NotificationHistoryDatabase: Mark unaudited PendingIntents with FLAG_MUTABLE_UNAUDITED

These PIs need an explicit mutability flag. This temporay flag is being
used to mark these points in code and should be replaced ASAP.
See go/immutable-pendingintents for more context.

Bug: 160794467
Test: TH
Exempt-From-Owner-Approval: noop change
Change-Id: Ia72faa769751b1262d57608f5722c3e50249c0bf

services/core/java/com/android/server/notification/NotificationHistoryDatabase.java

@@ -293,7 +293,9 @@ public class NotificationHistoryDatabase {
                                 .appendPath(file.getAbsolutePath()).build())
                         .addFlags(Intent.FLAG_RECEIVER_FOREGROUND)
                         .putExtra(EXTRA_KEY, file.getAbsolutePath()),
-                PendingIntent.FLAG_UPDATE_CURRENT);
+                // TODO(b/174161800) Please replace FLAG_MUTABLE_UNAUDITED below
+                // with either FLAG_IMMUTABLE (recommended) or FLAG_MUTABLE.
+                PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_MUTABLE_UNAUDITED);
         mAlarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, deletionTime, pi);
     }