Add FileSystemWatcher class to dart:io.

sdk/lib/io/directory_impl.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.
 
 part of dart.io;
 
-class _Directory implements Directory {
+class _Directory extends FileSystemEntity implements Directory {
   static const CREATE_REQUEST = 0;
   static const DELETE_REQUEST = 1;
   static const EXISTS_REQUEST = 2;
   static const CREATE_TEMP_REQUEST = 3;
   static const LIST_START_REQUEST = 4;
   static const LIST_NEXT_REQUEST = 5;
   static const LIST_STOP_REQUEST = 6;
   static const RENAME_REQUEST = 7;
 
   final String path;
@@ skipping 204 matching lines @@
     if (newPath is !String) {
       throw new ArgumentError();
     }
     var result = _rename(path, newPath);
     if (result is OSError) {
       throw new DirectoryException("Rename failed", path, result);
     }
     return new Directory(newPath);
   }
 
-  static String _trimTrailingPathSeparators(String path) {
-    // Don't handle argument errors here.
-    if (path is! String) return path;
-    if (Platform.operatingSystem == 'windows') {
-      while (path.length > 1 &&
-             (path.endsWith(Platform.pathSeparator) ||
-              path.endsWith('/'))) {
-        path = path.substring(0, path.length - 1);
-      }
-    } else {
-      while (path.length > 1 && path.endsWith(Platform.pathSeparator)) {
-        path = path.substring(0, path.length - 1);
-      }
-    }
-    return path;
-  }
-
   Stream<FileSystemEntity> list({bool recursive: false,
                                  bool followLinks: true}) {
-    return new _AsyncDirectoryLister(_trimTrailingPathSeparators(path),
-                                     recursive,
-                                     followLinks).stream;
+    return new _AsyncDirectoryLister(
+        FileSystemEntity._trimTrailingPathSeparators(path),
+        recursive,
+        followLinks).stream;
   }
 
   List listSync({bool recursive: false, bool followLinks: true}) {
     if (recursive is! bool || followLinks is! bool) {
       throw new ArgumentError();
     }
-    return _list(_trimTrailingPathSeparators(path), recursive, followLinks);
+    return _list(
+        FileSystemEntity._trimTrailingPathSeparators(path),
+        recursive,
+        followLinks);
   }
 
   String toString() => "Directory: '$path'";
 
   bool _isErrorResponse(response) {
     return response is List && response[0] != _SUCCESS_RESPONSE;
   }
 
   _exceptionOrErrorFromResponse(response, String message) {
     assert(_isErrorResponse(response));
@@ skipping 141 matching lines @@
       controller.addError(
           new DirectoryException("Directory listing failed",
                                  errorPath,
                                  err));
     } else {
       controller.addError(
           new DirectoryException("Internal error"));
     }
   }
 }