Implement PostDelayedTaskAt for guaranteed timer ordering

components/scheduler/renderer/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 COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 #define COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 
 #include "base/message_loop/message_loop.h"
 #include "components/scheduler/child/child_scheduler.h"
 #include "components/scheduler/child/single_thread_idle_task_runner.h"
@@ skipping 13 matching lines @@
 
   // Returns the compositor task runner.
   virtual scoped_refptr<base::SingleThreadTaskRunner>
   CompositorTaskRunner() = 0;
 
   // Returns the loading task runner.  This queue is intended for tasks related
   // to resource dispatch, foreground HTML parsing, etc...
   virtual scoped_refptr<base::SingleThreadTaskRunner> LoadingTaskRunner() = 0;
 
   // Returns the timer task runner.  This queue is intended for DOM Timers.
-  virtual scoped_refptr<base::SingleThreadTaskRunner> TimerTaskRunner() = 0;
+  virtual scoped_refptr<TaskQueue> TimerTaskRunner() = 0;
 
   // Called to notify about the start of an extended period where no frames
   // need to be drawn. Must be called from the main thread.
   virtual void BeginFrameNotExpectedSoon() = 0;
 
   // Called to notify about the start of a new frame.  Must be called from the
   // main thread.
   virtual void WillBeginFrame(const cc::BeginFrameArgs& args) = 0;
 
   // Called to notify that a previously begun frame was committed. Must be
@@ skipping 54 matching lines @@
   virtual void ResumeTimerQueue() = 0;
 
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_