The first suggested metric would track the cases where all of these are true:
- The user is returning to an existing tab.
- The reloading of the page contents is necessary.
- An offline snapshot is available.

The specific values to be tracked still need to be defined. We could create counters to help us compare the cases where all of these where true versus the ones where the offline copy was *not* available, which would provide some idea of its efficacy.

Another option would be to track the time the reloading took. Longer reload times could justify the time and resources spent to first load the snapshot while shorter times would make the extra complexity of the feature unjustified.

Fixit update: good one but needs defining all new metrics to be added beyond the ones suggested in #1. Me and dimich@ are needed, potentially bengr@ too, and others are also welcome to chime in.

Note we have also done this work to assess the potential benefit: https://bugs.chromium.org/p/chromium/issues/detail?id=686887

The new histogram being added in  issue 688588  to track last_n tab restores will provide a partial representation of the suggestion in #1 and might already be an initial source of data to show the potential benefit of this feature.

As referenced in previous comments we are already tracking:
*  Issue 688588 : the potential cases where restoring a tab from an offline snapshot would be possible in online situations (1st and 2nd points in suggested histogram in #1).
*  Issue 686887 : the potential amount of data that would be saved should we allow loading offline snapshots while online.

So I'm closing this issue for now. Reopen if you have ideas of other metrics we should have to generate supporting data for this feature.