Ignore all trailing separators in path.extension.

pkg/path/test/windows_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.windows_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:path/path.dart' as path;
 
 main() {
@@ skipping 17 matching lines @@
     expect(builder.extension('.'), '');
     expect(builder.extension('..'), '');
     expect(builder.extension('a/..'), '');
     expect(builder.extension('foo.dart'), '.dart');
     expect(builder.extension('foo.dart.js'), '.js');
     expect(builder.extension('foo bar\gule fisk.dart.js'), '.js');
     expect(builder.extension(r'a.b\c'), '');
     expect(builder.extension('a.b/c.d'), '.d');
     expect(builder.extension(r'~\.bashrc'), '');
     expect(builder.extension(r'a.b/c'), r'');
+    expect(builder.extension(r'foo.dart\'), '.dart');
+    expect(builder.extension(r'foo.dart\\'), '.dart');
   });
 
   test('rootPrefix', () {
     expect(builder.rootPrefix(''), '');
     expect(builder.rootPrefix('a'), '');
     expect(builder.rootPrefix(r'a\b'), '');
     expect(builder.rootPrefix(r'C:\a\c'), r'C:\');
     expect(builder.rootPrefix('C:\\'), r'C:\');
     expect(builder.rootPrefix('C:/'), 'C:/');
 
@@ skipping 466 matching lines @@
         Uri.parse('file:///C:/path/to/foo/'));
     expect(builder.toUri(r'C:\'), Uri.parse('file:///C:/'));
     expect(builder.toUri(r'\\hostname\'), Uri.parse('file://hostname/'));
     expect(builder.toUri(r'foo\bar'), Uri.parse('foo/bar'));
     expect(builder.toUri(r'C:\path\to\foo#bar'),
         Uri.parse('file:///C:/path/to/foo%23bar'));
     expect(builder.toUri(r'\\hostname\path\to\foo#bar'),
         Uri.parse('file://hostname/path/to/foo%23bar'));
   });
 }