Value url(JSObject *obj) {
  MOZ_ASSERT(is_instance(obj));
  Value val = JS::GetReservedSlot(obj, Slots::URL);
  MOZ_ASSERT(val.isString());
  return val;
}
Value url(JSObject *obj) {
  MOZ_ASSERT(is_instance(obj));
  Value val = JS::GetReservedSlot(obj, Slots::URL);
  MOZ_ASSERT(val.isString());
  return val;
}