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

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

 
 class _XMLHttpRequestJs extends _DOMTypeJs implements XMLHttpRequest native "*XMLHttpRequest" {
   XMLHttpRequest() native;
 
 
   static final int DONE = 4;
 
   static final int HEADERS_RECEIVED = 2;
 
   static final int LOADING = 3;
 
   static final int OPENED = 1;
 
   static final int UNSENT = 0;
 
-  bool get asBlob() native "return this.asBlob;";
+  bool asBlob;
 
-  void set asBlob(bool value) native "this.asBlob = value;";
+  final int readyState;
 
-  int get readyState() native "return this.readyState;";
+  final Object response;
 
-  Object get response() native "return this.response;";
+  final _BlobJs responseBlob;
 
-  _BlobJs get responseBlob() native "return this.responseBlob;";
+  final String responseText;
 
-  String get responseText() native "return this.responseText;";
+  String responseType;
 
-  String get responseType() native "return this.responseType;";
+  final _DocumentJs responseXML;
 
-  void set responseType(String value) native "this.responseType = value;";
+  final int status;
 
-  _DocumentJs get responseXML() native "return this.responseXML;";
+  final String statusText;
 
-  int get status() native "return this.status;";
+  final _XMLHttpRequestUploadJs upload;
 
-  String get statusText() native "return this.statusText;";
-
-  _XMLHttpRequestUploadJs get upload() native "return this.upload;";
-
-  bool get withCredentials() native "return this.withCredentials;";
-
-  void set withCredentials(bool value) native "this.withCredentials = value;";
+  bool withCredentials;
 
   void abort() native;
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   bool dispatchEvent(_EventJs evt) native;
 
   String getAllResponseHeaders() native;
 
   String getResponseHeader(String header) native;
 
   void open(String method, String url, [bool async = null, String user = null, String password = null]) native;
 
   void overrideMimeType(String override) native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   void send([var data = null]) native;
 
   void setRequestHeader(String header, String value) native;
 }