Change Mac OS to OS X in dart:io dartdoc

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;
 
 /**
  * Information about the environment in which the current program is running.
  *
  * Platform provides information such as the operating system,
@@ skipping 82 matching lines @@
    * Get the local hostname for the system.
    */
   static String get localHostname => _localHostname;
 
   /**
    * Returns true if the operating system is Linux.
    */
   static final bool isLinux = (_operatingSystem == "linux");
 
   /**
-   * Returns true if the operating system is Mac OS.
+   * Returns true if the operating system is OS X.
    */
   static final bool isMacOS = (_operatingSystem == "macos");
 
   /**
    * Returns true if the operating system is Windows.
    */
   static final bool isWindows = (_operatingSystem == "windows");
 
   /**
    * Returns true if the operating system is Android.
@@ skipping 55 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;
 }