FlatCombiner: Make `inflight` a queue (didn't seem to solve things)
FlatCombiner: Make `inflight` a queue (didn't seem to solve things)

buaasun/grappa,buaasun/grappa,alexfrolov/grappa,uwsampa/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa,uwsampa/grappa,alexfrolov/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa,uwsampa/grappa,uwsampa/grappa,uwsampa/grappa,buaasun/grappa,alexfrolov/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa