Revert 255158 "Avoid hitting the thread check when WebRtcAudioRe..."

trunk/src/content/renderer/media/webrtc_audio_device_impl.h

Index: trunk/src/content/renderer/media/webrtc_audio_device_impl.h
===================================================================
--- trunk/src/content/renderer/media/webrtc_audio_device_impl.h	(revision 256663)
+++ trunk/src/content/renderer/media/webrtc_audio_device_impl.h	(working copy)
@@ -240,15 +240,9 @@
   class Sink {
    public:
     // Callback to get the playout data.
-    // Called on the render audio thread.
     virtual void OnPlayoutData(media::AudioBus* audio_bus,
                                int sample_rate,
                                int audio_delay_milliseconds) = 0;
-
-    // Callback to notify the sink that the source has changed.
-    // Called on the main render thread.
-    virtual void OnPlayoutDataSourceChanged() = 0;
-
    protected:
     virtual ~Sink() {}
   };