Fix bug 15417

tools/dom/src/AttributeMap.dart

 // 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.
 
 part of html;
 
 abstract class _AttributeMap implements Map<String, String> {
   final Element _element;
 
   _AttributeMap(this._element);
 
+  void addAll(Map<String, String> other) {
+    other.forEach((k, v) { this[k] = v; });
+  }
+
   bool containsValue(String value) {
     for (var v in this.values) {
       if (value == v) {
         return true;
       }
     }
     return false;
   }
 
   String putIfAbsent(String key, String ifAbsent()) {
@@ skipping 136 matching lines @@
  * dataSet in the old DOM.
  */
 class _DataAttributeMap implements Map<String, String> {
 
   final Map<String, String> _attributes;
 
   _DataAttributeMap(this._attributes);
 
   // interface Map
 
+  void addAll(Map<String, String> other) {
+    other.forEach((k, v) { this[k] = v; });
+  }
+
   // TODO: Use lazy iterator when it is available on Map.
   bool containsValue(String value) => values.any((v) => v == value);
 
   bool containsKey(String key) => _attributes.containsKey(_attr(key));
 
   String operator [](String key) => _attributes[_attr(key)];
 
   void operator []=(String key, String value) {
     _attributes[_attr(key)] = value;
   }
@@ skipping 72 matching lines @@
   String _toHyphenedName(String word) {
     var sb = new StringBuffer();
     for (int i = 0; i < word.length; i++) {
       var lower = word[i].toLowerCase();
       if (word[i] != lower && i > 0) sb.write('-');
       sb.write(lower);
     }
     return sb.toString();
   }
 }