Standardize usage of virtual/override/final in extensions/

extensions/browser/app_window/native_app_window.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 EXTENSIONS_BROWSER_APP_WINDOW_NATIVE_APP_WINDOW_H_
 #define EXTENSIONS_BROWSER_APP_WINDOW_NATIVE_APP_WINDOW_H_
 
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 81 matching lines @@
   virtual void SetContentSizeConstraints(const gfx::Size& min_size,
                                          const gfx::Size& max_size) = 0;
 
   // Returns whether the window show be visible on all workspaces.
   virtual void SetVisibleOnAllWorkspaces(bool always_visible) = 0;
 
   // Returns false if the underlying native window ignores alpha transparency
   // when compositing.
   virtual bool CanHaveAlphaEnabled() const = 0;
 
-  virtual ~NativeAppWindow() {}
+  ~NativeAppWindow() override {}
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_APP_WINDOW_NATIVE_APP_WINDOW_H_