ASSERT that Visitor::mark is only called when inGC()

Source/platform/heap/Visitor.h

Index: Source/platform/heap/Visitor.h
diff --git a/Source/platform/heap/Visitor.h b/Source/platform/heap/Visitor.h
index d000afcb73de51916524129c0cf529201cb7a355..e4c51f7a0ba6cd65304fec4b5a09b65c52f2299f 100644
--- a/Source/platform/heap/Visitor.h
+++ b/Source/platform/heap/Visitor.h
@@ -344,6 +344,7 @@ public:
             return;
 #if ENABLE(ASSERT)
         TraceTrait<T>::checkGCInfo(t);
+        Derived::fromHelper(this)->checkMarkingAllowed();
 #endif
         TraceTrait<T>::mark(Derived::fromHelper(this), t);
 
@@ -632,6 +633,10 @@ public:
 
     inline bool isGlobalMarkingVisitor() const { return m_isGlobalMarkingVisitor; }
 
+#if ENABLE(ASSERT)
+    virtual void setAllowMarkingForHashTableWeakProcessing(bool) { }
+#endif
+
 protected:
     explicit Visitor(VisitorType type)
         : m_isGlobalMarkingVisitor(type == GlobalMarkingVisitorType)
@@ -650,6 +655,10 @@ protected:
     String m_hostName;
 #endif
 
+#if ENABLE(ASSERT)
+    virtual void checkMarkingAllowed() { }
+#endif
+
 private:
     static Visitor* fromHelper(VisitorHelper<Visitor>* helper) { return static_cast<Visitor*>(helper); }