lrn@google.com
1315656027
These callbacks will be called when the broadcast stream no longer has any listeners, or when it gets a listener after having none. The callback is provided with a StreamSubscription-like object where it can pause/resume/cancel the underlying subscription on the original stream. BUG=http://dartbug.com/11289 R=floitsch@google.com Review URL: https://codereview.chromium.org//17490002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@24776 260f80e4-7a28-3924-810f-c04153c831b5