Introduce DynamicModuleOwner dom struct

components/script/dom/webidls/DynamicModuleOwner.webidl

@@ -0,0 +1,13 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+/**
+ * This is defined for [`Dynamic Module`](https://html.spec.whatwg.org/multipage/#fetch-an-import()-module-script-graph)
+ * so that we can hold a traceable owner for those dynamic modules which don't hold a owner.
+ */
+
+[NoInterfaceObject, Exposed=Window]
+interface DynamicModuleOwner {
+  readonly attribute Promise<any> promise;
+};