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

ash/system/chromeos/audio/tray_audio_delegate_chromeos.h

Index: ash/system/chromeos/audio/tray_audio_delegate_chromeos.h
diff --git a/ash/system/chromeos/audio/tray_audio_delegate_chromeos.h b/ash/system/chromeos/audio/tray_audio_delegate_chromeos.h
index 24067d6ca0a3127d6ff4de9517e3a527f93b0a36..c51d246bcff49d04f5f992e5ac974072b78c44af 100644
--- a/ash/system/chromeos/audio/tray_audio_delegate_chromeos.h
+++ b/ash/system/chromeos/audio/tray_audio_delegate_chromeos.h
@@ -14,18 +14,18 @@ namespace system {
 
 class ASH_EXPORT TrayAudioDelegateChromeOs : public TrayAudioDelegate {
  public:
-  virtual ~TrayAudioDelegateChromeOs() {}
+  ~TrayAudioDelegateChromeOs() 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;
 };
 
 }  // namespace system