rv = NS_NewURI(&gURI, NS_LITERAL_CSTRING("about:xul-master-placeholder"), nsnull);
rv = NS_NewURI(&gURI, "about:xul-master-placeholder", nsnull);
PlaceHolderRequest::PlaceHolderRequest(){    if (gRefCnt++ == 0) {        nsresult rv;        rv = NS_NewURI(&gURI, NS_LITERAL_CSTRING("about:xul-master-placeholder"), nsnull);        NS_ASSERTION(NS_SUCCEEDED(rv), "unable to create about:xul-master-placeholder");    }}