scheduler: Implement task observers

content/renderer/scheduler/renderer_scheduler.h

 // 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.
 
 #ifndef CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_
 #define CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_
 
 #include "content/renderer/scheduler/single_thread_idle_task_runner.h"
 #include "content/renderer/scheduler/task_queue_manager.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
@@ skipping 52 matching lines @@
   // Must be called from the main thread.
   virtual bool IsHighPriorityWorkAnticipated() = 0;
 
   // Returns true if there is high priority work pending on the main thread
   // and the caller should yield to let the scheduler service that work. Note
   // that this is a stricter condition than |IsHighPriorityWorkAnticipated|,
   // restricted to the case where real work is pending.
   // Must be called from the main thread.
   virtual bool ShouldYieldForHighPriorityWork() = 0;
 
+  // Adds or removes a task observer from the scheduler. The observer will be
+  // notified before and after every executed task. These functions can only be
+  // called on the main thread.
+  virtual void AddTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+  virtual void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+
   // Shuts down the scheduler by dropping any remaining pending work in the work
   // queues. After this call any work posted to the task runners will be
   // silently dropped.
   virtual void Shutdown() = 0;
 
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_