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

sdk/lib/_internal/pub_generated/test/build/includes_dart_files_in_debug_mode_test.dart

+import 'package:scheduled_test/scheduled_test.dart';
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration("includes Dart files in debug mode", () {
+    d.dir(
+        appPath,
+        [
+            d.appPubspec(),
+            d.dir(
+                'web',
+                [
+                    d.file('file1.dart', 'var main = () => print("hello");'),
+                    d.file('file2.dart', 'void main(arg1, arg2, arg3) => print("hello");'),
+                    d.file('file3.dart', 'class Foo { void main() => print("hello"); }'),
+                    d.file('file4.dart', 'var foo;')])]).create();
+    schedulePub(
+        args: ["build", "--mode", "debug"],
+        output: new RegExp(r'Built \d+ files to "build".'));
+    d.dir(
+        appPath,
+        [
+            d.dir(
+                'build',
+                [
+                    d.dir(
+                        'web',
+                        [
+                            d.nothing('file1.dart.js'),
+                            d.matcherFile('file1.dart', isNot(isEmpty)),
+                            d.nothing('file2.dart.js'),
+                            d.matcherFile('file2.dart', isNot(isEmpty)),
+                            d.nothing('file3.dart.js'),
+                            d.matcherFile('file3.dart', isNot(isEmpty)),
+                            d.nothing('file4.dart.js'),
+                            d.matcherFile('file4.dart', isNot(isEmpty))])])]).validate();
+  });
+}