unfiled → selector
undecided → low
new → closed
Thanks for replying back with a test case. Further information on compareDocumentPosition (which is used for one of the tests performed by .contains()) can be found here: https://developer.mozilla.org/en/DOM/Node.compareDocumentPosition.
Also, the documentation for jQuery.contains() says:
>jQuery.contains( container, contained )\\\\
>container The DOM element that may contain the other element.\\\\
>contained The DOM node that may be contained by the other element.
As you correctly point out, window is not a DOM node and so an exception here would be raised.
As for this coming in as an enhancement, I'm having a hard time trying to visualize a real-world scenario where needing to test that a document belongs to a particular window would be needed (to the extent that a lot of people would use this feature if included in core).
I believe this is an enhancement that *should* be possible to turn into a plugin outside of core itself. I'd recommend trying to do this and seeing just how well it's received or widely it's used. If you can prove demand, we'd certainly be open to considering it.