Make inSameLine() in VisibleUnits.cpp to work with positions in composed tree

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/dom/Position.h"
 #include "core/editing/TextAffinity.h"
@@ skipping 25 matching lines @@
     {
         visitor->trace(m_position);
     }
 
 private:
     PositionType m_position;
     EAffinity m_affinity;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionWithAffinityTemplate<Position>;
+extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionWithAffinityTemplate<PositionInComposedTree>;
 
 using PositionWithAffinity = PositionWithAffinityTemplate<Position>;
+using PositionInComposedTreeWithAffinity = PositionWithAffinityTemplate<PositionInComposedTree>;
 
 } // namespace blink
 
 #endif // PositionWithAffinity_h