Remove one more use of mirrors: Components now have to explicitly sync their fields.

sky/sdk/lib/framework/components2/icon_button.dart

Index: sky/sdk/lib/framework/components2/icon_button.dart
diff --git a/sky/sdk/lib/framework/components2/icon_button.dart b/sky/sdk/lib/framework/components2/icon_button.dart
index b7b7deefcdd60c9a3a2370216d3dba4d22a7bff2..bf9db14b23b52fe6a292dcd517628567284ad548 100644
--- a/sky/sdk/lib/framework/components2/icon_button.dart
+++ b/sky/sdk/lib/framework/components2/icon_button.dart
@@ -14,6 +14,12 @@ class IconButton extends Component {
   String icon;
   GestureEventListener onGestureTap;
 
+  void syncFields(IconButton source) {
+    icon = source.icon;
+    onGestureTap = source.onGestureTap;
+    super.syncFields(source);
+  }
+
   UINode build() {
     return new EventListenerNode(
       new Padding(