Where is it?
Looks like c9 has changed. The Docs now say i.imgur.com/ThyaLmo.png offering c9.io/new/google (also available from the Dashboard i.imgur.com/S8GC0AT.png and thanks H too for the link), where “Create a new workspace” i.imgur.com/nhLaf7J.png says i.imgur.com/Zc9OdeJ.png and once I have connected my Google account I see i.imgur.com/aHDjWWk.png including Select a project. I’ve not tested this, but it looks like problem solved.
(On those links restore the http:// or https:// that this post form made me remove.)
Note: On returning to c9.io/new/google , the page takes a few seconds to change to show the Google connection.