Make message listener API backwards compatible.

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 114 matching lines @@
   int global_length = global_listeners.length();
   if (global_length == 0) {
     DefaultMessageReport(loc, message);
     if (isolate->has_scheduled_exception()) {
       isolate->clear_scheduled_exception();
     }
   } else {
     for (int i = 0; i < global_length; i++) {
       HandleScope scope;
       if (global_listeners.get(i)->IsUndefined()) continue;
-      Handle<Foreign> callback_obj(Foreign::cast(global_listeners.get(i)));
+      v8::NeanderObject listener(JSObject::cast(global_listeners.get(i)));
+      Handle<Foreign> callback_obj(Foreign::cast(listener.get(0)));
       v8::MessageCallback callback =
           FUNCTION_CAST<v8::MessageCallback>(callback_obj->foreign_address());
+      Handle<Object> callback_data(listener.get(1));
       {
         // Do not allow exceptions to propagate.
         v8::TryCatch try_catch;
-        callback(api_message_obj, api_exception_obj);
+        callback(api_message_obj, callback_data->IsUndefined()
+                                      ? api_exception_obj
+                                      : v8::Utils::ToLocal(callback_data));
       }
       if (isolate->has_scheduled_exception()) {
         isolate->clear_scheduled_exception();
       }
     }
   }
 }
 
 
 Handle<String> MessageHandler::GetMessage(Handle<Object> data) {
@@ skipping 31 matching lines @@
 
 
 SmartArrayPointer<char> MessageHandler::GetLocalizedMessage(
     Handle<Object> data) {
   HandleScope scope;
   return GetMessage(data)->ToCString(DISALLOW_NULLS);
 }
 
 
 } }  // namespace v8::internal