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

Source/wtf/HashTable.h

 /*
  * Copyright (C) 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008 David Levin <levin@chromium.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 1238 matching lines @@
                 ASSERT(visitor->isAlive(table->m_table));
                 // Now perform weak processing (this is a no-op if the backing
                 // was accessible through an iterator and was already marked
                 // strongly).
                 typedef typename HashTableType::ValueType ValueType;
                 for (ValueType* element = table->m_table + table->m_tableSize - 1; element >= table->m_table; element--) {
                     if (!HashTableType::isEmptyOrDeletedBucket(*element)) {
                         // At this stage calling trace can make no difference
                         // (everything is already traced), but we use the
                         // return value to remove things from the collection.
-                        if (TraceInCollectionTrait<WeakHandlingInCollections, WeakPointersActWeak, ValueType, Traits>::trace(visitor, *element)) {
+
+                        // FIXME: This should be rewritten so that this can check
+                        // if the element is dead without calling trace,
+                        // which is semantically not correct to be called in
+                        // weak processing stage.
+#if ENABLE(ASSERT)
+                        visitor->setAllowMarkingForHashTableWeakProcessing(true);
+#endif
+                        bool elementIsDead = TraceInCollectionTrait<WeakHandlingInCollections, WeakPointersActWeak, ValueType, Traits>::trace(visitor, *element);
+#if ENABLE(ASSERT)
+                        visitor->setAllowMarkingForHashTableWeakProcessing(false);
+#endif
+                        if (elementIsDead) {
                             table->registerModification();
                             HashTableType::deleteBucket(*element); // Also calls the destructor.
                             table->m_deletedCount++;
                             table->m_keyCount--;
                             // We don't rehash the backing until the next add
                             // or delete, because that would cause allocation
                             // during GC.
                         }
                     }
                 }
@@ skipping 185 matching lines @@
         CollectionIterator end(toBeRemoved.end());
         for (CollectionIterator it(toBeRemoved.begin()); it != end; ++it)
             collection.remove(*it);
     }
 
 } // namespace WTF
 
 #include "wtf/HashIterators.h"
 
 #endif // WTF_HashTable_h