Make VM event streams look like real dart streams.

runtime/observatory/tests/service/debugging_test.dart

Index: runtime/observatory/tests/service/debugging_test.dart
diff --git a/runtime/observatory/tests/service/debugging_test.dart b/runtime/observatory/tests/service/debugging_test.dart
index e9e2c119343e44152882febd46ea6641fbef7627..d34a86dd8e59b91865b7eaab48f3bf513e9350f5 100644
--- a/runtime/observatory/tests/service/debugging_test.dart
+++ b/runtime/observatory/tests/service/debugging_test.dart
@@ -28,8 +28,9 @@ var tests = [
 // Pause
 (Isolate isolate) async {
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kPauseInterrupted) {
       subscription.cancel();
       completer.complete();
@@ -42,8 +43,9 @@ var tests = [
 // Resume
 (Isolate isolate) async {
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kResume) {
       subscription.cancel();
       completer.complete();
@@ -59,8 +61,9 @@ var tests = [
 
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   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();
@@ -98,8 +101,9 @@ var tests = [
 (Isolate isolate) async {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   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();
@@ -126,8 +130,9 @@ var tests = [
 (Isolate isolate) async {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   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));
@@ -145,8 +150,9 @@ var tests = [
 // Resume
 (Isolate isolate) async {
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   var subscription;
-  subscription = isolate.vm.events.stream.listen((ServiceEvent event) {
+  subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kResume) {
       subscription.cancel();
       completer.complete();
@@ -160,8 +166,9 @@ var tests = [
 (Isolate isolate) async {
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
+  var stream = await isolate.vm.getDebugEventStream();
   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();