Start pulling pub from its own repo.

sdk/lib/_internal/pub/test/serve/watch_removed_file_test.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 'package:path/path.dart' as path;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../lib/src/io.dart';
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-import 'utils.dart';
-
-main() {
-  initConfig();
-  integration("stop serving a file that is removed", () {
-    d.dir(appPath, [
-      d.appPubspec(),
-      d.dir("web", [
-        d.file("index.html", "body")
-      ])
-    ]).create();
-
-    pubServe();
-    requestShouldSucceed("index.html", "body");
-
-    schedule(() => deleteEntry(
-        path.join(sandboxDir, appPath, "web", "index.html")));
-
-    waitForBuildSuccess();
-    requestShould404("index.html");
-    endPubServe();
-  });
-}