Use @Native annotation on dart2js DOM native classes

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

 // Copyright (c) 2014, 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;
 
 @DocsEditable()
-$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
+$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 
   @DomName('FileReader.result')
   @DocsEditable()
   Object get result {
 $if DART2JS
     var res = JS('Null|String|NativeByteBuffer', '#.result', this);
 $else
     var res = _blink.BlinkFileReader.$result_Getter(this);
 $endif
     if (res is ByteBuffer) {
       return new Uint8List.view(res);
     }
     return res;
   }
 
 $!MEMBERS
 }