Whether the subscription would need to buffer events.
This is the case if the controller's stream has a listener and it is paused, or if it has not received a listener yet. In that case, the controller is considered paused as well.
A broadcast stream controller is never considered paused. It always forwards its events to all uncanceled subscriptions, if any, and let the subscriptions handle their own pausing and buffering.
@override bool get isPaused => _controller.isPaused;