<!DOCTYPE html> <!-- webkit-test-runner [ AsyncOverflowScrollingEnabled=true ] -->
<html>
<head>
    <style>
        * {
            box-sizing: border-box;
        }
        body {
            display: grid;
            grid-template-rows: auto;
            grid-template-areas: "main"
        }

        .scroller {
            float: left;
            width: 100%;
            height: 100%;
            border: 1px solid black;
            overflow: scroll;
        }

        .content {
            width: 200%;
            height: 100%;
            background-color: green;
        }

        body.changed .content {
            width: 100%;
        }
        
        .box {
            width: 100px;
            height: 100px;
        }
    </style>
    <script>
        if (window.testRunner)
            testRunner.waitUntilDone();
        window.addEventListener('load', () => {
            setTimeout(() => {
                document.body.classList.add('changed');
                if (window.testRunner)
                    testRunner.notifyDone();
            }, 0);
        }, false);
    </script>
</head>
<body>
    <div id="main">
        <div class="scroller">
           <div class="content">
               <div class="box"></div>
           </div>
        </div>
    </div>
</body>
</html>