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

extensions/browser/content_hash_fetcher.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 "extensions/browser/content_hash_fetcher.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <memory>
 #include <vector>
 
 #include "base/base64.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
 #include "base/json/json_reader.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/synchronization/lock.h"
 #include "base/task_runner_util.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/timer/elapsed_timer.h"
 #include "base/version.h"
 #include "content/public/browser/browser_thread.h"
 #include "crypto/sha2.h"
 #include "extensions/browser/computed_hashes.h"
 #include "extensions/browser/content_hash_tree.h"
 #include "extensions/browser/content_verifier_delegate.h"
 #include "extensions/browser/verified_contents.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension.h"
@@ skipping 466 matching lines @@
 
   for (JobMap::iterator i = jobs_.begin(); i != jobs_.end(); ++i) {
     if (i->second.get() == job) {
       jobs_.erase(i);
       break;
     }
   }
 }
 
 }  // namespace extensions