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

Source/platform/heap/Heap.cpp

Index: Source/platform/heap/Heap.cpp
diff --git a/Source/platform/heap/Heap.cpp b/Source/platform/heap/Heap.cpp
index a25225c2bec962e07edfa8b4c754650f1be0cf4e..59121dcb7d43e6d97a10535b503f696939e4e7c3 100644
--- a/Source/platform/heap/Heap.cpp
+++ b/Source/platform/heap/Heap.cpp
@@ -1851,6 +1851,9 @@ public:
 
     MarkingVisitor()
         : Visitor(Mode == GlobalMarking ? Visitor::GlobalMarkingVisitorType : Visitor::GenericVisitorType)
+#if ENABLE(ASSERT)
+        , m_allowMarkingForHashTableWeakProcessing(false)
+#endif
     {
     }
 
@@ -2023,6 +2026,20 @@ protected:
         // does, the object should not be marked & traced.
         return page->terminating();
     }
+
+#if ENABLE(ASSERT)
+    virtual void checkMarkingAllowed() override
+    {
+        ASSERT(ThreadState::current()->isInGC() || m_allowMarkingForHashTableWeakProcessing);
+    }
+
+    virtual void setAllowMarkingForHashTableWeakProcessing(bool allow) override
+    {
+        m_allowMarkingForHashTableWeakProcessing = allow;
+    }
+
+    bool m_allowMarkingForHashTableWeakProcessing;
+#endif
 };
 
 void Heap::init()