Repeats and fixes the changes landed & reverted as CL 1789553003.

tests/compiler/dart2js/diagnostic_reporter_helper.dart

 // Copyright (c) 2015, 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.
 
 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/elements/elements.dart';
+import 'options_helper.dart';
 
 abstract class DiagnosticReporterWrapper extends DiagnosticReporter {
   DiagnosticReporter get reporter;
 
   @override
   DiagnosticMessage createMessage(
       Spannable spannable,
       MessageKind messageKind,
       [Map arguments = const {}]) {
     return reporter.createMessage(spannable, messageKind, arguments);
@@ skipping 44 matching lines @@
   @override
   SourceSpan spanFromSpannable(Spannable node) {
     return reporter.spanFromSpannable(node);
   }
 
   @override
   withCurrentElement(Element element, f()) {
     return reporter.withCurrentElement(element, f);
   }
 }