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

sdk/lib/_internal/pub_generated/test/serve/serves_file_with_space_test.dart

+library pub_tests;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+main() {
+  initConfig();
+  integration("serves a filename with a space", () {
+    d.dir(
+        appPath,
+        [
+            d.appPubspec(),
+            d.dir(
+                "web",
+                [
+                    d.file("foo bar.txt", "outer contents"),
+                    d.dir("sub dir", [d.file("inner.txt", "inner contents")])])]).create();
+    pubServe();
+    requestShouldSucceed("foo%20bar.txt", "outer contents");
+    requestShouldSucceed("sub%20dir/inner.txt", "inner contents");
+    endPubServe();
+  });
+}