It is possible to enlarge the embedded Editor to a size that is bigger than the containing box. In this case the control element for
changing the size (the one in the lower right corner) is invisible and unreachable. Therefore you can not shrink it again.

The browsers show different behaviours if you fill up the lines now.
Here are some results of our experiments:
Chrome:
If you fill up the line with single characters (without copy and paste!) Chrome shrinks the editor by itself to the maximum size.
If you use copy and paste it sometimes "scrolls" to the right end so you can see the control in the lower right side again without
showing a scroll bar.
The size of the Editor is saved (neither Login-/Logout nor F5 fix it)

Firefox:
After changing the size we never saw the control element again.