LayoutTests/fast/animation/pseudo-element-style-adjuster.html

<style>
@keyframes anim {
  from { color:red; }
  to { color:green; }
}
.flex { display:flex; }
.host::before { display:inline-block; content:'On the same'; }
.host::after { display:inline-block; content:'line'; animation-duration:0s; animation-name:anim; animation-fill-mode:forwards; }
</style>
<div class=flex>
<div class=host> </div>
</div>