anchor.diff:    @override
     void attached() {
       super.attached();
  +    assert(['local', 'inline'].contains(entryPoint));
  +
  +    _registerDesignerProxyListener();
     }
   
     Future load() {
  
positive.code:   }
  
    void _onWebviewContentLoad(_) {
      _tweakUI();
      _registerDesignerProxyListener();
      _injectDesignerProxy().then((_) => _webviewReady.complete());
    }
  
    void _tweakUI() {
      // TODO(ussuri): Some of this will become unnecessary once BUG #3467 is
      // resolved.
      _insertCssIntoWebview(r'''
          /* Reduce default font sizes */
          html /deep/ *, html /deep/ #tabs > * {
            font-size: 13px;
          }
  
negative.code:   }
  
    void _registerDesignerProxyListener() {
      chrome.runtime.onMessage.listen((chrome.OnMessageEvent event) {
        // TODO(ussuri): Check the sender?
        if (event.message['type'] == 'export_code_response') {
          _codeExported.complete("${event.message['code']}");
  