[preload] Opt-in to single-page test feature (#19913) testharness.js was recently extended with an API to explicitly opt-in to the "single page test" feature [1]. As per WPT RFC 28 [2], tests which do not use this API and which do not declare any subtests will soon be reported as a harness error. Update the tests which previously opted in implicitly to use the new API. [1] https://github.com/web-platform-tests/wpt/pull/19449 [2] https://github.com/web-platform-tests/rfcs/blob/master/rfcs/single_test.md
diff --git a/preload/single-download-late-used-preload.html b/preload/single-download-late-used-preload.html index 51533ba..bf02fdb 100644 --- a/preload/single-download-late-used-preload.html +++ b/preload/single-download-late-used-preload.html 
@@ -5,6 +5,7 @@  <script src="/preload/resources/preload_helper.js"></script>  <link rel=preload href="resources/square.png?pipe=trickle(d1)" as=image>  <script> + setup({ single_test: true });  var link = document.getElementsByTagName("link")[0]  assert_equals(link.as, "image");  link.addEventListener("load", () => {