Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/graphics/GraphicsLayer.cpp

 /*
  * Copyright (C) 2009 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 966 matching lines @@
 {
     if (rect == m_contentsRect)
         return;
 
     m_contentsRect = rect;
     updateContentsRect();
 }
 
 void GraphicsLayer::setContentsToImage(Image* image)
 {
-    RefPtr<NativeImageSkia> nativeImage = image ? image->nativeImageForCurrentFrame() : 0;
+    RefPtr<NativeImageSkia> nativeImage = image ? image->nativeImageForCurrentFrame() : nullptr;
     if (nativeImage) {
         if (!m_imageLayer) {
             m_imageLayer = adoptPtr(Platform::current()->compositorSupport()->createImageLayer());
             registerContentsLayer(m_imageLayer->layer());
         }
         m_imageLayer->setBitmap(nativeImage->bitmap());
         m_imageLayer->layer()->setOpaque(image->currentFrameKnownToBeOpaque());
         updateContentsRect();
     } else {
         if (m_imageLayer) {
             unregisterContentsLayer(m_imageLayer->layer());
             m_imageLayer.clear();
         }
     }
 
     setContentsTo(m_imageLayer ? m_imageLayer->layer() : 0);
 }
 
 void GraphicsLayer::setContentsToNinePatch(Image* image, const IntRect& aperture)
 {
     if (m_ninePatchLayer) {
         unregisterContentsLayer(m_ninePatchLayer->layer());
         m_ninePatchLayer.clear();
     }
-    RefPtr<NativeImageSkia> nativeImage = image ? image->nativeImageForCurrentFrame() : 0;
+    RefPtr<NativeImageSkia> nativeImage = image ? image->nativeImageForCurrentFrame() : nullptr;
     if (nativeImage) {
         m_ninePatchLayer = adoptPtr(Platform::current()->compositorSupport()->createNinePatchLayer());
         m_ninePatchLayer->setBitmap(nativeImage->bitmap(), aperture);
         m_ninePatchLayer->layer()->setOpaque(image->currentFrameKnownToBeOpaque());
         registerContentsLayer(m_ninePatchLayer->layer());
     }
     setContentsTo(m_ninePatchLayer ? m_ninePatchLayer->layer() : 0);
 }
 
 void GraphicsLayer::setContentsToSolidColor(const Color& color)
@@ skipping 201 matching lines @@
 #ifndef NDEBUG
 void showGraphicsLayerTree(const WebCore::GraphicsLayer* layer)
 {
     if (!layer)
         return;
 
     String output = layer->layerTreeAsText(WebCore::LayerTreeIncludesDebugInfo);
     fprintf(stderr, "%s\n", output.utf8().data());
 }
 #endif