Fixing dartc error about not using ~/ operator and FF test error.

tests/html/wheelevent_test.dart

 // Copyright (c) 2013, 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.
 
 library wheel_event_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 
 main() {
 
   useHtmlConfiguration();
 
   var userAgent = window.navigator.userAgent;
 
   // Lame platform-dependent check to validate that our assumptions about
   // which event is being used is correct.
   var wheelEvent = 'wheel';
   if (userAgent.contains("Opera", 0)) {
     wheelEvent = 'mousewheel';
   } else if (userAgent.contains("MSIE", 0)) {
     wheelEvent = 'mousewheel';
   } else if (userAgent.contains('Firefox')) {
     // FF appears to have recently added support for wheel.
-    if (userAgent.contains('Firefox/17')) {
-      wheelEvent = 'DOMMouseScroll';
-    } else {
-      wheelEvent = 'wheel';
-    }
+    wheelEvent = 'wheel';
   } else if (userAgent.contains('WebKit', 0)) {
     wheelEvent = 'mousewheel';
   }
 
   test('wheelEvent', () {
     var element = new DivElement();
     element.on.mouseWheel.add(expectAsync1((e) {
       expect(e.screenX, 100);
       expect(e.deltaX, 0);
       expect(e.deltaY, 240);
@@ skipping 24 matching lines @@
       240,
       0,
       100,
       200,
       10,
       20,
       0);
     element.$dom_dispatchEvent(event);
   });
 }