Pretty print AlternativeService in test macros.

net/http/http_server_properties.cc

Index: net/http/http_server_properties.cc
diff --git a/net/http/http_server_properties.cc b/net/http/http_server_properties.cc
index 82ce06e7e57a8a74ac93c63d2fc44fe0de2d93a7..e614b3864f28d594246f6475099ccb8a856abdac 100644
--- a/net/http/http_server_properties.cc
+++ b/net/http/http_server_properties.cc
@@ -4,6 +4,8 @@
 
 #include "net/http/http_server_properties.h"
 
+#include <iostream>
+
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/stringprintf.h"
@@ -110,6 +112,11 @@ std::string AlternativeServiceInfo::ToString() const {
                             probability);
 }
 
+std::ostream& operator<<(std::ostream& os,
+                         const AlternativeService& alternative_service) {
+  return (os << alternative_service.ToString());
+}
+
 // static
 void HttpServerProperties::ForceHTTP11(SSLConfig* ssl_config) {
   ssl_config->next_protos.clear();