Add 'part of' in dart2js code.

lib/compiler/implementation/scanner/partial_parser.dart

Index: lib/compiler/implementation/scanner/partial_parser.dart
diff --git a/lib/compiler/implementation/scanner/partial_parser.dart b/lib/compiler/implementation/scanner/partial_parser.dart
index fe2bcd7db71cf452b9b17ea7880287d2807a8584..7516e6ca517aa03c634ea858be870f7dc4e8271a 100644
--- a/lib/compiler/implementation/scanner/partial_parser.dart
+++ b/lib/compiler/implementation/scanner/partial_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 PartialParser extends Parser {
   PartialParser(Listener listener) : super(listener);