As used in this chapter, unless otherwise specifically provided, the term “probation officer” or “social worker” shall include the juvenile probation officer or the person who is both the juvenile probation officer and the adult probation officer, and any social worker in a county welfare department or any social worker in a California Indian tribe or any out-of-state Indian tribe that has reservation land that extends into the state that has authority, pursuant to an agreement with the department concerning child welfare services or foster care payments under the Aid to Families with Dependent Children program when supervising dependent children of the juvenile court pursuant to Section 272 by order of the court under Section 300, and the term “department of probation” shall mean the department of juvenile probation or the department wherein the services of juvenile and adult probation are both performed.