nsresult IndexOf(nsIContent* aPossibleChild, PRInt32& aResult) const { aResult = -1; return NS_OK; }
nsGenericDOMDataNode::IndexOf(nsIContent* aPossibleChild) const { return -1; }
  nsresult IndexOf(nsIContent* aPossibleChild, PRInt32& aResult) const {    aResult = -1;    return NS_OK;  }