GitLab

Pre-work for this has been done in:
https://chromium-review.googlesource.com/c/chromium/src/+/2443089

This moves BackgroundSyncMetrics to components and updates references.

Bug: 1087486
Change-Id: I175de6d5ff224ba2e9f590234b98bd4a2de952e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2445874
Commit-Queue: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814598}