Hide canonicalPosition in VisiblePosition from header file

Source/core/editing/VisiblePosition.h

 /*
  * Copyright (C) 2004, 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 94 matching lines @@
     DECLARE_TRACE();
 
 #ifndef NDEBUG
     void debugPosition(const char* msg = "") const;
     void formatForDebugger(char* buffer, unsigned length) const;
     void showTreeForThis() const;
 #endif
 
 private:
     void init(const Position&, EAffinity);
-    Position canonicalPosition(const Position&);
 
     Position leftVisuallyDistinctCandidate() const;
     Position rightVisuallyDistinctCandidate() const;
 
     Position m_deepPosition;
     EAffinity m_affinity;
 };
 
 // FIXME: This shouldn't ignore affinity.
 inline bool operator==(const VisiblePosition& a, const VisiblePosition& b)
@@ skipping 18 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::VisiblePosition*);
 void showTree(const blink::VisiblePosition&);
 #endif
 
 #endif // VisiblePosition_h