Add layout test for DOM timer throttling in iframe scrolled out of viewport

        https://bugs.webkit.org/show_bug.cgi?id=138884

        Reviewed by NOBODY (OOPS!).

        Add a layout test to test that a repeating DOM timer inside an iframe

        get throttled if the iframe is scrolled out of the viewport.

        * fast/dom/resources/timer-throttling-iframe.html: Added.

        * fast/dom/timer-throttle-on-scrolling-iframe-away.html: Added.

2014-11-19  Chris Dumez  <cdumez@apple.com>

<!DOCTYPE html>

<body>

<div id="testElement">TEST</div>

<script>

var testElement = document.getElementById("testElement");

var iterationCount = 0;

var timeoutId;

function timerCallback() {

  ++iterationCount;

  // Change style of Element.

  testElement.style["opacity"] = "" + (iterationCount / 10.);

  parent.timerFired(iterationCount, internals.isTimerThrottled(timeoutId));

  if (iterationCount == 7)

    clearInterval(timeoutId);

}

timeoutId = setInterval(timerCallback, 0);

</script>

</body>

<!DOCTYPE html>

<body>

<script src="../../resources/js-test-pre.js"></script>

<script>

description("Tests that a repeating timer in an iframe changing the style of an element gets throttled when scrolling the frame out of view.");

jsTestIsAsync = true;

function scrollFrameOutOfView()

{

  debug("Scrolling frame out of view.");

  window.scrollBy(0,800);

}

function timerFired(iterationCount, isThrottled) {

  // 5 iterations should suffice to throttle the timer.

  if (iterationCount == 5) {

    debug("Frame is inside viewport, timer should not be throttled");

    isTimerThrottledBeforeScroll = isThrottled;

    shouldBeFalse("isTimerThrottledBeforeScroll");

    scrollFrameOutOfView();

  } else if (iterationCount == 7) {

    debug("Frame is outside viewport, timer should now be throttled");

    isTimerThrottledAfterScroll = isThrottled;

    shouldBeTrue("isTimerThrottledAfterScroll");

    finishJSTest();

  }

}

</script>

<div style="position: relative; width: 1600px; height: 2400px; background-color: green;">

  <iframe id="testFrame" src="resources/timer-throttling-iframe.html" style="width: 100px; height: 100px;"></iframe>

</div>

<script src="../../resources/js-test-post.js"></script>

</body>