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

ash/system/chromeos/supervised/tray_supervised_user.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_CHROMEOS_SUPERVISED_TRAY_SUPERVISED_USER_H
 #define ASH_SYSTEM_CHROMEOS_SUPERVISED_TRAY_SUPERVISED_USER_H
 
 #include "ash/ash_export.h"
 #include "ash/system/chromeos/supervised/custodian_info_tray_observer.h"
 #include "ash/system/tray/system_tray_item.h"
 #include "ash/system/tray/view_click_listener.h"
 #include "base/strings/string16.h"
 
 namespace ash {
 class LabelTrayView;
 class SystemTray;
 
 class ASH_EXPORT TraySupervisedUser : public SystemTrayItem,
                                       public ViewClickListener,
                                       public CustodianInfoTrayObserver {
  public:
   explicit TraySupervisedUser(SystemTray* system_tray);
-  virtual ~TraySupervisedUser();
+  ~TraySupervisedUser() override;
 
   // If message is not empty updates content of default view, otherwise hides
   // tray items.
   void UpdateMessage();
 
   // Overridden from SystemTrayItem.
-  virtual views::View* CreateDefaultView(user::LoginStatus status) override;
-  virtual void DestroyDefaultView() override;
-  virtual void UpdateAfterLoginStatusChange(user::LoginStatus status) override;
+  views::View* CreateDefaultView(user::LoginStatus status) override;
+  void DestroyDefaultView() override;
+  void UpdateAfterLoginStatusChange(user::LoginStatus status) override;
 
   // Overridden from ViewClickListener.
-  virtual void OnViewClicked(views::View* sender) override;
+  void OnViewClicked(views::View* sender) override;
 
   // Overridden from CustodianInfoTrayObserver:
-  virtual void OnCustodianInfoChanged() override;
+  void OnCustodianInfoChanged() override;
 
  private:
   friend class TraySupervisedUserTest;
 
   static const char kNotificationId[];
 
   void CreateOrUpdateNotification(const base::string16& new_message);
 
   void CreateOrUpdateSupervisedWarningNotification();
 
   LabelTrayView* tray_view_;
 
   // Previous login status to avoid showing notification upon unlock.
   user::LoginStatus status_;
 
   // Previous user supervised state to avoid showing notification upon unlock.
   bool is_user_supervised_;
 
   DISALLOW_COPY_AND_ASSIGN(TraySupervisedUser);
 };
 
 } // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_SUPERVISED_TRAY_SUPERVISED_USER_H