Add 'part of' in dart2js code.

lib/compiler/implementation/universe/selector_map.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 universe;
+
 class SelectorMap<T> extends PartialTypeTree {
 
   SelectorMap(Compiler compiler) : super(compiler);
 
   SelectorMapNode<T> newSpecializedNode(ClassElement type)
       => new SelectorMapNode<T>(type);
 
   T operator [](Selector selector) {
     SelectorMapNode<T> node = findNode(selectorType(selector), false);
     if (node == null) return null;
@@ skipping 106 matching lines @@
       selectorsByName = new Map<SourceString, Link<SelectorValue<T>>>();
 
 }
 
 class SelectorValue<T> {
   final Selector selector;
   T value;
   SelectorValue(this.selector, this.value);
   toString() => "$selector -> $value";
 }