"Due its complexity, Chromium uses a set of custom tools to check out and build. Here’s an overview of the steps you’ll run:

    gclient. A checkout involves pulling nearly 100 different SVN repositories of code. This process is managed with a tool called gclient.

. . . "

// everytime i upgrade a browser? cmon..

I actually build chromium from source for this exact reason, I've gotten it to stop phoning home. It phones home for the following:

1. If you are using the Google APIs (see this picture http://i.imgur.com/UodLpFh.png) for the browser to have more functionality.

2. If you have the "Google account Badge" thingy in the upper right enabled.

I don't know exactly what in those two causes the phone home, I assume (educated guess here) that it's verifying your api keys for browser features such as spell check, that or getting the "Badge" thing setup. While you may be opening a new tab labeled blank that "badge" thing is a pure js/html page thats loaded in the background that does need to phone home.