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

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 1381 matching lines @@
     if (!m_frame->script().canExecuteScripts(NotAboutToExecuteScript))
         return;
 
     if (Page* page = m_frame->page())
         page->inspectorController().didClearWindowObjectInMainWorld(m_frame);
     InspectorInstrumentation::didClearWindowObjectInMainWorld(m_frame);
 
     Vector<RefPtr<DOMWrapperWorld> > worlds;
     DOMWrapperWorld::allWorldsInMainThread(worlds);
     for (size_t i = 0; i < worlds.size(); ++i)
-        m_client->dispatchDidClearWindowObjectInWorld(*worlds[i]);
+        m_client->dispatchDidClearWindowObjectInWorld(worlds[i].get());
 }
 
-void FrameLoader::dispatchDidClearWindowObjectInWorld(DOMWrapperWorld& world)
+void FrameLoader::dispatchDidClearWindowObjectInWorld(DOMWrapperWorld* world)
 {
     if (!m_frame->script().canExecuteScripts(NotAboutToExecuteScript) || !m_frame->script().existingWindowShell(world))
         return;
 
     m_client->dispatchDidClearWindowObjectInWorld(world);
 }
 
 SandboxFlags FrameLoader::effectiveSandboxFlags() const
 {
     SandboxFlags flags = m_forcedSandboxFlags;
     if (LocalFrame* parentFrame = m_frame->tree().parent())
         flags |= parentFrame->document()->sandboxFlags();
     if (HTMLFrameOwnerElement* ownerElement = m_frame->ownerElement())
         flags |= ownerElement->sandboxFlags();
     return flags;
 }
 
 } // namespace WebCore