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

extensions/browser/content_hash_fetcher_unittest.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 <memory>
 
 #include "base/callback.h"
 #include "base/callback_helpers.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/weak_ptr.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/version.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/test/test_browser_thread_bundle.h"
 #include "extensions/browser/content_hash_fetcher.h"
 #include "extensions/browser/content_verifier_delegate.h"
 #include "extensions/browser/extensions_test.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension_paths.h"
 #include "extensions/common/file_util.h"
 #include "net/url_request/test_url_request_interceptor.h"
@@ skipping 224 matching lines @@
   EXPECT_TRUE(
       base::ContainsKey(result->mismatch_paths, script_path.BaseName()));
 
   // Make sure the verified_contents.json file was written into the extension's
   // install dir.
   EXPECT_TRUE(
       base::PathExists(file_util::GetVerifiedContentsPath(extension->path())));
 }
 
 }  // namespace extensions