }
-  }
-
-  virtual void DispatchToMicroTask(already_AddRefed<nsIRunnable> aRunnable) override
-  {
-    RefPtr<nsIRunnable> runnable(aRunnable);
 
     MOZ_ASSERT(!NS_IsMainThread());
     MOZ_ASSERT(runnable);
 
-    std::queue<nsCOMPtr<nsIRunnable>>* microTaskQueue = nullptr;
+    std::queue<RefPtr<MicroTaskRunnable>>* microTaskQueue = nullptr;
 
     JSContext* cx = GetCurrentThreadJSContext();
     NS_ASSERTION(cx, "This should never be null!");
@@ -1120,15 +1112,15 @@ public:
     NS_ASSERTION(global, "This should never be null!");
 
     // On worker threads, if the current global is the worker global, we use the
-    // main promise micro task queue. Otherwise, the current global must be
+    // main micro task queue. Otherwise, the current global must be
     // either the debugger global or a debugger sandbox, and we use the debugger
-    // promise micro task queue instead.
+    // micro task queue instead.
     if (IsWorkerGlobal(global)) {
-      microTaskQueue = &mPromiseMicroTaskQueue;
+      microTaskQueue = &GetMicroTaskQueue();
     } else {
       MOZ_ASSERT(IsDebuggerGlobal(global) || IsDebuggerSandbox(global));
 
-      microTaskQueue = &mDebuggerPromiseMicroTaskQueue;
+      microTaskQueue = &GetDebuggerMicroTaskQueue();
     }
 
     microTaskQueue->push(runnable.forget());

dom/workers/WorkerPrivate.cpp

@@ -4816,8 +4816,10 @@ WorkerPrivate::DoRunLoop(JSContext* aCx)
       static_cast<nsIRunnable*>(runnable)->Run();
       runnable->Release();
 
-      // Flush the promise queue.
+      CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
-      Promise::PerformWorkerDebuggerMicroTaskCheckpoint();
+      if (ccjs) {
+        ccjs->PerformDebuggerMicroTaskCheckpoint();
+      }
 
       if (debuggerRunnablesPending) {
         WorkerDebuggerGlobalScope* globalScope = DebuggerGlobalScope();
@@ -5803,8 +5805,12 @@ WorkerPrivate::EnterDebuggerEventLoop()
     {
       MutexAutoLock lock(mMutex);
 
+      CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
+      std::queue<RefPtr<MicroTaskRunnable>>& debuggerMtQueue =
+        context->GetDebuggerMicroTaskQueue();
       while (mControlQueue.IsEmpty() &&
-             !(debuggerRunnablesPending = !mDebuggerQueue.IsEmpty())) {
+             !(debuggerRunnablesPending = !mDebuggerQueue.IsEmpty()) && 
+             debuggerMtQueue.empty()) {
         WaitForWorkerEvents();
       }
 
@@ -5813,6 +5819,11 @@ WorkerPrivate::EnterDebuggerEventLoop()
       // XXXkhuey should we abort JS on the stack here if we got Abort above?
     }
 
+    CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
+    if (context) {
+      context->PerformDebuggerMicroTaskCheckpoint();
+    }
+
     if (debuggerRunnablesPending) {
       // Start the periodic GC timer if it is not already running.
       SetGCTimerMode(PeriodicTimer);
@@ -5829,8 +5840,10 @@ WorkerPrivate::EnterDebuggerEventLoop()
       static_cast<nsIRunnable*>(runnable)->Run();
       runnable->Release();
 
-      // Flush the promise queue.
+      CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
-      Promise::PerformWorkerDebuggerMicroTaskCheckpoint();
+      if (ccjs) {
+        ccjs->PerformDebuggerMicroTaskCheckpoint();
+      }
 
       // Now *might* be a good time to GC. Let the JS engine make the decision.
       if (JS::CurrentGlobalOrNull(cx)) {
@@ -6257,8 +6270,8 @@ WorkerPrivate::RunExpiredTimeouts(JSContext* aCx)
 
     RefPtr<Function> callback = info->mHandler->GetCallback();
     if (!callback) {
-      // scope for the AutoEntryScript, so it comes off the stack before we do
+      nsAutoMicroTask mt;
-      // Promise::PerformMicroTaskCheckpoint.
+
       AutoEntryScript aes(global, reason, false);
 
       // Evaluate the timeout expression.
@@ -6293,10 +6306,6 @@ WorkerPrivate::RunExpiredTimeouts(JSContext* aCx)
       rv.SuppressException();
     }
 
-    // Since we might be processing more timeouts, go ahead and flush
-    // the promise queue now before we do that.
-    Promise::PerformWorkerMicroTaskCheckpoint();
-
     NS_ASSERTION(mRunningExpiredTimeouts, "Someone changed this!");
   }
 

js/xpconnect/src/XPCJSContext.cpp

@@ -3485,21 +3485,6 @@ XPCJSContext::BeforeProcessTask(bool aMightBlock)
 {
     MOZ_ASSERT(NS_IsMainThread());
 
-    // If ProcessNextEvent was called during a Promise "then" callback, we
-    // must process any pending microtasks before blocking in the event loop,
-    // otherwise we may deadlock until an event enters the queue later.
-    if (aMightBlock) {
-        if (Promise::PerformMicroTaskCheckpoint()) {
-            // If any microtask was processed, we post a dummy event in order to
-            // force the ProcessNextEvent call not to block.  This is required
-            // to support nested event loops implemented using a pattern like
-            // "while (condition) thread.processNextEvent(true)", in case the
-            // condition is triggered here by a Promise "then" callback.
-
-            NS_DispatchToMainThread(new Runnable());
-        }
-    }
-
     // Start the slow script timer.
     mSlowScriptCheckpoint = mozilla::TimeStamp::NowLoRes();
     mSlowScriptSecondHalf = false;

xpcom/base/CycleCollectedJSContext.cpp

@@ -437,7 +437,7 @@ CycleCollectedJSContext::CycleCollectedJSContext()
   , mPrevGCNurseryCollectionCallback(nullptr)
   , mJSHolders(256)
   , mDoingStableStates(false)
-  , mDisableMicroTaskCheckpoint(false)
+  , mTargetedMicroTaskRecursionDepth(0)
   , mMicroTaskLevel(0)
   , mMicroTaskRecursionDepth(0)
   , mOutOfMemoryState(OOMState::OK)
@@ -458,8 +458,8 @@ CycleCollectedJSContext::~CycleCollectedJSContext()
   MOZ_ASSERT(!mDeferredFinalizerTable.Count());
 
   // Last chance to process any events.
-  ProcessMetastableStateQueue(mBaseRecursionDepth);
+  CleanupIDBTransactions(mBaseRecursionDepth);
-  MOZ_ASSERT(mMetastableStateEvents.IsEmpty());
+  MOZ_ASSERT(mPendingIDBTransactions.IsEmpty());
 
   ProcessStableStateQueue();
   MOZ_ASSERT(mStableStateEvents.IsEmpty());
@@ -467,8 +467,8 @@ CycleCollectedJSContext::~CycleCollectedJSContext()
   // Clear mPendingException first, since it might be cycle collected.
   mPendingException = nullptr;
 
-  MOZ_ASSERT(mDebuggerPromiseMicroTaskQueue.empty());
+  MOZ_ASSERT(mDebuggerMicroTaskQueue.empty());
-  MOZ_ASSERT(mPromiseMicroTaskQueue.empty());
+  MOZ_ASSERT(mPendingMicroTaskRunnables.empty());
 
   mUncaughtRejections.reset();
   mConsumedRejections.reset();
@@ -921,7 +921,7 @@ CycleCollectedJSContext::LargeAllocationFailureCallback(void* aData)
   self->OnLargeAllocationFailure();
 }
 
-class PromiseJobRunnable final : public Runnable
+class PromiseJobRunnable final : public MicroTaskRunnable
 {
 public:
   PromiseJobRunnable(JS::HandleObject aCallback, JS::HandleObject aAllocationSite,
@@ -935,14 +935,20 @@ public:
   }
 
 protected:
-  NS_IMETHOD
+  virtual void Run(AutoSlowOperation& aAso) override
-  Run() override
   {
     nsIGlobalObject* global = xpc::NativeGlobal(mCallback->CallbackPreserveColor());
     if (global && !global->IsDying()) {
       mCallback->Call("promise callback");
+      aAso.CheckForInterrupt();
     }
-    return NS_OK;
+  }
+
+  virtual bool Suppressed() override
+  {
+    nsIGlobalObject* global =
+      xpc::NativeGlobal(mCallback->CallbackPreserveColor());
+    return global && global->IsInSyncOperation();
   }
 
 private:
@@ -976,7 +982,7 @@ CycleCollectedJSContext::EnqueuePromiseJobCallback(JSContext* aCx,
   if (aIncumbentGlobal) {
     global = xpc::NativeGlobal(aIncumbentGlobal);
   }
-  nsCOMPtr<nsIRunnable> runnable = new PromiseJobRunnable(aJob, aAllocationSite, global);
+  RefPtr<MicroTaskRunnable> runnable = new PromiseJobRunnable(aJob, aAllocationSite, global);
   self->DispatchToMicroTask(runnable.forget());
   return true;
 }
@@ -1175,18 +1181,18 @@ CycleCollectedJSContext::SetPendingException(nsIException* aException)
   mPendingException = aException;
 }
 
-std::queue<nsCOMPtr<nsIRunnable>>&
+std::queue<RefPtr<MicroTaskRunnable>>&
-CycleCollectedJSContext::GetPromiseMicroTaskQueue()
+CycleCollectedJSContext::GetMicroTaskQueue()
 {
   MOZ_ASSERT(mJSContext);
-  return mPromiseMicroTaskQueue;
+  return mPendingMicroTaskRunnables;
 }
 
-std::queue<nsCOMPtr<nsIRunnable>>&
+std::queue<RefPtr<MicroTaskRunnable>>&
-CycleCollectedJSContext::GetDebuggerPromiseMicroTaskQueue()
+CycleCollectedJSContext::GetDebuggerMicroTaskQueue()
 {
   MOZ_ASSERT(mJSContext);
-  return mDebuggerPromiseMicroTaskQueue;
+  return mDebuggerMicroTaskQueue;
 }
 
 nsCycleCollectionParticipant*
@@ -1345,24 +1351,24 @@ CycleCollectedJSContext::ProcessStableStateQueue()
 }
 
 void
-CycleCollectedJSContext::ProcessMetastableStateQueue(uint32_t aRecursionDepth)
+CycleCollectedJSContext::CleanupIDBTransactions(uint32_t aRecursionDepth)
 {
   MOZ_ASSERT(mJSContext);
   MOZ_RELEASE_ASSERT(!mDoingStableStates);
   mDoingStableStates = true;
 
-  nsTArray<RunInMetastableStateData> localQueue = Move(mMetastableStateEvents);
+  nsTArray<PendingIDBTransactionData> localQueue = Move(mPendingIDBTransactions);
 
   for (uint32_t i = 0; i < localQueue.Length(); ++i)
   {
-    RunInMetastableStateData& data = localQueue[i];
+    PendingIDBTransactionData& data = localQueue[i];
     if (data.mRecursionDepth != aRecursionDepth) {
       continue;
     }
 
     {
-      nsCOMPtr<nsIRunnable> runnable = data.mRunnable.forget();
+      nsCOMPtr<nsIRunnable> transaction = data.mTransaction.forget();
-      runnable->Run();
+      transaction->Run();
     }
 
     localQueue.RemoveElementAt(i--);
@@ -1370,11 +1376,27 @@ CycleCollectedJSContext::ProcessMetastableStateQueue(uint32_t aRecursionDepth)
 
   // If the queue has events in it now, they were added from something we called,
   // so they belong at the end of the queue.
-  localQueue.AppendElements(mMetastableStateEvents);
+  localQueue.AppendElements(mPendingIDBTransactions);
-  localQueue.SwapElements(mMetastableStateEvents);
+  localQueue.SwapElements(mPendingIDBTransactions);
   mDoingStableStates = false;
 }
 
+void
+CycleCollectedJSContext::BeforeProcessTask(bool aMightBlock)
+{
+  // If ProcessNextEvent was called during a microtask callback, we
+  // must process any pending microtasks before blocking in the event loop,
+  // otherwise we may deadlock until an event enters the queue later.
+  if (aMightBlock && PerformMicroTaskCheckPoint()) {
+    // If any microtask was processed, we post a dummy event in order to
+    // force the ProcessNextEvent call not to block.  This is required
+    // to support nested event loops implemented using a pattern like
+    // "while (condition) thread.processNextEvent(true)", in case the
+    // condition is triggered here by a Promise "then" callback.
+    NS_DispatchToMainThread(new Runnable());
+  }
+}
+
 void
 CycleCollectedJSContext::AfterProcessTask(uint32_t aRecursionDepth)
 {
@@ -1382,39 +1404,20 @@ CycleCollectedJSContext::AfterProcessTask(uint32_t aRecursionDepth)
 
   // See HTML 6.1.4.2 Processing model
 
-  // Execute any events that were waiting for a microtask to complete.
-  // This is not (yet) in the spec.
-  ProcessMetastableStateQueue(aRecursionDepth);
-
   // Step 4.1: Execute microtasks.
-  if (!mDisableMicroTaskCheckpoint) {
+  PerformMicroTaskCheckPoint();
-    PerformMicroTaskCheckPoint();
-    if (NS_IsMainThread()) {
-      Promise::PerformMicroTaskCheckpoint();
-    } else {
-      Promise::PerformWorkerMicroTaskCheckpoint();
-    }
-  }
 
   // Step 4.2 Execute any events that were waiting for a stable state.
   ProcessStableStateQueue();
 }
 
 void
-CycleCollectedJSContext::AfterProcessMicrotask()
+CycleCollectedJSContext::AfterProcessMicrotasks()
 {
   MOZ_ASSERT(mJSContext);
-  AfterProcessMicrotask(RecursionDepth());
+  // Cleanup Indexed Database transactions:
-}
+  // https://html.spec.whatwg.org/multipage/webappapis.html#perform-a-microtask-checkpoint
-
+  CleanupIDBTransactions(RecursionDepth());
-void
-CycleCollectedJSContext::AfterProcessMicrotask(uint32_t aRecursionDepth)
-{
-  MOZ_ASSERT(mJSContext);
-
-  // Between microtasks, execute any events that were waiting for a microtask
-  // to complete.
-  ProcessMetastableStateQueue(aRecursionDepth);
 }
 
 uint32_t
@@ -1431,12 +1434,12 @@ CycleCollectedJSContext::RunInStableState(already_AddRefed<nsIRunnable>&& aRunna
 }
 
 void
-CycleCollectedJSContext::RunInMetastableState(already_AddRefed<nsIRunnable>&& aRunnable)
+CycleCollectedJSContext::AddPendingIDBTransaction(already_AddRefed<nsIRunnable>&& aTransaction)
 {
   MOZ_ASSERT(mJSContext);
 
-  RunInMetastableStateData data;
+  PendingIDBTransactionData data;
-  data.mRunnable = aRunnable;
+  data.mTransaction = aTransaction;
 
   MOZ_ASSERT(mOwningThread);
   data.mRecursionDepth = RecursionDepth();
@@ -1453,7 +1456,7 @@ CycleCollectedJSContext::RunInMetastableState(already_AddRefed<nsIRunnable>&& aR
   }
 #endif
 
-  mMetastableStateEvents.AppendElement(Move(data));
+  mPendingIDBTransactions.AppendElement(Move(data));
 }
 
 IncrementalFinalizeRunnable::IncrementalFinalizeRunnable(CycleCollectedJSContext* aCx,
@@ -1659,14 +1662,14 @@ CycleCollectedJSContext::PrepareWaitingZonesForGC()
 }
 
 void
-CycleCollectedJSContext::DispatchToMicroTask(already_AddRefed<nsIRunnable> aRunnable)
+CycleCollectedJSContext::DispatchToMicroTask(already_AddRefed<MicroTaskRunnable> aRunnable)
 {
-  RefPtr<nsIRunnable> runnable(aRunnable);
+  RefPtr<MicroTaskRunnable> runnable(aRunnable);
 
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(runnable);
 
-  mPromiseMicroTaskQueue.push(runnable.forget());
+  mPendingMicroTaskRunnables.push(runnable.forget());
 }
 
 class AsyncMutationHandler final : public mozilla::Runnable
@@ -1682,41 +1685,61 @@ public:
   }
 };
 
-void
+bool
 CycleCollectedJSContext::PerformMicroTaskCheckPoint()
 {
-  if (mPendingMicroTaskRunnables.empty()) {
+  if (mPendingMicroTaskRunnables.empty() && mDebuggerMicroTaskQueue.empty()) {
+    AfterProcessMicrotasks();
     // Nothing to do, return early.
-    return;
+    return false;
   }
 
   uint32_t currentDepth = RecursionDepth();
   if (mMicroTaskRecursionDepth >= currentDepth) {
     // We are already executing microtasks for the current recursion depth.
-    return;
+    return false;
+  }
+
+  if (mTargetedMicroTaskRecursionDepth != 0 &&
+      mTargetedMicroTaskRecursionDepth != currentDepth) {
+    return false;
   }
 
   if (NS_IsMainThread() && !nsContentUtils::IsSafeToRunScript()) {
     // Special case for main thread where DOM mutations may happen when
     // it is not safe to run scripts.
     nsContentUtils::AddScriptRunner(new AsyncMutationHandler());
-    return;
+    return false;
   }
 
   mozilla::AutoRestore<uint32_t> restore(mMicroTaskRecursionDepth);
   MOZ_ASSERT(currentDepth > 0);
   mMicroTaskRecursionDepth = currentDepth;
 
+  bool didProcess = false;
   AutoSlowOperation aso;
 
   std::queue<RefPtr<MicroTaskRunnable>> suppressed;
-  while (!mPendingMicroTaskRunnables.empty()) {
+  for (;;) {
-    RefPtr<MicroTaskRunnable> runnable =
+    RefPtr<MicroTaskRunnable> runnable;
-      mPendingMicroTaskRunnables.front().forget();
+    if (!mDebuggerMicroTaskQueue.empty()) {
-    mPendingMicroTaskRunnables.pop();
+      runnable = mDebuggerMicroTaskQueue.front().forget();
+      mDebuggerMicroTaskQueue.pop();
+    } else if (!mPendingMicroTaskRunnables.empty()) {
+      runnable = mPendingMicroTaskRunnables.front().forget();
+      mPendingMicroTaskRunnables.pop();
+    } else {
+      break;
+    }
+
     if (runnable->Suppressed()) {
+      // Microtasks in worker shall never be suppressed.
+      // Otherwise, mPendingMicroTaskRunnables will be replaced later with
+      // all suppressed tasks in mDebuggerMicroTaskQueue unexpectedly.
+      MOZ_ASSERT(NS_IsMainThread());
       suppressed.push(runnable);
     } else {
+      didProcess = true;
       runnable->Run(aso);
     }
   }
@@ -1726,13 +1749,38 @@ CycleCollectedJSContext::PerformMicroTaskCheckPoint()
   // for some time, but no longer than spinning the event loop nestedly
   // (sync XHR, alert, etc.)
   mPendingMicroTaskRunnables.swap(suppressed);
+
+  AfterProcessMicrotasks();
+
+  return didProcess;
 }
 
 void
-CycleCollectedJSContext::DispatchMicroTaskRunnable(
+CycleCollectedJSContext::PerformDebuggerMicroTaskCheckpoint()
-  already_AddRefed<MicroTaskRunnable> aRunnable)
+ {
-{
+  // Don't do normal microtask handling checks here, since whoever is calling
-  mPendingMicroTaskRunnables.push(aRunnable);
+  // this method is supposed to know what they are doing.
+
+  AutoSlowOperation aso;
+  for (;;) {
+    // For a debugger microtask checkpoint, we always use the debugger microtask
+    // queue.
+    std::queue<RefPtr<MicroTaskRunnable>>* microtaskQueue =
+      &GetDebuggerMicroTaskQueue();
+
+    if (microtaskQueue->empty()) {
+      break;
+    }
+
+    RefPtr<MicroTaskRunnable> runnable = microtaskQueue->front().forget();
+    MOZ_ASSERT(runnable);
+
+    // This function can re-enter, so we remove the element before calling.
+    microtaskQueue->pop();
+    runnable->Run(aso);
+  }
+
+  AfterProcessMicrotasks();
 }
 
 void

xpcom/base/CycleCollectedJSContext.h

@@ -170,9 +170,6 @@ protected:
   virtual void CustomOutOfMemoryCallback() {}
   virtual void CustomLargeAllocationFailureCallback() {}
 
-  std::queue<nsCOMPtr<nsIRunnable>> mPromiseMicroTaskQueue;
-  std::queue<nsCOMPtr<nsIRunnable>> mDebuggerPromiseMicroTaskQueue;
-
 private:
   void
   DescribeGCThing(bool aIsMarked, JS::GCCellPtr aThing,
@@ -243,11 +240,11 @@ private:
   virtual void TraceNativeBlackRoots(JSTracer* aTracer) { };
   void TraceNativeGrayRoots(JSTracer* aTracer);
 
-  void AfterProcessMicrotask(uint32_t aRecursionDepth);
+  void AfterProcessMicrotasks();
 public:
   void ProcessStableStateQueue();
 private:
-  void ProcessMetastableStateQueue(uint32_t aRecursionDepth);
+  void CleanupIDBTransactions(uint32_t aRecursionDepth);
 
 public:
   enum DeferredFinalizeType {
@@ -306,8 +303,8 @@ public:
   already_AddRefed<nsIException> GetPendingException() const;
   void SetPendingException(nsIException* aException);
 
-  std::queue<nsCOMPtr<nsIRunnable>>& GetPromiseMicroTaskQueue();
+  std::queue<RefPtr<MicroTaskRunnable>>& GetMicroTaskQueue();
-  std::queue<nsCOMPtr<nsIRunnable>>& GetDebuggerPromiseMicroTaskQueue();
+  std::queue<RefPtr<MicroTaskRunnable>>& GetDebuggerMicroTaskQueue();
 
   nsCycleCollectionParticipant* GCThingParticipant();
   nsCycleCollectionParticipant* ZoneParticipant();
@@ -346,53 +343,25 @@ public:
     return JS::RootingContext::get(mJSContext);
   }
 
-  bool MicroTaskCheckpointDisabled() const
+  void SetTargetedMicroTaskRecursionDepth(uint32_t aDepth)
   {
-    return mDisableMicroTaskCheckpoint;
+    mTargetedMicroTaskRecursionDepth = aDepth;
   }
 
-  void DisableMicroTaskCheckpoint(bool aDisable)
-  {
-    mDisableMicroTaskCheckpoint = aDisable;
-  }
-
-  class MOZ_RAII AutoDisableMicroTaskCheckpoint
-  {
-    public:
-    AutoDisableMicroTaskCheckpoint()
-    : mCCJSCX(CycleCollectedJSContext::Get())
-    {
-      mOldValue = mCCJSCX->MicroTaskCheckpointDisabled();
-      mCCJSCX->DisableMicroTaskCheckpoint(true);
-    }
-
-    ~AutoDisableMicroTaskCheckpoint()
-    {
-      mCCJSCX->DisableMicroTaskCheckpoint(mOldValue);
-    }
-
-    CycleCollectedJSContext* mCCJSCX;
-    bool mOldValue;
-  };
-
 protected:
   JSContext* MaybeContext() const { return mJSContext; }
 
 public:
   // nsThread entrypoints
-  virtual void BeforeProcessTask(bool aMightBlock) { };
+  virtual void BeforeProcessTask(bool aMightBlock);
   virtual void AfterProcessTask(uint32_t aRecursionDepth);
 
-  // microtask processor entry point
-  void AfterProcessMicrotask();
-
   uint32_t RecursionDepth();
 
   // Run in stable state (call through nsContentUtils)
   void RunInStableState(already_AddRefed<nsIRunnable>&& aRunnable);
-  // This isn't in the spec at all yet, but this gets the behavior we want for IDB.
+
-  // Runs after the current microtask completes.
+  void AddPendingIDBTransaction(already_AddRefed<nsIRunnable>&& aTransaction);
-  void RunInMetastableState(already_AddRefed<nsIRunnable>&& aRunnable);
 
   // Get the current thread's CycleCollectedJSContext.  Returns null if there
   // isn't one.
@@ -411,7 +380,7 @@ public:
   void PrepareWaitingZonesForGC();
 
   // Queue an async microtask to the current main or worker thread.
-  virtual void DispatchToMicroTask(already_AddRefed<nsIRunnable> aRunnable);
+  virtual void DispatchToMicroTask(already_AddRefed<MicroTaskRunnable> aRunnable);
 
   // Call EnterMicroTask when you're entering JS execution.
   // Usually the best way to do this is to use nsAutoMicroTask.
@@ -442,9 +411,9 @@ public:
     mMicroTaskLevel = aLevel;
   }
 
-  void PerformMicroTaskCheckPoint();
+  bool PerformMicroTaskCheckPoint();
 
-  void DispatchMicroTaskRunnable(already_AddRefed<MicroTaskRunnable> aRunnable);
+  void PerformDebuggerMicroTaskCheckpoint();
 
   // Storage for watching rejected promises waiting for some client to
   // consume their rejection.
@@ -483,21 +452,25 @@ private:
   nsCOMPtr<nsIException> mPendingException;
   nsThread* mOwningThread; // Manual refcounting to avoid include hell.
 
-  struct RunInMetastableStateData
+  struct PendingIDBTransactionData
   {
-    nsCOMPtr<nsIRunnable> mRunnable;
+    nsCOMPtr<nsIRunnable> mTransaction;
     uint32_t mRecursionDepth;
   };
 
   nsTArray<nsCOMPtr<nsIRunnable>> mStableStateEvents;
-  nsTArray<RunInMetastableStateData> mMetastableStateEvents;
+  nsTArray<PendingIDBTransactionData> mPendingIDBTransactions;
   uint32_t mBaseRecursionDepth;
   bool mDoingStableStates;
 
-  bool mDisableMicroTaskCheckpoint;
+  // If set to none 0, microtasks will be processed only when recursion depth
+  // is the set value.
+  uint32_t mTargetedMicroTaskRecursionDepth;
 
   uint32_t mMicroTaskLevel;
+
   std::queue<RefPtr<MicroTaskRunnable>> mPendingMicroTaskRunnables;
+  std::queue<RefPtr<MicroTaskRunnable>> mDebuggerMicroTaskQueue;
 
   uint32_t mMicroTaskRecursionDepth;