The new version of Flow is pushing us to specify all of these type params. Presumably Flow was always unable to infer them, but the new version is stricter about forcing type params when they can't be inferred.
NOTE: CI will fail on this diff. I considered the possibility of fixing Flow errors BEFORE upgrading Flow, but it wasn't possible... in some cases, the fixes to support the new version of Flow caused errors in the old version. I could have hidden these type errors with $FlowFixMe lines and then later revert those, but that seemed like too much busy work.
Depends on D9993