Propagate muted state from MediaStreamAudioSource into JS.

media/audio/fake_audio_input_stream.h

Index: media/audio/fake_audio_input_stream.h
diff --git a/media/audio/fake_audio_input_stream.h b/media/audio/fake_audio_input_stream.h
index d9b186a844a9b97d3d3390d6787db2aca3f01f6c..438a3b97e07ee6bc2cdb4720c2df8d3be1c287a3 100644
--- a/media/audio/fake_audio_input_stream.h
+++ b/media/audio/fake_audio_input_stream.h
@@ -54,6 +54,10 @@ class MEDIA_EXPORT FakeAudioInputStream
   // input stream.
   static void BeepOnce();
 
+  // Set the muted state for _all_ FakeAudioInputStreams. The value is global,
+  // so it can be set before any FakeAudioInputStreams have been created.
+  static void SetMutedState(bool is_muted);
+
  private:
   FakeAudioInputStream(AudioManagerBase* manager,
                        const AudioParameters& params);