Add a new audio extension event OnLevelChanged.

extensions/shell/browser/shell_audio_controller_chromeos.cc

 // Copyright 2014 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.
 
 #include "extensions/shell/browser/shell_audio_controller_chromeos.h"
 
 #include <algorithm>
 
 #include "chromeos/audio/audio_device.h"
 
@@ skipping 17 matching lines @@
 
 ShellAudioController::ShellAudioController() {
   chromeos::CrasAudioHandler::Get()->AddAudioObserver(this);
   ActivateDevices();
 }
 
 ShellAudioController::~ShellAudioController() {
   chromeos::CrasAudioHandler::Get()->RemoveAudioObserver(this);
 }
 
-void ShellAudioController::OnOutputVolumeChanged() {}
+void ShellAudioController::OnOutputNodeVolumeChanged(uint64 node_id,
+                                                     double volume) {
+}
 
 void ShellAudioController::OnOutputMuteChanged() {}
 
 void ShellAudioController::OnInputGainChanged() {}
 
 void ShellAudioController::OnInputMuteChanged() {}
 
 void ShellAudioController::OnAudioNodesChanged() {
   VLOG(1) << "Audio nodes changed";
   ActivateDevices();
@@ skipping 27 matching lines @@
   }
   if (best_output && best_output != handler->GetPrimaryActiveOutputNode()) {
     const chromeos::AudioDevice* device = GetDevice(devices, best_output);
     DCHECK(device);
     VLOG(1) << "Activating output device: " << device->ToString();
     handler->SwitchToDevice(*device, true);
   }
 }
 
 }  // namespace extensions