Add IPC interface for switching the audio output device for a given audio stream in the browser.

media/audio/audio_logging.h

Index: media/audio/audio_logging.h
diff --git a/media/audio/audio_logging.h b/media/audio/audio_logging.h
index 913b8ec4433552bf41e22e734ecd00896c2bb714..4d7551f2021d9eb770e887dd80c25a18caa4a753 100644
--- a/media/audio/audio_logging.h
+++ b/media/audio/audio_logging.h
@@ -43,6 +43,11 @@ class AudioLog {
 
   // Called when an audio component changes volume.  |volume| is the new volume.
   virtual void OnSetVolume(int component_id, double volume) = 0;
+
+  // Called when an audio component switches output device. |device_id| is the
+  // new audio output device.
+  virtual void OnSwitchOutputDevice(int component_id,
+                                    const std::string& device_id) = 0;
 };
 
 // AudioLogFactory dispenses AudioLog instances to owning classes for tracking