Create a secondary file thread, FILE_USER_BLOCKING...

chrome/test/base/testing_browser_process.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.
 
 // An implementation of BrowserProcess for unit tests that fails for most
 // services. By preventing creation of services, we reduce dependencies and
 // keep the profile clean. Clients of this class must handle the NULL return
 // value, however.
 
 #ifndef CHROME_TEST_BASE_TESTING_BROWSER_PROCESS_H_
@@ skipping 31 matching lines @@
 class TestingBrowserProcess : public BrowserProcess {
  public:
   TestingBrowserProcess();
   virtual ~TestingBrowserProcess();
 
   virtual void EndSession() OVERRIDE;
   virtual ResourceDispatcherHost* resource_dispatcher_host() OVERRIDE;
   virtual MetricsService* metrics_service() OVERRIDE;
   virtual IOThread* io_thread() OVERRIDE;
 
+  virtual base::Thread* file_user_blocking_thread() OVERRIDE;
   virtual base::Thread* file_thread() OVERRIDE;
   virtual base::Thread* db_thread() OVERRIDE;
   virtual base::Thread* cache_thread() OVERRIDE;
   virtual WatchDogThread* watchdog_thread() OVERRIDE;
 
 #if defined(OS_CHROMEOS)
   virtual base::Thread* web_socket_proxy_thread() OVERRIDE;
 #endif
 
   virtual ProfileManager* profile_manager() OVERRIDE;
@@ skipping 74 matching lines @@
   scoped_ptr<printing::BackgroundPrintingManager> background_printing_manager_;
   scoped_refptr<printing::PrintPreviewTabController>
       print_preview_tab_controller_;
   scoped_ptr<prerender::PrerenderTracker> prerender_tracker_;
   IOThread* io_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(TestingBrowserProcess);
 };
 
 #endif  // CHROME_TEST_BASE_TESTING_BROWSER_PROCESS_H_