Remove unused include in sequenced_worker_pool.h

ios/web/public/web_thread.h

 // 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.
 
 #ifndef IOS_WEB_PUBLIC_WEB_THREAD_H_
 #define IOS_WEB_PUBLIC_WEB_THREAD_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
 #include "base/task_runner_util.h"
 
 namespace base {
 class MessageLoop;
 class SequencedWorkerPool;
 }
 
 namespace tracked_objects {
 class Location;
 }
@@ skipping 242 matching lines @@
  private:
   friend class WebThreadImpl;
 
   WebThread() {}
   DISALLOW_COPY_AND_ASSIGN(WebThread);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_WEB_THREAD_H_