Add infrastructure to keep track of references to prototypes.

src/lookup.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/v8.h"
 
 #include "src/bootstrapper.h"
 #include "src/deoptimizer.h"
 #include "src/lookup.h"
 #include "src/lookup-inl.h"
@@ skipping 109 matching lines @@
   if (state_ == TRANSITION) return;
   DCHECK(state_ != LookupIterator::ACCESSOR ||
          GetAccessors()->IsDeclaredAccessorInfo());
   DCHECK(state_ == NOT_FOUND || !HolderIsReceiverOrHiddenPrototype());
 
   // Can only be called when the receiver is a JSObject. JSProxy has to be
   // handled via a trap. Adding properties to primitive values is not
   // observable.
   Handle<JSObject> receiver = GetStoreTarget();
 
-  if (!name().is_identical_to(isolate()->factory()->hidden_string()) &&
+  if (!isolate()->IsInternallyUsedPropertyName(name()) &&
       !receiver->map()->is_extensible()) {
     return;
   }
 
   transition_map_ = Map::TransitionToDataProperty(
       handle(receiver->map(), isolate_), name_, value, attributes, store_mode);
   state_ = TRANSITION;
 }
 
 
@@ skipping 189 matching lines @@
   }
   return false;
 }
 
 
 void LookupIterator::InternalizeName() {
   if (name_->IsUniqueName()) return;
   name_ = factory()->InternalizeString(Handle<String>::cast(name_));
 }
 } }  // namespace v8::internal