Replace more ObserverList with base::ObserverList.

components/ui/zoom/zoom_event_manager.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 COMPONENTS_UI_ZOOM_ZOOM_EVENT_MANAGER_H_
 #define COMPONENTS_UI_ZOOM_ZOOM_EVENT_MANAGER_H_
 
 #include "base/callback_list.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
@@ skipping 42 matching lines @@
   // Get a weak ptr to be used by clients who may themselves be UserData for
   // the context, since the order of destruction is undefined between the client
   // and this class.
   base::WeakPtr<ZoomEventManager> GetWeakPtr() {
     return weak_ptr_factory_.GetWeakPtr();
   }
 
  private:
   base::CallbackList<void(const content::HostZoomMap::ZoomLevelChange&)>
       zoom_level_changed_callbacks_;
-  ObserverList<ZoomEventManagerObserver> observers_;
+  base::ObserverList<ZoomEventManagerObserver> observers_;
   base::WeakPtrFactory<ZoomEventManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ZoomEventManager);
 };
 
 }  // namespace ui_zoom
 
 #endif  // COMPONENTS_UI_ZOOM_ZOOM_EVENT_MANAGER_H_