Don't allow DragListener._modelPoint to turn into a reference to a scratch vector that is changed elsewhere, see https://github.com/phetsims/friction/issues/202
Don't allow DragListener._modelPoint to turn into a reference to a scratch vector that is changed elsewhere, see https://github.com/phetsims/friction/issues/202

phetsims/scenery,phetsims/scenery,phetsims/scenery