Dispatch events for back press

Test: manual - expand bubble, hit back, repeat
Test: atest WindowOrganizerTests
Fixes: 182173547
Change-Id: Icf7ea333fa4429fbb8f9c99279b0188052351289

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

@@ -865,6 +865,7 @@ class TaskOrganizerController extends ITaskOrganizerController.Stub {
             mPendingTaskEvents.remove(pending);
         }
         mPendingTaskEvents.add(pending);
+        mService.mWindowManager.mWindowPlacerLocked.requestTraversal();
         return true;
     }