Changes to make compiler_util a standalone package.

pkg/compiler_util/lib/link.dart

Index: pkg/compiler_util/lib/link.dart
diff --git a/pkg/compiler_util/lib/link.dart b/pkg/compiler_util/lib/link.dart
index 58d2cb98cf09b71e3abc52de0d149b02ebbaa9cb..68baf5516731c894bf9930d39d070127984b1aa7 100644
--- a/pkg/compiler_util/lib/link.dart
+++ b/pkg/compiler_util/lib/link.dart
@@ -2,7 +2,13 @@
 // 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.util;
+library compiler_util.link;
+
+import 'src/link_implementation.dart' show
+    LinkBuilderImplementation,
+    LinkEntry,
+    LinkIterator,
+    MappedLinkIterable;
 
 class Link<T> implements Iterable<T> {
   T get head => throw new StateError("no elements");