Add test for initialization of the native interceptor dispatch property.

tests/html/js_dispatch_property_test.dart

+// Copyright (c) 2016, 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.
+
+// Test for dart2js initialization of dispatchPropertyName.
+
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+
+import 'package:expect/expect.dart' show NoInline, AssumeDynamic;
+
+import 'js_dispatch_property_test_lib.dart';
+
+@NoInline() @AssumeDynamic()
+confuse(x) => x;
+
+main() {
+  useHtmlConfiguration();
+
+  group('group', () {
+    test('test', () {
+      // Force dynamic interceptor dispatch.
+      var a = confuse(create());
+      expect(a.foo('A'), equals('Foo A'));
+    });
+  });
+}