Move package:testing to SDK.

pkg/testing/bin/run_tests.dart

Index: pkg/testing/bin/run_tests.dart
diff --git a/pkg/testing/bin/run_tests.dart b/pkg/testing/bin/run_tests.dart
new file mode 100755
index 0000000000000000000000000000000000000000..06581f6bf8386f03769c519cc2469b21b37ee28e
--- /dev/null
+++ b/pkg/testing/bin/run_tests.dart
@@ -0,0 +1,8 @@
+#!/usr/bin/env dart -c
+// 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.
+
+import "package:testing/src/run_tests.dart" as run_tests;
+
+main(List<String> arguments) => run_tests.main(arguments);