How to add new gesture files:
1. Obtain a chromebook with a test image and the input source in question
    (either onboard or plugged in).
2. Determine the input node of the input, e.g. /dev/input/event4.  Either:
    a. run evtest command on the device.  The output should be names and nodes
       of all detected input sources.
    b. run touch_UpdateErrors test on the device and read the logs.  All input
       devices should be listed in .INFO along with their nodes.
3. RECORD (from the device):
    evemu-record $node -1 > $filename
4. PLAY BACK (for verification, from the device):
    evemu-play --insert-slot0 $node < $filename

Other potentially useful commands:
- Record device properties for emulation:
    evemu-describe $node
- Emulate device:
    evemu-device < $filename


See also https://www.freedesktop.org/wiki/Evemu/