function isHost(obj) {
  var str = {}.toString.call(obj);

  switch (str) {
    case '[object File]':
    case '[object Blob]':
    case '[object FormData]':
      return true;
    default:
      return false;
  }
}
Check if `obj` is a host object,
we don't want to serialize these :)

TODO: future proof, move to compoent land

@param {Object} obj
@return {Boolean}
@api private