title: Flutter Web factoryFunction is PlatformViewFactory || factoryFunction is ParameterizedPlatformViewFactory is not true
body: <p>I got this error on Flutter Web WebView stuations</p>
  <p>my code base look like this</p>
  <pre class="lang-dart prettyprint-override"><code>ui.platformViewRegistry.registerViewFactory(
      'someKey',
      (int _) =&gt; getIframe()
        ..id = 'SomeIframeId'
        ..src = url ?? &quot;data:text/html;base64,${Constant.contentBase64}&quot;
        ..style.border = 'none' as html.IFrameElement,
    );
  </code></pre>
  <p>this code base was work before Flutter 3.3.0 update can anyone know solution</p>
  <p>The complete error:
  <strong>Assertion failed: org-dartlang-sdk:///flutter_web_sdk/lib/_engine/engine/platform_views/content_manager.dart:67:12
  factoryFunction is PlatformViewFactory ||
  factoryFunction is ParameterizedPlatformViewFactory
  is not true</strong></p>