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chromium/third_party/blink/manual_tests/scrollable-positioned-frame.html 

<!DOCTYPE html>
<html>
<body>
  <p>The contents of this frame should scroll with the mouse wheel.</p>
  <iframe width=200 scrolling=yes src="resources/frame-textarea.html" style="position:fixed; left: 200px" id="frame"></iframe>
</body>
</html>