[element_embedding_demo] migrate to dart:js_interop (#2231)

web_embedding/element_embedding_demo/lib/main.dart

@@ -1,10 +1,8 @@
-// ignore_for_file: avoid_web_libraries_in_flutter
-
 import 'dart:async';
+import 'dart:js_interop' as js;
+import 'dart:js_interop_unsafe' as js_util;
 
 import 'package:flutter/material.dart';
-import 'package:js/js.dart' as js;
-import 'package:js/js_util.dart' as js_util;
 
 void main() {
   runApp(const MyApp());
@@ -28,9 +26,9 @@ class _MyAppState extends State<MyApp> {
   @override
   void initState() {
     super.initState();
-    final export = js_util.createDartExport(this);
+    final export = js.createJSInteropWrapper(this);
-    js_util.setProperty(js_util.globalThis, '_appState', export);
+    js.globalContext['_appState'] = export;
-    js_util.callMethod<void>(js_util.globalThis, '_stateSet', []);
+    js.globalContext.callMethod('_stateSet'.toJS);
   }
 
   @override

web_embedding/element_embedding_demo/pubspec.yaml

@@ -10,7 +10,6 @@ dependencies:
   cupertino_icons: ^1.0.2
   flutter:
     sdk: flutter
-  js: ^0.7.0
 
 dev_dependencies:
   flutter_test: