LibWeb: Allow the Performance object to be used by workers

Author: https://github.com/tcl3
Commit: eebdc7bc88
Pull-request: https://github.com/SerenityOS/serenity/pull/23771
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/kalenikaliaksandr
Reviewed-by: https://github.com/shannonbooth

Userland/Libraries/LibWeb/Animations/DocumentTimeline.cpp

@@ -19,7 +19,9 @@ JS_DEFINE_ALLOCATOR(DocumentTimeline);
 JS::NonnullGCPtr<DocumentTimeline> DocumentTimeline::create(JS::Realm& realm, DOM::Document& document, HighResolutionTime::DOMHighResTimeStamp origin_time)
 {
     auto timeline = realm.heap().allocate<DocumentTimeline>(realm, realm, document, origin_time);
-    timeline->set_current_time(document.window()->performance()->now());
+    auto* window_or_worker = dynamic_cast<HTML::WindowOrWorkerGlobalScopeMixin*>(&realm.global_object());
+    VERIFY(window_or_worker);
+    timeline->set_current_time(window_or_worker->performance()->now());
     return timeline;
 }