The ornamental design for an electronicdeviceholder for a child seat, as shown and described.
FIG. 1 is a perspective view of a child seat with an electronic device holder for a child seat, showing my new design;
FIG. 2 is an enlarged, front perspective view of the electronic device holder for a child seat of FIG. 1 with a slidable portion in an extended configuration and the straps in an opened configuration;
FIG. 3 is a front elevation view thereof with the slidable portion in a collapsed configuration;
FIG. 4 is a rear elevation view thereof;
FIG. 5 right side elevation view thereof;
FIG. 6 is a left side elevation view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken line showing of the child seat in the drawings is for illustrative purposes only and forms no part of the claimed design.