chromium/third_party/blink/web_tests/fast/events/fire-scroll-event.html

<html>
<script src="../../resources/js-test.js"></script>
<body style="min-width: 5000px; min-height: 5000px">
<script>
description('Checks that the scroll event fires on the document asychronously and only once.');

var eventCount = 0;
var doneTimeout;

onscroll = function(event)
{
    eventCount++;
    if (eventCount == 1) {
        debug('Scroll event bubbles: ' + event.bubbles);
        var scrollX = document.scrollingElement.scrollLeft;
        var scrollY = document.scrollingElement.scrollTop;
        testPassed('Scroll position: (' + scrollX + ', ' + scrollY + ')');
        // Don't call notifyDone straight away, in case there's another scroll event coming.
        doneTimeout = setTimeout(finishJSTest, 100);
    } else {
        clearTimeout(doneTimeout);
        testFailed('Scroll handler was invoked ' + eventCount + ' times');
        finishJSTest();
    }
}

onload = function()
{
    window.scrollTo(100, 100);
    if (eventCount > 0) {
        testFailed('Scroll event fired synchronously');
        finishJSTest();
    }
    window.scrollTo(200, 200);
}
var jsTestIsAsync = true;
</script>
</body>
</html>