{
        return;
      }
      this._overlaySetup = true;
      this.style.outline = 'none';
      this.style.display = 'none';
    },

    /**
     * Called when `opened` changes.
     * @param {boolean=} opened
     * @protected
     */
    _openedChanged: function(opened) {
      if (opened) {
        this.removeAttribute('aria-hidden');
      } else {
        this.setAttribute('aria-hidden', 'true');
      }

      // Defer any animation-related code on attached
      // (_openedChanged gets called aga