I think we should try again to spawn the extension host only after the workbench is running. I remember @jrieken tried this but then we had clients that would prevent the restoring of editors from happening (via preferences editor).

We should replace IExtensionService.onReady() with a LifecyclePhase that is always fired after LifecyclePhase.Running imho and then we have a consistent picture of phases.

That means revisiting each user of IExtensionService.onReady() and making sure it is not blocking the startup. One challenge is that it is hard to prevent deadlocks from happening because we will always add new code that might cause it.

Thoughts?