The ornamental design for a cushioned supportbase for a tablet computer, as shown and described.
FIG. 1 is a top, front and right side perspective view of a cushioned support base for a tablet computer showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a top, front and right side perspective view thereof, shown in condition of use with a tablet computer supported on the front face disclosed in broken lines to illustrate an environment; and,
FIG. 9 is a top, rear and left side perspective view thereof, shown in condition of use with a tablet computer supported on the rear face.
The broken lines showing a tablet computer in FIGS. 8-9 represent environmental structure and form no part of the claimed design.