LibWeb: Reschedule HTML event loop processing if navigable needs repaint

This is an attempt to fix the hanging CI on macOS caused by some
screenshot requests being stuck unprocessed. With this change, we at
least make sure that the HTML event loop processing, which triggers
repainting, will happen as long as there are navigables that need to be
repainted.

Userland/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp

@@ -207,6 +207,8 @@ void EventLoop::process()
     //         loop processing.
     for_each_fully_active_document_in_docs([&](DOM::Document& document) {
         auto navigable = document.navigable();
+        if (navigable && !navigable->has_a_rendering_opportunity() && navigable->needs_repaint())
+            schedule();
         if (navigable && navigable->has_a_rendering_opportunity())
             return;
         auto* browsing_context = document.browsing_context();