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

ash/system/chromeos/session/logout_button_tray.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_BUTTON_TRAY_H_
 #define ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_BUTTON_TRAY_H_
 
 #include "ash/ash_export.h"
 #include "ash/system/chromeos/session/logout_button_observer.h"
 #include "ash/system/tray/tray_background_view.h"
@@ skipping 10 matching lines @@
 namespace ash {
 class StatusAreaWidget;
 
 // Adds a logout button to the launcher's status area if enabled by the
 // kShowLogoutButtonInTray pref.
 class ASH_EXPORT LogoutButtonTray : public TrayBackgroundView,
                                     public LogoutButtonObserver,
                                     public views::ButtonListener {
  public:
   explicit LogoutButtonTray(StatusAreaWidget* status_area_widget);
-  virtual ~LogoutButtonTray();
+  ~LogoutButtonTray() override;
 
   // TrayBackgroundView:
-  virtual void SetShelfAlignment(ShelfAlignment alignment) override;
-  virtual base::string16 GetAccessibleNameForTray() override;
-  virtual void HideBubbleWithView(
-      const views::TrayBubbleView* bubble_view) override;
-  virtual bool ClickedOutsideBubble() override;
+  void SetShelfAlignment(ShelfAlignment alignment) override;
+  base::string16 GetAccessibleNameForTray() override;
+  void HideBubbleWithView(const views::TrayBubbleView* bubble_view) override;
+  bool ClickedOutsideBubble() override;
 
   // LogoutButtonObserver:
-  virtual void OnShowLogoutButtonInTrayChanged(bool show) override;
-  virtual void OnLogoutDialogDurationChanged(base::TimeDelta duration) override;
+  void OnShowLogoutButtonInTrayChanged(bool show) override;
+  void OnLogoutDialogDurationChanged(base::TimeDelta duration) override;
 
   // views::ButtonListener:
-  virtual void ButtonPressed(views::Button* sender,
-                             const ui::Event& event) override;
+  void ButtonPressed(views::Button* sender, const ui::Event& event) override;
 
   void UpdateAfterLoginStatusChange(user::LoginStatus login_status);
 
  private:
   void UpdateVisibility();
 
   views::LabelButton* button_;
   user::LoginStatus login_status_;
   bool show_logout_button_in_tray_;
   base::TimeDelta dialog_duration_;
 
   DISALLOW_COPY_AND_ASSIGN(LogoutButtonTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_SESSION_LOGOUT_BUTTON_TRAY_H_