The ornamental design for a mirror, as shown and described.
FIG. 1 is a first perspective view of a mirror showing my new design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is aback view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof;
FIG. 9 is an enlarged view of the selected portion in FIG. 1; and,
FIG. 10 is an enlarged view of the selected portion in FIG. 2.
The broken lines shown in the drawings depict portions of the mirror in which the design is embodied that form no part of the claimed design. The dash-dot broken lines in the figures are demarcating enlarged areas and form no part of the claimed design.