Have StyledMarkupSerializer work on the Composed tree

Source/core/editing/VisibleSelection.h

Index: Source/core/editing/VisibleSelection.h
diff --git a/Source/core/editing/VisibleSelection.h b/Source/core/editing/VisibleSelection.h
index f50f0a7e989479c3ef593bfa1c44186e0df2a568..8c309ae336dcd0ade98d405cc7a2273f661ed94c 100644
--- a/Source/core/editing/VisibleSelection.h
+++ b/Source/core/editing/VisibleSelection.h
@@ -120,6 +120,7 @@ public:
     PassRefPtrWillBeRawPtr<Range> toNormalizedRange() const;
     bool toNormalizedPositions(Position& start, Position& end) const;
     static void normalizePositions(const Position& start, const Position& end, Position* normalizedStart, Position* normalizedEnd);
+    static void normalizePositions(const PositionInComposedTree& start, const PositionInComposedTree& end, PositionInComposedTree* outStart, PositionInComposedTree* outEnd);
 
     Element* rootEditableElement() const;
     bool isContentEditable() const;