Add buffer_size

test/beast/http/span_body.cpp

@@ -10,6 +10,7 @@
 // Test that header file is self-contained.
 #include <boost/beast/http/span_body.hpp>
 
+#include <boost/beast/core/buffer_size.hpp>
 #include <boost/beast/http/message.hpp>
 #include <boost/beast/_experimental/unit_test/suite.hpp>
 
@@ -23,7 +24,6 @@ struct span_body_test
     void
     testSpanBody()
     {
-        using net::buffer_size;
         {
             using B = span_body<char const>;
             request<B> req;