An ornamentaldesign for an office chair, as shown and described in the attached drawings.
FIG. 1 is a front view of a first embodiment of an office chair embodying our design;
FIG. 2 is a top view thereof;
FIG. 3 is a left side view thereof, the right side view being substantially a mirror image thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left, rear isometric view thereof;
FIG. 6 is a front view of a second embodiment of an office chair embodying our design;
FIG. 7 is a top view thereof;
FIG. 8 is a left side view thereof, the right side view being substantially a mirror image thereof;
FIG. 9 is a rear view thereof; and,
FIG. 10 is a left, rear isometric view thereof.
The base for the office chair of the claimed design is illustrated herein in phantom outline for environmental purposes and forms no part of the claimed design.