Use packages dart_parser, dart_scanner, and compiler_util.

pkg/compiler/lib/src/io/start_end_information.dart

 // Copyright (c) 2015, 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.
 
 /// Source information system that maps spans of Dart AST nodes to spans of
 /// JavaScript nodes.
 
 library dart2js.source_information.start_end;
 
 import '../common.dart';
 import '../diagnostics/messages.dart' show MessageTemplate;
 import '../elements/elements.dart' show ResolvedAst, ResolvedAstKind;
 import '../js/js.dart' as js;
 import '../js/js_source_mapping.dart';
-import '../tokens/token.dart' show Token;
+import 'package:dart_scanner/dart_scanner.dart' show Token;
 import '../tree/tree.dart' show Node;
 import 'source_file.dart';
 import 'source_information.dart';
 
 /// Source information that contains start source position and optionally an
 /// end source position.
 class StartEndSourceInformation extends SourceInformation {
   @override
   final SourceLocation startPosition;
 
@@ skipping 187 matching lines @@
 
   @override
   SourceInformation buildIf(Node node) => buildGeneric(node);
 
   @override
   SourceInformationBuilder forContext(ResolvedAst resolvedAst,
       {SourceInformation sourceInformation}) {
     return new StartEndSourceInformationBuilder(resolvedAst);
   }
 }