Revert to using string ids for entities in firebase manual tests. (#2929)
Revert to using string ids for entities in firebase manual tests. (#2929)

The storage provider APIs haven't been updated to using Id objects yet, so the tests still need to pass in strings.
PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs