Extension doesn't load in embedded dashboard

[dustinglass]

I have gotten the extension to work great on Tableau Desktop and Cloud, but when embedded in my web app the extension doesn't load. The rest of the dashboard components load, but the extension doesn't load and shows a light gray placeholder box, and then finally a Sign in to Tableau Online button appears. (Obviously not suitable for white-labeling.) I suspect this is because some authentication method used by the extension (or lack thereof) doesn't work in an externally embedded context.

See this screen capture for clarity: https://drive.google.com/file/d/1Y1MezeYXaMw1dPtB1h507E4vL0lHpgUe/view?usp=sharing

It's a great extension, but I'd love to see it work in an embedded use case.