Maybe the is="" attribute gets you partway there? <ul is="label-list"> <li is="list-item">foo</li> </ul> EDIT: google's documentation: https:/

Maybe the is="" attribute gets you partway there? <ul is="label-list"> <li is="list-item">foo</li> </ul> EDIT: google's documentation: https://developers.google.com/web/fundamentals/web-components/customelements#extendhtml https://developers.google.com/web/fundamentals/web-component...