e}
     */
    get _focusNode() {
      return this._focusedChild || Polymer.dom(this).querySelector('[autofocus]') || this;
    },

    /**
     * Array of nodes that can receive focus (overlay included), ordered by `tabindex`.
     * This is used to retrieve which is the first and last focusable nodes in order
     * to wrap the focus for overlays `with-backdrop`.
     *
     * If you know what is your content (specifically the first and last focusable children),
     * you can override this method to ret