Make Dart2js implement the onExit/onError/errorsAreFatal parameters to spawnUri.

sdk/lib/isolate/isolate.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.
 
 /**
  * Concurrent programming using _isolates_:
  * independent workers that are similar to threads
  * but don't share memory,
  * communicating only via messages.
  */
@@ skipping 139 matching lines @@
    * the isolate will act as if, respectively, [setErrorsFatal],
    * [addOnExitListener] and [addErrorListener] were called with the
    * corresponding parameter and was processed before the isolate starts
    * running.
    *
    * You can also call the [setErrorsFatal], [addOnExitListener] and
    * [addErrorListener] methods on the returned isolate, but unless the
    * isolate was started as [paused], it may already have terminated
    * before those methods can complete.
    *
-   * WARNING: The [errorsAreFatal], [onExit] and [onError] parameters are not
-   * implemented yet.
-   *
    * Returns a future that will complete with an [Isolate] instance if the
    * spawning succeeded. It will complete with an error otherwise.
    */
   external static Future<Isolate> spawn(void entryPoint(message), var message,
                                         { bool paused: false,
                                           bool errorsAreFatal,
                                           SendPort onExit,
                                           SendPort onError });
 
   /**
@@ skipping 465 matching lines @@
  * as the original error, but has no other features of the original error.
  */
 class RemoteError implements Error {
   final String _description;
   final StackTrace stackTrace;
   RemoteError(String description, String stackDescription)
       : _description = description,
         stackTrace = new StackTrace.fromString(stackDescription);
   String toString() => _description;
 }