Move frog dart:dom from fields to getters/setters.

client/dom/generated/src/frog/MessageEvent.dart

Index: client/dom/generated/src/frog/MessageEvent.dart
diff --git a/client/dom/generated/src/frog/MessageEvent.dart b/client/dom/generated/src/frog/MessageEvent.dart
index d125f2db1674c383e6dc76a84ed4b0a776663bb8..2671dd2d9bfa06c6d9e51e6206985fae812d9588 100644
--- a/client/dom/generated/src/frog/MessageEvent.dart
+++ b/client/dom/generated/src/frog/MessageEvent.dart
@@ -1,15 +1,15 @@
 
 class MessageEvent extends Event native "*MessageEvent" {
 
-  Object data;
+  Object get data() native "return this.data;";
 
-  String lastEventId;
+  String get lastEventId() native "return this.lastEventId;";
 
-  String origin;
+  String get origin() native "return this.origin;";
 
-  List ports;
+  List get ports() native "return this.ports;";
 
-  DOMWindow source;
+  DOMWindow get source() native "return this.source;";
 
   void initMessageEvent(String typeArg, bool canBubbleArg, bool cancelableArg, Object dataArg, String originArg, String lastEventIdArg, DOMWindow sourceArg, List messagePorts) native;