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 front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a perspective view thereof with the cushion slightly lifted.
A bottom view thereof is omitted since it does not contain ornamental features. The heavy broken line showing of stitch lines forms portions of the claimed design, while the light broken line showing of portions of the chair forms no part of the claimed design. The dot-dash broken lines in FIG. 7 define the boundaries of the claimed design and form no part thereof.