Add a new audio extension event OnLevelChanged.

chromeos/audio/cras_audio_handler.h

 // Copyright (c) 2013 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 CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_
 #define CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_
 
 #include <queue>
 
 #include "base/basictypes.h"
@@ skipping 19 matching lines @@
                                          public SessionManagerClient::Observer {
  public:
   typedef std::priority_queue<AudioDevice,
                               std::vector<AudioDevice>,
                               AudioDeviceCompare> AudioDevicePriorityQueue;
   typedef std::vector<uint64> NodeIdList;
 
   class AudioObserver {
    public:
     // Called when output volume changed.
-    virtual void OnOutputVolumeChanged();
+    virtual void OnOutputNodeVolumeChanged(uint64 node_id, double volume);
 
     // Called when output mute state changed.
     virtual void OnOutputMuteChanged();
 
     // Called when input mute state changed.
     virtual void OnInputGainChanged();
 
     // Called when input mute state changed.
     virtual void OnInputMuteChanged();
 
@@ skipping 278 matching lines @@
   bool log_errors_;
 
   base::WeakPtrFactory<CrasAudioHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CrasAudioHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_AUDIO_CRAS_AUDIO_HANDLER_H_