Lightweight checkin output for network stats.

Define and print a compact version of network statistics when dump
is requested with the "--checkin" flag.  Defaults to last 24 hours,
but included data can be tweaked with various flags.

Groups together detailed network identities into larger umbrella
terms like "mobile" and "wifi."

Bug: 18415963
Change-Id: I70cf9c828ea5c6e5bb6884837d3608f66fbad2e6
diff --git a/core/java/android/net/NetworkStats.java b/core/java/android/net/NetworkStats.java
index ea5dfd1..2afe578 100644
--- a/core/java/android/net/NetworkStats.java
+++ b/core/java/android/net/NetworkStats.java
@@ -733,6 +733,22 @@
     }
 
     /**
+     * Return text description of {@link #set} value.
+     */
+    public static String setToCheckinString(int set) {
+        switch (set) {
+            case SET_ALL:
+                return "all";
+            case SET_DEFAULT:
+                return "def";
+            case SET_FOREGROUND:
+                return "fg";
+            default:
+                return "unk";
+        }
+    }
+
+    /**
      * Return text description of {@link #tag} value.
      */
     public static String tagToString(int tag) {