This might be as simple as switching their registration to be syncable right here https://cs.chromium.org/chromium/src/components/flags_ui/pref_service_flags_storage.cc?l=53

I don't know what mechanism flags use to notify whatever depends on them to check them, or if you usually need to restart your browser after setting them. This could create a slightly awkward experience where you have to sync Chrome to have the new flags, and then restart before they take effect. More digging is needed to be sure.

Also it looks like some weird stuff is going on for ChromeOS for flags. Definitely will want to test to make sure everything is working on that front.

Also, I'm not quite sure how flags is gated based on platform. It looks like some experiments are unavailable based on platform. Hopefully is not just for setting/modifying them on given platforms, but also for reading them. We wouldn't want to let sync set flags to invalid states.

This type of work however is typically not done by the Sync team. The infrastructure is all here, and shouldn't require any changes. It's the owners of the flags logic that would ultimately need to decide this is a good idea and would be best situatuated for testing edge cases.

These flags are all experimental, and should never be relied on. They can break things or disappear at any time. As such, they're not good candidates for syncing across devices.

Great summary and reasoning. Thank you.