<!DOCTYPE html>
<html>
<head>
    <title>Test that the scrolling tree is in z-order.</title>
    <script>
        if (window.testRunner) {
            testRunner.dumpAsText();
            testRunner.waitUntilDone();
        }

        function doTest() {
            requestAnimationFrame(() => {
                document.body.classList.add('changed');

                if (window.internals)
                    document.getElementById('scrollingTree').innerText = window.internals.scrollingStateTreeAsText() + "\n";

                if (window.testRunner)
                    testRunner.notifyDone();
            });
        }

        window.addEventListener('load', doTest, false);
    </script>
    <style>
        .fixed {
            position: fixed;
            background-color: silver;
            border: 1px solid black;
            width: 200px;
            height: 150px;            
        }
        
        #second {
            left: 100px;
            top: 100px;
        }

        #third {
            left: 150px;
            top: 50px;
        }
        
        .changed #first {
            z-index: 2;
        }

        .changed #third {
            z-index: 1;
        }
    </style>
</head>
<body>
    <div class="fixed" id="first">First</div>
    <div class="fixed" id="second">Second</div>
    <div class="fixed" id="third">Third</div>
    <pre id="scrollingTree"></pre>
</body>
</html>