Modernizr.addTest('fullscreen',function(){
     for(var i = 0; i < Modernizr._domPrefixes.length; i++) {
        if( document[Modernizr._domPrefixes[i].toLowerCase() + 'CancelFullScreen'])
            return true;
     }
     return !!document['cancelFullScreen'] || false;
});

// http://developer.apple.com/library/safari/documentation/AudioVideo/Conceptual/Using_HTML5_Audio_Video/ControllingMediaWithJavaScript/ControllingMediaWithJavaScript.html#//apple_ref/doc/uid/TP40009523-CH3-SW20
// https://developer.mozilla.org/en/API/Fullscreen