1 When an optgroup element became 'disabled' or not-'disabled', distribution should happen.
3 Since an optgroup element does not create a renderer, we cannot check this using reftest.
5 PASS nodes1.length is 1
6 PASS nodes1.item(0).innerHTML is "optgroup 2"
7 PASS nodes2.length is 1
8 PASS nodes2.item(0).innerHTML is "optgroup 3"
9 PASS successfullyParsed is true