Summary:
changelog: [internal]
Exposes a new flag on RuntimeScheduler: `unstable_getIsSynchronous`. Flag indicates if the current code is run synchronously and therefore commit phase should be synchronous.
Unit tests will be added later, to keep this diff short. This code path is not executed yet.
Reviewed By: mdvacca, ShikaSD
Differential Revision: D32677814
fbshipit-source-id: e01d4fff7e716d627ff99fe104965851138c3aef