Use FastaMessage instead of String. Part 1.

pkg/compiler/lib/src/tree/nodes.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:collection' show IterableMixin;
 
-import 'package:front_end/src/fasta/fasta_codes.dart' show FastaMessage;
+import 'package:front_end/src/fasta/fasta_codes.dart' show Message;
 import 'package:front_end/src/fasta/scanner.dart' show Token;
 import 'package:front_end/src/fasta/scanner/token_constants.dart' as Tokens
     show PLUS_TOKEN;
 import 'package:front_end/src/fasta/scanner/characters.dart';
 import 'package:front_end/src/scanner/token.dart' show BeginToken, TokenType;
 
 import '../common.dart';
 import '../elements/elements.dart' show MetadataAnnotation;
 import '../util/util.dart';
 import 'dartstring.dart';
@@ skipping 3152 matching lines @@
   bool visitStringJuxtaposition(StringJuxtaposition node) =>
       node.isInterpolation;
 }
 
 /// Erroneous node used to recover from parser errors.  Implements various
 /// interfaces and provides bare minimum of implementation to avoid unnecessary
 /// messages.
 class ErrorNode extends Node
     implements FunctionExpression, VariableDefinitions, Typedef {
   final Token token;
-  final FastaMessage message;
+  final Message message;
   final Identifier name;
   final NodeList definitions;
 
   ErrorNode.internal(this.token, this.message, this.name, this.definitions);
 
-  factory ErrorNode(Token token, FastaMessage message) {
+  factory ErrorNode(Token token, Message message) {
     Identifier name = new Identifier(token);
     NodeList definitions =
         new NodeList(null, const Link<Node>().prepend(name), null, null);
     return new ErrorNode.internal(token, message, name, definitions);
   }
 
   Token get beginToken => token;
   Token get endToken => token;
 
   Token getBeginToken() => token;
@@ skipping 86 matching lines @@
  */
 Object getTreeElement(TreeElementMixin node) => node._element;
 
 /**
  * Do not call this method directly.  Instead, use an instance of
  * TreeElements.
  */
 void setTreeElement(TreeElementMixin node, Object value) {
   node._element = value;
 }