Add OVERRIDE to content/.

content/browser/tab_contents/popup_menu_helper_mac.h

 // Copyright (c) 2011 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_BROWSER_TAB_CONTENTS_POPUP_MENU_HELPER_MAC_H_
 #define CONTENT_BROWSER_TAB_CONTENTS_POPUP_MENU_HELPER_MAC_H_
 
 #include <vector>
 
+#include "base/compiler_specific.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/gfx/rect.h"
 
 class RenderViewHost;
 struct WebMenuItem;
 
 class PopupMenuHelper : public content::NotificationObserver {
  public:
   // Creates a PopupMenuHelper that will notify |render_view_host| when a user
   // selects or cancels the popup.
   explicit PopupMenuHelper(RenderViewHost* render_view_host);
 
   // Shows the popup menu and notifies the RenderViewHost of the selection/
   // cancel.
   // This call is blocking.
   void ShowPopupMenu(const gfx::Rect& bounds,
                      int item_height,
                      double item_font_size,
                      int selected_item,
                      const std::vector<WebMenuItem>& items,
                      bool right_aligned);
 
  private:
   // content::NotificationObserver implementation:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
-                       const content::NotificationDetails& details);
+                       const content::NotificationDetails& details) OVERRIDE;
 
   content::NotificationRegistrar notification_registrar_;
 
   RenderViewHost* render_view_host_;
 
   DISALLOW_COPY_AND_ASSIGN(PopupMenuHelper);
 };
 
 #endif  // CONTENT_BROWSER_TAB_CONTENTS_POPUP_MENU_HELPER_MAC_H_