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

chrome/browser/ui/views/message_center/web_notification_tray.h

 // Copyright 2013 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 CHROME_BROWSER_UI_VIEWS_MESSAGE_CENTER_WEB_NOTIFICATION_TRAY_H_
 #define CHROME_BROWSER_UI_VIEWS_MESSAGE_CENTER_WEB_NOTIFICATION_TRAY_H_
 
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/pref_member.h"
 #include "chrome/browser/status_icons/status_icon_menu_model.h"
@@ skipping 49 matching lines @@
   void HidePopups() override;
   bool ShowMessageCenter() override;
   void HideMessageCenter() override;
   void OnMessageCenterTrayChanged() override;
   bool ShowNotifierSettings() override;
   bool IsContextMenuEnabled() const override;
 
   // StatusIconObserver implementation.
   void OnStatusIconClicked() override;
 #if defined(OS_WIN)
-  virtual void OnBalloonClicked() override;
+  void OnBalloonClicked() override;
 
   // This shows a platform-specific balloon informing the user of the existence
   // of the message center in the status tray area.
   void DisplayFirstRunBalloon();
 
   void EnforceStatusIconVisible();
 #endif
 
   // StatusIconMenuModel::Delegate implementation.
   void ExecuteCommand(int command_id, int event_flags) override;
@@ skipping 43 matching lines @@
   bool should_update_tray_content_;
   bool last_quiet_mode_state_;
   base::string16 title_;
 
   DISALLOW_COPY_AND_ASSIGN(WebNotificationTray);
 };
 
 }  // namespace message_center
 
 #endif  // CHROME_BROWSER_UI_VIEWS_MESSAGE_CENTER_WEB_NOTIFICATION_TRAY_H_