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];