Fixing custom element type extensions in Dartium to have correct native type ID

tests/html/custom/document_register_type_extensions_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 document_register_type_extensions_test;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_individual_config.dart';
 import 'dart:html';
 import '../utils.dart';
 
@@ skipping 27 matching lines @@
   factory Qux() => new Element.tag('input', tag);
   Qux.created() : super.created();
 }
 
 class FooBad extends DivElement {
   static const tag = 'x-foo';
   factory FooBad() => new Element.tag('div', tag);
   FooBad.created() : super.created();
 }
 
+class MyCanvas extends CanvasElement {
+  static const tag = 'my-canvas';
+  factory MyCanvas() => new Element.tag('canvas', tag);
+
+  MyCanvas.created() : super.created();
+
+  void fillAsRed() {
+    width = 100;
+    height = 100;
+
+    var context = this.getContext('2d');
+    context.fillStyle = 'red';
+    context.fillRect(0, 0, width, height);
+    context.fill();
+
+    var data = context.getImageData(0, 0, 1, 1).data;
+    expect(data, [255, 0, 0, 255]);
+  }
+}
+
 main() {
   useHtmlIndividualConfiguration();
 
   // Adapted from Blink's fast/dom/custom/document-register-type-extension test.
 
   var testForm = new FormElement()..id = 'testForm';
   document.body.append(testForm);
 
   var isFormControl = (element) {
     testForm.append(element);
     return element.form == testForm;
   };
 
   var registeredTypes = false;
   void registerTypes() {
     if (registeredTypes) {
       return;
     }
     registeredTypes = true;
     document.register(Foo.tag, Foo);
     document.register(Bar.tag, Bar, extendsTag: 'input');
     document.register(Baz.tag, Baz);
     document.register(Qux.tag, Qux, extendsTag: 'input');
+    document.register(MyCanvas.tag, MyCanvas, extendsTag: 'canvas');
   }
 
   setUp(loadPolyfills);
 
   group('registration', () {
     setUp(registerTypes);
 
     test('cannot register twice', () {
       expect(() => document.register(FooBad.tag, Foo), throws);
     });
@@ skipping 179 matching lines @@
       // Polyfill does not convert parsed unregistered custom elements to
       // HtmlElement.
       // expect(namedBarParsed is UnknownElement, isFalse);
       expect(namedBarParsed is HtmlElement, isTrue);
 
       var divBarParsed = createElementFromHtml('<div is=x-bar>');
       expect(divBarParsed is Bar, isFalse);
       expect(divBarParsed is DivElement, isTrue);
     });
   });
+
+  group('functional', () {
+    setUp(registerTypes);
+
+    test('canvas', () {
+      var canvas = new MyCanvas();
+      canvas.fillAsRed();
+    });
+  });
 }