Detect asynchronous dart2js crashes correctly.

sdk/lib/_internal/compiler/implementation/dart2js.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.cmdline;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:math' as math;
 
@@ skipping 544 matching lines @@
   exit(0);
 }
 
 void helpAndFail(String message) {
   help();
   print('');
   fail(message);
 }
 
 void mainWithErrorHandler(Options options) {
-  new Future.sync(() => compilerMain(options)).catchError((exception) {
+  runZonedExperimental(() => compilerMain(options), onError: (exception) {
     try {
       print('Internal error: $exception');
     } catch (ignored) {
       print('Internal error: error while printing exception');
     }
 
     try {
       var trace = getAttachedStackTrace(exception);
       if (trace != null) {
         print(trace);
       }
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   });
 }
 
 void main() {
   mainWithErrorHandler(new Options());
 }