<html>
  <head>
    <script>
      var winsToClose = []
      onbeforeunload = function() {
        for (let win of winsToClose) {
          if (win) {
            win.close();
          }
        }
      };
      for (let i = 0; i < 38; i++) {
        customElements.define("custom-element_0", class extends HTMLElement {
          constructor() {
            try { o1 = document.createElement("custom-element_0") } catch (e) {}
            try { winsToClose.push(window.open("javascript:'<html><body>dummy</body></html>';")); } catch (e) {}
          }
        })
        try { o3 = document.createElement("custom-element_0") } catch (e) {}
      }
    </script>
  </head>
</html>
