Update {virtual,override} to follow C++11 style in ash.

ash/system/win/audio/tray_audio_delegate_win.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 ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_DELEGATE_WIN_H_
 #define ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_DELEGATE_WIN_H_
 
 #include <audioclient.h>
 #include <mmdeviceapi.h>
 
 #include "ash/ash_export.h"
 #include "ash/system/audio/tray_audio_delegate.h"
 #include "base/compiler_specific.h"
 #include "base/win/scoped_comptr.h"
 
 namespace ash {
 namespace system {
 
 class ASH_EXPORT TrayAudioDelegateWin : public TrayAudioDelegate {
  public:
-  virtual ~TrayAudioDelegateWin() {}
+  ~TrayAudioDelegateWin() override {}
 
   // Overridden from TrayAudioDelegate.
-  virtual void AdjustOutputVolumeToAudibleLevel() override;
-  virtual int GetOutputDefaultVolumeMuteLevel() override;
-  virtual int GetOutputVolumeLevel() override;
-  virtual int GetActiveOutputDeviceIconId() override;
-  virtual bool HasAlternativeSources() override;
-  virtual bool IsOutputAudioMuted() override;
-  virtual void SetOutputAudioIsMuted(bool is_muted) override;
-  virtual void SetOutputVolumeLevel(int level) override;
-  virtual void SetInternalSpeakerChannelMode(AudioChannelMode mode) override;
+  void AdjustOutputVolumeToAudibleLevel() override;
+  int GetOutputDefaultVolumeMuteLevel() override;
+  int GetOutputVolumeLevel() override;
+  int GetActiveOutputDeviceIconId() override;
+  bool HasAlternativeSources() override;
+  bool IsOutputAudioMuted() override;
+  void SetOutputAudioIsMuted(bool is_muted) override;
+  void SetOutputVolumeLevel(int level) override;
+  void SetInternalSpeakerChannelMode(AudioChannelMode mode) override;
 
  private:
   base::win::ScopedComPtr<ISimpleAudioVolume> CreateDefaultVolumeControl();
 };
 
 }  // namespace system
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_WIN_AUDIO_TRAY_AUDIO_DELEGATE_WIN_H_