The ornamental design for a mirror, as shown and described.
FIG. 1 is a perspective view of the mirror of the present invention.
FIG. 2 is a left side elevational view of the mirror of FIG. 1, the right side elevational view being a mirror reflection of the left side elevational view.
FIG. 3 is a top plan view of the mirror of FIG. 1, the bottom plan view being a mirror reflection of the top plan view.
FIG. 4 is a front elevational view of the mirror of FIG. 1; and,
FIG. 5 is a rear elevational view of the mirror of FIG. 1.