chromium/third_party/blink/web_tests/transforms/transform-positioned-container.html

<!DOCTYPE html>
<style>
#old-container {
    position: relative;
}

#positioned-child {
    position: absolute;
}

#descendant-needing-layout {
    display: none;
    width: 100px;
    height: 100px;
    background-color: green;
}
</style>
This test verifies adding transform to a block correctly update container status.
<div id="old-container">
    <div id="new-container">
        <div id="positioned-child">
            <div id="descendant-needing-layout">
            </div>
        </div>
    </div>
</div>
<script>
function runTest() {
    document.body.offsetTop;

    var newContainer = document.getElementById("new-container");
    var descendantNeedingLayout = document.getElementById("descendant-needing-layout");

    newContainer.style.transform = "translateX(0)";
    descendantNeedingLayout.style.display = "block";
}

runTest();
</script>