Takes the first sink in the chain of sinks composed so far, and then chains its message sink in front of the chain already formed.
The composite sink chain.
The IContributeEnvoySink.GetEnvoySink(MarshalByRefObject, System.Runtime.Remoting.Messaging.IMessageSink) method is used as an optimization to create an envoy sink when the destination is a different context in the same application domain and is used by the Wrap operation.