Add 'part of' in dart2js code.

lib/compiler/implementation/compile_time_constants.dart

Index: lib/compiler/implementation/compile_time_constants.dart
diff --git a/lib/compiler/implementation/compile_time_constants.dart b/lib/compiler/implementation/compile_time_constants.dart
index 0a3eea61b699664af32b3b96c767e1fd55027594..f54e349ddbb39e66d7600b35b751ae762a37a1e1 100644
--- a/lib/compiler/implementation/compile_time_constants.dart
+++ b/lib/compiler/implementation/compile_time_constants.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 dart2js;
+
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of