Update dart2js unit tests to dart_parser and dart_scanner.

tests/compiler/dart2js/diagnostic_reporter_helper.dart

Index: tests/compiler/dart2js/diagnostic_reporter_helper.dart
diff --git a/tests/compiler/dart2js/diagnostic_reporter_helper.dart b/tests/compiler/dart2js/diagnostic_reporter_helper.dart
index 679ef8c7eeb9d187c9f2011be6e6c33137de52e9..a7c497f133603dbf0154e4e09aab9f1cbd2654b6 100644
--- a/tests/compiler/dart2js/diagnostic_reporter_helper.dart
+++ b/tests/compiler/dart2js/diagnostic_reporter_helper.dart
@@ -6,9 +6,10 @@ library dart2js.diagnostic_reporter.helper;
 
 import 'package:compiler/src/diagnostics/diagnostic_listener.dart';
 import 'package:compiler/src/diagnostics/messages.dart';
-import 'package:compiler/src/diagnostics/spannable.dart';
 import 'package:compiler/src/diagnostics/source_span.dart';
+import 'package:compiler/src/diagnostics/spannable.dart';
 import 'package:compiler/src/elements/elements.dart';
+import 'package:dart_scanner/dart_scanner.dart';
 import 'options_helper.dart';
 
 abstract class DiagnosticReporterWrapper extends DiagnosticReporter {
@@ -63,6 +64,9 @@ abstract class DiagnosticReporterWrapper extends DiagnosticReporter {
   }
 
   @override
+  SourceSpan spanFromToken(Token token) => reporter.spanFromToken(token);
+
+  @override
   withCurrentElement(Element element, f()) {
     return reporter.withCurrentElement(element, f);
   }