Add related types check to analyze_dart2js_test

tests/compiler/dart2js/memory_compiler.dart

 // Copyright (c) 2013, 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.test.memory_compiler;
 
 import 'dart:async';
 
 import 'package:compiler/compiler.dart' show
     DiagnosticHandler;
@@ skipping 63 matching lines @@
   }
 
   Iterable<DiagnosticMessage> get infos {
     return filterMessagesByKinds([Diagnostic.INFO]);
   }
 
   /// `true` if non-verbose messages has been collected.
   bool get hasRegularMessages {
     return messages.any((m) => m.kind != Diagnostic.VERBOSE_INFO);
   }
+
+  void clear() {
+    messages.clear();
+  }
 }
 
 class MultiDiagnostics implements CompilerDiagnostics {
   final List<CompilerDiagnostics> diagnosticsList;
 
   const MultiDiagnostics([this.diagnosticsList = const []]);
 
   @override
   void report(Message message, Uri uri, int begin, int end,
               String text, Diagnostic kind) {
@@ skipping 233 matching lines @@
       createDiagnosticHandler(diagnosticHandler, provider, showDiagnostics);
 
   List<Uri> libraries = <Uri>[];
   memorySourceFiles.forEach((String path, _) {
     libraries.add(new Uri(scheme: 'memory', path: path));
   });
 
   return analyze(libraries, libraryRoot, packageRoot,
                  provider, handler, options);
 }