The ornamental design for a chair, as shown and described.
FIG. 1 is a perspective view of a chair showing a first embodiment of our new design;
FIG. 2 is a front view of the first embodiment;
FIG. 3 is a rear view of the first embodiment;
FIG. 4 is a left side view of the first embodiment;
FIG. 5 is a right side view of the first embodiment;
FIG. 6 is a top view of the first embodiment;
FIG. 7 is a perspective view of a chair showing a second embodiment of our new design;
FIG. 8 is a front view of the second embodiment;
FIG. 9 is a rear view of the second embodiment;
FIG. 10 is a left side view of the second embodiment;
FIG. 11 is a right side view of the second embodiment; and,
FIG. 12 is a top view of the second embodiment.
A bottom view of each of the embodiments 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.