The ornamental design for a chair, as shown and described.
FIG. 1 is a perspective view of a chair, showing my new design;
FIG. 2 is a right elevation view thereof, the left elevation view being a mirror image thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The evenly-sized broken lines shown in the drawings depict portions of the chair that form no part of the claimed design, while unevenly-sized broken lines consisting of dash-dot-dash lines in the drawings depict the boundary of the claimed invention and it is understood that the claim extends to the boundary that forms no part of the claimed design.