[dart:html] rename register to registerElement per spec

tests/html/custom/js_custom_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 js_custom_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'dart:html';
 import '../utils.dart';
@@ skipping 13 matching lines @@
   useHtmlConfiguration();
 
   // Adapted from Blink's
   // fast/dom/custom/constructor-calls-created-synchronously test.
 
   var registered = false;
   setUp(() {
     return customElementsReady.then((_) {
       if (!registered) {
         registered = true;
-        document.register(A.tag, A);
+        document.registerElement(A.tag, A);
       }
     });
   });
 
   test('accessing custom Dart element from JS', () {
     var a = new A();
     a.id = 'a';
     document.body.append(a);
 
     var script = '''
       document.querySelector('#a').setAttribute('fromJS', 'true');
     ''';
     document.body.append(new ScriptElement()..text = script);
 
     expect(a.attributes['fromJS'], 'true');
   });
 
   test('accessing custom JS element from Dart', () {
     var script = '''
-    var Foo = document.register('x-foo', {
+    var Foo = document.registerElement('x-foo', {
       prototype: Object.create(HTMLElement.prototype, {
         createdCallback: {
           value: function() {
             this.setAttribute('fromJS', 'true');
           }
         }
       })});
     var foo = new Foo();
     foo.id = 'b';
     document.body.appendChild(foo);
     ''';
 
     document.body.append(new ScriptElement()..text = script);
     var custom = document.querySelector('#b');
     expect(custom is HtmlElement, isTrue);
     expect(custom.attributes['fromJS'], 'true');
   });
 }