Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/html/ImageDocument.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 144 matching lines @@
         document()->imageUpdated();
     }
 
     document()->finishedParsing();
 }
 
 // --------
 
 ImageDocument::ImageDocument(const DocumentInit& initializer)
     : HTMLDocument(initializer, ImageDocumentClass)
-    , m_imageElement(0)
+    , m_imageElement(nullptr)
     , m_imageSizeIsKnown(false)
     , m_didShrinkImage(false)
     , m_shouldShrinkImage(shouldShrinkToFit())
 {
     setCompatibilityMode(QuirksMode);
     lockCompatibilityMode();
 }
 
 PassRefPtr<DocumentParser> ImageDocument::createParser()
 {
@@ skipping 182 matching lines @@
     return m_imageElement->cachedImage();
 }
 
 bool ImageDocument::shouldShrinkToFit() const
 {
     return frame()->settings()->shrinksStandaloneImagesToFit() && frame()->isMainFrame();
 }
 
 void ImageDocument::dispose()
 {
-    m_imageElement = 0;
+    m_imageElement = nullptr;
     HTMLDocument::dispose();
 }
 
 // --------
 
 void ImageEventListener::handleEvent(ExecutionContext*, Event* event)
 {
     if (event->type() == EventTypeNames::resize)
         m_doc->windowSizeChanged();
     else if (event->type() == EventTypeNames::click && event->isMouseEvent()) {
         MouseEvent* mouseEvent = toMouseEvent(event);
         m_doc->imageClicked(mouseEvent->x(), mouseEvent->y());
     }
 }
 
 bool ImageEventListener::operator==(const EventListener& listener)
 {
     if (const ImageEventListener* imageEventListener = ImageEventListener::cast(&listener))
         return m_doc == imageEventListener->m_doc;
     return false;
 }
 
 }