Remove dart:platform library.

sdk/lib/io/platform.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.
 
 part of dart.io;
 
 /**
- * Deprecated: the [Platform] class exposes details of the machine and operating
+ * The [Platform] class exposes details of the machine and operating
  * system.
- *
- * This class has been replaced by adding the dart:platform library to Dart.
- * dart:platform is available on all browser and standalone platforms,
- * including Dart code that has been compiled to javascript.
- *
- * The dart:platform class has
- * the same top-level getters as the members of [Platform], except that the
- * [isWindows], [isLinux], [isAndroid], and [isMacOS] getters
- * have been removed. On platforms supporting dart:io, the getters of
- * dart:platform have the same values as the Platform class members, except
- * that [script] has been changed from a [String] to a file [Uri].
  */
 @deprecated
 class Platform {
   static final _numberOfProcessors = _Platform.numberOfProcessors;
   static final _pathSeparator = _Platform.pathSeparator;
   static final _operatingSystem = _Platform.operatingSystem;
   static final _localHostname = _Platform.localHostname;
   static final _version = _Platform.version;
 
   // This script singleton is written to by the embedder if applicable.
@@ skipping 85 matching lines @@
    *
    * If there is no --package-root flag, then the empty string is returned.
    */
   static String get packageRoot => _Platform.packageRoot;
 
   /**
    * Returns the version of the current Dart runtime.
    */
   static String get version => _version;
 }