Use @Native annotation on dart2js DOM native classes

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

 // 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.
 
 part of $LIBRARYNAME;
 
-$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
+$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 $!MEMBERS
 
   /**
    * Checks if the MediaStream APIs are supported on the current platform.
    *
    * See also:
    *
    * * [Navigator.getUserMedia]
    */
 $if DART2JS
   static bool get supported =>
     JS('bool', '''!!(#.getUserMedia || #.webkitGetUserMedia ||
         #.mozGetUserMedia || #.msGetUserMedia)''',
         window.navigator,
         window.navigator,
         window.navigator,
         window.navigator);
 $else
   static bool get supported => true;
 $endif
 }