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

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

 
 class _XPathResultJs extends _DOMTypeJs implements XPathResult native "*XPathResult" {
 
   static final int ANY_TYPE = 0;
 
   static final int ANY_UNORDERED_NODE_TYPE = 8;
 
   static final int BOOLEAN_TYPE = 3;
 
   static final int FIRST_ORDERED_NODE_TYPE = 9;
 
   static final int NUMBER_TYPE = 1;
 
   static final int ORDERED_NODE_ITERATOR_TYPE = 5;
 
   static final int ORDERED_NODE_SNAPSHOT_TYPE = 7;
 
   static final int STRING_TYPE = 2;
 
   static final int UNORDERED_NODE_ITERATOR_TYPE = 4;
 
   static final int UNORDERED_NODE_SNAPSHOT_TYPE = 6;
 
-  bool get booleanValue() native "return this.booleanValue;";
+  final bool booleanValue;
 
-  bool get invalidIteratorState() native "return this.invalidIteratorState;";
+  final bool invalidIteratorState;
 
-  num get numberValue() native "return this.numberValue;";
+  final num numberValue;
 
-  int get resultType() native "return this.resultType;";
+  final int resultType;
 
-  _NodeJs get singleNodeValue() native "return this.singleNodeValue;";
+  final _NodeJs singleNodeValue;
 
-  int get snapshotLength() native "return this.snapshotLength;";
+  final int snapshotLength;
 
-  String get stringValue() native "return this.stringValue;";
+  final String stringValue;
 
   _NodeJs iterateNext() native;
 
   _NodeJs snapshotItem(int index) native;
 }