<!DOCTYPE html>
<html>
    <head>
        <style>
            video {
                width: 480px;
                height: 320px;
            }
            div {
                margin-top: 5000px;
            }
        </style>
        <script>
            function scrollVideoOutOfView() {
                document.querySelector("div").scrollIntoView();
                setTimeout(function() {
                    window.webkit.messageHandlers.testHandler.postMessage("scrolled");
                }, 0);
            }

            function beganAutoplaying() {
                setTimeout(function() {
                    try {
                        window.webkit.messageHandlers.testHandler.postMessage("autoplayed");
                    } catch(e) {
                    }
                }, 0)
            }
        </script>
    </head>
    <body>
        <video autoplay onplaying=beganAutoplaying() loop id="first" src="large-video-with-audio.mp4"></video>
        <br>
        <div>hello world!</div>
    </body>
<html>