chromium/third_party/blink/web_tests/external/wpt/css/css-transforms/preserve3d-and-flattening-z-order-007.html

<!DOCTYPE HTML>
<meta charset="utf-8">
<title>CSS Test (Transforms): Flattening at the leafward edges of a preserve-3d scene</title>
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1255544">
<link rel="author" title="L. David Baron" href="https://dbaron.org/">
<link rel="author" title="Google" href="http://www.google.com/">
<link rel="help" href="http://www.w3.org/TR/css-transforms-2/#3d-transform-rendering">
<meta name="assert" content="Elements are drawn in the correct z-order.">
<link rel="match" href="preserve3d-and-flattening-002-ref.html">

<style>
body {
  margin: 0;
}
div, span {
  height: 100px;
  width: 100px;
  background: red;
}
span {
  display: inline-block;
  vertical-align: top;
}
div:not(:first-child):not(.outer) {
  /* put everything at the same position without using absolute positioning */
  margin-top: -100px;
}
.outer, .sibling {
  transform-style: preserve-3d;
}
.outer {
  background: gray;
}
.flattener {
  /* adding position:relative or a transform changes things */
  background: fuchsia;
}
.sibling {
  background: blue;
  transform: translate3d(25px, 50px, -20px);
}
.child {
  background: silver;
  transform: translate3d(50px, 0, 10px);
  will-change: transform;
}
</style>

<div class="outer">
  <div class="flattener">
    <div class="child"></div>
  </div>
  <div class="sibling"></div>
</div>