Introduce AudioStateNotifier.

- Handles device state change notifications.
- Allows AudioOutputController to restart its underlying stream
when necessary.

BUG=153056
TEST=new unittest.

Review URL: https://chromiumcodereview.appspot.com/11193029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@163478 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 12 insertions, 0 deletions

diff --git a/media/audio/audio_manager.h b/media/audio/audio_manager.h
index a34027f..3b61bde 100644
--- a/media/audio/audio_manager.h
+++ b/media/audio/audio_manager.h
@@ -112,6 +112,18 @@ class MEDIA_EXPORT AudioManager {
   // Returns message loop used for audio IO.
   virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() = 0;
 
+  // Allows clients to listen for device state changes; e.g. preferred sample
+  // rate or channel layout changes.  The typical response to receiving this
+  // callback is to recreate the stream.
+  class AudioDeviceListener {
+   public:
+    virtual void OnDeviceChange() = 0;
+  };
+
+  virtual void AddOutputDeviceChangeListener(AudioDeviceListener* listener) = 0;
+  virtual void RemoveOutputDeviceChangeListener(
+      AudioDeviceListener* listener) = 0;
+
  protected:
   AudioManager();