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

components/scheduler/child/scheduler_message_loop_delegate.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_SCHEDULER_CHILD_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_
 #define COMPONENTS_SCHEDULER_CHILD_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_
 
 #include "base/message_loop/message_loop.h"
 #include "components/scheduler/child/nestable_single_thread_task_runner.h"
 #include "components/scheduler/scheduler_export.h"
 
 namespace scheduler {
 
 class SCHEDULER_EXPORT SchedulerMessageLoopDelegate
     : public NestableSingleThreadTaskRunner {
  public:
   // |message_loop| is not owned and must outlive the lifetime of this object.
   static scoped_refptr<SchedulerMessageLoopDelegate> Create(
       base::MessageLoop* message_loop);
 
   // NestableSingleThreadTaskRunner implementation
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const base::Closure& task,
                        base::TimeDelta delay) override;
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
                                   const base::Closure& task,
                                   base::TimeDelta delay) override;
   bool RunsTasksOnCurrentThread() const override;
   bool IsNested() const override;
+  void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer) override;
+  void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) override;
 
  protected:
   ~SchedulerMessageLoopDelegate() override;
 
  private:
   SchedulerMessageLoopDelegate(base::MessageLoop* message_loop);
 
   // Not owned.
   base::MessageLoop* message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerMessageLoopDelegate);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_CHILD_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_