chromium/third_party/blink/web_tests/external/wpt/css/css-view-transitions/navigation/root-element-transition-iframe.html

<!DOCTYPE html>
<html class="reftest-wait">
<title>View transitions: basic cross-document navigation in an iframe</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-2/">
<link rel="author" href="mailto:[email protected]">
<link rel="match" href="root-element-transition-iframe-ref.html">
<script src="/common/reftest-wait.js"></script>
<script src="resources/common.js"></script>

<iframe id="inner" src="resources/root-element-transition-iframe.html?blue"></iframe>
<script>
async function runTest() {
  let frame = document.getElementById("inner");
  frame.contentWindow.postMessage("checkrendering");
  await waitForMessage("rendered");

  frame.src = "resources/root-element-transition-iframe.html?grey";
  await waitForMessage("transition");

  takeScreenshot();
}
onload = () => requestAnimationFrame(() => requestAnimationFrame(runTest));
</script>
</html>