Enforce marking "override" for functions overriding Blink.

content/child/webthemeengine_impl_default.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 CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_
 #define CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_
 
 #include "third_party/WebKit/public/platform/WebThemeEngine.h"
 
 namespace content {
 
 class WebThemeEngineImpl : public blink::WebThemeEngine {
  public:
   // WebThemeEngine methods:
-  virtual blink::WebSize getSize(blink::WebThemeEngine::Part);
-  virtual void paint(
-      blink::WebCanvas* canvas,
-      blink::WebThemeEngine::Part part,
-      blink::WebThemeEngine::State state,
-      const blink::WebRect& rect,
-      const blink::WebThemeEngine::ExtraParams* extra_params);
+  blink::WebSize getSize(blink::WebThemeEngine::Part) override;
+  void paint(blink::WebCanvas* canvas,
+             blink::WebThemeEngine::Part part,
+             blink::WebThemeEngine::State state,
+             const blink::WebRect& rect,
+             const blink::WebThemeEngine::ExtraParams* extra_params) override;
   virtual void paintStateTransition(blink::WebCanvas* canvas,
                                     blink::WebThemeEngine::Part part,
                                     blink::WebThemeEngine::State startState,
                                     blink::WebThemeEngine::State endState,
                                     double progress,
                                     const blink::WebRect& rect);
 
 #if defined(OS_WIN)
   // Caches the scrollbar metrics.
   static void cacheScrollBarMetrics(int32 vertical_scroll_bar_width,
                                     int32 horizontal_scroll_bar_height,
                                     int32 vertical_arrow_bitmap_height,
                                     int32 horizontal_arrow_bitmap_width);
 #endif
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_