async fn send_frame<S>(
socket: &mut ClientSocket<S>,
message: ServerMessage,
) -> Result<usize>where
S: Sink<Message, Error = Error> + Unpin,Expand description
send, answering how many bytes the frame carried.
Only the open path reports a size (#2374), and a return every other caller would drop is noise in thirty of them - so the size is answered here and the plain write wraps it.