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This CL instantiates UserActionRecorderImpl and hooks it up to various
user actions, causing user engagement and retention metrics to be
emitted.

Bug: 1150634, 1106937
Change-Id: I64498e7585d2be4c0536dc33cd5486781376c961
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2576404
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835919}