src/third_party/web_platform_tests/intersection-observer/v2/scaled-target.html

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/intersection-observer-test-utils.js"></script>

<style>
pre, #log {
  position: absolute;
  top: 0;
  left: 200px;
}
#iframe {
  width: 100px;
  height: 100px;
  border: 0;
  margin-bottom: 10px;
}
#occluder {
  width: 100px;
  height: 100px;
  background-color: blue;
  position: relative;
}
</style>

<iframe id="iframe" src="../resources/scaled-target-subframe.html"></iframe>
<div id="occluder"></div>

<script>
async_test(function(t) {
  let iframe = document.getElementById("iframe");

  function step0(event) {
    assert_equals(event.data, "");
  }

  function step1(event) {
    iframe.style.transform = "scale(2)";
    assert_equals(JSON.stringify(event.data),
                  JSON.stringify([true]));
  }

  function step2(event) {
    assert_equals(JSON.stringify(event.data),
                  JSON.stringify([false]));
  }

  let steps = [step0, step1, step2];

  window.addEventListener("message", event => {
    if (steps.length) {
      t.step(steps.shift(), t, event);
      waitForFrame(t, () => {
        iframe.contentWindow.postMessage("", "*")
      });
    } else {
      t.done();
    }
  });

}, "IntersectionObserver V2 test with scale applied to target.");
</script>