Add OVERRIDE to chrome/browser/ui/gtk/.

chrome/browser/ui/gtk/overflow_button.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 CHROME_BROWSER_UI_GTK_OVERFLOW_BUTTON_H_
 #define CHROME_BROWSER_UI_GTK_OVERFLOW_BUTTON_H_
 #pragma once
 
+#include "base/compiler_specific.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/base/gtk/owned_widget_gtk.h"
 
 typedef struct _GtkWidget GtkWidget;
 class Profile;
 
 // An overflow chevron button. The button itself is a plain gtk_chrome_button,
 // and this class handles theming it.
 class OverflowButton : public content::NotificationObserver {
  public:
   explicit OverflowButton(Profile* profile);
   virtual ~OverflowButton();
 
   GtkWidget* widget() { return widget_.get(); }
 
  private:
   // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
-                       const content::NotificationDetails& details);
+                       const content::NotificationDetails& details) OVERRIDE;
 
   ui::OwnedWidgetGtk widget_;
 
   Profile* profile_;
 
   content::NotificationRegistrar registrar_;
 };
 
 #endif  // CHROME_BROWSER_UI_GTK_OVERFLOW_BUTTON_H_