anchor.diff:    }
   }
   
  +// TODO: This should be moved into the ui/ directory.
   class ActivitySpinner {
     Element element;
   
  -  static ActivitySpinner _instance;
  -
  -  factory ActivitySpinner(Spark spark) {
  -    if (_instance == null) {
  -      _instance = new ActivitySpinner._internal(spark);
  -    }
  -    return _instance;
  +  ActivitySpinner(Spark spark, {id}) {
  +    element = spark.getUIElement(id);
     }
   
     void setShowing(bool showing) {
       element.style.opacity = showing ? '1' : '0';
  -  }
  -
  -  ActivitySpinner._internal(Spark spark) {
  -    element = spark.getUIElement('#activitySpinner');
     }
   }
   
  
positive.code:         allowsLabelBar: true);
    }
  
    void initJobManager() {
      _activitySpinner = new ActivitySpinner(this);
      _activitySpinner.setShowing(false);
  
      _jobManager = new JobManager();
      _jobManager.onChange.listen(onJobManagerData);
    }
  
    void onJobManagerData(JobManagerEvent event) {
      // TODO: This might cause the spinner to "blink" between jobs.
      bool showSpinner = (event.finished != true);
      this._activitySpinner.setShowing(showSpinner);
    }
  
    void initEditorManager() {
  
negative.code: 
    final bool developerMode;
  
    JobManager jobManager = new JobManager();
    ActivitySpinner _activitySpinner;
  
    AceContainer _aceContainer;
  