The ornamental design for a gascap, as shown and described.
FIG. 1 is an upper perspective view of a gas cap showing the new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a right side elevation view thereof, the left side elevation view, front side elevation view and back side elevation view being mirror images thereof;
FIG. 4 is a sectional view thereof, taken along the line 4-4 in FIG. 2; and,
FIG. 5 is a side elevation view taken between the front and right sides along the line 5-5 in FIG. 2.
The portions of the Figures shown in phantom lines are not part of the design sought to be protected and are provided for illustrative and environmental purposes only.