I'm not sure about the internals of Chromium because i never use it and I'm not involved in the development of it, but from what i remember using beforeload is a hack that has a % chance of actually working per page load.

Proper resource blocking support is in development last time i checked, but it isn't done yet, which is why Ghostery, Disconnect, HTTPS Everywhere, etc aren't available/don't work on chrome.

Of course, Ghostery will still give you a list of trackers, but it won't always succeed in blocking all of them.