Convert DOM and HTML frog to dart2js.

lib/dom/templates/html/impl/impl_Document.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.
 
 class $CLASSNAME extends _NodeImpl implements Document
-$if FROG
+$if DART2JS
     native "*HTMLDocument"
 $endif
 {
 
 $!MEMBERS
   // TODO(jacobr): implement all Element methods not on Document. 
 
   _ElementImpl query(String selectors) {
     // It is fine for our RegExp to detect element id query selectors to have
     // false negatives but not false positives.
@@ skipping 19 matching lines @@
       final copyOfMatches = new List<Element>(len);
       for (int i = 0; i < len; ++i) {
         copyOfMatches[i] = mutableMatches[i];
       }
       return new _FrozenElementList._wrap(copyOfMatches);
     } else {
       return new _FrozenElementList._wrap($dom_querySelectorAll(selectors));
     }
   }
 }