Allow the host to enable/disable double tap.
Send event when double tap is present.
Also fix a bug when scanning for gestures.
BRANCH=smaug
BUG=chrome-os-partner:44754
TEST=compile. Check on Ryu.
Change-Id: I50d008cd3823072ab1c1e2d21f1276cd2185d797
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/298683