constructor(interstitial, sequenceLength, adPosition) {
    /** @private {shaka.extern.AdInterstitial} */
    this.interstitial_ = interstitial;

    /** @private {number} */
    this.sequenceLength_ = sequenceLength;

    /** @private {number} */
    this.adPosition_ = adPosition;

    /** @private {boolean} */
    this.isLinear_ = interstitial.overlay == null;
  }
@param {shaka.extern.AdInterstitial} interstitial
@param {number} sequenceLength
@param {number} adPosition