Store the async-await compiled pub code directly in the repo.

sdk/lib/_internal/pub_generated/lib/src/validator/directory.dart

Index: sdk/lib/_internal/pub_generated/lib/src/validator/directory.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/validator/directory.dart b/sdk/lib/_internal/pub_generated/lib/src/validator/directory.dart
new file mode 100644
index 0000000000000000000000000000000000000000..133b3da4fc909273023fa3e4a20f1ec1a1924423
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/lib/src/validator/directory.dart
@@ -0,0 +1,37 @@
+library pub.validator.directory;
+import 'dart:async';
+import 'package:path/path.dart' as path;
+import '../entrypoint.dart';
+import '../io.dart';
+import '../utils.dart';
+import '../validator.dart';
+class DirectoryValidator extends Validator {
+  DirectoryValidator(Entrypoint entrypoint) : super(entrypoint);
+  static final _PLURAL_NAMES = [
+      "benchmarks",
+      "docs",
+      "examples",
+      "tests",
+      "tools"];
+  Future validate() {
+    return syncFuture(() {
+      for (var dir in listDir(entrypoint.root.dir)) {
+        if (!dirExists(dir)) continue;
+        dir = path.basename(dir);
+        if (_PLURAL_NAMES.contains(dir)) {
+          var singularName = dir.substring(0, dir.length - 1);
+          warnings.add(
+              'Rename the top-level "$dir" directory to ' '"$singularName".\n'
+                  'The Pub layout convention is to use singular directory ' 'names.\n'
+                  'Plural names won\'t be correctly identified by Pub and other ' 'tools.');
+        }
+        if (dir.contains(new RegExp(r"^samples?$"))) {
+          warnings.add(
+              'Rename the top-level "$dir" directory to "example".\n'
+                  'This allows Pub to find your examples and create "packages" '
+                  'directories for them.\n');
+        }
+      }
+    });
+  }
+}