Make GetBestPageForOnlineURL async

components/offline_pages/stub_offline_page_model.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_OFFLINE_PAGES_STUB_OFFLINE_PAGE_MODEL_H_
 #define COMPONENTS_OFFLINE_PAGES_STUB_OFFLINE_PAGE_MODEL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 41 matching lines @@
   const OfflinePageItem* MaybeGetPageByOfflineId(
       int64_t offline_id) const override;
   void GetPageByOfflineURL(
       const GURL& offline_url,
       const SingleOfflinePageItemCallback& callback) override;
   const OfflinePageItem* MaybeGetPageByOfflineURL(
       const GURL& offline_url) const override;
   void GetPagesByOnlineURL(
       const GURL& online_url,
       const MultipleOfflinePageItemCallback& callback) override;
-  void GetBestPageForOnlineURL(
-      const GURL& online_url,
-      const SingleOfflinePageItemCallback callback) override;
   const OfflinePageItem* MaybeGetBestPageForOnlineURL(
       const GURL& online_url) const override;
   void CheckMetadataConsistency() override;
   void ExpirePages(const std::vector<int64_t>& offline_ids,
                    const base::Time& expiration_time,
                    const base::Callback<void(bool)>& callback) override;
   ClientPolicyController* GetPolicyController() override;
   bool is_loaded() const override;
   OfflineEventLogger* GetLogger() override;
 
  private:
   std::vector<int64_t> offline_ids_;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_STUB_OFFLINE_PAGE_MODEL_H_