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

Source/core/layout/LayoutBR.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *
  * 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 18 matching lines @@
  */
 namespace blink {
 
 class LayoutBR final : public LayoutText {
 public:
     explicit LayoutBR(Node*);
     virtual ~LayoutBR();
 
     virtual const char* name() const override { return "LayoutBR"; }
 
-    virtual LayoutRect selectionRectForPaintInvalidation(const LayoutBoxModelObject* /*paintInvalidationContainer*/) const override { return LayoutRect(); }
+    virtual LayoutRect selectionRectForPaintInvalidation(const LayoutBoxModelObject* /* paintInvalidationContainer */) const override { return LayoutRect(); }
 
-    virtual float width(unsigned /*from*/, unsigned /*len*/, const Font&, LayoutUnit /*xPos*/, TextDirection, HashSet<const SimpleFontData*>* = 0 /*fallbackFonts*/ , GlyphOverflow* = 0) const override { return 0; }
-    virtual float width(unsigned /*from*/, unsigned /*len*/, LayoutUnit /*xpos*/, TextDirection, bool = false /*firstLine*/, HashSet<const SimpleFontData*>* = 0 /*fallbackFonts*/, GlyphOverflow* = 0) const override { return 0; }
+    virtual float width(unsigned /* from */, unsigned /* len */, const Font&, LayoutUnit /* xpos */, TextDirection, HashSet<const SimpleFontData*>* = nullptr /* fallbackFonts */ , GlyphOverflow* = nullptr) const override { return 0; }
+    virtual float width(unsigned /* from */, unsigned /* len */, LayoutUnit /* xpos */, TextDirection, bool = false /* firstLine */, HashSet<const SimpleFontData*>* = nullptr /* fallbackFonts */, GlyphOverflow* = nullptr) const override { return 0; }
 
     int lineHeight(bool firstLine) const;
 
     // overrides
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectBr || LayoutText::isOfType(type); }
 
     virtual int caretMinOffset() const override;
     virtual int caretMaxOffset() const override;
 
     virtual PositionWithAffinity positionForPoint(const LayoutPoint&) override final;
 
 protected:
     virtual void styleDidChange(StyleDifference, const ComputedStyle* oldStyle) override;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBR, isBR());
 
 } // namespace blink
 
 #endif // LayoutBR_h