GitLab

Adds an Engagement Suppression heuristic that sends several new signals
to the ML model for Tap Suppression.  These signals quantify user
engagment by registering the number of lifetime opens, quick actions
taken, translations shown, etc.

Note that the additional signals in this CL are documented in
http://go/ukm-cs-4 (with privacy approval noted there).

BUG=776156

Change-Id: I1e9457a18a5624ceb97e7236761f99173af6dabe
Reviewed-on: https://chromium-review.googlesource.com/1079810Reviewed-by: Roger McFarlane <rogerm@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571210}