[USS] Add function for update storage key for processor

components/sync/model/fake_model_type_change_processor.h

Index: components/sync/model/fake_model_type_change_processor.h
diff --git a/components/sync/model/fake_model_type_change_processor.h b/components/sync/model/fake_model_type_change_processor.h
index 732f9e61133d5424291b77f6a5d8374c13097ac2..42886611dd4e32e14cea1199af5170aed878adbd 100644
--- a/components/sync/model/fake_model_type_change_processor.h
+++ b/components/sync/model/fake_model_type_change_processor.h
@@ -33,6 +33,9 @@ class FakeModelTypeChangeProcessor : public ModelTypeChangeProcessor {
            MetadataChangeList* metadata_change_list) override;
   void Delete(const std::string& client_tag,
               MetadataChangeList* metadata_change_list) override;
+  void UpdateStorageKey(const std::string& old_storage_key,
+                        const std::string& new_storage_key,
+                        MetadataChangeList* metadata_change_list) override;
   void ModelReadyToSync(std::unique_ptr<MetadataBatch> batch) override;
   void OnSyncStarting(const ModelErrorHandler& error_handler,
                       const StartCallback& callback) override;