C++11: Replace 0 with nullptr where applicable in layout code.

Source/core/layout/OrderIterator.cpp

 /*
  * Copyright (C) 2011 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 19 matching lines @@
 
 #include "config.h"
 #include "core/layout/OrderIterator.h"
 
 #include "core/layout/LayoutBox.h"
 
 namespace blink {
 
 OrderIterator::OrderIterator(const LayoutBox* containerBox)
     : m_containerBox(containerBox)
-    , m_currentChild(0)
+    , m_currentChild(nullptr)
     , m_isReset(false)
 {
 }
 
 LayoutBox* OrderIterator::first()
 {
     reset();
     return next();
 }
 
 LayoutBox* OrderIterator::next()
 {
     do {
         if (!m_currentChild) {
             if (m_orderValuesIterator == m_orderValues.end())
-                return 0;
+                return nullptr;
 
             if (!m_isReset) {
                 ++m_orderValuesIterator;
                 if (m_orderValuesIterator == m_orderValues.end())
-                    return 0;
+                    return nullptr;
             } else {
                 m_isReset = false;
             }
 
             m_currentChild = m_containerBox->firstChildBox();
         } else {
             m_currentChild = m_currentChild->nextSiblingBox();
         }
     } while (!m_currentChild || m_currentChild->style()->order() != *m_orderValuesIterator);
 
     return m_currentChild;
 }
 
 void OrderIterator::reset()
 {
-    m_currentChild = 0;
+    m_currentChild = nullptr;
     m_orderValuesIterator = m_orderValues.begin();
     m_isReset = true;
 }
 
 OrderIteratorPopulator::~OrderIteratorPopulator()
 {
     m_iterator.reset();
 }
 
 void OrderIteratorPopulator::collectChild(const LayoutBox* child)
 {
     m_iterator.m_orderValues.insert(child->style()->order());
 }
 
 } // namespace blink