Using document.elementFromPoint() returns elements 180deg flipped in VR.

[caseyyee]

Visible in this example:
http://mozvr.github.io/cursor-target-test

[caseyyee]

The issue is not that the axis is flipped, but that the hittest is returning elements behind the user.

[caseyyee]

Tracking the issue in bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1171756