chromium/third_party/blink/web_tests/paint/overflow/transformed-iframe-clipping.html

<!DOCTYPE html>
<style>
iframe {
  transform-origin: left top;
  transform: scale(2.0);
  border: 2px solid red;
}
div {
  overflow: hidden;
  border: 1px solid black;
  height: 150px;
  width: 300px;
  border-radius: 4px;
}
</style>
<div>
<iframe>
</iframe>
</div>