It seems that with the new 1.8 snapshots, when creating a new world in that version, there're are not spawning any chest in dugeons or spawner rooms. I've tested this by loading a world in a couple version of the 1.8 snapshots and creating exacly the same world in 1.7.
The worlds which were created in the 1.8 snapshots never had any chests in the spawner rooms, while worlds created in 1.7 did.