Removed obsolete code

utils/lib/file_system.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.
-
-// TODO(terry): Investigate common library for file I/O shared between frog and tools.
-
-/** Abstraction for file systems and utility functions to manipulate paths. */
-library file_system;
-
-/**
- * Abstraction around file system access to work in a variety of different
- * environments.
- */
-abstract class FileSystem {
-  String readAll(String filename);
-
-  void writeString(String outfile, String text);
-
-  bool fileExists(String filename);
-
-  void createDirectory(String path, [bool recursive]);
-  void removeDirectory(String path, [bool recursive]);
-}
-
-/**
- * Replaces all back slashes (\) with forward slashes (/) in [path] and
- * return the result.
- */
-String canonicalizePath(String path) {
-  return path.replaceAll('\\', '/');
-}
-
-/** Join [path1] to [path2]. */
-String joinPaths(String path1, String path2) {
-  path1 = canonicalizePath(path1);
-  path2 = canonicalizePath(path2);
-
-  var pieces = path1.split('/');
-  for (var piece in path2.split('/')) {
-    if (piece == '..' && pieces.length > 0 && pieces.last != '.'
-      && pieces.last != '..') {
-      pieces.removeLast();
-    } else if (piece != '') {
-      if (pieces.length > 0 && pieces.last == '.') {
-        pieces.removeLast();
-      }
-      pieces.add(piece);
-    }
-  }
-  return pieces.join('/');
-}
-
-/** Returns the directory name for the [path]. */
-String dirname(String path) {
-  path = canonicalizePath(path);
-
-  int lastSlash = path.lastIndexOf('/', path.length);
-  if (lastSlash == -1) {
-    return '.';
-  } else {
-    return path.substring(0, lastSlash);
-  }
-}
-
-/** Returns the file name without directory for the [path]. */
-String basename(String path) {
-  path = canonicalizePath(path);
-
-  int lastSlash = path.lastIndexOf('/', path.length);
-  if (lastSlash == -1) {
-    return path;
-  } else {
-    return path.substring(lastSlash + 1);
-  }
-}