IIRC, `jsdom` only got functional CSSStyleDeclarations within the past 6 months.

> Why? So jQuery would not throw error in FF and Opera if it used in xml document? That's a weird case too, jQuery would still be broken, if it would be silent about it – how is that better?

It's better because the *rest* of jQuery still works just fine, as opposed to not existing because of a dependency failure for code that wasn't going to be used anyway. And `support` is not an optional module.