<style>
.composited {
    will-change: transform;
}
.clipper {
    width: 200px;
    height: 200px;
    border-radius: 40px;
    overflow: hidden;
}
.inner {
  width: 80px;
  height: 400px;
  background-color: #080;
  position: relative;
  will-change: transform;
}
</style>

<div class="composited">
  <div class="clipper">
    <div class="inner">
    </div>
  </div>
</div>