Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 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 1339 matching lines @@
     Document* document = m_frame->document();
 
     if (document->focusedElement() && document->focusedElement()->hasTagName(selectTag)) {
         HTMLSelectElement* selectElement = toHTMLSelectElement(document->focusedElement());
         if (selectElement->canSelectAll()) {
             selectElement->selectAll();
             return;
         }
     }
 
-    RefPtr<Node> root = 0;
+    RefPtr<Node> root = nullptr;
     Node* selectStartTarget = 0;
     if (isContentEditable()) {
         root = highestEditableRoot(m_selection.start());
         if (Node* shadowRoot = m_selection.nonBoundaryShadowTreeRootNode())
             selectStartTarget = shadowRoot->shadowHost();
         else
             selectStartTarget = root.get();
     } else {
         root = m_selection.nonBoundaryShadowTreeRootNode();
         if (root)
@@ skipping 276 matching lines @@
         while (target) {
             // We don't want to set focus on a subframe when selecting in a parent frame,
             // so add the !isFrameElement check here. There's probably a better way to make this
             // work in the long term, but this is the safest fix at this time.
             if (target->isMouseFocusable() && !isFrameElement(target)) {
                 m_frame->page()->focusController().setFocusedElement(target, m_frame);
                 return;
             }
             target = target->parentOrShadowHostElement();
         }
-        m_frame->document()->setFocusedElement(0);
+        m_frame->document()->setFocusedElement(nullptr);
     }
 
     if (caretBrowsing)
         m_frame->page()->focusController().setFocusedElement(0, m_frame);
 }
 
 static String extractSelectedText(const FrameSelection& selection, TextIteratorBehavior behavior)
 {
     // We remove '\0' characters because they are not visibly rendered to the user.
     return plainText(selection.toNormalizedRange().get(), behavior).replace(0, "");
@@ skipping 156 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const WebCore::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif