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chromium/third_party/blink/web_tests/compositing/ancestor-painted-layer-should-appear-expected.html 

<!DOCTYPE HTML>
<style>
body {
  will-change: transform;
}
#overlapper {
  width: 400px;
  height: 400px;
  left: 200px;
  background: gray;
  position: absolute;
  will-change: transform;
}

#container {
  -webkit-perspective: 1400px;
  will-change: transform;
  position: absolute;
  width: 180px;
  height: 180px;
  background: papayawhip;
}

#composited {
  width: 100px;
  height: 100px;
  background: green;
  position: absolute;
  transform: translateZ(10px);
}

#squashed {
  position: absolute;
  left: 200px;
  width: 50px;
  height: 50px;
  background: blue;
}
</style>
<div id="overlapper"></div>
<div id="container">
  <div id="composited"></div>
</div>
<div id="squashed"></div>