Implement handlified String::Flatten.

src/messages.cc

 // Copyright 2011 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 162 matching lines @@
 
   if (caught_exception || !result->IsString()) {
     return factory->InternalizeOneByteString(STATIC_ASCII_VECTOR("<error>"));
   }
   Handle<String> result_string = Handle<String>::cast(result);
   // A string that has been obtained from JS code in this way is
   // likely to be a complicated ConsString of some sort.  We flatten it
   // here to improve the efficiency of converting it to a C string and
   // other operations that are likely to take place (see GetLocalizedMessage
   // for example).
-  FlattenString(result_string);
+  result_string = String::Flatten(result_string);
   return result_string;
 }
 
 
 SmartArrayPointer<char> MessageHandler::GetLocalizedMessage(
     Isolate* isolate,
     Handle<Object> data) {
   HandleScope scope(isolate);
   return GetMessage(isolate, data)->ToCString(DISALLOW_NULLS);
 }
 
 
 } }  // namespace v8::internal