Put the summary of the bug you're having here

What I expected to happen was...:
I was testing the new performance improvements, I changed my render distance to 20 chunks

What actually happened was...:
Screen tearing occured and the graphics became extremely glitchy.

Steps to Reproduce:
1. Downloaded the new 14w30c jar in the launcher and started the game
2. changed render distance to 20 chunks in single player in an old world
3. Screen goes extremely glitchy, unplayable.

Here is video evidence, how it helps: http://youtu.be/_1gThgx60PA