Apply FLAG_IMMUTABLE to the PendingIntent in NetworkStatService.java

Broadcast intents sent by AlarmManager are immutable; the system
dispatches them without customization.

Fixes: 171815343
Test: TH
Change-Id: I35ccfc0f69fd98b5803da74d9eb12902b351acc7
Merged-In: I35ccfc0f69fd98b5803da74d9eb12902b351acc7
diff --git a/services/core/java/com/android/server/net/NetworkStatsService.java b/services/core/java/com/android/server/net/NetworkStatsService.java
index 71e7c8a..12c24d4 100644
--- a/services/core/java/com/android/server/net/NetworkStatsService.java
+++ b/services/core/java/com/android/server/net/NetworkStatsService.java
@@ -552,7 +552,8 @@
 
         //  schedule periodic pall alarm based on {@link NetworkStatsSettings#getPollInterval()}.
         final PendingIntent pollIntent =
-                PendingIntent.getBroadcast(mContext, 0, new Intent(ACTION_NETWORK_STATS_POLL), 0);
+                PendingIntent.getBroadcast(mContext, 0, new Intent(ACTION_NETWORK_STATS_POLL),
+                        PendingIntent.FLAG_IMMUTABLE);
 
         final long currentRealtime = SystemClock.elapsedRealtime();
         mAlarmManager.setInexactRepeating(AlarmManager.ELAPSED_REALTIME, currentRealtime,