cancelInternal(reason) {
    this.disturbed = true;
    if (this.state === liteImpl.ReadableStream.State.CLOSED) {
      return Promise.resolve();
    }
    if (this.state === liteImpl.ReadableStream.State.ERRORED) {
      return Promise.reject(this.storedError);
    }
    this.close();
    return /** @type {!ReadableStreamDefaultController} */ (
               this.readableStreamController)
        .cancelSteps(reason)
        .then(() => {});
  }
@param {*} reason
@return {!Promise<undefined>}
@package