code: function PDFPresentationMode_setSwitchInProgress() {
              if (this.switchInProgress) {
                clearTimeout(this.switchInProgress);
              }
              this.switchInProgress = setTimeout(function switchInProgressTimeout() {
                this._removeFullscreenChangeListeners();
                delete this.switchInProgress;
                this._notifyStateChange();
              }.bind(this), DELAY_BEFORE_RESETTING_SWITCH_IN_PROGRESS);
            }
docs: Used to initialize a timeout when requesting Presentation Mode,
  i.e. when the browser is requested to enter fullscreen mode.
  This timeout is used to prevent the current page from being scrolled
  partially, or completely, out of view when entering Presentation Mode.
  NOTE: This issue seems limited to certain zoom levels (e.g. page-width).
  @private