anchor.diff:        return;
       }
   
  +    ga?.sendEvent('execution', 'initiated');
  +
       editorIsBusy = true;
       testResultBox.hide();
       hintBox.hide();
  
positive.code:           .compile(input)
            .timeout(longServiceCallTimeout)
            .then((CompileResponse response) {
          return executionSvc.execute(
              context.htmlSource, context.cssSource, response.result);
        }).catchError((e, st) {
          consoleExpandController
              .appendError('Error compiling to JavaScript:\n$e');
          print(st);
        }).whenComplete(() {
          webOutputLabel.setAttr('hidden');
          editorIsBusy = false;
  
negative.code:           response.result,
            modulesBaseUrl: response.modulesBaseUrl,
          );
          ga?.sendEvent('execution', 'ddc-compile-success');
        }).catchError((e, st) {
          consoleExpandController
              .appendError('Error compiling to JavaScript:\n$e');
          print(st);
          ga?.sendEvent('execution', 'ddc-compile-failure');
        }).whenComplete(() {
          webOutputLabel.setAttr('hidden');
          editorIsBusy = false;
  