[webview_flutter]bugfix:webview example should be statefulWidget (#1511)

bugfix:webview example should be statefulWidget 
diff --git a/packages/webview_flutter/CHANGELOG.md b/packages/webview_flutter/CHANGELOG.md
index fc34c1c..8185c00 100644
--- a/packages/webview_flutter/CHANGELOG.md
+++ b/packages/webview_flutter/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.3.5+4
+
+* Fix bugs in the example app by updating it to use a `StatefulWidget`.
+
 ## 0.3.5+3
 
 * Make sure to post javascript channel messages from the platform thread.
diff --git a/packages/webview_flutter/example/lib/main.dart b/packages/webview_flutter/example/lib/main.dart
index 0ec5729..7dfac54 100644
--- a/packages/webview_flutter/example/lib/main.dart
+++ b/packages/webview_flutter/example/lib/main.dart
@@ -24,7 +24,12 @@
 </html>
 ''';
 
-class WebViewExample extends StatelessWidget {
+class WebViewExample extends StatefulWidget {
+  @override
+  _WebViewExampleState createState() => _WebViewExampleState();
+}
+
+class _WebViewExampleState extends State<WebViewExample> {
   final Completer<WebViewController> _controller =
       Completer<WebViewController>();
 
diff --git a/packages/webview_flutter/pubspec.yaml b/packages/webview_flutter/pubspec.yaml
index 77c0ce9..7dc030e 100644
--- a/packages/webview_flutter/pubspec.yaml
+++ b/packages/webview_flutter/pubspec.yaml
@@ -1,6 +1,6 @@
 name: webview_flutter
 description: A Flutter plugin that provides a WebView widget on Android and iOS.
-version: 0.3.5+3
+version: 0.3.5+4
 author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/webview_flutter