The other large binary blob in the non-opensource builds, apart from DRM, is the wifi network detection module.

It will look at what wifi networks are close to you, and Google finds out your physical location that way without your computer having a GPS chip or a cellphone network chip (Google has the full database of the center of gravity for every wifi network from the streetview cars, so the information of which network is how strong for your computer allows location by something like +- 10 meters).