Comment by 90-00-09

Sounds good. One problem that you will likely encounter in FF is that you can't open the native extension popup (the one that is attached to the action button) programmatically. That severely limits how you can present your UI, with the most obvious choice being injecting an iframe with the extension UI directly into the body of the page. The other choice is opening a new popup window, which is less convenient than seeing things side by side.