Refactor isolate interrupts to use OOB messages instead of interrupt bits.

runtime/observatory/tests/service/pause_idle_isolate_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=--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:io';
+import 'dart:isolate';
+
+var receivePort;
 
 void testMain() {
-  print('Hello');
+  receivePort = new ReceivePort();
 }
 
 var tests = [
 
 (Isolate isolate) async {
-  print('Getting stream...');
   Completer completer = new Completer();
   var stream = await isolate.vm.getEventStream(VM.kDebugStream);
-  print('Subscribing...');
   var subscription;
   subscription = stream.listen((ServiceEvent event) {
     if (event.kind == ServiceEvent.kPauseStart) {
       print('Received $event');
       subscription.cancel();
       completer.complete();
-    } else {
-      print('Ignoring event $event');
     }
   });
-  print('Subscribed.  Pause event is ${isolate.pauseEvent}');
 
   if (isolate.pauseEvent != null &&
       isolate.pauseEvent.kind == ServiceEvent.kPauseStart) {
     // Wait for the isolate to hit PauseStart.
     subscription.cancel();
-    print('Subscription cancelled.');
   } else {
-    print('Waiting for pause start event.');
     await completer.future;
   }
   print('Done waiting for pause event.');
 
-  // Grab the timestamp.
-  var pausetime1 = isolate.pauseEvent.timestamp;
-  expect(pausetime1, isNotNull);
-  // Reload the isolate.
-  await isolate.reload();
-  // Verify that it is the same.
-  expect(pausetime1.millisecondsSinceEpoch,
-         equals(isolate.pauseEvent.timestamp.millisecondsSinceEpoch));
-
+  // Wait for the isolate to pause due to interruption.
   completer = new Completer();
   stream = await isolate.vm.getEventStream(VM.kDebugStream);
+  bool receivedInterrupt = false;
   subscription = stream.listen((ServiceEvent event) {
-    if (event.kind == ServiceEvent.kPauseExit) {
-      print('Received PauseExit');
+    print('Received $event');
+    if (event.kind == ServiceEvent.kPauseInterrupted) {
+      receivedInterrupt = true;
       subscription.cancel();
       completer.complete();
     }
   });
 
-  print('Resuming...');
-  isolate.resume();
+  await isolate.resume();
 
-  // Wait for the isolate to hit PauseExit.
+  // Wait for the isolate to become idle.  We detect this by querying
+  // the stack until it becomes empty.
+  var frameCount;
+  do {
+    var stack = await isolate.getStack();
+    frameCount = stack['frames'].length;
+    print('frames: $frameCount');
+    sleep(const Duration(milliseconds:10));
+  } while (frameCount > 0);
+
+  // Make sure that the isolate receives an interrupt even when it is
+  // idle. (https://github.com/dart-lang/sdk/issues/24349)
+  await isolate.pause();
   await completer.future;
-
-  // Grab the timestamp.
-  var pausetime2 = isolate.pauseEvent.timestamp;
-  expect(pausetime2, isNotNull);
-  // Reload the isolate.
-  await isolate.reload();
-  // Verify that it is the same.
-  expect(pausetime2.millisecondsSinceEpoch,
-         equals(isolate.pauseEvent.timestamp.millisecondsSinceEpoch));
-  expect(pausetime2.millisecondsSinceEpoch,
-         greaterThan(pausetime1.millisecondsSinceEpoch));
+  expect(receivedInterrupt, isTrue);
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests,
                               testeeConcurrent: testMain,
                               pause_on_start: true,
-                              pause_on_exit: true,
                               trace_service: true,
                               verbose_vm: true);