Revert of Make DOMWrapperWorld::current() return a reference instead of a pointer

Source/bindings/v8/WorkerScriptController.h

 /*
  * Copyright (C) 2009, 2012 Google Inc. 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
@@ skipping 73 matching lines @@
         // or by Worker thread termination code to prevent future entry into JS.
         void forbidExecution();
         bool isExecutionForbidden() const;
 
         void disableEval(const String&);
 
         // Evaluate a script file in the current execution environment.
         ScriptValue evaluate(const String& script, const String& fileName, const TextPosition& scriptStartPosition, WorkerGlobalScopeExecutionState*);
 
         v8::Isolate* isolate() const { return m_isolate; }
-        DOMWrapperWorld& world() const { return *m_world; }
+        DOMWrapperWorld* world() const { return m_world.get(); }
         v8::Local<v8::Context> context() { return m_perContextData ? m_perContextData->context() : v8::Local<v8::Context>(); }
 
         // Send a notification about current thread is going to be idle.
         // Returns true if the embedder should stop calling idleNotification
         // until real work has been done.
         bool idleNotification() { return v8::V8::IdleNotification(); }
 
     private:
         bool initializeContextIfNeeded();
         void disposeContext();
 
         v8::Isolate* m_isolate;
         WorkerGlobalScope& m_workerGlobalScope;
         OwnPtr<V8PerContextData> m_perContextData;
         String m_disableEvalPending;
         RefPtr<DOMWrapperWorld> m_world;
         bool m_executionForbidden;
         bool m_executionScheduledToTerminate;
         mutable Mutex m_scheduledTerminationMutex;
         RefPtr<ErrorEvent> m_errorEventFromImportedScript;
         OwnPtr<V8IsolateInterruptor> m_interruptor;
     };
 
 } // namespace WebCore
 
 #endif // WorkerScriptController_h