Replace more ObserverList with base::ObserverList.

ui/gfx/display_change_notifier.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 UI_GFX_DISPLAY_CHANGE_NOTIFIER_H_
 #define UI_GFX_DISPLAY_CHANGE_NOTIFIER_H_
 
 #include <vector>
 
 #include "base/observer_list.h"
@@ skipping 14 matching lines @@
   void AddObserver(DisplayObserver* observer);
 
   void RemoveObserver(DisplayObserver* observer);
 
   void NotifyDisplaysChanged(const std::vector<Display>& old_displays,
                              const std::vector<Display>& new_displays);
 
  private:
   // The observers that need to be notified when a display is modified, added
   // or removed.
-  ObserverList<DisplayObserver> observer_list_;
+  base::ObserverList<DisplayObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayChangeNotifier);
 };
 
 } // namespace gfx
 
 #endif // UI_GFX_DISPLAY_CHANGE_NOTIFIER_H_