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

src/contexts.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.
 
 #ifndef V8_CONTEXTS_H_
 #define V8_CONTEXTS_H_
 
 #include "src/heap/heap.h"
 #include "src/objects.h"
 
@@ skipping 245 matching lines @@
   V(MAP_CACHE_INDEX, Object, map_cache)                                        \
   V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map)                             \
   V(STRING_ITERATOR_MAP_INDEX, Map, string_iterator_map)                       \
   V(MATH_RANDOM_INDEX_INDEX, Smi, math_random_index)                           \
   V(MATH_RANDOM_CACHE_INDEX, Object, math_random_cache)                        \
   V(MESSAGE_LISTENERS_INDEX, TemplateList, message_listeners)                  \
   V(NATIVES_UTILS_OBJECT_INDEX, Object, natives_utils_object)                  \
   V(NORMALIZED_MAP_CACHE_INDEX, Object, normalized_map_cache)                  \
   V(NUMBER_FUNCTION_INDEX, JSFunction, number_function)                        \
   V(OBJECT_FUNCTION_INDEX, JSFunction, object_function)                        \
-  V(OBJECT_WITH_NULL_PROTOTYPE_MAP, Map, object_with_null_prototype_map)       \
+  V(SLOW_OBJECT_WITH_NULL_PROTOTYPE_MAP, Map,                                  \
+    slow_object_with_null_prototype_map)                                       \
   V(OBJECT_FUNCTION_PROTOTYPE_MAP_INDEX, Map, object_function_prototype_map)   \
   V(OPAQUE_REFERENCE_FUNCTION_INDEX, JSFunction, opaque_reference_function)    \
   V(PROXY_CALLABLE_MAP_INDEX, Map, proxy_callable_map)                         \
   V(PROXY_CONSTRUCTOR_MAP_INDEX, Map, proxy_constructor_map)                   \
   V(PROXY_FUNCTION_INDEX, JSFunction, proxy_function)                          \
   V(PROXY_FUNCTION_MAP_INDEX, Map, proxy_function_map)                         \
   V(PROXY_MAP_INDEX, Map, proxy_map)                                           \
   V(REGEXP_EXEC_FUNCTION_INDEX, JSFunction, regexp_exec_function)              \
   V(REGEXP_FUNCTION_INDEX, JSFunction, regexp_function)                        \
   V(REGEXP_LAST_MATCH_INFO_INDEX, RegExpMatchInfo, regexp_last_match_info)     \
@@ skipping 365 matching lines @@
   STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize);
   STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 };
 
 typedef Context::Field ContextField;
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CONTEXTS_H_