Bug 847634 - Add lines missing from uplift. r=mfinkle a=lsblakk
Bug 844671 - Only sync remote tabs to non-private windows. r=gavin a=lsblakk
Bug 843214: Make SourceMediaStream::AddTrack/AppendToTrack/HaveEnoughBuffered/DispatchWhenNotEnoughBuffered/EndTrack smoothly handle cases where track does not exist. r=jesup a=lsblakk