Add button to add new FSP services to Files app.

ui/file_manager/file_manager/foreground/js/file_manager.js

Index: ui/file_manager/file_manager/foreground/js/file_manager.js
diff --git a/ui/file_manager/file_manager/foreground/js/file_manager.js b/ui/file_manager/file_manager/foreground/js/file_manager.js
index 2ccc3b9685154e3cbe621104c76a61256a462eeb..c760fb2be7590c5449dfc59be7369ab0c21821c0 100644
--- a/ui/file_manager/file_manager/foreground/js/file_manager.js
+++ b/ui/file_manager/file_manager/foreground/js/file_manager.js
@@ -946,7 +946,10 @@ FileManager.prototype = /** @struct */ {
                            assert(this.metadataModel_),
                            fakeEntriesVisible);
     directoryTree.dataModel = new NavigationListModel(
-        this.volumeManager_, this.folderShortcutsModel_);
+        this.volumeManager_,
+        this.folderShortcutsModel_,
+        new NavigationModelCommandItem(
+          util.queryDecoratedElement('#add-new-services', cr.ui.Command)));
 
     this.ui_.initDirectoryTree(directoryTree);
   };