Mine

evaluate_js (EphyEmbed *embed, EphyEmbedEvent *event, const char *script)
{
	nsresult rv; 	

	nsCOMPtr<nsIDOMEvent> ev;
	ev = static_cast<nsIDOMEvent*>(ephy_embed_event_get_dom_event (event));
	NS_ENSURE_TRUE (ev, FALSE);

	nsCOMPtr<nsIDOMNSEvent> nsEvent (do_QueryInterface (ev));
	NS_ENSURE_TRUE (nsEvent, FALSE);

	nsCOMPtr<nsIDOMEventTarget> evTarget;
	nsEvent->GetExplicitOriginalTarget (getter_AddRefs (evTarget));
	NS_ENSURE_TRUE (evTarget, FALSE);

	nsCOMPtr<nsIDOMDocument> doc (do_QueryInterface (evTarget));
	NS_ENSURE_TRUE (doc, FALSE);