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

ash/system/chromeos/session/logout_confirmation_dialog.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_SESSION_LOGOUT_CONFIRMATION_DIALOG_H_
 #define ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_CONFIRMATION_DIALOG_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "ui/views/window/dialog_delegate.h"
 
 namespace views {
 class Label;
 }
 
 namespace ash {
 
 class LogoutConfirmationController;
 
 // A dialog that asks the user to confirm or deny logout. The dialog shows a
 // countdown and informs the user that a logout will happen automatically if no
 // choice is made before the countdown has expired.
 class LogoutConfirmationDialog : public views::DialogDelegateView {
  public:
   LogoutConfirmationDialog(LogoutConfirmationController* controller,
                            base::TimeTicks logout_time);
-  virtual ~LogoutConfirmationDialog();
+  ~LogoutConfirmationDialog() override;
 
   void Update(base::TimeTicks logout_time);
 
   // views::DialogDelegateView:
-  virtual bool Accept() override;
-  virtual ui::ModalType GetModalType() const override;
-  virtual base::string16 GetWindowTitle() const override;
-  virtual base::string16 GetDialogButtonLabel(ui::DialogButton button) const
-      override;
-  virtual void OnClosed() override;
-  virtual void DeleteDelegate() override;
+  bool Accept() override;
+  ui::ModalType GetModalType() const override;
+  base::string16 GetWindowTitle() const override;
+  base::string16 GetDialogButtonLabel(ui::DialogButton button) const override;
+  void OnClosed() override;
+  void DeleteDelegate() override;
 
  private:
   void UpdateLabel();
 
   LogoutConfirmationController* controller_;
   base::TimeTicks logout_time_;
 
   views::Label* label_;
 
   base::RepeatingTimer<LogoutConfirmationDialog> update_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LogoutConfirmationDialog);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_CONFIRMATION_DIALOG_H_