[Sync] Adding storage key concept for ModelTypeServices.

components/sync_driver/device_info_service.h

Index: components/sync_driver/device_info_service.h
diff --git a/components/sync_driver/device_info_service.h b/components/sync_driver/device_info_service.h
index 2e6103fe68e1af6368e4ad933ba4c8890c76913e..5f416a6ae30ea9e91536ea85ca35d503c9cb7869 100644
--- a/components/sync_driver/device_info_service.h
+++ b/components/sync_driver/device_info_service.h
@@ -62,9 +62,10 @@ class DeviceInfoService : public syncer_v2::ModelTypeService,
   syncer::SyncError ApplySyncChanges(
       std::unique_ptr<syncer_v2::MetadataChangeList> metadata_change_list,
       syncer_v2::EntityChangeList entity_changes) override;
-  void GetData(ClientTagList client_tags, DataCallback callback) override;
+  void GetData(StorageKeyList storage_keys, DataCallback callback) override;
   void GetAllData(DataCallback callback) override;
   std::string GetClientTag(const syncer_v2::EntityData& entity_data) override;
+  std::string GetStorageKey(const syncer_v2::EntityData& entity_data) override;
   void OnChangeProcessorSet() override;
 
   // DeviceInfoTracker implementation.