Added MappedListIterable/Iterator to implement map() on Lists.

tools/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.
 
 part of $LIBRARYNAME;
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements List {
   // Raw Element.
@@ skipping 44 matching lines @@
       }
     }
     return false;
   }
 
   String join([String separator]) {
     return IterableMixinWorkaround.joinList(this, separator);
   }
 
   Iterable map(f(Element element)) {
-    return IterableMixinWorkaround.map(this, f);
+    return IterableMixinWorkaround.mapList(this, f);
   }
 
   List mappedBy(f(Element element)) {
     return IterableMixinWorkaround.mappedByList(this, f);
   }
 
   Iterable<Element> where(bool f(Element element)) {
     return IterableMixinWorkaround.where(this, f);
   }
 
@@ skipping 196 matching lines @@
     for (Element el in this) {
       f(el);
     }
   }
 
   String join([String separator]) {
     return IterableMixinWorkaround.joinList(this, separator);
   }
 
   Iterable map(f(Element element)) {
-    return IterableMixinWorkaround.map(this, f);
+    return IterableMixinWorkaround.mapList(this, f);
   }
 
   List mappedBy(f(Element element)) {
     return IterableMixinWorkaround.mappedByList(this, f);
   }
 
   Iterable<Element> where(bool f(Element element)) {
     return IterableMixinWorkaround.where(this, f);
   }
 
@@ skipping 734 matching lines @@
 $if DART2JS
   // Optimization to improve performance until the dart2js compiler inlines this
   // method.
   static dynamic createElement_tag(String tag) =>
       JS('Element', 'document.createElement(#)', tag);
 $else
   static Element createElement_tag(String tag) =>
       document.$dom_createElement(tag);
 $endif
 }