Create a secondary file thread, FILE_USER_BLOCKING...

content/browser/browser_main_loop.h

 // Copyright (c) 2011 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 CONTENT_BROWSER_BROWSER_MAIN_LOOP_H_
 #define CONTENT_BROWSER_BROWSER_MAIN_LOOP_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 61 matching lines @@
 #endif
 
   // Destroy parts_ before main_message_loop_ (required) and before other
   // classes constructed in content (but after main_thread_).
   scoped_ptr<BrowserMainParts> parts_;
 
   // Members initialized in |InitializeMainThread()| ---------------------------
   // This must get destroyed before other threads that are created in parts_.
   scoped_ptr<BrowserThreadImpl> main_thread_;
   scoped_ptr<BrowserProcessSubThread> io_thread_;
+  scoped_ptr<BrowserProcessSubThread> file_user_blocking_thread_;
   scoped_ptr<BrowserProcessSubThread> file_thread_;
   scoped_ptr<BrowserProcessSubThread> db_thread_;
   scoped_ptr<BrowserProcessSubThread> process_launcher_thread_;
   scoped_ptr<BrowserProcessSubThread> cache_thread_;
 #if defined(OS_CHROMEOS)
   scoped_ptr<BrowserProcessSubThread> web_socket_proxy_thread_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(BrowserMainLoop);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BROWSER_MAIN_LOOP_H_