Oilpan:Allow custom handling of classes that contain weak pointers that are embedded in collections.

Source/wtf/HashTraits.h

 /*
  * Copyright (C) 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  *
  * 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 46 matching lines @@
         static const unsigned minimumTableSize = 1;
 #else
         static const unsigned minimumTableSize = 8;
 #endif
 
         template<typename U = void>
         struct NeedsTracingLazily {
             static const bool value = NeedsTracing<T>::value;
         };
         static const bool isWeak = IsWeak<T>::value;
+        template<typename Visitor>
+        static bool shouldRemoveFromCollection(Visitor*, T&) { return false; }
     };
 
     // Default integer traits disallow both 0 and -1 as keys (max value instead of -1 for unsigned).
     template<typename T> struct GenericHashTraitsBase<true, T> : GenericHashTraitsBase<false, T> {
         static const bool emptyValueIsZero = true;
         static const bool needsDestruction = false;
         static void constructDeletedValue(T& slot) { slot = static_cast<T>(-1); }
         static bool isDeletedValue(T value) { return value == static_cast<T>(-1); }
     };
 
@@ skipping 192 matching lines @@
         template<typename U = void>
         struct NeedsTracingLazily {
             static const bool value = ShouldBeTraced<KeyTraits>::value || ShouldBeTraced<ValueTraits>::value;
         };
         static const bool isWeak = KeyTraits::isWeak || ValueTraits::isWeak;
 
         static const unsigned minimumTableSize = KeyTraits::minimumTableSize;
 
         static void constructDeletedValue(TraitType& slot) { KeyTraits::constructDeletedValue(slot.key); }
         static bool isDeletedValue(const TraitType& value) { return KeyTraits::isDeletedValue(value.key); }
+        template<typename Visitor>
+        static bool shouldRemoveFromCollection(Visitor* visitor, TraitType& pair)
+        {
+            return KeyTraits::shouldRemoveFromCollection(visitor, pair.key)
+                || ValueTraits::shouldRemoveFromCollection(visitor, pair.value);
+        }
     };
 
     template<typename Key, typename Value>
     struct HashTraits<KeyValuePair<Key, Value> > : public KeyValuePairHashTraits<HashTraits<Key>, HashTraits<Value> > { };
 
     template<typename T>
     struct NullableHashTraits : public HashTraits<T> {
         static const bool emptyValueIsZero = false;
         static T emptyValue() { return reinterpret_cast<T>(1); }
     };
 
 } // namespace WTF
 
 using WTF::HashTraits;
 using WTF::PairHashTraits;
 using WTF::NullableHashTraits;
 using WTF::SimpleClassHashTraits;
 
 #endif // WTF_HashTraits_h