Get rid of MessageLoop* caching in extensions code.

chrome/browser/extensions/sandboxed_extension_unpacker.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_SANDBOXED_EXTENSION_UNPACKER_H_
 #define CHROME_BROWSER_EXTENSIONS_SANDBOXED_EXTENSION_UNPACKER_H_
 
 #include <string>
 
 #include "base/file_path.h"
@@ skipping 106 matching lines @@
 
   // SandboxedExtensionUnpacker
   void OnUnpackExtensionSucceeded(const DictionaryValue& manifest);
   void OnUnpackExtensionFailed(const std::string& error_message);
   void OnProcessCrashed();
 
   void ReportFailure(const std::string& message);
   void ReportSuccess();
 
   FilePath crx_path_;
-  MessageLoop* file_loop_;
+  ChromeThread::ID thread_identifier_;
   ResourceDispatcherHost* rdh_;
   scoped_refptr<SandboxedExtensionUnpackerClient> client_;
   ScopedTempDir temp_dir_;
   FilePath extension_root_;
   scoped_ptr<Extension> extension_;
   bool got_response_;
   std::string public_key_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SANDBOXED_EXTENSION_UNPACKER_H_