The unprefixed fullscreen functions are incorrect
requestFullScreen() and cancelFullScreen() are used. Per http://fullscreen.spec.whatwg.org the correct names are requestFullscreen() and exitFullscreen().
The unprefixed fullscreenchange event isn't used at all.
Finally, there are _isMobile code paths that are WebKit-only.
Taken together, these things make it harder for browsers to get rid of the prefixed APIs.