Create an abstraction for the string type flags so that they can be cached....

src/property.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 27 matching lines @@
 // optionally a piece of data.
 //
 
 class Descriptor BASE_EMBEDDED {
  public:
   static int IndexFromValue(Object* value) {
     return Smi::cast(value)->value();
   }
 
   Object* KeyToSymbol() {
-    if (!key_->IsSymbol()) {
+    if (!StringShape(key_).IsSymbol()) {
       Object* result = Heap::LookupSymbol(key_);
       if (result->IsFailure()) return result;
       key_ = String::cast(result);
     }
     return key_;
   }
 
   String* GetKey() { return key_; }
   Object* GetValue() { return value_; }
   PropertyDetails GetDetails() { return details_; }
@@ skipping 324 matching lines @@
 
   // Append a descriptor to this stream.
   void Write(Descriptor* desc);
   // Read a descriptor from the reader and append it to this stream.
   void WriteFrom(DescriptorReader* reader);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROPERTY_H_