code: function getStreamStream (readable, file) {
    return () => {
      const counter = new stream.Transform()
      counter._transform = function (buf, enc, done) {
        file.length += buf.length
        this.push(buf)
        done()
      }
      readable.pipe(counter)
      return counter
    }
  }
docs: Convert a readable stream to a lazy readable stream. Adds instrumentation to track
  the number of bytes in the stream and set `file.length`.
  
  @param  {Stream} stream
  @param  {Object} file
  @return {function}