Add 'part of' in dart2js code.

lib/compiler/implementation/scanner/class_element_parser.dart

Index: lib/compiler/implementation/scanner/class_element_parser.dart
diff --git a/lib/compiler/implementation/scanner/class_element_parser.dart b/lib/compiler/implementation/scanner/class_element_parser.dart
index f86720c6a4797233573f6f6ab96b802be667aa46..39e6d250bb2415aa771da5c06ff84fa0bc942b3b 100644
--- a/lib/compiler/implementation/scanner/class_element_parser.dart
+++ b/lib/compiler/implementation/scanner/class_element_parser.dart
@@ -2,6 +2,8 @@
 // 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);