Introduce {left,right}PositionOf() for VisiblePosition

Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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 357 matching lines @@
 
     TextDirection blockDirection = directionOfEnclosingBlock(visiblePosition.deepEquivalent());
     InlineBox* previouslyVisitedBox = 0;
     VisiblePosition current = visiblePosition;
     TextBreakIterator* iter = 0;
 
     CachedLogicallyOrderedLeafBoxes leafBoxes;
     Vector<UChar, 1024> string;
 
     while (1) {
-        VisiblePosition adjacentCharacterPosition = direction == MoveRight ? current.right() : current.left();
+        VisiblePosition adjacentCharacterPosition = direction == MoveRight ? rightPositionOf(current) : leftPositionOf(current);
         if (adjacentCharacterPosition.deepEquivalent() == current.deepEquivalent() || adjacentCharacterPosition.isNull())
             return VisiblePosition();
 
         InlineBoxPosition boxPosition = computeInlineBoxPosition(adjacentCharacterPosition.deepEquivalent(), TextAffinity::Upstream);
         InlineBox* box = boxPosition.inlineBox;
         int offsetInBox = boxPosition.offsetInBox;
 
         if (!box)
             break;
         if (!box->isInlineTextBox()) {
@@ skipping 1942 matching lines @@
 {
     return isVisuallyEquivalentCandidateAlgorithm<EditingStrategy>(position);
 }
 
 bool isVisuallyEquivalentCandidate(const PositionInComposedTree& position)
 {
     return isVisuallyEquivalentCandidateAlgorithm<EditingInComposedTreeStrategy>(position);
 }
 
 } // namespace blink