[Groxx]

If I'm reading the article correctly (and it's a bit vague), these are part of the experimental extensions API. They're accessible only to arbitrary programs you've downloaded and run, and they inform you that they use api X.

To make matters harder, experimental API extensions aren't allowed in the chrome extension gallery - you'll have to go looking for unapproved, file-system-accessing extensions to expose yourself in the slightest to that danger.