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

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 98bf122a2eef33bd2aaf72214ba18a40b8d73ae5..560fd8be42a96622704fb37178c8c1c9821e1116 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -6143,9 +6143,6 @@ class Map: public HeapObject {
       FixedArray* prototype_transitions);
   inline bool HasPrototypeTransitions();
 
-  inline HeapObject* UncheckedPrototypeTransitions();
-  inline TransitionArray* unchecked_transition_array();
-
   static const int kProtoTransitionHeaderSize = 1;
   static const int kProtoTransitionNumberOfEntriesOffset = 0;
   static const int kProtoTransitionElementsPerEntry = 2;