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

utils/pub/pub.gyp

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'pub',
       'type': 'none',
       'dependencies': [
@@ skipping 14 matching lines @@
             '<(SHARED_INTERMEDIATE_DIR)/pkg_files.stamp',
             '<(SHARED_INTERMEDIATE_DIR)/packages.stamp',
           ],
           'outputs': [
             '<(SHARED_INTERMEDIATE_DIR)/pub.dart.snapshot',
           ],
           'action': [
             '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)dart<(EXECUTABLE_SUFFIX)',
             '--package-root=<(PRODUCT_DIR)/packages/',
             '--snapshot=<(SHARED_INTERMEDIATE_DIR)/pub.dart.snapshot',
-            '../../sdk/lib/_internal/pub/bin/pub.dart',
+            '../../sdk/lib/_internal/pub_generated/bin/pub.dart',
           ]
         },
       ],
     },
     {
       'target_name': 'core_stubs',
       'type': 'none',
       'dependencies': [
         '../../runtime/dart-runtime.gyp:dart',
         '../../pkg/pkg.gyp:pkg_packages',
@@ skipping 25 matching lines @@
     # and creates a single pub_files.stamp
     {
       'target_name': 'pub_files_stamp',
       'type': 'none',
       'actions': [
         {
           'action_name': 'make_pub_files_stamp',
           'inputs': [
             '../../tools/create_timestamp_file.py',
             '<!@(["python", "../../tools/list_files.py", "\\.dart$",'
-                ' "../../sdk/lib/_internal/pub"])',
+                ' "../../sdk/lib/_internal/pub_generated"])',
           ],
           'outputs': [
             '<(SHARED_INTERMEDIATE_DIR)/pub_files.stamp',
           ],
           'action': [
             'python', '../../tools/create_timestamp_file.py',
             '<@(_outputs)',
           ],
         },
       ],
     }
 
 
   ],
 }