Fallout from #2043: https://github.com/jquery/jquery/pull/2043/files#r23981494

Since all supported browsers have getBoundingClientRect, there's no reason not to just call the method right away, letting an exception throw if input is in fact not a DOM element.

The "object without getBoundingClientRect" test will have to go as well.