Bug 1854761 [wpt PR 42106] - Fix <source> version of the media-src-7_2_2.sub.html test., a=testonly

Automatic update from web-platform-tests
Fix <source> version of the media-src-7_2_2.sub.html test.

<source> elements can't be changed retroactively like the test was
doing. The media element would sometimes start the load and fail
since the source had no content. Instead add the <source> node in
one go.

Fixed: 1484341
Change-Id: I0e2c53fedcee121d59563d140d4d82793fcba5d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4883970
Reviewed-by: Jonathan Hao <phao@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1200339}

--

wpt-commits: f3b2a3dbd7052b19a8bed15eea85e4b768364cee
wpt-pr: 42106

testing/web-platform/tests/content-security-policy/media-src/media-src-7_2_2.sub.html

@@ -40,16 +40,17 @@
 
     <audio id="audioObject" width="320" height="240" controls
            onloadeddata="media_loaded(source_test)">
-        <source id="audioSourceObject"
-                type="audio/ogg"
-                onerror="media_error_handler(source_test)">
     </audio>
     <audio id="audioObject2" width="320" height="240" controls
            onerror="media_error_handler(src_test)"
            onloadeddata="media_loaded(src_test)">
-
+    </audio>
     <script>
-        document.getElementById("audioSourceObject").src = mediaURL;
+        let source = document.createElement("source");
+        source.src = mediaURL;
+        source.type = "audio/ogg";
+        source.onerror = _ => { media_error_handler(source_test); }
+        document.getElementById("audioObject").appendChild(source);
         document.getElementById("audioObject2").src = mediaURL;
     </script>