Handle js interop members in impact computation.

pkg/compiler/lib/src/diagnostics/messages.dart

 // Copyright (c) 2011, 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.
 
 /// The messages in this file should follow the [Guide for Writing
 /// Diagnostics](../../../../front_end/lib/src/fasta/diagnostics.md).
 ///
 /// Other things to keep in mind:
 ///
 /// An INFO message should always be preceded by a non-INFO message, and the
@@ skipping 2385 matching lines @@
         main() {
           new Foo()[0] = 1;
         }
         """
           ]),
 
       MessageKind.JS_OBJECT_LITERAL_CONSTRUCTOR_WITH_POSITIONAL_ARGUMENTS:
           const MessageTemplate(
               MessageKind
                   .JS_OBJECT_LITERAL_CONSTRUCTOR_WITH_POSITIONAL_ARGUMENTS,
-              "Parameter '#{parameter}' in anonymous js-interop class '#{cls}' "
-              "object literal constructor is positional instead of named."
+              "Some parameters in anonymous js-interop class '#{cls}' "
+              "object literal constructor are positional instead of named."
               ".",
               howToFix: "Make all arguments in external factory object literal "
                   "constructors named.",
               examples: const [
             """
               import 'package:js/js.dart';
 
               @anonymous
               @JS()
               class Foo {
@@ skipping 1380 matching lines @@
   static String convertToString(value) {
     if (value is ErrorToken) {
       // Shouldn't happen.
       return value.assertionMessage;
     } else if (value is Token) {
       value = value.lexeme;
     }
     return '$value';
   }
 }