Use packages dart_parser, dart_scanner, and compiler_util.

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

Index: pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
diff --git a/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart b/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
index e12c09c824f73d04916ef5e165e77c79c99d11b9..52dee7c75b5fc37aceff33d9e0c754edaabd759d 100644
--- a/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
+++ b/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
@@ -4,6 +4,7 @@
 
 library dart2js.diagnostic_listener;
 
+import 'package:dart_scanner/dart_scanner.dart' show Token;
 import '../elements/elements.dart' show Element;
 import '../options.dart' show DiagnosticOptions;
 import 'messages.dart';
@@ -21,11 +22,16 @@ abstract class DiagnosticReporter {
 
   /// Creates a [SourceSpan] for [node] in scope of the current element.
   ///
-  /// If [node] is a [Node] or [Token] we assert in checked mode that the
-  /// corresponding tokens can be found within the tokens of the current
-  /// element.
+  /// If [node] is a [Node] we assert in checked mode that the corresponding
+  /// tokens can be found within the tokens of the current element.
   SourceSpan spanFromSpannable(Spannable node);
 
+  /// Creates a [SourceSpan] for [token] in scope of the current element.
+  ///
+  /// In checked mode we assert that the token can be found within the tokens
+  /// of the current element.
+  SourceSpan spanFromToken(Token token);
+
   void reportErrorMessage(Spannable spannable, MessageKind messageKind,
       [Map arguments = const {}]) {
     reportError(createMessage(spannable, messageKind, arguments));