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

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 7c46f800e48df19b780a8119ad70cd3f182e45b0..03e17e8187652393a2a9b4695978787d9f1c683c 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3432,7 +3432,8 @@ void MigrateFastToSlow(Handle<JSObject> object, Handle<Map> new_map,
   if (expected_additional_properties > 0) {
     property_count += expected_additional_properties;
   } else {
-    property_count += 2;  // Make space for two more properties.
+    // Make space for two more properties.
+    property_count += NameDictionary::kInitialCapacity;
   }
   Handle<NameDictionary> dictionary =
       NameDictionary::New(isolate, property_count);
@@ -16769,7 +16770,8 @@ Handle<Derived> HashTable<Derived, Shape, Key>::New(
     MinimumCapacity capacity_option,
     PretenureFlag pretenure) {
   DCHECK(0 <= at_least_space_for);
-  DCHECK(!capacity_option || base::bits::IsPowerOfTwo32(at_least_space_for));
+  DCHECK_IMPLIES(capacity_option == USE_CUSTOM_MINIMUM_CAPACITY,

[Igor Sheludko, 2016/10/21 07:48:27]

FYI: USE_CUSTOM_MINIMUM_CAPACITY does not actually work because whenever you add
anything to the dictionary EnsureCapacity() will reallocate it to at least
USE_DEFAULT_MINIMUM_CAPACITY.

+                 base::bits::IsPowerOfTwo32(at_least_space_for));
 
   int capacity = (capacity_option == USE_CUSTOM_MINIMUM_CAPACITY)
                      ? at_least_space_for