<svg xmlns="http://www.w3.org/2000/svg" onload="f()">
  <rect width="50" height="50"/>
  <g>
    <style scoped="">
      rect { fill: blue }
    </style>
    <rect x="60" width="50" height="50"/>
  </g>
  <rect x="120" width="50" height="50"/>
  <script>
    function f() {
      document.getElementsByTagName("style")[0].removeAttribute("scoped");
    }
  </script>
</svg>