When ever you are in minecraft and press F11 to go full screen and then press it again to exit full screen the minecraft window become unresizible and you must quit the game and restart it in order to resize it.
It was to hard to try to upload pictures of this so I made a short video, however the video was just 3.0 MB to large to upload to the post so here's the link to my dropbox:
https://www.dropbox.com/s/0yujomva1ec5obf/2016-01-22-0932-12.mp4?dl=0
Duplicate of MC-68754.