if (aIndex < 0) { return NS_ERROR_INVALID_ARG;  } else if (0 == aIndex) { *aListName = nsLayoutAtoms::fixedList; NS_ADDREF(*aListName);
if (0 == aIndex) { return mFixedContainer.GetChildListName();
ViewportFrame::GetAdditionalChildListName(PRInt32   aIndex,                                          nsIAtom** aListName) const{  NS_PRECONDITION(nsnull != aListName, "null OUT parameter pointer");  *aListName = nsnull;  if (aIndex < 0) {    return NS_ERROR_INVALID_ARG;  } else if (0 == aIndex) {    *aListName = nsLayoutAtoms::fixedList;    NS_ADDREF(*aListName);  }  return NS_OK;}