(In reply to Olli Pettay [:smaug][email@example.com] from comment #6)
Dennis, do you happen to have recommendation how large buffer we should allow?
Last time I checked blink had some seemingly random limit around 500MB, but I don't know what Webkit does.
WebKit has a 64MB limit, which feels a lot more reasonable than Google's high limit.
That being said, our outreach in the known case of breakage was successful and they did adjust their implementation, so we don't have any active WebCompat breakage here.
If we see this again, we might have to look at some telemetry data (or rather, add some) to get a feeling about the usual sizes people try to store, and maybe figure out what their use-case is. I get the feeling that people storing large information in the history do this as a hacky workaround, but maybe I'm missing something. It's hard to make any good estimation without having a large number of cases to look at, though :/