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

sdk/lib/_internal/pub_generated/test/get/git/check_out_revision_test.dart

+library pub_tests;
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+main() {
+  initConfig();
+  integration('checks out a package at a specific revision from Git', () {
+    ensureGit();
+    var repo =
+        d.git('foo.git', [d.libDir('foo', 'foo 1'), d.libPubspec('foo', '1.0.0')]);
+    repo.create();
+    var commit = repo.revParse('HEAD');
+    d.git(
+        'foo.git',
+        [d.libDir('foo', 'foo 2'), d.libPubspec('foo', '1.0.0')]).commit();
+    d.appDir({
+      "foo": {
+        "git": {
+          "url": "../foo.git",
+          "ref": commit
+        }
+      }
+    }).create();
+    pubGet();
+    d.dir(
+        packagesPath,
+        [d.dir('foo', [d.file('foo.dart', 'main() => "foo 1";')])]).validate();
+  });
+}