docs: public static void redefineProperty(Scriptable obj, String name,
                                          boolean isConst)
      {
          Scriptable base = getBase(obj, name);
          if (base == null)
              return;
          if (base instanceof ConstProperties) {
              ConstProperties cp = (ConstProperties)base;
  
              if (cp.isConst(name))
                  throw ScriptRuntime.typeError1("msg.const.redecl", name);
          }
          if (isConst)
              throw ScriptRuntime.typeError1("msg.var.redecl", name);
      }