The ornamental design for a shelf for refrigerator, as shown and described.
FIG. 1 is a top front perspective view of a shelf for refrigerator showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is bottom front perspective view thereof;
FIG. 9 is a cross-sectional view taken along the line 9-9 of FIG. 2;
FIG. 10 is another bottom front perspective view thereof showing an example upper shelf in dashed broken lines to provide sample environment;
FIG. 11 is another front view thereof showing an example refrigerator in dashed broken lines to provide sample environment; and,
FIG. 12 is another front view thereof showing an example refrigerator in dashed broken lines to provide sample environment and depicting the shelf in an alternative position.
The dashed broken lines in the drawings represent example environment and portions of the shelf for refrigerator that form no part of the claimed design.