Reland of Fix getUserMedia so that failure is reported for invalid audio sources.

chrome/renderer/media/cast_receiver_audio_valve.h

Index: chrome/renderer/media/cast_receiver_audio_valve.h
diff --git a/chrome/renderer/media/cast_receiver_audio_valve.h b/chrome/renderer/media/cast_receiver_audio_valve.h
index f6c09a74a26c125268962b6c5d90a31df508e5e7..1bf020306733a71652e4e57542876d9740b51356 100644
--- a/chrome/renderer/media/cast_receiver_audio_valve.h
+++ b/chrome/renderer/media/cast_receiver_audio_valve.h
@@ -31,6 +31,10 @@ class CastReceiverAudioValve :
   void DeliverDecodedAudio(const media::AudioBus* audio_bus,
                            base::TimeTicks playout_time);
 
+  // Called to indicate that audio has started streaming and our capture
+  // callback should be notified.
+  void OnStarted();
+
   // When this returns, no more calls will be forwarded to |cb|.
   void Stop();