When a player is nearby, blazes occasionally attempt to shoot fireballs at the player through walls, ceilings and floors. Only one fireball per salvo is shot, instead of the usual three. A line of sight is not required for this to happen, and the effect occurs both with transparent and opaque blocks, tested with glass and nether brick with a setup as shown in the screenshot.

This seems to be new behaviour that is introduced in this snapshot, and does not occur in 1.8.8 or the 15w35e snapshot, but could be related to MC-47699