Codebase Browser
chromium
Go to App

chromium/content/test/data/coreferencingframe_1.html 

<!DOCTYPE html>
<html>
<body>
  A - This page has co-referencing nested iframes.
  <iframe id="child-0" src="/cross-site/b.com/coreferencingframe_2.html"></iframe>
</body>
</html>