Summary:
It can be a pain to debug slow network issues, especially with the iOS simulator which doesn't have a network link conditioner. This makes it really easy and predictable by simply adding a `setTimeout` around calling `sendRequest`.
Changelog:
[General] [Added] - DEBUG_NETWORK_SEND_DELAY can be used to simulate slow network.
Reviewed By: PeteTheHeat
Differential Revision: D19236911
fbshipit-source-id: 14762c7e0c6408a8364aa569c482729a7a1fe740