[runtime] Object.create(null) creates a slow object

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 7557 matching lines @@
   if (map()->is_dictionary_map()) {
     WRITE_FIELD(this, kPropertiesOffset,
                 GetHeap()->empty_properties_dictionary());
   } else {
     WRITE_FIELD(this, kPropertiesOffset, GetHeap()->empty_fixed_array());
   }
 }
 
 
 bool JSReceiver::HasFastProperties() {
-  DCHECK(properties()->IsDictionary() == map()->is_dictionary_map());
+  DCHECK_EQ(properties()->IsDictionary(), map()->is_dictionary_map());
   return !properties()->IsDictionary();
 }
 
 
 NameDictionary* JSReceiver::property_dictionary() {
   DCHECK(!HasFastProperties());
   DCHECK(!IsJSGlobalObject());
   return NameDictionary::cast(properties());
 }
 
@@ skipping 825 matching lines @@
 #undef WRITE_INT64_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_INL_H_