chore(Test): Add a test for angulardart#1540.

_tests/test/regression/1540_reset_deferred_query_test.dart

@@ -0,0 +1,46 @@
+@TestOn('browser')
+import 'package:angular/angular.dart';
+import 'package:angular_test/angular_test.dart';
+import 'package:test/test.dart';
+
+import '1540_reset_deferred_query_test.template.dart' as ng;
+
+void main() {
+  tearDown(disposeAnyRunningTest);
+
+  test('@deferred should work properly with queries', () async {
+    final fixture = await NgTestBed.forComponent(
+      ng.ViewChildTestNgFactory,
+    ).create();
+    expect(fixture.assertOnlyInstance.child, isNull);
+    await fixture.update((c) => c.showChild = true);
+    expect(fixture.assertOnlyInstance.child, isNotNull);
+    await fixture.update((c) => c.showChild = false);
+    expect(fixture.assertOnlyInstance.child, isNull);
+  });
+}
+
+@Component(
+  selector: 'view-child-test',
+  directives: [
+    HelloWorldComponent,
+    NgIf,
+  ],
+  template: r'''
+    <template [ngIf]="showChild">
+      <hello-world @deferred></hello-world>
+    </template>
+  ''',
+)
+class ViewChildTest {
+  @ViewChild(HelloWorldComponent)
+  HelloWorldComponent child;
+
+  bool showChild = false;
+}
+
+@Component(
+  selector: 'hello-world',
+  template: 'Hello World',
+)
+class HelloWorldComponent {}