Handle audio device changes on Mac

media/audio/mac/audio_manager_mac.h

Index: media/audio/mac/audio_manager_mac.h
diff --git a/media/audio/mac/audio_manager_mac.h b/media/audio/mac/audio_manager_mac.h
index d655d4b11ed9d54fac49daf85f6dd13de0916fd9..cd138cc50518d7ca770f26f489a3457b35f66372 100644
--- a/media/audio/mac/audio_manager_mac.h
+++ b/media/audio/mac/audio_manager_mac.h
@@ -11,6 +11,8 @@
 
 namespace media {
 
+class AudioDeviceListenerMac;
+
 // Mac OS X implementation of the AudioManager singleton. This class is internal
 // to the audio output and only internal users can call methods not exposed by
 // the AudioManager class.
@@ -38,6 +40,9 @@ class MEDIA_EXPORT AudioManagerMac : public AudioManagerBase {
   virtual ~AudioManagerMac();
 
  private:
+  // Listens for output device changes.
+  scoped_ptr<AudioDeviceListenerMac> output_device_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerMac);
 };