Automated IWYU fix for TaskRunner includes.

chrome/renderer/media/cast_threads.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.
 
 // Manages threads used by Cast Streaming Extensions API. There is a
 // singleton object of this class in the renderer.
 //
 // There are two threads owned by this class:
 // 1. Audio encode thread.
 // 2. Video encode thread.
 // These two threads are started this object is created.
 
 #ifndef CHROME_RENDERER_MEDIA_CAST_THREADS_H_
 #define CHROME_RENDERER_MEDIA_CAST_THREADS_H_
 
 #include "base/lazy_instance.h"
 #include "base/macros.h"
+#include "base/single_thread_task_runner.h"
 #include "base/threading/thread.h"
 
 class CastThreads {
  public:
   scoped_refptr<base::SingleThreadTaskRunner> GetAudioEncodeTaskRunner();
   scoped_refptr<base::SingleThreadTaskRunner> GetVideoEncodeTaskRunner();
 
  private:
   friend struct base::LazyInstanceTraitsBase<CastThreads>;
 
   CastThreads();
 
   base::Thread audio_encode_thread_;
   base::Thread video_encode_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(CastThreads);
 };
 
 #endif  // CHROME_RENDERER_MEDIA_CAST_THREADS_H_