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

Source/core/layout/line/InlineBox.h

Index: Source/core/layout/line/InlineBox.h
diff --git a/Source/core/layout/line/InlineBox.h b/Source/core/layout/line/InlineBox.h
index 9e04d3c27de287bfb94b5822bf63ce3e8a043ba4..545c51c7b5c4604ce498fbdf06546b286a14e536 100644
--- a/Source/core/layout/line/InlineBox.h
+++ b/Source/core/layout/line/InlineBox.h
@@ -40,9 +40,9 @@ class InlineBox {
     WTF_MAKE_NONCOPYABLE(InlineBox);
 public:
     InlineBox(LayoutObject& obj)
-        : m_next(0)
-        , m_prev(0)
-        , m_parent(0)
+        : m_next(nullptr)
+        , m_prev(nullptr)
+        , m_parent(nullptr)
         , m_layoutObject(obj)
         , m_logicalWidth()
 #if ENABLE(ASSERT)
@@ -111,7 +111,7 @@ public:
     void showLineTreeForThis() const;
 
     virtual void showBox(int = 0) const;
-    virtual void showLineTreeAndMark(const InlineBox* = 0, const char* = 0, const InlineBox* = 0, const char* = 0, const LayoutObject* = 0, int = 0) const;
+    virtual void showLineTreeAndMark(const InlineBox* = nullptr, const char* = nullptr, const InlineBox* = nullptr, const char* = nullptr, const LayoutObject* = nullptr, int = 0) const;
 #endif
 
     virtual const char* boxName() const;