[whatwg] Fullscreen revision I

[Jeremy Apthorp]

Another thing: I've heard from developers that it would be useful to allow
popup windows to open in fullscreen mode. For example, in Google Docs
presentations, the 'start presentation' button should open a new window in
fullscreen, so that users can use the editor in the main Chrome window and
see the presentation in a separate (fullscreen) window.

I propose that window.open(url, name, "fullscreen=yes") should present the
given url as fullscreen in a new window. Exiting fullscreen in that window
(via cancelFullScreen or user action) should restore the window (if the
author wants it to close, they can call window.close() on the
fullscreenchange event).

Of course, the request should only succeed if the UA is processing a user
gesture.