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

ash/system/chromeos/virtual_keyboard/virtual_keyboard_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_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_TRAY_H_
 #define ASH_SYSTEM_CHROMEOS_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_TRAY_H_
 
 #include "ash/system/tray/tray_background_view.h"
 #include "ash/system/tray_accessibility.h"
 #include "ash/system/user/login_status.h"
 #include "base/basictypes.h"
 #include "ui/views/controls/button/button.h"
 
 namespace views {
 class ImageButton;
 }
 
 namespace ash {
 class StatusAreaWidget;
 
 class VirtualKeyboardTray : public TrayBackgroundView,
                             public views::ButtonListener,
                             public AccessibilityObserver {
  public:
   explicit VirtualKeyboardTray(StatusAreaWidget* status_area_widget);
-  virtual ~VirtualKeyboardTray();
+  ~VirtualKeyboardTray() 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;
-  virtual bool PerformAction(const ui::Event& event) override;
+  void SetShelfAlignment(ShelfAlignment alignment) override;
+  base::string16 GetAccessibleNameForTray() override;
+  void HideBubbleWithView(const views::TrayBubbleView* bubble_view) override;
+  bool ClickedOutsideBubble() override;
+  bool PerformAction(const ui::Event& event) override;
 
   // views::ButtonListener:
-  virtual void ButtonPressed(views::Button* sender,
-                             const ui::Event& event) override;
+  void ButtonPressed(views::Button* sender, const ui::Event& event) override;
 
   // AccessibilityObserver:
-  virtual void OnAccessibilityModeChanged(
+  void OnAccessibilityModeChanged(
       ui::AccessibilityNotificationVisibility notify) override;
 
  private:
   views::ImageButton* button_;  // Not owned.
 
   DISALLOW_COPY_AND_ASSIGN(VirtualKeyboardTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_TRAY_H_