1touch_TouchscreenZoom uses two gesture files per device.
2
3With all zooms, do not make stray gestures.  Use only two fingers.  Once the
4zoom starts, do not stop movement or lift fingers until gesture is complete.
5
6<DEVICE_NAME>_touchscreen_zoom_in:
7    Press two fingers to the touchscreen such that they are close together, but
8    not touching.  Smoothly spread them apart.
9
10<DEVICE_NAME>_touchscreen_zoom_out:
11    Press two fingers to the touchscreen such that they are separated.  Smoothly
12    bring them together, but do not let them touch.
13