UMK metrics for offline pages were disabled for privacy reasons.  The original contract was that UKM would be collected only for pages that the user visits.  Offline pages that the user requests to download are not actually visited in the traditional sense, and the user may never in fact look at them.  However, the user did *request* them, so there is an argument to be made that from a privacy standpoint, UKM for offline pages should be a reasonable thing to collect.

We should either have a discussion with the privacy team about whether it makes sense to re-enable UKM for offline pages, or remove the code that collected it.