Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/lib/src/source/cached.dart

Index: sdk/lib/_internal/pub_generated/lib/src/source/cached.dart
diff --git a/sdk/lib/_internal/pub/lib/src/source/cached.dart b/sdk/lib/_internal/pub_generated/lib/src/source/cached.dart
similarity index 96%
copy from sdk/lib/_internal/pub/lib/src/source/cached.dart
copy to sdk/lib/_internal/pub_generated/lib/src/source/cached.dart
index 3775aa910728d1572f165d5600ab20769a58a8c7..95214712a45cd486dd7bd0e85e3d9aaaea6f135a 100644
--- a/sdk/lib/_internal/pub/lib/src/source/cached.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/source/cached.dart
@@ -32,7 +32,9 @@ abstract class CachedSource extends Source {
   Future<Pubspec> doDescribe(PackageId id) {
     return getDirectory(id).then((packageDir) {
       if (fileExists(path.join(packageDir, "pubspec.yaml"))) {
-        return new Pubspec.load(packageDir, systemCache.sources,
+        return new Pubspec.load(
+            packageDir,
+            systemCache.sources,
             expectedName: id.name);
       }