After hitting the issue where I accidentally opened my profile in beta recently and upgraded my storage schemas, I think we should try to warn about this issue a bit more. Bug 1246615 is to provide a banner or other warning. There are some things we should do at the platform level first: 1) Lets notify a "profile-storage-corrupted" observer topic when we detect this kind of thing. 2) Lets log a message to the browser console with more detail about the corruption. (Schema number, unexpected file, etc.) Bug 1246615 can then use the observer topic to know when to show its warning banner.

The main hassle here is often we detect this storage corruption on IO threads, but observer service and console reporting needs to take place on the main thread. I think we should add a helper to nsContentUtils or something to make it easy to trigger things.