Preserve constant function transition when adding the same function.

src/objects-inl.h

 // Copyright 2006-2008 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 1475 matching lines @@
   const int kMaxElementsForLinearSearch = 8;
   if (StringShape(name).IsSymbol() && nof < kMaxElementsForLinearSearch) {
     return LinearSearch(name, nof);
   }
 
   // Slow case: perform binary search.
   return BinarySearch(name, 0, nof - 1);
 }
 
 
+int DescriptorArray::SearchWithCache(String* name) {
+  int number = DescriptorLookupCache::Lookup(this, name);
+  if (number == DescriptorLookupCache::kAbsent) {
+    number = Search(name);
+    DescriptorLookupCache::Update(this, name, number);
+  }
+  return number;
+}
+
+
 String* DescriptorArray::GetKey(int descriptor_number) {
   ASSERT(descriptor_number < number_of_descriptors());
   return String::cast(get(ToKeyIndex(descriptor_number)));
 }
 
 
 Object* DescriptorArray::GetValue(int descriptor_number) {
   ASSERT(descriptor_number < number_of_descriptors());
   return GetContentArray()->get(ToValueIndex(descriptor_number));
 }
@@ skipping 1819 matching lines @@
 #undef WRITE_INT_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_