This was requested for cross referencing instead of "hide all popovers
until" here:
whatwg/fullscreen#204 (comment)

This patch also fixes a bug where a null endpoint is passed to hide all
popovers until, but hide all popovers until assumes endpoint is not null
by looking for endpoint's node document. The bug is fixed by adding a
required document parameter to hide all popovers until.

These dfns need to be exported in order to be used in the fullscreen
spec: whatwg/fullscreen#204