Introduce a macro enabling 'SimpleClassVectorTraits'

Source/wtf/VectorTraits.h

Index: Source/wtf/VectorTraits.h
diff --git a/Source/wtf/VectorTraits.h b/Source/wtf/VectorTraits.h
index 74cc1d8fbd15a969901c3334782e64045bfcb415..fe54ffe3fa512047f6d87099c530c75d452f40de 100644
--- a/Source/wtf/VectorTraits.h
+++ b/Source/wtf/VectorTraits.h
@@ -52,6 +52,9 @@ namespace WTF {
     template<typename T>
     struct VectorTraits : VectorTraitsBase<T> { };
 
+    // Classes marked with SimpleVectorTraits will use memmov, memcpy, memcmp
+    // instead of constructors, copy operators, etc for initialization, move
+    // and comparison.
     template<typename T>
     struct SimpleClassVectorTraits : VectorTraitsBase<T>
     {
@@ -91,6 +94,12 @@ namespace WTF {
 
 } // namespace WTF
 
+#define WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(ClassName) \
+namespace WTF { \
+    template<> \
+    struct VectorTraits<ClassName> : SimpleClassVectorTraits<ClassName> { }; \
+}
+
 using WTF::VectorTraits;
 using WTF::SimpleClassVectorTraits;