Bug 991812: Remove uses of RefCounted<T> that live in Gecko. r=ehsan

--HG--
extra : rebase_source : 239ff77ec3765a3f190ed75b1645c6011e5d1dbd
Bug 991812: Remove uses of AtomicRefCounted<T> that live in Gecko. r=ehsan

--HG--
extra : rebase_source : 0d14e02c64d548fd3177681248d722683aaa87c3
Bug 995405: Don't pass around references to the observer service off the main thread. r=michal

--HG--
extra : rebase_source : 14baedc2f8e0d9f63b30be9c3c9eb373ba432ec5
Bug 993734: Stop pretending that the observer service is threadsafe. r=bsmedberg

--HG--
extra : rebase_source : 233d626d1127cc9c82adb6d486b1ad599bb060ce
Bug 994971: Don't export nsObserverService.h. r=bsmedberg

--HG--
extra : rebase_source : cd5aa136075086a10cfa03d937743d8a5471fd6c