Bug 975419 - Used a TenuredHeap pointer for SandboxPrivate and BackstagePass. r=mccr8
Bug 975419 - Add a JS::TenuredHeap<JSObject*> overload to TraceCallbacks. r=mccr8,terrence
Bug 975419 - Trace the Incumbent Global from a CallbackObject (but check it too, just to be safe). r=bz,mccr8