UndoPosRef is not visible outside, but used in several methods in parametrization.

Here is report from sigtest:

Hidden class found: javax.swing.text.GapContent$UndoPosRef in method protected void javax.swing.text.GapContent.updateUndoPositions(java.util.Vector<javax.swing.text.GapContent$UndoPosRef>,int,int) in class javax.swing.text.GapContent
Hidden class found: javax.swing.text.StringContent$UndoPosRef in method protected void javax.swing.text.StringContent.updateUndoPositions(java.util.Vector<javax.swing.text.StringContent$UndoPosRef>) in class javax.swing.text.StringContent
Hidden class found: javax.swing.text.GapContent$UndoPosRef in method protected java.util.Vector<javax.swing.text.GapContent$UndoPosRef> javax.swing.text.GapContent.getPositionsInRange(java.util.Vector<javax.swing.text.GapContent$UndoPosRef>,int,int) in class javax.swing.text.GapContent
Hidden class found: javax.swing.text.StringContent$UndoPosRef in method protected java.util.Vector<javax.swing.text.StringContent$UndoPosRef> javax.swing.text.StringContent.getPositionsInRange(java.util.Vector<javax.swing.text.StringContent$UndoPosRef>,int,int) in class javax.swing.text.StringContent