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

Source/web/FrameLoaderClientImpl.cpp

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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.
@@ skipping 92 matching lines @@
 
 FrameLoaderClientImpl::FrameLoaderClientImpl(WebFrameImpl* frame)
     : m_webFrame(frame)
 {
 }
 
 FrameLoaderClientImpl::~FrameLoaderClientImpl()
 {
 }
 
-void FrameLoaderClientImpl::dispatchDidClearWindowObjectInWorld(DOMWrapperWorld& world)
+void FrameLoaderClientImpl::dispatchDidClearWindowObjectInWorld(DOMWrapperWorld* world)
 {
     if (m_webFrame->client()) {
-        m_webFrame->client()->didClearWindowObject(m_webFrame, world.worldId());
+        m_webFrame->client()->didClearWindowObject(m_webFrame, world->worldId());
         Document* document = m_webFrame->frame()->document();
         if (document) {
             WheelController::from(*document);
             if (RuntimeEnabledFeatures::deviceMotionEnabled())
                 DeviceMotionController::from(*document);
             if (RuntimeEnabledFeatures::deviceOrientationEnabled())
                 DeviceOrientationController::from(*document);
             if (RuntimeEnabledFeatures::screenOrientationEnabled())
                 ScreenOrientationController::from(*document);
             if (RuntimeEnabledFeatures::gamepadEnabled())
@@ skipping 667 matching lines @@
     return adoptPtr(m_webFrame->client()->createApplicationCacheHost(m_webFrame, client));
 }
 
 void FrameLoaderClientImpl::didStopAllLoaders()
 {
     if (m_webFrame->client())
         m_webFrame->client()->didAbortLoading(m_webFrame);
 }
 
 } // namespace blink