I claim the ornamental design for the combination bib and tray, as shown and described.
FIG. 1 is a front perspective view of combination bib and tray as worn by a user with the tray down; the broken lines showing environmental structure form no part of the claimed design;
FIG. 2 is a front perspective view thereof showing the tray up;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a front elevational view thereof;
FIG. 7 is a side elevational view thereof; and,
FIG. 8 is another side elevational view, opposite the side shown in FIG. 7.