LibJS+LibWeb: Wrap raw JS::Cell*/& fields in GCPtr/NonnullGCPtr

Author: https://github.com/mattco98
Commit: 7c0c1c8f49
Pull-request: https://github.com/SerenityOS/serenity/pull/17743
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/Loader/FrameLoader.h

@@ -47,7 +47,7 @@ private:
     void load_favicon(RefPtr<Gfx::Bitmap> bitmap = nullptr);
     bool parse_document(DOM::Document&, ByteBuffer const& data);
 
-    HTML::BrowsingContext& m_browsing_context;
+    JS::NonnullGCPtr<HTML::BrowsingContext> m_browsing_context;
     size_t m_redirects_count { 0 };
 };