Fix units for Arc.EngagementTime.* metrics

Units should be milliseconds instead of seconds.

Bug: 904282
Change-Id: I406a6d0f5808b2dc2662c77e7d4b9783e3a07e7e
Reviewed-on: https://chromium-review.googlesource.com/c/1355305
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Shao-Chuan Lee <shaochuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612925}
1 file changed