anchor.diff:      return _codeExported.future;
     }
   
  -  void _onContentLoad(_) {
  +  void _onWebviewContentLoad(_) {
       _tweakUI();
  -    _registerWebviewProxyListener();
  -    _injectWebviewProxy().then((_) => _webviewReady.complete());
  +    _registerDesignerProxyListener();
  +    _injectDesignerProxy().then((_) => _webviewReady.complete());
     }
   
     Future _tweakUI() {
  +    // Hide some parts of the UI we don't want.
       _insertCssIntoWebview(r'''
  -        #designer::shadow > #appbar > * { display: none; } 
  -        #designer::shadow > #appbar > .design-controls { display: block; }
  +        #designer::shadow > #appbar > * { 
  +          display: none;
  +        } 
  +        #designer::shadow > #appbar > .design-controls {
  +          display: block;
  +        }
  +        #designer::shadow > #appbar > .design-controls > .separator:first-child {
  +          display: none;
  +        }
       ''');
     }
   
  -  void _registerWebviewProxyListener() {
  +  void _registerDesignerProxyListener() {
       chrome.runtime.onMessage.listen((OnMessageEvent event) {
         // TODO(ussuri): Check the sender?
         if (event.message['type'] == 'export_code_response') {
  
positive.code:     ''');
    }
  
    Future _injectWebviewScriptingContextScript(String script) {
      script = script.replaceAll('"', r'\"').replaceAll('\n', r'\n');
      return _executeScriptInWebview(r'''
          (function() {
  
negative.code:   void attached() {
      super.attached();
  
      _webviewReady = new Completer();
      _webview = new js.JsObject.fromBrowserObject($['webview']);
      _webview.callMethod('addEventListener', ['contentload', _onWebviewContentLoad]);
    }
  
    Future reload() {
      _webviewReady = new Completer();
      final completer = new Completer();
      _webview.callMethod('reload', [(_) => completer.complete()]);
      return completer.future;
  