The ornamental design for a non-slip dog bowl, as shown and described.
FIG. 1 is a perspective view of a design for a non-slip dog bowl;
FIG. 2 is a side view thereof;
FIG. 3 is another side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a back view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines illustrate portions of the non-slip dog bowl that form no part of the claimed design. The dash-dot broken lines represent the bounds of the claim and form no part of the claimed design.