Flying Mob Pathfinding Causes Severe Lag

Windows_Minecraft - Noticed in 1.2.3, still observed in release 547645

Summary: First noticed in Dropper of Horrors, mobs that use flight pathfinding seem to cause enormous amounts of lag. When testing the map on Mid-tier devices, they were noticing horrible performance, and did the following to diagnose:

We did a bunch to try and see why it was breaking.

• removing all (as much as we could find) command blocks) = no noticeable change
• removing all the cows = small change 5fps
• removing all creepers (not sure how many we deleted, tried to get a number but on the debug Xbox wasn't showing) = 40+ fps increase

There were 13 of this mob in the map when it was tested. The mob was using the same behavior as bats, but we were using the creeper so we could take advantage of the charged effect. We are currently using similar behaviors in one of our Christmas maps, as well as in Escape from BLOZARK.

Impact: Worlds using custom mobs that fly will crash/perform poorly on low and mid-tier devices. The worlds will not meet performance standards, and thus will be withheld from releasing on the Marketplace.

Repro Steps:
1. Talk to Quinn/George to get "Noxcrew-DropperofHorrors-07-10-2017_Painting_1024.zip" from our slack.
2. Creepers (Greg the Popcorn Ghost) are already flying around the map.

Observed Results:
Poor performance

Expected Results:
Good performance

Screenshots/Videos attached: No