Ignore all trailing separators in path.extension.

pkg/path/test/posix_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.
 
 library path.test.posix_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:path/path.dart' as path;
 
 main() {
@@ skipping 13 matching lines @@
   test('extension', () {
     expect(builder.extension(''), '');
     expect(builder.extension('.'), '');
     expect(builder.extension('..'), '');
     expect(builder.extension('foo.dart'), '.dart');
     expect(builder.extension('foo.dart.js'), '.js');
     expect(builder.extension('a.b/c'), '');
     expect(builder.extension('a.b/c.d'), '.d');
     expect(builder.extension('~/.bashrc'), '');
     expect(builder.extension(r'a.b\c'), r'.b\c');
+    expect(builder.extension('foo.dart/'), '.dart');
+    expect(builder.extension('foo.dart//'), '.dart');
   });
 
   test('rootPrefix', () {
     expect(builder.rootPrefix(''), '');
     expect(builder.rootPrefix('a'), '');
     expect(builder.rootPrefix('a/b'), '');
     expect(builder.rootPrefix('/a/c'), '/');
     expect(builder.rootPrefix('/'), '/');
   });
 
@@ skipping 424 matching lines @@
 
   test('toUri', () {
     expect(builder.toUri('/path/to/foo'), Uri.parse('file:///path/to/foo'));
     expect(builder.toUri('/path/to/foo/'), Uri.parse('file:///path/to/foo/'));
     expect(builder.toUri('/'), Uri.parse('file:///'));
     expect(builder.toUri('foo/bar'), Uri.parse('foo/bar'));
     expect(builder.toUri('/path/to/foo#bar'),
         Uri.parse('file:///path/to/foo%23bar'));
   });
 }