pkg/scheduled_test: fix example in docs to be 100% valid

pkg/scheduled_test/lib/descriptor.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.
 
 /// A library for declaratively describing a filesystem structure, usually for
 /// the purpose of creating or validating it as part of a scheduled test.
 ///
 /// You can use [dir] and [file] to define a filesystem structure. Then, you can
 /// call [Descriptor.create] to schedule a task that will create that structure
 /// on the physical filesystem, or [Descriptor.validate] to schedule an
 /// assertion that that structure exists. For example:
 ///
+///     import 'dart:io';

[Bob Nystrom, 2014/02/19 18:17:28]

Nit, but can you add a blank line after this import?

[kevmoo, 2014/02/19 21:53:12]

Done.

 ///     import 'package:scheduled_test/descriptor.dart' as d;
 ///     import 'package:scheduled_test/scheduled_test.dart';
 ///
 ///     void main() {
 ///       test('Directory.rename', () {
 ///         d.dir('parent', [
 ///           d.file('sibling', 'sibling-contents'),
 ///           d.dir('old-name', [
 ///             d.file('child', 'child-contents')
 ///           ])
 ///         ]).create();
 ///
 ///         schedule(() =>
 ///             new Directory('parent/old-name').rename('parent/new-name'));
 ///
 ///         d.dir('parent', [
 ///           d.file('sibling', 'sibling-contents'),
 ///           d.dir('new-name', [
 ///             d.file('child', 'child-contents')
 ///           ])
 ///         ]).validate();
-///       })
+///       });
 ///     }
 ///
 /// Usually you don't want your tests cluttering up your working directory with
 /// fake filesystem entities. You can set [defaultRoot] to configure where
 /// filesystem descriptors are rooted on the physical filesystem. For example,
 /// to create a temporary directory for each test:
 ///
 ///     import 'package:scheduled_test/descriptor.dart' as d;
 ///     import 'package:scheduled_test/scheduled_test.dart';
 ///
@@ skipping 90 matching lines @@
 
 /// A convenience method for creating a [PatternDescriptor] descriptor that
 /// constructs a [FileDescriptor] descriptor.
 PatternDescriptor filePattern(Pattern name, [String contents='']) =>
   pattern(name, (realName) => file(realName, contents));
 
 /// A convenience method for creating a [PatternDescriptor] descriptor that
 /// constructs a [DirectoryDescriptor] descriptor.
 PatternDescriptor dirPattern(Pattern name, [Iterable<Descriptor> contents]) =>
   pattern(name, (realName) => dir(realName, contents));