GitLab

For mash/mushrome we need setting of touch state to happen in
mus. This patch separates out setting into a separate class so that
ash in mus/mash can plug in a class that makes mojo calls.

BUG=705686
TEST=covered by tests
R=oshima@chromium.org

Review-Url: https://codereview.chromium.org/2887413004
Cr-Commit-Position: refs/heads/master@{#473474}