[scheduler]: Fix tracing issues with nested IdlePeriod trace events.

components/scheduler/child/task_queue_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/scheduler/child/task_queue_manager.h"
 
 #include <queue>
 #include <set>
 
 #include "base/bind.h"
@@ skipping 263 matching lines @@
   scoped_refptr<DeletionSentinel> protect(deletion_sentinel_);
   // TODO(alexclarke): consider std::move() when allowed.
   internal::TaskQueueImpl::Task pending_task = queue->TakeTaskFromWorkQueue();
 
   if (queue->GetQuiescenceMonitored())
     task_was_run_on_quiescence_monitored_queue_ = true;
 
   if (!pending_task.nestable && main_task_runner_->IsNested()) {
     // Defer non-nestable work to the main task runner.  NOTE these tasks can be
     // arbitrarily delayed so the additional delay should not be a problem.
+    // TODO(skyostil): Figure out a way to not forget which task queue the
+    // task is associated with. See http://crbug.com/522843.
     main_task_runner_->PostNonNestableTask(pending_task.posted_from,
                                            pending_task.task);
   } else {
     TRACE_TASK_EXECUTION("TaskQueueManager::ProcessTaskFromWorkQueue",
                          pending_task);
     if (queue->GetShouldNotifyObservers()) {
       FOR_EACH_OBSERVER(base::MessageLoop::TaskObserver, task_observers_,
                         WillProcessTask(pending_task));
     }
     task_annotator_.RunTask("TaskQueueManager::PostTask", pending_task);
@@ skipping 89 matching lines @@
 }
 
 void TaskQueueManager::OnTaskQueueEnabled(internal::TaskQueueImpl* queue) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   // Only schedule DoWork if there's something to do.
   if (!queue->work_queue().empty())
     MaybePostDoWorkOnMainRunner();
 }
 
 }  // namespace scheduler