Revert of Remove header dependencies from sequence_checker.h to sequenced_worker_pool.h

chrome/browser/sync_file_system/drive_backend/sync_engine_context.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 "chrome/browser/sync_file_system/drive_backend/sync_engine_context.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database.h"
 #include "chrome/browser/sync_file_system/remote_change_processor.h"
 #include "chrome/browser/sync_file_system/task_logger.h"
 #include "components/drive/drive_uploader.h"
 #include "components/drive/service/drive_service_interface.h"
 
 namespace sync_file_system {
 namespace drive_backend {
 
 SyncEngineContext::SyncEngineContext(
@@ skipping 76 matching lines @@
   DCHECK(remote_change_processor);
   remote_change_processor_ = remote_change_processor;
 }
 
 void SyncEngineContext::DetachFromSequence() {
   sequence_checker_.DetachFromSequence();
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system