The ornamental design of a chairseat, as shown and described.
FIG. 1 is a perspective view showing the new design, the broken lines are for environmental purposes only and form no part of the claimed design;
FIG. 2 is a front view of the chair seat illustrated in FIG. 1, the broken lines are for environmental purposes only and form no part of the claimed design;
FIG. 3 is a side view of the chair seat illustrated in FIG. 1, the opposite side is a mirror image of that which is illustrated in this FIG. 3, the broken lines are for environmental purposes only and form no part of the claimed design;
FIG. 4 is a is top view of the chair seat illustrated in FIG. 1, the broken lines are for environmental purposes only and form no part of the claimed design;
FIG. 5 is a bottom view of the chair seat illustrated in FIG. 1, the broken lines are for environmental purposes only and form no part of the claimed design;
FIG. 6 is a rear view of the chair seat illustrated in FIG. 1, the broken lines are for environmental purposes only and form no part of the claimed design; and,
FIG. 7 is a second perspective view of the chair seat illustrated in FIG. 1, the broken lines are for environmental purposes only and form no part of the claimed design.