code: private boolean isUnextendableNativeClass(NodeTraversal t, String className) {
      // This list originally taken from the list of built-in objects at
      // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference
      // as of 2016-10-22.
      // - Intl.* classes were left out, because it doesn't seem worth the extra effort
      //   of handling the qualified name.
      // - Deprecated and experimental classes were left out.
      switch (className) {
        case "Array":
        case "ArrayBuffer":
        case "Boolean":
        case "DataView":
        case "Date":
        case "Float32Array":
        case "Function":
        case "Generator":
        case "GeneratorFunction":
        case "Int16Array":
        case "Int32Array":
        case "Int8Array":
        case "InternalError":
        case "Map":
        case "Number":
        case "Promise":
        case "Proxy":
        case "RegExp":
        case "Set":
        case "String":
        case "Symbol":
        case "TypedArray":
        case "Uint16Array":
        case "Uint32Array":
        case "Uint8Array":
        case "Uint8ClampedArray":
        case "WeakMap":
        case "WeakSet":
          return !isDefinedInSources(t, className);
        default:
          return false;
      }
    }
docs: Is the given class a native class for which we cannot properly transpile extension?
  @param t
  @param className