Start pulling pub from its own repo.

sdk/lib/_internal/pub/test/snapshot/doesnt_resnapshot_when_a_dependency_is_unchanged_test.dart

-// Copyright (c) 2014, 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 'package:path/path.dart' as p;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("doesn't recreate a snapshot when no dependencies of a package "
-      "have changed", () {
-    servePackages((builder) {
-      builder.serve("foo", "1.2.3", deps: {"bar": "any"}, contents: [
-        d.dir("bin", [d.file("hello.dart", "void main() => print('hello!');")])
-      ]);
-      builder.serve("bar", "1.2.3");
-    });
-
-    d.appDir({"foo": "1.2.3"}).create();
-
-    pubGet(output: contains("Precompiled foo:hello."));
-
-    pubUpgrade(output: isNot(contains("Precompiled foo:hello.")));
-
-    d.dir(p.join(appPath, '.pub', 'bin'), [
-      d.file('sdk-version', '0.1.2+3\n'),
-      d.dir('foo', [d.matcherFile('hello.dart.snapshot', contains('hello!'))])
-    ]).validate();
-  });
-}