Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/web/WebDOMEvent.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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
 #include "core/events/Event.h"
 #include "wtf/PassRefPtr.h"
 
 namespace blink {
 
 class WebDOMEventPrivate : public WebCore::Event {
 };
 
 void WebDOMEvent::reset()
 {
-    assign(0);
+    assign(nullptr);
 }
 
 void WebDOMEvent::assign(const WebDOMEvent& other)
 {
     m_private = other.m_private;
 }
 
 void WebDOMEvent::assign(const WTF::PassRefPtr<WebDOMEventPrivate>& event)
 {
     m_private = event;
@@ skipping 141 matching lines @@
     return m_private->hasInterface(WebCore::EventNames::XMLHttpRequestProgressEvent);
 }
 
 bool WebDOMEvent::isBeforeLoadEvent() const
 {
     ASSERT(m_private.get());
     return m_private->hasInterface(WebCore::EventNames::BeforeLoadEvent);
 }
 
 } // namespace blink