chromium/third_party/blink/web_tests/fast/css/pseudo-element-selector-scrollbar-hover.html

<!DOCTYPE html>
<html>
<head>
<title>Scrollbar thumb re-rendering on hover</title>
<style>
    #scrollable {
        height: 200px;
        width: 200px;
        overflow: auto;
        background-color: red;
        -webkit-appearance: none;
    }

    #scrollable::-webkit-scrollbar {
        width: 10px;
        background-color: red;
    }

    #scrollable::-webkit-scrollbar-thumb {
        background-color: red;
    }

    #scrollable:hover {
        background-color: green;
    }

    #scrollable:hover::-webkit-scrollbar {
        background-color: green;
    }

    #scrollable:hover::-webkit-scrollbar-thumb {
        background-color: green;
    }

    #content {
        height: 400px;
        width: 100px;
    }
</style>
</head>
<body>
<p>Bug <a href="http://webkit.org/b/109230">109230</a>: REGRESSION(r130089): Scrollbar thumb no longer re-rendered on hover</p>
<p>For this test to pass, the below box should be green (in DumpRenderTree).<br>
Interactively, the whole box should turn green on mouseover, even if not over the scrollbar thumb.</p>
<div id="scrollable">
    <div id="content"></div>
</div>
<script>
    function hoverOverScrollable()
    {
        if (!window.testRunner)
            return;

        var scrollable = document.getElementById('scrollable');
        var scrollBox = scrollable.getBoundingClientRect();
        var scrollableCenterX = (scrollBox.left + scrollBox.right) / 2;
        var scrollableCenterY = (scrollBox.top + scrollBox.bottom) / 2;

        eventSender.mouseMoveTo(scrollableCenterX, scrollableCenterY);
    }
    window.addEventListener('load', hoverOverScrollable);
</script>
</body>
</html>