Two minor issues that I caught in the log while fixing Phame permissions:
- We had a JS bug which would cause us to immediately generate two comment previews at the exact same time -- one for loading the page, and one for "switching to desktop". Instead, only generate the "switch to desktop" preview if we really switched to desktop from a different device layout.
- These two requests could end up reading/writing the VersionedDraft table at exactly the same time fairly often (e.g., after a comment submission, the page would load, send two preview requests at exactly the same time, and they'd race fairly reliably for me locally). If we do race, recover from the race.