UI: XDCR Backfill

XDCR collections will introduce a new concept of backfill, which is hidden from the users, as well as the highest abstraction level of the UI.

Given that the highest-level of replication will not expose the level of detail to the user, then the next question is: "How do we represent statistics related to backfill activities" in the UI?

It is completely plausible that the "main" replication is caught up and nothing is happening on the source side. Then, a customer deletes and recreates a target collection that is being replicated, which triggers and backfill. There's work being done... (i.e. changes_left for the backfill pipeline is no longer 0). But should the work be tagged on to the overall stats? Should the overall stats remain constant but have an "Advanced detail" stats that show work being done by the backfill pipeline?

Since XDCR is exposing backfill pipeline stats (MB-41049) as a separate entity, the question is how to represent that information in the UI going forward that is not going to introduce too much complication to the user.

Unfortunately, "ignore all backfill stats" may not be a viable option, since the customer will see inconsistent system behavior from the UI. (i.e. "My network bandwidth is being used but yet in the UI I don't see anything on XDCR")