The ornamental design for a mirror, as shown and described.
FIG. 1 is a perspective view of a mirror showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof;
FIG. 9 is a perspective view of the mirror shown in a covered state; and,
FIG. 10 is a perspective view of the mirror in condition of use.
The broken lines in the drawings depict portions of the mirror that form no part of the claimed design. The additional broken lines in the FIGS. 9 and 10 are to show environment and form no part of the claimed design.