Remove unused base/threading/worker_pool.h includes.

chrome/browser/extensions/api/image_writer_private/operation_nonchromeos.cc

 // Copyright 2014 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.
 
 #include <stdint.h>
 
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
-#include "base/threading/worker_pool.h"
 #include "chrome/browser/extensions/api/image_writer_private/error_messages.h"
 #include "chrome/browser/extensions/api/image_writer_private/operation.h"
 #include "chrome/browser/extensions/api/image_writer_private/operation_manager.h"
 #include "content/public/browser/browser_thread.h"
 
 namespace extensions {
 namespace image_writer {
 
 using content::BrowserThread;
 
@@ skipping 35 matching lines @@
   }
 
   image_writer_client_->Verify(
       base::Bind(&Operation::WriteImageProgress, this, file_size),
       base::Bind(&Operation::CompleteAndContinue, this, continuation),
       base::Bind(&Operation::Error, this), image_path_, device_path_);
 }
 
 }  // namespace image_writer
 }  // namespace extensions