The ornamental design for a chair, as shown and described.
FIG. 1 is a perspective view of the top, front and right side 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 right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a sectional view thereof taken along the line 8-8 of FIG. 2.
The claimed design is indicated by the relatively dark portions in the figures. The relatively light portions form no part of the claimed design. The broken dashed lines following the perimeter of the relatively light portions form no part of the claimed design.