at-supports-rule-insecure-context.html

<!DOCTYPE html>
<script src="../resources/get-host-info.js"></script>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<style>
#test {
  content: 'pass';
}

@supports (background: paint(foo)) {
  #test {
    content: 'fail';
  }
}
</style>
<div id="test"></div>
<script>
  if (window.location.origin != get_host_info().UNAUTHENTICATED_ORIGIN) {
    window.location = get_host_info().UNAUTHENTICATED_ORIGIN + window.location.pathname;
  } else {
    test(function() {
      const element = document.getElementById('test');
      assert_false(window.isSecureContext);
      assert_equals(getComputedStyle(element).content, '"pass"');
    });
  }
</script>

chromium/third_party/blink/web_tests/http/tests/csspaint/at-supports-rule-insecure-context.html