[Sync] Introduce AttachmentStoreForSync class

sync/api/fake_syncable_service.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 SYNC_API_FAKE_SYNCABLE_SERVICE_H_
 #define SYNC_API_FAKE_SYNCABLE_SERVICE_H_
 
 #include "sync/api/syncable_service.h"
 
 namespace syncer {
@@ skipping 25 matching lines @@
   // SyncableService implementation.
   SyncMergeResult MergeDataAndStartSyncing(
       ModelType type,
       const SyncDataList& initial_sync_data,
       scoped_ptr<SyncChangeProcessor> sync_processor,
       scoped_ptr<SyncErrorFactory> sync_error_factory) override;
   void StopSyncing(ModelType type) override;
   SyncDataList GetAllSyncData(ModelType type) const override;
   SyncError ProcessSyncChanges(const tracked_objects::Location& from_here,
                                const SyncChangeList& change_list) override;
-  scoped_ptr<AttachmentStore> GetAttachmentStoreForSync() override;
+  scoped_ptr<AttachmentStoreForSync> GetAttachmentStoreForSync() override;
   void SetAttachmentService(
       scoped_ptr<AttachmentService> attachment_service) override;
 
  private:
   scoped_ptr<SyncChangeProcessor> sync_processor_;
   SyncError merge_data_and_start_syncing_error_;
   SyncError process_sync_changes_error_;
   bool syncing_;
   ModelType type_;
   scoped_ptr<AttachmentStore> attachment_store_;
   scoped_ptr<AttachmentService> attachment_service_;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_API_FAKE_SYNCABLE_SERVICE_H_