Introduce enum class TextAffinity as replacement of enum EAffinity

Source/core/editing/PositionWithAffinity.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file./*
 
 #ifndef PositionWithAffinity_h
 #define PositionWithAffinity_h
 
 #include "core/CoreExport.h"
 #include "core/editing/Position.h"
 #include "core/editing/TextAffinity.h"
 
 namespace blink {
 
 template <typename Strategy>
 class CORE_TEMPLATE_CLASS_EXPORT PositionWithAffinityTemplate {
     DISALLOW_ALLOCATION();
 public:
-    PositionWithAffinityTemplate(const PositionAlgorithm<Strategy>&, EAffinity = DOWNSTREAM);
+    // TODO(yosin) We should have single parameter constructor not to use
+    // default parameter for avoiding include "TextAffinity.h"
+    PositionWithAffinityTemplate(const PositionAlgorithm<Strategy>&, TextAffinity = TextAffinity::Downstream);
     PositionWithAffinityTemplate();
     ~PositionWithAffinityTemplate();
 
-    EAffinity affinity() const { return m_affinity; }
+    TextAffinity affinity() const { return m_affinity; }
     const PositionAlgorithm<Strategy>& position() const { return m_position; }
 
     // Returns true if both |this| and |other| is null or both |m_position|
     // and |m_affinity| equal.
     bool operator==(const PositionWithAffinityTemplate& other) const;
     bool operator!=(const PositionWithAffinityTemplate& other) const { return !operator==(other); }
 
     bool isNotNull() const { return m_position.isNotNull(); }
     bool isNull() const { return m_position.isNull(); }
 
     DEFINE_INLINE_TRACE()
     {
         visitor->trace(m_position);
     }
 
 private:
     PositionAlgorithm<Strategy> m_position;
-    EAffinity m_affinity;
+    TextAffinity m_affinity;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionWithAffinityTemplate<EditingStrategy>;
 extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionWithAffinityTemplate<EditingInComposedTreeStrategy>;
 
 using PositionWithAffinity = PositionWithAffinityTemplate<EditingStrategy>;
 using PositionInComposedTreeWithAffinity = PositionWithAffinityTemplate<EditingInComposedTreeStrategy>;
 
 } // namespace blink
 
 #endif // PositionWithAffinity_h