Make VM event streams look like real dart streams.

runtime/observatory/tests/service/debugging_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';
 
@@ skipping 10 matching lines @@
 
 void startTimer() {
   new Timer.periodic(const Duration(milliseconds:10), periodicTask);
 }
 
 var tests = [
 
 // Pause
 (Isolate isolate) async {
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kPauseInterrupted) {
       subscription.cancel();
       completer.complete();
     }
   });
   isolate.pause();
   await completer.future;
 },
 
 // Resume
 (Isolate isolate) async {
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kResume) {
       subscription.cancel();
       completer.complete();
     }
   });
   isolate.resume();
   await completer.future;
 },
 
 // Add breakpoint
 (Isolate isolate) async {
   await isolate.rootLibrary.load();
 
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kPauseBreakpoint) {
       print('Breakpoint reached');
       subscription.cancel();
       completer.complete();
     }
   });
 
   var script = isolate.rootLibrary.scripts[0];
   await script.load();
 
@@ skipping 17 matching lines @@
 
   Script script = stack['frames'][0].location.script;
   expect(script.name,endsWith('debugging_test.dart'));
   expect(script.tokenToLine(stack['frames'][0].location.tokenPos), equals(15));
 },
 
 // Stepping
 (Isolate isolate) async {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kPauseBreakpoint) {
       print('Breakpoint reached');
       subscription.cancel();
       completer.complete();
     }
   });
 
   await isolate.stepOver();
   await completer.future;  // Wait for breakpoint events.
 },
 
 // We are now at line 16.
 (Isolate isolate) async {
   ServiceMap stack = await isolate.getStack();
   expect(stack.type, equals('Stack'));
   expect(stack['frames'].length, greaterThanOrEqualTo(1));
 
   Script script = stack['frames'][0].location.script;
   expect(script.name,endsWith('debugging_test.dart'));
   expect(script.tokenToLine(stack['frames'][0].location.tokenPos), equals(16));
 },
 
 // Remove breakpoint
 (Isolate isolate) async {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kBreakpointRemoved) {
       print('Breakpoint removed');
       expect(isolate.breakpoints.length, equals(0));
       subscription.cancel();
       completer.complete();
     }
   });
 
   expect(isolate.breakpoints.length, equals(1));
   var bpt = isolate.breakpoints.values.first;
   await isolate.removeBreakpoint(bpt);
   await completer.future;
 },
 
 // Resume
 (Isolate isolate) async {
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kResume) {
       subscription.cancel();
       completer.complete();
     }
   });
   isolate.resume();
   await completer.future;
 },
 
 // Add breakpoint at function entry
 (Isolate isolate) async {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getEventStream(VM.kDebugStream);
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kPauseBreakpoint) {
       print('Breakpoint reached');
       subscription.cancel();
       completer.complete();
     }
   });
 
   // Find a specific function.
   ServiceFunction function = isolate.rootLibrary.functions.firstWhere(
       (f) => f.name == 'periodicTask');
@@ skipping 18 matching lines @@
   expect(stack['frames'].length, greaterThanOrEqualTo(1));
 
   Script script = stack['frames'][0].location.script;
   expect(script.name,endsWith('debugging_test.dart'));
   expect(script.tokenToLine(stack['frames'][0].location.tokenPos), equals(14));
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: startTimer);