+ // A B
+ // (1) update_fee/commitment_signed ->
+ // <- (2) revoke_and_ack
+ // .- send (3) commitment_signed
+ // (4) update_fee/commitment_signed ->
+ // .- send (5) revoke_and_ack (no CS as we're awaiting a revoke)
+ // <- (3) commitment_signed delivered
+ // send (6) revoke_and_ack -.
+ // <- (5) deliver revoke_and_ack
+ // (6) deliver revoke_and_ack ->
+ // .- send (7) commitment_signed in response to (4)
+ // <- (7) deliver commitment_signed
+ // revoke_and_ack ->
+
+ // Create and deliver (1)...