Renaming this bug as it really has nothing to do with GMail specifically. To clarify:
- Chrome Sync Server relies on a backend infrastructure component to enforce quotas on per-datatype sync traffic.
- That quota service experienced traffic problems today due to a faulty load balancing configuration change.
- That change was to a core piece of infrastructure that many services at Google depend on. This means other services may have been affected at the same time, leading to the confounding original title of this bug.
- Because of the quota service failure, Chrome Sync Servers reacted too conservatively by telling clients to throttle “all” data types, without accounting for the fact that not all client versions support all data types.
The crash is due to faulty logic responsible for handling “throttled” data types on the client when the data types are unrecognized.