Add 'part of' in dart2js code.

lib/compiler/implementation/scanner/class_element_parser.dart

 // Copyright (c) 2011, 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 scanner;
+
 class ClassElementParser extends PartialParser {
   ClassElementParser(Listener listener) : super(listener);
 
   Token parseClassBody(Token token) => fullParseClassBody(token);
 }
 
 class PartialClassElement extends ClassElement {
   final Token beginToken;
   final Token endToken;
   ClassNode cachedNode;
@@ skipping 154 matching lines @@
   }
 
   void addMember(Element memberElement) {
     for (Link link = metadata; !link.isEmpty; link = link.tail) {
       memberElement.addMetadata(link.head);
     }
     metadata = const Link<MetadataAnnotation>();
     enclosingElement.addMember(memberElement, listener);
   }
 }