[Bugfix] Fix array out of bounds.

Problem:
JE caused by multi-threaded operation of WindowList.

Solution:
Lock to prevent array out of bounds.

Bug: 288065262
Test: Manual && Monkey Test
Change-Id: Idd58f5c74444e93758f89133779f2076f95f1725

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

@@ -549,8 +549,8 @@ public class TaskPersister implements PersisterQueue.Listener {
             // Write out one task.
             byte[] data = null;
             Task task = mTask;
-            if (DEBUG) Slog.d(TAG, "Writing task=" + task);
             synchronized (mService.mGlobalLock) {
+                if (DEBUG) Slog.d(TAG, "Writing task=" + task);
                 if (task.inRecents) {
                     // Still there.
                     try {