<!DOCTYPE html>
<script src="../../resources/run-after-layout-and-paint.js"></script>
<svg>
  <linearGradient id="f">
    <stop stop-color="red"/>
  </linearGradient>
  <linearGradient id="f">
    <stop stop-color="green"/>
  </linearGradient>
  <rect width="100" height="100" fill="url(#f) orange"/>
</svg>
<script>
runAfterLayoutAndPaint(function() {
  document.querySelector('#f').id = 'g';
}, true);
</script>