Move parentEditingBoundary() to VisibileUnits.cpp from Position.cpp.

Source/core/editing/Position.h

 /*
  * Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 220 matching lines @@
     int m_offset;
     PositionAnchorType m_anchorType;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionAlgorithm<EditingStrategy>;
 extern template class CORE_EXTERN_TEMPLATE_EXPORT PositionAlgorithm<EditingInComposedTreeStrategy>;
 
 using Position = PositionAlgorithm<EditingStrategy>;
 using PositionInComposedTree = PositionAlgorithm<EditingInComposedTreeStrategy>;
 
-// TODO(yosin) We should make |parentEditingBoundary()| as static function
-// in "VisibleUnits.cpp", since it is used only there.
-CORE_EXPORT Node* parentEditingBoundary(const Position&);
-CORE_EXPORT Node* parentEditingBoundary(const PositionInComposedTree&);
-
 template <typename Strategy>
 bool operator==(const PositionAlgorithm<Strategy>& a, const PositionAlgorithm<Strategy>& b)
 {
     if (a.isNull())
         return b.isNull();
 
     if (a.anchorNode() != b.anchorNode() || a.anchorType() != b.anchorType())
         return false;
 
     if (!a.isOffsetInAnchor()) {
@@ skipping 187 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::Position&);
 void showTree(const blink::Position*);
 #endif
 
 #endif // Position_h