chromium/third_party/blink/web_tests/external/wpt/screen-capture/resources/delegate-request-subframe.sub.html

<!DOCTYPE html>
<title>Display-capture request delegation test: subframe</title>

<script>
  function reportResult(msg) {
      window.top.postMessage({"type": "result", "result": msg}, "*");
  }

  window.addEventListener("message", async e => {
      if (e.data.type == "make-display-capture-request") {
          try {
              const stream = await navigator.mediaDevices.getDisplayMedia();
              stream.getTracks()[0].stop();
              reportResult("success");
          } catch(e) {
              reportResult("failure");
          }
      }
  });

  window.top.postMessage({"type": "subframe-loaded"}, "*");
</script>