Make PositionAlgorithm<Strategy>::next() to use Strategy::index()

Source/core/dom/Position.cpp

Index: Source/core/dom/Position.cpp
diff --git a/Source/core/dom/Position.cpp b/Source/core/dom/Position.cpp
index 68fc3ac705d545b561cbff4d8e78c1867d51bd6c..1b381a296ce602913504801ffc41e927ec631e83 100644
--- a/Source/core/dom/Position.cpp
+++ b/Source/core/dom/Position.cpp
@@ -464,7 +464,7 @@ PositionAlgorithm<Strategy> PositionAlgorithm<Strategy>::next(PositionMoveType m
     }
 
     if (ContainerNode* parent = Strategy::parent(*node))
-        return createLegacyEditingPosition(parent, node->nodeIndex() + 1);
+        return createLegacyEditingPosition(parent, Strategy::index(*node) + 1);
     return PositionAlgorithm<Strategy>(*this);
 }