The ornamental design for a mirror, as shown and described.
FIG. 1 is a front perspective view of a mirror according to an embodiment of the invention.
FIG. 2 is a front elevational view of a mirror according to an embodiment of the invention.
FIG. 3 is a side elevational view of a mirror according to an embodiment of the invention. The view from the opposite side is a mirror image thereof; and,
FIG. 4 is a top view of a mirror according to an embodiment of the invention.
The broken lines on the mirror are for the purpose of illustrating attachment means for the article and form no part of the claimed invention.