[scheduler]: Avoid waking up the scheduler to end long idle periods.

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 694 matching lines @@
 
 void TaskQueueManager::SetWorkBatchSize(int work_batch_size) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   DCHECK_GE(work_batch_size, 1);
   work_batch_size_ = work_batch_size;
 }
 
 void TaskQueueManager::AddTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
-  base::MessageLoop::current()->AddTaskObserver(task_observer);
+  main_task_runner_->AddTaskObserver(task_observer);
   task_observers_.AddObserver(task_observer);
 }
 
 void TaskQueueManager::RemoveTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
-  base::MessageLoop::current()->RemoveTaskObserver(task_observer);
+  main_task_runner_->RemoveTaskObserver(task_observer);
   task_observers_.RemoveObserver(task_observer);
 }
 
 void TaskQueueManager::SetTimeSourceForTesting(
     scoped_ptr<TimeSource> time_source) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   time_source_ = time_source.Pass();
 }
 
 uint64 TaskQueueManager::GetAndClearTaskWasRunOnQueueBitmap() {
@@ skipping 53 matching lines @@
       return nullptr;
   }
 }
 
 void TaskQueueManager::OnTaskQueueEnabled() {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   MaybePostDoWorkOnMainRunner();
 }
 
 }  // namespace scheduler