Port custom element layout tests to Dart

tests/html/custom/attribute_changed_callback_test.dart

+// Copyright (c) 2013, 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.
+
+library attribute_changed_callback_test;
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+import 'dart:html';
+
+class A extends HtmlElement {
+  static final tag = 'x-a';
+  factory A() => new Element.tag(tag);
+
+  static var attributeChangedInvocations = 0;
+
+  void onAttributeChanged(name, oldValue, newValue) {
+    attributeChangedInvocations++;
+  }
+}
+
+class B extends HtmlElement {
+  static final tag = 'x-b';
+  factory B() => new Element.tag(tag);
+
+  static var invocations = [];
+
+  void onCreated() {
+    invocations.add('created');
+  }
+
+  void onAttributeChanged(name, oldValue, newValue) {
+    invocations.add('$name: $oldValue => $newValue');
+  }
+}
+
+main() {
+  useHtmlConfiguration();
+
+  // Adapted from Blink's fast/dom/custom/attribute-changed-callback test.
+
+  test('transfer attribute changed callback', () {
+    document.register(A.tag, A);
+    var element = new A();
+
+    element.attributes['a'] = 'b';
+    expect(A.attributeChangedInvocations, 1);
+  });
+
+  test('add, change and remove an attribute', () {
+    document.register(B.tag, B);
+    var b = new B();
+    b.id = 'x';
+    expect(B.invocations, ['created', 'id: null => x']);
+
+    B.invocations = [];
+    b.attributes.remove('id');
+    expect(B.invocations, ['id: x => null']);
+
+    B.invocations = [];
+    b.attributes['data-s'] = 't';
+    expect(B.invocations, ['data-s: null => t']);
+
+    B.invocations = [];
+    b.classList.toggle('u');
+    expect(B.invocations, ['class: null => u']);
+
+    b.attributes['data-v'] = 'w';
+    B.invocations = [];
+    b.attributes['data-v'] = 'x';
+    expect(B.invocations, ['data-v: w => x']);
+
+    B.invocations = [];
+    b.attributes['data-v'] = 'x';
+    expect(B.invocations, []);
+  });
+}