As currently specified in HTML 5's section 6.2.1, WebKit should support the RemoteEventTarget interface for all classes which implement the EventTarget interface. This could probably be achieved by simply implementing the functionality in the EventTargetNode class, since all other classes which implement EventTarget seem to inherit from EventTargetNode.
RemoteEventTarget interface has been removed from the HTML5 draft; see http://html5.org/tools/web-apps-tracker?from=2869&to=2870 Spec now has an EventSource object: http://www.whatwg.org/specs/web-apps/current-work/#eventsource
INVALID per comment 1.