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

Source/core/layout/LayoutDeprecatedFlexibleBox.cpp

 /*
  * This file is part of the layout object implementation for KHTML.
  *
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 63 matching lines @@
     LayoutBox* next()
     {
         do {
             if (!m_currentChild) {
                 ++m_ordinalIteration;
 
                 if (!m_ordinalIteration) {
                     m_currentOrdinal = m_forward ? 1 : m_largestOrdinal;
                 } else {
                     if (static_cast<size_t>(m_ordinalIteration) >= m_ordinalValues.size() + 1)
-                        return 0;
+                        return nullptr;
 
                     // Only copy+sort the values once per layout even if the iterator is reset.
                     if (m_ordinalValues.size() != m_sortedOrdinalValues.size()) {
                         copyToVector(m_ordinalValues, m_sortedOrdinalValues);
                         std::sort(m_sortedOrdinalValues.begin(), m_sortedOrdinalValues.end());
                     }
                     m_currentOrdinal = m_forward ? m_sortedOrdinalValues[m_ordinalIteration - 1] : m_sortedOrdinalValues[m_sortedOrdinalValues.size() - m_ordinalIteration];
                 }
 
                 m_currentChild = m_forward ? m_box->firstChildBox() : m_box->lastChildBox();
@@ skipping 907 matching lines @@
     if (minHeight.isFixed() || minHeight.isAuto()) {
         LayoutUnit minHeight = child->style()->minHeight().value();
         LayoutUnit height = contentHeightForChild(child);
         LayoutUnit allowedShrinkage = std::min<LayoutUnit>(0, minHeight - height);
         return allowedShrinkage;
     }
     return 0;
 }
 
 } // namespace blink