Make VM event streams look like real dart streams.

runtime/observatory/tests/service/pause_on_exceptions_test.dart

 // Copyright (c) 2015, 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.
 // VMOptions=--compile_all --error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 import 'dart:async';
 import 'dart:developer';
@@ skipping 16 matching lines @@
 }
 
 var tests = [
 
 (Isolate isolate) async {
   var lib = await isolate.rootLibrary.reload();
 
   var onPaused = null;
   var onResume = null;
 
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     print("Event $event");
     if (event.kind == ServiceEvent.kPauseException) {
       if (onPaused == null) throw "Unexpected pause event $event";
       var t = onPaused;
       onPaused = null;
       t.complete(event);
     }
     if (event.kind == ServiceEvent.kResume) {
       if (onResume == null) throw "Unexpected resume event $event";
       var t = onResume;
@@ skipping 53 matching lines @@
 
   await test("none", "doCaught()", false, true);
   await test("none", "doUncaught()", false, false);
 
   subscription.cancel();
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests);