The ornamental design for a frontcover of a display device, as shown and described.
FIG. 1 is a front perspective view of a front cover of a display device in accordance with our new design;
FIG. 2 is an another front perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a left view thereof;
FIG. 5 is a right view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
There is no design feature to be shown in the rear views of the front cover, and thus the rear views of the front cover are omitted therein. The broken lines immediately adjacent the claimed areas represent the bounds of the claimed design while all other broken lines are directed to environment and are for illustrative purposes only. The broken lines form no part of the claimed design.