What I expected to happen was...:
I would be able to maximize the window again after going into and exiting fullscreen mode

What actually happened was...:
After I exited fullscreen mode, I couldn't hit maximize or resize the window

Steps to Reproduce:
1. Go into 15w38a
2. Go into fullscreen mode by clicking F11 on keyboard
3. Leave fullscreen mode by pressing F11 again
4. Try to click the maximize button in the top right, it is grayed out and you can't click it

Picture:
http://prntscr.com/8h5tbw