      this._manager.trackBackdrop();
        if (this.withBackdrop) {
          this.backdropElement.prepare();
          // Give time to be added to document.
          this.async(function(){
            this.backdropElement.open();
          }, 1);
        } else {
          this.backdropElement.close();
        }
      }
    },

    /**
     * tasks which must occur before opening; e.g. making the element visible.
     * @protected
     */
    _prepareRenderOpened: function() {

      // Needed to calcul