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

Source/core/layout/LayoutRuby.h

 /*
  * Copyright (C) 2009 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 38 matching lines @@
 // Note: <rp> elements are defined as having 'display:none' and thus normally are not assigned a layoutObject.
 //
 // Generated :before/:after content is shunted into anonymous inline blocks
 
 // <ruby> when used as 'display:inline'
 class LayoutRubyAsInline final : public LayoutInline {
 public:
     LayoutRubyAsInline(Element*);
     virtual ~LayoutRubyAsInline();
 
-    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = 0) override;
+    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = nullptr) override;
     virtual void removeChild(LayoutObject* child) override;
 
     virtual const char* name() const override { return "LayoutRuby (inline)"; }
 
 protected:
     virtual void styleDidChange(StyleDifference, const ComputedStyle* oldStyle) override;
 
 private:
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectRuby || LayoutInline::isOfType(type); }
     virtual bool createsAnonymousWrapper() const override { return true; }
 };
 
 // <ruby> when used as 'display:block' or 'display:inline-block'
 class LayoutRubyAsBlock final : public LayoutBlockFlow {
 public:
     LayoutRubyAsBlock(Element*);
     virtual ~LayoutRubyAsBlock();
 
-    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = 0) override;
+    virtual void addChild(LayoutObject* child, LayoutObject* beforeChild = nullptr) override;
     virtual void removeChild(LayoutObject* child) override;
 
     virtual const char* name() const override { return "LayoutRuby (block)"; }
 
 protected:
     virtual void styleDidChange(StyleDifference, const ComputedStyle* oldStyle) override;
 
 private:
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectRuby || LayoutBlockFlow::isOfType(type); }
     virtual bool createsAnonymousWrapper() const override { return true; }
     virtual void removeLeftoverAnonymousBlock(LayoutBlock*) override { ASSERT_NOT_REACHED(); }
 };
 
 } // namespace blink
 
 #endif // LayoutRuby_h