chromium/third_party/blink/manual_tests/frames/resources/blit-on-scroll-subframe.html

<style type="text/css" media="screen">
  iframe {
    border: 1px solid black;
  }
  
  body {
      height: 1000px;
  }
</style>
<iframe id="subframe" src="blit-on-scroll-subsubframe.html" width="280" height="250"></iframe>