The ornamental design for a chair, as shown and described.
FIG. 1 is an isometric view of a chair from a first, top perspective;
FIG. 2 is a front view of FIG. 1;
FIG. 3 is a back view of FIG. 1;
FIG. 4 is a top view of FIG. 1;
FIG. 5 is a bottom view of FIG. 1;
FIG. 6 is a side view of FIG. 1, an opposite side of the embodiment of FIG. 1 being a substantially identical mirror image; and,
FIG. 7 is an isometric view of FIG. 1 from a second, bottom perspective.
The broken lines showing certain portions of the chair and certain portions of the bottom support assembly of the embodiment of FIG. 1 are for illustrative purposes only and form no part of the claimed design.