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

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

 
 class _IDBTransactionJs extends _DOMTypeJs implements IDBTransaction native "*IDBTransaction" {
 
   static final int READ_ONLY = 0;
 
   static final int READ_WRITE = 1;
 
   static final int VERSION_CHANGE = 2;
 
-  _IDBDatabaseJs get db() native "return this.db;";
+  final _IDBDatabaseJs db;
 
-  int get mode() native "return this.mode;";
+  final int mode;
 
-  EventListener get onabort() native "return this.onabort;";
+  EventListener onabort;
 
-  void set onabort(EventListener value) native "this.onabort = value;";
+  EventListener oncomplete;
 
-  EventListener get oncomplete() native "return this.oncomplete;";
-
-  void set oncomplete(EventListener value) native "this.oncomplete = value;";
-
-  EventListener get onerror() native "return this.onerror;";
-
-  void set onerror(EventListener value) native "this.onerror = value;";
+  EventListener onerror;
 
   void abort() native;
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   bool dispatchEvent(_EventJs evt) native;
 
   _IDBObjectStoreJs objectStore(String name) native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 }