iron-overlay-canceled', event, {cancelable: true});
      if (cancelEvent.defaultPrevented) {
        return;
      }

      this._setCanceled(true);
      this.opened = false;
    },

    /**
     * Invalidates the cached tabbable nodes. To be called when any of the focusable
     * content changes (e.g. a button is disabled).
     */
    invalidateTabbables: function() {
      this.__firstFocusableNode = this.__lastFocusableNode = null;
    },

    _ensureSetup: function() {
      if (this._overlaySetup) 