Fix map modification in transition tree traversal.

src/objects.h

 // Copyright 2011 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 1109 matching lines @@
 
 
 // HeapObject is the superclass for all classes describing heap allocated
 // objects.
 class HeapObject: public Object {
  public:
   // [map]: Contains a map which contains the object's reflective
   // information.
   inline Map* map();
   inline void set_map(Map* value);
+  inline void set_map_unsafe(Map* value);
 
   // During garbage collection, the map word of a heap object does not
   // necessarily contain a map pointer.
   inline MapWord map_word();
   inline void set_map_word(MapWord map_word);
 
   // The Heap the object was allocated in. Used also to access Isolate.
   inline Heap* GetHeap();
 
   // Convenience method to get current isolate. This method can be
@@ skipping 6428 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_