LayoutTests/platform/mac/fast/frames/contentFrame-disconnecting-crash.html

<script>
if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
}
  onload = () => {
    let img = document.createElement('img');
    img.onerror = () => {
      document.execCommand('Undo');
      document.write('PASS: There was no crash.');
      testRunner.notifyDone();
    };
    img.src = 'data:';
    document.designMode = 'on';
    document.execCommand('SelectAll');
    document.execCommand('InsertImage', false, '#');
    document.execCommand('SelectAll');
    document.execCommand('Bold');
    document.execCommand('Italic');
    let embed = document.createElement('embed');
    document.querySelector('i').appendChild(embed);
    embed.src = 'data:';
  };
</script>