Custom Google Analytics Content Experiment
// Note: this will throw an error if it doesn't run before _gaq's _trackPageView
$.getScript('//www.google-analytics.com/cx/api.js?experiment=EXPERIMENT_ID', function(){
var variation_classes = ['mobile-search--show', 'mobile-search--hide'],
variant_class = variation_classes[cxApi.chooseVariation()];
$('body').addClass(variant_class);
});