Edit in JSFiddle

var yt = yt || {};
yt.timing = yt.timing || {};
yt.timing.tick = function (label, opt_time) {
    var timer = yt.timing['timer'] || {};
    if (opt_time) {
        timer[label] = opt_time;
    } else {
        timer[label] = new Date().getTime();
    }
    yt.timing['timer'] = timer;
};
yt.timing.info = function (label, value) {
    var info_args = yt.timing['info_args'] || {};
    info_args[label] = value;
    yt.timing['info_args'] = info_args;
};
yt.timing.info('e', "923111,916616,922401,920704,912806,927201,925706,928001,922403,913546,913556,920201,911116,901451");
if (document.webkitVisibilityState == 'prerender') {
    document.addEventListener('webkitvisibilitychange', function () {
        yt.timing.tick('start');

    }, false);
}
yt.timing.tick('start');
yt.timing.info('li', '1');
try {
    yt.timing['srt'] = window.gtbExternal && window.gtbExternal.pageT() || window.external && window.external.pageT;
} catch (e) {
}
if (window.chrome && window.chrome.csi) {
    yt.timing['srt'] = Math.floor(window.chrome.csi().pageT);
}
if (window.msPerformance && window.msPerformance.timing) {
    yt.timing['srt'] = window.msPerformance.timing.responseStart - window.msPerformance.timing.navigationStart;
}