sync this

There are two kinds of people in the world: (i) the kind who would want all their logins, passwords, cookies, and browsing history to be transmitted to Google's servers for reasons of "convenience" and (ii) everyone else.
If you fall into (ii) you probably don't care much about the recent flap where Google users are involuntarily "logged in" to their Chrome browsers. (Who knew you could even "log in" to a browser?) This occurs whenever users log into a Google "product" such as gmail. The reason for all this logging in is ostensibly so the users' data can be "synchronized" among the Google servers and all instances of Chrome they might be running.
If you fall into category (i) you are either very concerned about this privacy-shredding dark pattern or, you feel it's simply a matter of Google needing to have better documentation.