docs: public static Scriptable getBuiltinPrototype(Scriptable scope,
                                                   Builtins type) {
          // must be called with top level scope
          assert scope.getParentScope() == null;
          if (scope instanceof TopLevel) {
              Scriptable result = ((TopLevel)scope)
                      .getBuiltinPrototype(type);
              if (result != null) {
                  return result;
              }
          }
          // fall back to normal prototype lookup
          return ScriptableObject.getClassPrototype(scope, type.name());
      }