Get rid of MessageLoop* caching in extensions code.

chrome/browser/extensions/extension_message_service.h

 // Copyright (c) 2009 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 CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 121 matching lines @@
   // A map of channel ID to its channel object.
   typedef std::map<int, linked_ptr<MessageChannel> > MessageChannelMap;
 
   // Allocates a pair of port ids.
   // NOTE: this can be called from any thread.
   void AllocatePortIdPair(int* port1, int* port2);
 
   void CloseChannelImpl(MessageChannelMap::iterator channel_iter, int port_id,
                         bool notify_other_port);
 
-  // The UI message loop, used for posting tasks.
-  MessageLoop* ui_loop_;
-
   // --- UI thread only:
 
   // Handles channel creation and notifies the destinations that a channel was
   // opened.
   void OpenChannelToExtensionOnUIThread(
     int source_process_id, int source_routing_id, int receiver_port_id,
     const std::string& source_extension_id,
     const std::string& target_extension_id,
     const std::string& channel_name);
 
@@ skipping 37 matching lines @@
   int next_port_id_;
 
   // Protects the next_port_id_ variable, since it can be
   // used on the IO thread or the UI thread.
   Lock next_port_id_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionMessageService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_