Make sure that NormalizeElements and ShouldConvertToFastElements are based on the same values

src/objects.cc

 // Copyright 2013 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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 14628 matching lines @@
     Object* length = JSArray::cast(object)->length();
     if (!length->IsSmi()) return false;
     *new_capacity = static_cast<uint32_t>(Smi::cast(length)->value());
   } else {
     *new_capacity = dictionary->max_number_key() + 1;
   }
   *new_capacity = Max(index + 1, *new_capacity);
 
   uint32_t dictionary_size = static_cast<uint32_t>(dictionary->Capacity()) *
                              SeededNumberDictionary::kEntrySize;
+
+  // Turn fast if the dictionary only saves 50% space.
   return 2 * dictionary_size >= *new_capacity;
 }
 
 
 // static
 MaybeHandle<Object> JSObject::AddDataElement(Handle<JSObject> object,
                                              uint32_t index,
                                              Handle<Object> value,
                                              PropertyAttributes attributes) {
   MAYBE_RETURN_NULL(
@@ skipping 3882 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8