anchor.diff:    TestDriver _testDriver;
   
     Spark(this.developerMode) {
  -    if (SPARK_SINGLETON == null) {
  -      SPARK_SINGLETON = this;
  -    }
  -
       document.title = appName;
   
       localPrefs = preferences.localStore;
  
positive.code:   ws.Workspace workspace;
    EditorManager editorManager;
    EditorArea editorArea;
    analytics.Tracker tracker = new analytics.NullTracker();
  
    preferences.PreferenceStore localPrefs;
    preferences.PreferenceStore syncPrefs;
  
negative.code:   void _invoke([Object context]) {
      if (isPolymer || !_initialized) {
        var checkbox = getElement('#analyticsCheck');
        checkbox.checked = _isTrackingPermitted;
        checkbox.onChange.listen((e) => _isTrackingPermitted = checkbox.checked);
  
        getElement('#aboutVersion').text = spark.appVersion;
  
  