I actually keep a Chrome Snippet for such cases.

    var getFont = function(url) {
        var link = document.createElement('link');
        link.rel='stylesheet';
        link.type='text/css';
        link.href = url;
        document.head.appendChild(link);
    }

    getFont('https://fonts.googleapis.com/css?family=Open+Sans|Roboto')

    var sheet = (function() {
        var style = document.createElement('style');
        document.head.appendChild(style);
        return style.sheet;
    })();

    sheet.insertRule('body { font: 400 16px/24px Roboto,sans-serif!important; -webkit-font-smoothing: antialiased; }', 0);