Add a test for pub's async_await compiler.

sdk/lib/_internal/pub/test/async_compile_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.
+
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:scheduled_test/descriptor.dart' as d;
+import 'package:scheduled_test/scheduled_test.dart';
+import 'package:scheduled_test/scheduled_process.dart';
+
+import 'test_pub.dart';
+import '../lib/src/io.dart';
+
+void main() {
+  integration("the generated pub source is up to date", () {
+    var compilerArgs = Platform.executableArguments.toList()..addAll([
+      p.join(pubRoot, 'bin', 'async_compile.dart'),
+      '--force', '--verbose', '--no-snapshot',
+      p.join(sandboxDir, "pub_generated"),

[ricow1, 2014/12/02 06:25:45]

what is sandboxDir here? A temp dir? will it be cleaned up afterwards?
The reason I am asking is, that if I run:
tools/test.py -mrelease pub

I get 3 leftover pub testing folders in /tmp

[Bob Nystrom, 2014/12/02 19:15:50]

Yes, it should be.
That sounds like a bug either in scheduled_test or pub's test infrastructure. :(

+      p.join(sandboxDir, "build")
+    ]);
+
+    new ScheduledProcess.start(Platform.executable, compilerArgs).shouldExit(0);
+
+    new d.DirectoryDescriptor.fromFilesystem("pub_generated",
+        p.join(pubRoot, "..", "pub_generated")).validate();
+  });
+}