Network data activity change intent for network interfaces.

The activity notification is received from netd, an intent
DATA_ACTIVITY_CHANGE is then raised for other part of the system to
consume.

Change-Id: Idfcc4763c51c5b314c57f546c12557082f06bebf
diff --git a/services/java/com/android/server/connectivity/Vpn.java b/services/java/com/android/server/connectivity/Vpn.java
index 4b82037..b12d597 100644
--- a/services/java/com/android/server/connectivity/Vpn.java
+++ b/services/java/com/android/server/connectivity/Vpn.java
@@ -291,6 +291,9 @@
     public void limitReached(String limit, String interfaze) {
     }
 
+    public void interfaceClassDataActivityChanged(String label, boolean active) {
+    }
+
     private void enforceControlPermission() {
         // System user is allowed to control VPN.
         if (Binder.getCallingUid() == Process.SYSTEM_UID) {