LayoutManager: reverse the visibleInFullscreen flag

Change visibleInFullscreen to be trackFullscreen. If true, visibility
is fully bound to fullscreen status, if false, no change is made.
This allows to avoid set_skip_paint(), while not messing with
visibility of actors that are sometimes hidden for other reasons.
The flag was reversed because only the panel uses it, so false is
a more useful default.

https://bugzilla.gnome.org/show_bug.cgi?id=619955

js/ui/keyboard.js

@@ -93,7 +93,7 @@ const Key = new Lang.Class({
             this._getExtendedKeys();
             this.actor._extended_keys = this._extended_keyboard;
             this._boxPointer.actor.hide();
-            Main.layoutManager.addChrome(this._boxPointer.actor, { visibleInFullscreen: true });
+            Main.layoutManager.addChrome(this._boxPointer.actor);
         }
     },