LayoutTests/editing/pasteboard/copy-paste-crash-onbeforeunload-event.html

<p>This test passes if it doesn't crash.</p>
<script>
  if (window.testRunner)
    testRunner.dumpAsText();
  
  onbeforeunload = () => {
    for (let i = 0; i < 1000; i++)
      document.execCommand('Copy');
  };
  onload = async () => {
      document.execCommand('SelectAll');
    location.host = '';
    await caches.has('a');
    window.open();
    
  };
</script>