magento-test/app/code/Magento/Ui/view/base/web/templates/area.html

<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<if args="wasActivated">
    <div each="elems" visible="active" attr="'data-area-active': active" render=""></div>
</if>