Fix content-visibility-050.html flakiness

https://bugs.webkit.org/show_bug.cgi?id=238033

Reviewed by Tim Nguyen.

Import test from WPT.

* LayoutTests/imported/w3c/web-platform-tests/css/css-contain/content-visibility/content-visibility-050.html:
* LayoutTests/platform/mac-wk2/TestExpectations:

Canonical link: https://commits.webkit.org/266542@main

LayoutTests/imported/w3c/web-platform-tests/css/css-contain/content-visibility/content-visibility-050.html

@@ -28,10 +28,11 @@
     focusable.tabIndex = 0;
     container.appendChild(focusable);
     focusable.focus();
-    requestAnimationFrame(() => {
-      t.step(() => assert_greater_than(document.scrollingElement.scrollTop, 500));
-      t.done();
-    });
+    step_timeout(finish, 0);
+  }
+  function finish() {
+    t.step(() => assert_greater_than(document.scrollingElement.scrollTop, 500));
+    t.done();
   }
   onload = requestAnimationFrame(() => requestAnimationFrame(runTest));
 }, "Using tabindex to focus an newly constructed element in an auto subtree focuses element");

LayoutTests/platform/mac-wk2/TestExpectations

@@ -1824,8 +1824,6 @@ webkit.org/b/259464 [ Monterey+ ] fast/events/wheel/redispatched-wheel-event.htm
 webkit.org/b/259497 [ x86_64 ] imported/w3c/web-platform-tests/webcodecs/temporal-svc-encoding.https.any.html?vp9 [ Failure ]
 webkit.org/b/259496 [ x86_64 ] imported/w3c/web-platform-tests/webcodecs/temporal-svc-encoding.https.any.worker.html?vp9 [ Failure ]
 
-webkit.org/b/238033 imported/w3c/web-platform-tests/css/css-contain/content-visibility/content-visibility-050.html [ Pass Failure ]
-
 webkit.org/b/259183 fast/attachment/mac/wide-attachment-image-controls-basic.html [ Pass Failure ]
 
 webkit.org/b/259699 media/media-source/media-source-duplicate-seeked.html [ Pass Failure ]