Remove dart:platform library.

tests/lib/platform/number_of_processors_test.dart

Index: tests/lib/platform/number_of_processors_test.dart
diff --git a/tests/lib/platform/number_of_processors_test.dart b/tests/lib/platform/number_of_processors_test.dart
deleted file mode 100644
index 043914d4c75cd7f5c7a5537b32565434a7fbbf0d..0000000000000000000000000000000000000000
--- a/tests/lib/platform/number_of_processors_test.dart
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright (c) 2013, 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:platform" as platform;
-
-import "package:unittest/unittest.dart";
-
-main() {
-  if (platform.operatingSystem != null) {
-    expect(platform.numberOfProcessors, isPositive);
-  } else {
-    expect(platform.numberOfProcessors, isNull);
-  }
-}