<!DOCTYPE html>
<style>
  body {
    border-collapse: collapse;
  }

  :read-write::after {
    content: '';
  }
  :first-child::first-letter {
    background: grey;
  }
</style>
<script>
if (window.testRunner)
  testRunner.dumpAsText();

onload = () => {
  document.documentElement.appendChild(document.createElement('input'));
  document.execCommand('SelectAll');
  document.execCommand('Copy');
  let aElement = document.createElement('a');
  document.body.appendChild(aElement);
  let row = document.createElement('tr');
  aElement.appendChild(row);
  row.appendChild(document.createElement('input'));
  row.appendChild(document.createElement('td'));
  getSelection().modify('move', 'left', 'sentenceboundary');
  document.designMode = 'on';
  document.execCommand('PasteAsQuotation');
  document.styleSheets[0].insertRule(`#nnn {}`);
};
</script>
<!-- Pass if no crash or assert. -->