Introduce TimeSource notifications to the VideoRenderer.

media/base/video_renderer.h

 // Copyright (c) 2012 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 MEDIA_BASE_VIDEO_RENDERER_H_
 #define MEDIA_BASE_VIDEO_RENDERER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
@@ skipping 64 matching lines @@
   // Clients should expect |buffering_state_cb| to be called with
   // BUFFERING_HAVE_NOTHING while flushing is in progress.
   virtual void Flush(const base::Closure& callback) = 0;
 
   // Starts playback at |timestamp| by reading from |stream| and decoding and
   // rendering video.
   //
   // Only valid to call after a successful Initialize() or Flush().
   virtual void StartPlayingFrom(base::TimeDelta timestamp) = 0;
 
+  // Called when time starts or stops moving. Time progresses when a base time
+  // has been set and the playback rate is > 0. If either condition changes,
+  // |time_progressing| will be false.

[xhwang, 2015/04/07 23:57:49]

Add a comment about why we need this method in the first place. For example, we
need to notify the compositor so that it can stopping polling for new frames. If
you don't like to have impl details on the interface, maybe add it to VRI?

[DaleCurtis, 2015/04/08 00:04:32]

I'll add it to the VRI once we have such details. I don't think it makes sense
to add them here.

+  virtual void OnTimeStateChanged(bool time_progressing) = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoRenderer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_RENDERER_H_