Replace more ObserverList with base::ObserverList.

extensions/browser/app_window/app_window_geometry_cache.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 EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_GEOMETRY_CACHE_H_
 #define EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_GEOMETRY_CACHE_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 131 matching lines @@
   // The timer used to save the data.
   base::OneShotTimer<AppWindowGeometryCache> sync_timer_;
 
   // The timeout value we'll use for |sync_timer_|.
   base::TimeDelta sync_delay_;
 
   // Listen to extension load, unloaded notifications.
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;
 
-  ObserverList<Observer> observers_;
+  base::ObserverList<Observer> observers_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_APP_WINDOW_APP_WINDOW_GEOMETRY_CACHE_H_