Use fields in hidden native DOM classes instead of getters/setters.

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

Index: client/dom/generated/src/frog/StyleSheet.dart
diff --git a/client/dom/generated/src/frog/StyleSheet.dart b/client/dom/generated/src/frog/StyleSheet.dart
index 15fd3b3c990fb92f721656cc18799a1b4c4d01ca..00a1b69699afbe6718681c96bd1ebd26e0658e3b 100644
--- a/client/dom/generated/src/frog/StyleSheet.dart
+++ b/client/dom/generated/src/frog/StyleSheet.dart
@@ -1,19 +1,17 @@
 
 class _StyleSheetJs extends _DOMTypeJs implements StyleSheet native "*StyleSheet" {
 
-  bool get disabled() native "return this.disabled;";
+  bool disabled;
 
-  void set disabled(bool value) native "this.disabled = value;";
+  final String href;
 
-  String get href() native "return this.href;";
+  final _MediaListJs media;
 
-  _MediaListJs get media() native "return this.media;";
+  final _NodeJs ownerNode;
 
-  _NodeJs get ownerNode() native "return this.ownerNode;";
+  final _StyleSheetJs parentStyleSheet;
 
-  _StyleSheetJs get parentStyleSheet() native "return this.parentStyleSheet;";
+  final String title;
 
-  String get title() native "return this.title;";
-
-  String get type() native "return this.type;";
+  final String type;
 }