Definition
Portals defines HTMLPortalElement
[Exposed=Window]
interface HTMLPortalElement : HTMLElement {
[HTMLConstructor] constructor();
[CEReactions] attribute USVString src;
[CEReactions] attribute DOMString referrerPolicy;
[NewObject] Promise<undefined> activate(optional PortalActivateOptions options = {});
undefined postMessage(any message, optional StructuredSerializeOptions options = {});
attribute EventHandler onmessage;
attribute EventHandler onmessageerror;
};