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chromium/chrome/test/data/chromedriver/page_with_iframe_redbox.html 

<!DOCTYPE html>
<html>
  <body style="overflow: hidden">
    <iframe id="frm" width="300" height="200" style="position: absolute; top: 2500px; left: 2500px; border: 20px solid red; padding: 20px; margin: 20px" src="page_with_redbox.html">
    </iframe>
  </body>
</html>