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

src/bootstrapper.cc

 // Copyright 2014 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.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/base/ieee754.h"
 #include "src/code-stubs.h"
@@ skipping 3510 matching lines @@
 
   // Store the map for the %ObjectPrototype% after the natives has been compiled
   // and the Object function has been set up.
   Handle<JSFunction> object_function(native_context()->object_function());
   DCHECK(JSObject::cast(object_function->initial_map()->prototype())
              ->HasFastProperties());
   native_context()->set_object_function_prototype_map(
       HeapObject::cast(object_function->initial_map()->prototype())->map());
 
   // Set up the map for Object.create(null) instances.
-  Handle<Map> object_with_null_prototype_map =
+  Handle<Map> slow_object_with_null_prototype_map =
       Map::CopyInitialMap(handle(object_function->initial_map(), isolate()));
-  Map::SetPrototype(object_with_null_prototype_map,
+  slow_object_with_null_prototype_map->set_dictionary_map(true);
+  Map::SetPrototype(slow_object_with_null_prototype_map,
                     isolate()->factory()->null_value());
-  native_context()->set_object_with_null_prototype_map(
-      *object_with_null_prototype_map);
+  native_context()->set_slow_object_with_null_prototype_map(
+      *slow_object_with_null_prototype_map);
 
   // Store the map for the %StringPrototype% after the natives has been compiled
   // and the String function has been set up.
   Handle<JSFunction> string_function(native_context()->string_function());
   DCHECK(JSObject::cast(
       string_function->initial_map()->prototype())->HasFastProperties());
   native_context()->set_string_function_prototype_map(
       HeapObject::cast(string_function->initial_map()->prototype())->map());
 
   Handle<JSGlobalObject> global_object =
@@ skipping 1025 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8