The ornamental design for a childsafetyseat, as shown and described.
Cross-reference to related application incorporates by reference U.S. application Ser. No. 15/243,241.
FIG. 1 is a front perspective view of the child safety seat showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing of portions of the child safety seat is included for the purpose of illustrating environmental structure and forms no part of the claimed design.