Use 'field' syntax in dart:dom interfaces.

client/dom/generated/src/interface/SVGAnimationElement.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // WARNING: Do not edit - generated code.
 
 interface SVGAnimationElement extends SVGElement, SVGTests, SVGExternalResourcesRequired, ElementTimeControl {
 
-  SVGElement get targetElement();
+  final SVGElement targetElement;
 
   num getCurrentTime();
 
   num getSimpleDuration();
 
   num getStartTime();
 }