GitLab

Changes:
- Previously we were only exposing whether the event succeeded or
failed. Now we also include whether it timed out, was rejected,
or aborted.
- Add an event for when a sync is re-registered.
- Restore UMA logging and add a test for it.

Bug: 940450
Change-Id: I2f920b0b5adcf4374e9cfb4f3edd57658cd83021
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1549085
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Auto-Submit: Rayan Kanso <rayankans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#648655}