dart:html perf optimization based on runing Dromaeo benchmarks

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

 // Copyright (c) 2011, 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 _AttributeClassSet extends _CssClassSet {
   _AttributeClassSet(element) : super(element);
 
-  String _className() => _element.attributes['class'];
+  String $dom_className() => _element.attributes['class'];
 
   void _write(Set s) {
     _element.attributes['class'] = _formatSet(s);
   }
 }
 
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   Set<String> get classes() {
     if (_cssClassSet === null) {
       _cssClassSet = new _AttributeClassSet(_ptr);
@@ skipping 26 matching lines @@
   void set innerHTML(String svg) {
     final container = new Element.tag("div");
     // Wrap the SVG string in <svg> so that SVGElements are created, rather than
     // HTMLElements.
     container.innerHTML = '<svg version="1.1">$svg</svg>';
     this.elements = container.elements.first.elements;
   }
 
 $!MEMBERS
 }