The ornamental design for a base for an electronicdisplay device, as shown and described.
FIG. 1 is a front perspective view of a base for an electronic display device.
FIG. 2 is rear perspective view thereof.
FIG. 3 is a front view thereof.
FIG. 4 is a rear view thereof.
FIG. 5 is a top view thereof.
FIG. 6 is a bottom view thereof.
FIG. 7 is a left side view thereof; and,
FIG. 8 is a right side view thereof.
The base for the electronic display device is not limited to the scale shown in the figures. The broken lines in FIGS. 1-5, 7, and 8 illustrate portions of the base for an electronic display device that form no part of the claimed design. The shade lines in the figures, if any, show contour and not surface ornamentation.