Just recently from this new update, chests, item frames, villagers, zombies, armor stands (just about anything) will appear too look "see-through" and transparent.

Steps to Reproduce:
1. Login to snapshot 15w47a
2. Create a Single Player World
3. Place chests downs or other entities and look at them from certain angles until they change to look "see-through" (Walking around the chests or items helps)