Chromium implements un-spec'd behavior that times out long-running transactions so that other clients don't get permanently stuck on a misbehaving page. This timeout is started when a request is completed and cancelled when the request's state transitions to done. (Technically this isn't a constraint on the duration of the transaction, but the dispatch of a request result.)

It would be ideal to specify this behavior.

Relatedly, if it's possible to disable auto-commit (#34 ) then we may want to create an additional un-stick mechanism for code that fails to call commit().