Implement disabling and enabling media tracks

media/mojo/interfaces/renderer.mojom

Index: media/mojo/interfaces/renderer.mojom
diff --git a/media/mojo/interfaces/renderer.mojom b/media/mojo/interfaces/renderer.mojom
index e3135c8c56b9c91e10ed3ec0df53b76bd16a7cc7..bdcf06df5984ce75e752b8894cb7ec4a6d1b9249 100644
--- a/media/mojo/interfaces/renderer.mojom
+++ b/media/mojo/interfaces/renderer.mojom
@@ -23,6 +23,9 @@ interface Renderer {
   // Starts rendering from |time_usec|.
   StartPlayingFrom(int64 time_usec);
 
+  // Restarts rendering a given stream after it has been reenabled.
+  RestartStreamPlayback(bool video_stream, int64 time_usec);
+
   // Updates the current playback rate. The default playback rate should be 1.
   SetPlaybackRate(double playback_rate);