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

chrome/browser/ntp_snippets/content_suggestions_service_factory.cc

 // Copyright 2016 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/ntp_snippets/content_suggestions_service_factory.h"
 
 #include <utility>
 
 #include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/time/default_clock.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search/suggestions/image_decoder_impl.h"
 #include "chrome/browser/signin/profile_oauth2_token_service_factory.h"
 #include "chrome/browser/signin/signin_manager_factory.h"
 #include "chrome/browser/sync/profile_sync_service_factory.h"
 #include "chrome/browser/translate/language_model_factory.h"
@@ skipping 322 matching lines @@
           ntp_snippets::kForeignSessionsSuggestionsFeature)) {
     RegisterForeignSessionsProvider(sync_service, service, pref_service);
   }
 
   return service;
 
 #else
   return nullptr;
 #endif  // CONTENT_SUGGESTIONS_ENABLED
 }