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

Source/core/layout/line/LayoutTextInfo.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All right reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 14 matching lines @@
 
 #include "platform/text/TextBreakIterator.h"
 
 namespace blink {
 
 class Font;
 class LayoutText;
 
 struct LayoutTextInfo {
     LayoutTextInfo()
-        : m_text(0)
-        , m_font(0)
+        : m_text(nullptr)
+        , m_font(nullptr)
     {
     }
 
     LayoutText* m_text;
     LazyLineBreakIterator m_lineBreakIterator;
     const Font* m_font;
 };
 
 } // namespace blink
 
 #endif // LayoutTextInfo_h