Automated IWYU fix for TaskRunner includes.

chrome/browser/search/thumbnail_source.h

 // Copyright (c) 2012 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 CHROME_BROWSER_SEARCH_THUMBNAIL_SOURCE_H_
 #define CHROME_BROWSER_SEARCH_THUMBNAIL_SOURCE_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
 #include "components/image_fetcher/core/image_data_fetcher.h"
 #include "content/public/browser/url_data_source.h"
 
 class GURL;
 class Profile;
 
 namespace image_fetcher {
 struct RequestMetadata;
 }
 
@@ skipping 48 matching lines @@
   const bool capture_thumbnails_;
 
   image_fetcher::ImageDataFetcher image_data_fetcher_;
 
   base::WeakPtrFactory<ThumbnailSource> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ThumbnailSource);
 };
 
 #endif  // CHROME_BROWSER_SEARCH_THUMBNAIL_SOURCE_H_