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

Source/core/layout/svg/LayoutSVGText.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * 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.
  *
@@ skipping 53 matching lines @@
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectSVGText || LayoutSVGBlock::isOfType(type); }
 
     virtual void paint(const PaintInfo&, const LayoutPoint&) override;
     virtual bool nodeAtFloatPoint(HitTestResult&, const FloatPoint& pointInParent, HitTestAction) override;
     virtual PositionWithAffinity positionForPoint(const LayoutPoint&) override;
 
     virtual void layout() override;
 
     virtual void absoluteQuads(Vector<FloatQuad>&, bool* wasFixed) const override;
 
-    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = 0) override;
+    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = nullptr) override;
     virtual void removeChild(LayoutObject*) override;
     virtual void willBeDestroyed() override;
 
     virtual FloatRect objectBoundingBox() const override { return frameRect(); }
     virtual FloatRect strokeBoundingBox() const override;
 
     virtual RootInlineBox* createRootInlineBox() override;
 
     bool shouldHandleSubtreeMutations() const;
 
     bool m_needsReordering : 1;
     bool m_needsPositioningValuesUpdate : 1;
     bool m_needsTransformUpdate : 1;
     bool m_needsTextMetricsUpdate : 1;
     SVGTextLayoutAttributesBuilder m_layoutAttributesBuilder;
     Vector<SVGTextLayoutAttributes*> m_layoutAttributes;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutSVGText, isSVGText());
 
 }
 
 #endif