Use macros instead of specializing VectorTraits explicitly

Source/wtf/VectorTraits.h

Index: Source/wtf/VectorTraits.h
diff --git a/Source/wtf/VectorTraits.h b/Source/wtf/VectorTraits.h
index fe54ffe3fa512047f6d87099c530c75d452f40de..d93fa516f38fc626a14484cd98b58941aa2f3df1 100644
--- a/Source/wtf/VectorTraits.h
+++ b/Source/wtf/VectorTraits.h
@@ -100,6 +100,16 @@ namespace WTF { \
     struct VectorTraits<ClassName> : SimpleClassVectorTraits<ClassName> { }; \
 }
 
+#define WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(ClassName) \
+namespace WTF { \
+    template<> \
+    struct VectorTraits<ClassName> : VectorTraitsBase<ClassName> \
+    { \
+        static const bool canInitializeWithMemset = true; \
+        static const bool canMoveWithMemcpy = true; \
+    }; \
+}
+
 using WTF::VectorTraits;
 using WTF::SimpleClassVectorTraits;