Move package:testing to SDK.

pkg/testing/test/dart_sdk_negative_test.dart

Index: pkg/testing/test/dart_sdk_negative_test.dart
diff --git a/pkg/testing/test/dart_sdk_negative_test.dart b/pkg/testing/test/dart_sdk_negative_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..21b36ff77c89b253580943305dbb302b365c407d
--- /dev/null
+++ b/pkg/testing/test/dart_sdk_negative_test.dart
@@ -0,0 +1,7 @@
+// 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.md file.
+
+main() {
+  throw "This is a negative test.";
+}