Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/DragImage.cpp

 /*
  * Copyright (C) 2007 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 97 matching lines @@
     return adoptPtr(new DragImage(skBitmap, deviceScaleFactor));
 }
 
 static Font deriveDragLabelFont(int size, FontWeight fontWeight, const FontDescription& systemFont)
 {
     FontDescription description = systemFont;
     description.setWeight(fontWeight);
     description.setSpecifiedSize(size);
     description.setComputedSize(size);
     Font result(description);
-    result.update(0);
+    result.update(nullptr);
     return result;
 }
 
 PassOwnPtr<DragImage> DragImage::create(const KURL& url, const String& inLabel, const FontDescription& systemFont, float deviceScaleFactor)
 {
     const Font labelFont = deriveDragLabelFont(kDragLinkLabelFontSize, FontWeightBold, systemFont);
     const Font urlFont = deriveDragLabelFont(kDragLinkUrlFontSize, FontWeightNormal, systemFont);
     FontCachePurgePreventer fontCachePurgePreventer;
 
     bool drawURLString = true;
@@ skipping 136 matching lines @@
             *pixel = SkPreMultiplyARGB(
                 SkColorGetA(*pixel) * fraction,
                 SkColorGetR(*pixel),
                 SkColorGetG(*pixel),
                 SkColorGetB(*pixel));
         }
     }
 }
 
 } // namespace WebCore