code: function TransformStreamCloseReadableInternal(transformStream) {
    assert(transformStream._errored === false);
    assert(transformStream._readableClosed === false);
  
    try {
      ReadableStreamDefaultControllerClose(transformStream._readableController);
    } catch (e) {
      assert(false);
    }
  
    transformStream._readableClosed = true;
  }
docs: Abstract operations.