adjustRegion_(region) {
    if (this.parentService_) {
      region.id += 'svc' + this.parentService_;
    }
    region.id += 'win' + this.windowNum_;

    region.height = this.rowCount_;
    region.width = this.colCount_;
    region.heightUnits = shaka.text.CueRegion.units.LINES;
    region.widthUnits = shaka.text.CueRegion.units.LINES;

    region.viewportAnchorX = this.horizontalAnchor_;
    region.viewportAnchorY = this.verticalAnchor_;
    // WebVTT's region viewport anchors are technically always in percentages.
    // However, we don't know the aspect ratio of the video at this point,
    // which determines how we interpret the horizontal anchor.
    // So, we expose the additional flag to reflect whether these viewport
    // anchor values can be used as is or should be converted
    // to percentages.
    region.viewportAnchorUnits = this.relativeToggle_ ?
      shaka.text.CueRegion.units.PERCENTAGE : shaka.text.CueRegion.units.LINES;

    const AnchorId = shaka.cea.Cea708Window.AnchorId;

    switch (this.anchorId_) {
      case AnchorId.UPPER_LEFT:
        region.regionAnchorX = 0;
        region.regionAnchorY = 0;
        break;
      case AnchorId.UPPER_CENTER:
        region.regionAnchorX = 50;
        region.regionAnchorY = 0;
        break;
      case AnchorId.UPPER_RIGHT:
        region.regionAnchorX = 100;
        region.regionAnchorY = 0;
        break;
      case AnchorId.MIDDLE_LEFT:
        region.regionAnchorX = 0;
        region.regionAnchorY = 50;
        break;
      case AnchorId.MIDDLE_CENTER:
        region.regionAnchorX = 50;
        region.regionAnchorY = 50;
        break;
      case AnchorId.MIDDLE_RIGHT:
        region.regionAnchorX = 100;
        region.regionAnchorY = 50;
        break;
      case AnchorId.LOWER_LEFT:
        region.regionAnchorX = 0;
        region.regionAnchorY = 100;
        break;
      case AnchorId.LOWER_CENTER:
        region.regionAnchorX = 50;
        region.regionAnchorY = 100;
        break;
      case AnchorId.LOWER_RIGHT:
        region.regionAnchorX = 100;
        region.regionAnchorY = 100;
        break;
    }
  }
Support window positioning by mapping anchor related values to CueRegion.
https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/608toVTT.html#positioning-in-cea-708
@param {shaka.text.CueRegion} region
@private