nsIFrame *option; for (aContainer->FirstChild(aPresContext, nsnull, &option);
for (nsIFrame* option = aContainer->GetFirstChild(nsnull);
GetMaxOptionHeight(nsIPresContext *aPresContext, nsIFrame *aContainer){  nscoord result = 0;  nsIFrame *option;  for (aContainer->FirstChild(aPresContext, nsnull, &option);       option; option = option->GetNextSibling()) {    nscoord optionHeight;    if (nsCOMPtr<nsIDOMHTMLOptGroupElement>        (do_QueryInterface(option->GetContent()))) {      // an optgroup      optionHeight = GetMaxOptionHeight(aPresContext, option);    } else {      // an option      optionHeight = option->GetSize().height;    }    if (result < optionHeight)      result = optionHeight;  }  return result;}