Add 'part of' in dart2js code.

lib/compiler/implementation/ssa/value_set.dart

 // Copyright (c) 2012, 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 ssa;
+
 class ValueSet {
   int size = 0;
   List<HInstruction> table;
   ValueSetNode collisions;
   ValueSet() : table = new List<HInstruction>(8);
 
   bool get isEmpty => size == 0;
   int get length => size;
 
   void add(HInstruction instruction) {
@@ skipping 131 matching lines @@
   }
 }
 
 class ValueSetNode {
   final HInstruction value;
   final int hash;
   int get hashCode => hash;
   ValueSetNode next;
   ValueSetNode(this.value, this.hash, this.next);
 }