Handle audio device changes on Mac

media/audio/mac/audio_device_listener_mac.h

Index: media/audio/mac/audio_device_listener_mac.h
diff --git a/media/audio/mac/audio_device_listener_mac.h b/media/audio/mac/audio_device_listener_mac.h
new file mode 100644
index 0000000000000000000000000000000000000000..7e8f6c5d9a759856c4271cac450b9899e2f990f6
--- /dev/null
+++ b/media/audio/mac/audio_device_listener_mac.h
@@ -0,0 +1,39 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_AUDIO_MAC_AUDIO_DEVICE_LISTENER_MAC_H_
+#define MEDIA_AUDIO_MAC_AUDIO_DEVICE_LISTENER_MAC_H_
+
+#include <CoreAudio/CoreAudio.h>
+
+#include "base/callback.h"
+#include "base/threading/thread_checker.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// Listens for default device changes and forwards them to AudioManagerMac so it
+// can notify downstream clients. Only output device changes are supported
+// currently.
+class MEDIA_EXPORT AudioDeviceListenerMac {
+ public:
+  explicit AudioDeviceListenerMac(const base::Closure& listener_cb);

[DaleCurtis, 2012/10/29 01:58:45]

Include comment from the Windows version that |listener_cb| is a permanent
callback.

[sail, 2012/10/29 04:21:46]

Done.

+  ~AudioDeviceListenerMac();
+
+ private:
+  friend class AudioDeviceListenerMacTest;
+
+  static OSStatus OnDefaultDeviceChanged(

[DaleCurtis, 2012/10/29 01:58:45]

Just make this a static method within the class since it gets the pointer
through |content|, then you can drop the #include <CoreAudio> too.

[sail, 2012/10/29 04:21:46]

Done.

+    AudioObjectID object,
+    UInt32 size,
+    const AudioObjectPropertyAddress addresses[],
+    void* context);
+
+  base::Closure listener_cb_;
+  base::ThreadChecker thread_checker_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_MAC_AUDIO_DEVICE_LISTENER_MAC_H_