The ornamental design for a frontbumper for an automobile, as shown and described.
FIG. 1 is a front elevational view of a front bumper for an automobile showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side perspective view thereof;
FIG. 6 is a top, front and right side perspective view thereof; and,
FIG. 7 is a bottom, front and left side perspective view thereof.
The rear view of the front bumper forms no part of the claimed design. The inside surfaces of the front bumper visible in FIGS. 2, 6 and 7 form no part of the claimed design since the inside surfaces are hidden when the front bumper is mounted to the automobile.