Add empty dart:platform library.

sdk/lib/_internal/libraries.dart

 // Copyright (c) 2012, 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.
 
 library libraries;
 
 /**
  * A bit flag used by [LibraryInfo] indicating that a library is used by dart2js
  */
 const int DART2JS_PLATFORM = 1;
@@ skipping 77 matching lines @@
       "json/json.dart",
       maturity: Maturity.DEPRECATED),
 
   "math": const LibraryInfo(
       "math/math.dart",
       maturity: Maturity.STABLE,
       dart2jsPatchPath: "_internal/lib/math_patch.dart"),
 
   "mirrors": const LibraryInfo(
       "mirrors/mirrors.dart",
-      maturity: Maturity.UNSTABLE, 
+      maturity: Maturity.UNSTABLE,
       dart2jsPatchPath: "_internal/lib/mirrors_patch.dart"),
 
   "nativewrappers": const LibraryInfo(
       "html/dartium/nativewrappers.dart",
       category: "Client",
       implementation: true,
       documented: false,
       platforms: VM_PLATFORM),
 
+  "platform": const LibraryInfo(
+      "platform/platform.dart",
+      maturity: Maturity.UNSTABLE,
+      dart2jsPatchPath: "_internal/lib/platform_patch.dart"),
+
   "typed_data": const LibraryInfo(
       "typed_data/typed_data.dart",
       maturity: Maturity.STABLE,
       dart2jsPath: "typed_data/dart2js/typed_data_dart2js.dart"),
 
   "svg": const LibraryInfo(
       "svg/dartium/svg_dartium.dart",
       category: "Client",
       maturity: Maturity.WEB_STABLE,
       dart2jsPath: "svg/dart2js/svg_dart2js.dart"),
@@ skipping 173 matching lines @@
     "The library is stable. API backwards-compatibility is guaranteed.\n"
     "However implementation details might change.");
   
   static const Maturity LOCKED = const Maturity(5, "Locked",
     "This library will not change except when serious bugs are encountered.");
 
   static const Maturity UNSPECIFIED = const Maturity(-1, "Unspecified",
     "The maturity for this library has not been specified.");
 }