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 our new design;
FIG. 2 is a perspective view of the top, rear and left side thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear 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; and,
FIG. 8 is a bottom view thereof.
The dashed broken lines in the drawings illustrate unclaimed portions of the chair and form no part of the claimed design. The dot-dashed lines in FIGS. 1,2,4-6, and 8 show the boundary between claimed and unclaimed subject matter and form no part of the claimed design.