Migrate dom tests to dart:html.

lib/dom/templates/html/impl/impl_Element.darttemplate

 // Copyright (c) 2012, 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.
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements ElementList {
   // Raw Element.
   final _ElementImpl _element;
   final _HTMLCollectionImpl _childElements;
@@ skipping 316 matching lines @@
 
   String operator [](String key) {
     return _element.$dom_getAttribute(key);
   }
 
   void operator []=(String key, value) {
     _element.$dom_setAttribute(key, '$value');
   }
 
   String putIfAbsent(String key, String ifAbsent()) {
     if (!containsKey(key)) {

[Anton Muhin, 2012/04/26 18:47:36]

technically you can use Maps.putIfAbsent here as you change this method anyway.

       this[key] = ifAbsent();
     }
+    return this[key];
   }
 
   String remove(String key) {
+    String value = _element.$dom_getAttribute(key);
     _element.$dom_removeAttribute(key);
+    return value;
   }
 
   void clear() {
     final attributes = _element.$dom_attributes;
     for (int i = attributes.length - 1; i >= 0; i--) {
       remove(attributes[i].name);
     }
   }
 
   void forEach(void f(String key, String value)) {
@@ skipping 55 matching lines @@
   bool containsValue(String value) => getValues().some((v) => v == value);
 
   bool containsKey(String key) => $dom_attributes.containsKey(_attr(key));
 
   String operator [](String key) => $dom_attributes[_attr(key)];
 
   void operator []=(String key, value) {
     $dom_attributes[_attr(key)] = '$value';
   }
 
-  String putIfAbsent(String key, String ifAbsent()) {
+  String putIfAbsent(String key, String ifAbsent()) =>
     $dom_attributes.putIfAbsent(_attr(key), ifAbsent);
-  }
 
   String remove(String key) => $dom_attributes.remove(_attr(key));
 
   void clear() {
     // Needs to operate on a snapshot since we are mutating the collection.
     for (String key in getKeys()) {
       remove(key);
     }
   }
 
@@ skipping 340 matching lines @@
 
   /** @domName Document.createElement */
 $if FROG
   // Optimization to improve performance until the frog compiler inlines this
   // method.
   factory Element.tag(String tag) native "return document.createElement(tag)";
 $else
   factory Element.tag(String tag) => _document.$dom_createElement(tag);
 $endif
 }