Review feedback from globalContext change (#69)

And add test

lib/helpers.dart

@@ -53,7 +53,7 @@ Element? querySelector(String selectors) => document.querySelector(selectors);
 
 bool isInstanceOfDomType(JSObject? o, String domType) {
   if (o == null) return false;
-  final constructor = globalContext.getProperty(domType.toJS);
+  final constructor = globalContext[domType];
   if (constructor == null) return false;
   return o.instanceof(constructor as JSFunction).toDart;
 }

pubspec.yaml

@@ -6,7 +6,7 @@ version: 0.1.5-wip
 repository: https://github.com/dart-lang/web
 
 environment:
-  sdk: ">=3.2.0-75.0.dev <4.0.0"
+  sdk: ">=3.2.0-157.0.dev <4.0.0"
 
 dev_dependencies:
   args: ^2.4.0

test/helpers_test.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@TestOn('browser')
+library;
+
+import 'package:test/test.dart';
+import 'package:web/helpers.dart';
+
+void main() {
+  test('isInstanceOfDomType', () {
+    final div = document.createElement('div');
+
+    expect(isInstanceOfDomType(div, 'bob'), false);
+    expect(isInstanceOfDomType(div, 'HTMLDivElement'), true);
+  });
+}