Introduce composed tree version of nextVisuallyDistinctCandidate()

Source/core/editing/EditingUtilities.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 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 342 matching lines @@
 }
 
 PositionInComposedTree nextCandidate(const PositionInComposedTree& position)
 {
     return nextCandidateAlgorithm<EditingInComposedTreeStrategy>(position);
 }
 
 // |nextVisuallyDistinctCandidate| is similar to |nextCandidate| except
 // for returning position which |downstream()| not equal to initial position's
 // |downstream()|.
-Position nextVisuallyDistinctCandidate(const Position& position)
+template <typename Strategy>
+static PositionAlgorithm<Strategy> nextVisuallyDistinctCandidateAlgorithm(const PositionAlgorithm<Strategy>& position)
 {
     if (position.isNull())
-        return Position();
+        return PositionAlgorithm<Strategy>();
 
-    PositionIterator p(position);
-    Position downstreamStart = mostForwardCaretPosition(position);
+    PositionIteratorAlgorithm<Strategy> p(position);
+    const PositionAlgorithm<Strategy> downstreamStart = mostForwardCaretPosition(position);
 
     p.increment();
     while (!p.atEnd()) {
-        Position candidate = p.computePosition();
+        PositionAlgorithm<Strategy> candidate = p.computePosition();
         if (isVisuallyEquivalentCandidate(candidate) && mostForwardCaretPosition(candidate) != downstreamStart)
             return candidate;
 
         p.increment();
     }
 
-    return Position();
+    return PositionAlgorithm<Strategy>();
+}
+
+Position nextVisuallyDistinctCandidate(const Position& position)
+{
+    return nextVisuallyDistinctCandidateAlgorithm<EditingStrategy>(position);
+}
+
+PositionInComposedTree nextVisuallyDistinctCandidate(const PositionInComposedTree& position)
+{
+    return nextVisuallyDistinctCandidateAlgorithm<EditingInComposedTreeStrategy>(position);
 }
 
 template <typename Strategy>
 PositionAlgorithm<Strategy> previousCandidateAlgorithm(const PositionAlgorithm<Strategy>& position)
 {
     PositionIteratorAlgorithm<Strategy> p(position);
 
     p.decrement();
     while (!p.atStart()) {
         PositionAlgorithm<Strategy> candidate = p.computePosition();
@@ skipping 1164 matching lines @@
     // if the selection starts just before a paragraph break, skip over it
     if (isEndOfParagraph(visiblePosition))
         return mostForwardCaretPosition(visiblePosition.next().deepEquivalent());
 
     // otherwise, make sure to be at the start of the first selected node,
     // instead of possibly at the end of the last node before the selection
     return mostForwardCaretPosition(visiblePosition.deepEquivalent());
 }
 
 } // namespace blink