HTML5Demos: Fullscreen demo needs updating to latest syntax and prefixes

[dstorey]

URL: http://html5-demos.appspot.com/static/fullscreen.html Repo: https://github.com/ebidel/html5demos/blob/master/html5-demos.appspot.com/static/fullscreen.html

Issues:

• Multi-column only uses webkit/moz prefixes, without unprefixed
• No unprefixed :fullscreen or :-ms-fullscreen
• No unprefixed gradients
• Old flexbox and only webkit/moz prefixes
• Missing prefixes and latest syntax for fullscreen API.
• Some strange prefix/unprefix ordering