<!DOCTYPE html>
<html>
<head>
    <script>
        const maxNestingLevel = 5;
        let i = 0;
        let handle = null;

        function step()
        {
            i++;
            if (i == maxNestingLevel)
                parent.window.postMessage("timerReachedMaxNestingLevel", "*");
        }

        window.onmessage = function(message)
        {
            var re = /report-throttle-(cross|same)/;
            var match = re.exec(message.data);

            if (match) {
                var frameId = match[1];
                if (window.internals)
                    parent.window.postMessage("throttled[" + frameId + "]: " + internals.isTimerThrottled(handle), "*");
            }
        }

        window.addEventListener("load", function() {
            handle = setInterval(step, 5);
        }, false);
    </script>
</head>
<body>
    <div style="height: 100px; width: 100px; background: silver" onclick=""></div>
    Child frame.
</body>
</html>