Implement toString on File and Directory objects.

tests/standalone/io/file_test.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.
 //
 // Dart test program for testing file I/O.
 
 import "dart:io";
 import "dart:isolate";
 
 class MyListOfOneElement implements List {
@@ skipping 26 matching lines @@
 
   static void deleteTempDirectory() {
     tempDirectory.deleteSync(recursive: true);
   }
 
   // Test for file read functionality.
   static void testReadStream() {
     // Read a file and check part of it's contents.
     String filename = getFilename("bin/file_test.cc");
     File file = new File(filename);
+    Expect.isTrue('$file'.contains(file.name));
     InputStream input = file.openInputStream();
     input.onData = () {
       List<int> buffer = new List<int>(42);
       int bytesRead = input.readInto(buffer, 0, 12);
       Expect.equals(12, bytesRead);
       bytesRead = input.readInto(buffer, 12, 30);
       input.close();
       Expect.equals(30, bytesRead);
       Expect.equals(47, buffer[0]);  // represents '/' in the file.
       Expect.equals(47, buffer[1]);  // represents '/' in the file.
@@ skipping 1271 matching lines @@
       testDirectorySync();
       testWriteStringUtf8();
       testWriteStringUtf8Sync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }