Helper function to install a getter/setter accessor property.
function InstallGetterSetter(object, name, getter, setter, attributes) {
  %CheckIsBootstrapping();
  if (IS_UNDEFINED(attributes)) attributes = DONT_ENUM;
  SetFunctionName(getter, name, "get");
  SetFunctionName(setter, name, "set");
  %FunctionRemovePrototype(getter);
  %FunctionRemovePrototype(setter);
  %DefineAccessorPropertyUnchecked(object, name, getter, setter, DONT_ENUM);
  %SetNativeFlag(getter);
  %SetNativeFlag(setter);
}