Run ui_touch_selection_unittests on mac and cast bots.

Mac doesn't have touch UI, and the test doesn't really make too much
sense on cast, but the code under test is built there and the test
is small and fast, so might as well run it. Maybe one day the test
should move to chromium_gtests_for_devices_with_graphical_output instead.

Bug: 843511
Change-Id: I1792ee0d57a9f039dba71bb6b28d33e272ab5236
Reviewed-on: https://chromium-review.googlesource.com/1129580
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573484}
6 files changed