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

chrome/browser/ui/android/window_android_helper.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 CHROME_BROWSER_UI_ANDROID_WINDOW_ANDROID_HELPER_H_
 #define CHROME_BROWSER_UI_ANDROID_WINDOW_ANDROID_HELPER_H_
 
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace ui {
 class WindowAndroid;
 }
 
 // Per-tab class to provide access to WindowAndroid object.
 class WindowAndroidHelper
     : public content::WebContentsUserData<WindowAndroidHelper> {
  public:
-  virtual ~WindowAndroidHelper();
+  ~WindowAndroidHelper() override;
 
   void SetWindowAndroid(ui::WindowAndroid* window_android);
   ui::WindowAndroid* GetWindowAndroid();
 
  private:
   explicit WindowAndroidHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<WindowAndroidHelper>;
 
   // The owning window that has a hold of main application activity.
   ui::WindowAndroid* window_android_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowAndroidHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_ANDROID_WINDOW_ANDROID_HELPER_H_