The ornamental design for a cosmeticcontainer, as shown and described.
1.-3. Cosmetic container
2.1 : Perspective
2.2 : Front
2.3 : Back
2.4 : Top
2.5 : Bottom
2.6 : Left
2.7 : Right
The broken line showing of the container is included for the purpose of illustrating portions of the cosmetic container and forms no part of the claimed design.