It's off by default, it's only ever enabled by testing code, and why carry complexity that no one ever uses. Madness... This also appears to let us rip out DeepCloneObjectLiteral as well. All total, this looks like over a hundred lines of code to die here, I think.

Sigh. Bug 1061534 comment c5 says this is being carried indefinitely until someone does startup cache hacking of some sort to put this to actual use. My skepticism that it'll work right in that theoretical day when it actually happens is about nil. In the meantime it's obviously confusing, and dead code fodder that begs to be removed. :-(

FYI, nil is going to be non-null soonish, Sean is taking over the startup-cache for shumway.