This Chrome extension is developed primary for http://tokbox.com/. It doesn't do anything except capture content of your screen.
This Chrome extension was developed by Tokbox to enable screen sharing for official OpenTok integrations. It will only work with applications hosted at https://tokbox.com. If you have built a custom OpenTok application and would like to allow screen sharing, you will need to create and submit your own custom extension - see https://tokbox.com/developer/guides/screen-sharing/js/ .