There are some unfortunate aspects of openWindow() and openWindow2() that make
this difficult. Namely, they sometimes return top-level chrome windows, and
sometimes a single content window from the top-level chrome window that they
open, depending on how they're called.
There really isn't any reason to return a BrowsingContext rather than a chrome
window in the former case, but there also really isn't a way to make the API
polymorphic in a way that would allow handling the two cases differently. So
at some point, the two cases should ideally be split into separate APIs rather
than separate special cases of a single API.
In the mean time, I've left openWindow() returning local mozIDOMWindowProxy
objects, since it isn't used by the DOM window.open() or openDialog() APIs,
and only updated openWindow2(). As a follow-up, we should remove both
openWindow() and openWindow2(), and replace them with openChromeWindow() and
openContentWindow() (or similar) methods which make it immediately clear what
type of window is being returned.
Differential Revision: https://phabricator.services.mozilla.com/D35689
7575d4eb1d