Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/modules/webaudio/ChannelMergerNode.cpp

 /*
  * Copyright (C) 2010 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 25 matching lines @@
 #include "modules/webaudio/AudioNodeInput.h"
 #include "modules/webaudio/AudioNodeOutput.h"
 
 const unsigned DefaultNumberOfOutputChannels = 1;
 
 namespace WebCore {
 
 PassRefPtr<ChannelMergerNode> ChannelMergerNode::create(AudioContext* context, float sampleRate, unsigned numberOfInputs)
 {
     if (!numberOfInputs || numberOfInputs > AudioContext::maxNumberOfChannels())
-        return 0;
+        return nullptr;
 
     return adoptRef(new ChannelMergerNode(context, sampleRate, numberOfInputs));
 }
 
 ChannelMergerNode::ChannelMergerNode(AudioContext* context, float sampleRate, unsigned numberOfInputs)
     : AudioNode(context, sampleRate)
     , m_desiredNumberOfOutputChannels(DefaultNumberOfOutputChannels)
 {
     ScriptWrappable::init(this);
     // Create the requested number of inputs.
@@ skipping 60 matching lines @@
     // channels because of tryLocks() in the context's updating system. So record the new number of
     // output channels here.
     m_desiredNumberOfOutputChannels = numberOfOutputChannels;
 
     AudioNode::checkNumberOfChannelsForInput(input);
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)