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

Source/core/layout/LayoutFlowThread.h

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 79 matching lines @@
     virtual void mapRectToPaintInvalidationBacking(const LayoutBoxModelObject* paintInvalidationContainer, LayoutRect&, const PaintInvalidationState*) const override;
 
     LayoutUnit pageLogicalHeightForOffset(LayoutUnit);
     LayoutUnit pageRemainingLogicalHeightForOffset(LayoutUnit, PageBoundaryRule = IncludePageBoundary);
 
     virtual void setPageBreak(LayoutUnit /*offset*/, LayoutUnit /*spaceShortage*/) { }
     virtual void updateMinimumPageHeight(LayoutUnit /*offset*/, LayoutUnit /*minHeight*/) { }
 
     bool columnSetsHaveUniformLogicalHeight() const { return m_columnSetsHaveUniformLogicalHeight; }
 
-    virtual bool addForcedColumnBreak(LayoutUnit, LayoutObject* breakChild, bool isBefore, LayoutUnit* offsetBreakAdjustment = 0) { return false; }
+    virtual bool addForcedColumnBreak(LayoutUnit, LayoutObject* breakChild, bool isBefore, LayoutUnit* offsetBreakAdjustment = nullptr) { return false; }
 
     virtual bool isPageLogicalHeightKnown() const { return true; }
     bool pageLogicalSizeChanged() const { return m_pageLogicalSizeChanged; }
 
     void collectLayerFragments(DeprecatedPaintLayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect);
 
     // Return the visual bounding box based on the supplied flow-thread bounding box. Both
     // rectangles are completely physical in terms of writing mode.
     LayoutRect fragmentsBoundingBox(const LayoutRect& layerBoundingBox) const;
 
@@ skipping 16 matching lines @@
 
     LayoutMultiColumnSetList m_multiColumnSetList;
 
     typedef PODInterval<LayoutUnit, LayoutMultiColumnSet*> MultiColumnSetInterval;
     typedef PODIntervalTree<LayoutUnit, LayoutMultiColumnSet*> MultiColumnSetIntervalTree;
 
     class MultiColumnSetSearchAdapter {
     public:
         MultiColumnSetSearchAdapter(LayoutUnit offset)
             : m_offset(offset)
-            , m_result(0)
+            , m_result(nullptr)
         {
         }
 
         const LayoutUnit& lowValue() const { return m_offset; }
         const LayoutUnit& highValue() const { return m_offset; }
         void collectIfNeeded(const MultiColumnSetInterval&);
 
         LayoutMultiColumnSet* result() const { return m_result; }
 
     private:
@@ skipping 17 matching lines @@
 };
 
 template <> struct ValueToString<LayoutMultiColumnSet*> {
     static String string(const LayoutMultiColumnSet* value) { return String::format("%p", value); }
 };
 #endif
 
 } // namespace blink
 
 #endif // LayoutFlowThread_h