Change Platform members to getters instead of methods.

utils/pub/io.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.
 
 /**
  * Helper functionality to make working with IO easier.
  */
 #library('pub_io');
 
 #import('dart:io');
@@ skipping 20 matching lines @@
         parts.removeLast();
       } else if (piece != '') {
         if (parts.length > 0 && parts.last() == '.') {
           parts.removeLast();
         }
         parts.add(piece);
       }
     }
   }
 
-  return Strings.join(parts, Platform.pathSeparator());
+  return Strings.join(parts, Platform.pathSeparator);
 }
 
 /**
  * Gets the basename, the file name without any leading directory path, for
  * [file], which can either be a [String], [File], or [Directory].
  */
 String basename(file) {
   return fs.basename(_getPath(file));
 }
 
@@ skipping 266 matching lines @@
 }
 
 /**
  * Gets a [Directory] for [entry], which can either already be one, or be a
  * [String].
  */
 Directory _getDirectory(entry) {
   if (entry is Directory) return entry;
   return new Directory(entry);
 }