Remove dart:platform library.

sdk/lib/_internal/lib/platform_patch.dart

Index: sdk/lib/_internal/lib/platform_patch.dart
diff --git a/sdk/lib/_internal/lib/platform_patch.dart b/sdk/lib/_internal/lib/platform_patch.dart
deleted file mode 100644
index 13fdeb8e5f784a3249b6ac3fb3853b66fe25f9d8..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/lib/platform_patch.dart
+++ /dev/null
@@ -1,24 +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.
-
-patch int get numberOfProcessors => null;
-
-patch String get pathSeparator => '/';
-
-patch String get operatingSystem => null;
-
-patch String get localHostname => null;
-
-patch String get version => null;
-
-patch Map<String, String> get environment => null;
-
-patch String get executable => null;
-
-patch Uri get script => null;
-
-// An unmodifiable list.
-patch List<String> get executableArguments => new List<String>(0);
-
-patch String get packageRoot => null;