toOffscreenTabMediaConstraints_() {
    mr.Assertions.assert(
        this.presentationId, 'Missing offscreen capture presentation id');
    const constraints = this.toTabMediaConstraints_();
    constraints['presentationId'] = this.presentationId;
    return constraints;
  }
/**
   * @return {!MediaConstraints} Media constraints for use with offscreen
   * capture APIs.
   * @private
   */
@return {!MediaConstraints} Media constraints for use with offscreen
capture APIs.
@private
@return { !MediaConstraints } Media constraints for use with offscreen capture APIs . @private
toOffscreenTabMediaConstraints_() {
    mr.Assertions.assert(
        this.presentationId, 'Missing offscreen capture presentation id');
    const constraints = this.toTabMediaConstraints_();
    constraints['presentationId'] = this.presentationId;
    return constraints;
  }
toOffscreenTabMediaConstraints_ ( ) { mr . Assertions . assert ( this . presentationId , 'Missing offscreen capture presentation id' ) ; const constraints = this . toTabMediaConstraints_ ( ) ; constraints [ 'presentationId' ] = this . presentationId ; return constraints ; }
@return {!MediaConstraints} Media constraints for use with offscreen
 capture APIs.
@return { !MediaConstraints } Media constraints for use with offscreen capture APIs .