<style>
  :after, :before {
      content: counter(a);
      -webkit-appearance: discrete-capacity-level-indicator;
  }
</style>
<script>
  function main() {
      if (window.testRunner)
          testRunner.dumpAsText();
      console.log("This test passes if it does not crash.");
      document.execCommand("selectAll",false,null);
      window.getSelection().modify("extend","forward","lineboundary");
      window.getSelection().getRangeAt(0);
      document.execCommand("selectAll",false,null);
      window.getSelection().modify("extend","backward","lineboundary");
      window.getSelection().getRangeAt(0);
  }
</script>
<body onload="main()">
A