This selector makes me *so* sad. Hard to believe we can’t make it smaller. :-(

@pivanov, is it necessary to check both `[disabled="true"]` and `[disabled]`? Wouldn’t the latter be enough?

@eeejay, do we track these disabled / aria-disabled attributes for accessibility reasons in Gaia already? I believe it makes no sense to check `aria-disabled` on buttons and `disabled` on links, right?