Revert change to Platform.excutable and add Platform.resolvedExecutable

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 113 matching lines @@
    * returned on Windows is therefore case-insensitive and will convert
    * all keys to upper case. On other platforms the returned map is
    * a standard case-sensitive map.
    */
   static Map<String, String> get environment => _Platform.environment;
 
   /**
    * Returns the path of the executable used to run the script in this
    * isolate.
    *
-   * If supported by the platform the returned path will be absolute.
+   * The path returned is the literal path used to run the script. This
+   * path might be relative or just be a name from which the executable
+   * was found by searching the `PATH`.
    *
-   * If the execution environment does not support [executable] an empty
-   * string is returned.
+   * To get the absolute path to the resolved executable use
+   * [resolvedExecutable].
    */
   static String get executable => _Platform.executable;
 
   /**
+   * Returns the path of the executable used to run the script in this
+   * isolate after it has been resolved by the OS.
+   *
+   * This is the absolute path, with all symlinks resolved, to the
+   * executable used to run the script.
+   */
+  static String get resolvedExecutable => _Platform.resolvedExecutable;
+
+  /**
    * Returns the absolute URI of the script being run in this
    * isolate.
    *
    * If the script argument on the command line is relative,
    * it is resolved to an absolute URI before fetching the script, and
    * this absolute URI is returned.
    *
    * URI resolution only does string manipulation on the script path, and this
    * may be different from the file system's path resolution behavior. For
    * example, a symbolic link immediately followed by '..' will not be
@@ skipping 24 matching lines @@
   /**
    * Returns the version of the current Dart runtime.
    *
    * The returned `String` is formatted as the
    * [semver](http://semver.org) version string of the current dart
    * runtime, possibly followed by whitespace and other version and
    * build details.
    */
   static String get version => _version;
 }