use-external-dynamic-base-change.html

<!DOCTYPE html>
<script src="../../resources/run-after-layout-and-paint.js"></script>
<svg>
  <rect id="rect" width="0" height="100"/>
  <use xlink:href="#rect" fill="green"/>
</svg>
<script>
runAfterLayoutAndPaint(function() {
  var baseElement = document.createElement("base");
  baseElement.setAttribute("href", "http://www.example.com/");
  document.head.appendChild(baseElement);
  document.querySelector('#rect').setAttribute("width", "100");
}, true);
</script>

chromium/third_party/blink/web_tests/svg/custom/use-external-dynamic-base-change.html