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

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

Index: client/dom/generated/src/frog/DOMSelection.dart
diff --git a/client/dom/generated/src/frog/DOMSelection.dart b/client/dom/generated/src/frog/DOMSelection.dart
index 3fbdaeadf9f8982eeed9cc4fd52438bfa9c8fd77..b90e0baf237230c7f520fe56403bc05cffbe9aa5 100644
--- a/client/dom/generated/src/frog/DOMSelection.dart
+++ b/client/dom/generated/src/frog/DOMSelection.dart
@@ -1,27 +1,27 @@
 
 class _DOMSelectionJs extends _DOMTypeJs implements DOMSelection native "*DOMSelection" {
 
-  _NodeJs get anchorNode() native "return this.anchorNode;";
+  final _NodeJs anchorNode;
 
-  int get anchorOffset() native "return this.anchorOffset;";
+  final int anchorOffset;
 
-  _NodeJs get baseNode() native "return this.baseNode;";
+  final _NodeJs baseNode;
 
-  int get baseOffset() native "return this.baseOffset;";
+  final int baseOffset;
 
-  _NodeJs get extentNode() native "return this.extentNode;";
+  final _NodeJs extentNode;
 
-  int get extentOffset() native "return this.extentOffset;";
+  final int extentOffset;
 
-  _NodeJs get focusNode() native "return this.focusNode;";
+  final _NodeJs focusNode;
 
-  int get focusOffset() native "return this.focusOffset;";
+  final int focusOffset;
 
-  bool get isCollapsed() native "return this.isCollapsed;";
+  final bool isCollapsed;
 
-  int get rangeCount() native "return this.rangeCount;";
+  final int rangeCount;
 
-  String get type() native "return this.type;";
+  final String type;
 
   void addRange(_RangeJs range) native;