Adding some debug controls to test multi-window.

Adding some preliminary controls to mirror the currently exposed api
to create new activity stacks, resize stacks, and to move tasks
between stacks.

Change-Id: I3fb51c248f53a1d4c4eb23ca9fb3a76888def1de
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index b7728b3..03f1f71 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -3729,6 +3729,13 @@
         }
 
         @Override
+        public int getStackId() {
+            synchronized (mService) {
+                return mStackId;
+            }
+        }
+
+        @Override
         public boolean injectEvent(InputEvent event) {
             final long origId = Binder.clearCallingIdentity();
             try {