Avoid crashing when a closed StreamIterator is cancelled

Avoid crashing when a closed StreamIterator is cancelled

BUG=
R=floitsch@google.com, lrn@google.com

Committed: https://code.google.com/p/dart/source/detail?r=43460

[sigurdm, 2015-02-03 14:35:09]

Patchset #1 (id:1) has been deleted

[sigurdm, 2015-02-03 14:35:33]

sigurdm@google.com changed reviewers:
+ lrn@google.com

[floitsch, 2015-02-03 19:25:38]

floitsch@google.com changed reviewers:
+ floitsch@google.com

[floitsch, 2015-02-03 19:25:38]

LGTM.
But give Lasse a chance to review too.

[Lasse Reichstein Nielsen, 2015-02-04 10:03:42]

lgtm

https://chromiumcodereview.appspot.com/896793002/diff/20001/sdk/lib/async/str...
File sdk/lib/async/stream_impl.dart (right):

https://chromiumcodereview.appspot.com/896793002/diff/20001/sdk/lib/async/str...
sdk/lib/async/stream_impl.dart:1031: StreamSubscription subscription =
_subscription;
I think it would better to just do:
  if (subscription == null) return null;
here. The _subscription is only set to null in _clear, but that also sets _state
to _STATE_DONE, which will never change again. So, if _subscription is null,
then we know that all we will do is call _clear again before returning null,
which will do nothing.

[sigurdm, 2015-02-04 10:19:25]

New patchsets have been uploaded after l-g-t-m from
floitsch@google.com,lrn@google.com

[sigurdm, 2015-02-04 10:23:21]

Patchset #2 (id:40001) has been deleted

[sigurdm, 2015-02-04 10:23:57]

https://codereview.chromium.org/896793002/diff/20001/sdk/lib/async/stream_imp...
File sdk/lib/async/stream_impl.dart (right):

https://codereview.chromium.org/896793002/diff/20001/sdk/lib/async/stream_imp...
sdk/lib/async/stream_impl.dart:1031: StreamSubscription subscription =
_subscription;
On 2015/02/04 10:03:42, Lasse Reichstein Nielsen wrote:
> I think it would better to just do:
>   if (subscription == null) return null;
> here. The _subscription is only set to null in _clear, but that also sets
_state
> to _STATE_DONE, which will never change again. So, if _subscription is null,
> then we know that all we will do is call _clear again before returning null,
> which will do nothing.

Done.
Thanks!

[sigurdm, 2015-02-04 11:23:34]

Committed patchset #2 (id:60001) manually as 43460 (presubmit successful).