<!DOCTYPE html>
<html>
    <head>
        <style>
            video {
                width: 480px;
                height: 320px;
            }
        </style>
        <script>
            var isFirstClick = true;
            function handleMouseDown() {
                document.querySelector(isFirstClick ? "#first" : "#second").pause();
                isFirstClick = false;
            }

            function handleFirstPause() {
                setTimeout(function() {
                    try {
                        window.webkit.messageHandlers.testHandler.postMessage("paused");
                    } catch(e) { }
                }, 0);
            }

            function handleSecondPause() {
                setTimeout(function() {
                    try {
                        window.webkit.messageHandlers.testHandler.postMessage("paused");
                    } catch(e) { }
                }, 0);
            }

            function beganAutoplaying() {
                setTimeout(function() {
                    try {
                        window.webkit.messageHandlers.testHandler.postMessage("autoplayed");
                    } catch(e) {
                    }
                }, 0)
            }
        </script>
    </head>
    <body onmousedown=handleMouseDown()>
        <video autoplay onplaying=beganAutoplaying() loop id="first" src="large-video-with-audio.mp4" onpause=handleFirstPause()></video>
        <video autoplay onplaying=beganAutoplaying() loop id="second" src="large-video-with-audio.mp4" onpause=handleSecondPause()></video>
    </body>
<html>