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chromium
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chromium/third_party/blink/web_tests/fast/scrolling/resources/resize-corner-tracking-touch-child-iframe.html 

<!DOCTYPE html>
<html>
<body>
<iframe id="inner-iframe" src="resize-corner-tracking-touch-grandchild-iframe.html"
  style="resize:both; width: 200px; height: 200px;"></iframe>
</body>
</html>