4/n Add fallback to default task display area

... for the cases when a particular task display area target is not
specified, and/or the logic applies only to the default/fallback
task area on the display.

Bug: 152116619
Test: WM CTS and unit tests
Change-Id: I209629baada05b0615ea2874f39a2b30a95b7565
diff --git a/services/core/java/com/android/server/wm/TaskOrganizerController.java b/services/core/java/com/android/server/wm/TaskOrganizerController.java
index b641e4c..9ffd8d2 100644
--- a/services/core/java/com/android/server/wm/TaskOrganizerController.java
+++ b/services/core/java/com/android/server/wm/TaskOrganizerController.java
@@ -277,7 +277,7 @@
                     return null;
                 }
 
-                final Task task = display.mTaskContainers.createStack(windowingMode,
+                final Task task = display.getDefaultTaskDisplayArea().createStack(windowingMode,
                         ACTIVITY_TYPE_UNDEFINED, false /* onTop */, null /* info */, new Intent(),
                         true /* createdByOrganizer */);
                 RunningTaskInfo out = task.getTaskInfo();