paint-iframe-background-iframe.html

<!DOCTYPE html>

<html>
<head>
  <style type="text/css" media="screen">
    * {
      background-transparent;
    }
  </style>
</head>
<body>

  <p><!-- this file is transparent --></p>
</body>
</html>

chromium/third_party/blink/web_tests/fast/frames/resources/paint-iframe-background-iframe.html