Chromium is open source - which makes me suspicious of claims that the browser is nefariously tracking your every move without pointing to code.

Here's a search for the 'client_id' that the author was afraid of: http://codesearch.google.com/codesearch?as_q=client_id&v...

It looks like a likely possibility is that the author is syncing his profile to google - in which case it makes sense that some ID needs to be stored in order to figure out which sync updates are coming from which browser.