Fixing up setting styles to invalidate on IE9.

lib/html/dart2js/html_dart2js.dart

Index: lib/html/dart2js/html_dart2js.dart
diff --git a/lib/html/dart2js/html_dart2js.dart b/lib/html/dart2js/html_dart2js.dart
index f470f2d78d2fae2350579d1fb027bc3ec56e26ce..631809305fc67ebc39e58e6402a524bfd5fccc73 100644
--- a/lib/html/dart2js/html_dart2js.dart
+++ b/lib/html/dart2js/html_dart2js.dart
@@ -944,8 +944,6 @@ class _CSSStyleDeclarationImpl implements CSSStyleDeclaration native "*CSSStyleD
 
   String removeProperty(String propertyName) native;
 
-  void setProperty(String propertyName, String value, [String priority]) native;
-
 
   // TODO(jacobr): generate this list of properties using the existing script.
     /** Gets the value of "animation" */
@@ -3710,6 +3708,13 @@ class _CSSStyleDeclarationImpl implements CSSStyleDeclaration native "*CSSStyleD
   void set zoom(var value) {
     setProperty('zoom', value, '');
   }
+
+  void setProperty(String propertyName, String value, [String priority]) native '''
+    this.setProperty(propertyName, value, priority);
+    if (this.setAttribute) {
+      this.setAttribute(propertyName, value);
+    }
+  ''';
 }
 
 class _CSSStyleRuleImpl extends _CSSRuleImpl implements CSSStyleRule native "*CSSStyleRule" {