Stream blocks of timeline events over the service protocol

runtime/observatory/tests/service/vm_timeline_events_test.dart

+// Copyright (c) 2016, 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 'dart:async';
+import 'dart:developer';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+
+primeDartTimeline() {
+  while (true) {
+    Timeline.startSync('apple');
+    Timeline.finishSync();
+  }
+}
+
+bool isDart(Map event) => event['cat'] == 'Dart';
+
+List<Map> filterEvents(List<Map> events, filter) {
+  return events.where(filter).toList();
+}
+
+Completer completer = new Completer();
+int eventCount = 0;
+
+onTimelineEvent(ServiceEvent event) {
+  eventCount++;
+  expect(filterEvents(event.timelineEvents, isDart).length, greaterThan(0));
+  if (eventCount == 5) {
+    completer.complete(eventCount);
+  }
+}
+
+var tests = [
+  (Isolate isolate) async {
+    // Subscribe to the Timeline stream.
+    await subscribeToStream(isolate.vm, VM.kTimelineStream, onTimelineEvent);
+  },
+  (Isolate isolate) async {
+    // Ensure we don't get any events before enabling Dart.
+    await new Future.delayed(new Duration(seconds: 5));
+    expect(eventCount, 0);
+  },
+  (Isolate isolate) async {
+    // Get the flags.
+    Map flags = await isolate.vm.invokeRpcNoUpgrade('_getVMTimelineFlags', {});
+    expect(flags['type'], 'TimelineFlags');
+    // Confirm that 'Dart' is available.
+    expect(flags['availableStreams'].contains('Dart'), isTrue);
+    // Confirm that nothing is being recorded.
+    expect(flags['recordedStreams'].length, equals(0));
+  },
+  (Isolate isolate) async {
+    // Enable the Dart category.
+    await isolate.vm.invokeRpcNoUpgrade('_setVMTimelineFlags', {
+      "recordedStreams": ["Dart"]
+    });
+  },
+  (Isolate isolate) async {
+    // Wait to receive events.
+    await completer.future;
+    cancelStreamSubscription(VM.kTimelineStream);
+  },
+];
+
+main(args) async => runIsolateTests(args,
+                                    tests,
+                                    testeeConcurrent: primeDartTimeline);