They also use Chrome to collect data, according to my own testing. I have tested chrome, as well as chromium (the open source solution that G supposedly has not tampered with), and I have set up a firewall that limits outgoing connections. I found that, when both chromium and chrome was idle, it suddenly started requesting this:
"On [date], 2014, Chromium tried to establish a connection to ssl.google-analytics.com on port 443 (https). The request was denied via connection alert."
I am not sure why the browser itself would want to connect directly to google analytics when I was not using it, but based on other things that has come to light about googles monitoring and tracking of its users, I'm sure chrome collects a lot about use browsing habits and then sends it to google. I tested it on multiple computers, and the same thing happened, Chrome would all of a sudden connect to analytics while I wasn't browsing. Strange thing is, I have never seen anyone else write about this, although I successfully replicated this behaviour in Chrome multiple times (I just installed it, and it soon started calling back to GA, on any computer). Google is a shady business...