Add a getter for the active tag

Change-Id: I597e041867fba7efae41feea63fa196bc10e4aa2

core/java/android/net/TrafficStats.java

@@ -96,6 +96,15 @@ public class TrafficStats {
         NetworkManagementSocketTagger.setThreadSocketStatsTag(tag);
     }
 
+    /**
+     * Get the active tag used when accounting {@link Socket} traffic originating
+     * from the current thread. Only one active tag per thread is supported.
+     * {@link #tagSocket(Socket)}.
+     */
+    public static int getThreadStatsTag() {
+        return NetworkManagementSocketTagger.getThreadSocketStatsTag();
+    }
+
     /**
      * @deprecated unsupported, will eventually be removed
      */