chromium/third_party/blink/web_tests/external/wpt/css/css-view-transitions/iframe-and-main-frame-transition-old-main-new-iframe-ref.html

<!DOCTYPE html>
<title>View transitions: iframe and main frame transition at the same time (ref)</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<link rel="author" href="mailto:[email protected]">
<style>
iframe {
  position: fixed;
  top: 0;
  left: 0;
  width: 50vw;
  height: 50vh;
}

body {
  background: green;
}
</style>

<iframe srcdoc="
<style>
body {
  background: lightblue;
}
</style>
"></iframe>