Directly store the transition target on LookupResult in TransitionResult.

src/objects-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 2479 matching lines @@
 
   if (number == DescriptorLookupCache::kAbsent) {
     number = Search(name, number_of_own_descriptors);
     cache->Update(map, name, number);
   }
 
   return number;
 }
 
 
+PropertyDetails Map::GetLastDescriptorDetails() {
+  return instance_descriptors()->GetDetails(LastAdded());
+}
+
+
 void Map::LookupDescriptor(JSObject* holder,
                            Name* name,
                            LookupResult* result) {
   DescriptorArray* descriptors = this->instance_descriptors();
   int number = descriptors->SearchWithCache(name, this);
   if (number == DescriptorArray::kNotFound) return result->NotFound();
   result->DescriptorResult(holder, descriptors->GetDetails(number), number);
 }
 
 
 void Map::LookupTransition(JSObject* holder,
                            Name* name,
                            LookupResult* result) {
   if (HasTransitionArray()) {
     TransitionArray* transition_array = transitions();
     int number = transition_array->Search(name);
     if (number != TransitionArray::kNotFound) {
-      return result->TransitionResult(holder, number);
+      return result->TransitionResult(
+          holder, transition_array->GetTarget(number));
     }
   }
   result->NotFound();
 }
 
 
 Object** DescriptorArray::GetKeySlot(int descriptor_number) {
   ASSERT(descriptor_number < number_of_descriptors());
   return RawFieldOfElementAt(ToKeyIndex(descriptor_number));
 }
@@ skipping 4211 matching lines @@
 #undef READ_UINT32_FIELD
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_