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

Source/core/layout/line/InlineTextBox.h

Index: Source/core/layout/line/InlineTextBox.h
diff --git a/Source/core/layout/line/InlineTextBox.h b/Source/core/layout/line/InlineTextBox.h
index 7eb96619ae1d7bc4ae677cb0edd5b79113689eec..286220afbc123dbf98293fb226b481de2a17d286 100644
--- a/Source/core/layout/line/InlineTextBox.h
+++ b/Source/core/layout/line/InlineTextBox.h
@@ -40,8 +40,8 @@ class InlineTextBox : public InlineBox {
 public:
     InlineTextBox(LayoutObject& obj, int start, unsigned short length)
         : InlineBox(obj)
-        , m_prevTextBox(0)
-        , m_nextTextBox(0)
+        , m_prevTextBox(nullptr)
+        , m_nextTextBox(nullptr)
         , m_start(start)
         , m_len(length)
         , m_truncation(cNoTruncation)
@@ -87,8 +87,8 @@ public:
     LayoutUnit logicalBottomVisualOverflow() const { return logicalOverflowRect().maxY(); }
 
     // charactersWithHyphen, if provided, must not be destroyed before the TextRun.
-    TextRun constructTextRun(const ComputedStyle&, const Font&, StringBuilder* charactersWithHyphen = 0) const;
-    TextRun constructTextRun(const ComputedStyle&, const Font&, StringView, int maximumLength, StringBuilder* charactersWithHyphen = 0) const;
+    TextRun constructTextRun(const ComputedStyle&, const Font&, StringBuilder* charactersWithHyphen = nullptr) const;
+    TextRun constructTextRun(const ComputedStyle&, const Font&, StringView, int maximumLength, StringBuilder* charactersWithHyphen = nullptr) const;
 
 #ifndef NDEBUG
     virtual void showBox(int = 0) const override;