document_with_css_image_sharing.html

<html>
  <head>
    <link rel="stylesheet" type="text/css" href="background_image.css">
  </head>
  <body>
    <iframe src="document_with_duplicate_css.html"></iframe>
  </body>
</html>

chromium/chrome/test/data/page_load_metrics/document_with_css_image_sharing.html