Codebase Browser
chromium
Go to App

chromium/content/test/data/accessibility/html/offscreen-iframe-content.html 

<!doctype html>
<html>
<body>
  <div role="group" aria-label="iframe_onscreen" style="height:300px; background-color: red;"></div>
  <div role="group" aria-label="iframe_offscreen" style="height:200px; background-color: green"></div>
</body>
</html>