[OfflinePages] Make website settings popup rely on asynchronous API

components/offline_pages/offline_page_model.h

 // Copyright 2015 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_OFFLINE_PAGE_MODEL_H_
 #define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 75 matching lines @@
                                     const ClientId& client_id) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
   using CheckPagesExistOfflineResult =
       offline_pages::CheckPagesExistOfflineResult;
   using MultipleOfflinePageItemResult =
       offline_pages::MultipleOfflinePageItemResult;
+  using SingleOfflinePageItemResult =
+      offline_pages::SingleOfflinePageItemResult;
 
   //using DeletePageCallback = offline_pages::DeletePageCallback;
   using DeletePageResult = offline_pages::DeletePageResult;
   using SavePageResult = offline_pages::SavePageResult;
 
   // Generates a new offline id
   static int64_t GenerateOfflineId();
 
   // Returns true if an offline copy can be saved for the given URL.
   static bool CanSavePage(const GURL& url);
@@ skipping 262 matching lines @@
   std::unique_ptr<OfflinePageStorageManager> storage_manager_;
 
   base::WeakPtrFactory<OfflinePageModel> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageModel);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_H_