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

sdk/lib/_internal/pub_generated/test/validator/sdk_constraint_test.dart

Index: sdk/lib/_internal/pub_generated/test/validator/sdk_constraint_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/validator/sdk_constraint_test.dart b/sdk/lib/_internal/pub_generated/test/validator/sdk_constraint_test.dart
deleted file mode 100644
index 27c568a4f769a4fd7c9213d71293757a86c06895..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/test/validator/sdk_constraint_test.dart
+++ /dev/null
@@ -1,48 +0,0 @@
-// 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.
-
-import 'dart:async';
-import 'dart:convert';
-
-import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
-import 'package:path/path.dart' as path;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../lib/src/entrypoint.dart';
-import '../../lib/src/validator.dart';
-import '../../lib/src/validator/sdk_constraint.dart';
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-import 'utils.dart';
-
-Validator sdkConstraint(Entrypoint entrypoint) =>
-    new SdkConstraintValidator(entrypoint);
-
-main() {
-  initConfig();
-
-  group('should consider a package valid if it', () {
-    integration('has no SDK constraint', () {
-      d.validPackage.create();
-      expectNoValidationError(sdkConstraint);
-    });
-
-    integration('has an SDK constraint without ^', () {
-      d.dir(
-          appPath,
-          [d.libPubspec("test_pkg", "1.0.0", sdk: ">=1.8.0 <2.0.0")]).create();
-      expectNoValidationError(sdkConstraint);
-    });
-  });
-
-  test(
-      "should consider a package invalid if it has an SDK constraint with " "^",
-      () {
-    d.dir(appPath, [d.libPubspec("test_pkg", "1.0.0", sdk: "^1.8.0")]).create();
-    expect(
-        schedulePackageValidation(sdkConstraint),
-        completion(pairOf(anyElement(contains('">=1.8.0 <2.0.0"')), isEmpty)));
-  });
-}