Introduce connector, to help subchannel connect
diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index e268949..588c63c 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -37,6 +37,7 @@
 
 struct grpc_subchannel {
   gpr_refcount refs;
+  grpc_connector *connector;
 };
 
 struct grpc_subchannel_call {