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

ash/system/chromeos/label_tray_view.h

 // Copyright (c) 2012 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_LABEL_TRAY_VIEW_H_
 #define ASH_SYSTEM_CHROMEOS_LABEL_TRAY_VIEW_H_
 
 #include "base/strings/string16.h"
 #include "ui/views/view.h"
 
 namespace ash {
 
 class ViewClickListener;
 
 // View for simple information in tray. Automatically hides when message is
 // empty. Supports multiline messages.
 
 class LabelTrayView : public views::View {
  public:
   LabelTrayView(ViewClickListener* click_listener, int icon_resource_id);
-  virtual ~LabelTrayView();
+  ~LabelTrayView() override;
   void SetMessage(const base::string16& message);
  private:
   views::View* CreateChildView(const base::string16& message) const;
 
   ViewClickListener* click_listener_;
   int icon_resource_id_;
   base::string16 message_;
 
   DISALLOW_COPY_AND_ASSIGN(LabelTrayView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_LABEL_TRAY_VIEW_H_