Replace more ObserverList with base::ObserverList.

ios/web/web_state/web_state_impl.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 IOS_WEB_WEB_STATE_WEB_STATE_IMPL_H_
 #define IOS_WEB_WEB_STATE_WEB_STATE_IMPL_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 265 matching lines @@
   // The CRWWebController that backs and owns this object.
   CRWWebController* web_controller_;
 
   NavigationManagerImpl navigation_manager_;
 
   // |web::WebUIIOS| object for the current page if it is a WebUI page that
   // uses the web-based WebUI framework, or nullptr otherwise.
   scoped_ptr<web::WebUIIOS> web_ui_;
 
   // A list of observers notified when page state changes. Weak references.
-  ObserverList<WebStateObserver, true> observers_;
+  base::ObserverList<WebStateObserver, true> observers_;
 
   // Map of all the HTTP response headers received, for each URL.
   // This map is cleared after each page load, and only the headers of the main
   // page are used.
   std::map<GURL, scoped_refptr<net::HttpResponseHeaders> >
       response_headers_map_;
   scoped_refptr<net::HttpResponseHeaders> http_response_headers_;
   std::string mime_type_;
   std::string content_language_header_;
 
@@ skipping 16 matching lines @@
 
   // Callbacks associated to command prefixes.
   std::map<std::string, ScriptCommandCallback> script_command_callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(WebStateImpl);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_WEB_STATE_WEB_STATE_IMPL_H_