Don't overwrite transition array map while iterating over the transition tree.

src/transitions-inl.h

Index: src/transitions-inl.h
diff --git a/src/transitions-inl.h b/src/transitions-inl.h
index dc1620a07dd6ea192f65d1efbbb4b20ff0a93254..63a6c38c79020c2e437c013194beee5dd01fb60f 100644
--- a/src/transitions-inl.h
+++ b/src/transitions-inl.h
@@ -88,12 +88,6 @@ FixedArray* TransitionArray::GetPrototypeTransitions() {
 }
 
 
-HeapObject* TransitionArray::UncheckedPrototypeTransitions() {
-  ASSERT(HasPrototypeTransitions());
-  return reinterpret_cast<HeapObject*>(get(kPrototypeTransitionsIndex));
-}
-
-
 void TransitionArray::SetPrototypeTransitions(FixedArray* transitions,
                                               WriteBarrierMode mode) {
   ASSERT(IsFullTransitionArray());