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

Source/wtf/TypeTraits.h

Index: Source/wtf/TypeTraits.h
diff --git a/Source/wtf/TypeTraits.h b/Source/wtf/TypeTraits.h
index d89784a6eb32beeb3639d26881dd77bc4aaf0fc1..95254c4299a29ef0cc1f3306b8bac469ef8f495b 100644
--- a/Source/wtf/TypeTraits.h
+++ b/Source/wtf/TypeTraits.h
@@ -72,6 +72,11 @@ namespace WTF {
 
     template<typename T> struct IsWeak              { static const bool value = false; };
 
+    enum WeakHandlingFlag {
+        NoWeakHandlingInCollections,
+        WeakHandlingInCollections
+    };
+
     // IsPod is misnamed as it doesn't cover all plain old data (pod) types.
     // Specifically, it doesn't allow for enums or for structs.
     template <typename T> struct IsPod              { static const bool value = IsArithmetic<T>::value; };