Revert of Remove header dependencies from sequence_checker.h to sequenced_worker_pool.h

components/ntp_tiles/popular_sites_impl.h

 // Copyright 2016 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 COMPONENTS_NTP_TILES_POPULAR_SITES_IMPL_H_
 #define COMPONENTS_NTP_TILES_POPULAR_SITES_IMPL_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "components/ntp_tiles/popular_sites.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "url/gurl.h"
 
 namespace base {
-class TaskRunner;
-class SequencedWorkerPool;
 class Value;
 }
 
 namespace net {
 class URLRequestContextGetter;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
@@ skipping 70 matching lines @@
   GURL pending_url_;
 
   base::WeakPtrFactory<PopularSitesImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PopularSitesImpl);
 };
 
 }  // namespace ntp_tiles
 
 #endif  // COMPONENTS_NTP_TILES_POPULAR_SITES_IMPL_H_