firefox/devtools/client/framework/test/doc_cached-resource_iframe.html

<!-- Any copyright is dedicated to the Public Domain.
     http://creativecommons.org/publicdomain/zero/1.0/ -->

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
  </head>
  <body>
    <script>
    console.log("Hello from child");
    </script>
  </body>
</html>