The limited checking I did on my machine points to this, at least that's what the URLs in the code appeared to be for. Didn't really look at the code, just searched for the URLs.
What do you mean by synchronization?
Sync of tabs/bookmarks etc.
Chromium & chrome sync all of your bookmarks, settings, etc across browsers. If I fav something in my mobile, it shows up in my desktop.
That should only happen when logged in, and given the context here, I assume the user was not logged in (since when you're logged in, all privacy is definitely completely lost).