rename fasta.Token.value --> lexeme

pkg/compiler/lib/src/diagnostics/messages.dart

 // Copyright (c) 2011, 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.
 
 /// The messages in this file should follow the [Guide for Writing
 /// Diagnostics](../../../../front_end/lib/src/fasta/diagnostics.md).
 ///
 /// Other things to keep in mind:
 ///
 /// An INFO message should always be preceded by a non-INFO message, and the
@@ skipping 3754 matching lines @@
     return (template == other.template) && (toString() == other.toString());
   }
 
   int get hashCode => throw new UnsupportedError('Message.hashCode');
 
   static String convertToString(value) {
     if (value is ErrorToken) {
       // Shouldn't happen.
       return value.assertionMessage;
     } else if (value is Token) {
-      value = value.value;
+      value = value.lexeme;
     }
     return '$value';
   }
 }