LayoutTests/compositing/contents-opaque/opaque-with-clip-path.html

<style>
#parent {
    width: 500px;
	height: 200px;
	margin: 20px;
	background: blue;
	border: solid red 20px;
	-webkit-clip-path: inset(0 20% 0 50px) border-box;
}

.composited {
  -webkit-transform: translateZ(0);
}
</style>
<div id="parent" class="composited"></div>