Move pub into sdk/lib/_internal.

sdk/lib/_internal/pub/test/validator/pubspec_field_test.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.
 
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../../pub/entrypoint.dart';
-import '../../../pub/validator.dart';
-import '../../../pub/validator/pubspec_field.dart';
+import '../../lib/src/entrypoint.dart';
+import '../../lib/src/validator.dart';
+import '../../lib/src/validator/pubspec_field.dart';
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
 
 Validator pubspecField(Entrypoint entrypoint) =>
   new PubspecFieldValidator(entrypoint);
 
 main() {
   initConfig();
 
@@ skipping 73 matching lines @@
         "Bob Nystrom <rnystrom@google.com>",
         "<nweiz@google.com>",
         "John Messerly <jmesserly@google.com>"
       ];
       d.dir(appPath, [d.pubspec(pkg)]).create();
 
       expectValidationWarning(pubspecField);
     });
   });
 }