[whatwg] optgroup element used for selection

[timeless]

Personally i'd rather that a UA be able to choose to do this on its
own. I don't think it requires a change to the specification.

you're talking more about a behavior (clicking X triggers Y and Z)
than how the web page sees what happened (either way it only sees
triggers on Y and Z).

I've actually been poking this widget a couple of ways recently and
things like this have come to mind.