Introduce TimeSource notifications to the VideoRenderer.

media/base/video_renderer.h

Index: media/base/video_renderer.h
diff --git a/media/base/video_renderer.h b/media/base/video_renderer.h
index 360e632517fbf79621781f4d96f330bc0801d505..46e842eb8d0211341976d38c4a009a4e1ecf9fe8 100644
--- a/media/base/video_renderer.h
+++ b/media/base/video_renderer.h
@@ -82,6 +82,11 @@ class MEDIA_EXPORT VideoRenderer {
   // 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);
 };