Add support for the audio-output-device switching IPC mechanism to the renderer lower layers (media…

media/audio/null_audio_sink.h

Index: media/audio/null_audio_sink.h
diff --git a/media/audio/null_audio_sink.h b/media/audio/null_audio_sink.h
index 1abdb996b5c0bbbd180a4f4fee6bcc0e566cba72..d8d5f0401ee1b851e189453ffeaf7dd6456daba1 100644
--- a/media/audio/null_audio_sink.h
+++ b/media/audio/null_audio_sink.h
@@ -32,6 +32,9 @@ class MEDIA_EXPORT NullAudioSink
   void Pause() override;
   void Play() override;
   bool SetVolume(double volume) override;
+  void SwitchOutputDevice(const std::string& device_id,
+                          const GURL& security_origin,
+                          const SwitchOutputDeviceCB& callback) override;
 
   // Enables audio frame hashing.  Must be called prior to Initialize().
   void StartAudioHashForTesting();