[Overview] Allow selecting windows in lightbox mode

Make the event blocking done by Lightbox optional - leave it activated
when displaying the run dialog, but deactivate it when highlighting
windows in the overview.

https://bugzilla.gnome.org/show_bug.cgi?id=602774

js/ui/appDisplay.js

@@ -433,6 +433,8 @@ AppWellIcon.prototype = {
     },
 
     highlightWindow: function(metaWindow) {
+        if (this._didActivateWindow)
+            return;
         if (!this._getRunning())
             return;
         Main.overview.getWorkspacesForWindow(metaWindow).setHighlightWindow(metaWindow);
@@ -450,6 +452,7 @@ AppWellIcon.prototype = {
         if (this._getRunning()) {
             Main.overview.getWorkspacesForWindow(null).setApplicationWindowSelection(this.app.get_id());
             this._setWindowSelection = true;
+            this._didActivateWindow = false;
         }
     },