update async in the sdk, add flutter engine patch

Change-Id: I17e088df3024992c4ea19a6dc2bcd63ba0dbb11b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153620
Reviewed-by: William Hesse <whesse@google.com>
Auto-Submit: Jake Macdonald <jakemac@google.com>

.dart_tool/package_config.json

@@ -72,7 +72,7 @@
       "name": "async",
       "rootUri": "../third_party/pkg/async",
       "packageUri": "lib/",
-      "languageVersion": "2.2"
+      "languageVersion": "2.9"
     },
     {
       "name": "async_helper",
@@ -713,4 +713,4 @@
       "languageVersion": "2.4"
     }
   ]
-}
+}

DEPS

@@ -66,7 +66,7 @@ vars = {
 
   # Revisions of /third_party/* dependencies.
   "args_tag": "1.6.0",
-  "async_rev": "e0c41e0c1fb70ba606dc81335c981af7c00987c6",
+  "async_rev": "5a4373458bfc902e4a4064427c619c2b41783f0d",
   "bazel_worker_rev": "26680d5e249b249c7216ab2fed0ac8ed4ee285c5",
   "benchmark_harness_rev": "a9d5fe44b1cb5527101fb4597b38b3c8b7c04ea8",
   "boolean_selector_rev": "1309eabed510cc3b7536fd4367d39b97ebee3d69",

tools/patches/flutter-engine/fecc8163afc76f6accd461d59a7eb82fe4215d61.patch

@@ -0,0 +1,13 @@
+diff --git a/DEPS b/DEPS
+index a4ee1ba7e..862c7d8f7 100644
+--- a/DEPS
++++ b/DEPS
+@@ -170,7 +170,7 @@ deps = {
+    Var('dart_git') + '/args.git' + '@' + Var('dart_args_tag'),
+ 
+   'src/third_party/dart/third_party/pkg/async':
+-   Var('dart_git') + '/async.git@e0c41e0c1fb70ba606dc81335c981af7c00987c6',
++   Var('dart_git') + '/async.git@5a4373458bfc902e4a4064427c619c2b41783f0d',
+ 
+   'src/third_party/dart/third_party/pkg/bazel_worker':
+    Var('dart_git') + '/bazel_worker.git@26680d5e249b249c7216ab2fed0ac8ed4ee285c5',