Use packages dart_parser, dart_scanner, and compiler_util.

pkg/compiler/lib/src/string_validator.dart

Index: pkg/compiler/lib/src/string_validator.dart
diff --git a/pkg/compiler/lib/src/string_validator.dart b/pkg/compiler/lib/src/string_validator.dart
index b81661a9415f7edd310d153b8e3b356ed39d4a11..900e2b50c1be9141e86a09ea4705c1df81becc7a 100644
--- a/pkg/compiler/lib/src/string_validator.dart
+++ b/pkg/compiler/lib/src/string_validator.dart
@@ -9,10 +9,10 @@ library stringvalidator;
 import 'dart:collection';
 
 import 'common.dart';
-import 'tokens/token.dart' show Token;
+import 'package:dart_scanner/dart_scanner.dart' show Token;
 import 'tree/dartstring.dart' show DartString;
 import 'tree/nodes.dart' show StringQuoting;
-import 'util/characters.dart';
+import 'package:dart_scanner/src/characters.dart';
 
 class StringValidator {
   final DiagnosticReporter reporter;
@@ -100,7 +100,8 @@ class StringValidator {
 
   void stringParseError(String message, Token token, int offset) {
     reporter.reportErrorMessage(
-        token, MessageKind.GENERIC, {'text': "$message @ $offset"});
+        reporter.spanFromToken(token), MessageKind.GENERIC,
+        {'text': "$message @ $offset"});
   }
 
   /**