Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/SharedBuffer.cpp

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. 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 413 matching lines @@
     const char* segment = 0;
     unsigned position = 0;
     while (unsigned segmentSize = getSomeData(segment, position)) {
         memcpy(static_cast<char*>(arrayBuffer->data()) + position, segment, segmentSize);
         position += segmentSize;
     }
 
     if (position != arrayBuffer->byteLength()) {
         ASSERT_NOT_REACHED();
         // Don't return the incomplete ArrayBuffer.
-        return 0;
+        return nullptr;
     }
 
     return arrayBuffer;
 }
 
 PassRefPtr<SkData> SharedBuffer::getAsSkData() const
 {
     unsigned bufferLength = size();
     char* buffer = static_cast<char*>(sk_malloc_throw(bufferLength));
     const char* segment = 0;
     unsigned position = 0;
     while (unsigned segmentSize = getSomeData(segment, position)) {
         memcpy(buffer + position, segment, segmentSize);
         position += segmentSize;
     }
 
     if (position != bufferLength) {
         ASSERT_NOT_REACHED();
         // Don't return the incomplete SkData.
-        return 0;
+        return nullptr;
     }
     return adoptRef(SkData::NewFromMalloc(buffer, bufferLength));
 }
 
 } // namespace WebCore