wm: Passing a new ArraySet instance to avoid crash

The two threads "LazyTaskWriterThread" and "TaskSnapshotPersister"
are using the same persistentTaskIds param, which can lead to crash as follows

E AndroidRuntime: *** FATAL EXCEPTION IN SYSTEM PROCESS: TaskSnapshotPersister
E AndroidRuntime: java.lang.ArrayIndexOutOfBoundsException: length=0; index=14
E AndroidRuntime: 	at android.util.ContainerHelpers.binarySearch(ContainerHelpers.java:28)
E AndroidRuntime: 	at android.util.ArraySet.indexOf(ArraySet.java:86)
E AndroidRuntime: 	at android.util.ArraySet.indexOf(ArraySet.java:341)
E AndroidRuntime: 	at android.util.ArraySet.contains(ArraySet.java:330)
E AndroidRuntime: 	at com.android.server.wm.TaskSnapshotPersister$RemoveObsoleteFilesQueueItem.write(TaskSnapshotPersister.java:388)
E AndroidRuntime: 	at com.android.server.wm.TaskSnapshotPersister$1.run(TaskSnapshotPersister.java:226)

To fix this, passing a new ArraySet instance instead.

Change-Id: Id9503ae93ea929e7a289bd0a9f461f0639983ea6

Author: Qiushi.Han

services/core/java/com/android/server/wm/TaskSnapshotPersister.java

@@ -162,7 +162,9 @@ void onTaskRemovedFromRecents(int taskId, int userId) {
     void removeObsoleteFiles(ArraySet<Integer> persistentTaskIds, int[] runningUserIds) {
         synchronized (mLock) {
             mPersistedTaskIdsSinceLastRemoveObsolete.clear();
-            sendToQueueLocked(new RemoveObsoleteFilesQueueItem(persistentTaskIds, runningUserIds));
+            // Copy persistentTaskIds to avoid two threads manipulating it at the same time.
+            sendToQueueLocked(new RemoveObsoleteFilesQueueItem(
+                    new ArraySet<>(persistentTaskIds), runningUserIds));
         }
     }