First stab at a dev server in pub using barback.

sdk/lib/_internal/pub/test/pub_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 pub_tests;
 
 import 'dart:io';
 
 import 'package:scheduled_test/scheduled_test.dart';
 
@@ skipping 17 matching lines @@
               [solver]    Show steps during version resolution.
 
     -v, --verbose         Shortcut for "--verbosity=all".
 
     Available commands:
       cache      Inspect the system cache.
       deploy     Copy and compile all Dart entrypoints in the 'web' directory.
       help       Display help information for Pub.
       install    Install the current package's dependencies.
       publish    Publish the current package to pub.dartlang.org.
+      serve      Run a local web development server.
       update     Update the current package's dependencies to the latest versions.
       uploader   Manage uploaders for a package on pub.dartlang.org.
       version    Print pub version.
 
     Use "pub help [command]" for more information about a command.
     """;
 
 final VERSION_STRING = '''
     Pub 0.1.2+3
     ''';
@@ skipping 122 matching lines @@
       // The "version" file generated on developer builds is a little funky and
       // we need to make sure we don't choke on it.
       d.dir(sdkPath, [
         d.file('version', '0.1.2.0_r16279_bobross'),
       ]).create();
 
       schedulePub(args: ['version'], output: "Pub 0.1.2+0.r16279.bobross\n");
     });
   });
 }