[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 9e8b06c6fc467e8ca7668d039df96b29a9f9c4eb..dc403d90b049390354bb824ba39e1a98a7a226dd 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);
@@ -16774,7 +16775,8 @@ 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,
+                 base::bits::IsPowerOfTwo32(at_least_space_for));
 
   int capacity = (capacity_option == USE_CUSTOM_MINIMUM_CAPACITY)
                      ? at_least_space_for