aTooltip->SetAttr(nsnull, nsXULAtoms::label, label, PR_FALSE);
aTooltip->SetAttr(nsnull, nsXULAtoms::label, label, PR_TRUE);
SetTitletipLabel(nsITreeBoxObject* aTreeBox, nsIContent* aTooltip,                 PRInt32 aRow, nsAutoString aCol){  nsCOMPtr<nsITreeView> view;  aTreeBox->GetView(getter_AddRefs(view));  nsAutoString label;  view->GetCellText(aRow, aCol.get(), label);    aTooltip->SetAttr(nsnull, nsXULAtoms::label, label, PR_FALSE);}