Provide stdout and stderr output in the Observatory debugger.

runtime/observatory/tests/service/capture_stdio_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 'dart:async';
+import 'dart:developer';
+import 'dart:io';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'test_helper.dart';
+
+void test() {
+  debugger();
+  stdout.write('stdout');
+
+  debugger();
+  print('print');
+
+  debugger();
+  stderr.write('stderr');
+}
+
+var tests = [
+  hasStoppedAtBreakpoint,
+
+  (Isolate isolate) async {
+    Completer completer = new Completer();
+    var stdoutSub;
+    stdoutSub = await isolate.vm.listenEventStream(
+      VM.kStdoutStream,
+      (ServiceEvent event) {
+        expect(event.kind, equals('WriteEvent'));
+        expect(event.bytesAsString, equals('stdout'));
+        cancelFutureSubscription(stdoutSub).then((_) {
+          completer.complete();
+        });
+      });
+    await isolate.resume();
+    await completer.future;
+  },
+
+  hasStoppedAtBreakpoint,
+
+  (Isolate isolate) async {
+    Completer completer = new Completer();
+    var stdoutSub;
+    int eventNumber = 1;
+    stdoutSub = await isolate.vm.listenEventStream(
+      VM.kStdoutStream,
+      (ServiceEvent event) {
+        expect(event.kind, equals('WriteEvent'));
+        if (eventNumber == 1) {
+          expect(event.bytesAsString, equals('print'));
+        } else if (eventNumber == 2) {
+          expect(event.bytesAsString, equals('\n'));
+          cancelFutureSubscription(stdoutSub).then((_) {
+            completer.complete();
+          });
+        } else {
+          expect(true, false);
+        }
+        eventNumber++;
+      });
+    await isolate.resume();
+    await completer.future;
+  },
+
+  hasStoppedAtBreakpoint,
+
+  (Isolate isolate) async {
+    Completer completer = new Completer();
+    var stderrSub;
+    stderrSub = await isolate.vm.listenEventStream(
+      VM.kStderrStream,
+      (ServiceEvent event) {
+        expect(event.kind, equals('WriteEvent'));
+        expect(event.bytesAsString, equals('stderr'));
+        cancelFutureSubscription(stderrSub).then((_) {
+          completer.complete();
+        });
+      });
+    await isolate.resume();
+    await completer.future;
+  },
+];
+
+  
+main(args) => runIsolateTests(args, tests, testeeConcurrent: test);