function isIpod() {
  // navigator.userAgentData is currently not supported on any iOS browser, so
  // rely only on navigator.userAgent.
  return util.matchUserAgent('iPod');
}
@return {boolean} Whether the platform is iPod.
TODO(user): Combine iPod/iPhone detection since they may become
indistinguishable if we begin relying on userAgentdata in iOS.