[ServiceWorker] Add missing method to Cache.idl.

Source/modules/serviceworkers/Cache.idl

 // Copyright 2014 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.
 
 // See https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#cache
 
 // FIXME: Blink doesn't support dictionary definitions. For now, we can use the
 // Dictionary interface. See http://crbug.com/321462
 
 // dictionary QueryParams {
@@ skipping 15 matching lines @@
   // [CallWith=ScriptState] Promise match((Request or ScalarValueString) request, optional Dictionary queryParams);
   [CallWith=ScriptState] Promise match(Request request, optional Dictionary queryParams);
   [CallWith=ScriptState] Promise match(ScalarValueString request, optional Dictionary queryParams);
 
   // [CallWith=ScriptState] Promise matchAll((Request or ScalarValueString) request, optional Dictionary queryParams);
   [CallWith=ScriptState] Promise matchAll(Request request, optional Dictionary queryParams);
   [CallWith=ScriptState] Promise matchAll(ScalarValueString request, optional Dictionary queryParams);
 
   // [CallWith=ScriptState] Promise add((Request or ScalarValueString) request);
   [CallWith=ScriptState] Promise add(Request request);
+  [CallWith=ScriptState] Promise add(ScalarValueString request);
 
   // FIXME: The lack of union type support together with the sequence mean we can't use overrides here, instead
   // bind a generic type.
   // [CallWith=ScriptState] Promise addAll(sequence<Request or ScalarValueString> requests);
   [CallWith=ScriptState] Promise addAll(sequence<any> requests);
 
   // [CallWith=ScriptState] Promise put((Request or ScalarValueString) request, Response response);
   [CallWith=ScriptState] Promise put(Request request, Response response);
   [CallWith=ScriptState] Promise put(ScalarValueString request, Response response);
 
   // [CallWith=ScriptState] Promise delete((Request or ScalarValueString) request, optional Dictionary queryParams);
   [CallWith=ScriptState, ImplementedAs=deleteFunction] Promise delete(Request request, optional Dictionary queryParams);
   [CallWith=ScriptState, ImplementedAs=deleteFunction] Promise delete(ScalarValueString request, optional Dictionary queryParams);
 
   // [CallWith=ScriptState] Promise keys(optional (Request or ScalarValueString) request, optional Dictionary queryParams);
   [CallWith=ScriptState] Promise keys(optional Request request, optional Dictionary queryParams);
   [CallWith=ScriptState] Promise keys(ScalarValueString request, optional Dictionary queryParams);
 };