The ornamental design for a mirror, substantially as shown and described.
FIG. 1 is a bottom, right side, and front perspective view showing my new design;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The convex surface portions, as viewed from the front of the mirror, have a contrasting appearance above and below the straight line dividing the convex portion.