Hi all, Meng found a bug in `slave.cpp`, where the proper fix requires collecting futures in order. Currently every `collect` call spawns it's own actor, so for two `collect` calls, even though their futures are satisfied in order, they may finish out-of-order. So we need some libprocess changes to have the ability to collect futures in the same actor. Here I have two proposals:
1. Add a new `collect` interface that takes an actor as a parameter. 2. Introduce `process::Executor::collect()` for this. Any opinion on these two options?