Introduce composed tree version of nextVisuallyDistinctCandidate()

Source/core/editing/EditingUtilities.h

Index: Source/core/editing/EditingUtilities.h
diff --git a/Source/core/editing/EditingUtilities.h b/Source/core/editing/EditingUtilities.h
index 86c827d3804f31f15438aa5ea26d7c7fdc06fff8..0a396dfb4de92cbcd2db1430ccc0a5b5133b12ba 100644
--- a/Source/core/editing/EditingUtilities.h
+++ b/Source/core/editing/EditingUtilities.h
@@ -162,7 +162,8 @@ PositionInComposedTree nextCandidate(const PositionInComposedTree&);
 Position previousCandidate(const Position&);
 PositionInComposedTree previousCandidate(const PositionInComposedTree&);
 
-Position nextVisuallyDistinctCandidate(const Position&);
+CORE_EXPORT Position nextVisuallyDistinctCandidate(const Position&);
+CORE_EXPORT PositionInComposedTree nextVisuallyDistinctCandidate(const PositionInComposedTree&);
 Position previousVisuallyDistinctCandidate(const Position&);
 PositionInComposedTree previousVisuallyDistinctCandidate(const PositionInComposedTree&);