dart2Js: bailout early when using the new emitter with mirrors.

pkg/compiler/lib/src/warnings.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.
 
 part of dart2js;
 
 const DONT_KNOW_HOW_TO_FIX = "Computer says no!";
 
 /**
  * The messages in this file should meet the following guide lines:
@@ skipping 2364 matching lines @@
 $IMPORT_EXPERIMENTAL_MIRRORS_PADDING#{importChain}
 *
 * You can disable this message by using the --enable-experimental-mirrors
 * command-line flag.
 *
 * To learn what to do next, please visit:
 *    http://dartlang.org/dart2js-reflection
 ****************************************************************
 ''');
 
+
+  static const MessageKind MIRRORS_LIBRARY_NEW_EMITTER =
+      const MessageKind(
+          "dart:mirrors library is not supported when using the new emitter "
+            "(DART_VM_OPTIONS='-Ddart2js.use.new.emitter=true')");
+
   static const MessageKind CALL_NOT_SUPPORTED_ON_NATIVE_CLASS =
       const MessageKind(
           "Non-supported 'call' member on a native class, or a "
           "subclass of a native class.");
 
   toString() => template;
 
   Message message([Map arguments = const {}, bool terse = false]) {
     return new Message(this, arguments, terse);
   }
@@ skipping 47 matching lines @@
   static String convertToString(value) {
     if (value is ErrorToken) {
       // Shouldn't happen.
       return value.assertionMessage;
     } else if (value is Token) {
       value = value.value;
     }
     return '$value';
   }
 }