Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/css/StyleRuleImport.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 20 matching lines @@
 
 namespace WebCore {
 
 PassRefPtrWillBeRawPtr<StyleRuleImport> StyleRuleImport::create(const String& href, PassRefPtr<MediaQuerySet> media)
 {
     return adoptRefCountedWillBeRefCountedGarbageCollected(new StyleRuleImport(href, media));
 }
 
 StyleRuleImport::StyleRuleImport(const String& href, PassRefPtr<MediaQuerySet> media)
     : StyleRuleBase(Import)
-    , m_parentStyleSheet(0)
+    , m_parentStyleSheet(nullptr)
     , m_styleSheetClient(this)
     , m_strHref(href)
     , m_mediaQueries(media)
     , m_resource(0)
     , m_loading(false)
 {
     if (!m_mediaQueries)
         m_mediaQueries = MediaQuerySet::create(String());
 }
 
@@ skipping 76 matching lines @@
         // removed from the pending sheet count, so let the doc know
         // the sheet being imported is pending.
         if (m_parentStyleSheet && m_parentStyleSheet->loadCompleted() && rootSheet == m_parentStyleSheet)
             m_parentStyleSheet->startLoadingDynamicSheet();
         m_loading = true;
         m_resource->addClient(&m_styleSheetClient);
     }
 }
 
 } // namespace WebCore