async function getBrowserVersion(session) {
  const status = {msg: 'Getting browser version', id: 'lh:gather:getVersion'};
  log.time(status, 'verbose');
  const version = await session.sendCommand('Browser.getVersion');
  const match = version.product.match(/\/(\d+)/); // eg 'Chrome/71.0.3577.0'
  const milestone = match ? parseInt(match[1]) : 0;
  log.timeEnd(status);
  return Object.assign(version, {milestone});
}
@param {LH.Gatherer.ProtocolSession} session
@return {Promise<LH.Crdp.Browser.GetVersionResponse & {milestone: number}>}