Fork test scripts to support special runtime checkout.

testing/dart/multitest.dart

 // Copyright (c) 2011, 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("multitest");
 
 // Multitests are Dart test scripts containing lines of the form
 // " [some dart code] /// [key]: [error type]"
 //
 // For each key in the file, a new test file is made containing all
@@ skipping 170 matching lines @@
   };
   file.create();
 }
 
 String CreateMultitestDirectory(String buildDir, String testDir) {
   final String generatedTestDirectory = 'generated_tests/';
   Directory parent_dir = new Directory(buildDir + generatedTestDirectory);
   if (!parent_dir.existsSync()) {
     parent_dir.createSync();
   }
-  final String prefix = 'tests/';
-  final String suffix = '/src';
-  Expect.isTrue(testDir.startsWith(prefix));
-  Expect.isTrue(testDir.endsWith(suffix));
-  String path = parent_dir.path +
-      testDir.substring(prefix.length, testDir.length - suffix.length);
+  var split = testDir.split(new Platform().pathSeparator());
+  var lastComponent = split.removeLast();
+  Expect.isTrue(lastComponent == 'src');
+  String path = parent_dir.path + split.last();
   Directory dir = new Directory(path);
   if (!dir.existsSync()) {
     dir.createSync();
   }
   return path;
-}
+}