Fix broken build for more tests

Change-Id: I7bdd12a833233724805d01d993541ee05caa9bf6
diff --git a/libs/gui/tests/DisconnectWaiter.h b/libs/gui/tests/DisconnectWaiter.h
index 3a30a19..56e96c2 100644
--- a/libs/gui/tests/DisconnectWaiter.h
+++ b/libs/gui/tests/DisconnectWaiter.h
@@ -57,6 +57,8 @@
         }
     }
 
+    virtual void onSidebandStreamChanged() {}
+
     void finishDisconnect() {
         Mutex::Autolock lock(mMutex);
         mWaitForDisconnect = true;