Chrome Version       : 55.0.2873.0

I launched Chrome and failed the DCHECK in SiteEngagementService::CleanupEngagementScores() on line 318.  My last_engagement_time() was 8 hours later than my rebase_time.

This may have been because I had just launched a Chrome 52 build with the same local profile.  Perhaps Chrome 52 writes some data to the profile and not other data, and the newer versions expect both pieces of data to be in sync.

If so, we should probably try to handle this more gracefully (detect and silently fix or do nothing).  While running Chrome with outdated profile data is not guaranteed to "bring everything up to date nicely", it shouldn't actually trigger assertions in our code.

Don't know who should own this (or what the component is); assigning to the first OWNER in c/b/engagement/ for triage.