Revert co19 roll attempt

DEPS

 # Copyright (c) 2012, 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.
 
 vars = {
   # The dart_root is the root of our sdk checkout. This is normally
   # simply sdk, but if using special gclient specs it can be different.
   "dart_root": "sdk",
 
   # We use mirrors of all github repos to guarantee reproducibility and
@@ skipping 11 matching lines @@
       "https://chromium.googlesource.com/external/github.com/dart-lang/%s.git",
 
   # Chromium git
   "chromium_git": "https://chromium.googlesource.com",
   "fuchsia_git": "https://fuchsia.googlesource.com",
 
   # Only use this temporarily while waiting for a mirror for a new package.
   "github_dartlang": "https://github.com/dart-lang/%s.git",
 
   "gyp_rev": "@6ee91ad8659871916f9aa840d42e1513befdf638",
-  "co19_rev": "@dec2b67aaab3bb7339b9764049707e71e601da3d",
+  "co19_rev": "@4af9ef149be554216c5bb16cbac8e50d4c28cdf1",
 
   # Revisions of GN related dependencies. This should match the revision
   # pulled by Flutter.
   "buildtools_revision": "@057ef89874e3c622248cf99259434fdc683c4e30",
 
   # Scripts that make 'git cl format' work.
   "clang_format_scripts_rev": "@c09c8deeac31f05bd801995c475e7c8070f9ecda",
 
   "gperftools_revision": "@02eeed29df112728564a5dde6417fa4622b57a06",
 
@@ skipping 446 matching lines @@
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
     'action': ['python', 'sdk/build/vs_toolchain.py', 'update'],
   },
   {
     "pattern": ".",
     "action": ["python", Var("dart_root") + "/tools/generate_buildfiles.py"],
   },
 ]