Standardize usage of virtual/override/final in content/browser/

content/browser/theme_helper_mac.h

 // Copyright 2013 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_THEME_HELPER_MAC_H_
 #define CONTENT_BROWSER_THEME_HELPER_MAC_H_
 
 #include "base/memory/singleton.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ skipping 15 matching lines @@
       float initial_button_delay,
       float autoscroll_button_delay,
       bool jump_on_track_click,
       blink::ScrollerStyle preferred_scroller_style,
       bool redraw);
 
  private:
   friend struct DefaultSingletonTraits<ThemeHelperMac>;
 
   ThemeHelperMac();
-  virtual ~ThemeHelperMac();
+  ~ThemeHelperMac() override;
 
   // Overridden from NotificationObserver:
-  virtual void Observe(int type,
-                       const NotificationSource& source,
-                       const NotificationDetails& details) override;
+  void Observe(int type,
+               const NotificationSource& source,
+               const NotificationDetails& details) override;
 
   NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ThemeHelperMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_THEME_HELPER_MAC_H_