anchor.diff:                  'loading Gist ID $gistId.');
         }
       }
  +  }
  +
  +  void _resetCode() {
  +    setContextSources(lastInjectedSourceCode);
     }
   
     void setContextSources(Map<String, String> sources) {
  
positive.code:     reloadGistButton = DisableableButton(querySelector('#reload-gist'), () {
        if (gistId.isNotEmpty) {
          _loadAndShowGist(gistId);
        }
      });
  
      reloadGistButton.disabled = gistId.isEmpty;
  
      showHintButton = DisableableButton(querySelector('#show-hint'), () {
        var hintElement = DivElement()..text = context.hint;
  
negative.code:     userCodeEditor.readOnly = value;
      executeButton.disabled = value;
      formatButton.disabled = value;
      reloadGistButton.disabled = value;
      showHintButton?.disabled = value;
    }
  
  