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

src/transitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 67 matching lines @@
   inline void set_back_pointer_storage(
       Object* back_pointer,
       WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
 
   inline FixedArray* GetPrototypeTransitions();
   inline void SetPrototypeTransitions(
       FixedArray* prototype_transitions,
       WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
   inline Object** GetPrototypeTransitionsSlot();
   inline bool HasPrototypeTransitions();
-  inline HeapObject* UncheckedPrototypeTransitions();
 
   // Returns the number of transitions in the array.
   int number_of_transitions() {
     if (IsSimpleTransition()) return 1;
     int len = length();
     return len <= kFirstIndex ? 0 : (len - kFirstIndex) / kTransitionSize;
   }
 
   inline int number_of_entries() { return number_of_transitions(); }
 
@@ skipping 104 matching lines @@
                                            Name* key,
                                            Map* target);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TransitionArray);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TRANSITIONS_H_