LayoutTests/scrollbars/async-overflow-custom-scrollbar.html

<!DOCTYPE html> <!-- webkit-test-runner [ AsyncOverflowScrollingEnabled=true ] -->
<html>
    <head>
        <style>
            .scroller {
                width: 400px;
                height: 400px;
                overflow-y: scroll;
            }

            .contents {
                width: 200%;
                height: 200%;
                background-color: silver;
            }
            
            .scroller::-webkit-scrollbar {
                width: 20px;
                height: 20px;
            }

            .scroller::-webkit-scrollbar-thumb {
                background-color: green;
            }
            
            .scroller::-webkit-scrollbar-corner {
                background-color: green;
            }
        </style>
    </head>
    <body>
        <div class="scroller">
            <div class="contents"></div>
        </div>
    </body>
</html>