return it->QueryInterface(kIDocumentViewerIID, (void**) aResult);
return it->QueryInterface(NS_GET_IID(nsIDocumentViewer), (void**) aResult);
NS_NewDocumentViewer(nsIDocumentViewer** aResult){  NS_PRECONDITION(aResult, "null OUT ptr");  if (!aResult) {    return NS_ERROR_NULL_POINTER;  }  DocumentViewerImpl* it = new DocumentViewerImpl();  if (nsnull == it) {    *aResult = nsnull;    return NS_ERROR_OUT_OF_MEMORY;  }  return it->QueryInterface(kIDocumentViewerIID, (void**) aResult);}