LayoutTests/fast/inline/crash-when-revert-has-trailing-line-break.html

<style>
  th, body, span, html {
    padding-left: 250px;
  }
</style>
<script>
if (window.testRunner)
  testRunner.dumpAsText();

  onload = () => {
    let div = document.createElement('div');
    document.querySelector('style').appendChild(div);
    document.styleSheets[0].insertRule(`pre { aspect-ratio: 1; }`);
    document.body.appendChild(document.createElement('pre'));
    let th = document.createElement('th');
    document.body.appendChild(th);
    document.designMode = 'on';
    document.execCommand('SelectAll');
    document.execCommand('InsertLineBreak');
    getSelection().selectAllChildren(th);
    document.execCommand('InsertText', false, 'a');
    document.execCommand('UseCSS', false, 'false');
    div.before(undefined);
    document.execCommand('InsertLineBreak');
    document.execCommand('SelectAll');
    document.execCommand('Copy');
    document.execCommand('PasteAndMatchStyle');
    document.execCommand('JustifyFull');
  };
</script>
<!-- PASS if no crash or assert. -->