[asquabventured]

On chrome you can actually create your own signing key, and then self sign the unpacked extension directory using your key. To remove the pop-up you then need to set up a group policy (on Windows) to trust your self signed extensions. End result is this popup doesn't come up at launch.

I think this is so hidden (and not really documented well) as a "fix" that must have been added for companies that use their own internal extensions that don't publish them on the web store.

If you can't figure it out from that description I can try to publish a step-by-step on how to accomplish this