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

Source/core/layout/line/AbstractInlineTextBox.cpp

 /*
  * Copyright (C) 2013 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 18 matching lines @@
  */
 
 #include "config.h"
 #include "core/layout/line/AbstractInlineTextBox.h"
 
 #include "core/editing/iterators/TextIterator.h"
 #include "platform/text/TextBreakIterator.h"
 
 namespace blink {
 
-AbstractInlineTextBox::InlineToAbstractInlineTextBoxHashMap* AbstractInlineTextBox::gAbstractInlineTextBoxMap = 0;
+AbstractInlineTextBox::InlineToAbstractInlineTextBoxHashMap* AbstractInlineTextBox::gAbstractInlineTextBoxMap = nullptr;
 
 PassRefPtr<AbstractInlineTextBox> AbstractInlineTextBox::getOrCreate(LayoutText* layoutText, InlineTextBox* inlineTextBox)
 {
     if (!inlineTextBox)
         return nullptr;
 
     if (!gAbstractInlineTextBoxMap)
         gAbstractInlineTextBoxMap = new InlineToAbstractInlineTextBoxHashMap();
 
     InlineToAbstractInlineTextBoxHashMap::const_iterator it = gAbstractInlineTextBoxMap->find(inlineTextBox);
@@ skipping 141 matching lines @@
         return nullptr;
 
     InlineBox* previous = m_inlineTextBox->prevOnLine();
     if (previous && previous->isInlineTextBox())
         return getOrCreate(&toInlineTextBox(previous)->layoutObject(), toInlineTextBox(previous));
 
     return nullptr;
 }
 
 } // namespace blink