Support dependencies in SDK packages.

utils/tests/pub/pub_update_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('test_pub.dart');
 #import('../../../pkg/unittest/unittest.dart');
@@ skipping 59 matching lines @@
     ]).scheduleValidate();
 
     run();
   });
 
   test('does not add a package if it does not have a "lib" directory', () {
     // Using an SDK source, but this should be true of all sources.
     dir(sdkPath, [
       file('revision', '1234'),
       dir('pkg', [
-        dir('foo', [])
+        dir('foo', [
+          libPubspec('foo', '0.0.0-not.used')
+        ])
       ])
     ]).scheduleCreate();
 
     dir(appPath, [
       pubspec({"name": "myapp", "dependencies": {"foo": {"sdk": "foo"}}})
     ]).scheduleCreate();
 
     schedulePub(args: ['update'],
         output: '''
         Dependencies updated!
         ''');
 
     packagesDir({"foo": null}).scheduleValidate();
 
     run();
   });
 }