Use ExternalFileSystemBackend in the DriveURLRequestJob.

chrome/browser/chromeos/drive/drive_protocol_handler.h

 // Copyright (c) 2012 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_CHROMEOS_DRIVE_DRIVE_PROTOCOL_HANDLER_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_PROTOCOL_HANDLER_H_
 
 #include "base/basictypes.h"
-#include "base/memory/ref_counted.h"
 #include "net/url_request/url_request_job_factory.h"
 
 namespace base {
 class SequencedTaskRunner;
 }  // namespace base
 
 namespace drive {
 
 class DriveProtocolHandler : public net::URLRequestJobFactory::ProtocolHandler {
  public:
   explicit DriveProtocolHandler(void* profile_id);
   virtual ~DriveProtocolHandler();
 
   // Creates URLRequestJobs for drive:// URLs.
   virtual net::URLRequestJob* MaybeCreateJob(
       net::URLRequest* request,
       net::NetworkDelegate* network_delegate) const OVERRIDE;
 
  private:
   // The profile for processing Drive accesses. Should not be NULL.
   void* profile_id_;
 
-  // The task runner for operations to communicate with a locally cached file.
-  scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
-
   DISALLOW_COPY_AND_ASSIGN(DriveProtocolHandler);
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_PROTOCOL_HANDLER_H_