Replace more ObserverList with base::ObserverList.

sync/js/sync_js_controller.h

 // Copyright 2012 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 SYNC_JS_SYNC_JS_CONTROLLER_H_
 #define SYNC_JS_SYNC_JS_CONTROLLER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 31 matching lines @@
   // JsEventHandler implementation.
   void HandleJsEvent(const std::string& name,
                      const JsEventDetails& details) override;
 
  private:
   // Sets |js_backend_|'s event handler depending on how many
   // underlying event handlers we have.
   void UpdateBackendEventHandler();
 
   WeakHandle<JsBackend> js_backend_;
-  ObserverList<JsEventHandler> js_event_handlers_;
+  base::ObserverList<JsEventHandler> js_event_handlers_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncJsController);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_JS_SYNC_JS_CONTROLLER_H_