Implemented onRestrictPowerChanged().

BUG: 28521946

Change-Id: I702e27401f74eee6ce884351ae4e0bc89ec6b8e2
(cherry picked from commit f79c20500e4e14992f8f470836bf61a6c9d4a1d3)
diff --git a/src/com/android/settings/datausage/DataSaverBackend.java b/src/com/android/settings/datausage/DataSaverBackend.java
index eb62ad7..0c8c2e2 100644
--- a/src/com/android/settings/datausage/DataSaverBackend.java
+++ b/src/com/android/settings/datausage/DataSaverBackend.java
@@ -207,6 +207,10 @@
         }
 
         @Override
+        public void onRestrictPowerChanged(boolean restrictPower) {
+        }
+
+        @Override
         public void onRestrictBackgroundChanged(final boolean isDataSaving) throws RemoteException {
             mHandler.post(new Runnable() {
                 @Override