Chelsea and Arsenal have been charged with various things:
http://www.bbc.co.uk/sport/0/football/34319410
Violent conduct for Costa, improper conduct for Gabriel and failing to control their players for both clubs.
Seems about right, to me.
No idea how Arsenal expect to be successful with their appeal for the Gabriel red. He could've had two.
Took a swing at Costa, which the ref missed as badly as he did, then kicked out at him and got sent off.
Costa could've had about four, admittedly, but that seems like a very hopeful move.