Add data saver tile

Bug: 22817899
Change-Id: I900f19cca54daabd45fe358ae4117d4f3e9ab824
diff --git a/proto/src/metrics_constants.proto b/proto/src/metrics_constants.proto
index 88e55dd..697777c 100644
--- a/proto/src/metrics_constants.proto
+++ b/proto/src/metrics_constants.proto
@@ -339,5 +339,8 @@
 
     // Logged when the user calls an emergency contact.
     ACTION_CALL_EMERGENCY_CONTACT = 283;
+
+    // QS Tile for Data Saver.
+    QS_DATA_SAVER = 284;
   }
 }