Removed obsolete code

utils/lib/file_system_vm.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.
-
-// TODO(terry): Investigate common library for file I/O shared between frog and tools.
-
-library file_system_vm;
-import 'dart:convert';
-import 'dart:io';
-import 'file_system.dart';
-
-/** File system implementation using the vm api's. */
-class VMFileSystem implements FileSystem {
-  void writeString(String path, String text) {
-    var file = new File(path).openSync(mode: FileMode.WRITE);
-    file.writeStringSync(text);
-    file.closeSync();
-  }
-
-  String readAll(String filename) {
-    var file = (new File(filename)).openSync();
-    var length = file.lengthSync();
-    var buffer = new List<int>(length);
-    var bytes = file.readIntoSync(buffer, 0, length);
-    file.closeSync();
-    return UTF8.decode(bytes);
-  }
-
-  bool fileExists(String filename) {
-    return new File(filename).existsSync();
-  }
-
-  void createDirectory(String path, [bool recursive = false]) {
-    // TODO(rnystrom): Implement.
-    throw 'createDirectory() is not implemented by VMFileSystem yet.';
-  }
-
-  void removeDirectory(String path, [bool recursive = false]) {
-    // TODO(rnystrom): Implement.
-    throw 'removeDirectory() is not implemented by VMFileSystem yet.';
-  }
-}