abort () {
    // 1. If this's state is "empty" or if this's state is
    //    "done" set this's result to null and terminate
    //    this algorithm.
    if (this[kState] === 'empty' || this[kState] === 'done') {
      this[kResult] = null
      return
    }

    // 2. If this's state is "loading" set this's state to
    //    "done" and set this's result to null.
    if (this[kState] === 'loading') {
      this[kState] = 'done'
      this[kResult] = null
    }

    // 3. If there are any tasks from this on the file reading
    //    task source in an affiliated task queue, then remove
    //    those tasks from that task queue.
    this[kAborted] = true

    // 4. Terminate the algorithm for the read method being processed.
    // TODO

    // 5. Fire a progress event called abort at this.
    fireAProgressEvent('abort', this)

    // 6. If this's state is not "loading", fire a progress
    //    event called loadend at this.
    if (this[kState] !== 'loading') {
      fireAProgressEvent('loadend', this)
    }
  }
@see https://w3c.github.io/FileAPI/#dom-filereader-readystate