Move updating stack override config to ActivityStack

Also added some multi-display TODOs.

Change-Id: Iada3f84c4f57c9623fc7f116819d4e0267ebc32a
diff --git a/services/core/java/com/android/server/wm/AppWindowToken.java b/services/core/java/com/android/server/wm/AppWindowToken.java
index 2828b96..f9aa66b 100644
--- a/services/core/java/com/android/server/wm/AppWindowToken.java
+++ b/services/core/java/com/android/server/wm/AppWindowToken.java
@@ -325,6 +325,8 @@
                 // The token is not closing nor opening, so even if there is an animation set, that
                 // doesn't mean that it goes through the normal app transition cycle so we have
                 // to inform the docked controller about visibility change.
+                // TODO(multi-display): notify docked divider on all displays where visibility was
+                // affected.
                 mService.getDefaultDisplayContentLocked().getDockedDividerController()
                         .notifyAppVisibilityChanged();
             }