Preserve constant function transition when adding the same function.

src/objects.h

 // Copyright 2006-2009 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 1793 matching lines @@
   // Remove all transitions.  Return  a copy of the array with all transitions
   // removed, or a Failure object if the new array could not be allocated.
   Object* RemoveTransitions();
 
   // Sort the instance descriptors by the hash codes of their keys.
   void Sort();
 
   // Search the instance descriptors for given name.
   inline int Search(String* name);
 
+  // As the above, but uses DescriptorLookupCache and updates it when
+  // necessary.
+  inline int SearchWithCache(String* name);
+
   // Tells whether the name is present int the array.
   bool Contains(String* name) { return kNotFound != Search(name); }
 
   // Perform a binary search in the instance descriptors represented
   // by this fixed array.  low and high are descriptor indices.  If there
   // are three instance descriptors in this array it should be called
   // with low=0 and high=2.
   int BinarySearch(String* name, int low, int high);
 
   // Perform a linear search in the instance descriptors represented
@@ skipping 3543 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_