components: Cleanup class/struct fwd declarations

components/previews/core/previews_opt_out_store.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_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_
 #define COMPONENTS_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/time/time.h"
 #include "components/previews/core/previews_black_list_item.h"
 #include "components/previews/core/previews_experiments.h"
 
-class GURL;
-
 namespace previews {
 
 typedef std::unordered_map<std::string, std::unique_ptr<PreviewsBlackListItem>>
     BlackListItemMap;
 
 typedef base::Callback<void(std::unique_ptr<BlackListItemMap>,
                             std::unique_ptr<PreviewsBlackListItem>)>
     LoadBlackListCallback;
 
 // PreviewsOptOutStore keeps opt out information for the previews.
@@ skipping 16 matching lines @@
   // host from the store. And runs |callback| once loading is finished.
   virtual void LoadBlackList(LoadBlackListCallback callback) = 0;
 
   // Deletes all history in the store between |begin_time| and |end_time|.
   virtual void ClearBlackList(base::Time begin_time, base::Time end_time) = 0;
 };
 
 }  // namespace previews
 
 #endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_