Remove unused dart:async imports.
As of Dart 2.1, Future/Stream have been exported from dart:core.
diff --git a/pkgs/test_api/lib/src/frontend/async_matcher.dart b/pkgs/test_api/lib/src/frontend/async_matcher.dart
index 880901d..56ad776 100644
--- a/pkgs/test_api/lib/src/frontend/async_matcher.dart
+++ b/pkgs/test_api/lib/src/frontend/async_matcher.dart
@@ -2,8 +2,6 @@
// 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:matcher/matcher.dart';
import '../backend/invoker.dart';
diff --git a/pkgs/test_api/lib/src/frontend/expect.dart b/pkgs/test_api/lib/src/frontend/expect.dart
index cf3d927..3b5b4c6 100644
--- a/pkgs/test_api/lib/src/frontend/expect.dart
+++ b/pkgs/test_api/lib/src/frontend/expect.dart
@@ -2,8 +2,6 @@
// 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:matcher/matcher.dart';
import '../backend/closed_exception.dart';
diff --git a/pkgs/test_api/lib/src/frontend/future_matchers.dart b/pkgs/test_api/lib/src/frontend/future_matchers.dart
index efd9e76..696a9f1 100644
--- a/pkgs/test_api/lib/src/frontend/future_matchers.dart
+++ b/pkgs/test_api/lib/src/frontend/future_matchers.dart
@@ -2,8 +2,6 @@
// 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:matcher/matcher.dart';
import '../utils.dart';
diff --git a/pkgs/test_api/lib/src/frontend/stream_matcher.dart b/pkgs/test_api/lib/src/frontend/stream_matcher.dart
index 57dcf56..f9305a6 100644
--- a/pkgs/test_api/lib/src/frontend/stream_matcher.dart
+++ b/pkgs/test_api/lib/src/frontend/stream_matcher.dart
@@ -2,8 +2,6 @@
// 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:async/async.dart';
import 'package:matcher/matcher.dart';
diff --git a/pkgs/test_api/lib/src/frontend/stream_matchers.dart b/pkgs/test_api/lib/src/frontend/stream_matchers.dart
index e60bc58..869e6b4 100644
--- a/pkgs/test_api/lib/src/frontend/stream_matchers.dart
+++ b/pkgs/test_api/lib/src/frontend/stream_matchers.dart
@@ -2,8 +2,6 @@
// 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:async/async.dart';
import 'package:matcher/matcher.dart';
diff --git a/pkgs/test_api/lib/src/frontend/utils.dart b/pkgs/test_api/lib/src/frontend/utils.dart
index a2314c7..ac023e5 100644
--- a/pkgs/test_api/lib/src/frontend/utils.dart
+++ b/pkgs/test_api/lib/src/frontend/utils.dart
@@ -2,8 +2,6 @@
// 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';
-
/// Returns a [Future] that completes after the [event loop][] has run the given
/// number of [times] (20 by default).
///
diff --git a/pkgs/test_api/test/frontend/expect_test.dart b/pkgs/test_api/test/frontend/expect_test.dart
index 59842f2..ee8d243 100644
--- a/pkgs/test_api/test/frontend/expect_test.dart
+++ b/pkgs/test_api/test/frontend/expect_test.dart
@@ -2,8 +2,6 @@
// 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:test/test.dart';
import '../utils.dart';
diff --git a/pkgs/test_api/test/frontend/never_called_test.dart b/pkgs/test_api/test/frontend/never_called_test.dart
index c82cf8f..e9170f9 100644
--- a/pkgs/test_api/test/frontend/never_called_test.dart
+++ b/pkgs/test_api/test/frontend/never_called_test.dart
@@ -2,8 +2,6 @@
// 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:term_glyph/term_glyph.dart' as glyph;
import 'package:test/test.dart';
diff --git a/pkgs/test_api/test/frontend/tear_down_all_test.dart b/pkgs/test_api/test/frontend/tear_down_all_test.dart
index 83ca586..d6d209f 100644
--- a/pkgs/test_api/test/frontend/tear_down_all_test.dart
+++ b/pkgs/test_api/test/frontend/tear_down_all_test.dart
@@ -2,8 +2,6 @@
// 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:async/async.dart';
import 'package:test/test.dart';
diff --git a/pkgs/test_api/test/utils.dart b/pkgs/test_api/test/utils.dart
index 73e8c84..27082af 100644
--- a/pkgs/test_api/test/utils.dart
+++ b/pkgs/test_api/test/utils.dart
@@ -2,7 +2,6 @@
// 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 'dart:collection';
import 'package:test_api/src/backend/declarer.dart';
