Fixing SVGElement.classes.

sdk/lib/svg/dart2js/svg_dart2js.dart

Index: sdk/lib/svg/dart2js/svg_dart2js.dart
diff --git a/sdk/lib/svg/dart2js/svg_dart2js.dart b/sdk/lib/svg/dart2js/svg_dart2js.dart
index 9423c1fabb1c90c6912f5c72e294be83b5530b28..ef6935a5314d35df6a1185989893e970b7303f9b 100644
--- a/sdk/lib/svg/dart2js/svg_dart2js.dart
+++ b/sdk/lib/svg/dart2js/svg_dart2js.dart
@@ -1090,6 +1090,9 @@ class _AttributeClassSet extends CssClassSet {
     var classname = _element.attributes['class'];
 
     Set<String> s = new Set<String>();
+    if (classname == null) {
+      return s;
+    }
     for (String name in classname.split(' ')) {
       String trimmed = name.trim();
       if (!trimmed.isEmpty) {
@@ -1100,7 +1103,8 @@ class _AttributeClassSet extends CssClassSet {
   }
 
   void writeClasses(Set s) {
-    _element.attributes['class'] = _formatSet(s);
+    List list = new List.from(s);
+    _element.attributes['class'] = Strings.join(list, ' ');
   }
 }
 
@@ -1110,9 +1114,10 @@ class SVGElement extends Element native "*SVGElement" {
   factory SVGElement.svg(String svg) =>
       _SVGElementFactoryProvider.createSVGElement_svg(svg);
 
+  _AttributeClassSet _cssClassSet;
   CssClassSet get classes {
     if (_cssClassSet == null) {
-      _cssClassSet = new _AttributeClassSet(_ptr);
+      _cssClassSet = new _AttributeClassSet(this);
     }
     return _cssClassSet;
   }