Start/stop recording your GNOME 3 Desktop by pressing the Ctrl+Shift+Alt+R key combination.
The first time when you press this key combination, GNOME 3 will start recording your Desktop. A red circle is displayed in the bottom right corner of the screen when the recording is in progress. Pressing the same key combination a second time will stop the recording.
After the recording is finished, a file named 'shell-%d%u-%c.webm' is saved in the home directory. In the filename, %d is the date, %u is a string that makes the filename unique, and %c is a counter that is incremented each time a recording is made within a single gnome-shell session. The recording is saved in the WebM format.
Now we can do our Red Hat JBoss screencasts without much trouble, but next step is to get audio track included. ;-)