chromium/third_party/blink/web_tests/external/wpt/client-hints/resources/expect-no-client-hints-headers.html

<!DOCTYPE html>
<html>
<body>
<script>

// This test checks if browser attaches the viewport-width client hint in the
// HTTP request headers.

// resources/echo-client-hints-received.py sets the response headers depending on the set
// of client hints it receives in the request headers.

fetch("../resources/echo-client-hints-received.py").then(r => {
  if(r.status == 200 &&
     !r.headers.has("viewport-width-received") &&
     !r.headers.has("viewport-width-received")) {
    window.top.opener.postMessage('PASS', '*');
  } else {
    window.top.opener.postMessage('FAIL', '*');
  }
});

</script>
</body>
</html>