Navi: Add metrics for NTP background module

Bug: 924176
Change-Id: I412c161d44754341db49774957ac1bde42d26397
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497294
Commit-Queue: John Lee <johntlee@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639721}
8 files changed