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/messageTray.js

@@ -1457,7 +1457,7 @@ const MessageTray = new Lang.Class({
                                                               track_hover: true });
         this._summaryBoxPointer.actor.style_class = 'summary-boxpointer';
         this._summaryBoxPointer.actor.hide();
-        Main.layoutManager.addChrome(this._summaryBoxPointer.actor, { visibleInFullscreen: true });
+        Main.layoutManager.addChrome(this._summaryBoxPointer.actor);
 
         this._summaryBoxPointerItem = null;
         this._summaryBoxPointerContentUpdatedId = 0;