should-not-repaint-composited-opacity.html

<!DOCTYPE html>
<style>
#composited-box {
    will-change: transform;
    width: 100px;
    height: 100px;
    background: green;
    opacity: 0.8;
}
</style>
<script src="../resources/text-based-repaint.js"></script>
<script>
function repaintTest() {
    document.getElementById('composited-box').style.opacity = 0.5;
}
window.onload = runRepaintTest;
</script>
<div id="composited-box"></div>

chromium/third_party/blink/web_tests/paint/invalidation/compositing/should-not-repaint-composited-opacity.html