Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/graphics/LazyDecodingPixelRef.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 32 matching lines @@
 }
 
 LazyDecodingPixelRef::~LazyDecodingPixelRef()
 {
 }
 
 SkData* LazyDecodingPixelRef::onRefEncodedData()
 {
     // If the image has been clipped or scaled, do not return the original encoded data, since
     // on playback it will not be known how the clipping/scaling was done.
-    RefPtr<SharedBuffer> buffer = 0;
+    RefPtr<SharedBuffer> buffer = nullptr;
     bool allDataReceived = false;
     m_frameGenerator->copyData(&buffer, &allDataReceived);
     if (buffer && allDataReceived) {
         SkData* skdata = SkData::NewWithCopy((void*)buffer->data(), buffer->size());
         return skdata;
     }
     return 0;
 }
 
 bool LazyDecodingPixelRef::onNewLockPixels(LockRec* rec)
@@ skipping 51 matching lines @@
 }
 
 void LazyDecodingPixelRef::Decode()
 {
     lockPixels();
     unlockPixels();
 }
 
 
 } // namespace blink