Don't cache SVG CssClassSet

tools/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.
 
 part of $LIBRARYNAME;
 
 class _AttributeClassSet extends CssClassSetImpl {
   final Element _element;
 
   _AttributeClassSet(this._element);
@@ skipping 36 matching lines @@
     if (match != null && match.group(1).toLowerCase() == 'svg') {
       parentElement = document.body;
     } else {
       parentElement = new SvgSvgElement();
     }
     var fragment = parentElement.createFragment(svg, validator: validator,
         treeSanitizer: treeSanitizer);
     return fragment.nodes.where((e) => e is SvgElement).single;
   }
 
-  _AttributeClassSet _cssClassSet;
-  CssClassSet get classes {
-    if (_cssClassSet == null) {
-      _cssClassSet = new _AttributeClassSet(this);
-    }
-    return _cssClassSet;
-  }
+  CssClassSet get classes => new _AttributeClassSet(this);
 
   List<Element> get children => new FilteredElementList<Element>(this);
 
   void set children(List<Element> value) {
     final children = this.children;
     children.clear();
     children.addAll(value);
   }
 
   String get outerHtml {
@@ skipping 69 matching lines @@
    * Checks to see if the SVG element type is supported by the current platform.
    *
    * The tag should be a valid SVG element tag name.
    */
   static bool isTagSupported(String tag) {
     var e = new $CLASSNAME.tag(tag);
     return e is $CLASSNAME && !(e is UnknownElement);
   }
 $!MEMBERS
 }