Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/page/HistoryController.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 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/)
  *
  * 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
@@ skipping 212 matching lines @@
         historyNode->value()->clearChildren();
     }
     goToEntry(newEntry.release(), cachePolicy);
 }
 
 void HistoryController::setDefersLoading(bool defer)
 {
     m_defersLoading = defer;
     if (!defer && m_deferredItem) {
         goToItem(m_deferredItem.get(), m_deferredCachePolicy);
-        m_deferredItem = 0;
+        m_deferredItem = nullptr;
         m_deferredCachePolicy = UseProtocolCachePolicy;
     }
 }
 
 void HistoryController::updateForInitialLoadInChildFrame(Frame* frame, HistoryItem* item)
 {
     ASSERT(frame->tree().parent());
     if (!m_currentEntry)
         return;
     if (HistoryNode* existingNode = m_currentEntry->historyNodeForFrame(frame))
@@ skipping 27 matching lines @@
     RefPtr<HistoryItem> item = historyNode->value()->copy();
     const Vector<OwnPtr<HistoryNode> >& childEntries = historyNode->children();
     for (size_t i = 0; i < childEntries.size(); i++)
         item->addChildItem(itemForExport(childEntries[i].get()));
     return item;
 }
 
 PassRefPtr<HistoryItem> HistoryController::currentItemForExport()
 {
     if (!m_currentEntry)
-        return 0;
+        return nullptr;
     return itemForExport(m_currentEntry->rootHistoryNode());
 }
 
 PassRefPtr<HistoryItem> HistoryController::previousItemForExport()
 {
     if (!m_previousEntry)
-        return 0;
+        return nullptr;
     return itemForExport(m_previousEntry->rootHistoryNode());
 }
 
 HistoryItem* HistoryController::itemForNewChildFrame(Frame* frame) const
 {
     return m_currentEntry ? m_currentEntry->itemForFrame(frame) : 0;
 }
 
 void HistoryController::removeChildrenForRedirect(Frame* frame)
 {
@@ skipping 11 matching lines @@
     } else {
         HistoryItem* oldItem = m_currentEntry->itemForFrame(targetFrame);
         if (!clipAtTarget && oldItem)
             newItem->setDocumentSequenceNumber(oldItem->documentSequenceNumber());
         m_previousEntry = m_currentEntry.release();
         m_currentEntry = m_previousEntry->cloneAndReplace(newItem.get(), clipAtTarget, targetFrame, m_page);
     }
 }
 
 } // namespace WebCore