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chromium/third_party/blink/web_tests/fragmentation/outline-crossing-columns.html 

<!DOCTYPE html>
<div style="columns: 2; width: 250px; height: 100px">
  <div style="width: 30px; height: 30px"></div>
  <select multiple style="outline: 5px solid green">
    <option>test</option>
    <option>test</option>
    <option>test</option>
    <option>test</option>
    <option>test</option>
  </select>
</div>
<div style="width: 10px; height: 3000px"></div>