LayoutTests/compositing/overflow/content-gains-scrollbars.html

<!DOCTYPE html>
<style>
.container {
width: 100px;
height:100px;
position:absolute;
-webkit-transform:translateZ(0);
overflow:auto;
}

.content {
-webkit-transform: translateZ(0);
position:absolute;
width:10px;
height:10px;
}

.tall {
height:200px;
}

.wide {
width:200px;
}

.resizeWidget {
resize: both;
}

</style>
<pre id="layerTree"></pre>
<div class="container">
  <div id="vertical" class="content"></div>
</div>
<div class="container">
  <div id="horizontal" class="content"></div>
</div>
<div class="container">
  <div id="both" class="content"></div>
</div>
<div id="corner" class="container">
  <div class="content"></div>
</div>
<script>
function finishTest() {
    document.getElementById("vertical").classList.add("tall"); // topmost div gets a vertical scrollbar
    document.getElementById("horizontal").classList.add("wide"); // second div gets a horizontal scrollbar
    document.getElementById("both").classList.add("wide"); // third div gets both
    document.getElementById("both").classList.add("tall"); // vertical and horizontal scrollbars
    document.getElementById("corner").classList.add("resizeWidget"); // bottom div gets a resize corner but no scrollbars
    if (window.testRunner) {
        testRunner.displayAndTrackRepaints(); // Ensure compositor tree is up to date.
        document.getElementById("layerTree").innerText = window.internals.layerTreeAsText(document);
    }
}

if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.displayAndTrackRepaints(); // Force compositor state to be updated before the container needs any overflow controls
    finishTest();
} else
    window.setTimeout(finishTest, 0);
</script>