FIG. 1 is a perspective view of a high chair cushion, showing my new design, the broken lines are for environmental purposes only and form no part of the claimed design;

FIG. 2 is a top plan view of the cushion;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a left-side elevational view thereof; and,

FIG. 7 is a right-side elevational view thereof.