Confusing example in Iterators/Generators FAQ

[Ms2ger]

[Symbol.iterator](){
  return {
    next: () => ({ value: this.next(), done: this[done] })
  , return: () => ({ value: this.resolve(), done: this[done] })
  , throw: () => ({ value: this.reject(), done: this[done] })
  }
}

What is done in this[done]?