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

sdk/lib/_internal/pub_generated/test/snapshot/upgrades_snapshot_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("upgrades a snapshot when its package is upgraded", () {
     servePackages((builder) {
-      builder.serve("foo", "1.2.3", contents: [
-        d.dir("bin", [
-          d.file("hello.dart", "void main() => print('hello!');")
-        ])
-      ]);
+      builder.serve(
+          "foo",
+          "1.2.3",
+          contents: [
+              d.dir("bin", [d.file("hello.dart", "void main() => print('hello!');")])]);
     });
 
-    d.appDir({"foo": "any"}).create();
+    d.appDir({
+      "foo": "any"
+    }).create();
 
     pubGet(output: contains("Precompiled foo:hello."));
 
-    d.dir(p.join(appPath, '.pub', 'bin', 'foo'), [
-      d.matcherFile('hello.dart.snapshot', contains('hello!'))
-    ]).validate();
+    d.dir(
+        p.join(appPath, '.pub', 'bin', 'foo'),
+        [d.matcherFile('hello.dart.snapshot', contains('hello!'))]).validate();
 
     servePackages((builder) {
-      builder.serve("foo", "1.2.4", contents: [
-        d.dir("bin", [
-          d.file("hello.dart", "void main() => print('hello 2!');")
-        ])
-      ]);
+      builder.serve(
+          "foo",
+          "1.2.4",
+          contents: [
+              d.dir("bin", [d.file("hello.dart", "void main() => print('hello 2!');")])]);
     });
 
     pubUpgrade(output: contains("Precompiled foo:hello."));
 
-    d.dir(p.join(appPath, '.pub', 'bin', 'foo'), [
-      d.matcherFile('hello.dart.snapshot', contains('hello 2!'))
-    ]).validate();
+    d.dir(
+        p.join(appPath, '.pub', 'bin', 'foo'),
+        [d.matcherFile('hello.dart.snapshot', contains('hello 2!'))]).validate();
 
     var process = pubRun(args: ['foo:hello']);
     process.stdout.expect("hello 2!");
     process.shouldExit();
   });
 }