if (nsnull != mSheet) { return mSheet->QueryInterface(NS_GET_IID(nsIDOMCSSStyleSheet), (void**)aSheet);
if (mSheet) { return CallQueryInterface(mSheet, aSheet);
CSSStyleRuleImpl::GetParentStyleSheet(nsIDOMCSSStyleSheet** aSheet){  if (nsnull != mSheet) {    return mSheet->QueryInterface(NS_GET_IID(nsIDOMCSSStyleSheet), (void**)aSheet);  }  *aSheet = nsnull;  return NS_OK;}