See https://bugzilla.mozilla.org/show_bug.cgi?id=1735738 for reference.
);
        task.pageNum++;
        self._nextPage(task);
      });
    },
    _quit: function Driver_quit() {
      this._log("Done !");
      this.end.textContent = "Tests finished. Close this window!";
      
      var r = new XMLHttpRequest();
      r.open("POST", `/tellMeToQuit?browser=${escape(this.browser)}`, false);
      r.onreadystatechange = function (e) {
        if (r.readyState === 4) {
          window.close();
        }
      };
      r.send(null);
    },
    _info: function Driver_info(message) {
      this._send(
        "/info",
        JSON.stringify({
          browser: this.browser,
          message,
        })
      );
    },
    _log: function Driver_log(message) {