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

Source/core/layout/svg/SVGTextMetrics.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010-2012. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 42 matching lines @@
     m_height = scaledFont.fontMetrics().floatHeight() / scalingFactor;
 
     ASSERT(run.length() >= 0);
     m_length = static_cast<unsigned>(run.length());
 }
 
 TextRun SVGTextMetrics::constructTextRun(LayoutSVGInlineText* text, unsigned position, unsigned length, TextDirection textDirection)
 {
     const ComputedStyle& style = text->styleRef();
 
-    TextRun run(static_cast<const LChar*>(0) // characters, will be set below if non-zero.
+    TextRun run(static_cast<const LChar*>(nullptr) // characters, will be set below if non-zero.
         , 0 // length, will be set below if non-zero.
         , 0 // xPos, only relevant with allowTabs=true
         , 0 // padding, only relevant for justified text, not relevant for SVG
         , TextRun::AllowTrailingExpansion
         , textDirection
         , isOverride(style.unicodeBidi()) /* directionalOverride */);
 
     if (length) {
         if (text->is8Bit())
             run.setText(text->characters8() + position, length);
@@ skipping 23 matching lines @@
     float scalingFactor = text->scalingFactor();
     ASSERT(scalingFactor);
 
     m_width = width / scalingFactor;
     m_height = text->scaledFont().fontMetrics().floatHeight() / scalingFactor;
 
     m_length = length;
 }
 
 }