Adding fast path for generalizing maps.

src/objects.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 2791 matching lines @@
   // descriptor array.
   void CopyFrom(int dst_index,
                 DescriptorArray* src,
                 int src_index,
                 const WhitenessWitness&);
   MUST_USE_RESULT MaybeObject* Merge(int verbatim,
                                      int valid,
                                      int new_size,
                                      DescriptorArray* other);
 
+  bool IsMoreGeneralThan(int verbatim,
+                         int valid,
+                         int new_size,
+                         DescriptorArray* other);
+
   MUST_USE_RESULT MaybeObject* CopyUpTo(int enumeration_index);
 
   // Sort the instance descriptors by the hash codes of their keys.
   void Sort();
 
   // Search the instance descriptors for given name.
   INLINE(int Search(Name* name, int number_of_own_descriptors));
 
   // As the above, but uses DescriptorLookupCache and updates it when
   // necessary.
@@ skipping 6703 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_