setDelay(delay) {
    // NOTE: This is no longer used internally, but is exported.
    // So we cannot remove it without deprecating it and waiting one release
    // cycle, or else we risk breaking custom manifest parsers.
    goog.asserts.assert(delay >= 0, 'delay must be >= 0');
    this.presentationDelay_ = delay;
  }
Sets the presentation delay in seconds.

@param {number} delay
@export