Use @Native annotation on dart2js DOM native classes

tools/dom/templates/html/impl/impl_AudioContext.darttemplate

 // 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 web_audio;
 
-$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
+$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 $!MEMBERS
 $if DART2JS
   factory AudioContext() => JS('AudioContext',
       'new (window.AudioContext || window.webkitAudioContext)()');
 
   GainNode createGain() {
     if (JS('bool', '#.createGain !== undefined', this)) {
       return JS('GainNode', '#.createGain()', this);
     } else {
       return JS('GainNode', '#.createGainNode()', this);
@@ skipping 24 matching lines @@
         (error) {
           if (error == null) {
             completer.completeError('');
           } else {
             completer.completeError(error);
           }
         });
     return completer.future;
   }
 }