Create HeapLinkedHashSet and LinkedHashSet, ordered heap-friendly hash sets.

Source/heap/Visitor.h

Index: Source/heap/Visitor.h
diff --git a/Source/heap/Visitor.h b/Source/heap/Visitor.h
index 4d52a0368166e6915a8deb84de796f9f2ac4132d..92f92de30d8dfb15c89773dc268ad408039d56d8 100644
--- a/Source/heap/Visitor.h
+++ b/Source/heap/Visitor.h
@@ -39,6 +39,7 @@
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/HashTraits.h"
+#include "wtf/LinkedHashSet.h"
 #include "wtf/ListHashSet.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/RefPtr.h"
@@ -262,6 +263,12 @@ public:
         OffHeapCollectionTraceTrait<ListHashSet<T, inlineCapacity, U> >::trace(this, hashSet);
     }
 
+    template<typename T, typename U>
+    void trace(const LinkedHashSet<T, U>& hashSet)
+    {
+        OffHeapCollectionTraceTrait<LinkedHashSet<T, U> >::trace(this, hashSet);
+    }
+
     template<typename T, size_t N>
     void trace(const Deque<T, N>& deque)
     {
@@ -427,6 +434,20 @@ struct OffHeapCollectionTraceTrait<WTF::ListHashSet<T, inlineCapacity, HashFunct
     }
 };
 
+template<typename T, typename HashFunctions>
+struct OffHeapCollectionTraceTrait<WTF::LinkedHashSet<T, HashFunctions> > {
+    typedef WTF::LinkedHashSet<T, HashFunctions> LinkedHashSet;
+
+    static void trace(Visitor* visitor, const LinkedHashSet& set)
+    {
+        if (set.isEmpty())
+            return;
+        LinkedHashSet& iterSet = const_cast<LinkedHashSet&>(set);
+        for (typename LinkedHashSet::iterator it = iterSet.begin(), end = iterSet.end(); it != end; ++it)
+            visitor->trace(*it);
+    }
+};
+
 template<typename Key, typename Value, typename HashFunctions, typename KeyTraits, typename ValueTraits>
 struct OffHeapCollectionTraceTrait<WTF::HashMap<Key, Value, HashFunctions, KeyTraits, ValueTraits, WTF::DefaultAllocator> > {
     typedef WTF::HashMap<Key, Value, HashFunctions, KeyTraits, ValueTraits, WTF::DefaultAllocator> HashMap;