LayoutTests/compositing/repaint/change-notselfpainting-to-scroller.html

<!-- webkit-test-runner [ AsyncOverflowScrollingEnabled=true ] -->
<!DOCTYPE HTML>
<html>
<head>
<style>
  ::-webkit-scrollbar {
    width: 6px;
  }
  ::-webkit-scrollbar-thumb {
    background: grey;
  }
</style>
</head>
<body>
<div style="width: 400px; height: 400px; transform: translateZ(0px); background: lightblue">
  <div style="overflow-y:auto; width: 200px; height: 200px;">
    <div style="height: 100px; text-align: right">Hello there</div>
    <div id="change" style="height: 100px; background: red"></div>
  </div>
  Hi
</div>
<pre id=result></pre>

<script>
if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
}

function timerAfterRAF(callback) {
    return requestAnimationFrame(() => setTimeout(callback, 0));
}

function runTest() {
    if (window.internals)
        internals.startTrackingRepaints();
    change.style.height = "400px";

    timerAfterRAF(() => {
        if (window.internals) {
            result.innerText = internals.repaintRectsAsText();
            internals.stopTrackingRepaints();
        }
        if (window.testRunner)
            testRunner.notifyDone();

    });
};

window.addEventListener('load', () => {
    timerAfterRAF(runTest);
}, false);

</script>

</body>
</html>