Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp

 /*
  * Copyright (C) 2012 Google 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
@@ skipping 49 matching lines @@
 {
 }
 
 SkiaImageFilterBuilder::~SkiaImageFilterBuilder()
 {
 }
 
 PassRefPtr<SkImageFilter> SkiaImageFilterBuilder::build(FilterEffect* effect, ColorSpace colorSpace)
 {
     if (!effect)
-        return 0;
+        return nullptr;
 
     FilterColorSpacePair key(effect, colorSpace);
     FilterBuilderHashMap::iterator it = m_map.find(key);
     if (it != m_map.end()) {
         return it->value;
     } else {
         // Note that we may still need the color transform even if the filter is null
         RefPtr<SkImageFilter> origFilter = effect->createImageFilter(this);
         RefPtr<SkImageFilter> filter = transformColorSpace(origFilter.get(), effect->operatingColorSpace(), colorSpace);
         m_map.set(key, filter);
@@ skipping 123 matching lines @@
     }
     return true;
 }
 
 PassRefPtr<SkImageFilter> SkiaImageFilterBuilder::buildResize(float scaleX, float scaleY, SkImageFilter* input)
 {
     return adoptRef(new SkResizeImageFilter(scaleX, scaleY, SkPaint::kHigh_FilterLevel, input));
 }
 
 };