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chromium/third_party/blink/web_tests/fast/forms/checkbox/checkbox-child-hidden.html 

<!doctype html>
<link rel="match" href="checkbox-child-hidden-expected.html">

<label>
<input type="checkbox" id="cb" />
Checkbox
</label>

<script>
  var checkbox = document.getElementById("cb");
  checkbox.appendChild(document.createTextNode("Checkbox"));
</script>