infra to deliver callback args from driver to agent

Change-Id: Ide9d4542341144feb4c8cb37c1a4f6679d3dc2e2
diff --git a/proto/AndroidSystemControlMessage.proto b/proto/AndroidSystemControlMessage.proto
index d61e3d3..25c2772 100644
--- a/proto/AndroidSystemControlMessage.proto
+++ b/proto/AndroidSystemControlMessage.proto
@@ -16,6 +16,8 @@
 
 package android.vts;
 
+import "test/vts/proto/InterfaceSpecificationMessage.proto";
+
 
 // Type of a command.
 enum CommandType {
@@ -140,6 +142,9 @@
 message AndroidSystemCallbackRequestMessage {
   // callback id for the message sent to the TCP Server.
   optional bytes id = 1;
+
+  // args
+  repeated VariableSpecificationMessage arg = 11;
 }