Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/transformer/loads_a_diamond_transformer_dependency_graph_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 '../descriptor.dart' as d;
-import '../test_pub.dart';
-import '../serve/utils.dart';
-
-main() {
-  initConfig();
-  withBarbackVersions("any", () {
-    integration("loads a diamond transformer dependency graph", () {
-      d.dir("top", [d.pubspec({
-          "name": "top",
-          "version": "1.0.0"
-        }),
-            d.dir("lib", [d.file("transformer.dart", dartTransformer('top')),])]).create();
-
-      d.dir("left", [d.pubspec({
-          "name": "left",
-          "version": "1.0.0",
-          "transformers": ["top/transformer"],
-          "dependencies": {
-            "top": {
-              "path": "../top"
-            }
-          }
-        }),
-            d.dir("lib", [d.file("transformer.dart", dartTransformer('left')),])]).create();
-
-      d.dir("right", [d.pubspec({
-          "name": "right",
-          "version": "1.0.0",
-          "transformers": ["top/transformer"],
-          "dependencies": {
-            "top": {
-              "path": "../top"
-            }
-          }
-        }),
-            d.dir(
-                "lib",
-                [d.file("transformer.dart", dartTransformer('right')),])]).create();
-
-      d.dir(appPath, [d.pubspec({
-          "name": "myapp",
-          "transformers": [
-              "left/transformer",
-              "right/transformer",
-              "myapp/transformer"],
-          "dependencies": {
-            'left': {
-              'path': '../left'
-            },
-            'right': {
-              'path': '../right'
-            },
-          }
-        }),
-            d.dir("lib", [d.file("transformer.dart", dartTransformer('myapp'))]),
-            d.dir("web", [d.file("main.dart", 'const TOKEN = "main.dart";')])]).create();
-
-      createLockFile(
-          'myapp',
-          sandbox: ['top', 'left', 'right'],
-          pkg: ['barback']);
-
-      pubServe();
-      requestShouldSucceed(
-          "main.dart",
-          'const TOKEN = "(((main.dart, (left, top)), (right, top)), ((myapp, '
-              '(left, top)), (right, top)))";');
-      endPubServe();
-    });
-  });
-}