Remove unused include in sequenced_worker_pool.h

components/browser_sync/signin_confirmation_helper.cc

 // Copyright 2015 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 "components/browser_sync/signin_confirmation_helper.h"
 
 #include <memory>
 
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string16.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/history/core/browser/history_backend.h"
 #include "components/history/core/browser/history_db_task.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/history/core/browser/history_types.h"
 
 namespace browser_sync {
 
 namespace {
@@ skipping 92 matching lines @@
   if (--pending_requests_ == 0 || result) {
     return_result_.Run(result);
 
     // This leaks at shutdown if the HistoryService is destroyed, but
     // the process is going to die anyway.
     delete this;
   }
 }
 
 }  // namespace browser_sync