<html>
<body>
    <script src="../../resources/js-test.js"></script>
    <script>
        description('Tests that DOM timers gets throttled on hidden pages once they reach the max nesting level');
        jsTestIsAsync = true;

        let timerCount = 0;
        const timeoutInterval = 10;
        const maxNestingLevel = 5;
        let timerHandle = 0;

        function testTimer()
        {
            ++timerCount;

            timerHandle = setTimeout(testTimer, timeoutInterval);
            if (timerCount >= maxNestingLevel) {
                shouldBeTrue("internals.isTimerThrottled(timerHandle)");
                testRunner.resetPageVisibility();
                clearTimeout(timerHandle);
                finishJSTest();
                return;
            } else
                shouldBeFalse("internals.isTimerThrottled(timerHandle)");
        }

        function runTest()
        {
            if (!window.testRunner) {
                debug('This test requires testRunner');
                return;
            }
            testRunner.overridePreference("WebKitHiddenPageDOMTimerThrottlingEnabled", 1);

            timerHandle = setTimeout(testTimer, timeoutInterval);
            shouldBeFalse("internals.isTimerThrottled(timerHandle)");
        }
        onload = function() {
            document.onvisibilitychange = () => {
                if (!document.hidden)
                    return;
                document.onvisibilitychange = null;
                runTest();
            };
            testRunner.setPageVisibility("hidden");
        };
    </script>
</body>
</html>