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

ash/system/chromeos/screen_security/screen_capture_tray_item.h

 // Copyright 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 ASH_SYSTEM_CHROMEOS_SCREEN_CAPTURE_SCREEN_CAPTURE_TRAY_ITEM_H_
 #define ASH_SYSTEM_CHROMEOS_SCREEN_CAPTURE_SCREEN_CAPTURE_TRAY_ITEM_H_
 
 #include "ash/system/chromeos/screen_security/screen_capture_observer.h"
 #include "ash/system/chromeos/screen_security/screen_tray_item.h"
 
 namespace views {
 class View;
 }
 
 namespace ash {
 
 class ASH_EXPORT ScreenCaptureTrayItem : public ScreenTrayItem,
                                          public ScreenCaptureObserver {
  public:
   explicit ScreenCaptureTrayItem(SystemTray* system_tray);
-  virtual ~ScreenCaptureTrayItem();
+  ~ScreenCaptureTrayItem() override;
 
  private:
   // Overridden from SystemTrayItem.
-  virtual views::View* CreateTrayView(user::LoginStatus status) override;
-  virtual views::View* CreateDefaultView(user::LoginStatus status) override;
+  views::View* CreateTrayView(user::LoginStatus status) override;
+  views::View* CreateDefaultView(user::LoginStatus status) override;
 
   // Overridden from ScreenTrayItem.
-  virtual void CreateOrUpdateNotification() override;
-  virtual std::string GetNotificationId() override;
+  void CreateOrUpdateNotification() override;
+  std::string GetNotificationId() override;
 
   // Overridden from ScreenCaptureObserver.
-  virtual void OnScreenCaptureStart(
+  void OnScreenCaptureStart(
       const base::Closure& stop_callback,
       const base::string16& screen_capture_status) override;
-  virtual void OnScreenCaptureStop() override;
+  void OnScreenCaptureStop() override;
 
   base::string16 screen_capture_status_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenCaptureTrayItem);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_SCREEN_CAPTURE_SCREEN_CAPTURE_TRAY_ITEM_H_