sample/throttleLast doesn't call unsubscribe

[zsxwing]

In the following code, I would expect the "cleanup" message to be printed three times, but on the last case (o1.throttleLast(...)) it isn't.

 def o = rx.Observable.create({ subscriber ->
        subscriber.add(Subscriptions.create({ println "cleanup" }))
    })

    o.subscribe({})
        .unsubscribe() // prints

    o.take(1)
        .subscribe({})
        .unsubscribe();  // prints

    o.throttleLast(1, TimeUnit.MILLISECONDS)
        .subscribe({})
        .unsubscribe() // doesn't print

Reported by juanedi in http://stackoverflow.com/questions/27428757/unsubscriptions-not-cascading-back-to-base-observable-in-rxjava