Update {virtual,override,final} to follow C++11 style in extensions, round 2.

extensions/shell/browser/shell_audio_controller_chromeos.h

 // 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.
 
 #ifndef EXTENSIONS_SHELL_BROWSER_SHELL_AUDIO_CONTROLLER_CHROMEOS_H_
 #define EXTENSIONS_SHELL_BROWSER_SHELL_AUDIO_CONTROLLER_CHROMEOS_H_
 
 #include "base/macros.h"
 #include "chromeos/audio/cras_audio_handler.h"
 
 namespace extensions {
 
 // Ensures that the "best" input and output audio devices are always active.
 class ShellAudioController : public chromeos::CrasAudioHandler::AudioObserver {
  public:
   ShellAudioController();
-  virtual ~ShellAudioController();
+  ~ShellAudioController() override;
 
   // chromeos::CrasAudioHandler::Observer implementation:
   void OnOutputVolumeChanged() override;
   void OnOutputMuteChanged() override;
   void OnInputGainChanged() override;
   void OnInputMuteChanged() override;
   void OnAudioNodesChanged() override;
   void OnActiveOutputNodeChanged() override;
   void OnActiveInputNodeChanged() override;
 
  private:
   // Gets the current device list from CRAS, chooses the best input and output
   // device, and activates them if they aren't already active.
   void ActivateDevices();
 
   DISALLOW_COPY_AND_ASSIGN(ShellAudioController);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_SHELL_BROWSER_SHELL_AUDIO_CONTROLLER_CHROMEOS_H_