if(typeof window.performance === "object") {
  if(window.performance.now) {
    module.exports = function() { return window.performance.now() }
  } else if(window.performance.webktiNow) {
    module.exports = function() { return window.performance.webkitNow() }
  }
} else if(Date.now) {
  module.exports = Date.now
} else {
  module.exports = function() { return (new Date()).getTime() }
}
if(typeof window.performance === "object") {
  if(window.performance.now) {
    module.exports = function() { return window.performance.now() }
  } else if(window.performance.webkitNow) {
    module.exports = function() { return window.performance.webkitNow() }
  }
} else if(Date.now) {
  module.exports = Date.now
} else {
  module.exports = function() { return (new Date()).getTime() }
}

Update hrtime-polyfill.js