[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] angular.io application / infrastructure changes
[ ] Other... Please describe:

const ee = new EventEmitter();
ee.pipe(map(() => true)).subscribe().unsubscribe(); // can any other operator
console.log('EventEmitter', ee.observers.length); // 1 - wrong, should be 0

// This simulates `FilterSubscriber` or `MapSubscriber`
const subscriber = new Subscriber(val => {});
subscriber.add(() => console.log('Subscriber disposed')); // This is never called - wrong

const ee2 = new EventEmitter();
ee2.subscribe(subscriber).unsubscribe();
console.log('EventEmitter - Subscriber', ee2.observers.length); // 0
// This did unsubscribe because we're holding the direct `Subscription` for `EventEmitter`
// but didn't trigger the teardown function. The teardown function is
// where it unsubscribes from its parent in `FilterSubscriber` or `MapSubscriber`.

const s = new Subject();
s.pipe(map(() => true)).subscribe().unsubscribe();
console.log(s.observers.length); // 0 - correct

it('remove a subscriber subscribed after applying operators with pipe()', () => {
  const sub = emitter.pipe(filter(() => true)).subscribe();
  expect(emitter.observers.length).toBe(1);
  sub.unsubscribe();
  expect(emitter.observers.length).toBe(0);
});

it('error thrown inside an Rx chain propagates to the error handler and disposes the chain',
   () => {
     let errorPropagated = false;
     emitter.pipe(filter(() => { throw new Error(); }), )
         .subscribe(() => {}, err => errorPropagated = true, );

     emitter.next(1);

     expect(errorPropagated).toBe(true);
     expect(emitter.observers.length).toBe(0);
   });

[ ] Yes
[x] No