Method acknowledgePrior

src/server/chat.js:250–259

(sender, signature)

  }

  acknowledgePrior (sender, signature) {
    for (let i = 0; i < this.length; i++) {
      const [a, b] = this[i]
      delete this.m[a]
      if (a === sender && b === signature) {
        this.splice(0, i)
        break
      }
    }
  }

  // Once we've acknowledged that the client has saw the messages we sent,
  // we delete it from our map & pending list. However, the client may keep it in