function makeRanges(start, duration, num) {
  const ranges = [];
  let currentPos = start;
  for (let i = 0; i < num; i += 1) {
    ranges.push({
      start: currentPos,
      end: currentPos + duration,
      unscaledStart: currentPos * 90000,
    });
    currentPos += duration;
  }
  return ranges;
}
Create a list of continuous time ranges
@param {number} start
@param {number} duration
@param {number} num
@return {Array<shaka.media.PresentationTimeline.TimeRange>}