Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/editing/htmlediting.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 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 774 matching lines @@
 PassRefPtr<HTMLElement> createDefaultParagraphElement(Document& document)
 {
     switch (document.frame()->editor().defaultParagraphSeparator()) {
     case EditorParagraphSeparatorIsDiv:
         return HTMLDivElement::create(document);
     case EditorParagraphSeparatorIsP:
         return HTMLParagraphElement::create(document);
     }
 
     ASSERT_NOT_REACHED();
-    return 0;
+    return nullptr;
 }
 
 PassRefPtr<HTMLElement> createBreakElement(Document& document)
 {
     return HTMLBRElement::create(document);
 }
 
 PassRefPtr<HTMLElement> createOrderedListElement(Document& document)
 {
     return HTMLOListElement::create(document);
@@ skipping 312 matching lines @@
     // if the selection starts just before a paragraph break, skip over it
     if (isEndOfParagraph(visiblePosition))
         return visiblePosition.next().deepEquivalent().downstream();
 
     // otherwise, make sure to be at the start of the first selected node,
     // instead of possibly at the end of the last node before the selection
     return visiblePosition.deepEquivalent().downstream();
 }
 
 } // namespace WebCore