Revert "Revert "Use native async/await support in pub.""

sdk/lib/_internal/pub_generated/test/dart2js/ignores_non_entrypoint_dart_files_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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-import '../serve/utils.dart';
-
-main() {
-  initConfig();
-  setUp(() {
-    d.dir(
-        appPath,
-        [
-            d.appPubspec(),
-            d.dir(
-                'web',
-                [
-                    d.file('file1.dart', 'var main = () => print("hello");'),
-                    d.file('file2.dart', 'void main(arg1, arg2, arg3) => print("hello");'),
-                    d.file('file3.dart', 'class Foo { void main() => print("hello"); }'),
-                    d.file('file4.dart', 'var foo;')])]).create();
-  });
-
-  integration("build ignores non-entrypoint Dart files", () {
-    schedulePub(
-        args: ["build"],
-        output: new RegExp(r'Built 0 files to "build".'));
-
-    d.dir(appPath, [d.dir('build', [d.nothing('web')])]).validate();
-  });
-
-  integration("serve ignores non-entrypoint Dart files", () {
-    pubServe();
-    requestShould404("file1.dart.js");
-    requestShould404("file2.dart.js");
-    requestShould404("file3.dart.js");
-    requestShould404("file4.dart.js");
-    endPubServe();
-  });
-
-}