Templatize PositionWithAffinity class

Source/core/editing/PositionWithAffinity.h

Index: Source/core/editing/PositionWithAffinity.h
diff --git a/Source/core/editing/PositionWithAffinity.h b/Source/core/editing/PositionWithAffinity.h
index e5e59589828d10379f7f4f3f63f7a29d4ff65b46..38fb1f641e77ca045b928c7e8bcf77057af2dbc2 100644
--- a/Source/core/editing/PositionWithAffinity.h
+++ b/Source/core/editing/PositionWithAffinity.h
@@ -11,23 +11,33 @@
 
 namespace blink {
 
-class CORE_EXPORT PositionWithAffinity {
+template <typename Position>
+class CORE_TEMPLATE_CLASS_EXPORT PositionWithAffinityTemplate {
     DISALLOW_ALLOCATION();
 public:
-    PositionWithAffinity(const Position&, EAffinity = DOWNSTREAM);
-    PositionWithAffinity();
-    ~PositionWithAffinity();
+    typedef Position PositionType;
+
+    PositionWithAffinityTemplate(const PositionType&, EAffinity = DOWNSTREAM);
+    PositionWithAffinityTemplate();
+    ~PositionWithAffinityTemplate();
 
     EAffinity affinity() const { return m_affinity; }
-    const Position& position() const { return m_position; }
+    const PositionType& position() const { return m_position; }
 
-    DECLARE_TRACE();
+    DEFINE_INLINE_TRACE()
+    {
+        visitor->trace(m_position);
+    }
 
 private:
-    Position m_position;
+    PositionType m_position;
     EAffinity m_affinity;
 };
 
+extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionWithAffinityTemplate<Position>;
+
+using PositionWithAffinity = PositionWithAffinityTemplate<Position>;
+
 } // namespace blink
 
 #endif // PositionWithAffinity_h