Don't delay values and errors from async/await functions.

tests/lib/async/async_await_sync_completer_test.dart

Index: tests/lib/async/async_await_sync_completer_test.dart
diff --git a/tests/lib/async/async_await_sync_completer_test.dart b/tests/lib/async/async_await_sync_completer_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5865729e49c7b52a70b9fc3406650f2d2b395541
--- /dev/null
+++ b/tests/lib/async/async_await_sync_completer_test.dart
@@ -0,0 +1,49 @@
+// 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.
+
+import 'dart:async';
+import 'package:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
+
+import 'dart:async';
+
+var events = [];
+var delayedValue = new Completer();
+var delayedError = new Completer();
+
+foo() async {
+  new Future.microtask(() => 'in microtask')
+      .then(events.add)
+      .then(delayedValue.complete);
+  return 'in async function';
+}
+
+bar() async {
+  new Future.microtask(() => throw 'in microtask error')
+      .catchError(events.add)
+      .then(delayedError.complete);
+  throw 'in async function error';
+}
+
+void main() {
+  asyncStart();
+  var asyncValueFuture = foo().then(events.add);
+  var asyncErrorFuture = bar().catchError(events.add);
+  Future.wait([
+      asyncValueFuture,
+      delayedValue.future,
+      asyncErrorFuture,
+      delayedError.future]).then((_) {
+    // The body completed before nested microtask. So they should appear
+    // before the delayed functions. In other words, the async function should
+    // not unnecessarily delay the propagation of errors and values.
+    Expect.listEquals([
+        "in async function",
+        "in async function error",
+        "in microtask",
+        "in microtask error"],
+        events);
+    asyncEnd();
+  });
+}