Introduce Position::nodeAsRangeLastNode

Source/core/dom/Position.h

Index: Source/core/dom/Position.h
diff --git a/Source/core/dom/Position.h b/Source/core/dom/Position.h
index b13b35af0d046393617cff3398225377b6ed0591..ca1f734dffab0a6b3e3144f152ad15b49bce713b 100644
--- a/Source/core/dom/Position.h
+++ b/Source/core/dom/Position.h
@@ -141,6 +141,9 @@ public:
     // |PositionIs::OffsetInAhcor| to behave as |Range| boundary point.
     Node* nodeAsRangeFirstNode() const;
 
+    // Similar to |nodeAsRangeLastNode()|, but returns a node in a range.
+    Node* nodeAsRangeLastNode() const;
+
     // Returns a node as past last as same as |Range::pastLastNode()|. This
     // function is supposed to used in HTML serialization and plain text
     // iterator. This position must be a |PositionIs::OffsetInAhcor| to