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

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

Index: sky/sdk/lib/framework/components2/radio.dart
diff --git a/sky/sdk/lib/framework/components2/radio.dart b/sky/sdk/lib/framework/components2/radio.dart
index 4a4781cd72efb586727a1677c1018e065091fda8..5e4be29be2d15079681122eda551275497f231e1 100644
--- a/sky/sdk/lib/framework/components2/radio.dart
+++ b/sky/sdk/lib/framework/components2/radio.dart
@@ -16,15 +16,22 @@ class Radio extends ButtonBase {
 
   Radio({
     Object key,
-    this.onChanged,
     this.value,
-    this.groupValue
+    this.groupValue,
+    this.onChanged
   }) : super(key: key);
 
   Object value;
   Object groupValue;
   ValueChanged onChanged;
 
+  void syncFields(Radio source) {
+    value = source.value;
+    groupValue = source.groupValue;
+    onChanged = source.onChanged;
+    super.syncFields(source);
+  }
+
   UINode buildContent() {
     // TODO(jackson): This should change colors with the theme
     Color color = highlight ? colors.Purple[500] : const Color(0x8A000000);