in static/assets/js/modernizr.js [538:545]
tests['hsla'] = function() {
// Same as rgba(), in fact, browsers re-map hsla() to rgba() internally,
// except IE9 who retains it as hsla
setCss('background-color:hsla(120,40%,100%,.5)');
return contains(mStyle.backgroundColor, 'rgba') || contains(mStyle.backgroundColor, 'hsla');
};