anchor.diff:        if (_aceEditor.readOnly) {
           _aceEditor.readOnly = false;
         }
  +
  +      _foldListenerSubscription = currentSession.onChangeFold.listen((_) {
  +        setMarkers(file.getMarkers());
  +      });
  +
  +      // TODO(ericarnold): Markers aren't shown until file is edited.  Fix.
  +      setMarkers(file.getMarkers());
       }
   
       // Setup the code completion options for the current file type.
  
positive.code:   ace.Editor _aceEditor;
  
    workspace.Marker _currentMarker;
  
    static bool get available => js.context['ace'] != null;
  
  
negative.code:   ace.EditSession get currentSession => _aceEditor.session;
  
    void switchTo(ace.EditSession session, [workspace.File file]) {
      if (_foldListenerSubscription != null) {
        _foldListenerSubscription.cancel();
        _foldListenerSubscription = null;
      }
  
      if (session == null) {
        _aceEditor.session = ace.createEditSession('', new ace.Mode('ace/mode/text'));
        _aceEditor.readOnly = true;
  