dom: more final more of the time

tools/dom/src/dart2js_DOMImplementation.dart

 // Copyright (c) 2012, 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.
 
 part of html;
 
 // TODO(vsm): Unify with Dartium version.
 class _DOMWindowCrossFrame implements WindowBase {
   // Private window.  Note, this is a window in another frame, so it
   // cannot be typed as "Window" as its prototype is not patched
   // properly.  Its fields and methods can only be accessed via JavaScript.
-  var _window;
+  final _window;
 
   // Fields.
   HistoryBase get history =>
     _HistoryCrossFrame._createSafe(JS('HistoryBase', '#.history', _window));
   LocationBase get location =>
     _LocationCrossFrame._createSafe(JS('LocationBase', '#.location', _window));
 
   // TODO(vsm): Add frames to navigate subframes.  See 2312.
 
   bool get closed => JS('bool', '#.closed', _window);
@@ skipping 69 matching lines @@
 
   static HistoryBase _createSafe(h) {
     if (identical(h, window.history)) {
       return h;
     } else {
       // TODO(vsm): Cache or implement equality.
       return new _HistoryCrossFrame(h);
     }
   }
 }