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/core/java/android/net/INetworkManagementEventObserver.aidl b/core/java/android/net/INetworkManagementEventObserver.aidl
index a97f203..6f4dd5f 100644
--- a/core/java/android/net/INetworkManagementEventObserver.aidl
+++ b/core/java/android/net/INetworkManagementEventObserver.aidl
@@ -62,4 +62,11 @@
      */
     void limitReached(String limitName, String iface);
 
+    /**
+     * Interface data activity status is changed.
+     *
+     * @param iface The interface.
+     * @param active  True if the interface is actively transmitting data, false if it is idle.
+     */
+    void interfaceClassDataActivityChanged(String label, boolean active);
 }