Cache tab explodes causing the devtools to crash

[jerelmiller]

It seems there might be an issue with some cache values causing the cache tab to explode, which crashes the devtools panel. This comes from email feedback from one of our users.

I'll see if we can get a reproduction or figure out what kind of cache values are present in the cache here. At the very least, we should be able to handle unserialable cache values in the devtools, even if this means showing an error to the user in doing so.