gestures: Restrict actions based on keybindingMode

Just like keybindings and the message tray pointer barrier, gestures
don't always make sense - for instance, swiping up the screen shield
should not trigger the message tray just as the SelectArea action around
the left edge should not open the overview.
To avoid this, restrict gestures based on the current keybinding mode.

https://bugzilla.gnome.org/show_bug.cgi?id=740237

js/ui/messageTray.js

@@ -1951,7 +1951,9 @@ const MessageTray = new Lang.Class({
         this._messageTrayMenuButton.actor.connect('key-press-event',
                                                   Lang.bind(this, this._onTrayButtonKeyPress));
 
-        let gesture = new EdgeDragAction.EdgeDragAction(St.Side.BOTTOM);
+        let gesture = new EdgeDragAction.EdgeDragAction(St.Side.BOTTOM,
+                                                        Shell.KeyBindingMode.NORMAL |
+                                                        Shell.KeyBindingMode.OVERVIEW);
         gesture.connect('activated', Lang.bind(this, this.toggle));
         global.stage.add_action(gesture);
     },