Don't reorder windows on non-default display.

At least not until we add tasks to those displays.

Fixes bug 10264736.

Change-Id: I3baed4bf324c4a11bbf5b07755218c2992f5af39
diff --git a/services/java/com/android/server/wm/WindowManagerService.java b/services/java/com/android/server/wm/WindowManagerService.java
index 3db807f..950d482 100644
--- a/services/java/com/android/server/wm/WindowManagerService.java
+++ b/services/java/com/android/server/wm/WindowManagerService.java
@@ -7923,11 +7923,8 @@
     }
 
     final void rebuildAppWindowListLocked() {
-        final int numDisplays = mDisplayContents.size();
-        for (int displayNdx = 0; displayNdx < numDisplays; ++displayNdx) {
-            final DisplayContent displayContent = mDisplayContents.valueAt(displayNdx);
-            rebuildAppWindowListLocked(displayContent);
-        }
+        // TODO: Multidisplay, when ActivityStacks and tasks exist on more than one display.
+        rebuildAppWindowListLocked(getDefaultDisplayContentLocked());
     }
 
     private void rebuildAppWindowListLocked(final DisplayContent displayContent) {