the single-player screen is not behaving as it should!

The map choosing screen is moving very quickly. But only if you enter maximized screen.

I expected to go to singel player to create a world to look at the snapshot (14w11b)

I opened the single-player menu and it seemed all normal, but when I putt my screen in the maximized mode (not full screen) It just spaced out.
Video:
http://gyazo.com/aca60f549a46e212343789de714d8fe3
(make sure to use the MP4 format it displays better)

Steps to Reproduce:
1. launch minecraft (mac)
2. Choose snapshot 14w10b
3. go to "singleplayer"
4. maximize screen, and it should appear!

-stormer1267