Second version of support for specifying an unhandled exception callback

sdk/lib/isolate/base.dart

 // Copyright (c) 2012, 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.
 
 class IsolateSpawnException implements Exception {
   const IsolateSpawnException(String this._s);
   String toString() => "IsolateSpawnException: '$_s'";
   final String _s;
 }
 
@@ skipping 14 matching lines @@
  * When any isolate starts (even the main script of the application), a default
  * [ReceivePort] is created for it. This port is available from the top-level
  * getter [port] defined in this library.
  *
  * [spawnFunction] returns a [SendPort] derived from the child isolate's default
  * port.
  *
  * See comments at the top of this library for more details.
  */
 // Note this feature is not yet available in the dartvm.
-external SendPort spawnFunction(void topLevelFunction());
-
+external SendPort spawnFunction(void topLevelFunction(),
+    [bool UnhandledExceptionCallback(IsolateUnhandledException e)]);
 /**
  * Creates and spawns an isolate whose code is available at [uri].  Like with
  * [spawnFunction], the child isolate will have a default [ReceivePort], and a
  * this function returns a [SendPort] derived from it.
  *
  * See comments at the top of this library for more details.
  */
 external SendPort spawnUri(String uri);
 
 /**
@@ skipping 88 matching lines @@
   SendPort toSendPort();
 
 }
 
 // TODO(kasperl): Document this.
 abstract class SendPortSync {
 
   callSync(var message);
 
 }