ExtJS 4.2: Migrate buttonDownlaod (not tested).

static/plugin_dbui/src/buttondownload.js

@@ -4,7 +4,7 @@
  */
 Ext.define('App.ButtonDownload', {
 
-    extend: 'Ext.Button',
+    extend: 'Ext.button.Button',
     alias: 'widget.xbuttondownload',
 
     /**
@@ -16,10 +16,8 @@ Ext.define('App.ButtonDownload', {
      // private method requests by the component model of ExtJS
     initComponent: function () {
 
-        "use strict";
-
-        // initialize the underlying class
-        App.ButtonDownload.superclass.initComponent.call(this);
+        // initialize the base class
+        this.callParent(arguments);
 
         // download when the button is pressed
         this.on('click', this.onDownload, this);