Original commit message from CVS:
More EOS changes.
When a bin2 is found inside a bin1, we add the bin2 to the EOS providers
of the bin1. When there is nothing more to schedule in bin1 and bin2 has
fired EOS, bin1 is in EOS.
The queue overrides the EOS notification and calls EOS on the src pad
when the queue is empty and the sink pad is in EOS.