haikuwebkit/LayoutTests/animations/keyframe-rem-unit.html

<!DOCTYPE html>
<style>
div {
  animation: anim 16ms linear forwards;
}
@keyframes anim {
    0% {
        font-size: 6rem;
    }
    100% {
        font-size: 6rem;
    }
}
</style>
<div>Hello world!</div>