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

src/transitions-inl.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 70 matching lines @@
 }
 
 
 FixedArray* TransitionArray::GetPrototypeTransitions() {
   ASSERT(IsFullTransitionArray());
   Object* prototype_transitions = get(kPrototypeTransitionsIndex);
   return FixedArray::cast(prototype_transitions);
 }
 
 
-HeapObject* TransitionArray::UncheckedPrototypeTransitions() {
-  ASSERT(HasPrototypeTransitions());
-  return reinterpret_cast<HeapObject*>(get(kPrototypeTransitionsIndex));
-}
-
-
 void TransitionArray::SetPrototypeTransitions(FixedArray* transitions,
                                               WriteBarrierMode mode) {
   ASSERT(IsFullTransitionArray());
   ASSERT(transitions->IsFixedArray());
   Heap* heap = GetHeap();
   WRITE_FIELD(this, kPrototypeTransitionsOffset, transitions);
   CONDITIONAL_WRITE_BARRIER(
       heap, this, kPrototypeTransitionsOffset, transitions, mode);
 }
 
@@ skipping 77 matching lines @@
 
 
 #undef FIELD_ADDR
 #undef WRITE_FIELD
 #undef CONDITIONAL_WRITE_BARRIER
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TRANSITIONS_INL_H_