[net/http auth] Use strings to identify authentication schemes.

net/log/net_log_event_type_list.h

Index: net/log/net_log_event_type_list.h
diff --git a/net/log/net_log_event_type_list.h b/net/log/net_log_event_type_list.h
index 0e5128972246e2e19506541e528e00984bcebed4..128d3cb068a33503328129dbb33bea8cb5eca77d 100644
--- a/net/log/net_log_event_type_list.h
+++ b/net/log/net_log_event_type_list.h
@@ -1796,6 +1796,13 @@ EVENT_TYPE(AUTH_PROXY)
 // The time spent authentication to the server.
 EVENT_TYPE(AUTH_SERVER)
 
+// Unexepcted failure while trying to create an HttpAuthhandler.
+//   {
+//     "challenge": <Authentication challenge that caused the failure>,
+//     "net_error": <net::Error>
+//   }
+EVENT_TYPE(AUTH_HANDLER_CREATION_FAILURE)
+
 // ------------------------------------------------------------------------
 // HTML5 Application Cache
 // ------------------------------------------------------------------------