How long the browser is given to restore the page after the learner leaves
fullscreen, before the waiting dialog opens.
Remarks
fullscreenchange fires when the exit begins, so a dialog opened on it
spends its entrance behind the browser's own transition and looks like it had
been there all along. There is no event for "the exit finished", which is why
this is a constant.
How long the browser is given to restore the page after the learner leaves fullscreen, before the waiting dialog opens.