estSrcOnMicrotask("");
  img = new Image();
  let png = "/images/green.png?" + Math.random();
  let resolved_png = new URL(png, document.documentURI).href;
  testSrcOnMicrotask("");
  // Both .src and .srcset assignments are relevant mutations. So the first task should be "canceled" (return early).
  // appendChild is not a relevant mutation unless in a <picture> element.
  img.src = png;
  testSrcOnMicrotask("");
  img.srcset = png;
  testSrcOnMicrotask(resolved_png);
  document.body.appendChild(img);
  te