0e6cc375c4
On a done event, the subscription is stale, but the forwarding stream uses the presence of the subscription as a state-marker for it being useful. Changed to null the subscription on a done event. BUG=http://dartbug.com/8311 Review URL: https://codereview.chromium.org//12213009 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@18212 260f80e4-7a28-3924-810f-c04153c831b5