Bug 1591668 [wpt PR 19926] - [html] Convert srcdoc_change_hash.html t…

…o promise_test, a=testonly

Automatic update from web-platform-tests
[html] Convert srcdoc_change_hash.html to promise_test

This is an alternative to adding `setup({ single_test: true })` in
web-platform-tests/wpt#19918.
--

wpt-commits: 2127be728a1d785b3443eaec5955070c0908aa62
wpt-pr: 19926

Differential Revision: https://phabricator.services.mozilla.com/D53517

UltraBlame original commit: c1d0439f81cad16038d0c7d8fa991c93bcb807de

testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/srcdoc_change_hash.html

@@ -1,12 +1,10 @@
-
-
-
+<title>same-document navigation inside an srcdoc iframe using location.hash</title>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <script src="/resources/testdriver.js"></script>
 <script src="/resources/testdriver-vendor.js"></script>
 <script>
-  async function test() {
+  promise_test(async () => {
     // Wait until 'document' is available.
     await new Promise(resolve => window.addEventListener('load', resolve));
 
@@ -66,8 +64,5 @@
       await hash_changed;
       assert_equals(iframe.contentWindow.location.href, "about:srcdoc#2");
     }
-
-    done();
-  }
-  test();
+  });
 </script>