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

sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart

Index: sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart b/sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart
new file mode 100644
index 0000000000000000000000000000000000000000..2f81ba5729b5cf2641ab369f8c1d46de5ef19152
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/lib/src/validator/utf8_readme.dart
@@ -0,0 +1,24 @@
+library pub.validator.utf8_readme;
+import 'dart:async';
+import 'dart:convert';
+import '../entrypoint.dart';
+import '../io.dart';
+import '../utils.dart';
+import '../validator.dart';
+class Utf8ReadmeValidator extends Validator {
+  Utf8ReadmeValidator(Entrypoint entrypoint) : super(entrypoint);
+  Future validate() {
+    return syncFuture(() {
+      var readme = entrypoint.root.readmePath;
+      if (readme == null) return;
+      var bytes = readBinaryFile(readme);
+      try {
+        UTF8.decode(bytes);
+      } on FormatException catch (_) {
+        warnings.add(
+            "$readme contains invalid UTF-8.\n"
+                "This will cause it to be displayed incorrectly on " "pub.dartlang.org.");
+      }
+    });
+  }
+}