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

Source/core/layout/svg/LayoutSVGContainer.h

 /*
  * Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2009 Google, Inc.  All rights reserved.
  * Copyright (C) 2009 Apple 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 44 matching lines @@
 
     virtual FloatRect objectBoundingBox() const override final { return m_objectBoundingBox; }
 
 protected:
     virtual LayoutObjectChildList* virtualChildren() override final { return children(); }
     virtual const LayoutObjectChildList* virtualChildren() const override final { return children(); }
 
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectSVGContainer || LayoutSVGModelObject::isOfType(type); }
     virtual void layout() override;
 
-    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = 0) override final;
+    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = nullptr) override final;
     virtual void removeChild(LayoutObject*) override final;
     virtual void addFocusRingRects(Vector<LayoutRect>&, const LayoutPoint& additionalOffset) const override final;
 
     virtual FloatRect strokeBoundingBox() const override final { return m_strokeBoundingBox; }
 
     virtual bool nodeAtFloatPoint(HitTestResult&, const FloatPoint& pointInParent, HitTestAction) override;
 
     // Allow LayoutSVGTransformableContainer to hook in at the right time in layout().
     virtual bool calculateLocalTransform() { return false; }
 
@@ skipping 18 matching lines @@
     bool m_needsBoundariesUpdate;
     mutable bool m_hasNonIsolatedBlendingDescendants : 1;
     mutable bool m_hasNonIsolatedBlendingDescendantsDirty : 1;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutSVGContainer, isSVGContainer());
 
 } // namespace blink
 
 #endif // LayoutSVGContainer_h