Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/css/resolver/StyleResourceLoader.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google 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 70 matching lines @@
         return StyleGeneratedImage::create(imageGeneratorValue);
     }
 
     if (CSSCursorImageValue* cursorImageValue
         = pendingImage->cssCursorImageValue())
         return cursorImageValue->cachedImage(fetcher, deviceScaleFactor);
 
     if (CSSImageSetValue* imageSetValue = pendingImage->cssImageSetValue())
         return imageSetValue->cachedImageSet(fetcher, deviceScaleFactor, options);
 
-    return 0;
+    return nullptr;
 }
 
 PassRefPtr<StyleImage> StyleResourceLoader::loadPendingImage(StylePendingImage* pendingImage, float deviceScaleFactor)
 {
     return doLoadPendingImage(m_fetcher, pendingImage, deviceScaleFactor, ResourceFetcher::defaultResourceOptions());
 }
 
 void StyleResourceLoader::loadPendingShapeImage(RenderStyle* renderStyle, ShapeValue* shapeValue, float deviceScaleFactor)
 {
     if (!shapeValue)
@@ skipping 99 matching lines @@
 void StyleResourceLoader::loadPendingResources(RenderStyle* renderStyle, ElementStyleResources& elementStyleResources)
 {
     // Start loading images referenced by this style.
     loadPendingImages(renderStyle, elementStyleResources);
 
     // Start loading the SVG Documents referenced by this style.
     loadPendingSVGDocuments(renderStyle, elementStyleResources);
 }
 
 }