Fix dart2js-with-kernel test crashes

pkg/compiler/lib/src/kernel/element_map_mixins.dart

 // Copyright (c) 2017, 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.
 
 import 'package:js_runtime/shared/embedded_names.dart';
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../constants/constructors.dart';
@@ skipping 124 matching lines @@
       type ??= findIn(Uris.dart_collection);
       type ??= findIn(Uris.dart_math);
       type ??= findIn(Uris.dart_html);
       type ??= findIn(Uris.dart_html_common);
       type ??= findIn(Uris.dart_svg);
       type ??= findIn(Uris.dart_web_audio);
       type ??= findIn(Uris.dart_web_gl);
       type ??= findIn(Uris.dart_web_sql);
       type ??= findIn(Uris.dart_indexed_db);
       type ??= findIn(Uris.dart_typed_data);
+      type ??= findIn(Uris.dart_mirrors);
       if (type == null && required) {
         reporter.reportErrorMessage(CURRENT_ELEMENT_SPANNABLE,
             MessageKind.GENERIC, {'text': "Type '$typeName' not found."});
       }
       return type;
     }
 
     return lookup;
   }
 
@@ skipping 687 matching lines @@
     }
     if (isRedirecting) {
       return new RedirectingGenerativeConstantConstructor(
           defaultValues, superConstructorInvocation);
     } else {
       return new GenerativeConstantConstructor(
           type, defaultValues, fieldMap, superConstructorInvocation);
     }
   }
 }