Closely review all uses of IsCallerChrome() for e10s

A lot of our fingerprinting patches depend upon the accuracy is nsContentUtils::IsCallerChrome() to determine if it is content window or browser chrome accessing fingerprinting information.

IsCallerChrome() kind of scares me, and has had issues for unexpected contexts like WebWorkers (See #13027 (moved)).

We should keep a close eye on this as we transition to e10s support post FF38, as who knows that the child/parent context relationship changes may do to various codepaths.