The GNOME Shell comes with built in screen recording facilities.
The Control+Shift+Alt+R keybinding starts and stops the screen recording. A red circle together with a small green rectangle are displayed in the bottom right corner of the screen when a recording is in progress.
After recording is finished, a file named shell-%d%u-%c.webm is created in your home directory. In the filename, %d is the date, %u is a string that makes the filename unique, and %c is a numeric counter that is incremented each time a recording is made within a single GNOME Shell session.