Use packages dart_parser, dart_scanner, and compiler_util.

pkg/dart_scanner/lib/dart_scanner.dart

 // Copyright (c) 2016, 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.md file.
 
 library dart_scanner;
 
 import 'src/token.dart' show
     Token;
 
 import 'src/utf8_bytes_scanner.dart' show
     Utf8BytesScanner;
 
+export 'src/token.dart' show
+    BeginGroupToken,
+    ErrorToken,
+    KeywordToken,
+    StringToken,
+    SymbolToken,
+    Token,
+    isBinaryOperator,
+    isMinusOperator,
+    isTernaryOperator,
+    isUnaryOperator,
+    isUserDefinableOperator;
+
+export 'src/token_constants.dart' show
+    EOF_TOKEN;
+
+export 'src/utf8_bytes_scanner.dart' show
+    Utf8BytesScanner;
+
+export 'src/string_scanner.dart' show
+    StringScanner;
+
+export 'src/keyword.dart' show
+    Keyword;
+
 abstract class Scanner {
   List<int> get lineStarts;
   Token tokenize();
 }
 
 class ScannerResult {
   final Token tokens;
   final List<int> lineStarts;
 
   ScannerResult(this.tokens, this.lineStarts);
 }
 
 ScannerResult scan(List<int> bytes, {bool includeComments: false}) {
   if (bytes.last != 0) {
     throw new ArgumentError("[bytes]: the last byte must be null.");
   }
   Scanner scanner =
       new Utf8BytesScanner(bytes, includeComments: includeComments);
   return new ScannerResult(scanner.tokenize(), scanner.lineStarts);
 }