Add a binder RPC to enable/disable data saver.

Bug: 26685616
Bug: 27506285
Change-Id: Id11ee717cfc1c79070b6bbec397986c25947646c
diff --git a/server/BandwidthController.h b/server/BandwidthController.h
index f62cb1b..9d59a6c 100644
--- a/server/BandwidthController.h
+++ b/server/BandwidthController.h
@@ -21,9 +21,12 @@
 #include <utility>  // for pair
 
 #include <sysutils/SocketClient.h>
+#include <utils/RWLock.h>
 
 class BandwidthController {
 public:
+    android::RWLock lock;
+
     class TetherStats {
     public:
         TetherStats(void)