Extract DiagnosticReporter implementation from Compiler.

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';
+
+abstract class DiagnosticReporterWrapper extends DiagnosticReporter {
+  DiagnosticReporter get reporter;
+
+  @override
+  DiagnosticMessage createMessage(
+      Spannable spannable,
+      MessageKind messageKind,
+      [Map arguments = const {}]) {
+    return reporter.createMessage(spannable, messageKind, arguments);
+  }
+
+  @override
+  internalError(Spannable spannable, message) {
+    return reporter.internalError(spannable, message);
+  }
+
+  @override
+  void log(message) {
+    return reporter.log(message);
+  }
+
+  @override
+  DiagnosticOptions get options => reporter.options;
+
+  @override
+  void reportError(
+      DiagnosticMessage message,
+      [List<DiagnosticMessage> infos = const <DiagnosticMessage> []]) {
+    reporter.reportError(message, infos);
+  }
+
+  @override
+  void reportHint(
+      DiagnosticMessage message,
+      [List<DiagnosticMessage> infos = const <DiagnosticMessage> []]) {
+    reporter.reportHint(message, infos);
+  }
+
+  @override
+  void reportInfo(
+      Spannable node,
+      MessageKind errorCode,
+      [Map arguments = const {}]) {
+    reporter.reportInfo(node, errorCode, arguments);
+  }
+
+  @override
+  void reportWarning(
+      DiagnosticMessage message,
+      [List<DiagnosticMessage> infos = const <DiagnosticMessage> []]) {
+    reporter.reportWarning(message, infos);
+  }
+
+  @override
+  SourceSpan spanFromSpannable(Spannable node) {
+    return reporter.spanFromSpannable(node);
+  }
+
+  @override
+  withCurrentElement(Element element, f()) {
+    return reporter.withCurrentElement(element, f);
+  }
+}