Change RefPtr<DOMWrapperWorld> that causes reference cycles to DOMWrapperWorld*

Source/bindings/v8/V8MutationCallback.cpp

 /*
  * Copyright (C) 2013 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 34 matching lines @@
     m_callback.setWeak(this, &setWeakCallback);
 }
 
 void V8MutationCallback::call(const Vector<RefPtr<MutationRecord> >& mutations, MutationObserver* observer)
 {
     if (!canInvokeCallback())
         return;
 
     v8::HandleScope handleScope(m_isolate);
 
-    v8::Handle<v8::Context> v8Context = toV8Context(executionContext(), m_world.get());
+    v8::Handle<v8::Context> v8Context = toV8Context(executionContext(), m_world);
     if (v8Context.IsEmpty())
         return;
 
     v8::Context::Scope scope(v8Context);
 
     v8::Handle<v8::Function> callback = m_callback.newLocal(m_isolate);
     if (callback.IsEmpty())
         return;
 
     v8::Handle<v8::Value> observerHandle = toV8(observer, v8::Handle<v8::Object>(), m_isolate);
@@ skipping 13 matching lines @@
     exceptionCatcher.SetVerbose(true);
     ScriptController::callFunction(executionContext(), callback, thisObject, 2, argv, m_isolate);
 }
 
 void V8MutationCallback::setWeakCallback(const v8::WeakCallbackData<v8::Function, V8MutationCallback>& data)
 {
     data.GetParameter()->m_callback.clear();
 }
 
 } // namespace WebCore