LayoutTests/compositing/fixed-with-main-thread-scrolling.html

<!DOCTYPE html>
<html>
<head>
    <style>
        body {
            height: 6000px;
        }
        .box {
            position: fixed;
            top: 10px;
            left: 10px;
            width: 200px;
            height: 200px;
            background-color: green;
        }
        
        .fixed-background {
            margin-top: 300px;
            height: 200px;
            background-image: linear-gradient(white, silver);
            background-attachment: fixed;
        }
    </style>
    <script>
        if (window.testRunner) {
            testRunner.waitUntilDone();
        }

        function scrollTest()
        {
            eventSender.mouseMoveTo(20, 20);
            eventSender.monitorWheelEvents();
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -1, "began", "none");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "changed", "none");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "changed", "none");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -1, "changed", "none");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, 0, "ended", "none");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "none", "begin");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "none", "continue");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "none", "continue");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "none", "continue");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, -100, "none", "continue");
            eventSender.mouseScrollByWithWheelAndMomentumPhases(0, 0, "none", "end");
            eventSender.callAfterScrollingCompletes(() => {
                setTimeout(() => {
                    testRunner.notifyDone()                
                }, 0);
            });
        }

        window.addEventListener('load', () => {
            setTimeout(() => {
                scrollTest();
            }, 0)
        }, false);
    </script>
</head>
<body>

<div class="box"></div>

<div class="fixed-background">
    I have a fixed background.
</div>
</body>
</html>