constructor(asyncIteratorReader, preventCancel) {
    /** @package @const {!ReadableStreamDefaultReader<T>} */
    this.asyncIteratorReader = asyncIteratorReader;

    /** @package @const {boolean} */
    this.preventCancel = preventCancel;
  }
@param {!ReadableStreamDefaultReader<T>} asyncIteratorReader
@param {boolean} preventCancel
@package