Use NumberOfOwnDescriptors/EnumLength for counting properties on fast objects.

src/heap.cc

 // 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 4171 matching lines @@
 
   // Initial size of the backing store to avoid resize of the storage during
   // bootstrapping. The size differs between the JS global object ad the
   // builtins object.
   int initial_size = map->instance_type() == JS_GLOBAL_OBJECT_TYPE ? 64 : 512;
 
   // Allocate a dictionary object for backing storage.
   StringDictionary* dictionary;
   MaybeObject* maybe_dictionary =
       StringDictionary::Allocate(
-          map->NumberOfDescribedProperties() * 2 + initial_size);
+          map->NumberOfOwnDescriptors() * 2 + initial_size);
   if (!maybe_dictionary->To(&dictionary)) return maybe_dictionary;
 
   // The global object might be created from an object template with accessors.
   // Fill these accessors into the dictionary.
   DescriptorArray* descs = map->instance_descriptors();
   for (int i = 0; i < descs->number_of_descriptors(); i++) {
     PropertyDetails details = descs->GetDetails(i);
     ASSERT(details.type() == CALLBACKS);  // Only accessors are expected.
     PropertyDetails d = PropertyDetails(details.attributes(),
                                         CALLBACKS,
@@ skipping 3117 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal