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

Source/core/layout/LayoutBlockFlow.h

Index: Source/core/layout/LayoutBlockFlow.h
diff --git a/Source/core/layout/LayoutBlockFlow.h b/Source/core/layout/LayoutBlockFlow.h
index 5c2db784c58c6adbe870c260f9dbe196c961b9a1..45be5dc274d02a1d80304be35f25bcba0329300c 100644
--- a/Source/core/layout/LayoutBlockFlow.h
+++ b/Source/core/layout/LayoutBlockFlow.h
@@ -105,15 +105,15 @@ public:
 
     RootInlineBox* createAndAppendRootInlineBox();
 
-    void markAllDescendantsWithFloatsForLayout(LayoutBox* floatToRemove = 0, bool inLayout = true);
-    void markSiblingsWithFloatsForLayout(LayoutBox* floatToRemove = 0);
+    void markAllDescendantsWithFloatsForLayout(LayoutBox* floatToRemove = nullptr, bool inLayout = true);
+    void markSiblingsWithFloatsForLayout(LayoutBox* floatToRemove = nullptr);
 
     bool containsFloats() const { return m_floatingObjects && !m_floatingObjects->set().isEmpty(); }
     bool containsFloat(LayoutBox*) const;
 
     void removeFloatingObjects();
 
-    virtual void addChild(LayoutObject* newChild, LayoutObject* beforeChild = 0) override;
+    virtual void addChild(LayoutObject* newChild, LayoutObject* beforeChild = nullptr) override;
 
     void moveAllChildrenIncludingFloatsTo(LayoutBlock* toBlock, bool fullRemoveInsert);
 
@@ -190,7 +190,7 @@ public:
     GapRects selectionGapRectsForPaintInvalidation(const LayoutBoxModelObject* paintInvalidationContainer) const;
     GapRects selectionGaps(const LayoutBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
         LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight,
-        const PaintInfo* = 0, ClipScope* = 0) const;
+        const PaintInfo* = nullptr, ClipScope* = nullptr) const;
     GapRects inlineSelectionGaps(const LayoutBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
         LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const PaintInfo*) const;
     GapRects blockSelectionGaps(const LayoutBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
@@ -284,7 +284,7 @@ private:
 
     // Called from lineWidth, to position the floats added in the last line.
     // Returns true if and only if it has positioned any floats.
-    bool positionNewFloats(LineWidth* = 0);
+    bool positionNewFloats(LineWidth* = nullptr);
 
     LayoutUnit getClearDelta(LayoutBox* child, LayoutUnit yPos);