[TNU06] Add roaming notification

Warn user of potential data charges if the backhaul is
cellular and user is roaming.

Bug: 145629001
Test: atest TetheringTests
Change-Id: I74b4f87c2f6aad09e05d3f2a779f880396885953
diff --git a/Tethering/res/values/config.xml b/Tethering/res/values/config.xml
index 780a015..aed5ab8 100644
--- a/Tethering/res/values/config.xml
+++ b/Tethering/res/values/config.xml
@@ -206,4 +206,9 @@
     <!-- Delay(millisecond) to show no upstream notification after there's no Backhaul. Set delay to
          "-1" for disable this feature. -->
     <integer name="delay_to_show_no_upstream_after_no_backhaul">-1</integer>
+
+    <!-- Cellular roaming notification is shown when upstream is cellular network and in roaming
+         state. -->
+    <!-- Config for showing upstream roaming notification. -->
+    <bool name="config_upstream_roaming_notification">false</bool>
 </resources>