Introduce nextPositionOf() for VisiblePosition

Source/core/editing/VisiblePosition.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Portions Copyright (c) 2011 Motorola Mobility, 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
@@ skipping 46 matching lines @@
 VisiblePosition::VisiblePosition(const PositionInComposedTree& pos, TextAffinity affinity)
 {
     init(pos, affinity);
 }
 
 VisiblePosition::VisiblePosition(const PositionWithAffinity& positionWithAffinity)
 {
     init(positionWithAffinity.position(), positionWithAffinity.affinity());
 }
 
-VisiblePosition VisiblePosition::next(EditingBoundaryCrossingRule rule) const
+// TODO(yosin) We should move |nextPositionOf()| to "VisibleUnits.cpp".
+VisiblePosition nextPositionOf(const VisiblePosition& visiblePosition, EditingBoundaryCrossingRule rule)
 {
-    VisiblePosition next(nextVisuallyDistinctCandidate(m_deepPosition), m_affinity);
+    VisiblePosition next(nextVisuallyDistinctCandidate(visiblePosition.deepEquivalent()), visiblePosition.affinity());
 
     switch (rule) {
     case CanCrossEditingBoundary:
         return next;
     case CannotCrossEditingBoundary:
-        return honorEditingBoundaryAtOrAfter(next);
+        return visiblePosition.honorEditingBoundaryAtOrAfter(next);
     case CanSkipOverEditingBoundary:
-        return skipToEndOfEditingBoundary(next);
+        return visiblePosition.skipToEndOfEditingBoundary(next);
     }
     ASSERT_NOT_REACHED();
-    return honorEditingBoundaryAtOrAfter(next);
+    return visiblePosition.honorEditingBoundaryAtOrAfter(next);
 }
 
 VisiblePosition previousPositionOf(const VisiblePosition& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     Position pos = previousVisuallyDistinctCandidate(visiblePosition.deepEquivalent());
 
     // return null visible position if there is no previous visible position
     if (pos.atStartOfTree())
         return VisiblePosition();
 
@@ skipping 683 matching lines @@
     else
         fprintf(stderr, "Cannot showTree for (nil) VisiblePosition.\n");
 }
 
 void showTree(const blink::VisiblePosition& vpos)
 {
     vpos.showTreeForThis();
 }
 
 #endif