[TNU05] Add no upstream notification

Reminder user of unavailable tethering status if there is no
internet access.

Bug: 147818698
Test: atest TetheringTests
Change-Id: Ic6557f9f7703337596100cd6a477fd7239217166
diff --git a/Tethering/res/values/config.xml b/Tethering/res/values/config.xml
index 3a2084a..780a015 100644
--- a/Tethering/res/values/config.xml
+++ b/Tethering/res/values/config.xml
@@ -200,4 +200,10 @@
     <string name="tethering_notification_title">@string/tethered_notification_title</string>
     <!-- String for tether enable notification message. -->
     <string name="tethering_notification_message">@string/tethered_notification_message</string>
+
+    <!-- No upstream notification is shown when there is a downstream but no upstream that is able
+         to do the tethering. -->
+    <!-- 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>
 </resources>