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

Source/core/layout/TextRunConstructor.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 77 matching lines @@
         return constructTextRunInternal(context, font, static_cast<const LChar*>(nullptr), 0, style, direction);
     if (text->is8Bit())
         return constructTextRunInternal(context, font, text->characters8() + offset, length, style, direction);
     return constructTextRunInternal(context, font, text->characters16() + offset, length, style, direction);
 }
 
 TextRun constructTextRun(LayoutObject* context, const Font& font, const String& string, const ComputedStyle& style, TextDirection direction, TextRunFlags flags)
 {
     unsigned length = string.length();
     if (!length)
-        return constructTextRunInternal(context, font, static_cast<const LChar*>(0), length, style, direction, flags);
+        return constructTextRunInternal(context, font, static_cast<const LChar*>(nullptr), length, style, direction, flags);
     if (string.is8Bit())
         return constructTextRunInternal(context, font, string.characters8(), length, style, direction, flags);
     return constructTextRunInternal(context, font, string.characters16(), length, style, direction, flags);
 }
 
 TextRun constructTextRun(LayoutObject* context, const Font& font, const String& string, const ComputedStyle& style, TextRunFlags flags)
 {
     return constructTextRun(context, font, string, style, string.isEmpty() || string.is8Bit() ? LTR : determineDirectionality(string), flags);
 }
 
 TextRun constructTextRun(LayoutObject* context, const Font& font, const LayoutText* text, unsigned offset, unsigned length, const ComputedStyle& style)
 {
     ASSERT(offset + length <= text->textLength());
     if (text->hasEmptyText())
         return constructTextRunInternal(context, font, static_cast<const LChar*>(nullptr), 0, style, LTR);
     if (text->is8Bit())
         return constructTextRunInternal(context, font, text->characters8() + offset, length, style, LTR);
 
     TextRun run = constructTextRunInternal(context, font, text->characters16() + offset, length, style, LTR);
     run.setDirection(directionForRun(run));
     return run;
 }
 
 } // namespace blink