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

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

 
 class _IDBDatabaseJs extends _DOMTypeJs implements IDBDatabase native "*IDBDatabase" {
 
-  String get name() native "return this.name;";
+  final String name;
 
-  EventListener get onabort() native "return this.onabort;";
+  EventListener onabort;
 
-  void set onabort(EventListener value) native "this.onabort = value;";
+  EventListener onerror;
 
-  EventListener get onerror() native "return this.onerror;";
+  EventListener onversionchange;
 
-  void set onerror(EventListener value) native "this.onerror = value;";
-
-  EventListener get onversionchange() native "return this.onversionchange;";
-
-  void set onversionchange(EventListener value) native "this.onversionchange = value;";
-
-  String get version() native "return this.version;";
+  final String version;
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   void close() native;
 
   _IDBObjectStoreJs createObjectStore(String name) native;
 
   void deleteObjectStore(String name) native;
 
   bool dispatchEvent(_EventJs evt) native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   _IDBVersionChangeRequestJs setVersion(String version) native;
 
   _IDBTransactionJs transaction(String storeName, int mode) native;
 }