Slime mob spawners spawn slimes only in slime chunks

How to reproduce

1. Create a superflat world with the seed: 7606204815140416435
2. First, execute these commands: /gamerule doMobSpawning false and /kill @e[type=!minecraft:player] (untill all entities are dead)
3. Teleport to 102 5 223 using /tp @s 102 5 223
4. Execute the command 'Spawner 1', afterwards execute command 'Spawner 2'
5. Observe the two spawners, only 'Spawner 1' will spawn slimes

   Spawner 1: /setblock 98 6 229 spawner{SpawnData:{id:slime},SpawnCount:2,MaxNearbyEntities:100,Delay:300,MaxSpawnDelay:500,RequiredPlayerRange:16} replace
   

   Spawner 2: /setblock 64 6 229 spawner{SpawnData:{id:slime},SpawnCount:2,MaxNearbyEntities:100,Delay:300,MaxSpawnDelay:500,RequiredPlayerRange:16} replace
   

Video proof: http://usetapes.com/v/TQQ1qEYHiC