squash-partial-repaint-inside-squashed-layer.html

<!DOCTYPE html>
<head>
<style>
.composited {
will-change: transform;
}

.box {
  width: 100px;
  height: 100px;
}

.behind {
  position: absolute;
  z-index: 1;
  top: 100px;
  left: 100px;
  background-color: blue;
}

.middle {
  position: absolute;
  z-index: 1;
  top: 180px;
  left: 180px;
  background-color: lime;
}

.repaintdiv {
  position: absolute;
  z-index: 1;
  top: 260px;
  left: 260px;
  width: 182px;
  height: 29px;
  background-color:red;
}

.top {
  position: absolute;
  z-index: 1;
  top: 280px;
  left: 340px;
  background-color: cyan;
}

div:hover {
  background-color: green;
  transform:translatez(0);
}

</style>
<script src="../resources/text-based-repaint.js"></script>
<script>
    function repaintTest()
    {
        document.getElementById('repaintdiv').style.background = 'salmon';
    }
    runRepaintAndPixelTest();
</script>
</head>
<body>
    <div class="composited box behind"></div>
    <div class="box middle"></div>
    <img id="repaintdiv" class="repaintdiv"></img>
    <div class="box top"></div>
</body>

chromium/third_party/blink/web_tests/paint/invalidation/compositing/squash-partial-repaint-inside-squashed-layer.html