I claim, the ornamental design for a mascara brush, as shown and described.
FIG. 1 is an isometric view of a mascara brush, showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a first side elevation view thereof;
FIG. 5 is a second side elevation view thereof;
FIG. 6 is a top plan view thereof, enlarged to depict my claimed design more clearly; and,
FIG. 7 is a bottom plan view thereof, enlarged to depict my claimed design more clearly.
The dash-dot-dash lines immediately adjacent to the shaded areas of the mascara brush represent unclaimed boundaries of the claimed design. The dot-dot lines showing the remainder of the mascara brush are for illustrative purposes only and form no part of the claimed design.