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chromium/third_party/blink/web_tests/http/tests/inspector-protocol/resources/site_per_process_main.html 

<html>
<title>site_per_process_main</title>
<head></head>
  <body>
    <iframe id="test"></iframe>
    <iframe id="child-2" src="http://devtools.oopif.test:8000/inspector-protocol/resources/iframe.html"></iframe>
  </body>
</html>