Do not expose scheduling task from background thread

Author: aurimasc

com.unity.mobile.notifications/Runtime/Android/Plugins/com/unity/androidnotifications/UnityNotificationBackgroundThread.java

@@ -10,7 +10,7 @@
 import java.util.Set;
 
 public class UnityNotificationBackgroundThread extends Thread {
-    public static class ScheduleNotificationTask implements Runnable {
+    private static class ScheduleNotificationTask implements Runnable {
         private Notification.Builder notificationBuilder;
 
         public ScheduleNotificationTask(Notification.Builder builder) {
@@ -33,8 +33,8 @@ public UnityNotificationBackgroundThread() {
         enqueueHousekeeping();
     }
 
-    public void enqueueNotification(ScheduleNotificationTask task) {
-        mTasks.add(task);
+    public void enqueueNotification(Notification.Builder notificationBuilder) {
+        mTasks.add(new UnityNotificationBackgroundThread.ScheduleNotificationTask(notificationBuilder));
     }
 
     public void enqueueCancelNotification(int id) {

com.unity.mobile.notifications/Runtime/Android/Plugins/com/unity/androidnotifications/UnityNotificationManager.java

@@ -260,7 +260,7 @@ public Object[] getNotificationChannels() {
     public void scheduleNotification(Notification.Builder notificationBuilder) {
         int id = notificationBuilder.getExtras().getInt(KEY_ID, -1);
         putScheduledNotification(id);
-        mBackgroundThread.enqueueNotification(new UnityNotificationBackgroundThread.ScheduleNotificationTask(notificationBuilder));
+        mBackgroundThread.enqueueNotification(notificationBuilder);
     }
 
     protected void performNotificationScheduling(Notification.Builder notificationBuilder) {