This bug can be recreated using the following steps:

1) Launch minecraft to main menu
2) Move the mouse to the bottom right corner and click and drag the corner to manipulate the size of the window.
3) While holding the corner, click and drag the window to make it bigger (or smaller) at a VERY FAST rate. (The best way to describe this movement is to jerk the mouse back and forth with about 6 inches between point A and point B at a very fast rate.)Essentially, try to make the minecraft window go from it's default size to covering your entire screen in less than half a second.