SequenceManager: Cross thread delayed task calls WillQueueTask once

Bug: 826902
Change-Id: Ic79292edea1d7d92935797103ded169cb114e1cf
Reviewed-on: https://chromium-review.googlesource.com/1254542
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595848}

base/debug/task_annotator.cc

@@ -44,10 +44,8 @@ void TaskAnnotator::WillQueueTask(const char* queue_function,
                            TRACE_EVENT_FLAG_FLOW_OUT);
   }
 
-  // TODO(https://crbug.com/826902): Fix callers that invoke WillQueueTask()
-  // twice for the same PendingTask.
-  // DCHECK(!pending_task.task_backtrace[0])
-  //     << "Task backtrace was already set, task posted twice??";
+  DCHECK(!pending_task->task_backtrace[0])
+      << "Task backtrace was already set, task posted twice??";
   if (!pending_task->task_backtrace[0]) {
     const PendingTask* parent_task = GetTLSForCurrentPendingTask()->Get();
     if (parent_task) {

base/task/sequence_manager/task_queue_impl.cc

@@ -204,7 +204,7 @@ void TaskQueueImpl::PostDelayedTaskImpl(PostedTask task) {
     TimeTicks time_domain_delayed_run_time = time_domain_now + task.delay;
     PushOntoDelayedIncomingQueueFromMainThread(
         Task(std::move(task), time_domain_delayed_run_time, sequence_number),
-        time_domain_now);
+        time_domain_now, /* notify_task_annotator */ true);
   } else {
     // NOTE posting a delayed task from a different thread is not expected to
     // be common. This pathway is less optimal than perhaps it could be
@@ -225,8 +225,10 @@ void TaskQueueImpl::PostDelayedTaskImpl(PostedTask task) {
 
 void TaskQueueImpl::PushOntoDelayedIncomingQueueFromMainThread(
     Task pending_task,
-    TimeTicks now) {
-  main_thread_only().sequence_manager->WillQueueTask(&pending_task);
+    TimeTicks now,
+    bool notify_task_annotator) {
+  if (notify_task_annotator)
+    main_thread_only().sequence_manager->WillQueueTask(&pending_task);
   main_thread_only().delayed_incoming_queue.push(std::move(pending_task));
 
   LazyNow lazy_now(now);
@@ -266,7 +268,7 @@ void TaskQueueImpl::ScheduleDelayedWorkTask(Task pending_task) {
   } else {
     // If |delayed_run_time| is in the future we can queue it as normal.
     PushOntoDelayedIncomingQueueFromMainThread(std::move(pending_task),
-                                               time_domain_now);
+                                               time_domain_now, false);
   }
   TraceQueueSize();
 }

base/task/sequence_manager/task_queue_impl.h

@@ -296,7 +296,8 @@ class BASE_EXPORT TaskQueueImpl {
   // Push the task onto the |delayed_incoming_queue|. Lock-free main thread
   // only fast path.
   void PushOntoDelayedIncomingQueueFromMainThread(Task pending_task,
-                                                  TimeTicks now);
+                                                  TimeTicks now,
+                                                  bool notify_task_annotator);
 
   // Push the task onto the |delayed_incoming_queue|.  Slow path from other
   // threads.