Speed up creation of Objects whose prototype has dictionary elements

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 <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 11778 matching lines @@
   if (value->IsJSObject()) {
     PrototypeOptimizationMode mode =
         from_javascript ? REGULAR_PROTOTYPE : FAST_PROTOTYPE;
     JSObject::OptimizeAsPrototype(Handle<JSObject>::cast(value), mode);
   }
 
   Handle<Map> new_map = Map::TransitionToPrototype(map, value);
   DCHECK(new_map->prototype() == *value);
   JSObject::MigrateToMap(real_receiver, new_map);
 
-  if (!dictionary_elements_in_chain &&
+  if (from_javascript && !dictionary_elements_in_chain &&
       new_map->DictionaryElementsInPrototypeChainOnly()) {
     // If the prototype chain didn't previously have element callbacks, then
     // KeyedStoreICs need to be cleared to ensure any that involve this
     // map go generic.
     object->GetHeap()->ClearAllICsByKind(Code::KEYED_STORE_IC);
   }
 
   heap->ClearInstanceofCache();
   DCHECK(size == object->Size());
   return value;
@@ skipping 4659 matching lines @@
   Handle<DependentCode> codes =
       DependentCode::Insert(handle(cell->dependent_code(), info->isolate()),
                             DependentCode::kPropertyCellChangedGroup,
                             info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal