html5中notification问题在谷歌浏览器中也不能运行


<!DOCTYPE HTML>
<html>
<head
<meta charset="gbk">  
<title>Creating OS notifications in HTML5</title>
</head>
<body>
<input type="button" value="验证授权" onclick="init();" />
<input type="button" value="弹出消息" onclick="notify();" />


    <script type="text/javascript">
        const miao = 5;

        function init() {
            if (window.webkitNotifications) {
                window.webkitNotifications.requestPermission();
            }
        }

        function notify() {
            var icon = "logo.png";
            var title = "窗口将在 " + miao + " 5后关闭";
            var body =  "PHP100 提供的 HTML5视频教程 桌面提醒API";

            if (window.webkitNotifications) {
                if (window.webkitNotifications.checkPermission() == 0) {
                    var popup = window.webkitNotifications.createNotification(icon, title, body);
                    popup.ondisplay = function(event) {
                        setTimeout(function() {
                            event.currentTarget.cancel();
                        }, miao * 1000);
                    }
                    popup.show();
                } else {
                    window.webkitNotifications.requestPermission();
                    return;
                }
            }
        }
    </script>

</body>
</html>

你chrome版本太低不支持window.webkitNotifications这个对象吧。。我这里版本 38.0.2125.104 webkitNotifications为undefined