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

Source/core/layout/TextAutosizer.h

Index: Source/core/layout/TextAutosizer.h
diff --git a/Source/core/layout/TextAutosizer.h b/Source/core/layout/TextAutosizer.h
index 43c4d3b37d21c244e4b2a0a66040015da2c22432..be2c33a1330ae19c2c78050bd708ccae105e7e3a 100644
--- a/Source/core/layout/TextAutosizer.h
+++ b/Source/core/layout/TextAutosizer.h
@@ -148,10 +148,10 @@ private:
     };
 
     struct Cluster {
-        explicit Cluster(const LayoutBlock* root, BlockFlags flags, Cluster* parent, Supercluster* supercluster = 0)
+        explicit Cluster(const LayoutBlock* root, BlockFlags flags, Cluster* parent, Supercluster* supercluster = nullptr)
             : m_root(root)
             , m_flags(flags)
-            , m_deepestBlockContainingAllText(0)
+            , m_deepestBlockContainingAllText(nullptr)
             , m_parent(parent)
             , m_multiplier(0)
             , m_hasEnoughTextToAutosize(UnknownAmountOfText)
@@ -260,9 +260,9 @@ private:
     void resetMultipliers();
     BeginLayoutBehavior prepareForLayout(const LayoutBlock*);
     void prepareClusterStack(const LayoutObject*);
-    bool clusterHasEnoughTextToAutosize(Cluster*, const LayoutBlock* widthProvider = 0);
-    bool superclusterHasEnoughTextToAutosize(Supercluster*, const LayoutBlock* widthProvider = 0);
-    bool clusterWouldHaveEnoughTextToAutosize(const LayoutBlock* root, const LayoutBlock* widthProvider = 0);
+    bool clusterHasEnoughTextToAutosize(Cluster*, const LayoutBlock* widthProvider = nullptr);
+    bool superclusterHasEnoughTextToAutosize(Supercluster*, const LayoutBlock* widthProvider = nullptr);
+    bool clusterWouldHaveEnoughTextToAutosize(const LayoutBlock* root, const LayoutBlock* widthProvider = nullptr);
     Fingerprint getFingerprint(const LayoutObject*);
     Fingerprint computeFingerprint(const LayoutObject*);
     Cluster* maybeCreateCluster(const LayoutBlock*);