Add missing #include around sequenced_worker_pool.h in //chrome

chrome/browser/supervised_user/experimental/supervised_user_blacklist.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/supervised_user/experimental/supervised_user_blacklist.h"
 
 #include <algorithm>
 #include <cstring>
 #include <fstream>
 
 #include "base/files/file_path.h"
 #include "base/files/memory_mapped_file.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "content/public/browser/browser_thread.h"
 #include "url/gurl.h"
 
 using content::BrowserThread;
 
 namespace {
 
 std::unique_ptr<std::vector<SupervisedUserBlacklist::Hash>>
 ReadFromBinaryFileOnFileThread(const base::FilePath& path) {
   DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
@@ skipping 63 matching lines @@
 
 void SupervisedUserBlacklist::OnReadFromFileCompleted(
     const base::Closure& done_callback,
     std::unique_ptr<std::vector<Hash>> host_hashes) {
   host_hashes_.swap(*host_hashes);
   LOG_IF(WARNING, host_hashes_.empty()) << "Got empty blacklist";
 
   if (!done_callback.is_null())
     done_callback.Run();
 }