Fixed path issue on windows

tools/testing/dart/test_suite.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.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 807 matching lines @@
    * or in the build directory, and will return a String representing
    * the relative path to either the dart or the build directory.
    * Thus, the returned [String] will be the path component of the URL
    * corresponding to [file] (the http server serves files relative to the
    * dart/build directories).
    */
   String _createUrlPathFromFile(Path file) {
     file = TestUtils.absolutePath(file);
     var fileString = file.toString();
     
-    var relativeBuildDir = TestUtils.buildDir(configuration);
-    var buildDir = TestUtils.absolutePath(new Path(relativeBuildDir));
+    var relativeBuildDir = new Path(TestUtils.buildDir(configuration));
+    var buildDir = TestUtils.absolutePath(relativeBuildDir);
     var dartDir = TestUtils.dartDir();
 
     var pathComponent;
     if (fileString.startsWith(buildDir.toString())) {
       var fileRelativeToBuildDir = file.relativeTo(buildDir);
       pathComponent = "$relativeBuildDir/$fileRelativeToBuildDir";
     } else if (fileString.startsWith(dartDir.toString())) {
       pathComponent = file.relativeTo(dartDir);
     } else {
       // Unreachable
@@ skipping 1104 matching lines @@
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout
  * $compileErrorSkip tests are skipped on browsers due to compile-time error
 """;
     print(report);
    }
 }