Remove uses of Path class from tests/standalone.

tests/standalone/io/file_test.dart

 // Copyright (c) 2013, 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.
 //
 // Dart test program for testing file I/O.
 
 import "package:expect/expect.dart";
+import "package:path/path.dart";
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 import 'dart:isolate';
 
 class MyListOfOneElement
     extends Object with ListMixin<int> implements List<int> {
   int _value;
   MyListOfOneElement(this._value);
   int get length => 1;
@@ skipping 901 matching lines @@
   static void testOpenDirectoryAsFileSync() {
     var f = new File('.');
     try {
       f.openSync();
       Expect.fail("Expected exception opening directory as file");
     } catch (e) {
       Expect.isTrue(e is FileException);
     }
   }
 
-  static void testOpenFileFromPath() {
+  static void testOpenFile() {
     var name = getFilename("tests/vm/data/fixed_length_file");
-    var path = new Path(name);
-    var f = new File.fromPath(path);
+    var f = new File(name);
     Expect.isTrue(f.existsSync());
     name = f.fullPathSync();
-    path = new Path(name);
-    var g = new File.fromPath(path);
+    var g = new File(name);
     Expect.isTrue(g.existsSync());
     Expect.equals(name, g.fullPathSync());
   }
 
   static void testReadAsBytes() {
     var port = new ReceivePort();
     port.receive((result, replyTo) {
       port.close();
       Expect.equals(42, result);
     });
@@ skipping 337 matching lines @@
     port = new ReceivePort();
     testRead();
     testReadSync();
     testReadStream();
     testLength();
     testLengthSync();
     testPosition();
     testPositionSync();
     testOpenDirectoryAsFile();
     testOpenDirectoryAsFileSync();
-    testOpenFileFromPath();
+    testOpenFile();
     testReadAsBytes();
     testReadAsBytesEmptyFile();
     testReadAsBytesSync();
     testReadAsBytesSyncEmptyFile();
     testReadAsText();
     testReadAsTextEmptyFile();
     testReadAsTextSync();
     testReadAsTextSyncEmptyFile();
     testReadAsLines();
     testReadAsLinesSync();
@@ skipping 26 matching lines @@
       testWriteStringUtf8Sync();
       testRename();
       testRenameSync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }