LibJS: Put zombie cell tracking code behind a compile-time flag

Since this is a debug-only feature, let's not have it impact GC marking
performance when you don't need it.

Userland/Libraries/LibJS/Runtime/FinalizationRegistry.h

@@ -34,7 +34,13 @@ public:
 
 private:
     virtual void visit_edges(Visitor& visitor) override;
-    virtual void did_become_zombie() override { deregister(); }
+
+#ifdef JS_TRACK_ZOMBIE_CELLS
+    virtual void did_become_zombie() override
+    {
+        deregister();
+    }
+#endif
 
     FunctionObject* m_cleanup_callback { nullptr };
 

Userland/Libraries/LibJS/Runtime/Shape.cpp

@@ -238,9 +238,11 @@ FLATTEN void Shape::add_property_without_transition(PropertyName const& property
     add_property_without_transition(property_name.to_string_or_symbol(), attributes);
 }
 
+#ifdef JS_TRACK_ZOMBIE_CELLS
 void Shape::did_become_zombie()
 {
     revoke_weak_ptrs();
 }
+#endif
 
 }

Userland/Libraries/LibJS/Runtime/Shape.h

@@ -88,7 +88,10 @@ public:
 private:
     virtual const char* class_name() const override { return "Shape"; }
     virtual void visit_edges(Visitor&) override;
+
+#ifdef JS_TRACK_ZOMBIE_CELLS
     virtual void did_become_zombie() override;
+#endif
 
     Shape* get_or_prune_cached_forward_transition(TransitionKey const&);
     Shape* get_or_prune_cached_prototype_transition(Object* prototype);

Userland/Libraries/LibJS/Runtime/WeakMap.h

@@ -30,7 +30,13 @@ public:
     virtual void remove_swept_cells(Badge<Heap>, Span<Cell*>) override;
 
 private:
-    virtual void did_become_zombie() override { deregister(); }
+#ifdef JS_TRACK_ZOMBIE_CELLS
+    virtual void did_become_zombie() override
+    {
+        deregister();
+    }
+#endif
+
     void visit_edges(Visitor&) override;
 
     HashMap<Cell*, Value> m_values; // This stores Cell pointers instead of Object pointers to aide with sweeping

Userland/Libraries/LibJS/Runtime/WeakRef.h

@@ -31,7 +31,13 @@ public:
 
 private:
     virtual void visit_edges(Visitor&) override;
-    virtual void did_become_zombie() override { deregister(); }
+
+#ifdef JS_TRACK_ZOMBIE_CELLS
+    virtual void did_become_zombie() override
+    {
+        deregister();
+    }
+#endif
 
     Object* m_value { nullptr };
     u32 m_last_execution_generation { 0 };

Userland/Libraries/LibJS/Runtime/WeakSet.h

@@ -30,7 +30,12 @@ public:
     virtual void remove_swept_cells(Badge<Heap>, Span<Cell*>) override;
 
 private:
-    virtual void did_become_zombie() override { deregister(); }
+#ifdef JS_TRACK_ZOMBIE_CELLS
+    virtual void did_become_zombie() override
+    {
+        deregister();
+    }
+#endif
 
     HashTable<Cell*> m_values; // This stores Cell pointers instead of Object pointers to aide with sweeping
 };