Bug 840898.  Flag our nullable return value as actually being nullable.  r=tbsaunde
Bug 835267.  Make sure to save our suggested filename before we append a .part to it so that we don't suggest filenames with .part in them.  r=gavin.

Another option would be to save it before we createUnique too, and just assume that this name is only used if the user really wants it so it's OK to overwrite files with it.
Bug 822674.  Give RTCPeerConnection a sane classinfo.  r=jst,jesup.  r=peterv pending