test_gallery_full_screen_image_flicks

To understand the flick event take a look over
https://hg.mozilla.org/integration/mozilla-inbound/file/9a8d04f67e39/testing/marionette/client/marionette/touch/synthetic_gestures.js#l25

 https://hg.mozilla.org/integration/mozilla-inbound/file/9a8d04f67e39/testing/marionette/client/marionette/touch/synthetic_gestures.js#l46