Implement new audio handler which talks to the new audio dbus apis.

chromeos/dbus/cras_audio_client.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_DBUS_CRAS_AUDIO_CLIENT_H_
 #define CHROMEOS_DBUS_CRAS_AUDIO_CLIENT_H_
 
 #include "base/callback.h"
 #include "base/observer_list.h"
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/audio_node.h"
 #include "chromeos/dbus/dbus_client_implementation_type.h"
 #include "chromeos/dbus/volume_state.h"
 
 namespace dbus {
 class Bus;
 }  // namespace
 
 namespace chromeos {
 
 // CrasAudioClient is used to communicate with the cras audio dbus interface.
 class CHROMEOS_EXPORT CrasAudioClient {
  public:
   // Interface for observing changes from the cras audio changes.
   class Observer {
    public:
-    // Called when audio output device volume changed.
+    // Called when cras audio client starts or re-starts, which happens when
+    // cros device powers up or restarted.
+    virtual void AudioClientRestarted();
+
+    // Called when audio output device volume changed to new value of |volume|.
     virtual void OutputVolumeChanged(int volume);
+
+    // Called whne audio output mute state changed to new state of |mute_on|.
     virtual void OutputMuteChanged(bool mute_on);
+
+    // Called when audio input gain changeg to new value of |gain|.
     virtual void InputGainChanged(int gain);
+
+    // Called when audio input mute state changed to new state of |mute_on|.
     virtual void InputMuteChanged(bool mute_on);
+
+    // Called when audio nodes change.
     virtual void NodesChanged();
+
+    // Called when active audio output node changed to new node with |node_id|.
     virtual void ActiveOutputNodeChanged(uint64 node_id);
+
+    // Called when active audio input node changed to new node with |node_id|.
     virtual void ActiveInputNodeChanged(uint64 node_id);
 
    protected:
     virtual ~Observer();
   };
 
   virtual ~CrasAudioClient();
 
   // Adds and removes the observer.
   virtual void AddObserver(Observer* observer) = 0;
@@ skipping 45 matching lines @@
   CrasAudioClient();
 
  private:
 
   DISALLOW_COPY_AND_ASSIGN(CrasAudioClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_CRAS_AUDIO_CLIENT_H_