Codebase Browser
chromium
Go to App

chromium/third_party/blink/web_tests/fast/multicol/dynamic/add-will-change-transform.html 

<!DOCTYPE html>
<style>
.multicol {
    width: 60px;
    columns: 20px;
    column-gap: 0;
    column-fill: auto;
    height: 60px;
}
.square {
    width: 20px;
    height: 20px;
    background: blue;
}
</style>

<p>There should be a blue square below.</p>
<div class="multicol">
    <div class="square"></div>
    <div class="square"></div>
    <div class="square"></div>
    <div class="square"></div>
    <div id="elm">
        <div class="square"></div>
    </div>
    <div class="square"></div>
    <div class="square"></div>
    <div class="square"></div>
    <div class="square"></div>
</div>

<script>
    document.body.offsetTop;
    var elm = document.getElementById("elm");
    elm.style.willChange = "transform";
</script>