Butler stream servers can generate client address.

logdog/client/butler/streamserver/base.go

Index: logdog/client/butler/streamserver/base.go
diff --git a/logdog/client/butler/streamserver/base.go b/logdog/client/butler/streamserver/base.go
index 1e30635fdc16b32744c6fc7814df3de7657689f7..908b9a2c59a6ff185b9725a146fe7e007f4006a4 100644
--- a/logdog/client/butler/streamserver/base.go
+++ b/logdog/client/butler/streamserver/base.go
@@ -32,6 +32,9 @@ type streamParams struct {
 type listenerStreamServer struct {
 	context.Context
 
+	// address is the string returned by the Address method.
+	address string
+
 	// gen is a generator function that is called to produce the stream server's
 	// Listener. On success, it returns the instantiated Listener, which will be
 	// closed when the stream server is closed.
@@ -58,6 +61,8 @@ func (s *listenerStreamServer) String() string {
 	return fmt.Sprintf("%T(%s)", s, s.laddr)
 }
 
+func (s *listenerStreamServer) Address() string { return s.address }
+
 func (s *listenerStreamServer) Listen() error {
 	// Create a listener (OS-specific).
 	var err error