document.onreadystatechange = function () {
    console.log("content script was fired onreadystatechange ");


    class PageMeasurement {
        constructor(url) {

            this.url = url;
            this.date = Date.now();
            var t = window.performance.timing;
            this.pageLoadTime = (t.loadEventEnd - t.fetchStart);
            this.renderTime =  (t.loadEventEnd - t.responseEnd);

        }
    }


    if (document.readyState === 'complete') {

        console.log("document.readyState === complete")
        var page = new PageMeasurement(document.URL);
        console.log("page.renderTime", page.renderTime);

    }

}