Import upstream changes (9e40dbdcd72f1415aafc21938e203fa2b4fa6a3c)
Import upstream changes (9e40dbdcd72f1415aafc21938e203fa2b4fa6a3c)

PolymerLabs/lit-element-starter-js,lit/lit-element-starter-js,PolymerLabs/lit-element-starter-js,lit/lit-element-starter-js