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

sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart

Index: sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart b/sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart
deleted file mode 100644
index c3e2bf7617ac390f2db6d278e931327aeb7c3d9a..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart
+++ /dev/null
@@ -1,35 +0,0 @@
-// Copyright (c) 2013, 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.validator.utf8_readme;
-
-import 'dart:async';
-import 'dart:convert';
-
-import '../entrypoint.dart';
-import '../io.dart';
-import '../validator.dart';
-
-/// Validates that a package's README is valid utf-8.
-class Utf8ReadmeValidator extends Validator {
-  Utf8ReadmeValidator(Entrypoint entrypoint)
-      : super(entrypoint);
-
-  Future validate() {
-    return new Future.sync(() {
-      var readme = entrypoint.root.readmePath;
-      if (readme == null) return;
-      var bytes = readBinaryFile(readme);
-      try {
-        // UTF8.decode doesn't allow invalid UTF-8.
-        UTF8.decode(bytes);
-      } on FormatException catch (_) {
-        warnings.add(
-            "$readme contains invalid UTF-8.\n"
-                "This will cause it to be displayed incorrectly on " "pub.dartlang.org.");
-      }
-    });
-  }
-}
-