<!DOCTYPE html>
<body>
<script src="../../resources/js-test-pre.js"></script>
<div id="testElement">Test</div>
<script>
description("Tests that a repeating timer changing the style of a visible element does not get throttled.");
jsTestIsAsync = true;

var iterationCount = 0;
var timeoutId;
var testElement = document.getElementById("testElement");
var wasThrottled = false;

function timerCallback()
{
  ++iterationCount;
  // Interact with the style of the element.
  testElement.style["left"] = "" + iterationCount + "px";

  // 5 iterations should suffice to throttle the timer.
  if (iterationCount == 5) {
    // Do not use shouldBeTrue() here because it would cause a DOM tree mutation and
    // unthrottle the DOM Timer.
    wasThrottled = internals.isTimerThrottled(timeoutId);
  } else if (iterationCount == 6) {
    debug("5th iteration, timer should not have been throttled.");
    shouldBeFalse("wasThrottled");
    debug("6th iteration, timer should still be unthrottled.");
    shouldBeFalse("internals.isTimerThrottled(timeoutId)");
    clearInterval(timeoutId);
    finishJSTest();
  }
}

timeoutId = setInterval(timerCallback, 10);
debug("The timer should initially not be throttled.");
shouldBeFalse("internals.isTimerThrottled(timeoutId)");
</script>
<script src="../../resources/js-test-post.js"></script>
</body>