Use packages dart_parser, dart_scanner, and compiler_util.

pkg/compiler/lib/src/util/util.dart

Index: pkg/compiler/lib/src/util/util.dart
diff --git a/pkg/compiler/lib/src/util/util.dart b/pkg/compiler/lib/src/util/util.dart
index dbcc7d3a432f5baefd5941f2667ab290345232e8..8a394a5691fce547ee6a86e4fcbd5117c5303371 100644
--- a/pkg/compiler/lib/src/util/util.dart
+++ b/pkg/compiler/lib/src/util/util.dart
@@ -4,15 +4,15 @@
 
 library dart2js.util;
 
-import 'characters.dart';
-import 'util_implementation.dart';
+import 'package:dart_scanner/src/characters.dart';
+import 'package:compiler_util/link.dart';
 
 export 'emptyset.dart';
 export 'maplet.dart';
 export 'setlet.dart';
+export 'package:compiler_util/link.dart';
 
 part 'indentation.dart';
-part 'link.dart';
 
 /// Helper functions for creating hash codes.
 class Hashing {