Bug 1561249 - Check that MediaStream's onactive and oninactive attributes are not supported in WPT. r=jib

Differential Revision: https://phabricator.services.mozilla.com/D35822

--HG--
extra : moz-landing-system : lando

testing/web-platform/tests/mediacapture-streams/historical.https.html

@@ -20,4 +20,14 @@ test(() => {
   const mediaStream = new MediaStream();
   assert_throws(new TypeError(), () => URL.createObjectURL(mediaStream));
 }, "Passing MediaStream to URL.createObjectURL() should throw");
+
+test(() => {
+  const mediaStream = new MediaStream();
+  assert_false("onactive" in mediaStream);
+}, "MediaStream.onactive should not exist");
+
+test(() => {
+  const mediaStream = new MediaStream();
+  assert_false("oninactive" in mediaStream);
+}, "MediaStream.oninactive should not exist");
 </script>